u.s. Department of the Interior U.S. Geological Survey

Hydrology of the Helena Area Bedrock, West-Central Montana, 1993-98 By Joanna N .. Thamke

with a section on Geologic Setting and a Generalized Bedrock Geologic Map by MitcheJl W6 Reynolds

Water-Resources Investigations Report 00-4212

In cooperation with

Lewis and Clark County Water Quality Protection District

U.S. Department of the Interior

BRUCE BABBITT, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Any use of trade, product, or finn names iu this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government

Helena, Montana October 2000

For additional information write to:

District Chief U.S. Geological Survey 3162 Bozeman Avenue Helena, MT 59601-6456

Copies of this report may be purcbased from:

U.S. Geological Survey Branch of Information Services Box 25286 Denver, CO 80225-0286

CONTENTS Page

Abstrac! ........ .................... ........ .. ................................. ....... .................................. .................. ..... ............................. ... .... .. .... I InirodliClion .. .. ... ......................................... .. .............................. ........ ...... .... ....... ..... .... .. ............ ..... ......... ..... ..... ......... .... .. .... 2

Purpose and scope .... ..... ... .. .......................... .................. .... ...... .... ... ...... .... ...... ... ..... ..... ..... ..... ..... .. ... .. .... ............. ....... 2 Location and description of study area .... .... .... ... .. ..... ..... ... ... ... .... .... .... ........................................................... .. .. ....... 2 Previous investigations .. .. ...... ..... .... .. ... .... .. ........ ...... .... ... .. ... .. .. .... ... . ......... ..... .......................... .............. .. ....... ..... .. .... 4 Methods of investigation. ...................... .......... ............. .. .. ................... ............. ..... .................. ......................... .. ....... 6

Well invenlory and water-level monitoring ........ .............. ...................................... . .................... ....... ........... 6 Detemlination ofwatcr-leveltrends........... ......... .. .............. ........................................................... ..... .. .. ....... 7 Water-quality sampling, analysis, and quality control. ....... ........................................................... ...... ....... ... 7

Acknowledgments ...................................... ........ ........... .. .. .. .... .... ..... .......... ......................................... ................... ... 9 Geologic selling.......................................................................... .... ....................................................................... .... ...... .. .... 10

Bedrock units .... .................. ....................... ......... ..... ......... ... .. .. .. ........ ......... ........................................ ...... ......... .. .. .... 10 Geologic structuTC. ..... .................. ............... .... .......... .. .. .. . ... ....... ......................................... ................. .. ..... ........ ...... . 13 Application of the generalized bedrock geologic map .... ................ .. ......................................... .. ... ................... ....... 15

Hydrology.. ..... ...................................................................... ...... .. ...... ....................................................................... ....... ..... 15 North Hills ... ... ......... ............................ ............. ........ ... .... .. ... ........ .. ......... .. ..... .............................. ...... .......... ..... ........ 20 Scratchgravel Hills. .... ...... ............................ .. ................... ..... .... ... ....... .. .. .... .................................. ........ ...... .... .. .. .... .. 22 Western mourllai ns .......................................... .......... ....... ............................ .................. ............................ .. .... ......... 26 South Hills .... .......... ................... ......... .... .............. ......... ........... ......... ............. .... .. ... .. .... .. .. .... .... ...... ... ...................... . 28 Ground-water availability ........... .... ... .. ....... ......................... .... ........ ... ........ ... ........... ......... ......... ...... .. ......... .............. 29 Application of the hydrologic information ....................................... ... . .. .......... ... .................................. .. ......... .... ... .. 30

Sunlmary and conclusions .... .... .. ............ .......................................................................................... ..... ...................... ..... ..... 30 Selected references ....................................................... ... .. .... ...... ... ............. ..... .... ..... ..... ................... ...... ........... ...... .. ... ... ..... 33 Appendix ........ .. .......... ........... ................................. .. ............ ............. ............... ..................................................................... 37 Definitions .......... .. .......... ......... ......................... .. ... .. .. ........ .. . ........ .. .. ... ........ ... .. ... .. ... .......... ....................... .............. ..... ........ . 39 Location-numbering system... ..... ......... ......... ............... .. ...... ................ ....... ................................ .. ....... . .... ....................... .... . 42 Data ........ ............. .............................................................. ... ..... ........... ..... ..................................................... .. ..................... 43

ILLUSTRAnONS

Plate I. Generalized bedrock geologic map of the Helena area, west-central Montana ...................................... In pocket 2. Map showing location. water-level trends, and chemical composition of water for

selected wells in Helena area bedrock, west-central Montana ........ ..................... ..... .... .... ......... .... ..... In pocket 3. Hydrographs for wells in monthly water-level monitoring network. Helena area bedrock,

west-central Montana ........... ..................................... ........... .. .......... ....... ...... .. .... .......... ... .... ............... In pocket Figure 1. Map showing location of the study area ..... ......... .. ............. ..... ....... .... ...... .. .. .... ....................... ..................... 3

2. Map showing average annual precipitation. 1961-90 ... .... ......... ............ ................................... .. .................. 5 3. Map showing location of selected geologic fearures in western Montana.. .... .... .. .... .... ......................... .... ... 11 4. Graphs showing annual precipitation for selected sites , 1992-98.. ............ ......... ..... ....... ............................. 17 5. Graphs showing average monthly precipitation for selected sites, 1961-90................................................. 18 6. Graphs showing monthly precipitation for selected sites, January 1992 through May 1998 ........... ............ 19 7. Map showing apparent age and nitrate concentration in water from selected wells..................................... 21 8. Graph showing temporal changes of nitrate concentration in water from nine wells, 1994-98 ....... ............ 23 9 . Graph showing nitrogen-isotope ratio and nitrate concentration in water from selected wells ...................... 24

10. Long-term hydrographs for two wells completed in the Scratchgravel Hills bedrock and corresponding monthly precipitation ....................................... ...... .. .. .......... ............................................. 25

CONTENTS iii

TABLES

Table Page

I. Geologic time chart .................. .......................... ...... ......... ............................... ............................. ................ 38 2a. Geologic and inferred hydrologic characteristics of Helena area bedrock ................................................... 44 2b. Approximale range of values of permeability and hydraulic conductivity of Helena area bedrock............. 54 3. Records of wells... .............. ..... ......... ......... ......... ......... .................. ......... ............. ........................ .............. .. .. 55 4. Records of water levels in selected wells........... ......... ................. .......... .......... ........ ............... ...................... 70

5. Physical properties and major-ion and trace-element concentrations in unfilrered water samples collected from selected wells .................................................................................................................... 106

6. Chlorofluorocarbon (CFC) dara for water from selecred wells, 1992 and 1995 ........................................... liS 7. Chloride and nitrale concentrations and ratios of nitrogen isotopes and oxygen isotopes in water

from selected wells ........... ...... .............. ............. ......... .................. ........................ ......... ......... ................... I I 7 8. Volatile organic compounds, EPA Maximum Contaminant Levels, minimum reporting

level, and concentrations of volati Ie organic compounds in water samples collected from selected wells ............................................................................................................................................. I I ~

CONVERSION FACTORS, VERTICAL DATUM, ABBREVIATED WATER-QUALITY UNITS, AND ACRONYMS

MultipLy By To obtain

acre 4,047 square meter

darey 9.87 x 10.9 square centimeter (cm2) foot (11) 0.3048 meter (m)

0.0003048 kilometer (km) gallon (gal) 3.785 liter

gallon per minute (gal/min) 0.06309 liter per second

gallon per day per square foot (gaVdayjfi2) 4.72 x. 10.5 centimeter per second 0.134 foot per day

inch (in.) 25.4 millimeter (mm)

2.54 centi meter (em) mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.59 square kilometer (km")

Temperature can be converted from degrees Celsius (0C) to degrees Fahrenheit (OF) by the following equation:

OF = 9/5 (nC) + 32

Sea level: In this rep.ort, "sea level" refers to the National Geodetic Venical Datum of 1929 (NGVD of I 929)--a geodctic datum dcrived from a general adjustment of the first-order level nets of both the United States and Canada. formerly called Sea Level Datum of 1929.

Abbreviated water-guality units used in this repon:

gal/min

)lS/cm mgiL %0

gallons per minute microsiemens per centimeter ar 25 degree~ Celsius milligrams per liter permil (or parts per thousand)

Acronyms used in this repon:

CFC EPA MeL SMCL

USGS VOC WQPD

chloro Iluorocarbon United States Environmental Protection Agency Maximum Contaminant Level Secondary Maximum Contaminant Level United States Geological Survey volatile organic compound Lewis and Clark County Water Quality Protection District

iv Hydrology of the Helena Area Bedrock. West-Central Montana, 1993-98

Hydrology of the Helena Area Bedrock, West-Central Montana, 1993-98 By Joanna N. Thamke

with a section on Geologic Setting and a Generalized Bedrock Geologic Map by Mitchell W. Reynolds

Abstract

Helena area bedrock within the mountains and hills that surround the Helena Valley encompasses abour 585 square miles in west-central Montana. Water from Helena area bedrock is used by an increas­ing number of residents as the primary source of domestic water supply and also provides a large part of the annual recharge to the Helena valley-fill aquifer system. As the growing population increases demands on the water supplies within the Helena area bedrock, public concern bas been expressed regarding potential depletion or contamination oflhis water resource. In 1993, the U.S. Geological Survey, in cooperation with the Lewis and Clark County Water Quality Protection District, began a study to assess the hydrology of the Helena area bedrock and to provide infonnation that can be used to evaluate future changes in the hydro­logic system.

Bedrock units that contain ground warer of con­cern in this report generally are exposed on the margins of the Helena Valley. Bedrock units of the Helena area range from Middle Proterozoic to Tertiary in age and include sedimentary rock sequences, igneous intrusive rock units, and volcanic rock sequences.

The principal controlling faults in the Helena area are the Helena Valley fault zone along the north and northeast margin of the area and the Bald Butte fault zone that crosses the central part of the area. Together, the Helena Valley fault zone and the Bald Butte fault zone are components ofa major continental fracture known as the Lewis and Clark fault zone. All faults in the Helena area affect the hydrologic charac­teristics of rocks displaced by the faults.

Recharge to Helena area bedrock primarily occurs by direct infiltration of precipitation, although recharge by infiltration of streamflow, infiltration from saturated overlying unconsolidated deposits, leakage from irrigation canals, and infiltration of applied irriga­tion water can be significant locally. Recbarge by infil­trarion of precipitation occurs when infiltration is greater than the sum of evapotranspiration and soil­moisture deficit. These conditions generally are satis­fied only during the wetter parts of some years, result­ing in small amounts of recharge. if any, during most years. Amounts of recharge vary with location and ch­matic factors. Average annual ground-water discharge from bedrock to the valley-fill aquifer has been esti­mated to be about 40,000 acre-feet per year. Ground water in the bedrock is contained in joints, fractures, and other fomls of secondary porosity, resulting in het­erogenous hydrologic characteristics and highly vari­able well yields and water levels over short distances.

Availability of water in Helena area bedrock dif­fers areally across short distances as a result of precip­itation, evapotranspiration, and the heterogeneous character of the rock types and joint, fracture, and fault systems in the many different geologic units. The depths of 198 inventoried wells ranged from 14 to 750 feet, with a median of 160 feet. Well yields reported in 159 drillers' logs ranged from 1 to 100 gallons per minute, with a median of 15 gallons per minute. Water levels in wells fluctuate in response to natural and human-induced recharge and discbarge. Water-level trends during January 1992 through May 1998 indi­cated both increases and decreases . The long-term trend for November 1976 through May 1998 for one well was decreasing, even though (he trend for the well during January 1992 through May 1998 was increas·

Abstract

ing. In any area of the bedrock, if natural and human­induced discharge exceeds recharge for a significant period of time, water-level declines would be expected. Conversely, ifrecharge exceeds discharge, water-level rises would be expected.

Ground-water quality in Helena area bedrock is suitable for most uses and is affected by geology and locally by human activity. Bedrock strongly influences the composition and concentration of major ions in the water. Water samples from 6 0[70 sampled wells had nitrate concentrations tbar equaled or exceeded 10 mil­ligrams per liter (the maximum contaminant level established by the U.S. Environmental Protection Agency for public drinking-water supplies) . Concen­trations of trace elements in water generally were low. Concentrations of volatile organic compounds in all of to waler samples analyzed were less than minimum reponing levels.

INTRODUCTION

The City of Helena and surrounding areas have experienced a marked growth in population during recent years. Much of this growth has been concen­lrated in the Helena Valley, where residents rely on the Helena valley-fill aquifer system for water supply . Development has also occurred in the surrounding mountains and hills, where residents rely on water in the bedrock for water supply . In addition to supplying water [0 residents in the surrounding mountains, water from Helena area bedrock provides a large part of the annual recharge to the Helena valley-fill aquifer system (Briar and Madison, 1992). Public concern has been expressed that increased development and lise of the limited water supplies within the Helena area bedrock may lead to depletion or contamination of this water resource.

[n 1993, the U.S. Geological Survey (USGS), in cooperation with the Lewis and Clark County Water Quality Protection District (WQPD), began a study of water in Helena area bedrock. The study was designed to provide an initial assessment oftne hydrology of the bedrock and to provide infonnation that can be used in the future to evaluate changes in the hydrologic system. Much of the hydrologic information was interpreted in the context of the geologic setting and a generalized bedrock geologic map developed by the USGS compo­nent of the National Cooperative Geologic Mapping Program.

2 Hydrology of .h~ HelclHI Area Bedrock, West-Central Montllna, 1993-98

Purpose and Scope

This report describes the geologic setting and hydrology of Helena area bedrock. The geologic sel­

ting consists of a description of the bedrock units and

their hydrogeologic characreristics, a description of the geologic structure of the area, and a bedrock geologic

map of the area. To aid in the description oflhe hydrol­ogy, the study area has been divided into four smaller

areas or parts. Precipitation, recharge, age of water, discharge, water-level changes and trends, and water

quality are described for each area. Hydrologic data

for the study were obtained through the inventory of

201 wells, momhly measurements ofwarer levels in 112 wells, and colleclion ofwater samples for analysis

of major-ion and trace-element concentrations from 70

wells. In addition, water from 20 oC tile inventoried

wells was analyzed for chloroflurocarbons (CFe's),

water from 9 of the inventoried wells was analyzed for

stable-isotope ratios of nitrogen and oxygen in nitrate

and for temporal variations in nitrate concentration,

and water from 10 of the 70 wells sampled for major­

ion and trace-element concentrations also was ana­

lyzed for volatile organic compounds (VOCs).

Location and Description of Study Area

The study area encompasses about 585 mi 2, pri­marily in Lewis and Clark County, in west-cenlTal

Montana (fig. I) . Allitudes across tne area range from

about 8,150 ft at Red Mountain in the southwestern

pan of the study area to 3.590 ft alIne Missouri River

near Beaver Creek in the northeastern part of the study

area. Bedrock underlies and is exposed at the surface

surrounding the Helena valley-fill aquifer (pI. I). The

study area does not include areas wnere wells withdraw water only from [he Helena valley-fill aquifer system

or the Spokane Bench on the east side of that system.

Four principal streams enrer the Helena Valley from

bedrock areas: Prickly Pear. Tenmile, Sevenmile, and Silver Creeks (fig. 1).

The area can be divided into four major geo­

graphic parts: the North Hills, the Scratchgravel Hills

(on the west side of the valley), the western moumains,

and the South Hills, where the City of Helena is located

R W ,6 . RAW. 1120 A.3W, R.2W.

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Figure 1. location of the study area.

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G ..... - ..... \ 0 Montana City ..... -~e'8 -.....

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MONTANA

./ Siudy area

FIGURE 1 3

(fig . 1) . The North H ills rise from the northern margin of the Helena Valley as a sloping plain that breaks into rolling hills alo.ng an east-trending crest. The crest of the North Hills is about 12 miles north of Helena and extends from Hauser Lake and the Missouri River on the east to Silver City on the west. The Scratchgravel Hills, tlanked by the Scratchgravel Hills fault on the eaSl and the Silver Creek fault on the west, rise prominently northwest of Helena . The western mountains include all the mountainous terrain west or the Scratchgravel and South Hills from about Silver Creek on the north to the headwaters of Tenmile Creek on the south . The South Hills include most of the City of Helena and hills farther south that extend from Little Butte on the east to Colorado Gulch and the drainage divide between Lump Gulch and Tenmile Creek on the west (fig. I).

Average annual precipitation in the Helena area ranges from abOllt lain. in the Helena Valley to more than 30 in . in the headwaters of Tenmile Creek south­west of Helena, as shown on figure 2. The information shown on figure 2 was originally compiled and ana­lyzed by Phillip E. Fames (Snowcap Hydrology, Boze­man, Mont ., written commun., 1999) from Snow Survey Telemetry System Data, storage and precipita­tion gage data, and National Weather Service climato­logical data. Lines of equal average annual precipi­tation on figure 2 are derived from regional maps that cover about 13,500 mi2, surroundi ng and including the area of this report . Values shown are for a standard 30-year base period of record (! 961-1990).

About 49,000 people resided in the Helena Val­ley and the surrounding study area in 1998, including about 28,300 in the City of Helena and 1,750 in the City of East Helena (David R. Martin, Census and Eco­nomic Information Center, Montana Department of Commerce, oral commun., 2000). During 1970-99, the population of Lewis and Clark County has grown by more than 60 percent (from 33,281 to 54,075). Popu­lation growth from 1990 to 1999 was about 6,580 peo­ple (David R. Martin , oral commun., 2000) . A sig­nificant part of the popUlation growth has been in the mountains that surround the Helena Valley.

Land uses in the study area include irrigated hay and pasture farming, livestock grazing, residential development. mining, and quarrying. lrrigated hay and pasture farming is mostly in (he bottoms of principal stream valleys and where the bedrock is overlain by valley fill. Livestock grazing is mostly on large

" Hrdrology of the Helenn Arca Bedrock, We$I-Cenlrlll Montanll, 199)·98

ranches and land managed by the U.S. Forest Service. Residential development in the study area is concen­trated in the cilies ofHeJena and East Helena and is dis­tributed irregularly among ranches, ranchettes, sub­divisions, and mobile-home parks outside the urban areas. Mining for gold, silver, lead, copper, and zinc has occurred in the mountains since 1864, and many inactive or abandoned mine sites remain . Limestone is quarried in the South Hills south and southeast of Hel­ena.

Previous Investigations

Numerous geologic investigations of the Helena area have been conducted; only the principal works that provide fundamental geologic map information are described here. Interpretive reports are cited within the text. Knopf (1913, 1963) established the geologic framework for the western part of the Helena area . Nomenclature for the upper part of the Belt Super­group, odginally proposed by Knopfas the Marsh For­mation, was clarified and revised by Harrison ( 1972) to be consistent with use across the Belt basin of western Montana and eastern Idaho. Knopfs (1963) geologic map subsequently served as the base for part of the geo­logic map of the Elliston region by Schmidt (Schmidt and others, 1994). Schmidt's geologic mapping and compilation were the source of data for the northeast segment of the I :250,000-scale generalized geologic map of the BUlle I" x 2" quadrangle (Wallace, 1987) that includes the western part of the study area . Geol­ogy of the southwestern and southern parts of the Hel­ena area was studied by the USGS as part of the Boulder batholith and related mineral resources projects. Geologic maps and descriptions of rock units from three of those studies were used for this report : Becraft and others ( 1963). Ruppel (1963), and Smedes (1966). Klepper, Robinson , and Smedes (1971) described the Elkhorn Mountains Volcanics in detail , and Greenwood and others (1990) provided new inter­pretalions oCthe succession and origin of the Elkhorn Mountains Volcanics along the south margin of the Helena area.

Several previous studies contributed to an under­standing of the geology of the hills of the northern and eastern Helena area. Mertie and others (1951) studied the Canyon Ferry Lake area east of Helena. Robinson and others (1969), Bregman ( I 981 ), and unpublished mapping by M.W. Reynolds and W.H. I-lays (U.S. Geological Survey, written commun .. 1997), together

R5W.

I (2..25 miles soulh of • slud~ .rea boundAry)

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EXPLANATION

UNE OF EQUAL AVERAGE ANNUAL PRECIPITATlON··Period 01 record. 1961-90. Conlour inlarval 2 and 10 Inches (Phillip E, Fames, Snowcap Hydrology; written commun" 1999)

LINE OF APPROXIMATE SURFACE EXTENT OF HELENA VALLEY·FILL AQUIFER SYSTEM (Briar and Madison. 1992)

Helena WSO

LINE OF APPROXIMATE BOUNDARY DELINEATING NORTH HILLS, SCRATCHGRAVEL HILLS, WESTERN MOUNTAINS, AND SOUTH HILLS

~ PRECIPITATION STATION AND NAME,· Dala for Helena WSO, Auslm 1W. and Frohner Meadows. and Rocker Peak shown in figure 4.

Figure 2, Average annual precipitation, 1961-90, Data from Phillip E. Farnes, Snowcap Hydrology, Bozeman, Montana (written commun., 1999).

FIGURE 2 :;

with unpublished mapping by G.D. Robinson (U.S . Geological Survey, WTitlen commun., 1971) in the Silver City area, serve as a basis for knowledge of the geology in the northwestern part of the region. Lorenz and Swenson (1951) summarized the geology and ground water of the Helena Valley, including parts of the area described in the current report. Within Helena Valley. geologic mapping by Schmidt [1986, and written commun. (see pI. I. index map)] provided detailed infonnation about tbe bedrock and faults . A subsequent map of the same area by Stickney (1987) focused on some details of Quaternary deposits.

Several investigators previously described the Helena valley-fill aquifer system. Lorenz and Swen­son () 951) first described the water resources of the Helena Valley. Ground-water quality in the valley was described by Wilke and Coffin (L 973). Depth to the water table and area inundated by the June 1975 flood were investigated by Wilke and Johnson (1978). Moreland and Leonard (1980) evaluated the shallow aquifers beneath the valley. The hydrogeology of the valley-fi II aqui fer system was described by Briar and Madison (l992). Drake (1991, 1995) evaluated trends in selected chemjcal constituents in water from the valley-fill aquifer system. The geography, geology, and hydrology of the Helena Valley were summarized by Kendy and Tresch (1996).

Previous ground-water investigations of the Hel­ena area bedrock have been limited to small parts oflhe study area . Hydrologic characteristics. for a specific part of the North Hills were detennined by Scientific A pplicatiol1s I ntemational Corporation (1989) and Kaczmarek (1995). The hydrology oftne Scratch­gravel Hills was described by Lewis and Clark Area­wide Planning Organization and the Green Meadow Study Committee (1977), Wetzel and Hanneman (1983). and Wetzel (J 993). James M. Montgomery, Consulting Engineers, Inc. (1977) described the hydrology oflhe Veteran's Administration Center at FOr1l-Ianison. and PRC Environmental Management, Inc. (l995) described the hydrology of Fort Harrison, both south of the Scratchgravel Hills. Stiller and Asso­ciates (1983) and Hydrometrics, Inc. (1991) summa­rized water quality and hydrology of the southeastern part of the Scratchgravel Hills. The complex hydrol­ogy in a small area west of Helena was described by Baumann and Clark ( 1991 ).

(, Hydrology of (he Helena Arcn Bedrock., West-Central Montana. 1993-98

Methods of Investigation

Well Inventory and Water-Level Monitoring

Drillers' logs of water wells completed in the study area were obtained from the Montana Bureau or Mines and Geology and were used to guide selection of privately owned and commercial water wells for inven­tory by USGS and WQPD personnel. The drillers' logs typically provide information about well completion (well depth, casing diameter, casing material, top and boltom of casing, and conslTUction date), water level, and well test data (yield, pumping period, pumping water level, and measurement date). There are no uni­form criteria for drillers to measure this information and methods are not reported on drillers' logs; the methods used and the accuracy of these values might vary.

The well inventory included detennination of well location, land-surface altitude, aqui fer unit, and, where possible, measurements of water level, yield, and pumping water level (table 3). Well location and land-surface altitude generally were determined ITom 7.S-minute topographic quadrangle maps, although some well locations were detennined using a global positioning system. Aquifer units were detennined from drillers' logs and geologic maps. Drillers' logs for two of the wells inventoried indicated completion in bedrock; subsequent sttldy of geologic maps indi­cated probable completion in Quaternary alluvium. so these two wells were not included in this study. Cer­tain measurements on drillers' logs (well depth, casing diameter, casing material, and lOp of casing) were ver­ified, where possible, during the well inventory.

Basic water-quality measurements were made onsite, where possible, during the well inventory (table 3). Water temperature, specific conductance, pH, and nitrate concentralion were measured at the water­sample collection point for tbe well. Onsite nitrate concentrations were detetmined semi-quantitatively using a spectrophotometer having a detection limit of 0.5 mg/L. These basic water-quality data subsequently were evaluated to help select a subset of wells from which to collect samples for laboratory chemical analysis.

Of the 20 I water wells inventoried for this study (which is much less than the existing number of wells in the area), 112 were selected for a monthly water­level monitoring nerwork to represent the various Hel-

ena area bedrock units. Selection was based on acces­sibility and pennission of the well owner. Water levels were measured by USGS and WQPD personnel, usu­ally during the last 2 weeks of each month. A gradu­ated steel tape, electric tape, or pressure gage was used ro measure the water level. (Tapes were cleaned with a bleach solution between well sires.) Significant effort was made to collect water levels at times when water was not being pumped; however, sometimes this was not possible. Well activity was noted on field forms as "pumped" or "recently pumped" if there were audible or visual indications of water use or if the well owner indicated recent use at the time of measurement. The water-level monitoring network was initiated in Octo­ber 1993: however, many wells, particularly in the Scratchgravel Hills area, were measured prior to this date as part of other data-collection efforts. Final measurements at most wells were made ill March or April 1997. although 25 wells were measured beyond April 1997. Some wells were eliminated from the monitoring network prior to spring 1997 if measure­ment obstacles developed, if well access changed, or if the well was destroyed. At least 20 different measure­ment periods of water-level records are represented for wel1s--several with I year of data, many with 3 to 6 years of data, and 2 with more than 20 years of data. The period of record common to most wells is October 1993 through April 1997. All available water-level measurements through May 1998 are included in table 4: hydrographs of water levels for all wells in the mon­itoring network are shown on plate 3.

Determination of Water-Level Trends

Simple linear regression relations betweeo waler level and time were used to test for trends io water level during the general period of Ihis study. Regression relations were developed for those wells ha ving at least J successive years of near-monthly water-level mea­surements. Available data for the period January 1992 through May 1998 were used to detennine trends. In addition, the long-teml water-level trend for one weU in the Scratchgravel Hills also was examined. The long-tenn period of record was November 1976 through May 1998.

A simple linear regression relation between water level and time indicates a trend io water level if the slope of (he regression line is significantly different from zero. Whether a computed regression line slope

can be considered to be significantly different from zero depends upon the attained level of significance, or p-value, of the computed regression slope . P-values provide ao indication of how likely the true slope is really zero (no trend). Thus. small p-values represent regression line slopes that have only a small chance of truly being zero and, therefore, can be considered 10 be significantly different from zero.

Hydwgraphs and regression lines relating water level to time are shown graphically on plate 3. P-values for each regression line also are shown and can be used to infer whether the regression lines indicate trends in water-level data. For this study, all regression lines are presented, but only those regression lines having a p-value of 0.05 or less (95-percem confidence level or greater) were considered to indicate significant trends .

Water-Quality Sampling, Analysis, and Quality Control

Water samples were collected from 70 wells dur­ing 1994 to 1998 for laboratory analysis of major ions and trace elements. Water samples were collected from nine wells at four different time periods for analysis of nitrate plus nitrile (as nitrogen). Because the concen­tration of nitrite generally is below the laboratory min­imum reporting levels or small compared to nitrate in the study area, concentrations of nitrate plus nitrite are referred to as nitrate in this report for simplicity. Water samples from 10 of the 70 wells also were analyzed for volatile organic compounds (YOCs). VOCs include solvents, dry cleaning agents, and similar compounds that are primarily synthetic and, if present in water, indicate a human-induced effect on water quality.

Wells selected for water-quality sampling were spatially distributed throughout the study area. Trace elements were analyzed in water from wells located near historical mining activity; VOCs were analyzed in water from wells near roadways, railroad beds, and dry­cleaning operations. Water samples for analysis of major ions, nitrate, trace elemeots, and VOCs were col­lected by WQPD personnel from wells using the exist­ing well pump. The sample collec(ion point was the spigot nearest the well to reduce the amount of plumb­ing pipe and fixtures in contact with The water. Com­monly this was a frost-free spigot within several feel of the well. For some wells, a spigot on the exterior oflhe house was the collection poinl. All samples for labora­tory chemical analysis were unfiltered and collected either directly from the spigot or from a garden hose

INTRODUCTION 7

attached to the spigot if the spigot could not be easily accessed. Samples to be analyzed for trace elements, nitrate. and VOCs were immediately preserved with Ilitric acid, sulfuric acid. and hydrochloric acid, respec­tively . Water samples were chilled and stored in cool­ers that were sealed prior to shipment to the laboratory with chain-of-custody fonns. Chain-of-custody lonns were signed by laboratory personnel to con finn receipt of the samples.

Chemical analyses were perfonned by Inter­mountain laboratories, Bozeman, Mon!., for samples collected during 1994 and Energy Laboratories, Billings. Mont., for samples collected during 1996 to 1998. Both laboratories used methods described by the U.S. Environmental Protection Agency (EPA) (1979, 1986, 1993, 1994). Analytical results for major ions, nitrate, and trace elements are presented in table 5. Analyses of VOCs were perfomled by Energy labora­tories, Billings, Monl., using methods described by the EPA (1988) . Analytical results for VOCs are presented in table 8.

Water-quality data were compared to primary and secondary drinking-water regulations and bealth advisories of the EPA (1996). National primary drink­ing-water regulations are established for chemical con­s1ituents wbich, ifpresent in drinking water, can cause adverse human health effects. Either a maximum con­taminant level (MCl) or a treatment technique is spec­ified by these regulations for regulated constituents. MCls are health-based and enforceable for public drinking-water supplies . National secondary drinking­water regulations are established for constituents or properties that can adversely affect the odor or appear­ance of water. These regulations specify secondary maximum contaminant levels (SMCLs) that are esthet­ically based and nonenforceable.

lntemal quality-control data for analytical proce­dures were provided by the laboratory through matrix spiked samples, blank spiked samples, and reagent blanks. A matrix spiked sample is an aliquot of a well­water sample to which a predetennined amount of analyte has been added . This type of sample is used to evaluate whether any of the constituents present in the sample caused analytical interference. A matrix spiked sample was analyzed for trace elements during 1994 by Intermountain Laboratories; a matrix spiked sample was analyzed for VOCs during 1996 by Energy labo­ratories. Percent recovery for the constituents analyzed in the matrix spiked samples ranged from 89 to 112, which is within tbe acceptable confidence interval of

8 H~·drol()g.v or the Aelenll Area Bedrock. WC"~I-Cl'nlral Montana. t 993-98

80-120 percent. A blank. spiked sample is an aliquot of deionized water to which a predetemlined amount of anaJyte has been added. This type of sample is free of matrix interference and is used \0 confinn that the ana­lytical methods accurately recover the known amount of added analyre. Energy laboratories extracted and analyzed two blank spiked samples for VOCs; percent recovery was between 90 and I 13 for all compounds analyzed and was, therefore. within the acceptable con­fidence interval.

A reagent blank is an aliquot of deionized water which is passed through the laboratory equipment and analyzed to identi fy any detectable concentrations that might indicate contamination from the laboratory equipment. Energy laboratories analyzed five reagent blanks for VOCs; all VOC analysis results were below the minimum reporting level.

Quality-control data were obtained for environ­mental samples by submitting replicate samples for analysis (five for major-ion and lrace-element analysis, three for VOC analysis). Data from analysis of rep li­cate samples for major ions and trace elements are included in table 5.

Chlorofluorocarbons. Chlorofluorocarbon (eFC) concentrations were detennined in water samples from 20 wells to determine the age of ground water, which can provide infonnation on time of recharge and, there­fore, the susceptibility of the quality of the water to human-induced changes. Water samples for analysis of CFC concentrations were collected by USGS per­sonnel from wells using the e.."isting pump. The collec­tion point was the same as used by WQPD personnello collect water samples. All wells were purged until 2-3 well volumes of water were removed and field param­eters (temperature, specific conductance. and pH) had stabilized. Unfiltered samples for CFC analysis were collected using a specially designed apparatus described by Busenberg and Plummer (1992). The age of ground water, as estimated by the CFC method, is the time since the water became isolated from the unsaturated zone atmosphere (and recharged the ground water) to when the sample was collected.

The CFC dating technique requires an estimate of the recharge temperature of the water. The recharge temperature is the temperature of the water in equilib­rium with the atmosphere at the time of recharge. Recharge temperatures were detennined using the mean annual air temperature (National Oceanic and Atmospberic Administration, issued monthly) and the

estimated recharge altitude. Mean annual air tempera­ture for weather stations in and near the study area ranges from 5.5 DC at Austin (altitude 4.790 ft) to 7.7 °c at Canyon Ferry Dam (altitude 3,672 ft). Appar­ent ages calculated using these temperatures differed by about I year. An estimated recharge temperature of 5.5 °c was used for all CFC' calculations. Concentra­tions of CFCs were analyzed by the USGS, Reston, Va., laboratory using methods described by Busenberg and Plummer (1992). Analytical results for CFCs are presented in table 6.

Nitrogen and Oxygen Isotope Ratios of Nitrate. Sta­ble-isotope ratios for nitrogen and oxygen were deter­mined in water samples from nine wells. Water samples for stable-isotope analysis were collected by USGS personnel from wells using the existing pump. The collection point was the same as used by WQPD personnel to collect water samples. All wells were purged lIntil 3 well volumes of water were removed and field parameters had stabilized.

The ratios of stable isotopes of nitrogen ( 15N/ 14N) and oxygen (180 / 160) in nitrate can be used in many circumstances to detennine the primary sources of nitrate in ground water (for example, Kreitler, 1975; Gonnly and Spalding, 1979; Flipse and Bonner, 1985; Bottcher and others, 1990; and Wassenaar, 1995. among many others). Nitrogen-iso­tope ratios in nitrate from animal and human wastes Iypically are between +9 and +22%0 (Kreitler, 1975; Gonnly ana Spalding, 1979; Lindau and Spalding, 1984; Heaton, 1986). Nitrogen-isotope ratios in nitrate derived from mineralization or oxidation of organic nitrogen in soil typically are between +4 and +9%0 (Boyce and others, 1976; Gonnly and Spalding, 1979; Wolterink and others, 1979; Heaton, 1986). Nitrogen­isotope ratios in nitrate from fertilizers are generally between 0 and +60/00 (Spalding and others, 1982). Atmospheric deposition (which includes precipitation) is a small source of nitrate to ground water; nitrogen­isotope ratios in precipitation range from about -7 to +2.5%0 (Hubner, 1986; LeTolle. 1980; Heaton, 1986). Interpretation of nitrate s.ources requires caution because the isotope ratios of different sources may overlap; the original ratios can be altered by isotope fractionation, mainly during denitrification and ammo­nia volatilization; the original ratios can be altered by mixing of waters; and the nitrogen-isotope ratio in many circumstances can be interpreted to represent one nitrate source or a mixture of nitrate from multiple sources.

Denitrification can affect nitrogen-isotope ratios, particularly in deep wells (greater than 100 ft) com­pleted in fractured bedrock, as the sampled wells are. Occurrence of denitrification can be detected by analy­sis of the oxygen- and nitrogen-isotope ratios (Amberger and Schmidt, 1987; Bottcher and others, 1990; Voerketius and Schmidt, 1990). I f no denitrifi­cation has occurred, oxygen-isotope ratios typically are 3%0 (Nimick and Thamke, 1998). If denitrification has occurred, oxygen-isotope ratios typically would increase about twice as much as nitTogcn-isotope ratios (Amberger and Schmidt. J 987: Bottcher and orbers, 1990; Voerkelius and Schmidt, 1990).

Stable-isotope ratios of oxygen and nitrogen in nitrate in water were determined by the USGS, Menlo Park, Calif., laboratory from nitrate concentrated on anion exchange resin columns within 24 hours of sam­ple collection (Kendall and Grim, 1990; Kendall and others, 1996). Analytical results for nilrogen and oxy­gen isotopes, plus associated chloride and nitrate con­centrations, are presented in table 7.

Acknowledg ments

The Lewis and Clark County Water Quality Pro­tection District and its Board members are acknowl­edged for their C()rnmitment to understanding ground­water resources in the Helena area. The many individ­ual well owoers are acknowledged for allowing access to their wells and for valuable discussions about Ihe occurrence and use of water resources in Helena area bedrock. James E. Elliott. retired USGS employee and well owner in the study area, provided many years of valuable water-level data for his and neighboring wells . Phillip E. Fames not only graciously supplied precipi­tation information but also discussed the merits and application of different precipitation models. In addi­tion, several WQPD and USGS employees are acknowledged for inventorying the wells io the study area and measuring monthly water levels even in the most inclement weather: Patricia S. Hettinger and Kathy L. Moore (WQPD), and Fred A. Bailey (USGS), who also provided valuable field obselVations. Mike Richter, a summer volunlee-r for the USGS. assisted with well inventory and chlorofluorocarbon sample collection. Deeda Richards, Montana Department of Natural Resources and Conservation, helped in coordi­nating programmatic activities.

INTRODUCTION 9

GEOLOGIC SETIING

Western Montana is characterized by a topogra­phy of elongate and curved valleys separated by moun­tain ranges that rise abruptly from the valleys. The front of the Rocky Mountains extends generally south across Montana from the U.S. border at Glacier National Park, curves eastward north of Helena, and extends southeast and south along mountain ranges east of the Smith River, Shields River, and upper pan of the Yellowstone Riverto Yellowstone National Park (fig. 3). The Helena area lies near the northeastern margin of that east-directed curve in the general moun­tain front. The Helena Valley with its surrounding mountains and hills was fonned primarily by basin­forming tectonic movements--earth movements that have generally dropped the valley with respect to adja­cent mountains. As a result, bedrock units that can function as sources for ground water are generally exposed on the valley margins, including low, fault­fonned benches adjacent to. and topographically nearly contiguous with, the sediment-filled valley; the bed­rock units are widely exposed in the m.ountains. In contrast, the Helena valley-fill aquifer consists of unconsolidated or poorly consolidated sediments (Briar and Madison, 1992) eroded from bedrock units of the adjacent uplands . The contrast between aquifer types is marked. This section of the report focuses first on the bedrock and then on the principal geologic struc­tures that have displaced the bedrock as well as, in some places. the young valley-fill sediments . Finally, this section provides some guidance for application of the generalized bedrock geologic map of the Helena area (pI. I) .

Bedrock Uni1s

The sequence and general characteristics of bed­rock units as grouped in this report are summarized in table 2 in descending stratigraphic position and increas­ing geologic age. This table also summarizes infer­ences, made on the basis of examination of the rocks in the field and under the microscope , regarding hydro­logic characteristics and responses ofthe bedrock units . Different sequences oflhe bedrock units are present in three broad parts of the Helena area: (I) tJ1e north and northeast. bounded on the west by the Canyon Creek and Scratchgravel Hills faults, and described as the North Hills; (2) west and southwest of the Canyon Creek and Scratcbgravel Hills faults. designated as the

10 Hydrology ofthe H~lcna Arell Bedrock, West-Centnl Montana. 199;1-98

western mountains and Scratchgravcl Hills; and (3) soutb and 30uthwesl of the Helena Valley as far west as Colorado Gulch. described as the Sourh Hills (pI. I and 2). Igneous intrusive rocks of the Boulder batholith and related stocks are exclusively localed in the west and southwesl parts of the Helena area (fig. 3).

The oldest rock sequences, belonging to the Belt Supergroup of Middle Proterozoic age (table I), are widely exposed in the nonh, n0!1heast, and west pans of the Helena area (pI. I) . The oldest units, the Greyson and Spokane Formations, crop out east and north of the Canyon Creek and Silver Creek faults and the Bald Butte fault zone (pI. I). These units likely lie beneath the young sediments throughout Helena Valley at depths not yet penetrated by drilling in the central part of the valley. In the eastern pan of the North Hills area, these oldest exposed Belt Supergroup rocks are faulted along the Eldorado thrust fault over strongly folded and locally faulted Paleozoic and Mesozoic rocks . In COI1-trasr, younger Belt Supergroup rocks including the Empire and Heleoa FOnllations and the Missoula Group (Snowslip Formation through the Bonner Quartzite) are exposed ml:linly west and south of the Canyon Creek and Silver Creek faults and the Bald Butte fault zone . Both the older and younger Belt sequences share several characteristics. Both sequences are mainly compact argillite and siltite; thin intervals in each sequence are coarse-grained siliciclas­tic sedimentary rock. such as sandstone or conglomer­ate, or carbonate rock, or both. Both sequences are metamorphosed regionally to low grade (locally to higher grades around igneous plutons in the western area). The micaceous mineral chlorite characterizes the metamorphism in tbe rocks. and rock fabrics are generally more compact than in younger sedimentary rocks. TIl rough much of both sequences, fractures are likely the roost important avenues [or water movement and storage.

In its lower part, the younger sequence of Belt Supergroup contains a thick succession of silty carbo­nate and carbonate rock (limestone and some dolo­stone), widely exposed west and northwest of Helena (pI. I) . These carbonate rocks, called the Helena For­mation, are unique in the Belt Supergroup of the region because they are subject not only to fracturing but also to dissolution of carbonate minerals. Overlying rocks of the Missoula Group (Shepard, Snowslip. and Mount Shields Fonnations and Bonner Quartzite) are mainly siltite and argillite, with units ofquanz-cemented sand-

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EXPLANATION

BOULDER BATHOLITH MONTANA DISTURBED BELT- · Approx imate eastem limit

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ELKHORN MOUNTAINS VOLCANICS _ • ..----.. .... FAULTED BELT SUPERGROUP

ROCKS-Approximate eastern timil FAUlTS--Dashed where

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Figure 3. Location of selected geologic features in western Montana,

FIGURE 3 II

stone and some conglomerate. A few thin beds of carbonate rock are present in the lower part of the Shepard Formation. Of special note is the truncation of (onnatioos in this Group from the highest (and youngest) Bonner Quartzite in the northwest, downward southeast through the Snowslip Fo.rmation in the Dry Gulch area of Helena. Southeast of Dry Gulch, all fomlations of the Missoula Group are absent. Uplift and erosion that produced the truncation occurred before the much younger Middle Cambrian Flathead Sandstone accumulated.

The distribution of sedimentary rocks of Cam­brian through Cretaceous age is delineated by major faults. The Bald Butte fault zone bounds the distribu­tion in the west and southwest part of the Helena area. In the northeast, those strata are exposed in a limited area west of the Missouri River on the north flank of the North Hills and more widely northeast of the river. The Eldorado thrust fault, with Greyson and Spokane Formations on the upper plate, overrides, and hence conceals, Cambrian through Cretaceous strata continu­ously south across the North Hills into Helena Vallcy.

The geology of Cambrian through Cretaceous sedimentary rocks differs in the northeast from that in the west and southwest in three si.gnificant ways. (I) In the northeast, the strata arc folded and faulted. but retain their basic lithologic characteristics. In the west and southwest, the rocks are intruded by igneous rocks of the Boulder batholith . As a result, Cambrian through Pennian strata of the west and southwest have been metamorphosed or heated sufficiently to increase their hardness and compactness, and to decrease signif­icantly their interstitial porosity and permeability. (2) The general sedimentary succession in the west and south is thinner than that in the northeast. This differ­ence results from original southwest depositional thin­ning of some units, such as the Big Snowy Group and the Amsden Formation, from erosional removal of some beds within the succession beneath unconformi­ties that increase in magnimde toward tbe southwest. and from assimila(ion or chemical modification of the units by adjacent intrusive bodies and the increased temperatures related to the intrusion. (3) Lower Creta­ceous sedimentary rocks in the northeast include a thicker succession of non-marine sedimentary rocks at the base of the Cretaceous than in the west and south­west, and the overlying succession of Lower Creta­ceous rocks in the southwest contains a substantially larger amount ofvoJcanic ash and particulate volcanic

12 Hydrology of rile Ilelena Area Bedrock, WeJ1-Cenlml Monlllna. 199]·98

debris than strata in the northeast. The ncar juxtaposi­tion of the major differences likely result from the slructuraltelescoping of the west and southwest suc­cession toward the nonheast succession along the Eldorado thrust fault and along a possible thrust fault concealed by igneous rocks of the Boulder batholith. As a general consequence of these factors, Cambrian through Cretaceous sedimentary rocks in the west and southwest likely have aqui fer characteristics dependent primarily on fracturing and faulting rather than on pri­mary or secondary solution porosity and penneability. In contrast, in the northeast, interstratal dissolution of relatively unaltered carbonate rocks and higher poros­iry and penneability of all the sedimentary succession, together with fracturing, likeJy produce more favorable aquifer characteristics, but not of hydrologic signi fi­cance in the study area.

Upper Cretaceous extrusive and intrusive rocks of the Elkhorn Mountains Volcanics are confined to the south and west parts of the Helena bedrock area (pl. I). The fonnation consists of tuff, tuff breccia, and flows in the lower part, rhyolitic welded ruff and volcanic breccia in the middle, and bedded tuff. bedded breccia, and sedimentary rocks in the upper part (Klepper, Rup­pel, and others, 1971; Smedes, 1966). The rocks have rhyolitic and rhyodacitic composition. Associated intrusive rocks , mapped together with the volcanic rocks on plate I, have compositions simjlar to the vol­canic rocks and all are considered products of the same magmas (Klepper, Ruppel, and others, 197 J; Green­wood and others. 1990). Much of the Elkhorn Moun­tains Volcanics along the southern margin of the Helena bedrock area is dense , compact rock, in which original textures are evident. Through much of the suc­cession, porosity and penneability seem to be very low, so that fractures and faults are likely the principal ele­ments for water transport and accumulation. In the high relief developed on the compact Elkhorn Moun­tain Volcanics, veneers of talus, other colluvium, and residuum deposits may enhance the aquifer properties of the Elkhom Mountains Volcanics.

Upper Cretaceous igneous intrusive rocks of the Boulder batholith and related stocks fonn the largest area of bedrock in the Helena area (pI. 1). These rocks are generally present in the south and west parts of the area, mainly south of the Bald Butte fault zone (pI. I). Only the ScratchgraveJ Hills. Marysville. and Silver City stocks and small stocks in the Sitzer Gulch area are north of the Bald Butte fault zone. No similar plu­tons are present north of the Helena Valley fault zone.

As generalized on plate I, the unit shown as Cretaceous intrusive rocks includes primarily granodiorite and granite, but also includes quaJ1z monzonite and monzo­nite of the Scratchgravel Hills and smaller plutons. South of Helena, the map unit also includes several small more mafic intrusive bodies (quanz diorite and diorite) that represent early stage intmsions of the Boulder batholith complex. The igneous rocks are wholly crystalline with little or no original porosity or permeability; exceptions occur where the crystalline rocks have been altered by late-stage intrusive l1uids or much younger ground-water/rock interactions along fractures and faults . Across much of the area, fractures and faults account for most movement and storage of water in the igneous rocks.

Tertiary intrusive and extrusive igneous rocks are confined to the west and south parts of the Helena bedrock area, mainly southwest of the Bald Buttc fault zone (pl. I). The older of these rocks are of Eocene age and crop out mainly in the Mullan Pass and Dread­naught Hi II areas near the west edge of the study area. The rocks consist of andesitic and basaltic lava tlows with imerstrati fied tuff and tuffbreccia beds. Flows are dense, commonly compact, but with local vesicular and flow banding textures. Fractures, which are common, are the main conduits for waler movement through the rock. Tuff and tuffaceous sediment near the base of the succession arc sites of springs at the surface. The younger rock units. mainly rhyolite intrusive rocks and related ruffs, are of Oligocene age. Concentrated near Ihe Continental Divide in the upper Tenmile Creek basin (Red and Lee Mountains) and in the Montana City area south ofl-lelena, these rocks occur as igneous domes, locally with associated flows. Most support hills with steep slopes not conducive to development and water prospecting.

Tertiary sedimentary rocks are exposed east and south of Lake Helena and near the confluence of Threemile and Silver Creeks in the northwest part of the Helena area . Strata of the former area are mostly of Oligocene age, whereas those of the latter area are likely younger-Pliocene en and Miocene age. Both successions of Tertiary rocks include interbedded sand­stone, conglomerate, clayey siltstone, 1lne si llstone, and sandy siltstone, all commonly containing a signifi­cant amount of day. The 0 I igocene rocks inc lude beds of rhyolitic tuff. silty tuff and, on the Spokane Bench in the eastern part of the area, pebble and cobble con­glomerate beds that suppon and cap hills on the bench. Some thin intervals in both sequences contain abundant

organic material derived from plants; other fine silt beds contain small gastropods and ostracods. which document the accumulation of the beds in freshwater lakes, ponds, and calm margins of streams. Beds in both areas are broken by faults and display through­going fractures. Southwest of East Helena. the Oligocene beds interfinger with volcanic tuff beds and breccia possibly derived from the area of Oligocene rhyolite intrusions near Montana City. The Oligocene sedimentary rocks originally extended over a much broader area than the Helena Valley; identical beds are present east of the area of this report in the Canyon Ferry Lake and Townsend Valley areas and locally atop the Big Belt Mountains. The broader Oligocene basin was disrupted by faults responsible for the present topography of the region.

Geologic Structure

The Helena area owes its physiographic fonn mainly to geologic structures that displace bedrock and valley fill. Geologic structures control not only the physiography but also the distributron and present character of the rocks. and hence have major influence on the occurrence and quality of water in bedrock. Two elements of the geologic structure are summarized here: the tectonic framework controlled by faults, and the configuration and influence of igneous intrusive bodies.

The principal controlling faults in the Helena area are the Helena Valley fault zone. along the north and northeast margin of the area, and the Bald Butte fault zone that crosses the central part of the area. Both fault zones contain major through-going tilUlts.

The Helena Valley fault zone extends cast­southeast from Canyon Creek, northwest of Helena, along the base of the North Hills, and curves southeast through Lakeside on Hauser Lake to bound the steep west front of tile Big Belt Mowltains (pI. l. fig. 3). There. displacement on the fault may be primarily ver­ticat, with the east side up as much as 10.000 ft. At the eastern end of Lake Helena. lesser fault strands, includ­ing (he Spokane Bench fault, Regulating Reservoir fault , and Spokane Hills fault (Schmidt. 1986) splay southeast from the main Helena Valley fault zone. Along each fault, geologic units are displaced rela­tively up on the east to fonn the topographically ele­vated east margin of Helena Valley. Ncar the northwest comer of Helena Valley, similar faults trend toward, and some merge with, the Helena Valley fault zone.

GEOLOGIC SF.:TTING \3

One srrand splays from the main zone in Canyon Creek northwest of rhe study area, extends southeast past Silver City as the Canyon Creek fault , and splits as the Silver Creek fault and an unnamed fault bounding the Scratchgravd Hills on the north. The Scratchgravel Hills faull and an unnamed fault a mile northeast trend from, but do not join, the main fault zone; those faults displace beds of Spokane and Greyson Fonnations and trend southeast into Helena Valley (pI. I) . The Helena Valley fault zone at the base of the Nonh Hills consists ora series offaults, parallel to the main strand, that off­set the Greyson and Spokane Formations against one another. The main fault zone displaces a major syncli­norium north of the faulr againsr a faulted anticlino­rium south of the fault: it f0l111S a boundary between a terrane south of tht! fault that contains (he Boulder batholith and numerous intrusive stocks from a terrane on the nOr1h that contains no stocks in the Helena area. The overall impact of the zone is ro displace a major segment or the Earth's crust relatively eastward on the north side orthe fault zone, and westward on the south side. The fault zone might have been the locus of the 1935 Helena earthquake (Sclunidt 1986).

The second principal fault is the Bald Butte fault zone, recognized and mapped carefully by Schmidt (1986) and shown in Schmidt and others ([994). The fault zone extends from Nevada Creek nearly 45 miles nOr1hwcst or Helena, through the City of Helena, and southeast nearly through Winston (fig. 3). Schmidt (1986) considered the fault zone to be the most active seismically among faults in the area. Displacement varies along Ihe trace of the fault zone, up on the north­east along some segments and up on the southwest along other segments. Within the area of plate I, the zone exhibits a component of left slip. The combined displacements demonstrate that the zone is a major fraclllre in the Earth's crust. From Birdseye southeasr nearly to Prickly Pear Creek, a fault strand of tile Bald Butte fault zone bounds Ihe west edge of a bedrock bench on which the City of Helena is buill. Records from waler wells drilled on the bench suggest that a veoeer of surficial sediment rests on the Middle ProTerozoic Greyson Fonnation and a small or faulted fragment of an intrusive body of granodiorite.

Together the Helena Valley fault zone and Bald Butte fault zone are components of a major continental fracture, originally referred to as the Lewis and Clark line (Billingsley and Locke, 1939; Mertic and olhers, ) 951; and Reynolds and Kleinkopf. 1977, and many subsequent authors) and currently referred to as the

14 Hydrology of (tic Helena Area Bedrock. West-Central Montana. 1993-98

Lewis and Clark fault zone (fig. 3). Helena Valley near the east end of rhe Lewis and Clark fault zone is inter­preted as a pull-aparr basin, developed as the block south of the Helena Valley fault zone extended west and collapsed with respect to the block north of the fault zone (Reynolds, 1979).

Northeast-trending faults displace Paleozoic and Mesozoic rocks south and southeast of Helena. The faulrs were active during Late Cretaceous time inas­much as several faults are truncated by rocks of the Boulder barholith or are intruded by small intrusive bodies that are early phases of intrusion of the batholith.

I n the northeast comer of rhe Helena area, Mid­dle Proterozoic rocks are faulted northeast and east over folded Paleozoic and Mesozoic sedimentary rocks on the Eldorado thrust fault. The thrust fault, exposed on the north flank of tbe North H ills, dips soulh and southwest at a [ow angle beneath the hills alleasl as far as the Helena Valley fault zone . Holes drilled through Proterozoic rocks at the edge of the thrust fault could penetrate the Paleozoic rocks . However, the highly fractured character of rocks both above and below the thrust fault and the sharp topographic gradient down to Ihe Missouri River to the east indicate that the upper t>everal hundred feet of the bedrock would produce minimal, or no, water, possibly of unsuitable quality for use.

All fall Its in the Helena area affect lhe hydrologic characteristics of rocks displaced by the faults. Rocks adjoining the faults arc commonly steeply tilted, are sheared with clay or micaceous miMrals and iron oxide and iron sulfate minerals on shear surfaces, and are highly shattered at places. Numerous small faults par­allel the major fault and displace the rocks withill a few feet of the major fau It. I n other observed instances, a zone of sheared clay-rich rock several feet to tens 0 r feet wide nlay occupy a fault. In areas such as the North Hills. closely parallel faults juxtapose rocks of markedly di [rerent grain sizes with the effecr of pro­ducing barriers to fluid flow. Clay on fault surfaces can also be a barrier to fluid flow across the fault. The described effects of faults are observed in rocks of all ages.

Boundaries between intrusive rocks and older sedimentary and volcanic rocks affect the occun'ence of ground-water resources. Generally rocks inro which the plulons are intruded are metamorphosed with a con­sequent change from more permeable and less dense structure to recrystallized less penneable and more

dense compact rock. Similarly, plutons can be more finely crystalline along their margins. Margins of small intrusive bodies in the Helena area indicate that the intrusive rock rose mainly vertically to dome the rocks into which they were moving. The north margin of the Boulder batholith from Colorado Gulch on the west to ncar East Helena on the east seems to rest on older sedimentary rocks. An upright nonnal succes­sion of rocks from the Middle Proterozoic Helena For­mation through lower Upper Cretaceous rocks dip south apparently beneath the batholith. Hamilton and Myers (1974) considered that the low-angle surface represented a surface view of the lower part or floor of an inverted tear-shaped intrusion. [n contrast. Klepper, Robinson, and Smedes (1971) interpreted the margin as an intnlsive contact into a major synclinorium that developed with the extrusion of large volumes of Elkhorn Mountains Volcanics. A third alternative interpretation is that the northeastern margin ofrhe plu­ton intruded along a strike-slip fault , active between Flume Gulch and Dry Gulch before intrusion that trans­ferred movement eastward to a thrust fault; thus, the intrusive contact from Dry Gulch to near Unionville may represent intrusion along the strike-slip fault, whereas farther east intrusion followed the low-angle fault surface of the thrust fault.

Application of the Generalized Bedrock Geologic Map

Plate I provides an intennediate-scale overview of the Helena bedrock area. The geologic map has been compiled at a scale of 1: 100,000 from the most widely available sources of geologic map infonnation (see index to geologic mapping on pI. 1). That infonnation has been updated by M. W. Reynolds for this report with more recent geologic mapping and field revision of published maps. A II well locations and all bedrock units penetrated during drilling have been con finned on geologic maps at the largest scale available. Source geologic maps are all at scales larger than plate I. Care has been taken to ensure accurate representation of the original geology at the compilation scale. However, positional accuracy of some features might be some­what diminished at the smaller scale of the base map when compared to the original data source. Also, line thicknesses for contacts and faults necessarily assume a greater width, relative to the real geologic feature, at the scale of the generalized map than on any original map. The map is not intended for large-scale, site­specific detailed planning.

Bedrock units throughout the Helena area are generally covered by young surficial deposits such as alluvium, colluvium, glacial debris, or windblown sed­iment. Thickness of such deposits varies /Tom veneers througb which the underlying bedrock is clearly dis­cernible to major thicknesses that conceal allunderly­ing bedrock and structure. Boundaries of major accumulations of surficial deposits are shown on plate I as finely dashed lines . These boundaries should not be considered precise at the map scale or at larger scales. Boundaries shown may be less accurate posi­tionally than bedrock contacts and faults because (I) surficial deposits commonly thin to a knife edge; different mappers will interpret the edge differently when drawing a boundary; or (2) the original geologic map maker was concerned principally with bedrock unilS and structure and thus overlooked, or did not orig­inally map as consistently, some surficial deposits . Veneers of surficial sediment, when saturated, can be local sources of recharge to underlying bedrock; use of the generalized map to define their distribution does not substitute for site specific mapping of such depos­its.

Specific knowledge is needed to determine the water-bearing properties of the geologic units at and surrounding a site because the units, including the igne~ ous and metamorphic rocks, have internal differences in stratigraphy, composition, mineralogy and grain size or crystallinity. These differences--together with struc­tural imprints such as faults, folds, and the spacing, ori­entation, degree of openness, and extent and type of mineral filling in fractures and faulrs--all affect the ability of rocks to store and transmit water. Identifying faults in crystalline intrusive rocks and volcanic ter­ranes can be more difficult than in sedimentary rock sequences.

HYDROLOGY

Water in bedrock of the Helena area is important to residents who utilize water from wells completed in bedrock and also to residents who depend on water pro­duced from the Helena valley-fill aquifer. Recharge to the bedrock primarily occurs by iofiltration ofprecipi­taLion, although recharge by infiltration of streamflow, leakage from irrigation canals, and infiltration of applied irrigation water also occurs and can be signifi­cant locally . Watcrproduclion from wells completed in the bedrock is mainly from joints, fractures, and other

HYDROLOGY 15

fonns of secondary porosity in the rock. Subsurface movement of water typically is from areas of high land­surface altitude to areas of lower altitude. Subsurface discharge from the bedrock is a significant source of recharge to the valley-fill aquiter (Briar and Madison, 1992).

The principal streams in the study area are the Missouri River, Prickly Pear Creek. Tenmile Creek, SevenmiJ.e Creek, and Silver Creek (fig. I); all of these creeks are perennial in at least their upper reaches. Other creeks and drainage channels typically are inter­mittent (having seasonal flow) or ephemeral (flowing only for short periods in response to precipitation and overland runoff).

Precipitation patterns and distribution vary by altitude throughout the study area. Average annual precipitation ranges from about LO in. at the lower land-surface altitudes in the Helena Valley to about 30 in. at the highest land-surface altitudes in the southwest part of the study area (fig. 2). Annual precipitation at Helena Regional Airport was greater than average dur­ing 1993. 1995. and 1998. and less than average during 1992, 1994, 1996, and 1997 (fig. 4). Annual precipita­tion at other measurement sites in and near the study area di (fered somewhat from that pattern.

Average monthly precipitation is largest during May and June at three of the four precipitation stations (fig. 5), althougb precipitation during April, July, and other months also can be large. The percentage of annual precipitation received during December through April increases at higher altitudes (fig. 5), pri­marily as the result of snowfall . Actual monthly pre­cipitation in and near the study area during January 1992 through May 1998 is shown in figure 6.

Much of the precipitation is consumed through the processes of evaporation and sublimation to the atmosphere and transpiration by plants. These pro­cesses collectively are referred to as evapotranspira­tion . According to the National Oceanic and Atmospheric Administration (1982), the potential annual evapotranspiration for the Helena area is about 30 in ., which is larger than the average annual precipi­tation in most of the stl:ldy area.

Infiltration of precipitation is the primary source of recharge LO bedrock in most areas. Recharge occurs when infiltration is greater than the sum of evapotrans­piration and soil-moisture deficit. Because infiltration ofprecipitalion likely exceeds evapotranspiration plus soil-moisture deficit only during the wetter part or parts of some years and recharge occurs only when infiltra-

16 Hydrology orthe Helena Ana Bedrock, WC:;I-Cenlrlll Monlana, 1993-1}8

lion is greater than the sum of evapotranspi ration and soil-moisture deficit, most bedrock in the study area receives only small amounts of recharge, ifany, during most years. Recharge events typically are episodic and occur mainly during extended periods of abundant rainfall or during periods of significant snowmelt.

The recharge process by infiltration ofprecipita­tion can be affected by the surficial geology . Where no soil is present and bedrock is exposed at the surface, recharge can occur directly tlrrough associated joints and fractures. Where bedrock is covered by soil. the soil-moisture deficit needs to be made up before recharge can occur. Soil-moisture deficit generally is made up only when annual precipitation is 13 in. or more (Philip E. Farnes. oral commun .. 2000, and Far­nes, 1978). In some areas, soil-moisture deficit proba­bly is not made up during intense, briefprecipilation events . Where bedrock is covered by veneers of unconsolidated deposits, relatively slow but constant recharge to the bedrock can occur if the unconsolidated deposits are saturated. Veneers of unconsol idated deposits are present in the southern part of the North Hills, the central and eastern parts of the Scratchgrave! Hills, various parts of the westem mountains, the northern part of the South Hills, and various other areas (pI. I).

Recharge to the bedrock very likely is not dis­tributed unifonnly across the study area. Amounts of recharge are difficult to measure and vary with location and climatic factors . Location factors include porosity and permeability of the geologic unit, slope, aspect, vegetative and soil cover, and soil-moisture deficit. Climatic factors include amount and intensity of pre­cipitation, and evapotranspiration. However, area­wide average annual amounts of recnarge can be esti­mated or inferred from other in formation. The average annual groU11d-water discharge from Helena area bed­rock to the valley-fill aquifer has been estimated to be about 40,000 acre-ft (Briar and Madison, 1992), and total discharge from the bedrock--including discharges to perennial streams. wells, and adjacent areas outside the boundaries of the valley-fill aquifer--would be larger yet. Therefore, the area-wide average annual recharge to the bedrock would need to be more than the average annual ground-water discharge to the valley­fill aquifer (estimated to be 40,000 acre-ft) to sustain ground-water levels and maintain the current subsur­face discharge to (he valley-fill aquifer.

20 Helena WSO (a\ ..---

IS Helena Regional Airpon) (elljlude 3.893

12 reO' above sea level) ------------- ----

8 ..--

4

0 1992 1993

30 Auslin lW (altilude 4,790 leel

~

25 above sea Ievell

20

15 ----- ;:.=.:.::.:. - -- ----

10

5

0 1992 1993

Ul 30 w

::I: (.)

~ 25 ~ ;i 0 20 ~ t:: 0- 15 [5 ILl a: 0.. 10

5

0 1992 1993

40 Rocker Peak r-lall~ude 8.000 reel

35 abo,"" ..,a level)

30

25

~ 20 ,

I

15

10

5

0 1992 1993

1961-90 average annual precipllatlon = 11.60

______ 1 ___ --==::-:'

-----------~----

.--

1994 1995 1996 1997

1961-90 average annual preclpil6110n = '~.7S

/ ,--

.--- - ------ -- --- - -- ----

___ r::-::::-:- - -.---

1994 1995 1996 1997

1961-90 s""ra!l<l annual precipit8110n ~ 25.66 / ,------------ ---- -- -~----r----

r--

1994 1995 1996 1997

/1~""rella annual precipil8tJon = 32.10

r- r--

r==-:- _____

1998

,-

---- - -- --

1998

1998

----------- -.-. -- ------- ---- -------------r-

~

1994 1995 1996 1997 1998

-

Figure 4. Annual precipitation for selected sites, 1992-98. Data from Western Regional Climate Center (2000a and b) and U.S. Department of Agriculture (Jeri Lynn Ward, written commun., 1998; 2000).

FIGURE4 17

2 r-----------------------------------------------------------------~

3

2

0

J

rn w r u ~ ~

3

;i 0 ~ I-' ~ 2 (3 w CC a.

o

4

3

2

a

Helena WSO (al Helena Regional Airpon) [allikJde 3,893 feal above sea level)

Jan Feb Mar Apr

Austin IW (allilude 4.790 IGel abovo sea level)

:-:-

:--:-

Jan Feb Mar Apr

Frohnar Meadows [ailitude 6,480 'eet above s<>a levef)

~, :-:-

:-

Jan Feb Mar Apr

Rocl<er Peak (altllude a,ooo feel abOlle SW level)

:-:-

:-

:-

Jan Feb Mar Apr

May June

:- -

May June

:-

:-

May June

-

May June

July Aug Sept Oct

:-~

:-

-

JUly Aug Sept Oct

:-- :-

-

July Aug Sepl Ocl

:-

:-:-

r--

July Aug Sept OCI

1961·90 average annual precipitalion _ I I ,00

Nov Dec

1ge1 · gO 8v<! rage annual pracrp<lalion - 15 75

:-

~

Nov Oec

1~61·90 avornge annual precipltauon _ 25 65

-

:-

Nov Dec

\96 '-90 average annual precip i la~on - 32 ,10

:-

:-

Nov Dec

-

Figure S. Average monthly precipitation for selected sites, 1961-90. Data 1rom Western Regional Climate Center (2000a and b) and U.S, Department of Agriculture (Jeri Lynn Ward, written commun., 1998; 2000).

18 Hyd"otogy of thr Helena Area Bedrock. West-Central Montana, 1993-98

6,----------------------------------------------------------------------,

2

4

2

o

Helena WSO (at Helena Regional Airport) {all~ude 3.893 leel above sea levell

AUSlinlW (allilu<1& 4.7llO lael above sea level)

Frohner Me,adows (allilude 6.480 leal abOve sea level)

f0-

~ ~ 7~ j

1992 1993 I

ri !

l ~ ~

1- t1 I . -I . I I . ~ 1994 f995 1996 1997 1998

12,----------------------------------------------------------------------, Rocker Peak (artitud. B.OOO leel above

10 - ... Ievel)

8

6

1992 1993 1994 1995 1996 f997 1998

Figure 6. Monthly precipitation for selected sites, January 1992 through May 1998. Data from Western Regional Climate Center (2000a and b) and U.S. Department of Agriculture (Jeri Lynn Ward, written commun., 1998; 2000).

FIGLIRE 6 19

Hydrogeologic characteristics of the bedrock are heterogeneous. Water levels in some wells vary across short distances; likewise, changes in water levels in wells due to recharge or discharge can be quite differ­ent in wells spaced closely together, indicating little or no hydraulic connection between some wells. Yields also vary markedly between some wells across short dislances.

The age of ground water in the Helena area bed­rock is relatively young. The apparent age--detined as the time since the water was isolated from the atmo­sphere during recharge--ranged from 6 to 42 years, based on concentrations of CFCs in water fi·om 20 wells throughout the area (table 6). Because land-use practices can affect the quality ofrccharge water, these apparent ages indicate that land-use practices during the last 40 years or so could have an effect on the present quality of water in the bedrock.

These and other aspects orthe hydrogeology of the Helena area bedrock are described separately in the following sections for the North Hills. Scratchgravel Hills. westem mountains. and South Hills areas.

North Hills

A verage annual precipitation in the North Hills typically ranges from about 10 to 16 in. (fig. 2). which is less than tJle average annual evapotranspiration. As a result, most bedrock areas ofche North Hills receive only small amounts of recharge, if any, in most years. Ex.amples of increases in water levels in response to recharge from infiltration ofprecipitalion can be seen in the hydrographs on plate 3. Several examples are listed in the table below. In contrast. water levels in some wells did not increase, or even decreased, during these same periods, indicating that recharge to bedrock

Time period Wells in Ih" Nonh Hills in wl>ic.h

the waUf level increased in response 10

rccharj!c during Ihe time period (pI. ))

in the North Hills area can vary with location and recharge event.

Recharge to bedrock can also occur locally from infiltration of streamflow. leakage from the Hclena Valley irrigation canal, and infiltration of irrigation water applied to fields. Silver Creek, pans of which are perennial, can provide recharge to alluvial deposits and bedrock immediately adjacent to the streams, but mainly is an area of discharge from the bedrock. Sim­ilarly. the Missouri River and Willow Creek are mainly areas of discharge from bedrock. All other streams in the North Hills are ephemeral or intennirtent and likely provide limited recharge to adjacent bedrock during times of intense or abundant rainfall and runoff. The Helena Valley irrigation canal, located along the south­ern foot of the North Hills, is unlined along some reaches and is lined with compacted earth along other reaches. Leakage from the canal can recharge bedrock locally bul has no effect on bedrock across most oflhe North Hills. Similarly, the land irrigated with water from the canal is limited, so infiltration from ilTigalion water is also areally limited. As an example of recharge from canal leakage, water levels in wells 132 and 136 generally increased during the April to Octo­ber irrigation season each year dud ng 1993-96 (pl . 3) .

Apparent ages of ground water were eSlima(cd from CFC data for water samples from three wells completed in the North Hills bedrock (fig. 7. table 6). Water collected in 1995 from the three wells ranged in age from 20 to 37 years .

Discharge from the North Hills bedrock is mainly through water withdrawals for domestic and stock use and by subsurface discharge to lhc Helena valley-fill aquifer along the southern edge oflhe Norlh Hills area . Water yields from wells completed in the

Remark~

May-June 1995

February 1996

May 1991'>

128. 194, t 95. and pos~ibly others

149. 194. and possibly others

Rehllivety wet period (fig. 6)

Un,ea,onably wann pan of period with precipitation and snowmelt

135, 141, and possibly others RcI~tively wet period (fig. 6)

20 HydroloJ:.v of the Hrlena Area BC{\Tock. West-C('ntral Montana. 1993-98

T. 12N.

T,11N.

T. ION.

T.9N.

4$°30,

T.8N.

R.6W.

199, 197

86 e

\ 113 I

-0'1 0

~ \~ ..=. \~

I(/)

0 ~ 0 , I

($ /C)

I

(") \..-,~ \~

\ \

I -'

(0 0 ,

{ /

> I

l /

(

~-I .,

e 98

196 '-

178 e

180,S 31

.::::.182 'V

187. 188

e 189 8 ,

8 192, 42

Western

mountains 100 e

102 6 104 8

'06

O~~ 34

35 q 8 , ./

r \

39 Jr' -'

8

... \~ t

I , )

"f'..../-' I

JI J ,

~ '-.~-' ,

Base mod,.oo hom U.S. GEological Survey Dlgi'al Line Graph data . 1 100.000, 1998

2, /' ./

o I o

I 2

RAW. IIi' R.3W. R.2W.

North Hills

195

'-46, ...... 12.

123, 37

135

e l30 9 8

'33

Helena

Valley

Spokane Bench

." ./ 88 0 51

®HElENA 55,.

, \

2 I

I 3

1D

Hills

3 4 5 MILES I t I I I

4 5 KILOMETERS

::3 9 G e

\

...... JEFFERSON CO .....

.....

EXPLANATION

LINE OF APPROXIMATE BOUNDARY DELINEATING NORTH HILLS, SCRATCHGRAVEL HILLS. WESTERN MOUNTAINS, AND SOUTH HillS

INVENTORIED WELL WITH WATER·QUALllY DATA

o No nitrate information

Well with nitrate concentmllon. in milligrams per liler:

e Less than 2

o 2 to less than 5

5 to tess (han 10

• Equ<l1 10 or greater than 10

12 Well number

20 Bold numeral Is the apparenl age of sampled waler, in years, determined from chtorofluoro­carbon (CFC) data

Figure 7, Apparent age and nitrate concentration in water from selected wells,

FIGURE 7 21

North Hills bedrock. as reported in 36 drillers ' logs reviewed for this study (table 3), range from 6[0 100 gal/min, wilh a median of 20 gal /min.

Water levels were measured monthly in 24 wells in the North Hills area (table 4). Well locations are shown on plate 2. Water-level hydrographs and trends are shown on plate 3. For the period of this study, water levels increased episodically in response to snowmelt and rain and, locally, in response to seasonal leakage from the Helena Valley canal or intiltration of applied irrigation walCr. Conversely, water levels decreased in response to natural discharge and water withdrawals, which typically arc largest in the summer. Water-level trends were analyzed statistically for 12 wells in the NOlih Hills having at \cast 3 successive years of near­monthly water-level data during Janu"ry \992 through May 1998 (pI. 3). The sratist ical analysis indicated a significant (p-vaillc less than 0.05) decreasing trend for two wells (wells 144 and 153), and an increasing trend for lWO wells (wells 136 and 163). No water-level trend was indicated for the othercight wells (wells 123, 128,129,132,149,151. 194, and 195).

Water from 15 wells completed in the North Hi lis area bedrock was sampled during 1994 and 1996 to derermine water chemistry (table 5). The water gen­erally was a mixed cation-bicarbonale type. a calcium­bicarbonate typc, or a mixed cation-l1lixed anion type (pI. 2). Water from 6 of Ihe II sampled wells com­pleted in the Spokane Fonnation was a mixed cation­bicarbonate rype. Watcr from three orlhe four sampled wells completed in the Greyson Fonnatiol1 was a calcium-bicarbonate type.

laboratory nitrate concentrations in water sam­ples obtained during! 994-98 rangcd from less than 0.05 to 17 mglL, and was greater Ih"n the maximum contaminant level (MCl) or 10 mgi L established by the EPA ( 1996) for public drink ing-water supplies in one of 15 wells sampled (well 195. fig. 7) . Nitrate con-

Tim~ period

L1te spring i 1\ 191}J and t994

May-June 1995

February 19%

May 1990

J:m uary-M!lrch 1997

Wells in (he Scra(ct.!!ra\·cl Hills in which lit" wHler ICI'e1 increDscd In rcsponS"IO r~charge during Ihe lime period tpl. 3)

59. 11 I. 66. and possibly others

59,60.66.68. and pos~ihly other.;

n I. 65.67, 174 . and possibly others

60. t73. nnd possibly OlhcTS

(,0.61. 65. 67 .1 74 . and pos~ibty others

centrations ill waler from well 195 ranged from 14 to 17 mg/L during 1994-98 (lanle 7, fig. 8). Sources of nitrate in water from two wells (wells 163 and 195) were in felTed [rom nitrogen-isotope ratios (fig. 9), land use, and chloride concemrations (table 7). Nitrate con­centrations in water from well 163 ranged from 2.6 to 3.2 mg/L during 1994-97. The inferred sources of nitrate in water from well 103 arc organic nitrogen from soil or a combin<Hion of sources (table 7). A large nitrogen-isotope ratio, large chloride concentrations, and proximity of septic systems (rable 7) indicate that a likely source of nitrate in water from well 195 is human or animal waste.

ConcentTations of trace elements in water (table 5) generally were low and did not exceed MCLs estab­lished by the EPA ( 1996) for drinking water. The total­recoverable iron concentration in water from two wells (wells 115 and 145) exceeded the secondalY maximum contaminant level (SMCL) established by the EPA (1996) for public drinking-water supplies. The source of the iron--wherher from thc bedrock or the plumbing systcm--is not known.

Water salnples from two wells (wclls 145 and 165) completed in the N0\1h Hills bedrock were ana­lyzed for VOCs (table 8). Concentrations of VOCs were less than minimum reporting levels.

Scratch gravel Hills

A verage annual precipilation in the Scratch­gravel Hills ranges from about 10 to 13 in. (fig. 2), which is less than the average annlla I evapotranspira­tion. As a result, most bedrock areas of the Scralch­gravel H ills receive only sma II amounts of recharge, if any, in most years. Examples of increases in water lev­els in response to recharge from infiltration ofprccipi­tation can be seen in 1he hydrographs on plate J. Several examples are lisred in rhe table below. During these periods, water levels in some wells did not

Remarks

Retalivdy wet periods (fig.. 6)

Relative Iy wet period (I·ig. fJ I

Unseilsonably wann purt of period with prccipilil( ion lind sllowtneJr

Relatively wet period (fig. 6)

Unseasollubly waml P:lrls or period wilh snowmeh

22 Hydrology of the Helena Area Bedrock. W"s4-Centrsl Montana. 1993·98

cc w I­:::; CC

~ 20 CJ)

:::i: <{ a: <,2 ...J ...J

~ ~

;1. 15

~ Z o ;:: <{ a: .... 2 W

~ 10 o (.J

w .... a: l-Z (/) ::l ...J £l. 5 w I-«

e- _____ _

---

/+- - - - - - - -+

/.--------. ---

)(- - - -1<,

0 , ">("'

\ .-.--... \ ,

!==================================~t~:;~~~~·~~:~~:~~ ~ - -0 -----:s.-------<)

a: l:: Z

O~J_~~~_L~_L~LL~~~~~~~~-L~~~~I~I-L~LL~I-L~-L~Ll~I~~ 1995 1996 1997 1994

NORTH HILLS: 6,163 e 195

EXPLANATION

AREA AND WELLS'

SCRATCHGRAVEL HILLS: WESTERN MOUNTAINS:

o 106 D 60 1II 173 0180

'il 187

SOUTH HILLS: + 46 X 87

Figure B. Temporal changes of nitrate concentration in water from nine wells, 1994-98. Dashed lines connecting symbols for individual wells are for visual aid only and do not imply knowledge of nitrate concentrations in the intervening periods between samples.

increase, or even decreased, indicating thar recharge to bedrock in the Scratchgravel Hills area can vary with location and recharge event.

Recharge to bedrock also can occur locally from infiltration of streamflow, infiltration of irrigation water applied to fields , leakage from a small irrigation canal in the south-cenlral part of tbe Scratchgravel Hills area , and leakage from the Helena Valley irriga­tion canal near the eastern edge of the area . The only perennial streams in (he area--parts of Silver Creek along the northern edge, Sevenmile Creek along the southwestern edge, and Tenmile Creek aiong the sourh-

em edge--can provide recharge under certain hydro­logic conditions to alluvial deposits and bedrock immediately adjacent to the streams, but mainly are areas of discharge from the bedrock. However, sheet flow and runoff in ephemeral streams within the Scratchgravel Hills likely provide limited recharge to bedrock during times 0 f intense or abundant precipita­tion. Infiltration of stTcamJ1ow from an ephemeral stream, as well as precipitation, during a period of intense rain fall and runoff in spring 1981 resulted in a substantial rise in water level in well 60 (pI. J). Leak­age from a small irrigation canal in the southem part of

HYDROLOGY 23

Fertilizer ~ __________ ~A~ __________ ~

Atmospheric deposition

r-"--. Organic nitrogen from soil Human or animal waste

r---------------~·~--------------~v,----~k~----~

~ 18 ....I ~ f- 16 0 f-

z: Q ([ 14 f-UJ «f-er-!2 ~ 12 UJW 00-

6 U) 10 o~ wa: l::~ 8f-a:....I f-:! 2:2 U) 6 -:::l -' 0-w 4 -I-

+187

+ 46*

87* +

-

+'95* -

-

-

-

--

<{ ([ I-

60 163 ++

173* + Z 2

+180 -

+ 106

0 2 3 4 567 8

NITROGEN-ISOTOPE RATIO, IN PERMIL

9 10 11

Figure 9. Nitrogen-isotope ratio and nitrate concentration in water from selected wells (identified by well number), Asterisk after well number denotes chloride concentration greater than 40 milligrams per liter in water. Italicized well number denotes that sample is affected by denitrification, original nitrogen-isotope ratio is likely smaller,

the area resulted in substantial seasonal water-level rises in wells located near and downgradient from the canal (wells 67 and 69) (pI. 3).

Apparent ages of ground water were estimated from CFC data for water samples from five wells com­pleted in the Scratchgravel Hills bedrock (fig. 7, table 6). Water collected in 1992 and 1995 from these wells ranged in age from 10 to 27 years.

Discharge from the Scratchgravel Hills bedrock is mainly through withdrawals for domestic and stock use, by subsurface flow toward and probable discharge to Sevenmile Creek, Tenmile Creek, and, during parts of the year, to Silver Creek. and by subsurface flow to the east to the Helena valley-fill aquifer. Water yields from wells completed in the Scratchgravel Hills bed­rock. as reported in 17 drillers' logs reviewed for this study, ranged from 3 to 60 gal/min, with a median of 12 gal/min.

Water levels were measured monthly in 16 wells in the Scratchgravel Hills area (table 4), Well locations are shown on plate 2. Water-level hydrographs and

24 Hydrology of the Helena Area Bedrock, West-Central Monlana, 19'.l3-~8

trends are shown on plate J. For the period of this study, water levels increased episodically in response to infiltration of rain or snowmelt and, locally, in response to seasonal leakage from a small irrigation canal. Conversely, water levels decreased in response to natural discharge and water withdrawals, which typ­ically are largest in summer. Water-level trends were analyzed statistically for I J wells in the Scratchgravel Hills having at least 3 successive years of near-monthly water-level data during January 1992 through May 1998 (pI. 3). The statistical analysis indicated a signif­icant (p-value less than 0.05) decreasing trend for two wells (wells 173 and 175) and an increasing trend for nine wells (wells 59, 60, 61, 65, 66, 67, 68, 69, and L 74). No water-levellrend was indicated for the other two wells (wells 63 and 166). Water-level data for a period considerably longer are available for two wells (wells 60 and) 74), For well 60, the water-level trend for November 1976 through May 1998 is decreasing, although the trend for January 1992 through May 1998 is increasing (fig. 10 and pI. 3). For well 174, the

w (.) <{ LL a:: ::. til Q Z :5 3: o -' W al I­W W LL

~ ..J w > w -' a: w I-

~

A 10n---~--,---.---,--,---.---,---,--"--,---,---r---r-~--~---'---.---'--'---.---,,

Wall 60

15

20

25

30

3S

B

, 0 ..... ~ . ~, J \

Tr., n(1 "r-oo 1 ,,713 -96 p-= <O,OOO 1

/ I . " \.4

0 1

r

Tmr1lJ IlI ll' I S92'~fl 0=«0,000 1

10n---'---'---'---.--'---'---.---'---'--'---'---.---'--'--~---'---'---'--'---'---"

~ . Well 174 -' w co I-w wl) w<{ LLLL :;za: -~ ..J(f)

15 .". .. • • , I I •

oe ~ •

" • -•

W Q 20 (ijz -':5

Tf,2nd I",E 1 ,1':<3 98

r",O.0004 a: w f-<{

3: 25UL __ ~ __ ~ __ L-__ L-~ __ ~ __ ~ __ -L __ -L __ ~ __ ~ __ L-__ L-~L-~ __ ~ __ -L __ -L __ ~ __ ~ __ ~

76 77 78 79 80 81 82 83 S4 85 86 87 88 89 90 91 92 93 94 95 96 97 98

c 7 ~--,---.---,--,---.---,---,--,---.---,---,---,--,,--,---.---,---.---,--,---.---,,

6

5

4 -

3

2

Helena WSO Monthly precipitation

77 78 79 80 81 82 83 S4 85 86 87 88 89 90 91 92 93 94 95 96 97 98

Figure 10. Long-term hydrographs for two wells completed in the Scratchgravel Hills bedrock and corresponding monthly precipitation. Period of record is about 23 years.

FIGURE J 0 25

long-tenn trend was not determined because of relatively large gaps in data for some parts of the record . Thc comparison of the long-teml water-level trend to the 'rend [or January 1992 through May 1998 for well 60 demonstrates that rrends detennined during the relatively short duration of this study do not necessarily reflect long-renn trends and that long-tenn monitoring can provide valuable infomlation.

Water from eight wells completed in the Scratch­gravel Hills bedrock was sampled during 1994 and 1996 to determine water chemistry (table 5). All eight wells were completed in granitic rocks, and the water from six of the eight wells was a calcillm-bicarbonate typc (pI. 2). Water from well 61 was a mixed cation­bicarbonate type. Water from well I 66--located on the northea.st tlank of the Scratch gravel Hills--was a cal­cium-chloride type nnd generally had much higher major-ion concentrations than water from other bed­rock wells in the study area. Inventory information indicates that household water is discharged near the well and likely affects the water quality at this site.

Laboratory nitrate concentrations in water sam­ples obtained during 1994-97 ranged from 0.56 to 37 mg/L. Water from one oflhe eight wells sampled (well 166, fig. 7) exceeded the MCl 0 [ J 0 mg/L estahllshed by the EPA ( 1996). This well is locared on the north­east nank of the Scratchgravel Hills and, as stated above, the water quality likely is affected by human activities. The hydraulic gradient is eastward, toward the valley, and the quality of water at this site does nor affect the quality of water in other wells to the west in Scratchgravel Hills bedrock. Sources of nitrate in wntcr from two wells (wells 60 and 173) were inferred from nitrogen-isotope ratios (fig. 9), land use, and chlo­ride concentrations (table 7). Nitrdte concentrations in water from well 60 ranged from 1.5 to 2.6 mg/L during 1990-97 (table 7). Nitrate concentrations in water from

Wells In rhe weSlern mountains in "hieh

well 173 ranged from 2.5 to 4.2 mg/L during 1996-97 (table 7). The inferred sources of nitrate in water from well 60 are organic nitrogen from soil or a combination of sources. The inferred sources of nitrate in water from well 173 are organic nitrogen from soil or a com­bination of sources including human or animal waste.

Concentrations of rrace elements in water (table 5) typically were low and most did not exceed MCLs established by the EPA (1996) for drinking water. However, water from well 166 did exceed the EPA SMCL for chloride and the EPA SMCL and MCl for sulfate .

A water sample from one well (well 61) com­pleted in the Scratchgravel Hills bedrock was analyzed for VOCs (table 8). Concentrations ofVOCs were less than minimum reporting levels.

Western Mountains

Average annual precipitation in the western mountains ranges from about 12 in. near the Scratch­gravel Hills to more than 30 in. at higher altitudes in the upper Tenmile Creek basin (fig. 2). Areas of the west­ern mountains in which average annual evapotranspira­tion is substantially larger lhan average annual pre­cipitation receive on Iy small amollnts of recharge, if any. in most years. However, larger amounts of re­charge probably occur during most years in the south­ern part of the western mountains where precipitation amounts approach or exceed 30 in. per year. Examples of recharge from infiltration ofprecipilation can be seen in the hydrographs on plate 3. Several examples are listed in the table below. During these periods, water levels in some wells did not increase. or even decreased, indicating that recharge to bedrock of the western mountains can vary with location and recharge evem.

Tim,· period the wall'r level increased In rrsponse Remarks

Mily-June 1995

February I ()96

May 1996

Aprit-June 1997

to recharge during the time period (pI. .'1

It2. 170, and possibly others Retatively wet period (fig. 6)

34.35. 98. 103. 105. t12. lot. t 69. 170. Uns.::asonably wann part of period with precipitation :md snowmelt 190. 199, and possibly olhers

32. 75, 112, 161. 169, 178. 180. and possibly olhers

96 and 91\

Relativ~ly wei period (tig. 6)

Relatively wet period (fig. 6)

26 Hydrology of fhl' Helena Arc~ Bedrock. ""'est-Central Montana. 199)-98

Recharge to bedrock also can occur locally from infiltration of streamflow, infiltration of applied irriga­tion water, and leakage from an irrigation canal. Ten­mile Creek, Sevenmile Creek, pans of Silver Creek, Threemile Creek, and Colorado Gulch. and many of the upper reaches of intennitlent streams in the western mountains are perennial. These streams or stream reaches can provide recharge under cenain hydrologic conditions to alluvial deposits and bedrock immedi­ately adjacent to the streams, but mainly are areas of discharge fTom the bedrock. Streamflow in losing reaches of ephemeral or intennittent streams within the westem mountains provides recharge to bedrock dur­ing times ofrunolT from snowmelt or rain. lnfiltration from Tenmile Creek to bedrock resulted in late spring rises in water levels in well 112 in 1995 cllld 1996 (pI. 3); a combination of intiltration from Tenmile Creek and an irrigation canal near Terunile Creek resulted in early summer lises in water levels in well 32 in 1994-96. Infiltration from Moose Creek duling late spring snowmelt resulted in rises in water levels in well 38 in 1994-96.

Apparent ages of ground water were estimated from CFC data for water samples from six wells com­pleted in the westem mountains bedrock (fig. 7. table 6). Water collected in 1995 from these wells ranged in age from 6 to 42 years.

Discharge from the westem mountains bedrock is through withdrawals for domestic and stock use and by subsurface discharge to Tenmile Creek, Sevenmile Creek, and gaining reaches of other streams. Well yields in the westem mountains bedrock, as reported in 53 drillers' logs. ranged from I to 90 gal/min, with a median well yield of 12 gal/min.

Water levels were measured monthly in 40 wells in rhe westem mountains area (table 4). Well locations are shown on plate 2. Water-level hydrographs and trends are shown on plate 3. For the period oflhis study, water levels increased episodically or seasonally in response to in fi Itration of rain or snowmelt. locally in response to seasonal infiltration ofstreamtlow and, locally in the lower parts of the area, in response to sea­sonalleakage from an irrigation canal. Conversely, water levels decreased in response to natmal discharge and water withdrawals. which typically are largest in summer. Water-level trends were analyzed statistically for 17 wells in the western mountains having at least 3 successive years of near-monthly water-level data dur­ing January) 992 through May 1998 (pl. 3). The statis­tical analysis indicated a significant (p-value less than

0.05) decreasing trend for one wei) (well 180) and an increasing trend for five wells (wells 75.77, 103. 160, 183). No water-level trend was i.odicated for J I wells (wells 32, 34, 35, 38, 112, 146, 16 I. 169, 170, ) &7, and 199).

Water from 29 wells completed in the western mountains area bedrock was sampled during 1994 and 1996 to detennine water chemistry (table 5). The water generally was a calcium-bicarbonate type, a magnesium-bicarbonate type, or a mixed cation­bicarbonate type water (pI. 2) . Waler from \3 of the 14 sampled wells completed in the Shepard, Snowslip, or Helena Fonnations was a magnesium-bicarbonate type (6 wells) or a mixed cation-bicarbonate type (7 wells). Water from all of the eight sampled wells in granitic rocks was a calcium-bicarbonate type (6 wells) or a mixed carion-bicarbonate type (2 wells) . Carbonate rocks in the Shepard, Snowslip, and Helena Fomlations are sources of magnesium in water and. together with gTanitic rocks, are the sources of calcium and bicarbon­ate in water in this area .

Laboratory nitrate concenrrations in samples obtained during 1994-97 mnged from less than 0.05 to ) 2 mg/L and were equal 10 or greater than the MCL of 10 mg/L established by the EPA (1996) in water (i·om 2 of the 29 wells sampled (wells 171 and 187, fig. 7). The nitrate conccntration in water from weI I 171 was 16 mg/L in 1996. Nitrate concentrations in water from well 187 ranged from 7.2 to 10 mglL during 1996-97 (table 7, tig. 8). Sources of nitrate in water from three wells (wells 106, ! 80. and 187) were inferred from nitrogen-isotope ratios (tig. 9) , land usc, and chloride concentrations (table 7). The inferred sources of nitTate in watcr from well 187 are organic nitrogen from soil or a combination of sources ((able 7, fig. 9). Nitrate concentrations in water from well 106 ranged from 1.2 to 5.4 mg/L, and in water from well 180 were consistently 0.7 mg/L during 1996-97 (table 7, fig . 8). The nitrogen isotope ratios for warer from wells 106 and 180 shown in figure 9 have been affected by deni­trification based on the oxygen-isotope ratios in rhe water. It'denitrlfication had not occurred. the expected nitrogen-isotope ratio would be about 3%0 in water from well 106 and about 00/00 in water from well 180. The inferred sources of nitrate in water from weill 06 are fertilizer or a combination of sources. The inferred source of the small concentrations of nitrate in water from well 180 is atmospheric deposition.

Concentrations of trace elements (table 5) typi­cally were low. The total-recoverable lead concentra-

HYDROLOGY 27

tion in water from well 34 (17 J.lg/L) exceeded the MCL of 15 J.lglL established by the EPA (\996) for drinking­water supplies. The total-recoverable concentration of iron in water from wells 34 and 182 and the total­recoverable concentration of manganese in waler from well 170 exceeded the SMCLs establ ished by the EPA (1996). The sources of the lead, iron, and mangancse--whether fTom the bedrock ortbe plumbing system--are not known .

Water samples fTom five wells (wells 39, 98, 104, 186, and 199) completed in western mountains bedrock were analyzed for VOCs (table 8). Concentra­tions ofVOCs were less than minimum reporting levels.

South Hills

Average annual precipitation in the South Hills ranges from about to in. at the lower altitudes near East Helena to nearly 30 in. at the higher altitudes in the southwestern part of the area (fig. 2). Areas of the South Hills in which average annual evapotranspira­tion is substantially larger than average annual precip­itation receive only small amounts of recharge, if any, in most years. However, larger amounts of recharge probably occur during most years in the southwestern part of the South Hills where precipitation amounts approach 30 in. per year. Examples of recharge from infiltration of precipitation can be seen in the hydro­graphs on plate 3. Several examples are listed in the table below. However, water levels in some wells did not increase, or even decreased, during these periods indicating thaI recharge to bedrock in the South Hills can vary with location and recharge event.

Recharge to bedrock in the South Hills also can occur locally as infiltration of streamflow. Perennial streams in the South Hills area include Prickly Pear Creek, McClellan Creek, and parts of Colorado Gulch.

Weill> In Ih~ South Rills In whkb the WOler

Lump Gulch, and Clancy Creek. These streams can provide recharge to immediately adjacent alluvial deposits and bedrock under certain hydrologic condi­tioos, but mainly are areas of discbarge from the bed­rock. Infiltration from Prickly Pear Creek resulted in late spring rises in water levels in well 12 (pI. 3). Streamflow in losing reaches of ephemeral or intermit­tent streams within the South H ills provides recharge to bedrock during limes of runoff from rain or snowmelt. Infihration from Grizzly Gulch during late spring snowmelt resulted in rises in water levels from well 19.

Another source of recharge in local areas is infi 1-tration from municipal water supplies applied for lawn irrigation. Infiltration to bedrock from the City of He 1-ena water supply via lawn irrigation supplemented pre­cipitation and collectively resulted in summer rises in water levels in well 55 (pI. 3).

Apparent ages of ground water were estimated from CFC data for water samples from six wells com­pleted in the South Hills bedrock (fig. 7, table 6). Water collected in 1995 from these wells ranged in age from 10 to 23 years.

Discharge from the South Hills bedrock is through withdrawals for domestic and stock use , by subsurface flow toward and probable discharge to Col­orado Gulch, Tenmile Creek, and Prickly Pear Creek, and by subsurface /low to the north to the Helena val­ley-fill aquifer. Well yields in the South Hills bedrock. as reported in 53 drillers' logs, ranged from 4 to 80 gal/min, with a median well yield of 15 gaJlm.in .

Water levels were measured monthly in 32 wells in Ihe South Hills area (table 4). Well locations are shown on plate 2. Water-level hydrographs and trends are shown on plale 3. For the period of this study, water levels increased episodically or seasonally in response to infiltration of rain or snowmelt, and locally in response to seasonal infiltration of streamflow and sea­sonal infillration from the City of Helena water supply

Time period level Increased in response Remarks to recharge during the rime period (pl. 3)

May-June 1995 12. 14. 19. 2 1.46. 55, and possibly Relatively wei period (fig. 6) other.;

February 1996 9, 12. 14. 22. 24. 53, 55, RO, S), 87, 88, Unseasonably wann part of period with precipitation and snowmelt 93. and possibly others

April-June 1997 14. 21. 55. and possibly others Relatively wet period (fig. 6)

28 H~'d(ology or the Helena Area Bedrock. Wesl..(:entral MoolJloa. 1993-98

via lawn irrigation. Conversely, water levels decreased in response to natural discharge and water withdrawals, which lypically are largest in summer. Water-level trends were analyzed statistically for 15 wells in the South Hills having at least 3 successive years of near­monthly water-level data during January 1992 through May 1998 (pI. J). The statistical analysis indicated a significant (p-value Jess than 0.05) decreasing trend for six wells (wells 12, 14.15,19.21. 83) and an increas­ing trend for three wells (wells 30, 46. 94) . No water­level trend was indicated for the other six wells (wells II. 22, 50, 55, 80, and 85).

Water from 18 wells completed in the Soulh Hills bedrock was sampled during 1994. 1996. and 1998 to determine water chemistry (table 5). The water generally was a calcium-bicarbonate rypc or a mixed calion-bicarbonate type water (pI. 2). Water from wells completed in granitic rocks typically was a calcium­bicarbonate type. Water from wells complered in the Helena Formation typically was a mixed cation­bicarbonate type.

laboratory nitrate concentrations in samples obtained during 1994-97 ranged from 0.05 to 24 mgfL and was greater than the MCl of 10 mgfL established by the EPA ( 1996) in 2 of the 18 wells sampled in the South Hills (wells 46 and 55. fig. 7) . Sources of nitrate in water from two wells (wells 46 and 87) were inferred from nitrogen-isotope ratios (fig. 9). land use, and chlo­ride concentration (table 7) . Nitrate concentrations in water ranged fTom 16 to 24 mgIL in well 46 during 1994-97 and from 5.2 to 6.9 mgll in well 87 during 1996-97 (table 7, fig . 8). The large concentration of chloride and large nitrogen-isotope ratio in water from these two wells indicate a nitrate source of human waste (table 7).

Concentrations of trace elements in water from bedrock (table 5) typically were low. The total­recoverable concentrdtion of lead in water from wel12l (16 ).lg/L) exceeded the MCl of 15 JlglL established by the EPA (1996) for drinking water and tbe total­recoverable concentration of cadmium in water from well 24 (28 Ilg/l) exceeded the MCl of 5 JlglL. Sub­sequent resampling of water from well 24 indicated a cadmium concentTation less than the minimum report­ing level. The total-recoverable concentration of iron in water from wells 3. 6,19, 21, and 55 exceeded the SMCl of 300 Jlgll established by the EPA ( 1996) for drinking water. The sources of the lead, cadmium. and iron--whcther from the bedrock, the plumbing system. or sample contamination--are not known.

Water samples from two wells (wells 21 and 27) completed in South Hills bedrock were analyzed for VOCs (table 8). Concentrations of VOCs were less than minimum reporting levels .

Ground-Water Availability

The availability of water in Helena area bedrock differs areally across short distances as a result of pre­cipitation, evapotranspiration. and the heterogeneous character of the rock types and the joint, fracture. and fault systems in the many different geologic units. However. the general availability can be inferred in terms of well depths, well yields. water-level fluctua­tions, and water-level trends. The depths of 198 of the wells inventoried for the entire study area range from 14 fl to 750 ft. with a median depth of 160 ft .

Well yields for the entire study area. as reported in drillers' logs for 159 wells, range from I gal/min to 100 gal/min, with a median value of 15 gal/min (table 3). Median well yields for each of the four areas do not differ greatly. A median welt yield of 15 gal/min typi­cally limits the use of the well to domestic supply. Well owners and local officials report that dry holes and wells having a very low yield can exist near wells having adequate yield . Records of such occurrences were not kept as part of this study. but additional infor­mation can be obtained from the WQPD.

Water levels in wells fluctuate il) response LO nat­ural and human-induced recharge and discharge. The magnitude of the fluctuations depends on the quantity of water recharged or discharged and on the porosity and permeability of the water-bearing rock. For a given amount of recharge or discharge. water-level fluctua­tions will be relatively large in wells completed in rock having small porosity and permeability compared to fluctuations in wells completed in more porous, perme­able rock. The hydrographs on plate 3 show large water-level fluctuations in some wells and small nuctu­ations in orhers. Some of the differences in the magni­tllde of water-level tluctuations are due, at least in part. to differences ill porosity and penneability.

Statistical analysis of water levels indicated trends for J I of the 58 wells having at least 3 years of consecutive monthly water-level data during the period January 1992 through May 1998. Of those, water levels in 19 wells showed an increasing trend and water levels in 12 wells showed a decreasing tTend. How­ever, the long-term trend also was detennined for one of the wells in the Scratchgravel !-lills. For this welt,

~IYDROLOGV 29

the water-level trend for November 1976 through May 1998 was decreasing, even though the tTend for January 1992 through May 1998 was increa~ing. , n any area of the bedrock, ifnatural and human-induced discharge exceeds recharge for a signi ficant period of time. water-level declines would be expected . Conversely, if recharge exceeds discharge, water-level rises would be expected. The magnitude of the declines or rises would depend on the average porosity of the rock in the area of consideration and the magnitude of the difference between discharge and recharge.

Application of the Hydrologic Information

The hydrologic information in this report can provide insight Lo the water resources in bedrock in the Helena area. However, the hydrologic information bas limitations. Although infornlation from more than 200 wells was used for this investigation, the density of coverage of that information is adequate only for appli­cation to broad areas, due primarily to the heteroge­neous character of the hydrogeology of the bedrock. A ppl ication of the infonnation to specific sites might not be appropriate. Water-level measurements were limited to domestic wells in which nonnal household use can affect the water level at the time of measure­ment. Water-level records collected during this study generally are for periods of less than 5 years during 1992-98. Records for significantly longer periods might indicate Irends that are different from the trends presented in this report. Water-quality information presented in th is report is speci fic to the selected wells at the time of sample collection: additional water-qual­ity infonnation from a larger number of wells or from morc frequent sampling of wells 10 detect seasonal or temporal water~quality variations might indicate water-quality characteristics or concerns not indicated by the infonnation currently available.

SUMMARY AND CONCLUSIONS

Water from Helena area bedrock is used by an increasing number of residents as the primary source of domestic water supply and also provides a large part of the annual recharge to the Helena valley-fill aquifer system. Public concern has been expressed that increased development and use of the limited water supplies within the Helena area bedrock may lead to depletion or contamination of this water resollrce. In 1993, the U.S. Geological Survey, in cooperation with the Lewis and Clark County Water Quality Protection

30 Hydrology oflbe HelenB Art'u Bl'drork. Wl'M-Crlllra' Monlana, 1993-98

District, began a study to assess the hydrology of Hel­ena area bedrock and to provide infonnation that can be used to evaluate future changes in the hydrologic sys­tem. Data for the study were obtained through inven­lOry of201 water wells, monthly measurements of water levels in 112 wells. and collection of water­quality samples from 70 wells.

Helena area bedrock units that contain ground water of concern in this report generally are exposed on the margins oftbe Helenli Valley. These bedrock units range from Middle Proterozoic to Tertiary in age and include sedimentary rock sequences. igneous intrusive rock units, and volcanic rock sequences. Different sequences of the bedrock units are present in three broad parts of the Helena area : (I) the north and north­east, bounded on the west by the Canyon Creek and Scratchgravel Hills faults, and described as the North Hills; (2) west and southwest of the same faults, desig­nated as the western mountains and Scratchgravel I-!ills; and (3) south and southwest of the Helena Val­ley, described as the South 1-1 ills.

The oldest rock units, the Greyson and Spokane Fonnations of tile Belt Supergroup, crop out east and north of the Canyon Creek and Silver Creek faults and the Bald Butte fault zone, Younger Bel! SupergTOup rocks, including the Empire and Helena Formations and the Missoula Group, are exposed mainly west and south of the Canyoo Creek and Silver Creek faults and the Bald Butte fault zone. Both the older and younger Belt sequences are metamorphosed regionally to low grade and are generally more compact than younger sedimentary rocks; as a result, through much of the sequences, fractures are likely the most important ave­nue for water movement and storage. Carbonate rocks of the Helena Formation are subjectllot only to fractur­ing. but also to dissolution of carbonate minerals.

SedimenLary rocks of Paleozoic and Mesozoic age are exposed west and south of rhe Bald Butte fault zone and in the no·rtheast. In the west and southwest, the sedimentary rocks are intnlded by the Boulder batholith and have been metamorphosed sufticiently to increase their hardness and compactness and to signif­icantly decrease their interstitial porosity and penne­abil ity, in the northeast, dissolution of carbonate rocks and higher porosity and penncability of the sedimen­tary succession. together with fracturing, likely pro­duce more favorable aquifer characteristics but not of hydrologic signi fica nee.

Upper Cretaceous eXlTUsive and intrusive rocks of the Elkhorn Mountain Volcanics are confined to the

south and west Through much of the succession, pri­mary porosity and penneability seem to be very low, so that fracrures and faults are likely the principal ele­ments for water transport and accumulation.

Upper Cretaceous igneous intrusive rocks of the Boulder batholith and related stocks fonn the largest area of bedrock in the Helena area. These rocks are mainly confined to areas south and west of the Bald Butte fault zone and to the Scratchgravel Hills. The igneous rocks are wholly crystalline with little or no primary porosity or penneability. Fractures and faults account for most movement and storage ofwaler in the igneous rocks.

Tertiary intrusive and extrusive igneous rocks are con fined to the west and south, mainly southwest of the Bald Butte fault zone. Fractures, which are com­mon, are the main conduits for water movement through the rock.

Tertiary sedimentalY rocks are exposed in the south and east and near the confluence of Three mile and Silver Creeks . The Tertiary rocks include inrer­bedded sandstone, conglomerate, clayey siltstone, fioe siltstone, and sandy siltstone, all commonly containing a signi ficant amount of clay. Beds in both areas are broken by faults and display through-going fractures.

The principal controlling faults in the Helena area are the Helena Valley fault zone along the north and northeast margin of the area, and the Bald Bulte fault zone that crosses the central part of the area. Together, the Helena Valley fault zone and the Bald BuHe fault zone are components ofa major continental fracture originally referred (0 as the Lewis and Clark line and currently referred to as the Lewis and Clark fault zone . The Helena Valley fault zone might have been the locus of the 1935 Helena earthquake. All faults in the Helena area affect the hydrogeologic char­acteristics of rocks displaced by the faults.

The heterogeneous characteristics of fracrured bedrock can result in highly variable welt yields and water levels over short distances. Ground water in the bedrock is contained in joints, fractures , and other forms of secondary porasiry in the rock.

Recharge to bedrock primarily occurs by direct infiltration of precipitation, although recharge by intil­tration of streamtlow, inti ltration from saturated over­lying unconsolidated deposits, leakage from irrigation canals, and infiltration of applied irrigation water also occurs and can be significant locally. Recharge by infiltration of precipitation occurs when infiltration is greater than the sum of evapotranspiration and soil-

moisture deficit; these conditions generally are satis­fied only during the wetter parts of some years, result­ing in small amounts of recharge. if any, during most years. Recharge events typically are episodic and occur mainly during extended periods of abundant rainfall or during periods of signi ficant snowmelt. Amounts of recharge vary with location and climatic factors.

The apparent age of ground water in the Helena area bedrock is relatively young, based on CFC data, ranging from 6 to 42 years. Consequently, land-use practices during the past 40 years or so could have an effect on present water quality in the bedrock.

Discharge from Helena area bedrock includes discharges to perennial streams. wells, and, in the sub~ surface, to adjacent areas. Average subsurface dis­charge from the Helena area bedrock into the valley-fill aquifer has been estimated to be 40,000 acre-feet per year.

Ground-water quality in Helena area bedrock generally is suitable for most uses and is affected by geology and 10cal.1y by human activity. Bedrock strongly influences the composition and concentration of major ions in the water. Water from 6 of the 70 wells sampled had nitrate concentrations that equaled or exceeded the MCl of 10 mg/L established by the EPA for public drinking-water supplies. Concentrations of trace elements in water generally were low. Concen­trations ofVOCs in all of 10 water samples analyzed were less than laboratory minimum reporting levels.

Bedrock in the North Hills receives recharge from infiltration of precipitation, infiltration of stream­tlowand, locally, from leakage from the Helena Valley irrigation canal and infiltration of applied ilTigation water. Average annual precipitation in the North Hills ranges from about 10 to 16 inches and provides limited recharge to bedrock during times of favorable precipi­tation and soil-moisture conditions. Perennial streams in the North Hills are mainly areas or discharge. Ephemeral or intermittent streams likely provide some recharge during times of runoff. Recharge from the Helena Valley irrigation canal and applied irrigation water is limited to the southern foot of the North Hills; the overall recharge from these sources to the North Hills bedrock probably is small. Yields from 36 wells in the North Hills bedrock ranged from 6 to 100 gal/min, with a median yield of 20 gal/min. Water lev­els analyzed for 12 wells for the period JanualY 1992 through May 1998 indicated a decreasing trend for 2 wells, an increasing trend for 2 wells, and no trend for

SUMMARY AND CONCLUSIONS 31

8 wells. Nitrate concentrations measured in water sam­ples from 15 wells ranged from less than 0.05 to 17 mg/L. Water from one well had nitrate concentrations greater than 10 mglL; the likely source of rhe high nitrate in water from the well is human or aoimal wasle.

Bedrock in the Scratchgravel Hills receives recharge from infiltration of precipitation and, locally, infiltration of streamflow, infiltration from inigation, leakage from a small irrigation canal in the south-cen­tral part, and leakage from the Helena Valley irrigation canal near the eastern edge. Average annual precipita­tion in the Scratchgravel Hills ranges from about 10 to 13 inches and provides limited recharge to bedrock duriog t.imes of favorable precipitation and soil­moisture conditions . The perennial streams in lhe area are mainly areas of discharge from the Scratchgravel Hills; however, runoffin ephemeral streams within the area likely provide some recharge to bedrock during times of intense or abundant precipitation . Recharge from a small irrigat ion canal in the soutbern part of the area can occur locally. Yields from 17 wells in the Scratchgravel Hills bedrock ranged from 3 to 60 gaVmin, with a median yield of 12 gal/min. Water lev­els analyzed for 13 wells for the period January 1992 through May 1998 indicated a decreasing trend for 2 wells, an increasing trend for 9 wells. and no trend for 2 wells. However, water levels examined for one well having more than 20 years of record indicated a decreasing long-tenn lTend, although the trend during January 1992 througb May 1998 was increasing. Nitrate concentrations measured in water samples from eight wells ranged from 0.56 to 37 mglL. Water from one well had a nitrate concentration greater than 10 mgIL and chloride and sulfate concentrations greater than rhe SMCL; the likely source 0 fhigh nitrate in water from the well is discharge of household water.

Bedrock in the western mountains receives recharge from infiltration ofprecipitatioll and,locally. from infillTation of streamflow, infiltration from iniga­tion, and leakage from an irrigation canal. Average annual precipitation in the western mountains ranges from about 12 to more than 30 inches and provides lim­ited recharge to bedrock during times of favorable pre­cipitation and soil-moisture conditions. Several streams in the area are perennial, along with the upper reaches of many of the intcnnittent streams, and mainly are areas of discharge from [he bedrock. Losing reaches of ephemeral or intennittent streams only pro­vide recharge to parts of the western mountains during times of runoff. Yields from 53 wells in the western

32 Hyd~ology of the Helena" rca Bedror.k. West-Central Monrana. 1993-98

mountains bedrock ranged from I to 90 gal/min. with a median yield of 12 gal/min. Water levels analyzed for 17 wells for the period January 1992 through May 1998 indicated a decreasing trend for I well, an increasing trend for 5 wells, and no trend for II wells. Nitrate concentrations measured in water samples from 29 wells ranged from less than 0.05 to 12 mg/L. with water from 2 wells having 10 mglL or more. The likely source of high nitrate in water from one of these two wells is organic nitrogen from soil or a combination of sources.

Bedrock in the South Hills receives recharge from infiltration of precipitation and, locally, from infiltration ofstreaml1ow, and infiltrdtion of municipal water supplies through lawn irrigation. Average annual precipitation in the South Hills ranges from about 10 to nearly 30 inches and provides limited recharge to bed­rock during times of favorable precipitation soil­moisture conditions. Perennial streams are located within parts of tbe South Hills and mainly are areas of discharge from the bedrock. Losing reaches of ephem­eral or intermittent streams only provide recharge to parts of the South Hills during times ofrunofffrom ("""din or snowmelt. Yields from 53 wells in the South Hills bedrock ranged from 4 to 80 gal/min, with a median yield of 15 gal/min. Water levels analyzed for 15 wells for the period January 1992 through May 1998 indi­cated a decreasing trend for 6 wells, an increasing trend for 3 wells, and no tTend for 6 wells. Nitrate concentra­tions measured in water samples from 18 wells ranged from 0.05 to 24 mgIL, WiTh water from 2 wells having more than 10 mg/L. The likely source of nitrate in water from one of these two wells is human waste.

Availability of water in Helena area bedrock dif­fers areally across short distances as a result of precip­itation, evapotranspiration, and the heterogeneous character 0 f the rock types and joint, fracture, and fault systems in the many different geologic units . The depths of 198 of the wells inventoried for the entire study area ranged from 14 to 750 ft, with a median depth of 160 ft . Well yields, as reported in drillers' logs for 159 wells, range from I to 100 gaVmin, with a median yield of 15 gal/min. A median yield of J 5 gal/min typically limits the use of the well to domestic supply.

Water levels in wells fluctuate in response to nat­ural and human-induced recharge and discharge. Tbe magnitude of the fluctuations depends on the quantity of water recharged or discharged and on the porosity and penneability of the water-bearing rock. In any area

of the bedrock, ifnatural and human-induced discharge exceeds recharge for a significant period of time, water-level declines would be expected. Conversely, if recharge exceeds discharge, water-level rises would be expected.

Statistical analysis of water levels indicated trends ior 30 of the 57 wells having at least 3 succes­sive years of near-monthly water-level data during the period of January 1992 through May 1998. Of those, water levels in 19 welts showed an increasing trend and water levels in II wells showed a decreasing trend. The differences in the water-level trends indicate the local nature and variability of recharge and discharge throughout the Helena bedrock area .

SELECTED REFERENCES

[Reports by private companies can be obtained through the Lewis and Clark County Water Quality Protection District Library, Helena, Mont.]

Amberger, A., and Schmidt, H.L., 1987. Natural isotope abundance ofnilrale as an indicator of its origin : Geochimica et Cosmochimica Acta, v. 51, p. 2699-2705.

Baumann. Brent, and Clark, K. B., 1991, Limited groundwater sT1.ldy, Highland Park Subdivision, Helena, Montana: Helena. Mont., Chen-Northern, Tnc .• October 9, 1991,5 p.

Becraft, G .E .. Pinkney, D.M., and Rosenblum. Sam, 1963. Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: U.S. Geological Survey Professional Paper 428, pI. I, scale 1:48 ,000.

Billingsley, P.R. , and Locke, Augustus, 1939, Structure of ore deposits in the continental framework : New York, American Institute of Mining and Metallurgical Engineers, 51 p.

Bottcher, l, Strebel , 0 ., Voerkelius, Susanne, and Schmidt, H. L., 1990. Using isotope fractionation of nitrate-nitrogen and nitrate-oxygen for evaluation of microbial denitrification in a sandy aquifer: Journal of Hydrology, v. 114, p. 413-424.

Boyce, J.S., Muir, John, Edwards. A.P., Seim, E.C.. and Olson, R.A., 1976, Geologic nitrogen in Pleistocene loess of Nebraska: Journal of Environmental Quality, v. 5, p. 93-96.

Bregman, M. L., 1981, Structural geology of the Sheep Creek and Rattlesnake Mountain quadrangles, Lewis and Clark County, Montana: Montana Bureau of Mines and Geology Geologic Map 26, scale 1:24,000.

Briar, D. W., and Madison, J.P., J 992. Hydrogeology of the Helena valley-fill aquifer system, west-central Montana: U.S. Geological Survey Water­Resources Investigations Report 92-4023,92 p.

Busenberg, Eurybiades, and Plummer, L. N .. 1992. Use of chloroi1uoromelhanes (CCI)F and CCI2F2) as hydrologic tracers and age-dating tools--The alluvium and terrace system of central Oklahoma: Waler Resources Research, v. 28, p. 2257-2283.

Daniel, Faith, and Berg, R.B., 1981, Radiometric dates of rocks in Montana: Montana Bureau of Mines and Geology Bulletin I 14, 136 p.

Drake, V.M., 1991, Hydrogeological charactcrization of the Helena Valley aqlli fer system based upon statistical evaluation of selected groundwater chemical parameters: Butte, Montana College of Mineral Science and Technology, M.S . thesis. 153 p.

Drake. V.M., 1995, Helena Valley aquifer groundwater nitrate concentralion trends : Helena, Monl.. Lewis and Clark COUIlTy Water Quality Protection District. May 1995, 30 p.

Driscoll, F.G., 1986. Groundwater and wells (2d ed.): St. Paul, Minn .. Johnson Division, 1089 p.

Fames, P.E., 1978, Preliminary report, hydrology of mountain watersheds: Bozeman, Monl., U.S . Department of Agriculture. Soil Conservation Service, revised May 1978. 7 p.

Flipse, W.J .. Jr., and Bonner, F.T., 1985, Nitrogen­isotope ratios of nitrate in ground water under fertilized fields, Long Island, New York: Ground Water, v. 23, p. 59·67.

Freeze. R.A., and Cherry. J.A ., J 979. Groundwater: Englewood, Cliffs, N.J., Prentice-Hall, Inc., 604 p.

Gonnly. l.R., and Spalding, R.F., 1979, Sources and concentrations of nitrate-nitrogen in groundwater of the central Platte region, Nebraska: Ground Water, v. 17, p. 291-301.

Greenwood, W.R., Ludington, Steve, Miller, W.R., and Hanna, W.F ., 1990, Mineral resources of the Elkhorn Wilderness Study Area, Broadwater and Jefferson Counties, Montana, with a section 011

Uranium and thorium potential. by K.J . Wenrich. W .R. Miller. V.J . Suits, and J.B. McHugh: U.S. Geological Survey Bulletin J 805 , 37 p.

Hamilton, Warren, and Myers, W.B .. 1974. Nature of the Boulder batholith of Montana: Geological Society of America Bulletin. v. 85. p. 365-378.

Hansen, W .R., ed., 1991. Suggestiol1s to authors of the reports of the United States Geological Survey (7th ed.}: U.S. Government Printing Office, 289 p.

Harrison, J.E., 1972, Precambrian Belt basin of northwestern United States--Its geometry, sedimentation, and copper occurrences:

SELECTED REFERENCES 33

Geological Society of America Bulletin, v. 83, p. 1215-1240.

Heaton. T.H.E .. 1986, Isotopic studies of nitrogen pollution in the hydrosphere and atmospnere--a review: Chemical Geology (Isotope Geoscience section), v. 59, p. 87-102.

Hubner, H .. 1986, Isotope effects of nitrogen in the soil and biosphere, ill Fritz. P., and Fontes, lC., eds., Handbook of environmental isotope geochemistry. v. 2, The terrestrial environment. B: Amsterdam. Elsevier, chap, 9, p. 361-425.

Huntington Chen-Northern, 1991. Data summary report, Seratchgravel Sanitary Landfill: Helena. Mont., p. 13-14.

Hydrometrics. Tnc., 1991, A summary of fall 1989 and 1990 groundwater monitoring at the Lewis and Clark County Landfill: Helena, Mont.. Hydrometries. September 1991 [variously paged].

Jackson, J.A., ed., 1997, Glossary of geology. 4th cd.: Alexandria, Va., American Geological Institute, 769 p.

James M. Montgomery, Consulting Engineers. Inc., 1977, V.A. Center, Fort Harrison, Montana, Engineering feasibility and economic srudy of the water supply system: Boise, Ida .. May 1977 [variously paged].

Kaczmarek, M. B .. 1995, Results of a 96-hour pumping test of the Skyview no. J well and observation data from the Townview no. 2 well perfonned as part of the M& W Enterprises, LLC application for beneficial water use permit: Helena, Mont., Morrison~Maierle, Jnc. July 1995 [variously paged].

Kendall. Carol. and Grim. E .• 1990, Combustion tube method for measurement ofnilrogen isotope ratios using calcium oxide for lotal removal of carbon dioxide and water: Analytical Chemistry, v. 62, p. 526-529.

Kendall. Carol, Silva, S.R., Chang, c.c.Y .. Bums, D.A., Campbell, D.H., and Shanley, J.B ., 1996, Use oCthe 8180 and 815N of nitrate to detennine sources ofnitrate in early spring runoff in forested catchments, in IAEA Conference and Symposium Proceedings of the International Symposium on Isotopes in Water Resources Management, Vienna, Austria, March 20-24, 1995: International Atomic Energy Agency, p. 167-176.

Kendy. Eloise, and Tresch. R.E .. 1996. Geographic, geologic and hydrologic summaries of intennontane basins of the Northern Rocky Mountains, Montana: U.S. Geological Survey Water-Resources Investigations Report 96-4025, 233 p.

34 Hydrology of the Helena Area Bedrock, W~"St-Ccntr81 Montana, J 993-98

Klepper. M.R .. Robinson. G.D., and Smedes, H .. 1971, On the nature of the Boulder batholith of Montana: Geological Socicty of America Bulletin, v. 82. p. 1563-1580.

Klepper, M.R .. Ruppel , E.T., Freeman, V.L., and Weeks, R.A., 1971, Geology and mineral deposits. east flank of the Elkhorn Mountains, Broadwater County, Montana: U.S. Geological Survey Professional Paper 665, 66 p.

Knopf, Adolf, 1913, Ore deposits of the Helena mining region, Montana: U.S . Geological Survey Bulletin 527. 143 p.

Knopf. Adolf, 1963, Geology of the northern part of the Boulder bathylith and adjacent area, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-381 , scale 1:48,000.

Knudson, Ken. and Swanson. Dick, 1977, Disappearance of the. trout fishery from Si I ver Creek downstream from mill ponds containing high concentrations of heavy metals and cyanide: Helena, Mont, Montana Department of Fish and Game report dated January 1977. 22 p.

Kreitler, C. W., ) 975, Determining the source of nitrate in ground water by nitrogen isotope studies: Austin, Texas. Bureau of Economic Geology. University of Texas at Austin Report of Investigations 83, 57 p.

LeTolle, Rene, 1980, Nitrogen-I 5 in the natural environment, ill Fritz, P., and Fonles, lC., eds., Handbook of environmental isotope geochemistry, v. 1, The terrestrial environment, A: Amsterdam. Elsevier, chap. 10. p. 407-433.

Lewis and Clark Areawide Planning Organization and {he Green Meadow Study Commit1ee, 1977. Green Meadow study area: Helena, Mon!., 78 p.

Lindau. C.W .. and Spalding, R.F., 1984, Major procedural discrepancies in soil extracted nitrate levels and nitrogen isotopic values: Ground Water, v. 22, p. 273-278.

Lorenz, H. W., and Swenson. F.A., 1951 , Geology and ground-water resources of the Helena VaHey, Montana, with a sectiOIl 011 The chemical quality of the water, by H.A. Swenson: U.S. Geological Survey Circular 83. 68 p.

Madison. RJ .. and Brunett, J.O ., 1985, Overview of the occurrence of nitrate in ground water of the United States, ill National Water Summary 1984-­Hydrologic events, selected water-quality trends and ground-water resources: U.S. Geological Survey Water-Supply Paper 2275, p. 93-105.

Mertie, J.B .. Jr., Fischer, R.P. , and Hobbs. S.W., 1951, Geology of Ihe Canyon Ferry quadrangle, Montana : U.S. Geological Survey Bulletin 972, 97 p.

Moreland , J.A., and Leonard, R. B., t 980, Evaluation of shallow aquifers in the Helena Valley, Lewis and Clark County. Montana: U.S. Geological Survey Water-Resources Investigations Open-File Report 80-1 102. 24 p.

Moreland. J.A., Leonard. R.B .. Reed. T.E., Clausen, R.O., and Wood, W.A., 1979, Hydrologic data from selected wells in the Helena Valley, Lewis and Clark County, Montana: U.S . Geological Survey Open-File Report 79-1676, 54 p.

Mueller, D.K .. and Helsel. D.R., 1996. Nutrients in the Nation's waters--Too much ofa good thing?: U.S. Geological Survey Circular 1136, 24 p.

National Oceanic and Atmospheric Administration. 1961-90 (issued monthly), Climatological data for Montana: Asheville, N.C, National Climatic Data Center.

National Oceanic and Atmospheric Administration, 1982. Evaporation alias for the contiguous 48 United States: Asheville, N.C, NOAA Technical Report NWS33, 26 p.

Nimick, D.A.. and Thamke, IN., 1998, Extent, magnitude, and sources of nitrate in the Flaxville and underlying aquifers, Fort Peck Indian Reservation. northeastern Montana: U.S. Geological Survey Water-Resources Investigations Report 98-4079, 45 p.

Pioneer Technical Services, Inc. , 1995, Abandoned hardrock mine priority sites, 1995 Summary report: prepared for Montana Department of State Lands. Abandoned Mine Reclamation Bureau, Engineering Services Agreement DSL-AMRB, No. 94-006.

Plummer. L.N., and Friedman, L.C, J 999, Tracing and dating young ground water: U.S. Geological Survey Fact Sheet 134-99.4 p.

PRC Environmental Management, Inc., J 995. Hydrogeology addendum, in Draft final environmental assessment, Montana Army National Guard, Fort Harrison Land Exchange: Helena. Mont., prepared for Montana Army National Guard, Fort Harrison, Helena, Mont., appendix A, 15 p.

Reynolds. M.W., 1979, Character and extent of basin­range faulting, western Montana and east-central Idaho ill Rocky Mountain Association of Geologists and Utah Geological Association Guidebook, Basin and Range Symposium, 1979: p.185-193.

Reynolds, M.W., and KleinkopC M.D., 1977. The Lewis and Clark line, Montana-ldaho--A major intraplate tectonic boundary [abs .]: Geological Society of Amedca Abstracts with Programs, v. 9, p. 1140-1 141.

Robinson, G.D., McCallum. M.E., and Hays, W.H., 1969, Geologic map of the Upper Holter Lake quadrangle, Lewis and Clark County, Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-H40, scale 1:24,000.

Ruppel, E.T., 1963, Geology orthe Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: U.S. Geological Survey Bulletin I lSI. pI. I, scale 1:48,000.

Schmidt, R.G., 1986, Geology. earthquake hazards. and land use in the Helena area, Montana--a review: U.S. Geological Survey Professional Paper 1316. 64 p.

Schmidt, R.G., Loen,J .S .. Wallace, CA .. and Mehnert, H.B., 1994, Geology of the Elliston region, Powell and Lewis and Clark Counties, Montana: U.S. Geological Survey Bulletin 2045, pI. I, scale 1:62,500.

Scientific Applications International Corporation, 1989, Hydrologic testing and investigations for beneficial water use permit no . 65217-G411: Scientific Applications International Corporation, 37 p.

Smedes, H.W., 1966. Geology and igneous petrology of the northern Elkhorn Mountains. Jefferson and Broadwater Counties. Montana: U.S. Geological Survey Professional Paper 510. 116 p.

Spalding. R.F., Exner, M.E .. Lindau, CW., and Eaton , D.W., 1982. Investigation of sources of groundwater nitrate contamination in the Burbank-Wallula area of Washington, U.S.A. : Joumal of Hydrology, v. 58. p. 307-324.

Stickney, M.e.. 1987, Quaternary geologic map of the Helena Valley, Montana: Montana Bureau of Mines and Geology Geologic Map Series 46, scale 1:50,000.

Stiller, David, and Associales, 1983, Hydrologic investigation of the Scratchgravel sanitalY landfill, Lewis and Clark County, Montana: Helena, Mont., David Stiller and Associates [variously paged].

Streckeisen, A.J., 1973, Plutonic rocks--classification and nomenclature recommended by the lUGS Subcommission on the Systematics of Igneous Rocks: Geotimes. v. 18, no. 10, p. 26-30.

U.S. Environmental Protection Agency, 1979, Methods for chemical analysis of water and wastes, with updates : EPA 600/4- 79-020 [variously paged] .

U.S . Environmental Protection Agency, 19H6, Method 60 10--lnductively coupled plasma-atomic emission spect(Oscopy: Method 7000--Atomic absorption spectroscopy; Method 7470--Mercury in liquid waste (manual cold-vapor technique): EPA SW-846 [variously paged].

SELECTED REFERENCES 35

U.S. Environmental Protection Agency, 1988, Methods for the detennination of organic compounds in drinking water, with updates: EPA 600/4-SX-039 [variously paged].

U.S. Environmental Protection Agency, 1993. Methods for the detennination of inorganics in environmental samples, with updates: EPA 6001R-93/ 100 [variously paged).

U.S. Environmental Protection Agency. 1994. Methods of the detennination of metals in environmental samples, with updates: EPA 600/R-94/ III [variously paged].

U.S. Environmental Protection Agency, 1996, Drinking water regulations and health advisories : Washington, D.C. , Office of Water, EPA 822-R-96-001, 11 p.

Voerkelius, S. , and Schmidt. H.L., 1990, Natural oxygen and nitrogen abundance of compounds involved in denitnfication : Mitteilungen der Deutschen Bodenkundlichen Gessclschaft, v. 60, p.364-366.

Wallace, CA .. comp., 1987, Generalized geologic map of the Butte 1° x 2° quadrangle. Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF -1925, scale 1:250,000.

Wassenaar. L.I. , 1995. Evaluation of the origin and fate of nitrate in the Abbotsford aquifer using the isotopes of 15N and 180 in NO]-: Applied Geochemistry, v. 10, p. 391-405.

Western Regional Climate Center, 2000a, Helena WSO. Montana-Climate Summary: accessed

36 HydroJogy of the Helena An'a Bedrock. Wesr-C~l1lnlf 1\!lonlllna. 1993-98

August 14,2000. at URL: http:// www.WRCCdri.eduJ.

Westem Regional Climate Center. 2000b, Austin I W, Montana-Climate Summary: accessed August 14. 2000, ar URL: http://www.WRCCdri.eduJ.

Wetzel, Kevyn, 1993, Scratchgravel Hills geohydrology--a re-evaluation : Helena, Mont. , Helena High School. unpublished science seminar paper, May 1993, 23 p.

Wetzel , Wayne. and Hanneman. Debra. 1983. Scratchgravel Hills geohydrology: Montana Department of Natural Resources and Conservation Water Resources Report, 60 p.

Wil.ke, K.R. , and Coffin, D.L., 1973, Appraisal of the quality of ground water in the Helena Valley, Montana : U.S . Geological Survey Water­Resources Investigations 32-73,31 p.

Wilke, K.R., and Johnson. M.V., 1978, Maps showing depth to water table. September 1976. and area inundated by the June 1975 flood, Helena Valley, Lewis and Clark County. Montana: U.s. Geological Survey Open-File RepoTl 78-1 lO, scale 1:62 ,500.

Wilson, W.E., and Moore, 1.E., eds., 1998. Glossary of hydrology; Alexandria , Va .. American Geological Institute, 248 p.

Wolterink, TJ. , Williamson, H.J .. Jones, D.C., Grimshaw. T.W., and Holland, W.F., 1979. Identifying sources of subsurface nitrate pollution with stable nitrogen isotopes: U.S. Environmental Protection Agency. EPA-600/4-79-050.

APPENDIX

APP~NDIX 37

Table I. Geologic time chart

[lvlodi lied from Hansen ( 1991). Abbreviation: Ma. mega-annum or mi nious of years. Symbol: - . approximalely I

EON ERA PERIOD

Quaternary

Neogene Cenozoic Subperiod

Tertiary Paleogene SUbperiod

Cretaceous

Mesozoic Jurassic

Triassic

Phanerozoic

Penninn

Carboniferous Pennsylvananian

Periods

Missi~sippian

Devonian Paleozoic

S ilurian

Ordovician

Cambrian

Late Protcrowic

Proterozoic Middle Proterozoic

Early Proterozoic

LaIC Archean

Archean Middle Arche.1.n

Early Archean

f- - - - - - - - - - - - - - - - -3800'! -prc-Archean 2

I Rocks older than 570 Ma also cnlled Precambnan, a lime term wlIhoul specIfic rank . 21nlomlallimc (erm withoul specific rank .

38 Hydrology of (he Helena Area Bedrock. Wesl-Central Mont:ma, 1993-98

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late Early

Latc Middle Early

Late Middle Early

Late Early

Lare Middle Early

Late Early

La[e

Middle Early

Late Middle Early

Late Middle Early

Late Middle Early

- - - -

BOUNDARY AGE

IN MILLION YFARS

0.010

1.6

5

24

38

55

60 96 IJll

205

-240

290

-330

360

410

435

500

-5701

900

1600

2500

3000

3400

4550

DEFINITIONS

Because of the complex nature of the study area hydrology and geology, some tenns commonly used {o describe hydrologic and geologic features may not be familiar and are defined below. Other tenns are defined in the text, are generally known, or can be found in the Glossary of Hydrology (Wilson and Moore, 1998) or the Glossary of Geo logy (Jackson, 1997).

Anticline--A convex upward fold in which the oldest rocks are in the center

Anticlinorium--A composite anticlinal stmcture of broad areal extent composed of lesser folds

Argillite--I-Iard, dense sedimentary rock, composed of dominantly clay-sized and some admixed silt­sized particles, which has undergone regional low-grade metamorphism. Stratification, sedimentary structures, and other internal sedimentary features are well preserved through the low-grade metamorphism

Batholith--A large mass of plutonic rock that is exposed across an area of 40 mi 2 ( 100 km2) or more. The plutonic rock has intruded older rocks discordantly, generally at high tempera t ures

Breccia--A coarse clastic rock consisting of angular rock andJor mineral fragments of various sizes held together by a mineral cement or finer mineral or rock particles

Denitrification--A multi-step process in which nitrate (NO)) is converted to nitrogen gas by bacteria in an anaerobic environment

Dolostone--A sedimentary rock composed dominantly of the mineral dolomite, a calcium-magnesium carbonate mineral. Dolostone is usually a post­depositional replacement of the sedimentary rock limestone. Original stratification, sedimentary srructLlJes, and. in some strata, fossils are generally preserved in dolostone

Dome-An igneous intrusion whose exposed upper surface is convex upward and whose sides slope away from the center at angles that increase with depth. A dome is described as elongate where the curved surface is longer in one direction than in the perpendicular direction. In the case of the Scratchgravel Hills pluton, the elliptical shape of monzonite outcrops is the

surface expression of a dome elongated in a north-northwest direction

Extrusive--A descriptive modifier for an igneolls rock that was erupted onto the surface of the earth. Extrusive describes rocks, for example. that comprise lava flows, volcanic breccia, and tuff

Fabric--Thc spatial and geometric arrangement, size, and shape of crystals, rock and mineral components, and structures that characterize a rock mass

Fault--A break, or fracture, along which rocks on one side have moved relative to rocks on the other side

Fault zone--A composite zone of displacement across rock masses characterized by numerous faults and fractures each generally parallel to the trend of the zone of displacement. The zone can be a few centimeters wide, or as much as 0.6 mi (I km) wide in the Helena region. Amounts and directions of displacement can differ among rocks and faults within the zone as a result of different directions or extents of movement with time along the faults comprising the zone

Fracture--A break or rupture across a rock mass. As used in this report, a rock mass is broken but not displaced signi fican1 ly across a fracture, in contrast to a fault across which adjacent rock masses have moved into juxtaposition

Gaining stream--A stream that gains water from inflow of ground water through the streambed

High grade--A general descriptor for the extent to which a rock has been metamorphosed under conditions of high temperature and pressure. As used i.n this report, high grade is synonymous with high rank

Hydraulic conductivity--A measure of the ability of rock or sediment to transmit a measured volume of fluid through a measured area during a unit of time

Igneous--A rock or mineral that has crystallized from molten material, such as a magma

Ioterval--An unspecified thickness of strati tied rock that contains several beds, laminae, sets of cross beds, OT combinations of bedding types, which have common lithologic or hydrogeologic characteristics. An interval is part of a mapped geologic unit (pI. I). The ternl is used in this report to distinguish descriptively between an

DEFINITIONS 39

individual bed, lamina, or a cross-bed set, and a contiguous succession of several such beds or bedding types

Interval of dissoJution--An unspecified thickness of sedimentary rock, geoerally a carbonate rock, that includes several beds, laminae, or sets of cross beds, which together have undergone dissolution of chemical minerals, such as carbonates, silicates, and sulfates. An interval of dissolution can include several solution forms such as mold.ic porosity, in which selected fossil fragments, carbonate clasts, or ooid cores are dissolved to produce voids; intercrystal and intracrys(al porosity; solution openings along fractures or bedding surfaces in the rock interval~ and solution vugs, cavities, or even caves within beds or across several beds, sets of laminae, or combinations of bedding types

Intrusive--The characteristic of a rock type or rock body emplaced as molten material, then crystallizing, within a preexisting rock

Losing stream--A stream that loses water to ground water by outflow through tbe streambed. Losing streams can be connected to the ground­water system by a continuous saturated zone or can be disconnected from the ground-water system by an unsaturated zone

Low grade--A general descriptor for the extent to which a rock has been metamorphosed under conditions of increased, but low to moderate temperarure and pressure. As used in this report, low grade is synonymous with low rank

Lower plate--The body of rock beneath, or footwall of, a fault 1hat is, or was originally, inclined at a low angle to the surface of the Earth

Metamorphosed--The quality of a rock in which the original minerals, fabric and structure, and, in some cases, chemistry have changed to different forms as a result of the rock being subject to increased temperatures and pressures below the surface zone of weathering and cementation

Monzonite--A crystalline igneous intrusive rock containing nearly equal amounts of potassium (alkali) feldspar and plagioclase (sodium and calcium) feldspar, augite as the principal mafic mineral, and usually a small amount or quartz .

.so Hydrology ortbe Helena Ar-ea .Bad rock. West-Cl"1l1rol MQntana, 1993-98

Monzonite of the Scratchgravel Hills grades into quartz monzonite (see definition)

Normal fault--A fault that generally dips at a high angle to the surface of the Earth and along which rocks above the dipping fault surface moved down relative to rocks below the dipping surface

Particulate waste--Particles or flocculent accumulations of human, animal, plant, or industrial organic waste; minerals such as clay or rock fragments derived from the walls of a bore hole, drain field, or stream; or a combillation of these

Permeabilify--A measure of the ability of a rock or sediment to transmit fluid

Pluton--An igneous intrusion emplaced, generally at increased temperatures, into surrounding rock. Used in this report or to refer to a mass of plutonic rock without regard to size or composition

Potosity--The space, or interstices, within a rock or sediment. Expressed quantitatively as the ratio of the volume of interstices to the total volume of the rock or sc.diment. Porosity can be (a) primary, that is, voids included in the rock or sediment when it was fonned, or (b) secondary. voids developed by dissolution of minerals or cement in the rock; by joints, fractures, or deformation of the rock, or by a combination of these

Potential evaporation-The evaporation expected trom a natural water surface or very wet soil

Quartz monzonite--A crystalline igneous intrusive rock containing 10 to 20 percent quartz crystals, potassium (alkali) feldspar comprising about 35-65 percent of the tolal feldspar with plagioclase feldspar comprising the remainder of the total feldspar, and biotite, hornblende, and some augite comprising the mafic minerals. Known also as quartz-bearing monzonite or granodiorite

Quartzite--Hard. dense sedimentary rock, composed of sand-sized particles, dominantly quartz which has undergone regional low-grade metamorphism. Stratification. sedimentary structures, and other internal sedimentary features are well preserved through the metamorphism

Recharge--The addition of water to the zone of saturation; also, the amount of water added

Residuum--The residue at the surface produced by the weathering of underlying bedrock or deposits. As used in this report, includes residual rock fragments and sand-sized particles as well as si 11- and clay-sized particles

Seasonal--Hydrologic variation during the seasons of a year. such as high surface-water runoff in the spring and low surface-water flow in the autumn and early winter

Secular--A progressive process lasting for an unspecified long period of time, commonly several years; nuctuations of limited duration can temporarily reverse the progressive process

Siliciclastic--A sedimentary rock composed of grains of silicate minerals such as quartz and feldspar. Grains of carbonate or evaporite minerals are uncommon in the rock, but these chemically derived minerals can be the cement in the siliciclastic rock

Siltite--Hard. dense sedimentary rock, composed of silt-sized grains, which has undergone regional low-grdde metamorphism. Stratification, sedimentary structures, and other internal sedimentary features are well preserved through the low-grade metamorphism

Splay--One of a series of faults that diverges from a major fault or fault zone. The word is also used as a verb to denote the act, or visual appearance in map view. of a fault diverging as a structural entity from a major fault or fault zone

Stock--An igneous intrusive body, generally discordant in preexisting rocks, that encompasses an area of less than 40 mi2 (100 km 2) in surface exposure; similar to a batholith, but much smaller in exposed surface area

Strike-slip fault--A vertical or nearly vertical fault along which rocks on one side have moved horizontally with respect to rocks on the opposite side

SynC\ine--A concave upward fold whose limbs are inclined generally downward toward the center;

the youngest beds are usually in the center of the fold

Synclinorium--A composite synclinal structure of regional extent, composed of lesser folds

Tectonics--A study of the interrelation of folds, faults and fault systems, plutons, and systems of defonnation of a large area or region

Telescope--The relative apparent shortening of a sequence of crustal rocks produced when one length of the rocks moves on one or more thrust faults over the once-contiguous equivalent rocks that are now beneath the thrust fault or taults

Thrust fault--A break, or fault. in rocks that is inclined at an angle of 450 or less relative to the surface of the Earth. Rocks above the break have moved upward and generally horizontally with respect to rocks beneath the break

Tuff--A consolidated rock composed mainly of fragments derived from volcanic eruptions, including ash, fragmeots of pumice . Generally, less than 25 percent of the volcanic fragments are larger than 2.5 in . (64 O1m) ; some volcanic tuff contains sediment, such as sand, silt, clay and pebbles, transported by water, and volcanic ash and fragments reworked by moving water

Tuffbreccia--A consolidated volcauic rock composed of angular fragments of volcanic debris, including bombs. lumps of scoria. cinders of pumice. lapilli, and blocks of congealed lava usually, but not always, in a matrix of volcanic ash

Upper plate--The body of rock above. or hanging wall of, a fault thaL is, or was originally, inclined at a low angle to the Earth's surFace

Welded tllff--A consolidated rock composed of volcanic mineral crystals, pumice fragments, and small congealed volcanic glass fragments in a matrix of volcanic glass shards, welded together by heat, entrapped and escaping volcanic gases, and weight of the overlying volcanic materials

DEFINITIONS 41

LOCATION-NUMBERING SYSTEM

The location of wells is designated by a location number, which is based on the rectangular system for the subdivision of public lands. The number consists of as many as 14 characters and is assigned according to the location of a site within a given township, range, and section. The first three characters specify the township and its relative positioll north (N) of the Mon­tana Base line. The next three characters specify the range and its relative position west (W) of the Montana Principal Meridian. The next two characters indicate the section, and the next one to four characters indicate the position of the site within the section. The first

Location-numbering system.

42 H~'drology of the Helena Arca B.dTock, West-Ceotnl Montana. 1993-98

letter denotes the quarter section (160-acre tract); the second letter denotes the quarter-quarter section (40-acre tract); the third letter denotes tbe quarter­quarter-quarter section (I O-acre tract); and the fourth letter denotes the qual1er-quarter-qllarter-quarter section (2.S-acre tract). These lettered subdivisions of the section are indicated as A, B, C. and D in a counterclockwise direction, beginning in the north­east quadrant. The last two characters fonn a sequence number based on tbe order that a site was inventoried in that tract. For example, location number II N03W 18BBACO I represems lhe first well invento­ried in the SW1I4NEII4NWI J4NW1 J4Sec. 18, T. 11 N., R. 3 W.

Weil 11N03W188BAC01

DATA

DATA 43

t ::;:: .< C

o .., <:> 0-~ <:>

.... 1; :c '" ro ~ co

~ '" ., =' ,., Q.

"' <:> "-r ~

£ h '" ~ ., !:. s: o ,. ;; ::I

."' 'D

"'" 'f 'D

""

Tab

le 211. G

eologic and inferred hydrologic characteristics of H

elena area bedrock

I [)escrip\ions and inferences are based On

d~laikd c"aminalion orlhe rocks on outcrop. drill cunings, and carL'S; on exam

inallon oflh~ rock, under the micro,cope: and on com

parison of observed rock characteristics 10 dcscriplions of nuid produclion from

drilling and well records.

Qualitative descriptions low

, moderate. and high applied to penneability and hydraulic conductiv;ly or H

elena area bedrock units can h~, interpreted in approxim

ate general terms using table 2b (Freeze and C

herry. 1989: annotations from the current ~Iudy).

Values on lObI<: 2a cannot be applied for detailed

quantilalive cvalu~tion at a specific sile wilhoullaboralO

ry IeslS or the propenics of rocks drilled at the site]

Geologic characteristics

[nferred bydrologic characteristics Inferred hydrologic responses In study area to

Geologic m

ap G

enerali7.ed G

eneralized P

rotracted unit and m

ap distribution in

rock P

arallel to P

erpendicular to W

hrrr fractured

Recharge

withdraw

al of P

rotracted fluId sym

bol study area

type 5t ratification

stratification or faulted

ground water

waste disposal

CpL 1)

Pliocene(?) and

Northem

part of Interbedded

Low

to moderdle

Low

to moderate

Locally m

oderate M

oderale to rapid M

oderate to rapid I nterconnecled

Miocene

western m

oun-conglom

erate. porosity and

porosity and hydraulic

recharge by draw

down jfw

atCf

fractures can serve as sedim

entary tains and pos-

sandstone. si It-penneability, bUI

penneabililY,

conductivity In

cpisodic inlluenl is not sustained by

conduits for unim-

rocks sible thin

stone, and tulT; highly variable

but vertically fracrured

seepage or sea-recharge; possible

pedcd contaminant

remnants in

minor m

ud-w

ithin conglom-

variable within

conglomerate

sonal canal reduction o

f now

; adsorption and R

.M.s

southern par1 slone

crate and sand-conglom

erate and sandslone

leakage where

porosity and retenl ion o

f o

f North H

ills stone intervals:

and sandstonc i nlerva Is: clay

conglomerate and

penneability by conlam

inanls by area

moderate

intervals; low

derived from

sandstone heds secondary grow

th clays and on

porosity and low

penneabl1ity alteration o

f tuff are exposed at the

and movem

ent of

fracturc faces; swell-

penneability in acro~s IU

tTbeds

can seal surface; lim

ited clay in interstices:

ing of som

e clays by tuffbeds

and alternating fract ures and

episodic recharge overall w

ater-level w

elling; once I:on-rock types

faulls; low to

through fractures decline likely on a

laminated, likely

moderate hydrau-

in ruff sequences secular basis w

ith slow

10 recover by lic conductivity

protracted with-

nushing wilh fresh

.in fractured tuff draw

aJ w

ater

Oligocene

South Hills,

Rhyolile now

s L

ow porosity and

Low

porosity and Fluid flow

and L

imited episodic

Moderate to rapid

In terconnecled volcanic

Montana ('ily

and inrrusive penneability in

perlneability in storage prim

arily rccharge Ihrough

drawdow

n: water

frnctures can serve as rocks; m

ay area; southern

bodies, minor

rhyolile where

rhyolite where

in fractures and fractures; ~

Iow

production likely conduits for unim

-include som

e part o

f western

tuft: breccia, not fractured;

not fractured: laulls: low

to recovery aftcr

seasonal and cyclic: peded contam

inant rocks o

f possi-m

ountains and tuffaceous

moderate

moderale

moderale fluid

withdraw

al overall w

ater-level flow

: fracturc open-ble late

sandstone; un it porosilY

and low

porosity but low

!low through

decline likely on a ings can be reduced

Eocene age in

Q;vt is m

ainly penneability in

penneability in fT3l:IU

res secular basis w

ith or sealed by accum

u-the southw

est stratified rulT

breccia and tuf-breccia and

protracted Im

ion of particulate

part of the

and thin inter-faceolls

IUffaceous

wilhdraw

al w

aste m

ap area beds o

f sand-sandstonc

sandstone SLOne and

Q;v, Q

;vt pebble con-glom

erate

Tab

le 2a. G

eologic and inferred hydrologic characteristics of H

elena area bedrock (Continued)

Geologic' C

'hll.racterislics In

ferred hydrologic cb

aracteristics In

ferred hydrologic responses in study area to

Geologic-

map

G

eneralized

P

rotracted

u

nit aD

d map

d

istribu

tion

in G

eneralized

P

arallel to P

crpendiC'ular to

Wh

ere fractured

R

echarg

e w

ithd

rawal o

f P

rotracted

fluid sym

bol stu

dy

Hrea

rock

type stratIfication

SI ratlfiCH

t ion o

r faulted g

rou

nd

waler

waste dlspo..~ul

(pI. 1)

Oli~ocene sedi-

Spokane

tnterbedded sand· M

oderate to high Low

to moderate

Locally m

oderate L

ow to m

oder-M

oderate to rapid Interconnected

mcntary rocks;

Bench. SO

Ulh

stone, conglom.

porosity nnd low

porosity and hydraulic

ate. locally draw

down;

fractures can serve m

ay include H

ills, Ilnd

erate. and miT;

to moderate

permeabitity

conductivity in high, recharge

possible reduction of

as conduits for som

c rocks of

East H

elena m

inor cilfbon-perm

eability, but w

ithin sandstone fractured

by episodic porosity ond perm

e-unim

peded possible

area aceous ,iltstone

h.ighJy variable and $om

e con· $and~tone and

innuent seep-ability by sw

elling contam

inant Ilow;

Eocene age

and mudstone

laterally in glom

erate inter-conglom

erate age or sea-

and movem

ent of

adsorption and al base

sandstone and vals:

low

intervals; clay sonall:anal

clay; overall water-

retention of

conglomerate

permeability

deri ved from

leakage where

level dccline likely contaminant~ by

G:S

intervals;

across IU ff beds

alteration of turr sand~tone and

on a secular bn~is clays and on

moderate to low

and interbedded

can seal fractures conglom

eratc w

ith protracted with-

fracture faces; porosity and low

rock typcs thai

and faull~; low

beds are draw

al sw

elling of ;;om

e perm

eability in contain silt.

nuid now in

exposed at the clays by w

etting: lU

ff and mud-

clay. and tuff fracru red luff

surface once contam

i-stone beds

naled. likely slow

to recover by nush-ing w

ith fresh w

ater

Eocene

Western m

oun-A

ndesitic and L

ow porosity and

Low

porosity and Fluid {low

and L

imited episodic

Moderate to rapid

Int.::rconnected volcanic roeks

tains, includ· basaltic now

s. perm

eability perm

eability storage prim

a. recharge

drawdow

n in fractures can serve

ing Mullan

breccia. and w

here not w

here not rily in fracrures

I hrough frac· fractures; w

ater as condu its [or

Eov Pass areas

intrusive fractured; can

fraclured and [au Its; low

to tures: slow

production likely

unimpeded

and Dread-

bodies have intervals o

f m

oderate fluid recovery after

seasonal and cyclic: contam

inant now:

noughl Hill

moderate

flow lhrough

withdraw

al overall w

ater-level fracture openings

permeability at

fractures decline likely on a

can be reduced or bases or tops o

f secular basis w

ith sealed by accum

u-volcanic noli's

protracted latioo ofparliculatc

wi[hdraw

al w

aste

Cretaceous

Western

Quanz m

onzo· N

ot stratified; local N

ot stratified; local Fluid flow

and L

imited episodic

Moderate draw

down;

Interconnected intrusive

mountains,

nile. monzonite.

alignment of

alignment of m

in· storage

rccharge w

ater production fractures can serve

rocks. S

eratch-granite and ~

omc

minerals can

erals can produce prim

arily in through frac·

seasoDal and cyclic;

as conduits for m

ainly gravel H

ills. m

afic intrusive produce planar

planar and linear fractu res and

rures: slow

overall waler-level

unimpeded

granitic and South

rocks and linear

fabrics; low

faults; low to

recovery a fler decline likely on a

contaminant tlow

; ..:

r-lills fabrics; low

porosity and

moderate tluid

wi.thdraw

al secular basis w

ith fracrure open i ngs

:0-: K

g porosity and

pemleability

flow through

protracted cao be redltced or

t;t:l r

permeability

unless weathered

fractures w

ithdrawal

sealed by accumu·

tTl ....

unless weathered

and fractured lation o

f particulme

"' and fractured

contaminants

.... ~

.... T

able 2a. G

eologic and inferred hydrologic characteristics of H

elena area bedrock (Continued)

'" :z: '"", Q

. ... o 0" ~ o ... ;;

... :c '" r> " " ;..-..., .. ., I:I:l

a. ... o " F ~

'" ~ n ... :. ., '" ~ o ~

'" " !" "" '>C

..... ~

co

Geologic characteristics

Geologic m

ap G

eneralized unit an

d m

ap distribution in

Generalized

symbol

study area rock type

(pI. 1)

Elkhorn

Western m

oun-A

ndesitic M

ounmins

tains; South volcanic rocks;

Volcanics

Hills, includ-

ash flow tuffs:

ing Prickly shallow

intru· K

ev Pear C

reek sive rocks. and

and Clancy

minor sedim

en-C

reek drain-w

ry rocks; ages

mainly w

ell indurated and locally m

etamor-

phosed

Upper and

Western m

oun-M

udstone. L

ower

tains, inc Iud· siltstone, thin

Cretaceous

ing Dog

sandSlone units; sedim

entary C

reek, Uncle

some conglom

-rocks:

George

era Ie (lnd vcry C

olorado C

reek, and thin tuff beds;

Group and

tributaries 0 r Jocfllly m

clamO

f-K

ootenai T

enmilc

phost:d adjacent Form

ation: C

reek: North

10 younger locally

Hills. north-

intrusive nodies includes

cast part: and Slim

Sam

South Hills

Formation

Kck

Inferred hydrologic characteristics

Parallel to

Perpendicular to

Where fractured

stratificatlon sl ratification

or faulted

Generally low

G

enerally low

Fluid now and

porosity ami

pernlenbility storage

permeability in

across interned· prim

ari Iy in frac· volcanic flow

s ded units and

tures and f<lulls: and m

ost weldcd

within volcanic

low to m

oderate ash flow

IUITs;

flows and shal-

fluid flow

low to locally

low intnlsivc

through m

oderate poros· rocks

fractures iry and low

per-m

eability in ~ome

thin sedimel1lary

units

Low

to moderate

Low

permeability

Fractures and porosity ~nd low

and hydraulic

faults increase perm

eability in conductivity

permeability and

mudstone and

across interbed-hydraulic

si Ilstone inter· ded m

ud~tone

conduct ivity vals: low

to mod·

and sandstone craie porosity and perm

eability. latcrally V

(lrl-able, in sandstone and som

e conglom

erate intervals; low

porosity and perm

eability in all rock types w

here m

etamorphosed

Inferred hydrologic responses in sludy area to

Protracted

Recharge

witbdraw

al of P

rotracted fluid

ground water

waste disposal

---

Lim

ited episodic M

oderate to rapid Interconnecled

recharge drnw

down; w

ater fractures can serve

through fTOC-producti()n

as conduits for ture,,; slow

seasonal and

unimpcded

recovery aner cyclic: overall

contaminant 110w

; w

ithdrawal

water·level decline

fracrure openings likely on a secular

can be reduced or basis w

ith protracted sealed by accum

u· w

ithdrawal

lation of particulate

contaminants

Lim

ited episodic M

oderate drawdow

n Interconnected

recharge if w

ell is complcted

fractures can serve m

ainly through in

a~ conduit'S for fractures: slow

sandstone or

unimpeded

recovery a Iter conglom

erate: contam

inant flow;

protracted m

oderate to rapid rractures and inter-

withdraw

al draw

down if

granular pore space com

pletion is in can be reduced or

fractured mudstone:

sealed by aeeumu-

precipitation of

lation of particulate

carbonate and w

aste authigenic grow

th or m

ovement o

f clay during w

ithdrawal

cnn reduce porosity and perm

eabiliry in pO

Tes: overall water-

level decline likely on a secular basis w

ith prOITacted

withdraw

al

-i ;;. C

I) r rrl ... .. .... --'l

Tab

le 2a. G

eologic and inferred hydrologic characteristics of H

elena area bedrock (Continued)

Geologic charactl'ristics

Inferred h ~'drologic characteristics

Geologic m

ap G

eneralized unit lind m

ap distribution in

Generalized

Parallel to

Perp

cnd

icular 10

Wh

ere fractLlred

symbol

study area rock type

stratification stratillcation

or faulted

(pl. I)

Jurdssic sedi-W

estern mO

un-M

udstone. G

enemlly low

L

ow to m

oderatc Fracnlres enhance

mentary rocks:

lains, SOlllh

siltstone. and porosity and

poro>iry and dissolution,

Morrison For-

Hills, and

thin unils of line-

permeabilil)';

pcnneabilily hydraulic con-

malion and

nonheast pan grained sand-

low pennea..,ili!y

wilhin 5,lOeI-

duclivily, and E

llis Group

of N

orth Hills

stOn<: wilh m

inor w

here melam

or-stone: low

per-reservoir slorage

carbonaceous phosed

meabilityacross

wilhill som

e car-Jm

e shale and

mudstone and

bonate b<!ds and lim

estone beds; inlerbedded

in some m

ud-locally m

etamor-

rock Iypes stone inlervals

phose<! where

inlruded hy igne-ou~ rocks

Permian lind

South Hills and

Silica-and G

e·nerally low

Low

to locally Fractures enhance

Pennsylv8-northeast pan

caJt;ium carbon-

porosity and m

oderate dis~olulion.

nian sedimen-

of N

orth Hills

nte-cemented

penlleability: porosil>' and

hydraulic con-tary rocks:

sandstone: thin locally m

oderale penne<tbilily

ducrivilY, and

Phosphoria.

limestone.

porosily in w

ilhin caroontlle reservoir storage

Quadrant. and

siltstone, and intervals o

f and sandslone

wilhin som

e car-A

msden

dolostone beds; dissolution in

intervals; low

bonate beds and F

onnations som

e thin chert lim

eslone and penneability

in mudslone

in upper part calcareous

across mud~tonc

intervals P

lPqa

sandSlone beds and quartz-cem

ented sandstone intervals

Inferred

hydrologic responses in study area to

Pro

tracted

Rerhllrgc

withdrllw

al of

Protracted fluid

gro

un

d \Y

ater w

aste disposal

----

Lim

ited episodic M

oderate drawdow

n Illterconnected

recharge in sandstone units

fracturcs can serve m

ainly through and in fractured

as condu i IS ror fractures; slow

m

udstone; unimped~d

recovcry after precipitation o

r conlam

inant flow:

witlll..lraw

al caroonnte and

fraclUres and inler-

aUlhigenic grow

lh or granular pore space

movem

ent of

can be reduced or clay in pores

sealed by accumu-

during withdraw

al lation of particulate

can reduc\: porosi I)' w

aste and penneabilily; overall w

ater-level decline likely on a secular basis w

ith prolracled w

ithdrawal

Lim

ited episodic M

oderale 10 slow

Inlerconnectecl recharge

drawdow

n; fractures can serve

mainly through

withdraw

al may

as conduits for fraclures; slow

induce reduction o

r unim

peded con-recovery 11 fter

porosity and lam

in ant flow;

withdraw

al perm

eability by fractures and inter-

precipitation of

granular pore space calcium

carbonate: can be reduced or

overall water-level

sealed by decline likely on a

accumulation of

secular basis with

particulate waste

protractcd with-

drawal

t T

able 2a.

Geologic and inferred hydrologic characteristics o

f Helena area bedrock (C

on

tinu

ed)

::r: '"" Co .., ., 0-~ ::>

.... ;. ... ::t: ... ;; ::>

" >-., .., .. 1:1) ... C

o ., <:> n v~

~

a n '" ;; ., ~

~

<:> ::> iO =

... 'D

If 'D

Qo

Geologic characterIstics

Geologic m

ap

Generalized

unit and

map

distribution In G

eneralized sym

bol rock type

(pI. I) stu

dy

area

Big S

no

wy

N

ortheast pan

M

udstone. G

roup: o

f No

nh

Hills

siltstone. and

H

eath, Otter,

thin limestolle

and Kibbey

bed$; calcareous F

on

natio

ns

sandstone; local dolostone

Mb

breccia near base

Madison

South H

ills, T

hick bedded G

roup: northeast p

an

limC

5tonc; thin M

ission o

f North

bedded lime-

Can

yo

n

Hills,an

d

stone with so

me

Lim

estone locally in cen-

calcareous and

tral part of

siltstone in lower

LO

<Igepole w

esLern

part; metam

or-L

imestone

mountains

phoscd to calc-

silicate rock M

ml

whcre intruded

by Cretaceous

igneous rocks

Inferred hydrologic characteristics

Parallel to

Perp

end

icular to

Wh

ere fractured stratificatio n

stratification o

r faulted

Generally lo

w

Low

penneability P

enneability is porosity and

across mudstone

increased by

p

enn

eabi I ity;

intervals except fractures in all

Ivcally moderate

where fractured,

rock types but porosity an

d

and then moder-

particularly in pem

leability in alc at boundaries

mudstone

brecc ia near base

wiLh sandstone o

r intervals

limestone

Moderate porosity,

Discontinuous low

F

racrures p

enn

eability

, and to m

oderate sign i ficanL

ly hydraulic

porosity and enhance

conductivity in pcnneability;

dissolution, intervals o

f locally m

oderate penneability,

dissolution; low

to high pen

ne-

and hydraulic porosiry an

d

ability and conductiviry

pcnneability hydraulic con-

throughout the w

here meL

amor·

ductivity in rocks; fractures

phosed areas o

f dissolu-are likely the

tion m

ain source of

penneability w

hcre un

it is m

etamorphosed

Inferred hydrologic responses in study area to

Pro

tracted

Recharge

withdraw

al of

Pro

tracted fluid

waste disposal

gro

un

d w

ater

Lim

ited episodic M

oderate drawdow

n Interconnected

recharge if com

pletion is in fractures clln so;:rvo;:

mainly through

fractured mudstone;

as conduits for fractures;

or carbonate beds

unimpeded

recovery slow

with secondary dis-

contaminant now

; in m

udstone solution porosity;

fractures and

inter-intervals w

here overall w

atcr-Icvcl g

ranu

lar pore space nO

I densely decline on a secu

lar can be reduced o

r fractured; slow

basis likcly in m

ud-sealed by accum

u-recovery after

stone units with pro-

lation ofp

anicu

late w

ithdrawal

tracted withdraw

al w

aste

Moderate to

Moderatc drnw

down;

Interconnected rapid recovery,

can be rapid in inter-fm

ctures can serve but strongly

va Is of d issolut ion:

as conduits for episodic; slo

w

mO

<lerate to rapid

unimpeded

recovcry after draw

down w

here contam

inant flow;

protracted m

elamorphosed

fracturcs and

imcr-

withdraw

al an

d fracrured

granu lar pore space can bc reduced o

r sealed b

yaccu

mu

-lation o

f part iculate w

aste; waSLe w

ater o

f low pH

can induce dis-solution o

f the carbonate m

inerals

Tab

le 2a. G

eologic and inferred hydrologic characteristics of H

elena area bedrock (Continued)

Geologic characteristics

Inferred hydrologic characteristics In

ferred hydrologic responses in study area to

Geologic m

ap G

eneralized P

rotracted

u

oit an

d m

ap distribution in

Generalized

Parallel to

Perp

end

icular to

Wh

ere fractured R

echarge w

ithdrawal o

f P

rotracted

fluid sym

bol study area

rock typ

e stratification

stratification o

r faulted g

rou

nd

wa"ter

waste disposal

(pI. 1)

nlrec F

orks N

ortheast pan

T

hick

bedded to L

ow porosity and

Discontinuous low

D

is50lUlion o

f M

oderale recov-S

low to m

oderate 1 nterconnccted

and o

f North

laminated

permeability

porosity and carbonate

ery mainly

drawdow

n. locally fractures can serve

Jefferson H

ills; locally dolostone and

with low

penncability; can

minerals along

through frac-rapid in intervals

as conduits for F

ormations.

in central pan

m

inor very thin hydraulic

be enhanced and adjacent to

tures; recharge o

r dissolution; unim

peded undivided

; o

f west em

lim

estone; conductivity

; across bedding by

fractures likely episodic; slow

m

oderale lO rapid

contaminant Ilow

; as m

apped m

ountains; m

udslOne and

paning parallel dissolul ion o

f accounls for

recovery after draw

down w

here fractures and inl"er-

includes S

oulh Hills

carbonaceous to stralification

carbonate m

uch of the

protracted m

ctamol1>

hosed granular pore space

some

mudstone in

can locally have m

inerals secondary poros-

withdraw

al and fractured;

can btl reduced or

Mississippian

uppermost part;

moderate

iry. penneabil-overall w

ater-level sealed b

yaccu

mu

-strata altlle

locally hydraulic

ity, and decline likely on a

lalion of paniculate

top m

etamorphosed

conductivity; hydraulic con-

secular basis with

waste; infiltrating

to calc-silicate low

porosity and duC

livity of the

prolracted with

-fluids o

f low pH

D

lj rock adjacent to

permeability

carbonate beds draw

al can induce d

iswlu

-C

retaceous inlru-w

here melam

or-and m

udslone lion o

f the carbon-sive roeks

phosed ate m

inerals

Upper and

Western m

oun-T

hick to thin L

ow porosity and

Discontinuous low

D

issolution of

Lim

ited episodic M

oderate drawdow

n Interconnected

Middle

tains in no

nh

-bedded

permeability in

porosity and per-carhonate

recharge in intervills o

f disso-fractures can serve

Cam

brian em

tributaries lim

estone, with

carbonate rocks; m

eability; can be m

inerals along m

ainly through lU

lion; moderate to

as conduits for carbonatc

of T

en mile

limestone

moderate

increased across and adjacent to

fractures; rapid draw

down

unimpeded

rock~:

Creek; S

outh pebble conglom

-porosity. m

ainly bedding by

fractures likely locally m

oder-w

here fractured: contam

inant now;

Hasm

ark. Pil-

Hills; easl o

f crate and dolo-

secondary, and dissolution o

f accounts for

ate recharge overall w

ater-level fractures and inter-

grim, P

ark.

North H

ills stone at top;

penlleability in carbonate

much o

f the w

here frac-decline likely on a

granular pore space and M

eagher m

udstone al cen-areas o

f dissolu-

minerals

secondary poros-tures connect

secular basis with

can be reduced or

Fonnations

ter and as pan

-tion; low

perme-

ity. permeabil-

units contain-

protracted with

-sealed by accurnu-

ings in lower

anililY in m

ud-ity, and

ing dissolution draw

al lation o

fpan

ieulale

Be

part; locally stone intervals;

hydraulic con-

cavities and w

aste; infiltrating m

etamorpbosed

low o

r no poros-ductivity o

r the vugs; gener-

fluids of low

pH

lO calcsilicate

ity and perme-

carbonare beds ally slow

, but can ioduce dissolu-

rock ability w

here and m

udstone locally

tion of the carbon-

metam

orphosed m

oderale ate m

inerals recovery; slow

recovery after

-l protracled

;;.. w

ithdrawal

I;Il r t'1 t"" EO

.... \CO

g: T

able 2a. G

eologic and interred

hydrologic characterislics or Helen

a area bedrock (Co

ntin

ued

)

::c .... a­d ;' ~ o ..., ::r

~

;x .. ;;" ,. .. >-., "' .. ~

.. c.

., " " 1'" ~

a 'j' (') ... " ; ~

" :I ., ::I

!" '¢

,., 'r' 'C

Q

C

Geologic characteristics

Gcologic m

ap

Generalized

un

it nn

d m

ap

distribulion in

Generalized

symbol

rock type (pl. \)

study area

Middle

Western m

oun· U

pper part: C

ambrian

lains in north· m

icaceous clastic

em tributaries

mudstone and

rocks: o

fTen

mi!e

siltstone beds W

olsey C

reek; Soulh

with local thin

Shale and

H ills: east o

f lim

estone beds, F

lathead N

orth Hills

Lo

wer part:

Fonnation

quartz-cem

ented £

cl

sandstone and thin co

ng

lom

er-ate w

ith mud·

stone pan

ing

s

rntrusive rocks: ScratcilgT

Ilvei M

edium to

Lale

Hills; w

est-coarsely

Pro

tcrow

ic em

mounlains

crystalline in low

er reach gabbro and

Z9 o

f Scvenm

ilc diorite

Creek

Inferred hyd rologic ch a racted sties

Parallel to

Perp

end

icular to

Wh

ere fractured

sl ratification

stratification o

r faulted

Low

porosity and L

ow porosilY

and F

luid 110w and

penneability; pernleabi I ity:

storage prima-

where nO

I frac· w

here not frac· rily in fraclures

rurcd low hydrau-

lured low hydrau-

and faults: low to

lic conductivity lic conduclivity

moderate nuid

tlow

thro

ug

h

fractures

Generally no

Generally low

F

luid flow and

Slratitication but

roro

sity and

storage prima-

can have parallel pcnnenbility; low

rily in fractures;

alignment or

hydraulic con-generally low

platy and labular

ductivity; may

fluid no

w

minerals;

have moderate

through generally low

penneability

fracturcs porosily and

where deeply

penneabilily; w

eathered low

hydraulic conductivity; m

ay have m

oderate pcnneability w

here deeply w

cathered

Inferred

bydrologic responses In study area to

Pro

trncted

R

echarg

e w

ithd

rawal of

Pro

tracted fluid

waste disposal

gro

un

d w

aler

Likely slow

M

oderale drawdow

n Interconnected

recharge o

f water in

fracture~ can serve through frae·

fractu res; with-

as conduits for turl's;

drawal can

unimpeded

episodic: slow

produce elevated

contaminant tlow~

recovery after precipitation o

f fraclures and inter-

wilhdraw

al iron oxides: overall

granular pore space

water·level decline

can be reduced or

likely on a secular sealed

by accumu-

basis with pro-

lation of particulate

tracted withdraw

al w

aste

Areally lim

ited M

oderate drawdow

n Interconnected

outcrop nrea; o

fwaler in

fractures can serve likely very

fraclllres; overall as conduits for lim

· slow

recharge d

ttline on a

iled contaminant

Ihrough frac-secular basis w

ith now

tures;

protracted with-

episodic; slow

drawnl; w

ilhdrawal

recovery a fler can

induce elevated w

ithdrawal

precipitation of

iron oxides

Tab

le 2a. G

eologic and illIerred hydrologic characteristics of H

elena area bedrock (Continued)

Geologic characteristics

Inl'erred hydrologic characteristics In

ferred hydrologic responses in study area to

Geologic m

ap

Gcne-raliled

Pro

tracted

unit and map

distribution in

Generalized

Parallel to

Perp

end

icular to

Wh

ere fractured

R

echarge w

ithd

rawal o

f P

rotracted

fluid sym

bol study area

rock type stratification

~tratiJjcation o

r fllulted g

rou

nd

watcr

waste di~posal

(pI. I) -

---

Bonner

Weslcrn m

oun· M

edium-

and L

ow porosily and

Low

porosity and Fluid now

and R

echarge M

oderate drawdow

n I nterconnccled

Quartzile

tains includ· coarse-gra i ncd

penneability perm

eabi I i ty storage

cpisodic, o

f water in

fraclures can serve lllg upper

quartzile; ~ome

wh

ae nOI frac-

where not frae

-prim

arily in frac· m

ainly through fraclures; overall

as conduits for Y

bo

IIi bU

[aries of

fine pebbles; lured; local m

od-lured; low

lures and tau Its;

fraclures; likely w

ater-Ievcl decl inc unim

pedcd D

og Crcck

argillile partings erate porosil),

hydraulic con-low

to moderale

slow recharge

likely on a secular contam

inant flow:

and Green-

where cem

enl has duclivily

Iluid now

b~sis wilh pro·

fractures and imer-

hom M

oun-

dissolved; low

Ihrough fraclures Iracted w

ithdrawal:

granular pore space lain area

hydraulic w

ithdrawal can

con be reduced or conductivity

induce devaled sealed

byaccumu·

precipilation of

lalion ofparliculate iron oxides

waste

Mounl S

hields W

estern moun-

lnlerbedde·d L

ow porosity and

Low

poro~ity H

ydraulic R

echarge M

oderate drawdow

n: Interconnecled

Fonnalion

lains, north-argillite and

permeability

and pennca-conductivity.

episodic, overall w

aler·level rractures can serve

central pan siltilc w

ilh Ihin w

here not frae-bility w

here not fluid !low

, m

ainly Ihrough dccline likely on n

as conduits for V

ms

intervals or

lured: low

rractured: low 10

and storage fractures: likely

secular basis with

unimpeded

quartzite: quartz-hydraulic con-

no hydraulic m

ainly in slow

recharge; protraclcd

contaminant flow

; ile beds line

ducliviry conductivilY

l'ral.:lure,; and

~Iow recovery

withdraw

al fraclures nnd inter-

upward

across som

e faullS after w

ith-granular pore space

inlo argilli[e slralilicarioll

drawnl

can be reduced or sealed by accum

u-lation ofparticulale w

asle

Shepard and W

eslern moull-

Quartzile;

Low

porosity and L

imited po rosity

Fluid now and

Recharge

Modcrate draw

down:

Interconllected S

nowslip F

or· tains_ eusl·

argillite and perm

eability and penneability

~Iorage mainly in

episodic. overall w

aler-Ievel Ipclures can

motions. undi·

cenlral and siltilc: som

e w

here nOI frac-

when: nOI rrac·

fractures and m

ainly through decline likely on a

provide conduils vided

nonh-central calcareous

tured: low

rured: low to no

some faulls

frrtctures; Ii.kcly secular basis w

ilh for unim

peded pans

nrgilJite and hydraulic C

OIl-

hydraul.ic slow

recharge prot.racted w

ith-contam

inant flow:

Yss

limeslone in

ductivily conductiviry

drawnl; can indllce

fracmres and inter-

Shepard across

precipitation of iron

granular pore space F

onnation siratificalion

oxides c~n be reduced or sealed byaccum

u-

-i lal ion o

f particulate ;!>

waste

o:l r :<1

'" '" U1

~

Tab

le 2a. Geologic and infetTed hydrologic characteristics o

f Helen!! area bedrock (C

ontinued)

:.: '-C

~

"\

2-o

"" '< o ...., :T ~

x "' iO ;:l

'" ~ "t

• II) t;:I

'" ~ "\

:> ,., '!" ~

~ Q

:! "t

!!.

3:: :> => ;; " ~ :g w

.b <lC

Gcologic ch

aracteristics

Geologic m

ap

unit and

map

sy

mb

ol

(pI. 1)

Helena and E

mpire

Formations.

undivided

Yh

e

Spokane Form

ation

Ys

General.ized

distrib

utio

n in

Gen

eralized

rock

typ

e stu

dy

area

Western m

oun-D

olomitic

wins, east-

argillite and centm

l and sihitc; lim

estone nonhern

and dolosto ne; pans;

argtHite and very

Scrntch-thin quanzite

gravel Hills;

beds in lowest

SOLith H

ills. pan~; locally

south of E

ast m

etamorpho

sed H

elena to calc·silicatc rock

Nonh H

ills: South H

ills east o

f H

elena

Argillite and sihitc w

ith ve ry thin lim

estone and quartz sandstone i.n uppennost and low

est part: recrystallized to

l:()arser gmins

by metam

or­phism

adjaccnt to intru

sivc bodics

Inferred

hy

dro

log

ic characteristics

Parallel to

stratification

Generally low

porosity and perm

eability

Low

porosity. perm

eahilityaml

hydraulic conductivity IV

here not I'mc­

tured; no porosity and perm

eability w

here strongly m

etamorphoscd

Perp

end

icular to

st ratifica tion

Porosity enhanced in carbonatc beds and som

e sand­Slone beds by dis­solution o

f carbonate and sil­ica; generally low

[lerm

ea hi lity ncross beds

Generally low

hydraulic conductivity w

here [lot frac­tured

Where fractu

red

or fault~d

Fluid now and

storage mainly in

fractures and som

e faults: ~ome dissol u­

tion of carbon­

ate beds adjacent to fraCl1.lfC

S

Porosity. l1uid stornge. and nuid flow

m

ainly in frnetures and ~ome raults

Inferred

hy

dro

log

ic respo

nses in sh

ldy

urea to

Rech.arge

Slow to m

oder­ate recovery

: episodic recharge m

ainly through fracrures; slow

recovery after w

ithdrawal

Recharge episodic_ m

ainly through fractures; likely slow

recharge: slow

recovt:ry afler w

ith­draw

al

Pro

tracted

with

draw

al of

gro

un

d w

ater

Moderate draw

down;

locally rapid in inlerval

~ or dissolu

­tion: m

oderate to rapid draw

down w

here m

etamorphosed

and fractured:

overall water-level

decline likely on;l sccular basis w

ith protracttd w

ith­draw

al

Slow to m

oderate draw

down; C

Dn be

rapid where unit is

strongly fractured; overall w

ater-level decline likely on it secular ba$is w

ith protracted w

ith­draw

al; withdraw

al can induce precipita. tion (If iron o,;,ides and sO

llie carbonate

Pro

tracted fluid

waste d

ispo

sal

Interconnected

frnctures can serve as conduits for unim

peded contam

inant flow;

Iractllrcs and inter· granular pore space can b

e reduced or sealed by accum

u­lation ofparticulate w

aste: infiltrating fluids o

f low pH

ran induce dissolu­tion o

f the carbon­ate m

incrals

Interconnected fracture

s can serve as conduits for unim

peded con<am

inant now;

fracturcs a.nd inter­granular pore space can be r.:duccd or sealed by accum

u· lation ofparticulate w

asle; infillration oftluids o

f low pH

can induce dis-"olu­tion o

f the carbon­ate m

inerols

;! o:l r l'l

'" .. '" .....

Tab

le 2a. G

eologic and inferred hydrologic characteristics of H

elena area bedrock (Continued)

Geologic characteristics

Geologic m

ap unit and m

ap

symbol

(pI. 1)

Greyson F

ormalion

Yg

Generalized

distrib

utio

n in

study area

North H

ills; SO

Ulh H

ills easlo

f H

elena

Generalized rock type

Sillile and argillite w

ith quanzilc in uppem

lost part

Inferred

hydrologic characteristics

Parallel to

strs rification

Low

porosity, penlleability. and hydraulic conduclivilY

w

here not frac­

lUred; can have

moderate poros­

ity and perme­

ability in $omc

quartzile beds ill upperm

ost part

Perp

end

icular to

stratification

Gencrally low

hydraulic conductivity w

here not frac­tured

Wh

ere fractured

o

r faulted

Porosity, fluid flow

, aod Auid

storage mainly in

fractures and som

e faults; dissolution o

f silica along fractures and faults in quartz­ite beds at the top can locally increase poros­ity, perm

eabil­ity, and hydraulic con­ductivity

lnferred

hydrologic responses in study area to

Recharge

Rccharg.e episodic, m

ainly through fractures; likely slow

recharge

Pro

tracted

wit.hdraw

al of

gro

un

d w

ater

Slow

to moderate

drawdow

n; can be m

pid where unit is

strongly fractured or in porous quartzite beds in upper part; overa 11 dec! ine I ike Iy on a secular basis w

ith protracted with­

drawal; w

ithdrawal

Pro

tracted fluid

waste disposal

I nterconnccted fractures can serve as conduits for unim

peded contam

inant !low:

fractures and i nter­granu lar pore space can be reduced or sealed by accum

u­lation o

f particulate can induce precipira-

waste

tion of iron oxides

and some carbon-

8te; slow recovery

after withdraw

al

Table 2b. Approximate range of values ofpenneability and hydraulic conductivity of the Helena area bedrock

[Abbreviations: k. permeability: K. hydraulic conductivilY: em. centimeter: s. second: m. meier: gal gallon; ft. foo t]

Rocks Unconsolidated

deposits

I 1 If

1,/1 ~ ~ 1 ., g E.g ~ I ~ 11 ~I :!y~ !~ 51

Modilied Irom Free2e and Cherry (1989. p. 29).

S4 Hydrology /If tbe Helena Area Bedrock. Wt'SI-Cenlral Montana, 1993-98

k (darey)

10 5

10 -3

10""

10 .8

~10 ' 10-10

_10 11

K (em/s)

10 2

10

10'1

10 '3

-10 1

K (m/s)

-10-6

- 10'

K (gal/day/It 2)

10

,0-3

10

Shaded area approximate inferred limits tor Helena area bedrock unils

Table 3. Records of wells

A second-line entry for a well indicates additional information.

Area: NH, North Hil!s~ SG. Scratchgravel Kills; WM, westem mountains; SH, South Hills.

Well number-numbering system lIsed for cross reference 10 wells ploUed on plate 2.

Location number--numbering syslem described in lex\.

Altitude ofland surface--in feel above sea level (detennined from U,S. Geological Survey 7.S-minute topographic maps).

Aquifer code--identifies producing geologic unil in well , with geologic age, and geologic unit on plate I thal includes the producing unit

Aquifer code ofprodudng Prod ueing geologic unit and (age)

unit

IIUALYM Alluvium (Quatern3ry)

123SDMS Oligocene sedimentary and volcanic rocks (Tel1iary)

124PLNC Eocene volcanic and intrusive rocks (Tertiary)

2118LDB Cretaceous intrusive rocks (Late Cretaceous)

21lSGVH Scratchgrovel Hills intrusive rocks (Lale Cretaceous)

211MRVL Marysville intrusive rocks (Late Cretaceous)

211ELKM Elkhorn Mountains volcanic rock~ (late Cretaceous)

220ELLS Ellis Group (Jurassi.c)

320PSLV Pennsylvanian System (Pennsylvanian)

320QDRN Quadrant Formation (Pennsylvanian)

33IMSNC Mis~ion Canyon Limeswne (Early Mississippian)

331 MDSN Madison Group (Early Mississippian)

)4lJFRS Jefferson Formation (Middle and Late Devonian)

371CMBR Cambrian System

371HMRK HasIDark formation (Middle and Late Cambrian)

374MGHR Meagher Fonnation (Middle Cambrian)

J74WLSY Wolsey Shale (Middle Cambrian)

420MSLD Mount Shields Formation (Middle Proterozoic)

420SPRD Shepard F om13tion (M iddle Proterozoic)

420SSLP Snowslip Formation (Middle Proterozoic)

420HELN Helena Formation (Middle Proterozoic)

420EMPR Empi re F onnation (M illdle Proterozoic)

420SPKN Spokane Formation (Middle Proterozoic)

420GRSN Greyson Fonnation (Middle Proterozoic)

Depth ofwell--in feet below land surface.

Diameter of casing--in inches.

Casing material--P, polyvinyl chloride or plastic; S, stecl.

Top of casing--in feCI below or above (+) land surface.

Bottom of casing--in feel below land surface.

Primal)' use ofwaler--C, commercial: F, lire; H, domeslic; [, irrjgation; U. unused.

Depth 10 water--in feet below Land surface.

Inclusive geotoglc un 1/ (plHte 1 Hnd

table 2)

--OIs; OIvt

Env

Kg

Kev Jme

PlPqa

Mml

Dtj

£c

£cl Vms

Yss

Yhe

Ys

Yg

Source ofmeasurement--S, Lewis and Clark County Water Quality Proteclion District or U.S. Geological Survey; D, driller.

Pumping water level--deplh, in feel below land surface.

Abbreviations-- fl, feet: in., inch; gal/min, gallons per minute; °e degrees Celsius: )..IS/em, microsicmens per centimeter al 25 (lC: mglL, milligrams per liter.

Symbols: --, no data; <, less than.

TABLE.3 55

Table 3. Records of wells (Continued)

WeU num­ber

Locatioo number

I ()<INO~W02CADO(l1

2 ()QNO.1WO~BCABOI

I)QN01WO)cOOAO I

(lYNO) W04CDAAfJl

09NOJ W05ABAAO\

fo 09NOJW05AI)DCOI

9

10

II

12

13

14

15

16

17

IS

19

20

21

22

,. --'

24

25

26

27

2&

29

09N03W05ADDOO\

O9NOlW07CBCCOI

O'lNOJWOQAODCOI

09N03W09ABCBOI

U'INOJW IlllCOAOI

09NO)WI40ACCOI

09NmWlhCBCCOI

09N03Wt70BC 01

O9NmW23BDDDO I

O9N04W02[)AODOI

09N04W09DJ)ACIlI

09N04W09DDDD()I

09N04W I OCBBAO I

09N04W IOCEBDOI

09N04WIICCCBOI

09NQ4-WIICDBDQI

09N04WII DCAOOI

09N04WI2BDCAOI

()')N04W 12(:ABBOI

()'IN04WIKCOBOI

09N04W ISADDllOI

09N04W 15BBBOO I

u9N04W 1 6J\;\ABOI

Area

SH SH

SH

SH

SH

SH

Sf!

SH

SH

SH

SH

SH

SH

SH

SH

511

511

SI-I

SH

SH

51·1

SH

SH

SH

SI'I

SH

Sl-t

SI·I

SH

Aliltude of laod ~urface

(ft)

Aquifer code

Depth of well

(fl)

4.\9U Il .'SDMS 195

4.JOO 420HGLN 241

U:W 420HELN 656

4.590 .\.11 MOSN 712

4,700 371HMRK 52.5 4.MO J41JI'RS 621j

4.700 34IJfRS

5.01U

4.520

4.515

4.24(1

4.075

4.630

4.750

4.210

4.470

4.960

4.960

4.790

4.820

4.850

~ . 9RO

4.RRO

5.020

5,020

4.960

211BLDB

21IBL[)B

211 BLOB

420 HELN

J71HMRK

211BLDR

211BLDB

211BLDB

34IJFRS

211 BLOB

IIIBLDR

J31MSNC

220ELLS

2\ IBLDD

2 11BLOB

320QDRN

nOPSLV

220t:LLS

211BLOB

211BLOB

211BLOB

2\ IBLOB

620

ISO

750

552

79

145

105

207

ISO

234

192

340

87

95

122

t:!.4

128

1)0

102

249

220

98

50

Well CO {IIpletioll

Diam-eter of Casing

mate­casing

rial (in.)

6

6

4

6

R

4

" 6

4

6 4

f;

4

R

8

6 4

6 4

6

6

4

6 4

6 4

6

6

6

4

n

6

o 4

6

4

6

6 4

~

4

6

4

6

4

6

s S

P S P

S P

S

S P

S P

S

P

S

S S

P S P S

s p

S

P

S P

S

S S P

S

s I'

s p

S

r s p

s

s p

s p

s p

s p

s

Top of CaslDg

(ft)

"'0.8

'·2.6

9

+1.5

7 +.5

x ~2.U

+2.0

46(J

+.f..

In +2.0

HI ?S

(,

'1.2

9 -<-3.1

+1-2

",".R

12

+ 1.9 20

72

U

+2,0

10

+ 12

+.8

15

'-1.45

10

+Ll

10

'.9

8 +LO

+I,g

9 H ,2

9

+1 n 20 +,20

5 + 6

56 Hydrology of the Helena Area Bedrock., Wesl-Central Montana, 1993-98

B.ilttom of

casing (ft)

Date well con-

strucled

09-06·71

18 OI-04-9J

241

3SR 11 · 21 -89

656

\ 8.5 08- 16-89

712

- -RS 482 1O-30-'l2

620

20 03-19-92

620

28 07-03-84

180

20 04-24-93

750

20 ,5 11-22-8R

552

I R 09.{17·8S

79

145 04--09-93

21 09-03·85

105

22 03 -1 4-86

207

5S.5 12-29·90

18U

192 04-1~-74

18 10-12-93

340

22 09-07-74

95 36 II-OJ-92

122

20 09-15-86

124

56 ,5 11-16-&9

12K

20 04.21-80

102

18.5 05-17 -R~

249

36 05-11-94

220

21 08-29-91

98

4'2 07-03-75

Pri­Ulary u~e of water

H

H

H

H

H Ii

H

H

H

H

II

H

H

H

H

H

H

H

1·1

1·1

Ii

H

H

Ii

fI

I-t

H

Water level

Depth

to water

(rt)

130. 14

21J .63

245

364.64

274 ,4

2~U2

500

39.35

127.7J

224

45.14

22,98

Ib.32

.1U ,03

1·7315

227.46

71.)7

H .O

JJ 24

16,25

M 14

10.25

2& 88

17.3 I

4~.22

~.OO

107

Source of D1I.1(' of

mea~­

ure­ment

s s

o

s

s s

n

s

s

o

s

S

S

s

s

5

S o

S

s

S

S

s

s

s

s

s

s

S

me-as-ure­menl

09-14-9~

09·U6·'I5

11-21-89

0'1-05-95

IO~16-Y5

09~5-95

03-19-92

U9 -ot.-95

09-0~-9S

11·22-88

10-22-93

10-20-93

j()·22-9J

12.20·93

01-19-'14

11-17·93

09-07-95

10·12-9.1

11-17-93

09-26-95

lO-lJ -9J

10--14-93

10-14·93

08-25-95

11-08·93

09-0 5-95

09~5-95

10·13-93

09-07·95

Table 3. Records of wells (Continued)

Yield (gal/min)

6 I ~

II

20

15

15

)0

37

~

20

20

10

10

15

10

9

12

12

II

10

6.5

15

I()

10

25

15

7.5

10

Pump­ing

period

{hours}

2

2

.15

2

.5

.,

.5

.5

.5

1

.5

WelllC'St datA

Pump-ing water Sou ret of

levd data

(ft)

190

232

360

615

175

))

68

464 139

100

160

175 ))0

48. 7

9()

III

j 9.5

114

R) , I

28.8

95

92

2,)

50

D

o

D

D

o

D

D

D

o

D

S

o

D

D

D

D o

s

D

D

S

o S D

S

o

D

D

D

S D

Date yield meas­ured

09-14-71

01-04·93

11 ·21 · 89

08-16-89

10-30-92

0) · 19-92

07·03-84

04-24-9.1

11-22-88

09-07-88

10·2209)

04-09-93

09·03 ·85

OJ-14-86

12-29-90

04-18-74

10-12.93

11-1 7-9J

09·07-74

11-03·92

10-13-9J

09·15-8"

10·1-1-93

11 - 16-89

10-16-9)

04-21 -80

05·17-88

05-11·94

08-19-91

10-13-93

07-03· 75

Tem­pera­ture ("C)

11.5

11.5

13,5

14.0

105

14.0

12.0

12,0

1 J.O

7.5

7 ,5

11.0

IU

10 . .0

11.0

15.0

15.0 1(0.5

9.5

9 ,0

11.0

8..0 85

R,O

),5

7.0

8.0

7.0

~ .O

7.5

7.0

7,S

7.0

10.0

8 5

80

6.0

8,0

g,O

Specific conduct­

Boce C).ISkm)

1,010

448

555

536

571

410

3~1

~91

420

307

314

552 548

501

620

552

495 544

436

397

1.120

557

267

246

261

288

189

396

409

425

276 265

.100

)08

312 407

276

On~il" mCIIsurement5

pH (srand­

ard units)

7.6

7.7

7.9

7.1.

Il.R

7.1>

7.7

7.6

7.6

7.0

7.1

7.9

7.7 7.7

7.7

7,6

7.& 75

6.9

7.1

S,2

5.9 7.3 7.2

6.1

7.8

7 I

68

6,6

7,U

68 7.5

7.1

V 7.4

8. 1

7.4

H 7.1

g,O

6R

Source Nitrate of mess- Date of (mg/L ure-- measure-

BS N) menl mrnr

<,5

<,5

<,5

<~

<.5

<.5

<.5

<.S

" .. 1 .9

2

<.S

<,5

2

< 5 ,,-;,5

<, 5

<.5

<'.5

<.5

I

2

4

<. 5

2

s s

s s s

s s s s

s s s s S

s

s s s s

s

s

s s s

s s s

s s s s s s

s s s

s s s

s

s

09·14·95

09-06-95

09·11·95

08-15-%

09-05·95

10·06· 95

09·05.95

08-09-96

09·11-')5

09-06-95

08-07·96

09-05-95

OS-09.%

10.20-93

10-22-9.1

10-20-93

03 ·02-94

09-22-95

10·22·Q)

10-07-93

10·18·93

11·17-9_'

09-O]-9~

09--67-95

11·17·9)

03·02.<)4

09·26-95

10-13·93

09-25-95

M·O~ · 96

10·14-93

03·02-94

10-14-93

0~·25·95

1)9·04·Y6

1 1-06-93

()'I·Oj·95

OS·OR·96

09-05·95

10- 13-93

(19·07·95

Wcll num­ber

5 6

R

9

10

/I

12

IJ

14

15

16 17

18

19

2()

21

12

24

25

26

27

28

TABLE 3 57

Table 3. Records of wells (Continued)

Well num­ber

Loculion number

)0 09N04W 1 hIlACBO I

31 09N04WIl'\f) l)A801

.1! OQN05WOJAACCOI

JJ U9N05WOJABC[J01

35 OQN05WI2CCDAOI

.1 Ii MN05WI.1ACOBOI

37 O<>NOSWI6ijABBOI

3~ 09NOSW2 1ACOAOI

J ~ 09N05W]90OCCOI

40 09N05W2'100CC02

41 09N05W.l}C[){ 'CO I

~2 IONOJW I&I)DDC02

43 ION03W I9RC(,COI

4J JONt),)W IYCCBBO I

4~ ION0.1WI9CCOAOI

40 WN03W20CCAAOI

47 ION03W 2bCAACO I

48 IfINO)WHCJ\ACOI

49 ION OJW28CBAAt)1

50 IONMW2~CCCCOI

51 ION03W29BOCCOJ

52 JON03W,10DADAOI

5.1 IIINOJWJICBODOI

54 ION O.IWJ2A DDAOI

55 IONu.1W.12IKBDO I

51> ION04WlJIDBBBOI

57 ION().jW02BAIlDOI

Arell

SH

511

WM

WM

WM

WM

5J,

WM

WM

WM

WM

SH

SH

SII

SH

51·1

511

51,1

5H

SI·I

SH

511

SH SH SII

SG

SG

Altitude of land ~Ilrfacc

(fl)

Aquifer code

5.I}O 211BLDR

5.110 211Bl013

.1,470 211BLDB

4A70 211BLDil

4.5 j() 21 I FlLDI3

Depth of "ell

(fI)

191

195

140

95

}OO

4.820 211 BLOl) 260

-1.720 2 11BLDB 6U

4.7211 211 ElKM 200

5.120 111BLDB 105

5.120 211BLOB

5.120 21IBL.DB

S.l ln 211BLDO

J .X45 420H EL N

) .920 12JSDMS

:;,960 420HELN

.1.91 X 420HELN

44

173

550

3:>0

IOU

HIS 420SPKN 150

H20 420GRSN 41 ~

3.'170 420(jR~N 90

4.0~5 420HELN 240

3.<)85 4201-1 ELN lOO

4.0J~ 12)$J)MS 106

4,200 371CMBR 140

~ . I (,O .J20HELN 120

4.190 420HELN 140

3)<51) 211SGVH 1M

4.1 80 211 SGVH 125

Well completion

Dlam-cler (If Cl!..!ilng

casing (in.)

I>

6 (,

4

Q 4 Ii

" 4

6

6

4

6

(,

6

J

(I

(.

4

" 4

6

4

6

6

(,

4

male­rial

s P

S

5

I'

5

P

S J'

S

P S p

S

P S p

S

s p

s r s s s S p

s r 5 p

s p

S

P

S

P S p

S

P

S

r 5 S S

P

s p

p

p

Top ()f cBsing

(ft)

rl .95

II

+1(,

,,2.0

40

..I..:! •• l

65

-1.2

5

-135

10

-120

5

"2 ,}

20

+I.J

7S "'1.6

o ) R

- 1. 2

10

-15

-1.6

+1.7

10

10

'1.1\ 10

o 5

58 Hydrology of Ihe Helen!! Arco Bedrock. West-Cenlral Montana. 1993·98

Bouom of

casin~

(ft)

20

191

12U 110

140

77

95

:>1

)00

20

260

21

MI 4!l

I ~O

~

105

49

20R

20 151)

44 72

In 40

550

20

320

20

100

(,5

ISO

2.0

415

~O

'1U

41

240

"'I 200 ]0

I(\n

20

120

111

140

I~

1M

125

125

Dlllr well

con· slrUCIW

08-24-S3

05-30-91

11-05·91

O~·1~·90

05·29-91

OJ- .ll·88

nR·19·7(,

OR-12-91

O.s · I'1·~K

04-25·90

10·3()'~7

OR-16-71>

04·D·S9

0'7.{l2-~

05· 11 .~(,

05'{)(' · i\')

10-H·R7

07· 15· 7~

Pri­mary use of waler

H

H

H

H

H

II

H

II

H

H

II

II

u

II

Woler Ic\'~1

Duplh 10

waler (ft)

70.JO

29,20

35.11>

,11) 52

9Nl

25.'17

M ,oJ

27.2)

11.7 1

14.3 1

2'1.15

52.19

55.40

4017

54.)(\

.19,)6

I~,o?

52.4

4(, .83

nO IR

Source Date of

of rue.us­ure­ment

s

::; s

S

s

5

s

s

5

s

s s

s

s

s

s

s

s

5

s

s

o

meas-ure­mcOI

10·1 4·93

09-u7, 95

11 -09-93

10·15·93

I()·IH]

10·15·93

11 ·11>-<»)

09 ·2 1·<15

U9·21·95

09·21>-95

OQ.1~ ·95

11-03·9.1

11·03·'»)

11·0.1·'1)

10·1~-\))

1)9·21·9,

10·1<)·<))

10-J2-9.1

0'7·IS·7 ~

Table 3. Records or wells (Continued)

Yirld (gal/min)

16

20

IJ I>

9 4

61

20

X

10

20

12

20

50

40

80

50

15

.j

10

30

20

15

30 J()

Pump­Ing

p"rlod (hours)

.75

4

.59

,5

1

.5

.5

1

2

,83

2

,5

Well leS! dala

Pump-ing waler Source of

leyel daIS

(0)

ISO '11\9

190

1J6

90

31 .5

1'>5 51.7

256

94.2

56

15.2

175

.10 , ~

1110

31.3

1'10

155

300

145

70,0

4(lO

70

lolO

!l

S

D D

D

S o S

D

5 I)

S D

$

D

S

D

D

D

D

D

D

D

D

o S

D

[)

D

D

D o

D

S

Dale yield

meas­ured

10.15·86

10-14-03

OH-25-H3

05·.10·91

L 1-05-'l 1

10-15·93

05·22·~'>

10-14-93

OJ-26-87

10-15-QJ

05·24·90

10·15-<»)

05-29-9L

11·16.9;\

00·20·85

11-16-93

OJ-)J-~8

08·19· 76

0~·12-91

05 · 19·~~

04·15-",0

II·OJ·P

0~-16-7(,

10-22-93

02-26-79

O~·III-&9

04-28-87

1)7-0~-gll

05-06-89

10-2:l-S7

07-2X-9.1

10-25-9J

Tem­perll­lure (~C)

7,5

75

~,O

10.0

10.5

9,0

110

9,0

9.0

9.0

7.0

8,1)

5.5

10 ,1)

XU

S.5

11.0

11.0

11.0

105

12_0

11.O

8,0

9.5

11.5

12_0

11.0

10.0

10,0

11.5

11.0

130

100

Spl'('ific

conduCI­ance

(liS/em)

302

:99

37~

417

11 I

3S6

353

445

485 440

863

13.1

482

1 . .190 1.30(1

1,350

51&

54~

(,}I

1.520

bl()

nil

~26

I,U)O

1.030

1.120

I ,()9()

fI~2

Onsite measurem~nlS

pH (sland­

ard units)

7.4

72 66

7,7

7.2 7.4

7,0

7,2

7,2

1>9 7.6

7.4

64

X.5

7.8

8,0

7.2

7.2

7.0

7J 73

7.6

7.6

7.3

" I 7.7

7.7

7.S

7.8

7.1>

8.0

7.6

Source Nitrate of mns- OllIe of (mg/L ure- measurl'-a~ N) menl menl

<.S

<.5 ,_5

<, 5

II

-1

5 7

4

s s s

s s s

s s s s s

s

s s

5

$

s

s s s s s s

s s s

s s s s s

s

111-14·93

09·20-95

09-0-1-96

I L-{l9·Y}

11'1·27-95

10·15·9)

10·14·9)

0)-011·94

10-15·93

09-04-96

14>-1 5-93

11-16-93

11·16·Y}

09·21·95

0~·13.9n

w-n-'1s

11-il.1-93

10·21·9)

m-05·94

09-25-95

06-17-R3

10-22-93

10-21 -'1.1

10·21·9)

O·)-21·9~

119·04·%

to-I ~·9-'

j()·10·9~

11-09-9J

0.1-U2-9'

09-22-95

10-25·93

07-34>-96

Well num­ber

30

J I

32

3J

34

.15

39

40

41

42

4.1

-l5

47

4R

50

51

52

5.1 54

55

511

57

TABLE 3 59

Table 3. Records of wells (Continued)

Well num­

ber

Location number

~8 lON04WO~RACDOl

~9 ION04W02CAtJAOl

~o ION04W02CIlAAOI

61 10N()4wn2CDCDOI

62 I ON04 W02DABDU I

hJ I ON04WOJABBAO I

M lON()4WOJADBDOI

6~ 10N04WO)cDBAIlI

66 10N04W03DAAAOI

67 ION04W03l>ADAOI

6~ ION04WOJDBBDOI

69 10N04WO.1DBD!)01

70 I ON04WOJ DCBAO I

71 I ON()4WOSAA DDOI

72 ION04\VOftARA(01

7) ION04W08DCACOI

74 ION04W09DBAAO1

75 ION04WIOCCDDOI

7& ION04WI2CBBDOI

n ION04W I5 BDACOI

7R ION04W16DDAAOI

71) IhN04W12DBABOI

80 ION04W2JCADDOI

81 ION04W23f)ACDOI

R2 ION(l4W~)OCAAOI

83 1 ON04W23DDDDO I

84 ION04W24ADBCOI

8S ION04W2SACDDOI

R6 lON04W2MACBOI

Area

SG

S0

so

SG

SO SO SG

SG

SG

SG

S0

S0

SG

SO

WM

WM

WM

WM

S0

WM

WM WM SH

SH

SH

SH

SH

Sf!

SH

Allilude of laDd surface

(ft)

Aquifer

code

'!.I/i() 21IS(jV]-t

4.041) 211SGWI

.1.990 211 SGVH

J.990 21IS(;VH

Deplb orwell

(ft)

180

135

110

46

177

4.190 211SGVH 50

'l.IlO 211SGVH 103

4 .116 211SGVIl 206

4.065 211 SGVIi 140

4,045 211SGVH 90

4.15(. 211SGVH JOO

4.060 211SGVH 14(1

4.070 ~IISGVH 160

4.140 420SPKN 125

4.100 4~OHELN 100

4.222 420HELN 120

4.165 420SPKN 200

3.970 420SPKN 201

3.865 420SPKN II)()

4_050 420SPKN 160

4,00-5 420EMPIt 100

3.980 420HELN 7~

3.Q90 420HELN 1)0

4.005 420HELN 107

4.010 420l-U::LN 14()

4.110 J20HELN 224

3.915 IIOALVM 75

4.100 42()HELN 185

4. 170 420H ELN 2R~

W~II completion

Diam-eter of Casing casing JOatc-

rial (in.)

6

4.6

(;

6 (;

4

6

6

4

6

5 (-

4

n

6

J

6 d

6

-I

6 4

(.

4

6

4

I>

n n I>

4

(-.

4 (-.

4

Ii

4

Ii

4

n 4

(;

-I

s p

S P

S

P

S

P S P

S

P S

P S

P

S

P S P S

P S

r S p

S

P

S

P S S

S

P

S P S

P ~

P S

r $ p

S

P

Top of

casing (ft)

+1

8

+\.45

L~

'·25

+11

o 13

+.Y

>J 7

+IR

10

12

~IA~

16

~IO

25

'"1.2

+.R

1-1.0

15

"1.5 9

+1.0

+1.~

65 ~ 8

+1.2

f~.6

10

-.8

P

'"1.6

60

+1.5 9

+1.0

15

+1.9 S

-H. I

10

60 Hydrology of the Helenll Area ~drock., Wesl-Ccnlral Montana, 1993-98

Bottom of

cHslng (ft)

21

180

20

135

110

Dale well con-

$Iructcd

10-}4-75

OK-OS-76

- -94

24.9 02-27-73

21 10-28-75

103

185 02-20-90

206

20 03-2S-78

140

14.3 02-22-73

90

20 il5·17- 78

JOO

~I 03· 10·7(0

14(.

05-26-77

31i 04-06- ~7

125

20 (l(.· .l(I-94

100

20 06-28-').1

120

20 06-2n-75

200

)3 08-0)-74

20 I 09-04-91 J

III 10·29·7.1

100

81 07-06-P

260

78 07-1 (}.8-I 20 ()<I-I(}.90

130

10 ()7-0 .1-R6

107

~O (I;·2/i-1j.j

140

I~ 03-24-8S

224

28 09·IY·87

75

20 09-16-91

185 J~ 10-23-92

282

Pri­mary

use of watcr

H

H

H

U

fl

Ii

H

Ii

H

H

H

H

H

H

II

H

u

C

H

II

H

H

\Vater level

Deptb to

water (rt)

)0

)0

32.30

I ~

1~ .4R

2KIIS

.11 .06

55

21

70 .S4

IJ .OR

50.91

suo

.'i1 .. 12

47.2R

10.42

4().OO

49.46

40 . .16

53.75

79.92

%.0.1

126.70

3n.21

110.3\1

195.74

Source of

meas­ure­men!

D

o

s

S

D

S

s

o

s

D

D

S

S

s

s

s

s

s

s S

S

s

s

s

s

s

Dale of meas­ure­mCl11

10·14-75

11 -14· 7(,

10-29-92

02-27-73

IO-0c\ · ~4

04..(J1-?~

U3-2R· 7ft

1(}'25-R~

05-17-7S

0)·10-76

114·14-93

IU·OS.9.1

OR-2R-95

OX-2N·95

10- 14-9.1

10-0~·9.1

10-04-95

11·IlS·93

10-31·'XI

11-05-?3

11-17-93

11-05-9.1

09-01 ·')~

II-OR-9)

11-05-9.1

II-UR.93

Table 3. Records of wells (Continued)

Yield (gal/min)

20

,10

20

t~

t2

7

12

12

:\1) 12

~O

12

6,7

IS II

15

14

10

20 5

12

20

30

25

.10

Pump­ing

pcriod (hours)

2 5

10

J

.5

2.0

.42

.XJ

J

.S

U

2

.33 2

2

2

2

Wdl test datu

Pump-Ing water Source of

level data (flJ

IRO

1)0

xo

()5

109

44.4

40

140

12U

29.~

115

190

74,9

19U

65,2

260

00.8 7R

126

57.9

97

75

I R I

271

D

[)

D

D

D

S

D

D

D

D

D

S D

D

D

S

D

S

D

D

s [)

D

S

D

D

[)

D

D

D

Datt' yield meas­ured

10-24· 75

04-17-85

10.28-75

02-20-'10

11·1 ~·~3

Q3·28-7R

02-'22-73

05·17· 78

03-10-76

04-06-87

10·OR-93

06·30·94

06-28-94

0&.26-75

10-1~-9J

09-G4-91

IO-O~-93

10·29·73

07·06-R7

10-31-90

07· ((I·R4

04·10·90

11-17-93

07-03-86

OS·21i-94

09.19.R7

1()'~J-Q2

Tem­pera­ture (DC)

11.0

11.0

11.0

105

10,0

11.0

115

11.0

10,5

10,5

11.5

10.S

11.0

11.0

12.0

10.0

9..5

9.5

11.0

10.0

I 1.5

11.0

11.0

11.5

120

10.0

13.0

150

15.0

12.0

11>,0

10.0

10.5

12.0

!.l,S

Specific conduct­

anre (jJS/cm)

455

782

450

41>9

481

719

776

350

495

500

518

569

502

423

1>211

1.230

444

436

444 1.150

794

no 623

74~

5}9

550

546

7U2

994

1,030

1.120

~40

531

Onslt~ measurements

pH (stand­

ard units)

7.8

7.9

7.1>

7.1>

U

7.3

7.2

R.2

7.7

H

7.7

].6

7,7

7,9

7,9

77

8,1

'X 7,7

7,X

7.4

75

71

g,O

7.4

~2

75

7,~

7.9

i.R

7.4

7,7

7,5

6,)

7.7

Source Nitrate of mcas- Date of (rngll, urI."- moasurc-os N) ment ment

2

<',-"

2 3

5

4

<_5

<.5

4

4

4

s

s

s s s

117-JO-Q6

07 • .10·96

05-31-90

11-IX-Y3

03·03·94

S 09-09-9i>

s s s

s S' S

s

s

s

s s

s s s

s s S

s

s s s s s

s

s

s

s s s

09-2R-95

I\X-21-\l6

07·31·%

09-28-95

09-U5·9(,

11·IR-9J

07-JO--%

07-) 1-96

07-31-96

10-0&-93

08-28-95

OJl·19-%

10-14-9.'

1O-0~·<l3

03-05-94

10-04-95

II·M·93

10·31·<)0

11-05·93

11-17-93

03-02-94

11·05-9J

O~-01-95

11.08·93

11-05·9_\

()9·21-~5

09·04-96 11-12-93

Well

num­ber

60

(,J

~l

6,1

64

~7

69

70

71

72

74

7~

7~

77

81

82

TABLE 3 6J

Table 3. Records of wells (Continued)

Well num­b~r

Locsnon numb~r

~7 ION(I4W26ABACOI

x8 ION04W21i8AAt\OI

~~ ION04W2713IlDAIII

90 IONO~W2'1BHIKOI

91 ION04W3JIlIlAI)OI

92 IIJN04W35CACCOI

I):> I()N(t~W36CAAOOI

94 I ON(l4W_16DCBBU I

95 I ()Nu~W03ABCBO I

<)/, ION05WOJABODOI

97 loK05W05COBAOI

9~ Il)N05W09BDBCIII

9'1 IO~·1l5\.l"-IOADBB(l1

100 ION05W25DRDAOI

10 1 IONO.'W2SUBU!\0!

1112 ION05WJ2ACCAOJ

10) JON05V..-J).->.DD 01

104 ION05W1~JKDDIJJ

105 ION05WJ}CDCDOI

106 IONU5WJJCOCD01

107 IONOSWHOCBAOI

lOS ION05WJ4DC!3AOl

109 IONOSV.' .16BABOOI

110 IUN05W)6CBBBOI

II I ION05WJ6[)ABOOI

II C ION05W)(,DA!)I)(JI

I L1 I ONOIIWO 1 CI)t\ Bil 1

114 II N021.V 18BCDDOI

115 I I N02W IRBOCI101

Ii'" I IN02W IRCACCU)

11 7 I I N021.V I 8CIlAAUI

II~ IIK02WIRCCBOll

ArCII

Sit

SII

WM

ViM

SH ~H

SI-I

SJ-I

WM

WM

WM

WM

WM WM

WM WM

I.VII<!

WM

WM

WII<!

WM

WM WM WM

\\lM

\\1M

WM

NH

Nil

NI-I

NH NJ-l

Altitudc of land

lurfac~

(ft)

Aquifer code

Depth of well

(ft)

4.1(,5 420HFLN .255

4.195

.1.020

4..190

.I.J6U

4.6RO

4.220

.1.240

4_650

4.620

4.965

4.7S0

~20HELI' )91)

"1IBlDB 3S0

4201-IElN 100

~20IlELN 250

)74MGHR 475

J7IHMll.1< 160

HII-IMRK 1J1

J74WLSV 14U

J74WLSY I~O

34 1JFRS 110

211 BLDB 281

4 .~40 _\4IJFRS 14

4.1120 211 BLOI3 15S

4,620 2 11 BLDB 100

5_000 211BLOB 160

4.140 211aKM 21(1

4.752 "1IBUlI3 135

4,750 211RLDR

4.4SQ 21 tnLDB

4.459

4.550

4.)90

J .255

DJO

.1.7S0 _U~5

3.720

USO 1.oNO

2 11 BLOB

21 10LDO

111B1.08

211BLDB

l llBLI)B

~~OliELN

~20(jKSN

42()(iRSN

.l2IlGRSN

420GRSN

~2()SPKN

160

180

2~4

140

262

100

220

130

105

220

1 10

~()

Well completion

Diam-eter of C:.sing

ca~lng

(in,)

4

6

4 o 4

6

o 4

6

~

6

4

4

6

4

6

4

matE-rial

s p

S I'

g

P

s s p

S

r s p

s p

s p

s r s p

p

S

P S S P S

P S P S

P

s p

S

S S P

S

P

S

r

s p

S

P

s p

Top of casln·g

(fl)

+1 I

10

·25

10

+2_1

o

+2.9

-9 10 , 1.5

20

~ . 9

12

;- 1.7

10

+20

~O

., 1.8

10

; 2.0

10

+1.5

'-I.II

10

+ 1.11

+2 .0

10

+1.6

10

- 1.6 10

-1.1> 1>_0

+211

,,- 1.7

~

~ ,6

9

+1 7

20

1.4

10

2.0

10

-2.0

10

62 Hydrology of the Hl"Iena Area Bedrock, West-Central MOlllall9, 199.3-98

Bollom of

casing (ft)

JR 255

20

390

15

3BO

21

47~

40

t60 21

IJ.~

11

140

61

140

17

110

I ~

nl

Dale well COD-

structed

114·I7·Y}

04·11-89

05·11 ·93

06-20-85

10·1-'·91

OS.{)9-94

0~·1".74

O~-19-9)

I~ - -~6

200 n~·JI·Q2

155

I ~ 07-O.Q·9J

100

11 I ".()7-82

110

21.0 06-05-90

2M 40_0 06-~7-81

1)5

06-1 }·9b

I ~ . 5 10-28-80

I~O

11· ·Y5

- .74

1 R_5 1I5·0l!·~7

262

1 ~ 5 09'{)9-8)

16(1

40 09-23-ft~

220

20

220

20

160

20

RO

O~· ·95

07'{)6-93

01-03-94

08-10-92

Pri­mary u~e of wDter

H

U H

fI

H

H

H

H

H

H

fI

Ii

U Ii

II

H

H

C'

C H

H

H

II

U [I

H

H

Deprb to

waler (ft)

146,19

11 ..14

5),)4

3().1 ,I!5

7452

67,69

5955

]4 ,70

19,8')

50."'9

I> .14 75,67

75.11

J~_07

17,44

16,19

17

1612

1143

32.63

l~,!4

30 I X

11.94

J9.49

IOtHO

100_80

100.4~

20_89

Source DlIlt' of of

rous­ure­men!

s

s

s

S S

S

s

s

s

S

s

s s

S

S

<;

s

5

S S

s

s s

meas-ure­

menl

09-01-9~

U9-0 1-95

11-1O- ~,

OJ ·~ 1 -9~

1 1·1~·93

11 - 1"-93

10- 1)·93

IO-O~·93

08-15-95

tll - IO-94

1O·07-~3

IO-UI · ~5

10.01·95

10·10-95

11 -1~-9J

10-10-95

06-- 11·9i>

10·10-95

o 1·24 .9fj

10·01 -05

11-12-93

OY·ON·95

0~·24-95

1()·}S·95

10·15·95

10-25-95

10-25-95 11'{)4·9.1

Table 3. Records of wells (Continued)

Yield (gal/min)

12

35

30

to

11

)()

10

11

.\0

to

1>.1>

!5

20

,<0

12

10

\U

IU

12

R

32

15

11

12

10

30

Pump­Ing

period (boars)

.17

.5

'1

J

4

2

8

,2

2,5

W~lI tcst d~tll

Pump-ing water Sou reI.' of

level data (ft)

242

375

71

~7.7

4115

155

127

73. 7

lJ6

105

265

130

200

J 1.('

110

51

250

40. ~

150

215

IJ. I

201

I~II

D

o

D

S

s [)

D

D

S o

D

o

D

D

D

S

D

D

D

o S D

o s

[)

o

o

DatI.'

yield

mellr urcd

04· 1 7.9)

06--04-92

04-J '·89

1'-1U-Y3

11-IR-9J

04-2.1-R6

OS·I'·9)

n~·2(J·X5

10·13·93

10-23-91

OS-09-94

08-29-74

05·19-93

07--09-93

1 ~·07·S2

LI·12-93

06--05-90

06-27-81

1002R-RO

05-08-&7

11-12-93

09·09-83

09.23.R8

10-15-93

07-06--93

0'.0)·94

08·'0·92

Tem­pera­

ture

<"C)

14,0

13.5

1J.5

11.5

13.0

IU

11.0

11.5

11.0

Ito

IJ .O

90

9.0

R.O

95

10.0

8 5 R.O

9.5

I \.0

10.5

10_0

9_5

'15

10.5

10.0

10,5

10,5

to.5

10.5

10,5

10.0

80

12,5

12.0

13_5

Specific conduct­

ance (liS/em)

6-16

7S8 428 387 725

717 578

506

533

875

514

~39

4(\8

4~6

557 537

~Ot

1<J2 410

5% J91

6.MO

5)30

290

B4

742

204

220

213

555

720

70J

591

Onshe JT)ClISU ~eJT)fnts

pH (M>lnd­

Brd units)

7.8

7A S,I

7,9

7,4

R,O

7,2

16

1.5

5.1

/,5

7 I

7.\

7.}

1,1

7,2

7,1

7,)

~,3

73

7.7

6.9 7.0

6.9

1>9

7, I

7, 1

7..1

8.0

7.0

7.5 6.6

/ . 1

7.5

7.5

7.6

Source Nitrate of mea5- Date of (mg/L urI.'· mcuurc-as N) ment menl

J

4

<. 5

<5 "'.5

I < ,5

6

<"5

.4

2

<,5

3

I

2

s s s s s

s s

s

s

s

s s s s s

s s s

s s s s s s

s s s s s

s s ~

s

s s

s

09-01-95

08·13·96

09·01·95

09-00-96

11·10·93

11·1 ~·9.'

11 -09-93

09-1S-'l5

10-13-93

10·oS· 'H

0~·25-95

09·01·95

08-21-96

10-07-93

10-01-95

09·Q<I-96

10-10-95

0~-15-%

1I ·1l-93

OQ·2R·95

08-13·96

10-10-95

08-1.1-96

II-O~-'l~

10·10·95

O~-O 1-%

10-01-95

11-12·93

OQ-O~·95

10-15·93

03-02-94

09-21-'15

08·21·96

I (J-2S·95

08-21-90

11--O4-9~

Well num­ber

87

88

89

9(1

91

92

97

IlR

99

100

lUI

10~

10J

104

105

I Of>

107

lOR 109

llU

III

112

113

114

II"

116

117

I \~

TABLE 3 63

Table 3. Records of wells (Continued)

Well

num· ber

Location number

119 I INOJW02ACAAOI

120 I I N03 W02CDC DO I

12 1 1 I N03W02lXBDOI

122 IIN03W04AABBOI

123 II NO)W04ABADO I

124 IINOJW05BCCAO I

115 I I NII)W05CCBCOI

12(, I I NOJW()6BBAAOI

127 I I N03W06OCAAOI

128 I I N0.1W07BDBCO I

129 II NOJWORRC8AOI

1.10 II N())W()9BDBAO I

lJ I I I NO)W09CBOBOI

132 I I NO)WIOCCCCOI

133 IIN03WIOJ)ABMI

134 II NOJW I ODDODO I

1]5 1 I N03W I I Bn13AOI

lJo IINOJWI6BBBBOI

137 I 1 NO.1W I6('CCBOI

1}8 11N03WI 8A DBCO l

139 I I NO.1W 18BA B AOI

140 IINOJWl8BBACOI

141 IIN03WISBBBCOI

142 IIN04WOlAADAOI

143 IIN04WOICCBCOI

144 IIN04W02DBOCOI

145 II N04W06DACAO I

146 II N04 W06DCC'CO I

Arc.s

NI~

NI-I

NH

NI·I

NH

NH

Nii

NH

Nii

NH

Nii

NH

Nii

NH

NH

NH

NH

NH

NH

NH NH

NH

NH

N~I

NH

WM

Altilude of land surface

(ft)

Aquifer code

Deptb of well

(ft)

4.105 420GRSN 660

3 ,910 420SPKN 2~4

3.990 420GRSN 250

4.120 420GRSN 180

4.100 420GRSN 140

~ .0)0 42()SPKN 9()

3 ,965 420S PKN 110

4. 100 420SPKN 137

3.965 420SI'KN 125

},890 420SPKN 140

3,895 420SPKK 208

),865 420SPKN 240

J.8J5 420SI'KN 57

3,765 420SPKN 97

MAO 420S rKN 420

.\.770 A::lOSPKN 98

3.900 420SrK N 350

3.78~ 420SPKN 125

3,705 IIOALVM 53

3,ROO 420SPKN 89

3.S3S 420SPKN 1.10

J,840 420SPKN

3.830 420SPKN 124

.1,070 420GRSN DO

J.81\0 420GRSN 150

4.050 420GRSN lAO

A.DO 420SPKN 50

~,210 420SPKN 115

Well completion

Diam· eter of Casing

mate~

casIng rial (in.)

6.6

6

4

6

6

4

6

4

6

4

Ii

6

6

4

6.63

4

6 ~

6.63

(,

4

(,

6

4

6

(,

4

6

f,

6

4

6

(,

4

6

4

6

4

s P

S P

S

S I'

S

P

S

r S r S

r S P S p

S

s

s r S

s P S

s p

S

5

P S

s

s s p

p

s p

S r S P

Topor casing

(ft)

.. u 240

'-1.4

14

+2.0

+1.5

10

.... 1.4

9

"1.6

10

+1.3

10

".6

+1.0

105

7.9

+2 ()

+1 )

16

-'-2.0

180

;'.9

'1.2

10

1-1.6

+2.0

n + 1.3

+ 1.7

+,4

1.8

·,.j .0

6

"I.)

10

-'-.6

10

+1.7 95

64 Hydrology of the Helenp A~a Bedrock. West-Ccntral Montana, (993~98

Bottom or

casing (ft)

261

660 138 254

Date well con~

structed

04·12· 93

04·11·94

. ·~O

20 07-ll-!)4

180

I~ 06·28·93

140

20 90

20 110

21

137

08·22· 73

08·02·88

05 ·2.1·77

112 09· 1 (}'77

125

20

140

142

21

57

?7

12·10·91

08·04·82

. ·94

0) · 1 H· 74

07·25·90

20) ()4·01·83

400

98 05·1)4· 73

179 01>·17.93

350

41 05·01·85

53

89 I f). I 7·g(\

lAO 04.0J·QO

114 11 ·()9·91

21 06'{)2·76

150 ()6.14.7S

22 OS'{)I·85

lAO

18 11.20-83

50

105 0)·22·9(j

liS

Pri­mary use of water

1\

H

H H

Ii

Ii

~I

H

H

H

1-1

H

H

1-1

Ii

II

1-1

Ii

H

Ii

H

1-1

I~

H

1-1

Ii

H

Waler level

Depth to

waler (fl)

504

127.22

196.70

3R .~5

29.411

n05

SR ."7

103.29

IIS. IO

51-)0

50.58

47.30

23.29

53.))

DI.90

1\2.83

162.70

50.!! I

7.31>

60 .94

99.58

97.76

82.57

73.14

70.87

73.47

.18.7(1

15.75

Source of pate of

meas­ure­ment

s

s

s S

s

s

s

s

s

s

s

s

s

s

s

s

s

S

s

S

S S

S

s

s

s

mCKS-

ure­menl

07·IS·9~

10·23·95

10- 19-95

10·25·95

07-01-93

1(}'23·95

10· 19·95

10-25-95

10·26-95

11·11)..9.1

10·31·90

12·02·95

11-09-93

11·12·9~

1~24.9S

11·04·93

10 · 19-~5

01·25 -90

11·10-93

11·111· 9.1

10-28·95

07·29·94

10·25 ·9)

\0·27·93

1()·27·95

10·21·93

Table 3. Records of wells (Continued)

Yield

(gal/min)

18

50

~o

15

20

30

20

IN

10

100

I~

20

20

13

15

\1

1 " 17

20

35

8

2(1

7.5

20

20

10 )()

9

15

9

20

30

IU

Pump­ing

period (hours)

2

.45

)0

3 .45

2

.J)

I

2

.5J

.5

,6

2 35

2

3 .5

I

.5

.5

.5

W~lIlest dahl

Pump-i ng wilIer Source of

level data (ft)

655

23~

16()

117

43.S

80

105

l JO

125

135

55

15.8

)90

RO (,5

HS

51.0

55.9

45

1>9

62 .6

110

102 . 1

100

100

71>. 1

50

66.J

136

776 40

95

20.5

D

D

D

D

S

D

D

D

D

D

D

S

D

S

D

D

S D

s S

D

D

S

f)

S

D

D

S

D

S

D S

D

D

S

Dale yield

meas· ured

04- 12-93

04·11·94

07·11·94

06-18·93

11 ·09·9.\

08-22-73

08·02·88

09-10-77

1.2-10-91

OR.04·S2

10·31·90

10·28·9J

03-18-74

11-09-93

04·01·83

05-{)4-73

II ~14·'11

06·17·93

07-25-90

HI·O)·9)

05-01·85

10-17-86

11-10·93

04-03·90

11. 10-93

11·09-'!1

06·02· 71-

10·25-93

(}6·14-n

10-22-93

OS·OI·SS

10·27·9)

11·20·83

OJ· 22.'l(j

10--21·93

Tem­pera­lure (DC)

24.0

13.0

14.5

10.5

9,5

10.5

10.0

10.0

10.5

11.0

10.5

11.0

105

13.0

12,0

11 ,0

IS ,S 12.0

10.0

1.) .5

12.0

15.5

16.0

14.0

16.5

17.0

11.5 10,5

9,5

9.5

11.0

11.0

11 ,5

10,5

11.0

11.5

11.0

11.0

10.0

11.0

9,0

9,0

Specific conducl­

aote (vS1cm)

IA)O

454

450

7;!2

690

675

635

434

484

480

502

502

380 451

426

86S

K40

560

722

72R 522

513

417

414

408

582

8M

610

583

383

373

772

488 474

646

606

3XR R2J 854

UOo 888

On~ile measurements

plt (~IBod­

ard units)

7 . ~

77

8,0

7.5

74

7.6

7.5

7.7

7.8

7.S 7.8

7.9

7.6 f...f.

7.7

7.9

7.7

7.7

7.R

8.0

80 7.4

7, I

H

7.8

7.6

7.8

7.7

79

7,7

H 7.f.

7.4

7.6

7.4

7.6

7.6

7.4

7.5

Source Nilrale of mess- Dille of (mg/L ure- mellsure-I\~ N) meOI meot

<5

<5

8

2

2

s

s

s s

s S S

S

s s s

s

s

s s s s s s

s s s s s

s s So

S

S S

5 S

S

S

S

s s s s s s

10·24·95

10-23-95

10-19·95

10-25-95

11-09·93

0)·05·94

09·"U-~S

10-23-95

10·19·95

08·09.9f,

10·24·95

10-21>-95

11-10-93

10-) 1·9()

10·28·93

09·20·9~

12-{)2-95

08·20·96 Il·09.9~

07-15-90

11-1 2·93

10·24·95

OS-~O.96

11-04·93

10-19-95

08 ·n-9f..

07·25-9(\

11·03-93

06-29 ·K8

11-12-93

11·10.9)

10-28-95

10-2b-95

10·25-93

119·06-96

IO·2M3

10-27-93

10·27·95

OR.20·96 10-2 1-93

03 -05 ·94

Well num­ber

119

12U

121

122

124

125

121>

127

128

129

130

131

132

133

134

1)5

1.17

I3S

139

140

141

142

143

144

145

146

TABLE 3 65

Table 3. Records of wells (Continued)

Well completion

Well num­ber

Location number

147 I I N04 W()9ADADOI

14S IIN04W09CBDOIH

149 IIN04W09(ODDOI

150 I IN04W09DBAAOI

lSI IIN()4WIllADDOOI

ISl II N()4W 10CCCC<1I

15) I I NIl4W I KUDOO I

154 I 1 N04W I3AAADO 1

I ~5 II N04Wl JI;IDBBOI

151> IIN04WI4CCDDOI

157 IIN04WI'IACBAOJ

IS ~ IINMWI9COABOI

159 IIN04WI9CBDDOI

160 II N04W2I1BBCDOl

11) 1 lIN()4W20DCBDOI

1/\2 I 1 Nt)4W22 BCOBOI

In~ II N04W24AAACOI

1M I I N04Wl4AACDil I

165 II NO~W24BBABOI

166 IIN04W25BBDAUI

11'7 lIN()4W~5CAAAUI

I('~ 1 1 N04W29cnBCIi I

169 1 I N04W30ACBCO I

170 IIN04WJ2ADCRIlI

171 IINO~v...'J2BCAAIII

In I I Nfl4W34 ACDOO 1

17~ IINII4W34DABBOI

174 II N04W)4DCB.4,OI

Area

NH NH

Nii

Nil

NH

NH

NIl

NH

NH

NB

\\11-.1

\11M

WM

WM

WM

SG

NH

NH

NIl

SG

so

WM

WM

WM

\11M

SG

SG

SG

A11i1ude

of land surface

(ft)

Aquifer code

Diam-Depth cter of Casing ufwell matc­

CIIsing (ft) rial

4.310 4~OSPKN

4.2R5 420SPKN

~,280 420SPKN

4.500 420SPKN

4.120 420SPKN

4.205 420SPK,N

3 .1\90 42USPKN

2~0

521

1i0

400

157

176

3.850 IIOALVM 150

H70 420SrKN 230

3.910 420SPKN 52

4.650 4.20HElN 472

4.470 410 H£l. N 300

4.545 420HELN 16X

4.4jO 4!OHELN 200

4.390 420BELN 160

4.000 420SPKN 197

3.805 ~20SPKN 170

USO ~20SPKN 120

3,880 211SGVH 373

3,~10 211SGVH 126

4,410 420Hf.lN 205

4.S50 420Hl:.LN 232

4.J20 42UEJI,I Pi{ 500

4.315 420flF.LN 125

0(1(\ 211SGVH 215

4.359 211SGVH 180

-1 ,240 211 SGVH 125

(In .)

6 4

6

4.5 (I

Ii

4

6

4

6

6

~

6

6

II

6

4

/)

4 (,

6

4

6

(,

Ii

n A

6 4

"

s r s p

s P

S

P

s p

S

S

s

s P

S S

S ~

S

P

s p

S

S

l'

S

s P

S

s p

S

r s

s

S

P

S P S

66 Hydrology orlbe Helena Area Bedrock, Wesl-CeDlntl Monlana.. 1993-98

Top of casing

(ft)

· ' 1.4

10

~1.6

20

~1,5

10

-1.5

9

- I 5

10

I 7

136

~III

6

-1.2

"".S

-.5

19

~ , 5

9 +I.S

~I.S

15

"'1 )

' · 1.4

25

d .3

+.6

10

'1.0

12

+1.7

"'16

o

+ 1.2

20

+.9

Boltom of

casing (ft)

IS

j2J

29 60

20

400

I~

157

18 250

152

176

Date well

con-structed

11 ·02-92

02-14-9 1

01 .26·'14

11 -16·84

10-06-93

11-19-13

01'{)1-85

10 09-19· 75

472

20 09'{)8-~R

200

19 11-27· 7'1

160

20 08· 17-87

197

100 05 -28-85

110 03.02-R7

170

12(1 04-14-81

47 06-20·73

373

116 (19 ·20-91

205

20 08-05 · 78

D2

IR 06.27.9)

8 115

21

ISO

2(J

09·19-73

01-19-74

Pri­mary use of waler

~I

H

H

H

H

H

II

Ii

H

fI

Ii

H

H

Ii

H

H

H

].I

Ii

Ii

H

H

H

Waler level

Oepth

10

waltr (fl)

35.)2

40.71

IO.IlK

32 .36

119.6 2

liS

1332

.169 ,70

158.50

1]7.09

~2 .4 7

89.8~

12.74

73.92

71.88

77.37

1J2.57

~5.14

97.40

154.90

71.51

45.69

II S.52

126

16.45

Source of Dllte of

mcas­un~­

menl

s s

s

s

s

s

s

D

S

s

s S S

s

s

S

s

s

s

s

s

s

s

s

s

D

S

meas-IIrt­

men I

IO·2X·95

10·29-93

10.26·9)

10-26· 95

10·30·'15

07· 19-9(l

11· 10·<)3

01'{)I ·X5

10-26-93

OR·.'IO·95

10-OJ·95

IU·OJ·9.'

10-22-93

10·19 ·9 ,1

IO-2h-9J

10-29·9J

1U-"28-9J

IO-JI -9S

10-21-93

10·27·9)

09-01 ·95

10· 1 J.'13

10·15.93

OR·25·9$

lO·O~-·,}4

03 · 19· 74

11 - IR-93

Table 3. Records ofwelJs (Continued)

Yield (gaUmin)

7

9

15

13

6

X

10

I~

)0

.5.5

II

35

2() 5.7

20

10

10

)0

II

IX

5.5

M

211

12

')

12

~ . 5

X

2U

I

7

15

IS

Pump­ing

period (hour~)

.25

2 .5

,5

,65

2.5

.5

2

.5

,2~

.5 2

,5

3 .5

.5

l.5

I

,5

J

Well tesl daIs

Pump­Ing ",aler

level «(e)

510

~J 2 45

17.7

.170

200

171

141

142

no

50 25,/)

370

190

~~.I

32 110

175

17.3

100

75 .7

170

120

222

115

101. 1

R4

229

67 ~9.1

2()1I

Source of d~la

D

S

D

S o

D

5

D

D

S S

D

D S

D

D

S D

S

D

S D

S

n

D

D

S D

S

D

o

D S

D

[)

Date yield meas­ured

11-{)2-92

10-29·93

02·14-91

10-20·93

01-26·94

11·1 ~·g4

10-22-93

10-06·93

II-I~· 73

0'7-19·90

10·21\·9.1

09-I2-H

01>·1'1·87

10-26-93

09-19·75

119·0R·R8

10·21·93

11·27-79

10-19-93

0~·17·87

10-26·93

05·2R-SS

10·29.93

0).02·87

04-1~-SI

06·20-73

10·21·9)

09-:'0·91

10·27-93

(17-07·82

00·27-91

10·15·93

09·19·73

03·19-74

02·25· 76

Tem­pera­tun.'

tc)

12.0

12.2

10.5

13.5 lUI

11.0

11.5

11.5

15,11

12 u

11.5

11).5

12.U

12.0

9.5

12,0

9.5

9 .5

9.0 10.0

S.5

111,0

10,0

10.1)

10.0

I.l.O 13.0

12.0

10';

10.0

10.5

11.0

10,5

10.5

10.5

II.()

12.0

11.0

10.5

SpN'ific conducl­

ance (IlS/em)

SR I

(>35

594

447

445 621 378 401

-IX7

1.010

n6

400

40R

839

858 1.040

672

1,000

559

54R

SJ2

850

905 88~

SS8 R~5

I. 7~1I

449

53(\

fi21i

65~

844

U40

1.200

75 J

7S~

925

1i19

090

499

Onsite mcasun'menlS

pH (~I"nd­

ard units)

7,7

6,9

9.7

7.9 7,4

7.7

7.9

80 7.9

7.8

7.9

7.S g,O

7.6

70

7,)

7.5

7,7

7.(\

7 .. 1

6.8

7.4

7. 1

6.0

7.4

7,7

7.6 7.S

7.9

6.9

7.7

7.4

7.3 7 ~

7,4

7,1

75

Nltralc (mg/L uN)

2

.\

<.5

2

<5

2

37

<.5

II

I~

)

Source of me~s­

ure­menl

s s

s

[,

S

S

S S

S

s s

s s S s s

5

s s s s

s s s ~

s

s s s

s s s s s

s s s

Dale of mE'asurl'­

menl

IO·2R·95

10-29-93

10·"6-95

08-{)~-96

1(1·22·9~

03-0).94

09-20·95

10-30-95

11 7· 19·QH

10-26-93

()fI·l8 -~~

II·IU·'))

10-26·95

O~-20-%

10-1 .... 93

08·30·95

10':'2-93

10- 19·9.1

0.1-05·94

09·22·95

10-26-93

10·!<)·'I.l

0.1-05·94

10· ) 1-95

08-20-96

10·21-9.1

0~·U)-94

IU·2 7·9~

09·01-95

OR . \ ')-(Jol

1(\·1.1·~'

10-15-9.1

003·05-94

OR·25.95

OX-19.9(,

U7-J0-9/i

QQ-]!;-').'

U~·21-%

11 ·1 R-93

Well num­ber

147

14R

149

150

I S I

IS::!

153

154

155

156

1~7

15~

159

160

11>1

11\2

16.1

11>-1

11>5

161>

1M

1~9

171)

172

17.1

174

TABLE J 67

Table 3. Records of wells (Continued)

Well

num­ber

Location number

115 I I N04W35CCAAOI

17(. It N04W3S0DD,\OI

177 II N05W0.1CAADili

17R II N05W I2CBCAOI

I"" I I N05WDBCADOI

IXO IINO~WI4ADAAOJ

IRI II NOSWI4CABCOI

1~2 IIN05W14fJfJfll)(JI

I~J IIN05WI5DBAAOI

IX4 I I N05W20CADAO I

IX; II N05W21 AAB[)() I

181i I I N()5W21 6CBDOI

18711N05W2KBAAOI

ISM IINII5W2.41X"BDOI

I ~9 II "'05W25B(:CC01

190 II N05W25DBCCOI

191 IlNO~W}5RCCBOI

19~ I I N05WJ5DOBBOI

193 12NII.)W) WBDBOI

19~ 12N0)W3IDDACOI

195 12N03W3JDDOOOI

19(> 12N05WJ40DDAOI

197 12N06W35ACA[l1l1

19.~ 12N06W3_~ArACOI

19Q 12NOf>W)I>BC[)DOI

~OO I 2N06W3IiRDC!;JO I

2(JI I~NO~W)6CADOOI

r Dotc well dcoponed,

Ar~

SG

SG WM

WM

WM

WM

WM

WM

\11M

WM WM WM

\\1M

WM

WM

WM

WM

WM

NH NH NH

WM

WM

WM WM

WM WM

Altitude ot' land ,urfnce

(fl)

Aqulfer code

4.251 211SGVH

~.uo ~IISGVH

5.010 ~20HELN

4.430 ~20HELN

·H30 420HELN

4.550 420HELN

4.800 ·I20H ELN

4/,25 .120H ELN

4_910

6.11611 5,)20

5.7M)

4.570

4.725

4,(i50

4.720

4.620

4 . 2~0

4.120

~ , HO

42(J1-IELN

420SSLP

420MSLD

420MSLD

420SSLP

420SSLP

420SPRD

420SPRD

42HSPRD

420SPKN

420SPKN

.I20SPf(N

4.~90 420HELN

Otpth of ",,'ell

(fe)

161

.100

401

135

360

3S9

186

500

71

590

320 3()0

2.10

187

IIR

390

75

220

360

5J

121

5,\>60 211MRVL 400

5.Q50 211MRVL 24

5.4JU 2 II MRVL 7(1

5.431) 211MRVL 36

5.J60 211MRVL 100

Well completion

Diam· eter of Casing

casing (In.)

Ii

6 4

6

4

6

~

Ii

" 4

Ii

R

I>

4

(-.

4

I:>

4

o

6

{i

4 {i

6

f,

6

I

6

.t

6

I:>

4

mate­rial

P

S

s s p

S P

S

P

S

P

s p

S

P

S

P

s s p

S P

S

P

S

s P

S

P S

P

S

S

S P

S

P

s S p

s S P

Top of casing

(f'l)

10

"05

'-1_0

~o

~1.0

+l.ti

10

~2 4

<)

-'-1.4

b

+::!.o

~o

-<-13

II

"~_7

' ,6 10 -_6

III

+,6

107

+2,U

.,.IA

17

'1.6 I ~

->1_0

10

r,~

-I II ., I.~

9

+20

10

+_6

+1.8

10

7.0

+1.:1

10

68 Hydrology ofrhc Helena Area Bedrock, WeSI-Celltnil Monlana, 199)·98

Bottom of

clIslng (ft)

125

18

401

21

135

20

360

IS

389

2(1

IXu ~O

500

Date well con-

structed

111·0)·77

02·2~-93

O~·21-7'.l

1O.(i1 ·90

07·17-911

1O·02.R6

05·1~·95

:W I O·O!'· k.~

71

• -93

• ·RO 2().4 0~-22·i<4

JOO

2JU

120 0 .1·) I-S7

187

· -~7

22 03·11-86

)90

19 07·0<\·88

75

20 05- 12·94

no

53 OJ.{)l)·72

IS 09-23-92

121

18

450

08· -93

-88 20 07·17·X6

70

18.5 0~·2~·R9

100

Prl-mary

usc of wat.,r

II

Ii II

H

H

H

H

II

H

H

U

H

Ii

II

H

II

H

H

Ii

II

H

~I

H

C

H

H

F

Depth [0

water (fl)

7.1

57, 7~

S9.60

30_95

4744

4H 131 71

142.250

6H9

I') R4

113.01

IILM

')} 23

.79

17_71

17.56

7,4<)

Source of

meas­Urt~

ment

D

s s

s

S

s

D S

S

s

So

s

s

s

s S

S

s s

s s

Dalf of

meas-urc­

ment

01·()\·77

111.(16-95

()k·2'3·9~

10· 15-93

\(I·12-9J

10·1.1-93

• -93

11-10·93

O~-25·95

I 0- l.l-9~

10-13-»)

0~·31 ·95

10-21·93

08·24·95

10-23-95

11·09·9J

II·09·Y3

O~·JO-95

UJ(-J0-95

10-07·93

10·27-'B

10·27-93

Table 3. Records ofweHs (Continued)

Yield (gaUmin)

15

10

IS

20

12

6

4

7.5

10

7

12

20

20

20

25

(.

5

20

~.3

20

1.1

Pump­

ing period (hours)

.5

.5~

2

., 2

.5

2

2 I

.8

I

.5

.25

Well te~t dalU

Pump-

ing waler Source nf

ICI'el data (ft)

4(0.5

160

389

11:1

144

I ~ I

490

61

52.6

291

75.2

380

45

110

62.1

4.10

66

28.5

86

21.9

S

D

D

D

D

D

S

o

D

[)

S

D

D

S

D

s

D

D

D

D ()

S S

D

S

S D

S

Date yield meas­

ured

11-1 R-9J

01-01-77

02-26-93

05·21·79

10-01-90

07-17-90

10 .. 15·9)

10-02-86

05-18-95

10-06-8~

11)..1)·9)

07-26-77

10·13·93

O)·31·S7

10·13·93

0.1-11-86

07.Q6--8R

05-12-94

03-09-72

09·23·92

11-09.9.1

08-03·95

()7·17·~6

\0.07.93

10·27-93

0~·n·g9

10-27-93

Trm­pres­lure (0C)

105

11.5

11.5

12.5

160

12.5

12 ()

13.5

11.0

11.5

1i.5

9.0

11.0

so

11.5

R.5

11.0

?5

9.5

11.5

105

10.5

10.0

110

11.5

9.5

12.0

11.5

Ill.)

9.0

11.0

11.5

9.0

9.0

9.5

7.5

7.5

7.0

~.O

8.U

Specific

conduct­anu

(IlS/em)

510

537

557

388 430

m .1.10 912

359

345

351

422

553

55)

54

318

325 360 569

795

7'.-7

S~7

882 509

504

567

498

500

1.240

1.230

1.120

742

oS! 23~

2J3

258

1::!6

224

219

334

310

Onslte measuremenlS

pH (,Iand­

ud units)

7.8

7A

7.5

7.6

n

7.6

7A

7.4

7.2

7.7

77 7.7

7.4

7.8

10.0

8.1

8.:!

7.)

7.&

7 . .1

7.4

7.5

7.5

7.5

7.6

7.9

7 " 7,.1

7.5

7.7

7.J

7.5

7.5

6.9

6.8 8.1

0.6

7.0

7.0

5.6

65

Source Nitrate or mC1l5- Dole of (mgiL ure- meusur .....

as N) ment ment

<.5

<.5

I

8 9

II

<,5

<5

<,5

2

2

s s s ~

S

s s s

s s s s

s

s

s

s s s s s s s s s s s

s s s

s s s s s s s s s s s S

0).0)·94

00-28--95

09"{)5-96

\0-06--95

OX·2)·95

08-23-95

O~-19-96

08·2~·95

10·15·93

OQ-21-95

U~·19·%

10-12·Y3

ON-I ~-96

j() .. I)·Y)

oR-.l1-95

0~·2S-95

09 .. 0,·96

10-13-93

09·05·96

08·3I-Y5

OR· 10.9(0

IO·IJ.y)

0,--05-94

IIH-11-95

08·19-91>

10·21·9_1

OS-24-95

OX-21-%

IO-2J-9'i

11-09-93

OJ..{)]-Y4

OR·)O·95

OR·20.96

0~-30·95

08':'0-%

0~-.10-95

IO.()7-Y3

09·20·Y5

OR-20-%

10-27-93

1(]·27.93

Well

num­ber

175

176

177

178

17Y

I~O

181

IX2

1~3

1;;7

188

1~9

190

191

192

1'13

194

195

1%

1 \)7

198

199

200

201

TABLE 3 69

Table 4. Records of water levels in selected wells

(Location number described in lex!. Water level--in feet below or above (+) land surface. MS, conditions of meaSllrement. First column (M) is method ofmeasuremenl--G, pressure gage; S, steel rape; T, electric tape: V, calibrated electric lape. Second column (S) is sile status--D, dry: F, flowing; 0, obslnlction: P, pumping: R, recently pumped; W, well destroyed. Symbol: --, no data]

Well Number: 2 Location Number: 09N03W03BCAB01

Date Water MS Date

Water MS Date Water MS Date

Water MS level level level level

SEP 06, 1995 214.63 V MAY 21, 1996 211.79 S OCT 21,1996 215.45 S FEU 28, \997 214.10 S

JAN 23, 1996 216.40 V JUN 24 217.09 S NOV25 214.46 S MAR 27 214.12 S FEB 21 218.79 S JUL 23 216.05 S DEC 30 214.02 S APR 21S 214,28 S MAR 20 213.24 S AUG 19 214,17 S .IAN 28,1997 213.86 S APR 22 221 .25 S SEP 30 2)1.09 S

Well Number: 4 Location Number: 09 N03W04CDAAO 1

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

SEP OS, 1995 364.64 S MAR 20,1996 360.88 S SEP 30,1996 372.21 S FEB 28, )997 365,44 S OCT 30 3M.65 S APR 22 355.86 S OCT 22 398.37 S MAR 27 35R.02 S NOV 27 367.19 S MAY21 351.87 S NOV 26 351.87 S

.IAN 23. 1996 369.02 S JUN 24 36f<.90 S DEC 30 384.49 S FER 21 357.99 S AUG 19 354.78 S JAN 28. 1997 359.7& S

Well Number: 5 Location Number: 09N 03W05ABAA01

Date Water

MS Date Water

MS Date Water

MS level level level

OCT 06,1995 274.4 S JAN 23,1996 297.37 S MAR 20,1996 356.24 S

30 291. 70 S FEB 21 303.99 S NOV 27 292,27 S

Well Number: 6 Location Number: 09N03W05ABD CO 1

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

SEP OS, 1995 281.32 S FEB 27. 1996 297.08 S JUL 2),1996 309.92 S DEC 30,1996 332.0R S

OCT 30 284.8.1 S APR 22 309.34 S AUG 19 357.80 S JAN 28, 1997 338.09 S NOV 27 284 .97 S MAY 21 296.19 S SEP 30 282.99 S FEB 28 354.17 S

JAN 23. 1996 293.89 S JUN24 297.81 S NOV 25 297.78 S MAR 25 352.19 S

70 Hydrology of 11t~ Helena Area Bedrock., Wcst·Central Mont~ng, 1993-98

Table 4. Records or water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 8 Location Number: 09N03W07CBCC01

Water MS

Water MS Date

Water MS Date

Water MS Date

level Date

level level level

OCT 06,1995 39.35 S MARlO,1996 32.03 S AUG 19. 1996 34.24 S JAN 2Fi , 1997 32.69 S

30 32.22 S APR 22 28.88 S SEP 25 35.34 S FEB 27 31.29 S NOV 27 32.20 S MAY 21 29.59 S OCT21 32.95 S MAR 25 31.13 S JAN 23. 1996 32.54 S JUN 24 28.83 S NOV 26 34 .23 S MAY02 31.79 S FEB 21 32.30 S JUL 24 62.83 SP DEC 30 34 .88 S

Well Number: 9 Location Number: 09N03W09ABBC01

Date Water

MS Date Water MS Date

Water MS Date

Water MS level level level level

SEP OS, 1995 117.73 S MAR 20,19% 117.58 S AUG 19, 1996 120.97 S JAN 28, 1997 159.88 S OCT 30 127.08 S APR 22 106.84 S SEP 30 150.86 S FEB 28 157.41 S NOV 27 J3 1.09 S IvIAY21 92 .89 S OCT 21 190.38 S MAR27 164.64 S JAN 23. 1996 128.40 S fUN 24 117.39 S NOV 25 167.67 S APR 28 172.81 S FEB 21 126.85 S JUL 23 167.86 S DEC 30 189.69 S

Well Number: 11 Location Number: 09N03W11 BCBA01

Date Water

MS Date Water

MS Date Water

MS Date Water MS level level level level

OCT 22,1993 45. 14 S OCT 26.1994 44.64 S SEP 19, 1995 47.99 V SEP 30, 1996 45 .52 S DEC 20 45.59 S NOV21 47.15 S OCT 24 48.19 S OCT21 45 .51 S JAN 19. 1994 45.68 S DEC 20 47.11 S NOV 27 4&.53 S NOV 18 45.48 S FEB 23 45.79 S JA.t\l 24. 1995 47.17 S JAN 23.1996 48.28 S DEC 30 46.57 S MAR 22 45.95 S FEB 22 47.48 S rEB 21 47.&8 S JAN 28, 1997 45 .01 S APR21 45.62 S MAR 20 47.20 S MAR 20 40.93 S FEB 28 47 .95 S MAY 25 45.47 S APR26 47.4 ) S APR 22 43.33 S MAR27 45 .01 S JUN 20 48.24 S MAY 22 47.15 S MAY 21 44.03 SR APR 28 45.0<} S JUL 20 46.20 SR JUN2Fi 47,80 SP JUN 24 44.16 S AUG 30 48.29 SP JUL 25 4R.49 VP JULD 45.25 S $EP 19 47.17 S AUG 21 47.62 V AUG)9 45.35 S

TABLE 4 7!

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 12 Location Number: 09N03W14DACC01

Date

OCT 20,1993

DEC 20 JAN 19, [994

FEB 2J

MAR 22 APR 2[

MAY25 JUN 20 JUL20 AUG 30

SEPI9

OCT 26 NOV21 DEC 20

Water level

22.98

20.33 20.41

20.51

20.46

19.98

19.62 20.11 20.80 21.27 21.49

20.99

21 .04

21.02

MS Date

S JAN 24, 1995 S FEB 22

S MAR 20 S APR 26

S MAY 22 S JUN 27 S JUL 25 S AUG 21 S SEP[9

S OCT 24

S NOV 27 S JAN 23,1996 S FEB 21 S MAR 20

Water level

20.89

20.84 20.75 20.39

19.69

19.79

20.81

21 .02 21 .00

20.98

21.34

21.77 21.98

20.38

MS Date

S APR 22. 1996 S MAY 21 S JUN 24

S JUL 23 S AUG 19 S SEP 30 V OCT 21

V NOV [8

S DEC 30 S JAN 28, [997 S FEB 28 S MAR 25 S APR 28

S MAY 30

Well Number: 14 Location Number: 09N03W17DBC 01

Date

DEC 20,1993

JAN [9,1994

FEB 23 MAR 22

APR 21

MAY 25 JUN 20 JUL 20 AUGJO SEP 19

OCT 26 NOV21

DEC 20

JAN 24, 1995

Water level

30.03 31.94

31.02

30.28 28.94

25.22 28.06 27.i<!)

29.64

31.06 31.59 ) 1.93

32.05 32.09

MS Date

S FEB 22, 1995 S MAR 20

S APR 26

S MAY 22 S JUN 27 S JUL 25

S AlIG21 S SEP 19

S OCT 24 S NOV 27

S JAN 23, 1996

S FEB 21 S MAR 20 S APR 22

Water level

31.75

31.78 31.59

28.47

30.99 31.05

32.06

32.16 32.46

32.52 31.55

31.00 29.52

29.28

MS Date

S MAY 21,1996 S JUN 24

S JUL 23 S AUG 19

S SEP 30

V OCT 21 V NOV 18

S DEC 30

S JAN 28. 1997 S FEB 28 S MAR 27 S APR28 S MAY 30 S JUN24

Well Number: 15 Location Number: 09N03W23BDDD01

Date

OCT 18,1993

JAN 19, 1994

MAR 24 APR 2[ MAY 26 JUN 20 JUL 20 AUG 30

SEP 19

Water level

MS

+73.15 G

+83.76 G

+84.92 G +84 .92 G +72.90 G

+73.26 G

+73.01 G +73.26 G

F

Date

OCT 26. 1994 NOV 21 DEC 20

FEB 22,1995

APR 26

JUN 28

JUL 25 AUG 21

SEP 19

Water level

+73.12

+73. 19 +73.01

+73.72

+73.71

MS

G G

G

G

G +73.02 G

+69.44 G +47.40 G

+62.11 G

Date

OCT 24,1995 NOV]7

JAN 22, 1996

FEB 21

MAR 20 APR 22 MAY21 JUN24

JUL 23

72 Hydrology of «Itt Helena Area Bedrock. West-Cenlral Montana, 1993-98

Water level

20.05 19.92

20.75

21.02 22.28 21 .29 21.26 22.01

21.02 20.83

20.71 20.65

21.61

19.47

Water leval

28.98 28.44

30.05

31.38 31.41

31.92

31.94

32.08 3 I. \3

31.35

30.17 30.64 28.25

32.01

Water level

+68.29

+72.90

+ 73.02 ~·50. 64

+72.79

+72.79

+49.48

+50.87

MS Date

S JUN 24. 1997 S JUL 28

S AUG 25 S SEP 23

S OCT 30 S NOV 25 S DEC 17 S JAN 29, 1998

S FEB 24

S APR 01

S 28

S MAY 27 S

S

MS Date

S JUL 28, 1997

S AUG 25 S SEP 23

S OCT 30 S NOV 25 S DEC 17

S JAN 29. 1998

S FEB 24 S APROI S 28

S MAY 27 S

S S

MS Date

G AUG 19. 1996 G SEP 30

o OCT 21 G NOV 18 G DEC 30

G JAN 28. 1997 G FEB 28 G MAR 27

G APR 28

Water level

20.13

39.44

21.89

33.70 25.77 23.19 21.23 21.13 23.51 22.91

24.89 24.37

Water level

30.24 3162

32.13

31.23 32.22

32.13

32.41

32.59

32.21 31.51

32.27

Water level

+50.75 +50.75

+70.&3

+73.59

+61.83

+39.45 +70.83

+69.90

MS

S SR S

S

S

S S

S

S

S

S S

MS

s S

S

S S S S S

S

S

S

MS

G

G

G G G

G

G

G

o

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 17

Date

SEPT 07. 1995

OCT 31

NOV27

JAN 23, 1996

FEB21

Water level

7l.37

71.88

71.75

71.83

71.99

Well Number: 19

Date

NOV 17, 1993

JAN 19,1994

rEB 23

MAR22

APR 22

MAY 26

JUN20

.nJL20

AUG 30

SEPI9

Water level

33.24

35.60

26.05

32.85

24.69

30.84

33.71

36.76

43.02

43.17

Well Number: 21

Date

OCT 13. 1993

DEC 20

JAN 19, 1994

FEB 23

MAR 22

APR21 MAY25 JUN 20

JUL 20

AUG 30

SEP 20

OCT 26

NOV21

DEC 20

Water level

16.25

I S.41

18.19 19.01

IS.93

17.53

16.41 16.89

18.77 21.62

22.45

22.97 21.64

22.81

Location Number: 09N04W09DDAC01

MS Date

S MAR 20. 1996

S APR 22

S MAY 21 S JUN 25

S JUL 24

Water level

72.11 71.73

71.43

70.94

71.01\

MS Date

S AUG 19. 1996

S SEP 26

S OCT 22

S NOV 25

S DEC 30

Location Number: 09N04W10CBBA01

MS

s s s S S

S

S

S

S

S

Date

OCT 26,1994

NOV21 DEC 20

JAN 14, 1995

FEB 22

MAR 20

APR26

MAY 22 JUN 28 JUL 25

Water level

MS

35.42 S

34.73 S 34.86 S

39.91 S

40.35 S 41.47 S

38.53 S

36.65 S 39.64 V 42.54 V

Date

AUG 21, 1995 SEP 19

OCT 24

NOV 27

JAN 23. 1996

FEB 21

MAR 20

APR 22

MAY11 JUN25

Location Number: 09N04W11 CCCB01

MS Date

S JAN 24. 1995

S PEB 22

S MAR 20

S APR 26

S MAY 12 S JUN 27

S JUL 25

S AUG 21 S SEP 19 S OCT 24

S NOV 27

S JAN 23, 1996

S FEB 21 S MAR 20

Water level

22.83

22.48

21.96

21.57

18,50

18.13

18.69

20.&7

22.06

22.51

22.52 22.71

23.09

2UO

MS Date

S APR 20, 1996

S MAY 21

S JUN 24

S JUL24

S AUG 19

S SEP 26

V OCT21

V NOV 25 S DEC 30

S JAN 28.1997

S FEB 28

S MAR2S

S MAY 02

S JUN 24

Water level

71.1 R 70.34

71.46

71.46

71.65

Water level

46.55

48.31

49.08

49.71

47.23

50.06

50.20

43.28

41.96

42.97

Water level

19.10

IS.21 18.00

27.51 21,78

23.26

23.58

23.71

23.71

23.n 23.74

23.02

20.98

20.60

MS Date

S JAN 28. 1997

S FEB 28

S MAR 26

S MAY 02

S

MS Date

VR JUL 24, 1996

S OCT04

S 22 S NOV 27

S DEC 30

S JAN 28.1997

S FEB 28

S MAR 25

S MAY 02

S

MS Date

S JUL 28, 1997

S AUG 25 S SEP 23

S OCT 30

S NOV 25 S DEC 17 S JAN 29. 1998

S FEB 24

S APR 01

S 2H S MAY 27

S

S

S

Water level

72.68 71.77

73.17

73.03

Water level

47.76

56.54

57.77

5S.99

59.01

57.21

60,13

55.61

50.34

Water level

21.18 22.43

22.51 23.68

23.81

23.63

24.00

24.04

22.59

20,21

IR.38

MS

s S S

S

MS

s s s s s s s s S

MS

S

S

S

S S

S

S S

S

S S

TABL£ 4 73

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 22 Location Number: 09N04W11CDBD01

Date

OCT 14. 1993

DEC 20

JAN 19. 1994

FEB 2.1

MAR 22 APR21 MAY 25

JUN 20 JUL20 AUG 30

SEP 19

OCT 26 NOV21 DEC 20

Water level

MS

68.14 S

67.39 S

66.26 S

65.93 S

67.72 S 65 .22 S

65.72 S 62.64 S 64.88 SP 61.70 S

61.68 S 61.49 S

61.82 S

6n.07 S

Date

JAN 24,1995 FEB 22

MAR 20 APR 26 MAY 21 JUN 27

JUL 25

AUG21

SEP 19 0(T24 NOV 27

JAN 23 . 1996

FEB 21

MAR20

Water level

MS

62.29 S 62.55 S

62.55 S

63 .80 S

62.77 S 61 . 11 S 61.92 V 63.26 V

62.04 S 62 . 13 S 62.47 S

62.82 S

59.30 S 63.16 S

Date

APR 21.1996

MAY21 ruN 24

JUL 24 AUG 19 SEP 26 OCT 21

NOV 25

DEC 30

JAN 28, 1997

FEB 28 MARlS

MAY02

JUN 24

Well Number: 24 Location Number: 09N04W12BDCA01

Date

AUG 25. 1995

OCT 30 NOV 27 JAN n 1996

FEB 21

Water level

28.88 28.66

28.33

27.89 29,35

Well Number: 27

Date

SEP 05, 1995

OCT 30 NOV 27 JAN 23,1996

FEB 21

Water level

18.36 19.28 18.48 20,91

22.16

Well Number: 29

Date

SEP 07. 1995

OCT 31

NOV27

JAN 23. 1996 FEB21

Water level

18 .37 18.37 18,24

18.74

18,07

MS Date

S MAR 20. 1996

S APR 22

S MAY 21 S JUL 24

S AUG 19

Water level

27,79

25.81 26,21

28,66

28.49

MS Date

S SEP 26, 1996

S OCT 21

S NOV 25

DEC 30

S JAN 28. 1997

Location Number: 09N04W15ADDB01

MS Date

S MAR 20, 1996

S APR 22

S MAY 21 S 1UN 24

S JUL 24

Water level

19.37

20,28

lJ ,89

14.87

17.86

MS Date

S AUG 19, 1996 SR SEP 26 S OCT 21

S NOV 25

S DEC 30

Location Number: 09N04W16AAAB01

MS Date

S MAR 20. 1996 S APR 22

S MAY 21

S JUN 25 S JUL 24

Water level

18.38

16.04

16.46

15.97

16.88

MS Date

S AUG 19. 1996 S SEP 26

S OCT 22 S NOV 26

S DEC 30

74 H)'drology of the HeleDIi Ar~B Bedrock. West-Central MonUina. 199:3-98

Water level

MS

61.91 S

61.06 S 65.57 S 61.40 S

61.63 S

61.66 S 62.00 S 63.36 S 6J . 13 S 63.27 S

63.39 S 63.65 S 65.21 S

64.18 S

Date

JUL 28,1997

AUG 25 SEP 22 OCT 30 NOV}5

DEC 17

JAN 29. 1998 FEB 24 APROI

28 MAY 27

Water level

MS Date

28.92 31.19

32.88 27.25 27,17

Water level

17.13

17.64 18.78 21.97

17,94

Water level

18,10

18,04

18.18 18.29

18.51

S FEB 27. 1997

S MAR 25

S MAY 02

S S

MS Date

S JAN 28, 1997

S FEB 28 S MAR 25 S MAY 02

S

MS Date

S JAN 28, 1997 S FEI) 28

S MAR 26 S MAY 02

S

Water level

MS

65.49 S 6),82 S

62.83 S 65 ,25 S (i5 .58 S 65,65 S

66,04 S

66.18 S 66.63 S 67,02 S

67,82 S

Water level

26.72 25.26 29.10

Water level

17.83

17.71 17.43

17.50

Water level

18,74

18,63 1().96

17.02

MS

s S S

MS

s s S

S

MS

s S

S

S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 30

Date

OCT 14.1993

DEC 20

JAN 19. 1994

FEB 23

MAR 22 APR 22

MAY 26

JUN 20

JUL 20

AUG 30 SEP 19

Water fevel

70.40

7 1.96

66.21

65.40

65.59

65.78

62.20

61.22

59.62

58.50

58.30

Well Number: 31

Date

SEP 07. 1995

OCT 30

NOV 27

JAN 23. 1996

FEB 21

Water level

35.30

36.00

36.79

35.51 34.82

Well Number : 32

Date

NOV 09. 1993

DEC 20 JAN 19, 1994 FEB IS

23 MAR22

APR22

MAY 26

JUN 20 JUL 20

AUG 30

Water level

32.47

32.89

32.90 33.06

33.32

33 .07

32.8 1

30.05

J 1.82

) 1.41

)3.02

Location Number: 09N04W16BACB01

MS Date

S OCT 26, 1994

S NOV 21

S DEC 20

S JAN 24. 1995

S FEB 22

S MAR 20

S APR 26

S MAY 22

S RJN 28 S JUL 25

S AUG 21

Water fevel

58.12

55.98 57.59

57.72

57.74

5!!.47

58.07

58.26 57.39

57.89

57 .50

MS Date

S SEP 19, 1995

S OCT 24

S NOV 27

S JAN 23. 1996

S FEB 21

S MAR 20

S APR 22

S MAY 21

V .1UN 24 V JUL 24 V AUG 19

Location Number: 09N04W16DDAB01

MS Date

S MAR 20. 1996

S APR 22

S MAY 21

S JUN 24

S JUL 24

Water level

36.1 I

33.74

31.58 33.38

37.73

MS Date

S AUG 19, 1996 S SEP 26

S OCT 21

S NOV 25

S DEC 30

Location Number: D9ND5WD3AACCD1

MS

s S

S

S S

S

S S S

S S

Date

SEP 19. 1994 OCT 26

NOV21

DEC 20

JAN 24, 1995

FEB 22 MAR 20

APR 26

MAY22

JUN 27 JUL 25

Water level

MS

32.56 S

32.90 S 33.18 S

33.21 S

33.17 S 32.99 S 32.&8 S 32.59 S

J 1.34 S

32.45 V

28.98 S

Date

AUG 22, 1995

SCPI9

OCT 24

NOV27

JAN 23, 1996

FEB 21

MAR 20

APR 22

MAY 22 JUN 25 nIL 25

Water level

58.15

58.04

58.95

58.21

65.70

62.26

58.43

57.88

60.29

57.82

68 .64

Water level

32.62

35.28

34.96

35.09 35.12

Water level

35 .72

32.83 32.33

32.77

32.66

32,36

32.29

32.09

31.48 18.44

27.94

MS Date

S SEP 26. 1996

S OCT 22 S NOV 26

S DEC 30 S JAN 28. 1997

S FEB 28

S MAR 25

S MAY 02

S S

S

MS Date

S JAN 28, 1997

S FEB 28 S MAR 25

S MAY 02 S

MS Date

VR AUG 20. 1996 S

s SEP 24 OCT 22

S NOV 27

S DEC 26 S JAN 29. 1997

S fEB 25 S MAR 25

S APR 26

S

S

Water level

58.67

57.40

57.76

58 .32

58.35

58.41

61.54 58.81

Water level

35.39

36.82

35 .20 35.21

Water level

30.49

32.21

32.67

)),08

3314

33.26

33.11 32 .Q3

3246

MS

s s S S

S S S

S

MS

S S S S

MS

s s S S

S S S S

S

TABI.E 4 75

Table 4. Records of water levels, Helena area bedrock. west-central Montana (Continued)

Wef( Number: 34 Location Number: 09N05W12ACAD01

Date

OCT 14, 1993 DEC 20 JAN 19,1994 FEB 23

MAR 22 MAY 25

JUN 20

JUL 20

AUG30

SEP 19

Water level

35.26

34,94

35 ,14

35.46

34.84

37.20

45.77

38.69

41.66 41.83

MS Date

S OCT 26. 1994

S NOV 21

S DEC 20

S JAN 24 . 1995 S FER 22

S MAR 20 SP APR 26

S MAY 22

S JUN 27

S JUL 25

Water level

38.75

38.04

37.69

38.33

36.61

36.25

36.24

35.63

37.95

40.04

MS Date

S AUG 21 , 1995

S SEP 19 S OCT 24

S NOV 27

S JAN 23, 1996

S FEB 21

S MAR 20

S APR 22

SR MAY 22

V JUN 25

Well Number: 35 Location Number: 09N05W12CCDA01

Date

OCT IS, 1993

DEC 20

JAN 19, 1994

FEB 23

MAR 22

APR 22

MAY 25

JUN 20

JUL2I AUG ]0 SEP19 OCT 26 NOV 21

DEC 20

Water level

30.52

31.57

27.51

29.18

28.84 26.69

27.09

27.06

27.R9

27.64

28.82

28.09

28.73

30.91

MS Date

S JAN 24, 1995 S FEB 22

S MAR 20

S APR 27

S MAY 22

S JUN 27

S JUL 25 S AUG 21

S SEP 19

S OCT 24

S NOV 27

S JAN 23, 1996

S fEB 21

S MAR 20

Water level

29.61

28.63

28.91

28,44

28,47

27.10

2!U5 66.37

31 .80

27.44

28.26

28.58

27.57

26.50

MS Date

S APR 22, 1996

S MAY 22

S JUN 25

S JUL 25

S AUG 20

V SEP 24

V OCT 22

VP NOV 25

S DEC 26

S JAN 29, 1997

S FEB 27

S MAR 25

S APR 26

S JUN 24

Well Number: 38 Location Number: 09N05W21ACBA01

Date

NOV 16. 1993

DEC 20

JAN 19, 1994

FEB 23

MAR 22

APR22

MAY 25

JON 20

JUL 20

AUG 30

SEP 19

Water level

25.47 26.34

27.62

29.00

MS

s s s s

29.21 S

26.49 S

17.86 S 19.91 S

22.05 S

28 ,54 S

25.12 S

Date

OCT 26, 1994

NOV2) DEC 20

JAN 24, 1995

FEB 22

MAR 20

APR 26 MAY 22

JUN 26 JUl25

AUG21

Water level

28.26

29. 18 30.42

30.97

31.26 31.39

28.63

22.45

MS

S

S S S S S S S

18.35 V

20.10 V

21.87 V

Date

SEP 19, 1995

OCT 24 NOV 27

JAN 23, 1996

FEB 21

MAR21

APR 22 MAY2)

JUN 25

JUL 25 AUG20

76 Hydrology of rh~ Helens Area Bedrock. West-Central Montallll, 1993-98

Water level

39.26

41 .52

37.51

38.16

38.21

35.47

34.34

33.06

33.78

34.22

Water level

22.68

21 .84

23.08

28,45

28.54

25 .91

25.17

25.37

25.48

25 ,37 25 . 13

24.59

21.51 22.87

Water level

23.68

26.46

25 .63

27 ,28

27.08

27.34 24.97

23.17 IR.99 20 ,47

22.17

MS Date

V JUL 26. 1996

S AUG 20 S SEP 24

S OCT 22 S NOV 27 S DEC 26

S JAN 29, 1997

S FEB 25

S MAR 25 S APR 26

MS Date

S JUL 28, \997

S AUG 25

S SEP 23

S OCT 30

S NOV 25

S DEC 17 S JAN 29, )998 S FEB 24

S APR 01

S 28 S MAY 27

S

S

S

MS

s S S

S

S

S

S

S S

S

S

Date

SEP 24, 1996

OCT22 NOV 27

DEC 26

JAN 29, J997 FEB 28

MAR2S APR26

Water level

42.60

44.32

41.95

39.44

41.13

39.44

47.77

3&.67

36.35

37 .90

Water level

27.62

41.3.5 39.69

25 ,53 3506

25.38

23.05

40.24

27.84

25.29

27.62

Water level

24.09

25.45

27.83

28.26

28.49

2S .60

27.93

26.54

MS

S

S S S S S S S

S

SP

MS

S

S S S S S

S S

S S S

MS

s S S S S S S S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 39 Location Number: 09N05W29DDCC01

Date

SEP 21,1995

ocr 31 NOV 27

JAN23. 1996

Water level

MS

64.63 S

24.42 S 13.19 S

23.98 S

Date

FEB 21,1996

MAY 22

JUL 25

AUG 20

Water level

MS

27.99 S 21.34 S 38.01 S 23.53 S

Date

OCT 22,1996

NOV 25

DEC 26

JAN 28. 1997

WeI! Number: 40 Location Number: 09N05W29DDCC02

Date

SEP 2 L 1995

MAR 21. 1996

Water level

27.23

27.54

Well Number: 41

Date

SEP 26. 1995 NOV 28

JAN 23, 1996

Water level

11.71

12.18 12.53

Well Number: 46

Date

OCT 22,1993

DEC 20

JAN 19, 1994

FEB 23 MAR 22

APR21

MAY 25

JUN20

JUL 20

AUG 30 SEP 19

OCT 26

NOV21 DEC 20

Water level

40. 17

42.40

43.04

44 . 12

44.87

44.99

44.55 46.23

44.21

43 .21

4L84

41.45

42.70

42 .79

MS Date

S APR 22 . 1996

S JUN 25

Water level

25.77

25.90

MS Date

S SEP 24.1996

S MAR 25, 1997

Location Number: 09N05W33CDCC01

MS Date

S AUG 20. 1996 S SEP 23

S OCT 22

Water level

12.60

13.77

13.03

MS Date

S NOV 25, 1996

S DEC 26

S JAN 29, 1997

Location Number: 10N03W20CCAA01

MS Date

S JAN 24, 1995

S FEB 22

S MAR 20

S APR 26

S MAY 22

S ruN 27

S JUL 25

S AUG 21 S SEP 19

S OCT 24

S NOV 27

S JAN 23, 1996

S FEB 21

S MAR 20

Water level

43. 13

43.47 43.61

43.77

42 .04

41.37

39.87

40.12

39.62

39.77

34.36 41.19

40.97

41 .26

MS Date

S APR 22,1996

S MAY 21

S JUN 24

S JUL 24

S AUG 19

S SEP 25 VP OCT 21 C NOV 27

S DEC 27

S JAN 23, 1997

S FEB 27 S MAR 24

S APR2R

S MAY 30

Water level

MS Date

33.06 S

75.40 S 66.50 S 24.08 S

FEB 15, 1997

MAR 25

APR 26

Water level

23.59

27.07

Water level

12 .69

13.29 14.90

Water level

40.99

40.49

39.57

39.66

40.02

39.56

40.06

41.71

41.25

41.80

40.39

40.66

41.24

40.85

MS Date

S APR 26. 1997

S

MS Date

S MAR 25. 1997

S APR 26

S

MS Date

S JUN 25, 1997

S JUL 28

S AUG 25

S SEP 23

S OCT 30

S NOV 25 S DEC 17

S JAN 29. 1998

S FEB 24

S APR 01

S 28 S MAY 27 S S

Water level

MS

22.12 S

22.83 S

17.94 S

Water level

32.56

Water level

13 .05

11.30

Water level

49.51

37.85

38 .21

38.22

38.61

39.12

40.23

40.68

41.19

41.71

40.89

MS

s

MS

S

S

MS

S S

s S

S

S S S

S S

S

P

TABLE 4 77

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 50 Location Numbe.r : 10N03W28CCCC01

Date Water

MS Date Water

MS Date Water

MS Date Water MS

level level level level

OCT 18.1993 18.09 S OCT 26.1994 20.74 S SEP 19, [995 43.79 SP SEP 25, 1996 26.44 S DEC 20 [ 8.55 S NOV21 18.89 S OCT 24 19. 19 S OCT 21 20.38 S JAN 19. 1994 18.93 S DEC 20 19.05 S NOV27 19. 15 S NOV 27 20.49 S FEB 23 19.26 S JAN 24, 1995 19.46 S JAN 23.1996 19.58 S DEC 30 19.59 S MAR22 21.13 S FE922 19.72 S FEB21 19.72 S JAN 23. 1997 19.59 S APR 21 23.49 S MAR20 19.85 S MAR20 19.26 S FEB 27 19.55 S MAY 25 22.01 S APR 26 20.01 S APR 22 19.85 S MAR 24 19.89 S ruN 20 34.17 SR MAY 21 19.72 S MAY 21 20.58 S MAY 06 20.13 S

JUL 20 27.48 SR .rUN 27 20.25 S JUN 24 23.45 S AUG 30 28.16 SR JUL 25 23 .18 S JUL 23 23.10 S SEP 19 29.55 S AUG21 33.17 SP AUG 19 24.36 S

Well Number: 51 Location Number: 10N03W29BDCC01

Date Water MS Date

Water MS Date Water MS Date

Water MS level level level level

SEP 21. 1995 29.84 S MAR 20. 1996 41 .54 SR AUG 19, 1996 33.19 S .IAN 23. 1997 23.73 S OCT 30 27.45 S APR 22 24.41 S SEP 25 32 . 1.~ S FEB 27 24.59 S NOV 27 26.27 S MAY21 24.97 S OCT 22 30.50 S MAR 24 24.93 S JAN 23,1996 18.02 S JUN 24 27.23 S NOV 27 28.07 S MAY 06 24.53 S FEB 21 24.63 S JUL 2J 33.78 S DEC 27 27.57 S

Well Number: 53 Location Number; 1 ON03W31 CBBD01

Date Water

MS Date Water

MS Date Water MS Date

Water MS level level level level

OCT 22.1993 46.83 S JUL 20. 1994 50.72 S MAR 20. )995 50.39 S NOV 27, 1995 48.8\ S

DEC 20 48 .13 S AUG 30 4994 S APR 26 50.38 S JAN n 1996 50. 19 S

JAN )9. 1994 48 .91 S SEP 20 51.24 S MAY22 50.)0 S FEB 21 44.97 S FEB 23 49.49 S OCT 26 5t .20 S .IUN 27 48 .77 S MAR 20 43.39 S

MAR22 50.38 S NOV21 51.23 S JUL 25 47.60 V APR 22 46.49 S

APR 21 50.69 S DEC 20 50.75 S AUG 21 46.70 V MAY21 W

MAY 25 50.57 S JAN 24, 1995 50.42 S SEP 19 42.53 S JUN20 50.78 S FEB 22 50.50 S OCT 24 46.09 S

78 Hydrology of ltle Helena Ar~a Bedrock.. Wt'1it-Ccntral Montana, 199:3-98

Table 4. Records ofwaler levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 55 Location Number: 10N03W32BCBD01

Date

NOV 09, 1993

DEC 20

JAN 19, 1994

FEB 2J

MAR 22

APR 21

MAY 25

JUN 20

JUL 20

AUG30

SEP 19

OCT 26

NOV21

DEC 20

Water level

38.S3 41.07

41 .56

38.01

41.79

43.09

40.82

41.13

46.13

39.41

40,62

41.75

35 .29

41.89

MS Date

S JAN 24, 1995

S FEB 22

S MAR 20

S APR 26

S MAY 22

S JUN 27

S JUL 25

S AUG 21

SR SEP 19

S OCT 24

S NOV 27

S JAN 23, 1996

S FEB 21

S MAR 20

Water level

44.50

44.44

45.10

45.63

39.92

38.55

37.70

40.02

38.45

38.97

41.49

43.20

42.65

42 .40

MS Date

S APR 22, 1996

S MAY21

S JUN 24

S JUL 23

S AUG 19

S SEP 25

V OCT21

V NOV 27

S DEC27

S JAN 23, 1997

S FEB 27

S MAR 24

S MAY 06

S 30

Well Number: 58 Location Number: 10N04W02BACB01

Water MS Water MS Date level Date level

MAY 10, 1993

JUN 04

SEP 05

MAR 04,1994

APR 17

48.34 S

48.09 S

47.45 S 47,33 S 47.44 S

MAY 22,1994

JUN 07

JUL 03

AUG 03

SEP 07

47.61 S 47,70 S

48.55 S 49.49 S 50.08 S

Date

OCT 06, 1994

DEC 16

FEB 21,1995

APR 21

MAY 31

Well Number: 59 Location Number: 10N04W02CABA01

Date

APR03 , 1992

29

MAY 28

JUL 29 AUG31

SEP 28

OCT 31

FEB 03. 1993

MAR03

30

Water level

MS

50.24 S

50.40 S

50,82 S

51.35 S

51.67 S 51.83 S

51.78 S 51.96 S

52.04 S

51.32 S

Date

MAY 10, 199)

JUN02

JUL II

AUG 07

SEP06

OCT 05

NOV 13

DECOR

FEB 02,1994

MAR 03

Water level

MS

51.50 S

50.63 S

48,94 S

48.59 S 48.34 S

48.37 S 48.57 S 48.91 S

49. 16 S

49.39 S

Date

APR 10. 1994

MAY 20

IUN 07

IUL03

AUG 03

SEP 08

OCT 06

NOV 16

DEC 09

FEB 21. 1995

Water level

MS Date

40.41

40.17

38.55

38.47

38.81 38 ,811 39,62

41.49

42.62

42 .77

42 .58

42 .51

43.49

42.46

S JUN 24, 1997

S JUL 28 S AUG 25

S SEP 23 S OCT 31 S NOV 25

S DEC 17

S JAN 29, 1998

S FEB 24

S APR 01

S 28

S MAY 27

Water level

S S

MS

50.06 S

49.84 S 50.06 S 50.25 S 50.44 S

Water level

MS

49.65 S 48.64 S 47.76 S 47.33 S 48. 15 S

49.05 S

49.40 S

49.44 S 49.63 S

50.02 S

Date

JUL 18, 1995

SEP 06

DEC 14

JUL 30, 1996

Date

APR 13, 1995

MAY31

IUL 18

SEP 06

DEC 14

APR 18, 1996

JUL 28 MAR 15, 1997

Water level

39.83

37.06 37,61

33. 17

29.29

40.48

41.35

42.88

43 .70

44 .23

44.48

43.99

Water level

MS

S

S

S S S S

S

S

S

S S S

MS

50.58 S

51.85 S 51.19 S 51.36 S

Water level

MS

50.32 S 49.72 S

45.90 S 47.84 S 48.95 S

48.55 S 46.95 S 46.74 S

TABLE 4 19

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 60

Date

NOV 14, 1976 DEC 26 JAN )0, 1977 MAR 06 APR 10

MAY 08

ruL02

AUG 14

OCT 15

DEC 04

IAN 14.1978 FEB 20

MAR 19 MAY 09

JUN 17 ruL 10

SEP 04 OCT 13

FEB 11, 1979 MAY 26 ruN 30 SEP 02 NOV 04

DEC 02

FEA 03. 1980

MAROS APR IJ MAY04

Ol

.fUN 28 JUL 27 AUG 30

OCT 19 NOV 30,1980

JAN 24, 1981 MAR 07

APR 19 MAY 23

30 JUN 21 AUG 08 SEPI2

OCT 03 NOV II

DEC 24

FEB 15, 1982 MAR 28 APR 24 MAY23

Water level

25.37

26. \0

26.80 27.38 28.01 28.45 29.10 29.66 30.56 31.20 31.79

32.37

29.68

29.32 28.76 27.90

27.61 21U2 31 .20

24.72

23.76 23.88 25.15 25.60 26.88 27.48

27.94 28.48 27.12

25.21 23.94 23.38 23.10

23.3n 24.20 25.05 25.95 23.66 18.46 12.18 13.35 15.59 17.09

18.95 20.72

22.49 22.85 22.70

22.61

Location Number: 10N04W02CBAA01

MS Date

S JUL 27,1982 S SEP 25 S DEC 03 S JAN 16, 1983 S FEB 19

S APR 16

S MAY 10 S JUN 02 S 18

S JUL II S AUG 07 S SEP 25 S OCT 30 S JAN 01, 1984 S FEB 19 S APR 21 S MAY 27 S IUL 0 I. 1984 S SEP09 S NOV II

S JAN 26. 1985 S MAR3) S MAY 19 S JUL 04 S 26 S 27 S SEP 28

S DEC 26 S MAR 09, 1986

S MAY 25 S JUL 13 S SEP 28 S NOV 16 S FEB 01,1987 S APR 26 S JUL 03 S 25 S OCT 12

S DEC 15 S MAR 29, 1988

S MAY 17 S .IUN 17 S JUL 17 S SEP 01

S OCT II

S DEC 05 S JAN 04 , 1989 S MAR 15 S APR 05

Water level

22.64

24.15

25.09

25.69 26.20 26.94

27.46 27.84 27.119 27.55

28.29 27.74 27.78 28.48

28.93

29.58 30.29 30.98 31.35

31.40 31.87 32.19 33.21 34.97

36.29 35.55

34.19

34. 18 33.00 30.30 29.47

29.68 30.03

30.80

31.90 34.00

33.53 34.31

34.10

34.92

35.76 36.75

37.85 38.09

37.37

36.87 37.02 35.56

34.75

MS Date

s MAY 0 I, 1989 S JUL 26 S AUG 30 S NOV 03 S DEC 06 S JAN 05,1990

S FEB 12 S MAR 20 S MAY 16 S 29 S JUL07 S AUG 19 S SEP 22 S OCT 30

S DEC 06 S JAN II, 1991 S FEB 07

S MAR 15 S APR19 S MAY 16 S JUN 26 S JUL 30 S AUG 30

S SEP 24

S OCT 28 S NOV 26

S DEC 30

S JAN 24. 1992

S FEB 26

S MAR 29 S APR 29 S MAY 29 S JUN 30

S ruL 29 S AUG 28

S 31 S SEP 26 S OCT 31 S NOV 17 S 29 S JAN 14. 1993 S 31

S MAR 02

S 09

S 30 S MAY 05 S 10

S 12

S JUN 02

80 Hydrology ofeb.e Helena Area Bedrock, Well-Central Montana, 14}93-98

Water level

34 .52 34,46

32.90 32.85

32.94

33.26

33.64 34.09

34.S1 33.85

33.30 35.03 3] .98

34.20 34.56 34.93 35.26 35.63 35.86 36.73

36.45

37. L\ 36.57 36.25 36.57

36.28 36.46 36.66

36.57 36.85 37.58 38.36 38.41 38.92 3g.711

38.69 39.25 38.90

38.95 39.05

39.16 39.24 39.40

37.92 38.20 38.42 38.44 38.40 38.50

MS Date

S JUN 14, 1993

S 30 S AUG 04 S 31 S SEP 22

S OCT 05 S NOV 10

S DEC 07

S JAN OS, 1994 S FEB 02 S MAR 02 S APR 10

S MAY 04

S 24

S JUN 07

S JUL 03 S 31 S AUG 03

S SEP07

S OCT 04 S NOV 05 S 30

S JAN II. 1995 S FEB 01 S MARO) S APR 05 S MAY 03 S 29 S JUN 06

S ruL 12 S 22

S SEP05 S OCT II S NOV 08

S 30 S JAN 11,1996 S MAR 12 S APR 16 S JUN 05 S JUL 02 S AUG 15

S SEP 01 S OCT 20 S DEC IS

S FEB 04, 1997 S MAR 07

S 22

S APR 12 S MAY 12

Water level

37.98 37.97 36.78 36.27 35.84 35.63 35.80 35.75 35.89

36.04

36.25 36.55

36.62 36.40

35 .92 36.67 35.90 35.92 36.49

36.78 36.68 36.76

37.08

37.32 37.54

37.86

38.13 38.06

38.06 36. 13 35 .72 36.25

35.74

35.92

36.13 36.67 36.79 36.69 35.64 35.00

37.71 35.]2

35.511 35.49 35.74

30.52 30.89

32.21

32.21

MS

s S S S S S S S S S S S S S S S S S

S S S S S

S S S

S S S S

S S S S S S S S S S S S S S S S S S S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 60 (Continued) Location Number: 10N04W02CBAA01 (Continued)

Date

MAY .31, 1997

JUL 09

21

Water level

32.30 31.67

31 .88

Well Number: 61

Date

SEP 29,1992 30

APR 27. 1993 MAY 12

JUN 03 SEP 09 OCT 12 NOV 17 DEC 08 FEB 16, 1994

MAR 03

Water level

32.30

18.07

18.76

20.09 15.69 6.32

8.39 9.30

9.90

11.55

12.00

Well Number: 63

Date

APR 08,1992

29 MAY 28

JUN 30 JUL 29

AUG .30 SEP 26

OCT 31

NOV 16 JAN2LI993

Water level

15.65 15.63

16.30

16.68 17.11 17.27 17.20

16.86 16.60

16.35

Well Number: 64

Date

SEP 24,1994

OCT 06 NOV 16

DEC 16

Water level

18.45 18.48 18.18 18.29

MS Date

S AUG 26, 1997

S SEP 23

S OCT 23

Water level

31.90

32.17

31.43

MS Date

S DEC II, 1997 S JAN 3D, 1998 S MAR 09

Location Number: 10N04W02CDCD01

MS Date

S APR 20, 1994 S MAY 23 S JUN 08 S SEP 07

S OCT 06 S DEC 16 S FEB 17, 1995

S APR 20 S JUN 01

S 08

S JUL 20

Water level

12.25

2.56 2.51 8.76 9.74

11.14 12.54

13.60 IIUO 15.29

2.51

MS Date

S SEP 06, 1995 S 28 S OCT 31

S NOV 28

S JAN 24, 1996 S FEB 22

S MAR21

S APR 23 S MAY 22 S ruN 26 S JUL 25

Location Number: 10N04W03ABBA01

MS Date

S MAR 03. 1993 S )0 S MAY 12

S JUN 02 S JUL OS S 2fl

S SEP 01

S OCT 05 S NOV 12 S DEC 08

Water level

16.37

15.47 14 .88 14.71 14.82

14.70 14.79

14.89 15.08

15.19

MS Date

S FEB 04, 1994

S MAR. 03 S APR 20

S MAY 18 S JUN 08

S AUG 03

S SEP 09

S OCT 06 S NOV 16 S DEC 13

Location Number: 10N04W03ADBD01

MS Date

S FEB I 7. 1995

S APR 20 S MAY 31 S JUL 20

Water level

18.54

18.82

17.85 16.73

MS Date

S SEP 28. 1995 S DEC 14 S APR 18, 1996

S JUL 30

Water level

31.97 32.57

D.II

Water level

6.00 6.77 7.26

11.96 12.39

9.21 9.99

16.02

2.71

2.26

5.41

Water level

15.47 15.57 15.71 15.90 16.01 16.68

17.00

16.68 16.09 16.09

Water level

17.84 17.80 13.35 14.74

MS Date

s MAY IS, 1998 S S

MS Date

S AUG 20, 1996

S SEP 24 S OCT 24 S NOV 25

S DEC 26

S JAN 23, 1997

S FEB 26 SR MAR 26

S APR II S 28

S

MS Date

S FEB 16,1995

S APR 20

S MAY 31

S JUL 18 S DEC 14 S APR 18, 1996

S JUL 30

S

S S

MS

S S S S

Water level

34.38

Water level

9.60 15 .54 7. 12

8.26 9.16

10.88 5.56 6.61 6.80 7.21

Water level

16.30

18.82 16. 19

15.32

15.88 14.05 15.48

MS

S

MS

s s s s s S S S S

S

MS

S S S S S

S S

TABLE 4 81

Table 4. Records of water levels. Helena area bedrock, west-central Montana (Continued)

Well Number: 65 Location Number: 10N04W03CDBA01

Date

APR 01,1992

29

MAY 29

JUL 30

AUG)I

SEP 29

NOV 02

fEB 03. 1993

MAR 03

APR05 MAY 12

JUN 02

JUL 28 SEP 01

OCT 12

NOV 16

18 DEC 08

21

JAN 19. 1994

FEB 02

Water level

MS

28.08 S

28.42 S 30.41 S 32.49 S

30.52 S 30.06 S 30.09 S 28.90 S 2&.88 S

26.13 S

25.95 S 26.23 S

26. 13 S 26.26 S

26.45 S

26.25 S 26.51 S 26.51 S 27 .23 S 26.66 S 26.60 S

Date

FEB 23,1994

MAR 0)

22

APR20

MAY 18

26 11jN 07

20 JUL 22

AUG 03

30

SEP 09

20

OCT 06

26

NOV 16

21 DEC 13

20

JAN 24, 1995

FEB 21

Water level MS

26.55 S

26.75 S 26.75 S 27.17 S

27.46 S 27 .38 S 27 .35 S 29.71 S

29.60 S 29.11 S 30.18 S 28.72 S

28.83 S 28.35 S 27 .78 S 17.80 S 27.70 S 27.45 S

27.4R S

27.22 S 27 .51 S

Date

FEB 22.1995

MAR 20 APR20

27

MAY 24

JUN 08

27

JUL 20

25

AUG 21 SEP 19

OCT 24

NOV 28

JAN 24, 1996

FEB 22

MAR 21

APR 22

MAY 22

.ruN 26

JUL 25

AUG 20

Well Number: 66 Location Number: 10N04W03DAAA01

Date

FEB 26, 1992

MAR31

MAY 28 JUN 30 AUG31

SEP 29

OCT 31

FEB 03. 1993

MAR03

WBter level

MS

31.1J S 31.42 S 32.10 S

32.68 S 33 .49 S 33.60 S 33.51 S 34.12 S

34.29 S

Date

MAR 30,1993

MAY 10

JUN02

JUL 28

SEPOI

OeTOS NOV 10

DEC OS FEB 02, 1994

Water level

MS

33 .18 S 33 .12 S 32.19 S

29.70 S 29.25 S 29.11 S

28 .91 S

29.0J S

29.19 S

Date

MAR 04.1994

APR 20

MAY 18

JUN07 AUG 03

SEP 07

OCT 06

NOV 16 DEC 09

82 Hydrology of the Helena Area Bedrock, West-Central Monlana. 1993-98

Water level

MS

27.46 S 27.64 S 27 .77 S 27.72 S

28.32 S

27.99 S

28.52 S

27.75 S

27.70 V

29.09 V

27.93 S

31.20 SR

27.38 S

27.21 S

26.31 S

26.01 S 26.86 S 27.14 S 2&.62

26.73

26.03

Water level

S S S

MS

29.38 S 29.45 S 28.24 S 28.03 S 28.47 S 29.44 S 29.61 S

29.86 S

30.31 S

Date

SEP 24, 1996

OCT 24

NOV 25

DEC 26

JAN 23, 1997

FEB 27

MAR26

APR II 27

JUN 30

JUL 28

AUG 25

SEP 23

OCT 30 NOV 25

DEC 17

JAN 29,1998

FEB 24 APROI

28

MAY 27

Date

FEB 17, 1995

APR20

JLJN 01

JUL 20 SEPOI

DEC 14

APR 19, 1996 JUL 30

Water level

MS

2552 S 25.07 S

22.12 S

25.56 S 25.39 S 21.52 S

23 .03 S 22 .60 S 23.09 S 24.56 S 25.46 S

26.07 S 26.85 S 25. 12 S 25.46 S 25.48 S 25 .66 S 26.12 S 26.34 S

26.40 S P

Water level

MS

31.42 S 32 .30 S

31.59 S

28 .98 S

30.89 S 30.57 S 30.86 S

27.29 S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

WelJ Number: 67 Location Number: 10N04W03DADA01

Date

SEP 25. 1988 JAN 24, 1992

FEB 26

MAR31

APR 29

MAY28

JUN 30

JUL 29

AUG 29

SEP 26

OCT 31

NOV 16

29

JAN 21. 1993 FEB 03

MAR 03

09

Water level

MS

3 \.66 S 27.53 S

28 .25 S 29.03 S 29.32 S

29.50 S 30.07 S 30.63 S 31.23 S

31.72 S 32.25 S 32.45 S 32 .61 S

33 .20 S

33 .32 S

33.57 S

32 .M S

Date

MAR 30. 1993

APR 24

MAY 10

12

JUN02

JUL OS 18

SEPOI

OCT 05

NOV 10

DEC 08 FEB 02, 1994

MAR03 APR 02

20

MAY 18

Water level

MS

32.57 S

32.65 S

30.95 S

28.65 S 19.03 S 15.05 S 17.16 S 20.07 S 21.93 S 23.48 S 24.42 S 26. 13 S 26.87 S 27.53 S 21.17 S

14.90 S

Date

JUN 07. 1994

JUL 03

AUG03

SEP 07

OCT 06

NOV 16

DEC 09

FEB 16.1995

APR 13

MAY 31

JUL 18

SEP 01

OCT31

NOV 28 JAN 24,1996

FEB 22

Well Number: 68 Location Number: 10N04W03DBBD01

Date

APR 01,1992

29 MAY 29

.IUL30 SEP 09

29

NOV 02

FEB 03, 1993

MAR04

31

Water level

55.46

59.69

6Ul6

65 .02

64 .26 65 .44

61.68

MS Date

s MAY 12. 19.93

S JUN 02

S JUL 28

S SEP 01

S OCT 12 S NOV 15

S DEC 08

00.39 S FEB 04,1994

MAR03

APR 20

60.37 S 59. \3 S

Water level

56.7.9

60.00

54 .10

53 .23

52.86

50.80

51 .00

MS Date

S MA Y 18. 1994

S JUN 07

S AUG 03

S II S SEP 09

S OCT 06

S NOV 16

51.11 S DEC 13 :; 1.45 S

51.76 S

FEB 21,1995 APR 20

Well Number: 69 Location Number: 10N04W03DBDD01

Date

JUl. 13. 1992

30

SEP02

29 NOV 02

30

FEB 03. 1993 MAR04

31

Water level

44.42

45.53 46.94

47.81

48.29

48 .7\

49.71

50. 10

47.38

MS Date

S APR 22.1993

S MAY 12

S JUN 02

S JUL 28 S SEP \3 S OCT 12

S NOV 12

S FEB 04, 1994

S MAR 03

Water level

48.02

27.70

21.03 20.06

26.99

30.04

32.88

38.43 39.78

MS Date

S APR 20, 1994

S MAY 18 S !UN 07

S AUG OJ

S SEP09

S OCT 06

S NOV 16

S DEC 16 S FEB 2\. 1995

Water level

MS

13.42 S 13 .76 S 17.69 S 20.72 S 22.75 S 24.68 S 25.76 S 28.06 S 29.46 S \8.05 S

15.1 \ S 19.48 S 23.\8 S 24 .5\ S 26.73 S 22.60 S

Date

MAR21,19c)()

APR 23

MAY 22

JUN 26

JUL 25

AUG 20

SEP 24 OCT 24

NOV 25

DEC 26

JAN 23. 1997

FEB 26

MAR 26

APR II

28

Water level

MS Date

53 .94

53.36

69.90

58 .93

61.49

58.63

55.31

S JUN 08. 1995

S JUL 20

S SEP 01

S DEC 14

S APR 18. 1996

S JUL 3\

S

55.67 S

55.75 S 57.05 S

Water level

25.78

17.25

12.52

22.85

29.18

32.65

36.19

38.35 41.97

MS Date

S APR 13, 1995

S MAY 31 S JUl. 20

S SEP 06 S DEC 14

S APR 18, 1996

S S

S

Water level

MS

27.12 S

25.68 S

19. 19 S

13.49 S 13.87 S

15. \0 S 18.31 S

20.21 S

22.94 S

25 .50 S

25.49 S

23.43 S

2 1.25 S

21.57 S 21.91 S

Water level

57.09 52.9)

61AR

52.80 47.47

52.99

Water level

43.93

16.28

17.94

26.92

36.32

40.90

MS

S

S S S S S

MS

S S S S S S

TABLE 4 83

Table 4. Records ofwaler levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 70 Location Number: 1 ON04W03DCBAO 1

Date Water MS Date

Water MS Date

Water MS Date

Water MS level level level level

APR 24,1993 70.54 S OCT 19,1993 52.84 S MAY 18, 1994 33.28 S DEC 16, 1994 61.09 S MAY 12 51.75 S DEC OS 57.24 S JUN07 29.40 S APR 13. 1995 66.68 S JUN 02 37.01 S FEB 04. 1994 61.02 S OCT 06 55 .52 S SEP 01 49.00 S

JUL 28 39.59 S APR 20 47.53 S NOV 16 58.95 S JUL 31. 1996 50.46 S

Well Number: 73 Location Number: 10N04W08DCAC01

Date Water

MS Date Water

MS Date Water

MS Date Water MS

level level level level

AUG 28, 1995 53.20 V JUL 24.1996 56.78 V MAR 18,1997 41.02 S DEC 17. 1997 44.80 S

NOV 30 51.60 S AUG 26 56.62 S APR 21 40.88 S JAN 29,1998 45.50 S FEB 13, 1996 41.17 S SEP 19 59.53 S JUN 23 49.20 S FEB 24 45.44 S

24 45 .55 V OCT 22 51.45 S JUl28 48.16 S APR 01 45 .44 S

MAR 19 44.20 V NOV 25 47.08 S AUG 25 49.07 S 2R 45 .57 S

APRI9 43.22 V DEC 18 46.81 S SEP 23 45 .64 S MAY 27 49.79 S MAY 20 4}.40 V JAN 22, 1997 45.39 S OCT 30 47.90 S

JUN 19 43 .39 V FEB 19 42.01 S NOV 25 44.78 S

Well Number: 75 location Number: 1 ON04W1 OCCDOO1

Date Water

MS Date Water

MS Date Water MS Date

Water MS

level level Jevel level

OCT OS, 1993 47.28 S SEP 20,1994 55.68 S JUL 25. 1995 53.22 V JUL 25, 1996 38.39 S DEC21 46.31 S OCT27 54.50 S SEP 19 56.34 SP AUG 26 39.38 S JAN 19, 1994 45.94 S NOV 22 54. 13 S OCT 24 62.70 S SEP 19 40.95 S

FEB23 46.35 S DEC 20 51.34 S DEC 01 51.52 S OCT 22 40.71 S

MAR22 47.23 S JAN 24,1995 50.53 S FEB 13. 1996 71.12 S NOV25 41.99 S

APR 26 46.21 S FEB 22 50.19 S 24 45 .88 S DEC IS 41.90 S

MAY 27 4R.OS S MAR 20 52. 13 S MAR 19 51.06 S JAN 22, 1997 43.27 S JUN 21 54.31 SP APR21 48.89 S APR 19 49.26 S FEB 19 42. 10 S JUL 21 63 .84 SP MAY 24 50.03 S MAY 20 48.71 S MAR 18 40.14 S AUG 30 55.39 S JUN 26 51.79 S !UN 19 43 .53 S APR 2) 39.73 S

84 Hydrology of the Helena Area 8tdrock, W~t-Ccntral Monrana, 1993-98

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 77 Location Number: 10N04W15BDAC01

Date

NOV 08,1993

DEC20 JAN 19, 1994

FEB 23

MARl2 APR 26

MAY 26

JUN10 JUL 21 AUG 30 SEP 20

OCT 26

NOV21 DEC 20

Water level

40.09

39.99

39.99

39.78

39.77

39.75

39,50

39,SI

39.50 39,65

39.68

39.49

39.51

39,81

MS Date

S JAN 24, 1995

S FEB 22 S MAR 20

S APR 27

S MAY 22

S JUN 27 S JUL 25

S AUG 21

S SEP 19 S OCT 24 S NOV 08

S JAN 24. 1996 S FEB 22

S MAR 21

Water level

39, 18

39.13

39.00

39.10

39.07 39,09

39,23

39.49

39.91

40.04

38.61

39.89 39.82

39.79

MS Date

S APR 23, 1996

S MAY 22 S .TUN 26 S JUL 25 S AUG 20

S SEP 24

V OCT 22

V NOV 25

S DEC 18

S JAN 22, 1997 S FEB 19

S MAR 18 S APR 21

S JUN 24

Well Number: 80 Location Number: 10N04W23CADD01

Date

NOV 17. 1993

JAN 19, 1994

24

FEB 23

MAR 22 APR 22 MAY 26

JUN 20

JUL20

AUG 30

SEPI9

ocr 26

NOV 21

DEC 20

Water level

53,75

53.91

56.21

57.74 54.45

54.58 54.48

55.37 55.35

54 .79

54.68

57.89

54.81

55.53

MS Date

S JAN 24. 1995

S FEB 22

S MAR 20

S 24

S APR 26

S MAY 02

S 22

S JUN 27 S JUL 25

S AUG 21

S SEPI9

S OCT 24

S NOV 27 S JAN 23, 1996

Water level

56.21

54.96

55.05

55.27

55.96

54.99

54.77 55.27

55.40

56.80

54.86

54.88

53.48

55.61

MS Date

S FEB 2 I, 1996

S MAR 20 S APR 22

S MAY 22

S JUN 25

S JUL 24

S AUG 20

S SEP 25 V OCT 22

V NOV 27 S DEC 27 S JAN 23, 1997 S FEB 27 S MAR 24

Well Number: 82 Location Number: 10N04W23DCAA01

Date

SEP 0.1.1995

27

JAN 23,1996

FEB 21

MAR 20

Water level

MS

96.03 S 91.27 S 92,07 S 90.96 S

90..65 S

Date

APR 22. 1996 MAY21 JUN 25

IUL 24

AUG 19

Water level

MS

90.24 S 90.. 17 S

90.52 S

91.22 S 91.0.4 S

Date

SEP 25,1996

OCT 22 NOV 25

DEC 27 JAN 2), 1997

Water hwel

39.65

39.61

39.55 39,63

39.72

39.59

39.33

39.04

38.86

38.38

38.12

37.82

37.3 1

36.59

Water level

54.38

54.0.4 54.l4 54 , l J

53.31

53.il

53,75 54..33

54.86

57.43

57.53

57.53

54.99

55.27

Water level

MS Date

S JUL 28. 1997

S AUG 25

S SEP 23 S OCT 30

S NOV 25

S DEC 17 S JAN 29, 1998

S FEB 24 S APR 01

S 28

S MAY 27

S

S

S

MS Date

S MAY 30,1997 S JUL 28

S AUG 25 S SEP 23

S OCT 30

S NOV 25

S DEC 17

S JAN 29, 1998

S FEB 24 S APR 0.1

S 28

S MAY 27 S S

MS Date

91.29 S FEB 27,1997 MAR 24

MAY 0.2 91.29 S 91.)9 S

91.28 S

91 . .39 S

Water level

36. 13

35.51

36.39

33.38

32.65

32.09

31.58

31.48

31.71

31.81

32.09

Water level

55.37 54.49

54.32

54.66

54.75 54,99

55,01

54.89

55.82 55.95

56.43

56.34

Water level

MS

s s s S

S

S S S S S S

MS

S S S S

S S S S S S S S

MS

91.48 S 91.53 S

91.56 S

TABLE -4 85

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 83 Location Number: 10N04W23DDDD01

Date

NOV 08.1993 DEC 20 JAN 19,1994 FEB 23 MAR 22 APR 22 MAY 26 .!UN 20 JUL 20 AUG30

SEPI9

Water level

MS

126.70 S 97.40 S 97.0[ S

107.55 S 118.15 S 129.23 S

129.38 S 129.93 SR

130.39 SR 130.97 S

130.78 S

Date

OCT 26,1994 NOV2[

DEC 20 JAN 24, 1995

FEB 22 MAR20 APR 26 MAY 22 .!UN 27

.!Ul 25 AUG21

Water level

MS

129.99 S

129.35 S

130.50 S 131.26 S

132.40 S 132.54 S 13\.76 S

130.89 S 130.55 S 130.64 V

131.68 V

Date

SEP 19, 1995 OCT 24 NOV 27 JAN 23, 1996 FEB 21 MAR 20 APR 22 MAY21 JVN 24 JUL 24 AUG 19

Well Number: 65 Location Number: 10N04W25ACDB01

Date

NOV 08. 19'>3 DEC 20 JAN 19.1994 FEB 23 MAR 22 APR 22 MAY 26 JUN 20 AUG 30

Water level

110.39 112.74 110.87 114.17 111.41 111.50 111.75

112.05 113.77

Well Number: 67

Date

SEP 01,1995 OCT31 NOV 27

JAN 23.1996 FEB 21

Water level

146. 19

144.26 144.61

145.18 133.56

Well Number: 68

Date

SEP 01. 1995 OCT31 NOV27

JAN 23. 1996 FEB 21

Water level

199.04 191.02 192.90 193.26

[ 72.42

MS Date

S SEP19,1994

S OCT 26

S NOV 21 S DEC 20 S JAN 24. 1995 S FEB 22 S MAR 20 S APR 26 S MAY 22

JUN 27

Water level

110.86 110.44 111.24 I J 1.78 112.46 112.84 112.97 112.90 112.12 111.47

MS Date

S JUL 25, 1995 S AUG 21 S SEP 19 S OCT 24 S NOV 27

S FEB 21.1996 S MAR 20 S APR 22 S MAY 21 S JUN 25

Location Number: 10N04W26ABAC01

MS Date

S MAR 20, 1996 S APR 22 S MAY 21 S JUN 25 S JUL 24

Water level

143.33

143.21 143.48 144.1 [ 146.57

MS Date

S AUG 19,1996 S SEP 25 S OCT 22 S NOV 27 SP DEC 27

Location Number: 10N04W26BAAA01

MS Date

S MAR 20, 1996 S APR 20 S MAY 22

S JUN 24 S JUL 24

Water level

165.35 173.)9

182.55

186.77 195.82

MS Date

S AUG 20, 1996

S SEP 25 S OCT 22 S NOV 25 S DEC 27

86 Hydrology of the Helen" Area Bedrock. West·Central Montana, 1993-98

Water level

MS Date

131.37 S SEP 25. 1996 OCT 28 NOV 27 DEC 27

130.07 S

130.35 S 130.74 S

130.32 S JAN 23 , 1997 FEB 27 MAR24 MAY02

129.40 S [28.14 S 128.25 S 128.66 S 128.48 S 128.92 S

Water level

111.15 111.10 108.67

111.l9 L11.56 111.54 I) 1.34

110.94

110.93

110.4 7

Water level

\42.39 143.39

145.05 144.72 145.04

Water level

198.45 195.32 194.91

193 .79 194.14

MS Date

S JUL 24, 1996 S AUG 19 S SEP 25 S OCT 22 S NOV 27 S DEC 27

S JAN 23. 1997 S FEB 27 S MAR 24 S MAY 02

MS Date

S JAN 23. 1997 S FEB 27 S MAR 24 S MAY 02

S

MS Date

S JAN 23. 1997 S FEB 27 S MAR 24

S MAY 02

S

Water level

MS

129.09 S 129.29 S 129.7:> S 130.51 S 135.12 S

1.33.88 S

129.72 S 132.11 S

Water level

110.05

109.91 111.37 11 1.02 111.61 111.80 112.11 112.01 112.03 112.10

Water level

145.08 144.35 144.21

144.R7

Water level

193.13

1:<7.47 18S.51 1&9.26

MS

S S S S S S

S S

S

S

MS

S S S S

MS

S S S S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 90 location Number: 10N04W29BBBC01

Date

MAR 21,1996

APR 23

MAY22

JUN26

Water level

11.34

ILlS

13 .73

15.72

MS Date

S JUL 25. 1996

S AUG 20

S SEP 23

S OCT 24

Water level

1828

19.20

19.49

19.28

MS Date

S NOV 27. 1996

S DEC 26 S JAN 28. 1997

S FEB 28

Well Number: 93 location Number: 10N04W36CAAD01

Date

SEP28.1995

OCT )0

NOV 27

JAN 23, 1996

FEB 21

Water level

74.52

59.02

74.21

74 .99

64.18

MS Date

S MAR 20, 1996

S APR 22 S MAY 21

S JUN 25

S JUL 24

Water level

62.35

73.06

61.15

72.79

73.39

MS Date

S AUGI9,1996

S SEP 26 S OCT22

S NOV 27

S DEC JO

Well Number: 94 Location Number: 10N04W36DCBB01

Date

OCT 13. 1993

DEC 20

JAN 19, 1994

FEB 24

MAR 22

APR21

MAY 25

JUN 20

JUL 20

AUG 30

Water level

67.69

66.24

65.77

65.37

65 .12

64.91

64.56

64.15

64.10

63.02

MS Date

S SEP 19. 1994

S OCT 26

S NOV 21

S DEC 20

S JAN 24. 1995

S FEB 22

S MAR 20

S APR 26 S MAY22

S JUN 27

Water level

63.02

63.21

63.47

63.59

63.79

62.93

63 .91

64.05

64.01

63.69

MS Date

S JUL 25, 1995

S SEP 19

S OCT 24 S NOV 27

S JAN 23. 1996

S FEB 21

S MAR 20

S APR 22

S MAY21

S JUN 25

Well Number: 95 Location Number: 10N05W03ABCB01

Date

OCT 08. 1993

DEC 21

JAN 20. 1994

FEB 23

MAR 24

APR '22

MAY 27

Water level

MS

59.55 S 61.28 S

61.74 S

66.35 S 62 .75 S

62.55 S () 1.00 SR

Date

JUN 20,1994

JVL21

AUG 30

SEP 20

OCT27

NOV21

DEC 20

Water level

MS

60.84 S

65.06 S 63.48 S

65.46 S

65 .24 S

64.09 S

64.08 S

Date

JAN 24, 1995

FEB 22

MAR 20

APR 21

MAY 22

JUN 26

JUL 25

Water level

19.R3

19.26

18.37

11.06

Water level

72.81

72.29

73.68

72.89

72.91

Water level

63.10

62 .% 62 .90

6.1.0)

63.19

62.81

63.51

61.86

61.57

6 I. Of;

Water level

MS Date

S MAR 25. 1997

S APR 26

S S

MS Date

S JAN 28. 1997

S FEB 28

S MAR 26

S MAY 02

S

MS Date

V .1UL 24, 1996

S AUG 19

S SEP 26

S OCT 22

S NOV 27

S DEC 30 S JAN 28, 1997

S FEB 27

S MAR 26

S MAY 02

MS Date

64.95 S AUG 21 , 1995 SEP 20 64.40 S

66.IR S

66.14 S

62.69 SR

68.53 SR 67.90 V

OCT 24

AUG 20,1996

SEP 23

Water level

11.67

13.91

Water level

67.64

72.95

73.16

73.04

Water level

60.70

60.61

M.XO 60.98

61.34

61.49

61.87

62.01

62.08

62.40

Water level

MS

s S

MS

s S

S S

MS

S

S

S S S S

S

S

S S

MS

67.27 V

65.95 S

65.23 S

68.68 S 64.84 S

TABLE 4 87

Table 4. Records ofwaler levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 96 Location Number: 10N05W03ABDD01

Oate

AUG 25,1995

FEB 22, 1996

MAR 21 APR 23 MAY 22

lUN 26

JUL 25

AUG 20

Water level

24.07

24.07

22.84

23 .33

22.11 22.40

22.77

MS Date

S SEP 24, 1996

S OCT 22

S NOV 25 S DEC 18

S JAN 20, 1997

S FEB 19

S MAR 18

23.15 S APR21

Water level

23.25

23.22

23 .25

23 .63

23.79

21.49

20.15

MS Oate

S JUN 23, 1997

S JUL 28

S AUG 25

S SEP 23

S OCT 30 S NOV 25

S DEC 17

10.37 S JAN 29.1998

Well Number: 98 Location Number: 10N05W09BDBC01

Date

SEPOI. 1995

DECOI

JAN 24.1996

FEB 22

MAR21 APR 23 MAY 22 JUL 25

Water level

MS

50.69 S 39.72 S

41.37 S

37.32 S 34.61 S

17.97 S 17.09 S

44 .33 S

Date

AUG 28,1996

SEP 23

OCT 22 NOV 25

DEC 18

JAN 22, 1997

FEB 19

MAR 18

Water level

MS

56.50 S

42.60 S 36.75 S 35.54 S 35.63 S

35.13 S

39.72 S 42.60 S

Date

APR 21 , 1997

lUN 23

lUL 28 AUG 25

S£P 23

OCT 30

NOV 25

DEC 17

Well Number: 101 Location Number: 10N05W25DBDA02

Date

OCT 01. 1995

26

NOV 28 JAN 24, 1996

FEB 22

MAR20

APR 23

MAY 22 JUN 26

Water level

MS

75 .21 S

75.60 S

75 .50 S 75.19 S

74.96 S

74.20 S

73 .34 S

71.36 S

69.24 S

Date

JUL 25, 1996

AUG 20

SEP 23

OCT 24 NOV 27

DEC 26

lAN 29. 1997

FEB 28

Water level

MS

67.9R S

67.02 S 67 .30 S 68.48 S

69.25 S 69.51 S 71.16 S 69.88 S

Date

MAR25,1997 APR26

JlJN 24

JUL 28

AUG 25

SEP 23

OCT 30

NOV 25

88 Hydrology orthe Helena Art.a 8edrock. West-Central Montana. t993-98

Water level

MS Date

17.66

Ill .47

19.90

19.92

19.87

20.11 20.30

S FEB 24. 1998

S APR 01

S 28 S MAY 27

S S S

18.47 S

Water level

MS

7.93 S 35.04 S

39.36 S

43.06 S

32.48 S 35.25 S 34 .31 S 35.62 S

Water level

MS

69.93 S

71.79 S

71.09 S 68.92 S

69.01 S

69.76 S

70.20 S

70. 15 S

Date

JAN 29,1998

FEB 24 APROI

28 MAY27

Date

DEC 17. 1997 JAN 29,1998 FEB 24

APROI

28

MAY27

Water level

20.65

20.77

21.10

20.72

Water level

MS

S

S

S

S

MS

36.69 S 37.91 S 33.84 S 34.13 S

40.20 S

Water level

MS

74.33 S

70.81 S 71.35 S

71.52 S

71.86 S

72.16 S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 102 Location Number: 10N05W32ACCA01

Date Water

MS Date Water MS Date

Water MS Date

Water MS level level level level

OCT 10,1995 34.07 S APR 23. 1996 32.42 S OCT 24,1996 36.72 S MAR 25,1997 ) 1.09 S

31 37.29 S MAY 22 P NOV 27 35.33 S APR 26 27. 14 S

NOV 28 35.99 S JUN25 37.67 S D£C26 35.54 S

JAN 24, 1996 32.01 S AUG 28 51.32 SR JAN 29,1997 34.44 S

FEB 22 30.04 S SEP 23 37.67 S FEB 25 34.06 S MAR21 33.42 S

Well Number: 103 Location Number: 10N05W33ABD 01

Date Water

MS Date Water

MS Date Water

MS Date Water MS

level level level level

NOV 12, 1993 17.44 S OCT 26.1994 16.39 S SEP 19, 1995 14.77 S SEP23,I996 10.57 S DEC 20 17.87 S NOV21 16.87 S OCT 24 14.96 S OCT 24 10.42 S JAN 19. 1994 17.94 S DEC 20 17 . II S NOV 28 14.67 S NOV 27 I l.71 S

FEB 23 17.93 S JAN 24, 1995 17. \3 S JAN 24,1996 14.51 S DEC 26 11 .68 S MAR 22 15.60 S FEB 22 13 .66 S FEB 22 14.16 S JAN 29,1997 10.93 S APR 22 15.13 S MAR 20 14.94 S MAR2l 9.05 S FEB 28 12.42 S MAY25 16.14 S APR 26 15.62 S APR23 &.7& S MAR2S 11.60 S

JVN 20 17.22 S MAY22 16.50 S MAY22 9.46 S APR 26 12.27 S JUL 20 15.76 S JUN 27 14.93 V JUN 26 8.60 S AUG 30 16.09 S JUl25 14.92 V JUL 25 8.61 S

SEI'19 15.69 S AUG21 14.81 V AUG 20 9.0) S

Well Number: 104 location Number: 10N05W33BCDD01

Date Water MS Date Water MS Date

Water MS Date Water

MS level level level level

SEP 28, 1995 22.86 S MAR 20,1996 15.79 S AUG 20.1996 22.77 S JAN 29,1997 21.35 S OCT31 23.95 S APR 22 14.47 S SEP 24 22.22 S FEB 27 17.10 S

NOV 28 25.00 S MAY 22 16.92 S OCT 27 22 .71 S MAR25 17.68 S

JAN 24, 1996 21.07 S JUN 25 15.58 S NOV27 23 .00 S APR 26 17.50 S FEB 22 14.49 S ruL 25 23.38 S DEC 26 22.38 S

TABLE 4 89

Table 4. Records of waler levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 105

Date

OCT 10, 1995

31

NOV 28

JAN 24,1996

FEB 21 MAR21

APR 23

MAY22

Water level

16.19

16.89

14.60 19.61

13.71

13.25 13.10

12.29

Well Number: 107

Date

OCT 10, 1995

Water leve!

16.22

Well Number: 10B

Date

JAN 24,1996

FEB:22 MAR21 APR 23

Water level

11.43

14.49

15.10

8.85

Well Number: 112

Date

OCT 15. 1993 DEC 20

JAN 19,1994

FEB 23 MAR 22 APR 26 MAY 25 JUN 20 JUL 20

AUG 30

SEP 19

Water level

11.94

15.15 13 .50

13.96

13.94

\3.18

12 .26

12.96

13 .06

13.84

14.01

Location Number: 10N05W33CDCD01

MS Date

S JUN 25. 1996

S JUL 25 S AUG 20

S SEP 24

S OCT 24

S NOV 24

S DEC 26

S JAN 29. 1997

Water level

12.28

14.26

15.16

15.69

16.16

16.58

16.65

15.52

MS Date

S FEB 25, 1997

S MAR 25 S APR 26

S )UN 24

S JUL 28

S AUG 24

S SEP 23 S OCT 30

Location Number: 10N05W34DCBA01

MS Date

S OCT31,1995

Water leve!

7.34

MS Date

S NOV 27, 1995

Location Number: 10N05W34DCBA02

MS Date

S MAY 22, 1996

S JUN 25

S JUL 25

S AUG 19

Water level

15.61 12.84

14.87 15.13

MS Date

S SEP 24. 1996

S OCT 22

S NOV 25 S JAN 29. 1997

Location Number: 10N05W36DADD01

MS Date

S OCT 26, 1994

S NOV 21 S DEC 20 S JAN 24, 1995 S fEB 22

S MAR 20 S APR 26

S MAY 22 S JUN 27 S .IUL 25 S AUG 21

Water level

14 . 11

15.05

14.95

13.25 14.2 8

14.19 13.93

12.78

9.63

10.52

11.73

MS Date

S SEP 19. 1995

S OCT 24

S NOV 28 S JAN 24. 1996 S FEB 22

S MAR 21

S APR 23

S MAY 22 V .TUN 26

V JUL 25 V AUG 20

I}O Hydrology of Ih~ H.dl'nll Are .. Bedrock., We-sl-Cclllral MontliDlI, 1993·98

Water level

14.78

14. 12

13 .06 12,71 24.22

13.60

15.17 16.20

Water level

17.20

Water level

16.37

16J3

\7 .03

\5 .75

Water level

\2.70 13.25 13.63

\3.65

11.55

12.20 12.34 12.25 8.80

10.90

12.03

MS Date

S NOV 25,1997

S DEC 17

S JAN 29,1998

S FEB 24

S APR 01 S APR 28

S MAY 27

S

MS

S

MS Date

S FEB 27, 1997 S MAR 25 S S

MS Date

S SEP 23. 1996

S OCT 24

S NOV 27 S DEC 26

S JAN 29, 1997

S FEB 28

S MAR 25

S APR 26 S S S

Water level

14.12

18.99

14.86

14.57 13 .61

13 .86

14.76

Water level

14.66

13.89

Water level

12.94

13.43 13,65

13.76

13.56

13.08

13.31

1J.26

MS

S S

S

S

S S S

MS

S

S

MS

S S

S

S

S

S

S S

Table 4. Records of water levels, Helena area bedrock, west-central Monlana (Continued)

Well Number: 115

Date

OCT 25.1995

NOV 30

FEB 05. 1996

22 MAR 19

Water level

100.80

100.04

99.30

103,55

99,59

Well Number: 120

Date

OCT 23. 1995

NOV 30

FEB 05. 1996

22

MAR 19

Water level

125.82

I 24.8!! 122,66

122,58

122.35

Well Number: 123

Date

JUL 01. 1993

AUG 06

SEP 13

OCT 27

NOV 09

DEC 22

JAN 20. [994

FEB 24 MAR 24 APR 22

MAY 31

Water level

29.48

29.79

29.89

29.99

30.10

30.25

)0.37

30.32

30.44

30.39 29 ,95

Well Number: 125

Date

OCT 19. 1995

26

NOV 30

FEB 05, 1996

22

MAR 19

APR 18

MAY21

Water level

58.67

58.60

58.38

58.06

57.62

57.42

57.26

57. 17

location Number: 11 N02W18BDCB01

MS Date

S APR 18, 1996

S MAY 21

S JUN 20

S JUL 25

S AUG 26

Water level

101.48

99,66 92.11

IOS.08

104.58

MS Date

S SEP 20, 1996

S OCT 23

S NOV 26

S DEC 19

S JAN 23. 1997

location Number: 11 N03W02CDCD01

MS Date

V APR 18, 1996

V MAY 21

V .ruN 20

V JUL 25

V AUG 26

Water level

12\.45

124,60

142.70

154.19

144,00

MS Date

V OCT 23, 1996

V NOV 25

V DEC 19

S JAN 23, 1997

S FEB 19

Location Number: 11N03W04ABAD01

MS Date

S .rUN 21,1994

S JUL 21

S AUG 31

S SEP 20

S OCT 27

S NOV 22

S DEC 21

S JAN 25. 1995

S FEB 23

S MAR 22

S APR 24

Water level

31,30

31.96

29.54

31.64

29.74

29.21

28.71

28.32

29.58

28,22

28 ,52

MS Date

S MA Y 24, 1995

S ruN 27

S JUl. 26

S AUG 22

S SEP 20

S OCT 25

S FEB 16. 1996

S 22

S MAR 19

S APR 18

S MAY 21

Location Number: 11N03W05CCBC01

MS Date

V JUN 20. 1996

V IUL 25

V AUG 26

V SEP 20

V OCT 22

V NOV 26 V DEC 19

V JAN 22.1997

Water level

57.56

58.32

56.58

59.15

60.02

57.87

59.35

59.29

MS Date

V FEB 19, 1997

V MAR 18

S APR 2[

S JUN 23

S JUl28

S AUG 25

S SEP 23

S OCT 30

Water level

[00.28

99.[9

101.04

100.65

99.69

Water level

154 .63

156.53

153,92

144.60

141.39

Water level

28.58

29.80

31.30

31.82

32.66

29.68

28.98

31.29 28 ,16

27,68

29.96

Water level

57.87

56.68

55.75

55.80

55.51

56.28

56.41

56.71

MS Date

SR FEB 19, 1997

S MAR 18

S APR. 21

S S

MS Date

S MAR 18. 1997

S APR 21

S S S

MS Date

S JUN 20, 1996

V JUL 25

V AUG 26

V SEP 20

S OCT 23

S NOV 26

S DECI9 S JAN 23. 1997

S FEB 19

S MAR 18

S APR 21

MS Date

S NOV 25. 1997

S DEC 17

S JAN 29. 1998

S FEB 24

S APR 0)

S 28 S MAY 27

S

Water level

99.34

n.76 99.87

Water level

141.15

139.16

Water level

33 .20

44.70

34, 17

32 .34

30.46

30.52

29.89

30.45

29.0)

28 ,98

28 ,32

Water level

56.01

55.93

56.[7

57.72

56.29

55.77

56.06

MS

s s S

MS

S

S

MS

s SP S

S

S

S S

S S S S

MS

S

S S S S S

S

TABLE 4 91

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 128 Location Number: 11N03W07BDBC01

Date

NOV 10,1993

DEC 22

JAN 20, 1994

FEB 24

MAR 24

APR 21

MAY 31

ruN 21 JUL 21

AUG3}

SEP 20

Water level

MS

57.30 S

57.95 S 58.50 S

59.38 S

57.72 S 57.75 S

58.89 S 58.09 S

58.29 S

58.41 S 56.75 S

Date

OCT 27,1994

NOV 22

DEC 21

JAN 25, 1995

FEB 23

MAR 22 APR 24

MAY 24

JUN 27

JUL2S AUG 22

Water level

MS

59.30 S 58. 17 S 57.99 S 58.Q2 S

57.79 S 53.05 S

58.59 S 58.14 S 52.12 V

58.10 V

59.36 S

Date

OCT 25,1995

NOV 30

FEB 13. 1996 2)

MAR21 APR 18

MAY 21

JUN 20

nJL30

AUG 26

SEP 20

Well Number: 129 Location Number: 11N03W08BCBA01

Date

OCT 31,1990

FEB 21, 199\

MAR 14 APR1)

OeT28.199)

DEC 21

JAN 20,1994

FEB 24

MAR 24

APR 21 MAY)I

JUN 21 JUL 21

AUG 31

Water level

50.58

49.83

49.69

49.54

49. 19

48.66

45.63

49 .62

48.27

48.41 48.94

51.57

MS Date

S SEP 20, 1994

S OCT 27

S NOV 22

S DEC 21

S JAN 25, 1995

S FEB 23

S APR 21

S MAY 24

S JUN 27

S JUL 26

SR AUG 22

SP SEP 20

55.16 SR OCT 24

52 .53 S NOV )0

Water level

53.09

52.15

52 .77

52.32

52.05

53.70

51.87

53 .00

52.49 53.52

57.94

55.21

MS Date

S FEB 12, \996

S 22

S MAR 19

S APR 18

S MAY 21

S JON 20

S JUL 25

S AUG 26

S SEP 20

V OCT 21 VP NOV 26

S DEC 19

53.48 S

55.14 S

JAN 22. 1997

FEB 19

Well Number: 130 Location Number: 11N03W09ABBB01

Date

DEC 02, 1995

SEP 20, 1990

OCT 23

Water level

47.30

56.14

57.09

MS Date

S NOV 26, 1996

SP DEC 19

S

Water level

52.45 51.40

MS Date

S JAN 23. }997

S FE1319

92 Hydrology oflhe Helena Area Bedrock, West-Central MontaRa, 1993·98

Water level MS Date

58.43 S OCT II. 1996

NOV 26

DECI9

58. 18 V

5H.99 V 58.00 V JAN 22, 1997

FEB 19 58.94 V

58.04 V MAR 18 57.86 T APR 21

58.13 V 24 58.56 V

59.27 S

59.20 SR

Water revel

57 .53

52.99

55.01

52.54

53.50

53.00

54.23

55.79

54.43

55.84 53 .90

54.34

MS Date

S APR 2\. )997

S JUN 23

S JUL 28

S AUG 25

S OCT 30

V NOV 25

S DEC 17

S JAN 29, 1995

S FEB 24

S APR 01

S MAY 27

S 53.41 S 52.52 S

Water level

50.83

49.62

MS Date

S MAR 18. 1997

S APR 21

Water level

MS

59.04 S

58.62 S 58.89 S

58. 13 S

58.29 S

5R.42 S

58.25 S

58.27 S

Water level

53. 13

52.02

52.97

52.16

51 .86

51.70

51 .55 51.60

51 .55

51.21

52.43

Water level

56.0R

54.80

MS

s S

S S

S

S S S

S S S

MS

s s

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 132 Location Number: 11N03W10CCCC01

Date

NOV 0[' 1993 DEC22

JAN 20. 1994 MAR 24

APR 22

MAY 31

JUN 21 JUl21 AUG 31

SEP 20

Water level

53.33

53.58

55.49 61 .24 59.47 59.69

49.88

50.12 53.70

MS Date

S OCT 27. \994

S NOV 22 S DEC 21

S JAN 25. 1995

S FEB 23

S APR 25 S MAY 24 S ,lUN 27 S ,1UL 25

54.2 1 S AUG 12

Water level

50,36

50.45

53.30 56.52 54.76

58.13 55.86 60.18

45.01

MS Date

S SEP 20. 1995 S OCT 25 S NOV 30

S FEB 05. 1996 S 22 S MAR 19 S APR 19 VP MAY 21

V JUN 20

47.76 V JUL 25

Well Number: 135 Location Number: 11 N03W11 BBBA01

Date

OCT 19 . 1995

NOV 30 FEB 13. 1996

22 MAR 19 APRI8

MAY 22

Water level

162.70

159.97 164,12

159.38 160,75

109,03

166.65

MS Date

S JUN 20, 1996 S JUL 25 S AUG 26 S SEP 20 S OCT 23 S NOV 26 S DEC 19

Water level

171.12 162.91 166.35 160.99 161.28

160.97 160,13

MS Date

S MAR 18.1997 S APR 21 S JUN 23

S JUL 28 S AUG 25 S SEP 23 S OCT 30

Well Number: 136 Location Number: 11N03W16BBBBD1

Date

JUl 25. 1990

NOV 03,1993

DEC22 JAN 20. 1994 FEB 24

MAR 24 APR 21 MAY 31 JUN 21 HJL21 AUG31 SEP 20

Water level

MS Date

50.81 S OCT 27. 1994

54.30 S

57.01 S 57.68 S

60.49 S 01.65 S 62.63 S 63.86 SR

64.24 SR 62,98 SP 57,53 S

51.81 S

NOV 22 DEC21 JAN 25. 1995

FEB 23 MAR22 APR 24 MAY 24 JUN 27

JUl26 AUG 22 SEP 20

Water level

MS Date

52.98 S OCT 25 , 1995

54.90 S

56.59 S 58.43 S

5R29 S 61.05 S 62.41 SR

60.90 SR

53.60 V

52.94 V

50.12 V

50.46 S

NOV 30 FEB 05. 1996

22

MAR 1& 19

APR 19 MAY 21 JUN10

JUL 25

AUG 26 SEP 20

Water level

48.48

49.90 52.25

56.22 59.45

57.55

67.07 60,44

59.48

MS Date

S AUG 26. 1996 S SEP 20 S OCT 23 S NOV 26

S DEC 19 S JAN 23, 1997 SP FEB 19 S MAR 18 SP APR 21

51.50 S

Water level

164.21 160.20 166.71 182.18

18 \.80

166.28 161.25

Water level

52.S5 55.25 53 .04 59.78

61.76 60.83

58.74

56.92

47.47 48.29

47.05

MS Date

S NOV 25, 1997 S DEC 17 S JAN 29. 1998

S FEB 24 S APR 01 S 28 S MAY27

MS Date

S OCT 23. 1996 V NOV 26 V DEC 19

V JAN 23. 1997

V FEB 19

V MAR 18

V APR 21

V

S

S

S

l'

Water level

50.89

49.92

51.37 00,56

56,20 54 ,53

55.64

55.97

Water le\lel

100.91 15<>.49

159.29

160.14 162.80 160.24 162.39

Water level

49.65

MS

P SP S

S

S S

S S S

MS

s S S S

S S S

MS

s 52.05 S 54.04 S 56.02 S 57.47 S

51U4 S 60.26 S

TABLE 4 93

Table 4. Records of water Icvels. Helena area bedrock, west-central Montana (Continued)

Well Number: 141 Location Number: 11 N03W18BBBC01

Date Water MS Date

Water MS Date

Water MS Date Water

MS level level level level

JUL 29. 1994 82 .S7 S FEB OS. 1996 87.46 S ,1UL 30, 1996 R2.22 V JAN 22. 1997 79.S9 S OCT26 80.96 S 23 82.47 V AUG 16 83.49 S FEB 19 80,42 S .IAN 25. 1995 82 .81 S MAR 21 83.19 V SEP 20 79.39 S MAR 18 81.62 S APR 21 RS.73 S APR 18 83.96 V OCT 22 78.22 S APR 21 R2 . 5~ S JUL 24 90.96 S MAY 21 84.66 V NOV 26 78.49 S OCT 26 RI .61 S JUN 10 84.22 \I DEC 19 78 .68 S

Well Number: 144 Location Number: 11 N04W02DBBC01

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

OCT 27. 1993 73.47 S OCT 27.1994 69.94 S SEP 20. 1995 70.01 S SEP 20. 1996 71.36 S DEC 22 69.72 S NOV 22 69.63 S OCT 25 73 .S5 S OCT 22 71.48 S JAN 20. 1994 67.17 S DEC 21 69.31 S NOV 30 72.85 S NOV 26 70.71 S FEB 24 69 . .30 S JAN 25 . 1995 67.39 S FEB 06. 1996 72.10 S DEC 19 70.43 S MAR 24 6S.10 S FEB 23 68.56 S 23 71.12 S .IAN 22. 1997 70. 15 S APR 22 64.92 S MAR 22 6&.46 S MAR21 70.11 S FEBI9 70.27 S .~IA Y 27 65 .20 S APR24 68.85 S APR 18 71.22 S MAR 18 69.35 S JUN 21 66.63 S MAY24 68.43 S MAY21 79.76 S APR 21 70.17 S JUL21 66.95 S JUN 27 71.93 V JUN 19 81.37 S AUG 31 66.49 S JUt 26 71.79 V JUL 30 69.30 S SEP 20 66.60 S AUG 12 73 .69 S AUG 26 71 .4g S

Well Number: 145 Location Number: 11 N04W06DACA01

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

OCT 27, 1995 38.70 S JUN 19, 1996 40.76 V JAN 22, 1997 38.83 S DEC 17. 1997 38. 15 S NOV 30 JR.62 V JUL 26 41.41 V FEB 19 39.41 S JAN 29. 1998 3!!.4S S FEB 13, 1996 39.)4 V AUG 26 42.32 S MAR 18 4001 S FEB 24 38 .21 S

23 38.41 V SEP 20 40.73 S APR21 39.70 S APROI )fL06 S

MAR 19 39.17 V OCT 22 40.47 S JUN 23 39. 13 S 28 38. 13 S

APR 19 39.24 V NOV 25 39.95 S AUG 25 38.97 S MAY 27 38.20 S

MAY 20 39.01 V DEC 18 40.01 S SEP 23 38.82 S

94 Hydrology of the HelenD Arell. Bedrock, West-Central MOniliRIl, 1993-98

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 146 Location Number: 11N04W06DCCC01 -------------------------Date

OCT 21. 1993

DEC21 .IAN 20.1994

MAR24 APR21 MAY 27 JUN 21

JUL 21

AUG 31

SEP 20

Water level

15.75

15.80

11.81

15.57

15.49

15.59

15.97

16.65

16.56

16.62

MS Date

S OCT 27, 1994

S NOV 22 S DEC 21 S JAN 25. 1995

S FEB 23 S MAR22 S APR 21

SP MAY 24

S JUN 26

S Jut 26

Water level

16.18

16.92

16.87

16.05

15.59

15.81

15.79

15.52 16.20

MS Date

S AUG 22, 1995

S SEP 20

S OCT 25

o NOV 30 S FEB 13. 1996

S 23

S MAR 19

S APR 19

V MAY 20 VR JUN 19

Well Number: 147 Location Number: 11N04W09ADAD01

Date

OCT 2R, 1995

DEC 02

FEB 06, 1996

23

Water level

MS

35 .10 S 34.03 V

34.39 V

30.10 V

Date

MAR 21.1996

APR 18

MAY 20 JlJN 19

Water level

MS

29.00 V 29.69 V

30.68 V

31.42 V

Date

JUL 25 . 1996

AUG 26 SEP 20 OCT 22

Water level

16.43

16.70

16.54

17.43

16.2::!

15.25

15.12

15.69

15.61 15.86

Water level

MS Date

V JUL 24. 1996

S AUG 26

S SEP 20

S OCT 22

S NOV 25 S JAN 22, 1997

S FEB 19

S MAR 18

S APR 21 S

MS Date

32.24 V NOV 25,1996

DEC 19 41.41 S

43.57 S 34. 19 S

MAR 18. 1997

APR21

Water level

20. 10

16.56

16.33

16.47

16.19

15.32 14.66

13 .28

!J.n

Water level

MS

S S S S

S S S

S

S

MS

34.76 S 35.04 S 34.19 S 22.95 S

---------------------------------------

Well Number: 149

Date

OCT 26,1993

DEC21 JAN 20. \994

FEB 24

MAR24 APR 21 MAY 27 JUL 21

AUG3!

SEP 20

Water level

10.68

11.49

11.98 12.73

12.59

14.38

14.25

16.63

17.52

I S.23

Well Number: 150

Date

OCT 26.1995

NOV 30

FEB 06.1996 23

MAR 21

Water level

86.47

73.95

74.20

73.49

75 .50

Location Number: 11 N04W09CBDD01

MS Date

S OCT 27.1994

S NOV 22

S DEC 21

S JAN 25. 1995

S FEB 23

S MAR 22 S APR 24 SR MAY 24

S JUN 26 S JUL 25

Water level

17.64

16.94

16.49

16.50

16.52

16.43

16.87

Ift .57

18.01 18.22

MS Date

S AUG 2\. 1995

S SEP 20

S OCT 25 S NOV 30

S FEB 06, 1996

S 23

S MAR 21 S APR 18

V MAY 20

V JUN 19

Location Number: 11 N04W09DBAA01

MS Date

S APR 18, 1996

V MAY 21 V JUN 19 V JUL 25

V AUG 26

Water level

74.99

70.88

72.42

73.68

76.28

MS Date

V SEP 20. 1996

V OCT 22

V NOV 25

S DEC 19 S JAN 22, 1997

Water level

19.74

20.2\

18.86

18.34

17.58

12.28

11.40 12.24

13.32

12.19

Water level

81.41

72.95 76.60 74.91

73.81

MS Date

V JUL 25. 1996

S AUG 26

S SEP 20

V OCT 22 V NOV 25

V JAN 22.1997 V FEB 19

V MAR III

V APR 21 V

MS Date

S FEB 19. 1997

S MAR 18 S APR 21

S

S

Water level

17.57

19.16

18.69

18.91

18.39

13.56

15 . IR 13.62

10.27

Water level

75.51 77.81

75.37

MS

V

S

S S S

S

S S S

MS

S S S

TABLE: 4 95

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 151 Location Number: 11 N04W1QADDD01

Date

OCT 22. 1993

DEC 22

JAN 20, 1994

FEB 24 MAR24 APR21 MAY 17 JUN 21

Water level

34.47

27.96

29.16 30.01

.31.06

30.98

MS Date

S JUL 21. 1994

S AUG 31

S SEP 20

S OCT 27 S NOV 22

S DEC 21 31.21 S JAN 25. 1995

53.39 R FEB 23

Water level

65 .69

78 .38

79.93

61.89

49.37

43.77

MS Date

SP MAR 22, 1995

S APR 21 S .ruN 27

S AUG 22 S SEP 20

S OCT 25

46.71 S NOV 30

40.41 S FEB 05. 1996

Well Number: 153 Location Number: 11N04W12CDOD01

Date

JUL 19, 1990

OCT 26.1993

DEC 22 JAN 20,1994

FEB 24 MAR 24 APR 21

MAY 31 JUN 21 JUl21

AUG 31

SEP 20 OCT 27

NOV 22

DEC21

Water level

MS

119.62 S 116.88 S

116.69 S

116.10 S

116.01 S

118.40 S

117.73 S

119.55 SR 124.55 S 122.98 S 123.17 S 124.30 S 118.39 S 120.35 S 118.42 S

Date

JAN 25, 1995

FEB 23

MAR 12

APR24 MAY 24 .ruN 27

JUl26

AUG 22 SEP 20

OCT 25

NOV 30

FEB 05.1996

23

MAR 19

APR 18

Water level

118.01

116.88

120.32

116.72 118.02

117,99

117.76

122.74 124.22

119.67

123.22

MS Date

S MAY 21,1996 S JUN 20

S JUL 30

S AUG 26

S SEP 20

V OCT 22 V NOV 26

VR DEC 19

S JAN 22. 1997

V FEB 19 S MAR 18

123.60 S 126.83 S 126,90 S

APR 21 .IUN 23

JUL 28

AUG 25 124,14 S

Well Number: 155 Location Number: 11 N04W13BDBB01

Date

SEP 22. 1995

NOV 30

FEB 13, 1996

Water level

IUUI

110.20

112.41

MS Date

S FEB 23, 1996

S MAR 21 S APR 18

Water level

106.70

106.33

MS

s s

106.10 V

Date

MA Y 21,1996 JUN 20

JUL 30

96 Hydr()logy Bf the HelenH Area 8edrork. We$t-Cenlnl M()ntaoH, \993-98

Water level

MS Date

37 .97

38.63

73.08

66.63

68.27

52 .61

S FEB 16. 1996 S MAR 19

V APR 18

V MAY 21 S JON 19

S JUL 25

51.25 S

44.96 S

Water level

MS

127.88 T

126.17 S

127.99 S

126.47 S 126.89 S

121.41 S 122.06 S 121.36 S 123.35 S 118,59 S IIR,65 S 121.16 S \30.12 S

130.23 S

125.06 S

Water level

IOlt02

116.44 121.78

MS

V

V

V

AUG 26

SEP 20

Date

SEP 23, 1997 OCT 30

NOV 25

DEC 17

JAN 29.1998

FEB 14

APROI 28

MAY27

Date

AUG 26. 1996

SEP 13

Water level

38.49

38.92

54.43

47.58

49.30

74.50

MS

S

S

S

S S

SR 55,28 S

W

Water level

123.~5

123.0<)

122,75

119.71

119.49

II <) ,07

118.92

122.93

123.75

Water level

122.63

127.40

MS

s S S S

S

S

S

S

S

MS

S S

Table 4. Records of water levels. Helena area bedrock, west-central Montana (Continued)

Well Number: 160 Location Number: 11N04W20BBCD01

Date

OCT 22.1993

DEC21 JAN 20. \994

FEB 24 MAR 24 APR 21

MAY 27

JUN 21

JUL 21 AUG31 SEP 20

Water level

82.47

82.48

82.46

82.49

82.53

82.57

82.61

1D.83 83.29

83 . 18

83.49

MS Date

S OCT 27 , 1994

S NOV 22

S DEC 21

S JAN 25, 1995

S FEB 23

S MAR 22

S APR 24 S MAY 24 SR JUN 26

S JUL 25

S AUG 22

Water level

R3. 13

83.09

83. 12 83.05

83.07

83.03

83 .04

83.06

83 .07

83.09

83.45

MS Date

S SEP 20, 1995

S OCT 25

S NOV 30

S FEB 06. 1996

S 22

S MAR 21

SR APR 19

S MAY 20

V JUN 19

V flJL 24

V AUG 26

Well Number: 161 Location Number: 11N04W20DCBD01

Date

OCT 19, 1993

DEC 21

JAN 20, 1994

FEB 24 M.AR 24 APR 21

MAY 27

JUN 21

JUL 21

AUG 31

Water level

89.84

73.59

8&.69 89.21

89.39

89.23

89.26

88.75

MS Date

S SfP 20, 1994

S OCT 27

S NOV 22

S DEC 21

S JAN 25. 1995

S FtB 23 S MAR 22 S APR 24

89.46 S

90.80 S

MAY 25

JUN26

Water level

88.57

89.52

89.48

89.45

89.49

89.44

89.45

89.46

MS Date

S JUL 25. 1995

S AUG 22 S SEP 20

S OCT 25 S NOV 30

S FEB 22. 1996

S MAR 21

S APR 18

R9.47 S MAY21 89.45 V JUN 19

Well Number: 163 Location Number: 11N04W24AAAC01

Date

OCT 29. 1993

DEC 22

JAN 20. 1994

FEB 24 MAR 24 APR 22

MAY 31

JUN 21

JUL 21

AUG 31

Water level

MS

73.92 S

74.44 S 75.03 S 75.37 S

75.99 S

75.79 S 75.59 S

74.23 S

77.65 SP

70.37 S

Date

SfP 20. 1994

OCT 27

NOV 22

DEC 21

JAN 25, 1995

FEB 23

MAR 22 APR 24 MAY 24

JUN 27

Water level

MS

69.64 SR

70.32 S 71.59 S 72.90 S 74.47 S

75.84 S

77.39 S 78.24 S

79.15 SR 76.15 V

Date

JUL26, 1995

AUG 22

SEP 20

OCT 25

DEC 03

FEll 06, 1996

22 MARl) APR 18 JUN 20

Water level

83.32

8.UI 83.1 R

83.19

82.74

82 .04

81.37

RI.33

81.49

R 1.84

79.09

Water level

89.45

89.57

89.58

85.96

89.49

92.76

84.87

85.98

MS Date

S SEP 2(]. 1996

S OCT 22 V NOV 25

V DEC 18

V JAN 22. 1997

V FEB 19

V MAR 18

V APR 21

V

V

S

MS Date

V JUL 25,1996

V AUG 26 S SEP 20

S OCT 22 S NOV 25

S DEC IR

S JAN 22,1997

S APR 21 78.32 S

79.15 S

Water level

71.23

69.99

70.38

71.77

73.96

74.90

75.38

74.06

73.17

MS Date

P JUL 25. 1996

VR AUG 26

S SEP 20 S OCT 23 V NOV 26 V DEC 19

V JAN 23. 1997

V FEB 19

V MAR 18 V

Water Jevel

82.05

82.20

82.24

82.28

82 .28

83.78

82.27

82 .06

Water level

83.84

89.07

89.13

89.09

89.29

84.69 83 .57

86.53

Water level

MS

SR S

S

S S

S S S

MS

s s S

S S S S S

MS

70.05 VP

68.13 S

67.74 SP

67.97 S 69.73 S

70.78 S

72.35 S

73.51 S

76.98 S

TABLE 4 97

Table 4. Records of water levels, Helena area bedrock, west-centTal Montana (Continued)

Well Number: 165 Location Number: 11 N04W24B BABO 1

Date Water MS Date

Water MS Date Water MS Date

Water MS level level level level

OCT 31. 1995 77.37 S JUN 20. 1996 75.18 S DEC 23. 1996 77.92 S OCT IS. 1997 80,47 S

DEC 02 73.54 S JUL 24 76.90 S JAN 27,1997 1'1.56 S DEC 16 77.06 S FEB 28. 1996 73.20 S AUG 26 74 .86 S FEB 28 84.14 S MAR 30, 1998 86.10 S MAR 25 72.98 S SEP 21 81.21 S MAR29 82.37 S MAY 12 ~3.95 S APR 27 72.88 S OCT 27 74.93 S APR 26 81.59 S

MAY 18 72.8~ S DEC OJ 79.29 S SEPI3 78.31 S

Well Number: 166 Location Number: 11 N04W2SBBDA01

Date Water MS Date

Water MS Date Water

MS Date Water

MS level level level level

OCT 21. 1993 132.57 S OCT n 1994 126.49 S SEP 20. 1995 197.24 S AUG 26.1996 P DEC 22 106.02 S NOV 22 111.05 S OCT 25 131.(.4 S SEP 20 197.71 S JAN 20. 1994 102.57 S DEC 21 117.72 S NOV 30 110.71 S OCT 23 178.22 S FEB 24 103.62 S JAN 25. 1995 111.28 S FEB 05.1996 115.97 S NOV 26 128.89 S MAR24 101.71 S FEB 23 118.64 S MAR21 112.17 S DECI9 114.92 S APR 22 106.95 S MAR22 105.00 S APR 18 118.92 S JAN 23. 1997 126.54 S MAY 31 106.93 S APR 25 117.38 S MAY21 116.91 S FEB 19 1()9.n S JUN 21 107.2_~ S MAY 24 159.25 SP JUN 20 168.74 S MAR [8 109.30 S SEP 20 116.99 S JUN 27 200.85 V JUL 30 165.20 S APR 21 105.45 S

Well Number: 168 Location Number: 11 N04W29CDBCQ1

Date Water MS Date

Water MS Date

Water MS Date Water MS

level level level level

SEP 0 I. 1995 97.40 V APR 19. 1996 79.77 V SEP 19. 1996 81.97 S FEB 19. 1997 86.76 S

NOV 30 82.40 S MAY 20 79.99 V OCT 22 84.37 S MAR 18 81.44 S FEB 12. )996 25 . .15 S JUN 19 81.95 V NOV 25 81.15 S APR 21 78.37 S

24 80.20 V JUL 24 109.43 S DEC 18 82.33 S MAR 19 78.63 V AUG 2() P JAN 20, 1997 7217 S

98 Hydrology of the Helena Arn Bt-drock, West-Cent .... 1 Monlana, \993-98

Table 4. Records orwater levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 169

Date

OCT 13. 1993

DEC20

JAN 20,1994

FEB 24

MAR24

APR11

MAY 27

JVN 21

JUL 21

I\VG 31

Water level

154.90

155.96

156.41

156.80

159.15

157.59

159.35

159.09

160.18

161.87

Well Number: 170

Date

OCT 15, 1993

DEC 22 JAN 19. 1994

FEB 23

MAR22

APR22

MAY 27

JUN 21

JlfL 21

AUG 30

SEP 20

Water level

71.51

69.37

68.22 67.57

72.97

72.53

71.36

67.77

75.22

75.01

78.33

Well Number: 171

Date

AUG 25. 1995

OCT 31

DEC OJ FEB 12, 1996

24

Water level

45.69

44.90

44.45

38.51

38,77

Location Number: 11 N04W30ACBC01

MS Date

S SEP 20, 1994

S OCT 27

S NOV 22

S DEC 20

S JAN 25. 1995

S FEB 22 S M.'\R 20

S APR 21

SR MAY 24

S JD N 26

Water level

164.55

161.09

160.39

165.56

161.73

162.81

163.35

163.35

163.75

165.16

MS Date

S mL 25. 1995

S AUG 21

S SEP 20

S OCT 25 S DEC 01

S FEB 12. 1996

S FEB 24

S MAR 19

S APR 19

S MAY 20

Location Number: 11 N04W32ADCB01

MS Date

S OCT 27, 1994

S NOV 21

S DEC' 20

S JAN 24. 1995

S FEB 22

S MAR 20

S APR 21

S MAY 24

S JUN 26

S JUL 25

S AUG 2 1

Water level

72.84

72.19 74.82

74.77

73.25

76.41

7lU4

77.78

74.45

69.27 73.93

MS Date

S SEP 19, 1995

S OCT 24

S DEC 01

S FEI} 12. 1996

S 24

S MAR 19

S APRI9

S MAY 20

V JUN 19

V JUL 25

V AUG 26

Location Number: 11N04W32BCAA01

MS Date

S MAR 19. 1996

S APR 19

V MAY 20

5 JUN 19

V JUL 24

Water level

37.79

38,35

39.06

40.88

44.20

MS Date

V AUG 26, 1996

V SEPI\)

V OCT 22

V NOV 25

S DEC IS

Water level

164.79

167.00

165.17

165.64

165.46

164.&4

163.47

157.65

159.57

161.50

Water level

71.89

71.:27

75.65

78.97

77.63

73.75

78.73

75.20

74.65

84.95

74.53

Water level

43.29

44.35

43.83

43.71

43.14

MS Date

V JuN 19. 1996

V JUL 24

S AUG 26

S SEP 19

S OCT 22

S NOV 25

S DEC 18

S FEB 19,1997

S MAR 18

S APR 21

MS Date

S SEP19,1996

S OCT 22

S NOV 25

S DEC' 18 V JAN 22. 1997

V FEBI9

V MAR If>

V APR 2t

V S S

MS Date

S JAN 22. 1997

S FEB 19

S MAR 18

S APR 21

S

Water level

153.74

157.o?

138.39

156.51

157.28

157.93

160.62

159.37

156.23

147.65

Water level

7R.47

77.33

77.29

7R.29 75.75

71,46 67.(,9

65.74

Water level

42.38

36.49

33.63

34.46

MS

S

S

S

S

S

S S

S S

S

MS

S

S S

S

S

S

S

S

MS

S S

S

S

TABLE 4 99

Table 4. Records or water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 173 Location Number: 11N04W34DABB01

Date

APR 13, 1992 SEP 14

NOV 10

MAR 30.1993 MAY 12

JUN 02 JUL 28

SEP 09 DEeDS

Water level

MS

105.00 S

105.83 S 106.06 S 105.91 S 105.54 S 105.48 S

105.24 S 105.09 S

103.70 S

Date

MAR 03, 1994

JUN 08

AUG 03 OCT 06

DEC 13 FEB 16. )995

MAY 31 SEP 28

OCT 31

Water level

MS

103.26 S

103.50 S 105.02 S

106.09 S

106.26 S 106.30 S 106.42 S 107.20 S

)08.80 S

Date

NOV 28,1995

JAN 24.1996

FEB 22

MAR 2)

APR 23

MAY 22 JUN 26

JUL 25

AUG 20

Well Number: 174 LocatIon Number: 11N04W34DCBA01

Date

FEB 12. 1977 MAY 09

JUL IS AUG07 OCT 02

DEC 03 MAR 10. 1979

MAY 19 MAY 23

AUG 12 MAR 12. 19R]

AUG 06

AUG 14. 1984

MAY 15. 1985 JUN IX JULI9 AUG 04

SEP 22

APR 18. 1986 MAY 25 APR 10,1987

JUL 28

MAR 14, 1988

Water level

15.3 15.6 15 .7 16.3 16.1

15.S

15.2

14.0 16.0

14.7 15.7 16.0 17.5 15.8 17.0

16.1

16.2 19.7 17.6 15.2 16.2 15.8

16.9

MS Date

S APR 29. 1988

s S

S

S S S S S S S S

S

S

S S S S S

S S S S

JUN 19 JUL 16

AUGI] SEP09 MAR 02, 1989 MAY 03. 1991

NOV 13

FEB 29. 1992

APR IS NOV 18.1993

DEC 20

JAN 19. 1994 FEB 23

MAR 22 APR26 MAY 25 JUN 20

JUL 11

AUG 30 Sf:P )9

OCT 26 NOV 21

Water level

MS Date

16.6 S DEC 20. 1994

16.9 S

17.3 S

17.9 S

17.2 S 16.3 S 16.7 S

17.7 S

17_1 S

17.1 S

16.45 S 16.59 S

16.62 S

19.89 S 16.62 S 16.75 S

17.53 S

16.79 S 19.06 S

17.91 S 18.79 S

17.70 S

17 .87 S

JAN 24,1995

FEB 22

MAR 20

APR26 MAY 22

JUN 27

JUL 25

AUG 21 SEP 19 OCT 24 NOV 28

JAN 24. 1996 FEB 22 MAR 21

APR 23

MAY 12 JUN 26

lUL 25 AUG 20 SEP 24

OCT 24

NOV 25

100 Hydrology o( the Hel~DQ An'''.! Bedrock. West-Central Montann, 1993-98

Water level

MS

107.96 S

106.57 S

106.44 S 107.19 S

105.70 S 106.33 S 107.02 S 106.36 S 106.03 S

Date

SEP 24,1996

OCT 24

NOV 25

DEC 20

JAN 23. 1997

FEB 26

MAR 26

APR 11

28

Water level

MS Date

17.67 S DEC 26, 1996

19.71 S

18.01 S

22.41 SP lS.21 S

17.33 S 16.39 S

16.49 V

17.10 V

16.99 S

16.63 S 17.61 S

17.83 S 15.22 S 15 .29 S !5.95 S

16.36 S

16. 13 S

17.14 S 17.27 S

17.63 S 16.57 S 16.84 S

JAN 23. 1997

FEB 27

MAR 20

26

APR03 MAY 03

MAY31 JUN 26 JUL 28

AUG 25 SEP 23

OCT 30 NOV 25 DEC 17 JAN 29, 1998

FEB 24

APROI 28

MAY 27

Water level

MS

106.08 S

106.16 S 105 .43 S 101.05 S

104 .74 S 104.40 S

103.81 S 103 .31 S 102.&0 S

Water level

17.69

17.20

15.67

14.20 14.82

14.20

14.75 14 .74

15.76 IS .08 17.16

16.34 16.32

16.44

16.50

16.4 7 16.56

17.33

16.67 16.67

MS

S

S

S S S S

S S

S S S S S

S S

S

S S S S

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 175 Location Number: 11 N04W35CCAA01

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

FEB 26.1992 84.97 S AUG 16, 1993 101.44 S DEC 13. 1994 103.69 S JUL 25. 1996 106.47 S MAR Jl 85.40 S SEP 01 100.92 S FEB 16. 1995 103.53 S AUG 20 128.94 S

MAY29 87. 17 S OCT 05 100.13 S APR 20 103,48 S SEP 24 109 .. ~4 S

JUL 30 89.31 S NOV 15 99.40 S MAY 31 103.73 S OCT 24 109.26 S

AUG 31 90.59 S DEC OS 99.09 S JUL III 104.51 S NOV 25 111.24 S SEP 29 90.80 S FEB 16. \994 98.67 S SEP 28 106.15 S DEC 26 108.06 S NOV 02 91.93 S MAR 03 98.61 S NOV 2.8 105.93 S JAN 23. 1997 10S.53 S FEB 03, 1993 98.00 S APR20 98.70 S JAN 24. 1996 105.61 S FEB 26 104 .79 S MAR03 100.05 S MAY 18 99.10 S FEB 22 107.76 S MAR 26 106.64 S

30 101.66 S JUN OR 99.44 S MARll 105.60 S APR 28 105 .86 S MAY Of> \ 03.47 S AUG03 103.00 S APR 23 105.65 S

12 \04.12 S SEP 09 104.04 S MAY 22 106. 16 S

JUN02 104.90 S OCT 06 104.37 S JUN 26 107.29 S

Well Number: 177 Location Number: 11 N05WO 3CAAD01

Date Water

MS Date Water

MS Date Water

MS Date Water MS

level level level level

AUG 23.1995 148 .65 T APR 19. 1996 125 .75 S SEP 19, 1996 129.99 S FEB 19. 1997 128.99 S NOV 30 139.00 S MAY 21 145 .61 SP OCT 22 126.65 S MAR 18 130.60 S FEB 12. 1996 138.35 S .1UN 19 134 .81 SP NOV 25 126.56 S APR 21 131.53 S

2J 136.97 S JUL 24 135.62 SP DEC 18 125 .52 S

MAR 19 131.64 S AU026 155.00 SP JAN 22.1997 133 .35 S

Well Number: 178 Location Numbe.r: 11 N 05W12C BCA01

Date Water

MS Date Water MS Date

Water MS Date

Water MS

level level level level

AUG 23,1995 38.46 S MAR 21,1996 34.59 S AUG 26, 1996 55.87 SP JAN 22. 1997 37.63 S OCT31 37.38 S APR 19 37.10 V SEP 19 39.71 S fEB 19 37.50 S DECOI 37,25 S MAY 22 37.25 V OCT 22 37.82 S MAR 18 37.51 S FEB 12. 1996 30.86 S JUN 19 37.96 V NOV 25 39.39 S APR21 36.28 S

24 36.76 V JUl24 39.19 V DEC 18 38.58 S

TABLE 4 101

Table 4. Records of water levels, Helena area bedrock, west-central Montana (Continued)

Well Number: 180 Location Number: 11 N05W14ADAA01

Date

OCT 15. 1993 DEe21 JAN 20 MAR 24 APR21 MAY 27 JUN 21

JUL 21 AUG31

Water level

57.7R 97.19

75 .39 75.87

75.95 81 .30 90.87 79.81 i6.92

MS Date

S SEP 20. 1994

S OCT 27 S NOV 22

S DEC 21 S JAN 25,1995 SR FEB 23 SR MAR 22

S APR 21 SR MAY22

Water level

97.67 9959

112.49 119,49

130,42

137.49 135.04 147.97

151.90

MS Date

SR JUL 25, 1995 S SEP 22 S OCT 25 S FEB 24. 1996

S APRI9

S MAY 19

S JUN 19 S JUL 10 S JUL 24

Well Number: 182 Location Number: 11N05W14DDDD01

Date

AUG 29, 1995

OCTJI DEC 02 FEB 12. 1996

MAR 19 APR 19 MAY 20

JUN 19

Water level

30.95 30.90

31.75 32.62 31.76

34.87

31.74 31.92

MS Date

S JUL 24, 1996 S AUG 26 V SE.PI9 S OCT 22 S NOV 25 S DEC 18 V JAN 22. 1997 V FEBI9

Water level

32.78

36.02 42.67

33 .26 33.04 J3.47 33.33

33.59

MS Date

V MAR 18. 1997

S APR 21 S JUN 23

S JUL 28 S AUG 25 S SEP 23 S OCT 30 S NOV 25

Well Number: 183 Location Number: 11 N05W15DBAA01

Date

OCT 13. 1993

DEC21 JAN 20. 1994

FEB 24 MAR 24 APR 21 MAY'!.? JUN 21 JULlI AUG 31

Water level

MS

47.44 S

47.73 S 48.66 S 49.07 S 48.23 S 48.63 S 4R.75 S

4.8.45 S 4R.66 S

50.60 S

Date

SEP :W. 1994 OCT 27

NOV 22 DEC21 JAN 25. 1995 FEB 23 MAR 22 APR 21

MAY 24

JUN 26

Water level

MS

50.23 S

49.52 S 49.23 S 48.58 S 47.79 S

47.46 S 45 .51 S

48.61 S 48.67 S 49.30 V

Date

JUL 25. 1995 AUG 22 SEP 20 OCT 25

DECOI

FEB 12, 1996 MAR 19

APR 19 MAY 19

JUN 19

102 Hydrology oflhe Helen>!. Area l3edrock, West-Central Montana. 1993-98

Water level

155.30 135.41 155.19

156.60

143.12

103.70 127.91 145.&5 152.62

Water level

32.97

30.84 34.22

32.59 32. 11 30.93 30.93 31.12

Water level

49.18 4959 49.25 49.60 50.43

39.45 42.93 45.33 46.02 46.34

MS Date

VR AUG 26,1996 SR SEP 19 S OCT 22 SP NOV 25

S DEC 18 S JAN 22. 1997

S FEB 19

S MAR 18 S APR 21

MS Date

S DEC 17. 1997

S JAN 29. 1998 S FEB 24

S APR 01

S 28 S MAY 27

S

S

MS Date

V JUL 24. 19\)6

VR AUG 26 S SEPI9 S OCT 22 T NOV 25 V DEC IR V JAN n 1997 V FEB 19

V MAR 18 V APR 21

Water level

148.07 148.09

14&.22 148.03 147.29

146.19 145.37 124.i2

143.5.1

Water level

31.37 31.67 31.42 33.59 31.94 3:UO

Water level

48.3)

47.95 47.92

48.21 47.67 46.43

46.48

44.8 1

48.83 46.72

MS

S S S

S S S

S

S

S

MS

s s S

S S

S

MS

V

S S

S

S

S

S

S S

S

Table 4. Records of water levels, Helena area bedrock , west-central Montana (Continued)

Well Number: 187 Location Number: 11N05W23CBAA01

Date

OCT 13. 1993

DEC 21 JAN 20. 1994

FEB 24

MAR 24 APR 21

MAY 27 JUN 21

JUL 21

AUG 31

Water level

MS

43.22 S

45.67 S 44.75 S 45 .11 S

45.45 S

45.47 S

45.69 S 46.52 S 48.59 S

49.03 S

Date

SEP 20. 1994

OCT 27 NOVn DEC 21

JAN 25, 1995

FEB 23

MAR 22

APR21 MAY 24 JUN 26

Water level

MS

48.97 S

47.60 S 47.31 S

46.94 S

46.90 S 46.74 S 47.04 S 47 .12 S 46.99 S 95.25 VP

Date

JUL 26. 1995 AUG 22 SEP 20

OCT 25

DEC 02

FEB 12. 1996

24

MAR 19 APRI9 MAY 20

Well Number: 188 Location Number: 11 N05W24DCBD01

Date Water level

MS Date Water level

MS Date

AUG 31. 1995 123.56 V MAR 19.1996 92.04 V JUL 25. 1996

AUG 26 DEC 02 97.89 S APR 19 97.29 V

FEB 12. 1996 25

97.59 V MA Y 20

114.87 V JUN 19

103. 11 V SEP 19 112.82 V OCT 22

Well Number: 189 Location Number: 11 NOSW2SBCCC01

Date

OCT 13. 1993

DEC 21 JAN 20, 1994

FEB 23

MAR 24

APR 21

Water level

63.99 6356 64.00

64.38 64,88

64.75

Well Number: 190

Date

AUG 31,1995

OCT 31

DEC 02

FEB 12. 1996

24

Water level

112,42

104.95

109.49 132.11

94.08

MS Date

S MAY 27. 1994

S ]UN 20

S JUL 21

S AUG 31

S SEP 20 S OCT 27

Water level

65.21 78.79

93.79 68.73

69.19

70.16

MS Date

S NOV 22. 1994

SR DEC 20

SP JAN 25. 1995

S FEB 23

S MAR 22

S APR 21

Location Number: 11N05W2SDBCC01

MS Date

S MAR 19. 1996

S APR 19

S MAY 20 SP JUN 19 S JUL 24

Water level

104.17

50.58

88.30

81.12 86.40

MS Date

S AUG 26. 1996 S SEPI9

S OCT 22

S NOV 25

S DEC 18

Water level

49.05 50.55

50.77

48.68

47.:\7 41.58

41.16

42.25

41.94 43 .54

Water level

MS

v V

S

S V

V

V

V V

V

MS

Date

JUN 19. 1996

JUL 24

AUG 26

SEP19 OCT 22

NOV 2)

JAN 22. 1997 APR 21

Date

12663 V APR 21, 1997

P 13124 S 129.96 S

Water level

79.62 68 .79

69.26

67 .57

67.63

67.45

Water level

91.11 88.69

89.35 94.01

96.72

MS Date

SP MAY 24.1995 S JUN 26 S JUL 25

S AUG 22

S SEP 20

S

MS Date

S JAN 22, 1997

S FEB 19

S 1I.·1AR 18 S APR 21

S

Water level

45.72

48.26 47 .64 48.26

47 .92 47 .83

45.23

32AO

Water level

MS

V

V

S S S S S

S

MS

85.69 S

Water level

72.03

88.54

108.37

70.)0

77.19

Water level

89.97

76. 18

68.21

61.12

MS

S SP VP VR S

MS

S S S

S

TABLE 4 ln3

Table 4. Records ofwaler levels. Helena area bedrock. west-central Montana (Continued)

Well Number: 193 Location Number: 12N03W31DBBB01

Date

OCT 23. 1995

NOV 30

FEB 05.1996

22 MAR 20

Water level

61.64

56.54

51.20

MS Date

V APR O( 1996

V MAY 21 V JUN 20

49.R4 V .IUl25

48 .20 V AUG 26

Water level

47.56

48.24

52.81

MS Date

V SEP 20. 1996

V OCT 22

V NOV 26

69.17 V DEC 19

78.07 S JAN 22. 1997

Well Number: 194 Location Nu mber: 12N03W31 DDAC01

Date

NOV 09, 1993

DEC 22 JAN 20, 1994

FEB 24

MAR 24

APR]1

MAY)I JUN 21

JUl21

AUG 31 SEP 20

Water level

20.37

16.67 16.88

16.79

17 .62 17.12 17.25

17.66

18.69

MS Date

S OCT 27. 1994

S NOV 22

S DEC 21

S JAN 25. 1995

S FEB 23

S MAR 22 S APR 24

S MAY 24

S JUN 27 21.83 S JUL 26

AUG 22 28.04 S

Water level

28.96

20.76

18.74

19. 16 19.29

18.50

18.93

18.73

15.07

MS Date

S SEP 20.1995

S OCT 25 S NOV)O

S FEB 05. 1996 S 22 S MAR 19

S APR 18

S MAY 21

V JUN 20

16.07 V JUL 25

16.20 VP AUG 26

Well Number: 195 Location Number: 12N03W31DDBD01

Date

NOV 09,19<)3

DEC 22

JAN 20. 1994

rEB 24 MAR24

APR 21

MAY 31

JUN 21 JUL 21

AUG JI

SEP 20

Water level

56.22

56.40

56.90

57.47

57.44

57.35

5875

MS

s s S S

S

S S

(i 1.77 SP

63.64 SP

68. 17 S

70.17 S

Date

OCT 27, 1994

NOV 22 DEC 21

JAN 25, 1995

FEB 23

MAR 22

APR 24 MAY 24

JUN 27

JUL 26

AUG 22

Water level

71.98

72.28 72.12

70.74

68.48

69.66

70.JR

70.15

66.05

61.83 61.89

MS

S S S S S S S

S

V V

V

Date

SE!' 20. 1995

OCT 25

NOV 30

FEB OS. 1996 22

MAR 19 APR 18 MAY21 JUN 20 JUL 25

AUG 26

104 Hydrology of the Helena Area Dedrock. We-5I·Cc:nlrsl Montana. 1993-98

Water level

MS Date

76.34

71.64 65.17

S FEB 19. 1997

S MAR 18

S APR 21

61.94 S 59.47 S

Water level

MS Date

18.23

17.77

18.59

19.36

16.17

15.22 15.82

16.58 17.40

S SEP 20. 1996

S OCT 22

S NOV 26

S DEC 19 V JAN 22. 1997

V FEB 19

V MAR 18

V APR21

V

17.90 V

19.46 S

Water level

MS

62.04 S 59.67 S

59.60 S 59.42 S

5~ .07 V

56.08 V 54.87 V

54.93 V

56.22 V

63.50 V

66.26 S

Date

SEP20.1996

OCT 22

NOV 26

DEC 19 JAN 22 . 1997

FEB 19

MAR 18 APR21

Water level

56. 12

53.97 52.39

Water level

20.27

20.42

.20.54

20.42

20. 12

15.68 16.14

13.74

Water level

66.05

67.85

66.71 66.98

67.92 69.13

62,87

56.26

MS

s s s

MS

s S

S

S

S S

S S

MS

s s s S

S

S

S S

Table 4. Records of water levels, Helena area bedrock, west-cenlral Montana (Conrinued)

Well Number: 196 Location Number: 12N05W34DDDA01

Date Water

MS Date Water

MS Date Water

MS Date Water

MS level level level level

AUG 30, 1995 93.23 S MAR 19, 1996 80.78 V AUG 26,1996 89.87 S FEB 19, 1997 90.83 S OCT31 93.64 S APRI9 85.71 V SEP 19 91.19 S MAR 18. 90.23 S NOV30 93.79 V MAY 20 94.88 V OCT 22 90.48 S APR 21 88.14 S FEB 01. 1996 92.30 S fUN 19 96.93 V DECI7 91.51 S

23 90.37 V JUL 24 92.55 V JAN 23,1997 93.45 S

Well Number: 199 Location Number: 12N06W36BCDDO 1

Date Water

MS Date Water

MS Date Water

MS Date Water MS

level level level level

OCT 07.1993 17.72 S JAN 25,1995 21 .50 S APR 19,1996 11.62 V JUt 2R, 1997 P

DEC 21 18.91 S FEB 23 20.02 S MAY 20 14.59 V AUG 25 IR.IO S JAN 20.1994 19.41 S MAR 22 20.35 S JUN 19 16.36 V SEP 23 13.54 S FEB 24 19.77 S APR 24 20.11 S JUL 24 16.78 V OCT 30 19.18 S MARl4 19.10 S MAY 24 15 . 15 S AUG 26 17.54 S NOV 25 20.05 S

APR 21 17.89 S ruN 26 17.20 VP SEP 19 18. 13 S DEC 17 20.61 S

MAY 27 15.!!5 S JUL 26 14 .112 V OCT 22 19.38 S .IAN 29.1998 20.93 S JUN 21 16. 17 S AUG21 17.5 I V NOV 25 20.21 S FEB 24 20.14 S

JUL 21 17.50 S SEP 20 18.74 S DEC 18 20.61 S APROI IlU;4 S

AUG 31 22.69 sr OCT2S 16.59 S JAN 22. 1997 20.40 S 28 19. I II S

SEP 20 21 .22 S NOV 30 19.67 V FEB 19 20.82 S MAY 27 18.09 S OCT 27 19.46 S FEB 12, 1996 18.36 V MAR 18 18.76 S

NOV 22 20.22 S 23 17.90 V APR 21 16 .79 S DEC 21 21.14 S MAR 19 16.58 V JUN 23 16.37 S

TABLE 4 105

o ... .~ ci. .. " Q ~ 2-:;.

., :t: " ;:;: ::l .. .. ... .. " txI .. C

o

6 " T ~

~

h '" ::l q­!!!.

~ !:. .. ::l 1" -0

-0

w

~

oc

Table~.

Physical properties and m

ajo

r-ion

and tmce

-dcm

en

! concentrations in un

fillere

d w

ater s~mplcs eoll.::eted from selected w

ells

[Annlyses by Illlcnnuunlnin Laboratorit'~ and E

nerg), Laboralorics. O

nsilc IlllralC conccnlr.llion w,'\~ detcnnined by Ihl:' sam

pler u;m

g a speclropholom

clcL

LocJtio

n number describcd in rex!.

Abbreviations: A

rea: N

H. N

onh I-lill;,: SO. ScrBt~hgra"d 1·lills: W

tvl. western mount~in~

: SI-I. Soulh Hills.

AllU

ircr code or prodU

Cing uni.: 211 B

LD

B. U

pper CrclacenllS intrusive rocks: 2

tt SGV

H,

Upper ('rcl~ccoIIS Sc-ralcllgfavel H

ills intrusiw

roch; 211 M

RV

L, U

pper Cret~ccnllS Marysville intrusive rocks: 11 I E

LK

M. U

pper CrelaccO

lis Elkhorn M

ountains volcanic rocks: J20rSL

V .

Pennsylvani~n Syslem; D

I tvlSNC

, Low

er MississiPI>ian M

isS101I Canyon L

imestone: 34IJP

RS

. Upper and M

iddk Dcvoninn Jelfcrson form

allnn; )7IHM

RK

, Upper and M

iddle Cam

briJn Hasm

ark ronnation

; 420MSL

D. tvlirldle Proterozoic M

ount Shields Fonnation; 420SP

RD

. Middle PrO

lcroloic Shepard Fonnalion: 420SSLP, M

iddle Proterozoic SI1(lw~lip FonnatlOn: 4

~OHF.LN, M

iddle

PrOlerO

l.oiL' Helena F

onnalion: 420EM

I'R, M

iddle Prolerozoic Em

pire Fomlalion; 420SI'K

N. M

iddle Pm!er(1zoic Spokane Form

alinn; 420GR

SN, M

irldle Protcro7o;c Grey~on Form

ation. or. degrL'CS

Cel.,ius; ,IS

/em. miCTosiemcn~ p~r cenlim

eler at 15 dcgrees Celsius; m

glL. m

illigrams per liler: ).!giL. m

icrogrnm~ per lilC

r. Symbols: <

, ks.<; Ihan m

inimum

reponing level: -. 110 data)

Well

nu

mb

er

) (i

II 9

12 19 19 21 22

24 24 26 30 34 35 39 46 51 55

60 61 64 67 73 75 80 85

87

87

Lo

catio

n n

um

ber

09N03W

03CD

DA

OI

09N03W

05AB

DC

OI

09N03 W

07CB

CC

O 1

09N03W

09AB

13CO

I 09N

03WI4D

AC

CO

I 09N

04W10C

BB

AO

I 09N

04WIO

CB

BA

OI

09N04W

IICC

CB

OI

09N04W

1ICD

BD

OJ

09N04W

I2BD

CA

OI

09N04W

I2BD

CA

OI

09N04W

I2CC

BB

OI

09N04W

I6BA

CB

OI

09N05W

I2AC

AD

OI

09N05 W

12CC

DA

O 1

09N05W

29DD

CC

O 1

ION

03W20C

CA

AO

I IO

N03W

29BD

CC

OI

I ON

O)W

32BC

BD

O I

I ON

04 W02C

BA

AO

I 1 ON

04 W02C

DC

DO

I lO

N04W

03AD

BD

O I

ION

04W03D

AD

AO

I 1 O

N04W

08DC

AC

O I

10N04W

IOC

CD

DO

I I O

N04 W

23CA

DD

O 1

I ON

04W25A

CD

BO

1 I O

N04 W

26A B

AC

O I

ION

04W26A

BA

CO

I

Area

SH

SH SH SH

SH

SH

SH

SH SH

SH SH

SH SH

W

M

WM

W

M

SH

SH

SI-! SG

SG

SG

SG

W

M

WM

SH

SH

SH SH

Date

sam

ple

collec1ed

08-15-96 08-09·96 01<-07-96 08-09·96 03·02-94 203-02-94 10 3.02-94

08-08-96 03-02-94 09-04-96 01-29-98 08-08-96 09-04-96 03-06-94 09-04-%

O

R-13·96

05-04-94 09·04-96 0)·02-94 03·03-94 O

R-21-96

09-05·96 09·05-%

08-19-96 03-05-94 03-02-94 09-04-96 20~·13-96 208 -13-96

Aq

uife

r co

de

of

pro

du

cing

u

nit

420HE

LN

J41JF

RS

211B

LD

B

211BL

DB

371H

MR

K

331MSN

C

211BL

DB

211B

LD

B

320PSLV

211BLD

13 211 B

LD

B

21113LDB

211B

LD

B

211BL

DB

420H

EL

N

420HE

LN

420H

EL

N

211SGV

H

211SGV

H

211SGV

H

211SGV

H

420HE

LN

420SPK

N

420HE

LN

420H

EL

N

420HE

LN

De

pth

of w

ell

(fee

t)

656 620 ISO

750 145 87

122 124 IJO

249 191 300 260 278 100 200 140 110 46

103 87

120 201 130 185 255

Sp

ectfic

con

du

ctan

ce,

on

site

(fl S/ cm

)

536 391 314 548

495 288 288 425 265 312

646 299

353 485 486

1.360 611

1,120 481 776

500 492 444

780 546 840 788 788

Sp

ecific

con

du

c­ta

nce

, la

bo

rato

ry (IlS

/em)

568 364 287 558 600 290 300 435 )0

0

320

616 307 382

500 180

1,500 630

1,200 470 818 512 501 473

850 590 960 801 813

pH

, o

nslle

(sta

nd

ard

u

nits)

la6.S·S

.S

7.6

7.6

7.1 7.7 7.8 7.1< 7.8 7.0 7.5 7.4

7.8 6.0 7.2 6.9 7.8 7.3 6.1 7.8 7.8 7.2 7.R 7.7 7,7

7.5 7.8 6.3 7.4 7.4

pH,

lab

ora

tory

(stand

ard

un

its)

7.7 7.4 6.9 7.4 7.5 7.3 7.4 6.6

6.7

7.6

7.1 7.5 7.0 7.0 7.2 7.4 7.5 7.7 7.5 7.3 7.6 7.6

7.7 7.5 7.5 7.5 7.2 7.3

Wa

ter

temp

erature,

on

site

(OC

)

14.0 12.0 7.5

11.5

15.0 3.5 3.5

7.0 7.5 7.0

8.0 8.0 9.0 9.0 8.0

11.0 12,0

11.5 10.0 11.5 10.5 11.0 10.0 11.0 15.0 12,0 13.5 13.5

Calciu

m,

tota

l (m

g/L

)

31 47 43 80 58 41 40 59 37 42

89 37 48

76 21

140 46 85

58 83 64 59 42 60 56 60 65 65

Tobie 5.

Physical properties and major-ion and Irace-elem

ent eoneenlTalions in unfihered w

aler samples collected from

scl<::cted wells (C

onlinued)

Ma

gn

e-

Po

tas-

Su

lfate

, C

hlo

ride

, N

itrate

, N

itrate

A

rsen

ic, B

ariu

m.

Well

sium

, S

od

ium

, siu

m.

Alka

linity

tota

l to

tal

Flu

orid

e

on

stte

plu

s to

tal

tota

l

nu

mb

er

tota

l to

tal

tota

l (m

glL

as (m

g/L

) (m

g/L

) (m

g/L

) (m

g/L

n

itrite

reco

vera

ble

re

cove

rab

le

(mg

/L)

HC

03

) 1a25D

; 1c4

(mg

/L as N

) (1-l9/L)

(~g/L) (m

g/L

) (m

g/L) lbS OO

18250 a

s N)

1(:10 1cSO

1c2,000

3 27

37 9

201 120

14 0.32

<0.5 <0.05

16 6

17 8

2 256

28 3

.29 <.5

.42 <2

8 9

6 3

182 28

2 .12

<.5 .5 I

<2 9

15 13

3 180

130 8

.21 .29

2S 12

26 23

5 250

83 10

1.1 .30

<5 <500

19 C)

6 3

140 29

4 <.10

.37 <5

<500

19 9

7 3

140 29

5 .10

.37 21

12 8

3 152

71 5

.11 <.5

. 34 <2

22 9

6 '2

130 30

4 <.10

.53 <5

< 500 24

8 7

<I

168 4

<1

. 14 <.05

<2

24 <5

26 14

8 4

145 31

86 .10

4 5.4

<2 30

12 5

4 158

28 2

<.10 2

1.4 <2

34 10

JO 3

ISO 28

22 <.10

3.2 <5

<500

35 "

13 3

250 69

3 .15

.26 <2

39 5

5 2

77 15

<I

.11 <.5

<.05 5

46 66

67 4

440 250

73 .20

24 <5

< 500 51

19 55

10 239

80 3J

.65 1.5

5 5S

41 S3

42 340

IRO 62

1.0 17

8 <500

60 20

18 200

56 23

.60 2.1

<5 <500

61 30

41 2

427 68

11 1.4

:1 .91

3 64

16 13

<I

244 61

I) .62

3 2.9

<2

67 17

15 <

I 251

4 <

I .79

5 3.0

<2 73

26 12

3 230

44 7

.37 AD

6 -l

75 51

36 5

370 ~

100 18

.70 .60

<5 < 500

1;0 !W

26

17 3

230 59

18 .20

3.9 <S

<500 r t"'l

85 44

98 .3

422 120

39 .33

4 5.0

<2

Vl

87 42

35 .3

267 110

44 .25

4 6.4

<2

e 87

42 35

.3 266

112 44

.23 6.3

<2

-l

~

Tllble 5.

Physical properties and ma

jor-io

n and trace-elem

ent concentrations in u

nfilte

red

wa

ler sam

ples co

llected rTom selected w

ells (Co

ntin

ue

d)

=

00

:r; .<

Q.

6 g Q

... ;. '" :c '" ;;-=

M

an

ga

ne

se. M

ercu

ry, S

ele

niu

m,

Zin

c, ..

Ca

dm

ium

. C

hro

miu

m,

Co

pp

er.

Iron

, Lead,

>

tota

l lo

tal

tota

l to

tal

tota

l to

tal

tota

l to

lal

tota

l ~

We

ll ..

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

~

nu

mb

er

(~g/L) (f/gtL)

(~g/L) (/Lg/L)

(p.~/L) (~g/L)

(!l9/L

) (f/g/L)

(f/g/L) .. Q

. .,

1CS

1c100 1d1.300

18300 1 1

5

1aSO

1"2 1c50

1a5.000 <:> n ~

~

3 <

I <

10 580

<2

330 '"

6 2

<10

340 2

600 '" 'i C

i 8

<10

30 <

2 10

'" ~ 9

<I

<10

260 <2

560 ., ~

~

12 <

I <

10 250

<S <

20 <0.2

<5 ~

19 <

I <

10 5.000

<S S3

<.2 <5

;:; '" 19

::I

l'

~

21 30

360 16

250

'f 22

<I

<10

<50 <S

<20 <.2

<5 "D

Q

o

24 28

380 10

<2 20

24 <

I <

10 <30

<5 <

10 26

<I

<10

70 <2

80 30

<I

<10

<10

<2 10

34 <

I <

10 830

17 <20

<,2 <5

35 <

I <

10 <

10 <2

510 39

2 <

10 90

<2 20

46 <

1 <

10 40

<5 <2

0 <.2

<5 51

<I

<10

<10

<2 10

55 <

I <

10 410

<5 <20

<.2 <5

60 <

I <

10 50

<5 <20

<0.2 <5

61 <

I 10

<10

<2 20

64 2

<10

<10

<2 30

67 <

I <

10 <

10 <

2 170

73 <

I <

10 <

10 <2

10 75

<J

<10

<50

<5 <20

<.2 <S

80 <

I <

10 <50

<S

<20 <.2

<5 85

<I

<10

<10

<2 )0

87 <

I <

10 20

2 20

87 <

I <

10 <

10 <2

20

-i

;l>­cc .... r" 'Jo

o ..,

Tab

le s. P

hysical propenies and major-ion and trace-elem

ent concentrations in unfihered water sam

ples collet:led From selected w

ells (Continued)

Well

nu

mb

er

88 9&

100 102 104 106 112 113 115 123 125 130 133 135 142 144 145 146 ISO

151 155 161 163 165 166 168 170 170 171 173 174 175

178

IRO

182

Lo

catio

n n

um

be

r

I ON

04W26B

AA

AO

I JO

N05W

09BD

BC

OI

ION

05W25D

BD

AO

I IO

N05W

32AC

CA

OI

I ON

05W33 B

CD

DO

I IO

N05W

33CD

CD

OI

I ON

05W36D

AD

DO

I IO

N06W

OIC

DA

BO

I 11N

02WI8B

DC

BO

I I I N

03W04A

BA

DO

1 I I N

03W05C

CB

CO

I II N

03W09A

BB

BO

I II N

03WIO

DA

BB

OI

I IN03W

I IBB

BA

OI

I I N04W

OlA

AD

AO

I I I N

04W02D

BB

CO

I I I N

04W06D

AC

AO

I I I N

04W06D

CC

CO

I 11 N

04W09D

BA

AO

I 11N

04WIO

AD

DD

OI

IIN04W

I3BD

BB

OI

IIN04W

20DC

BD

OI

IIN04W

24AA

AC

OI

II N04W

24BB

AB

O I

I I N04W

25BB

DA

OI

I I N04W

29CD

BC

OI

l1N04W

32AD

CB

OI

1 I N04W

32AD

CB

OI

I I N04W

32BC

AA

OI

II N04W

34DA

BB

O I

11 N04W

34DC

BA

O I

11N04W

35CC

AA

OI

IIN05W

12CB

CA

OI

IIN05W

I4AD

AA

OI

IIN05W

14DD

DD

OI

Area

SH W

M

WM

W

M

WM

W

M

WM

W

M

NH

N

H

NH

N

H

NH

N

H

NH

N

H

NH

W

M

NH

N

H

NH

W

M

NH

N

H

SG

WM

W

M

WM

W

M

SG

SG

SG

WM

W

M

WM

Date

sam

ple

co

llected

09-06-96 08-21-96 09-04-96 08-15-96 08-13-96 08-13-96 03-02-94

08-21-96 08-21·96 03-05-94 08-09-96 08-20-96 08-20-96 08-21-96 09-06-96 08-20-96 08-20-96 03-05-94 08-08-96 03-03-94 O

R-20-96

03-05-94 03-05-94 0

8·2

0-9

6

03-03-94 08-19-96 20

3-05-94

203-05-94

08-19-96 08-21-96 03-03-94 09-05-96 08-19-96 08-19-96 08-19-96

Prin

cipa

l a

qu

ifer

cod

e

420I-lEL

N

211BL

DB

211B

LD

B

211BL

DB

211E

LK

M

211BL

DB

211B

LD

B

420I-lEL

N

420GR

SN

420GR

SN

420SP

KN

420S

PK

N

420SP

KN

420S

PK

N

420GR

SN

4.20G

RSN

420S

PK

N

420SP

KN

420S

PK

N

420SPKN

420S

PK

N

420HE

LN

420S

PK

N

420SP

KN

211SG

VH

420H

EL

N

420EM

PR

420HE

LN

211SG

VH

211SG

VH

211S

GV

H

420HE

LN

420H

EL

N

420HE

LN

Sp

ecific

Depth o

f we

ll co

nd

ucta

nce

, (feet)

on

site

390 280 155 160 280 135 220 130 220 140 110 240 420 350 130 140 50

115 400 157 230 160 100 120 373

205 500

125 180 125 1{;7 135 )8

9

500

(J.lS/cm

)

387 468 537 461 292 596 220

555 704

675 480 840 513 408 474 388 854 888 445 J7!)

858 548 888 885

4,490 653

1,200

1.200 753

690 5

\0

557 330

351 553

Sp

ecific

con

du

c­ta

nce

, la

bo

rato

ry (liS

/em

)

420 505 548 482 297 607 230 581 737

730 490

884 569 434 470 415 929 950 419 410 894 590 940 924

4,500 703

1,300 1.300

813

722

510 560 363

374 577

pH,

on

site

(stan

da

rd

un

its) laS.S_B

.S

7.9 7.3 7.2 7

,)

7.7 7.0 7.S 7.1 7.5 7.6

7.8 7.7 7.4

7.8 7.6

7.4 7.6

7.5 7.4

7.9 7.6

7.7

7.4 7.1 7.4 7.5 7.7

7.7 7.3 7.2 7.8 7.5 7.4

7.7

7.4

pH,

lab

ora

tory

(stan

da

rd

un

its)

7.6

7.3 7.2 7.4 7.3 6.9 6.5 7.3 7.4 7.6 7.6 7.8 7

7

7.7

7.5 7.6 7.6

7.6

7.5 7.7 7.7 7.7 7.6 7.3

7.2 7.6

7.5 7.5 7.5 7.3 7.5 7.4 7.5 7.6 7.7

Wa

ter

temp

erature,

on

slte

(DC

)

11.5

9.0 10.0 s.O

10.5 9.5

10.5 8.0

12.0 10.5 11.0 12.0 16.0 17.0 11.0 11.0 11.0 9.0

13.5 11.0 12.0 9.0

10.0 10.0 13.0 10.0 10.5 10.5 10.5 11.0 10.5 11.5 12.0 11.5 11.0

Ca

lcium

, to

tal

(mg

/L)

38

53

67

61 36 55 21 75 68 82 41 52 47 32

56 45 76

120 29

28 51 47 94

110 520

49

87

88 61 90 78 78 34 34 32

o ::t: ' .. ~ ... c C

~ 2-;.

,., ::t ~

iO

" .. > ., '" .. a

I .. 0

. .... o ... r ~

~ h '" ::> ::; !:. s: c ::> ;;; ::r 1" 'c> \C

>

't> \0

Q

c

Tab

le S. P

hysical properties and major-ion and rrnce-elcm

ent concentrations in unfiltered w

ater samp

les collected from selected w

ells (Continued)

Well

nu

mb

er

88

98

100 102 104 106 112 113 115 123 125 130

133

135 142 144 145

146 150 151 155 161 163 165 166 168 170 170 171

173 174 175 17S 180

1&2

Ma

gn

e­

sium

, to

tal

(mg

/L)

27 23 16 12 7

21 6 26 30 19 24 19 8 4 22

IS 22 30 32 25

26 40 40 36

20

0

53 81

80 5

0

22 IR 14 9

22

20

So

diu

m,

tota

l (m

g/L

)

12 6

24 9 II 36

13 2 37 40 24 86 48 42 18 14 78 28 19

17 !O

14 39

29 100

14 44 44 22 19

12 II 21 5

58

Po

tas­siu

m,

tota

l (m

g/L

)

2 4 5 4 3 7 2 2 5 4 6 9 4 4 I 2 J 4 4

13 2 5 6 3

<I

<I 3 3

Alka

linity

(mg

lL as

He

03 )

150 2

84

238

223 133 232

82

33

9

300 240 186 U

\8

177 148 216

226 241 300 272 200

246 250 340

397

140 311 300 300

329

319

270

296 174

196 243

Su

lfate

, to

tal (m

g/L) 13250; 1b500

51 29 77 27 36 79

30

36 120 110

51)

120 100 S5 36

22 190 180

18

38 120 70

170 160 540 110 170 170 71 41 54 4

17 17 62

Ch

lorid

e,

tota

l (m

g/L) 1a250

18 4

15 24 3

18 6 3

18 40 18

100 15 17 12 6 54 3

6

5 5

92 20 17 12

1.100

16 ISO

150 29 42 (i

3 II <)

18

Flu

orid

e

(mg

/L)

1e4

.19

.34

.29

<.10

.16 .72

.30

.28

.81

.60 .31 .45 .18

.57

.31

.32

.47 .20 .4

\ .(i0

.49

.20

.10 .19 .20

.20

.20

.20 .12 .37

.30 .32 ,)3

.19 .51

Nitra

te,

on

site

(mg

/L

as N)

3 2 <

.5

I 6 4 I J 2 2 I 3 2 ) 2

16 7 2 I 2

Nitrate p

lus

nitrite

(m

g/L

as N)

1c10

2.9 <,05 \.4 <.05

.70 5.4 .8

2

1.8 <

.05

.33

2.2 .53 .59

1.4

2.2

.53 <

.05

2.7 1.1 1.1 1.4 1.1 2.9

,40

37

<.05

3.2 3.2

12 4.2

.56 1.9 <

.05

.70 <

.05

Arse

nic,

tola

l reco

verab

le (llg /L

) 1cSO

4 <

2

<2 <2 <2 <

2

12 <

2

20

<5

<2

<2

4 8 <

2

<2 <2 <5 <2 <,~ 2

<5

<S 2

<5 4

<5

<2

<2

<5 <

2 9 <

2 2

Ba

rium

. to

tal

reco

vera

ble

((.tg/L

) 1e2,O

OO

<5

00

<500

<5

00

<500

<SOO <

50

0

<500

<SOO

<500

Table 5.

Pbysicnl properties and IOlal m

ajor-ion and Irace-elemen

t cQnccnlr.u

iolls in unlilrered water samplc~ collected rrom

selected wells (C

onlinued)

Cadm

ium,

Chrom

ium,

Copper,

Iron, L

ead, M

anganese, M

ercury, Selenium

. Z

inc,

Well

total total

total total

total total

total total

total

number

recoverable recoverable

recoverable reeoverable

recoverable recoverable

recoverable recoverable

recoverable (11 g

il) (llg

/L)

(11 gIL

) ~g1L)

(llg/L

) (11 g

IL)

(llg/L

) (l-(g/L)

(Ilg/L) 1e5

1c100 1d1,300

a300 1d15

1a50 1c2

1eSO

135,0

00

88 <

10 <

10 <..2

430 98

<I

<10

<10

<2 flO

100 <

I <

10 <

10 <

2 30

102 <

10 <

10 <2

40 104

<I

<10

40 2

190 106

<10

240 <

2 80

112 <

I <

10 190

<5 <20

<.2 <5

113 I

<10

<10

<2 20

115 <

10 350

<2 210

123 <

I <

10 <

SO <5

<20

<.2 <

5 125

<I

<10

<10

<')

<10

130 <

I <

10 <

10 <

2 20

I3J <

I <

10 80

<2 SO

135 <

10 20

<2 220

142 <

I <

10 <

10 <

2 20

144 <

I <

10 240

<2 20

145 <

I <

10 nlO

<2

<I

<10

146 <

I <

10 <50

<5 <

20 <.2

<S

150 I

<10

10 <

2 540

151 <

I <

10 <50

<5 <20

<2

<

5 IS

S <

I <

10 <

10 <2

<10

161 <

I <

If) <50

<5

<20

<.2 <5

163 <

I <

10 <50

<S

<20 <.2

<5 165

<I

<10

50 <2

20 166

<1

<10

SO <

5 <

20 <.2

10 16R

<I

<10

<10

<2 <

10 170

<1

<10

<50

<5

58 <.2

<5 170 171

<I

<10

<10

<2 <..10

173 <

I <

10 30

<2 <10

~

174 <

I <

10 <50

<5 <

20 <

.2 <5

>

175 <

I <

10 <

10 <2

40 CCI r

178 <

10 <

10 <

2 <

10 rrl

'II ISO

<I

<10

<10

<2 120

182 <

1 <

10 2.S 10

<I

150

-T

ablr 5.

Physical propcrtic~ and major-ion and InH

:e-c!eme:nl concelllralions in unlillcred w

iller samples cull.:(;(ed from

selecled wells

(Conlinued)

~

:l:: S

pecific p

H,

. .., S

pecific pH

, W

ater C>-

Oate

Principal

conduc-onsite

Calcium

, .,

Well

Depth of w

ell conductance,

laboratory tem

perature, '"

Location num

ber A

rea sam

ple

aquifer (standard

total 0

nu

mb

er (fe&

t) o

nsite

tance, (standard

on

site !;!

collected co

de

laboratory units)

(mg/L

) 0

(liS/em

) (liS

/em)

laS.5·S

.S

units) (0C

) ..... ~

,. :l:: 186

I I N05W

21 OC13 DO 1

WM

09-05-96

420MS

LD

300

325 338

8.2 8.0

11.0 15

."

"" 187

II N05W

23CB

AA

Ol

WM

09-05-96

420SS

LP

'"

230 569

571) 7.8

n 9.5

49 ..

188 IIN

05W24D

CB

DO

I W

M

08-19-96 420S

SL

P

IS7 737

708 7.4

7.4 10.5

54 >-.,

189 II N

05W25B

CC

CO

I W

M

03-05-94 420S

PR

D

11 g 88:2

1,000 7.5

7.5 \0.0

74 '" " til

190 IIN

05W25D

BC

CO

I W

M

~O8-19-96 420S

PR

D

390 504

54~

7.6 7.7

11.5 24

" Q. 208-19-96

., 190

II N05W

25DB

CC

O I

WM

504

540 7.6

7.7 11.5

23 0 "

20 8-21-96 F

192

11 N05W~5DDBBO I

WM

420S

PR

D

220 500

530 7.4

7.4 11.5

44 ~

192 IIN

05W35D

DB

BO

I W

M

208-21-96 500

536 7,4

7.4 11.5

44 ~ h

195 12N

OJW

J I DD

BD

OI

WM

03-03-94

420SP

KN

121

1.120 1.200

7.3 7,5

11.0 110

."

196 12N

OSW

34DD

DA

O I

WM

08-20-96

420HE

LN

450

651 679

7.5 7.4

11.5 4S

::>

~ 197

12N06W

35AC

AB

OI

WM

08-20-96

211MR

VL

400

233 254

lUi

7.:2 9,0

36 ~

199 12N

06W36B

CD

DO

I W

M

08-20-96 211M

RV

L

70 219

235 6,g

7.3 7.0

)1 0 " ;:

I National P

rimary D

rinking-Water R

cgulillions arc established for conlamin~n1s w

hich. if present in drinking waler, m

ay cuus': odversc human health effeels,

Either a M

aximum

'" ~

Contam

inanl Level (M

eL) or on aC

lion levcl wilh a Irealm

enllcehniquc is specified by Ihese regulations for regulated CO

nlamlnant,.

MC

Ls are health-based and enforceable:

'" ..., propo>ed M

CL

s are nonenforceable. S

econdary Drinking-W

ater Standards arc eSlablishcd for conlam

inanls Ihal can adversely alTectthe tasle. odor, or ilppear.~nce o

f water and

"" .c rcsult in discontinualion o

r use of Ihe w

aler. T

hese regulalions speci fy Secondary M

aximum

Contalninanl L

evels (SM

CL

), which are cslhclically based and nonenforceable (U

.S.

0:0

Envirollm

ental Proteclion Agency, 19%

), (a) SM

CL

valucs ofpJ-i show the ideal range for pi-I,

(0) Proposed MeL

, (c) MC

l, (d) Action icvel.

lReplicale sam

ple.

-,l »­eo r trI

V>

w

Ta

ble

5.

We

ll n

um

be

r

186 187 188 189 190 190 192 191 195 196 197 199

Physical properties and m

ajo

r-ion

and trace-clement concenlrations in u

nfilte

red

water sam

ples colleeled from

selected wells (C

on

tinu

ed

)

Mag{1e-

Po

tas-

Su

lfate

, C

hlo

ride

, N

itrate

, N

itrate

A

rsen

ic, B

ariu

m.

So

diu

m,

Alka

linity

tola

l F

luo

ride

p

lus

tota

l to

tal

sium

, to

tal

slum

. (m

g/L

as (m

gll)

tota

l (m

g/L) o

nslle

n

itrite

reco

vera

ble

re

cove

rab

le

tota

l (m

g/LJ to

tal

HC

03

) 1a2S0;

(mg

/L)

1c4 (m

g/L

(m

g/L

as N)

(l-(g/L) (~g/L)

(mg

ll) (m

gll)

IbSOO

1a250

as N)

lc10 lcSO

1c2,O

OO

36 3

2 226

12 <

1 .12

I <.05

<2 31

17 2

286 :2

<I

.55 9

10 <2

32 50

2 349

5R 25

1.2 .47

9

76 ]J

360

180 27

.30 1.5

<5 <500

48 12

2 JO

I 33

8 .26

5 1.8

5 48

11 2

294 31

8 .29

1.8 5

27 19

3 272

51 5

.53 <.05

13 27

20 3

279 53

5 .5.~

<.05 9

58 32

1. 350

64 130

.10 17

<5 <500

58 5

328 90

9 .28

<.05 5

4 5

<I 129

18 .11

<.5 .31

<2 6

4 I

121 14

<1 .11

I .18

<2

Table 5,

Physical properties and tolal m

ajo

r-ion

and trac.:-elcmenl concentrations in u

nliltcre

d w

ater samples co

llecle

d fro

m sclected w

ells (C

on

tinu

ed

) A

x C

ad

miu

m,

Ch

rom

ium

, C

op

pe

r, Iro

n,

Lead, M

an

ga

ne

se,

Me

rcury,

Se

len

ium

, Z

inc,

'<

tota

l lo

tal

tota

l lo

tal

tota

l to

tal

tota

l to

tal

tota

l Q

,

Well

a re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

reco

vera

ble

re

cove

rab

le

0-n

um

be

r ~

(llg/l) ~glL)

(II gIL

) (lJg/L)

(II gil)

(llg/L)

(119 /l) (11 giL

) (1l9

1L) "

1cS c1

00

ld

1.300

13300

ld1

S 1aSO

1

c2

1cSO

laS.OO

D

..., ;:r ...

186 <

10 30

<2 10

x ... 187

<I

<10

<10

<2 20

<> ::0 80

'" 188

<I

20 <7

20 ;;. .,

189 <

I <

10 67

<5 <2

0

<,2 <5

., '" ~ 190

2 <

10 <

10 <

2 140

.. c.

190 <

I <

10 10

<2 160

., Q

., 192

<I

<10

190 <

2 20

~

~

'" 192

<I

<10

130 <2

20 ~

195 <

I <

10 <50

<5

<20 <.2

<5 h '"

196 <

I <

10 90

:I 540

:! ., 197

<I

<10

<10

<2

70 II>

~

" 199

<I

<10

<10

<2

<I

40 C

I

- II> ::I

~

'C!

'C!

't' -D

'"

Table 6. Chlorofluorocarbon ((FC) data for water from selected wells. 1992 and 1995

IAobn!viations' mglL milligr::uns per liter: pg/kg, picograms per kilogfllffi of sohllion: pplV. rmts r<lr trillion (volume): CI-'C·l1. Irichlorofluoromelhanc; (,FC·12, dichlorodinuoromethone: CFC-113. tnchlorotJinuoroelh~ne , Symbol: -',110 data]

DlssolII'ed Concentration In solution Calculated atmospheric partial

Apparent Well Sampllng

Time oxygen, pressure, in pptv

number date onsite pg/kg pg/kg pg/kg age

(mg/L) CFC-11 CFC-12 CFC-113 CFC-11 CFC-12 CFC-113 (years)

12 09127195 1311 3.7 165.8 112.2 )7,5 55,0 167.5 13.6 23 1320 108.2 \ 14.2 18.9 55.8 170.5 14.7

21 09125/95 1403 1.7 289.1 179.3 40,2 95.0 2653 30,9 2() 1441 30],9 175,5 35.1 99.l> 259.6 27.0 1502 266.0 172.3 36.6 87.5 254.9 2);,2

)0 09126195 1100 9,0 \, 130.0 \ ,091.3 441,0 371.5 1.615.7 339,1 10 \110 5,141.1 33,768.2 56, 8 1,(,90.3 49.950,0 43.7 II~O 5,230.9 31.809.2 48.4 1,7 19.8 47,052,2 37.2

32 09/27/95 1005 ,1 ,7 26.3 0,0 .2 39.6 0.0 33 10\4 .7 26.7 0.0 .2 40.2 0.0 IDIR 1.4 29.7 0.0 .5 44.8 0.0

46 09125/95 1029 4.7 lion 1,045.0 51.7 192,{) 1.503.R 3R.7 12 1034 (,18 ,0 1.136.5 52,1 197.7 1.635.4 .39.0

55 09.122195 1509 8.7 4.716,8 393.4 65.4 \.508.7 566,1 48,9 10 1513 4.707,3 376,1 63.4 \,505.6 541.3 47.5 1517 4,712.0 379.5 67.9 1.507.1 546.2 50,8

(i0 0<)115192 1000 312.9 167.1 2),7 81.7 200.1 31.1 10 1010 297.3 150.9 3.1.6 77,6 190 .. 1 44,1 1020 323.3 172,5 22,7 84.4 208.6 29,8 1030 293.7 155.6 40.4 76.7 186) 53.0 1035 328.5 178.3 20.8 85.7 213.5 27.3

61 0'1128/95 1532 4.5 499.2 293.9 K9 .5 158,2 419.0 66.4 1O 1532 500.2 301.8 85.4 15R.5 430.3 63.3 1537 518.7 32.\.7 77.8 164.4 460.9 57.7

64 09128i95 1431 7,6 349.5 170.5 33.0 110.8 243.1 24.5 20 14.38 352.2 165 ,0 27.8 111 ,(' 235.2 20.6 1440 35),9 164,8 32 .5 112.1 235.0 24 , I

9.1 09126 /95 1350 453.1 11J.4 7.4 151.7 170.1, 5,R 23 1421 464,7 112,7 5,2 155.6 169.H 4,1

112 09121/95 U5) 6,0 1.495.9 493.7 98,8 500.9 743.R 77.4 R 1417 2,024.3 563.1 113 ,0 677,9 848.4 81;.5 1422 720.2 2963 461.7 241.2 446.4 361.6

113 09120/95 1056 23.9 12.3 7.5 7,5 .31.5 5.5 37 1105 23.9 24.7 5.9 7,5 :15.0 4.4

119 09120195 1232 9,0 52.4 46.1 3.0 16,6 65.7 2.2 .10 12.16 54.0 44.7 ft .7 17. 1 63.7 $,0 1241 54.0 44.9 3.8 17.2 64 ,0 2.8 1246 56.2 49.K 4.6 17,R 71.0 .3.4

151 09120195 1427 R.8 864.2 357,7 2R2.fJ 273,9 510,0 209,5 :20 1432 356.7 \97 ,0 48.7 113.1 2RO.9 ~6.1

161 09122195 1106 4,4 23.1 l7,{i 0.0 7.3 25,2 0,0 JH 1110 25,0 16,9 0 ,0 7.9 24 .0 0,0 1115 25.4 16.4 0.0 8.0 2.3.4 0,0

TABLE 6 liS

Table 6. Chlorofluorocarbon (CFC) data for water from selected wells, 1992 and 1995 (Continued)

Dissolved Concentration in solution Calculated atmospheric partial

Apparent Well Sampling

Time oxygen, pressure. In pptv

number date onslle age

pg/kg pglkg pg/kg (years) (mg/L) CFC·11 CFC-12 CFC-113

CFC-11 CFC-12 CFC-113

173 09/28/95 1113 7. 2 107.5 68.3 11.1 34 .1 97 ,) 8,2 ~7

1122 IOll .g 66.5 11.0 34 .5 94.8 8,2 II '27 105.8 69.5 9 .1 33.5 99. 1 6.7

175 09128/95 1254 6.7 321.0 141.7 29,2 101.7 202.1 21.6 23 1301 245.7 87.9 10.0 77.9 125.3 7.4 1320 252.8 115.4 12.7 ~O . I 121 .8 9A

I~O 09/21/95 115~ 5.0 68.6 37.2 10.5 22.2 54.0 8.0 31 1207 67.9 :n.5 2.0 21.9 54.5 U 1211 70.6 35.9 4.3 22.8 52.2 3.2

192 09/25/95 1241 . 1 .0 7.8 0.0 ,2 11.6 0.0 42 1252 .8 8.6 0 .0 3 12 .7 0 ,0

199 09/20/95 155 1 8.3 788.3 357.5 96.7 247 ,6 505.1 71.0 6 1602 765.1 353.2 89.9 240.3 499.1 66.0

116 Hydrology ofllle Helena Area Bedrock, WeSt-Central Monlllna. 1993-98

Table 7. Ch londe and nitrate concentrations and ratios of nitrogen isotopes and oxygen isotopes in waler from selected wells

IAnalyses by Intennollntain Laboralones. Energy Laboratories. and U.S. Geological Survey National Water Quality LaOOrdtory. Abhrcviations: mgll.. . milligrams per liter: pennil. per thousand. Symbols: <'. less than minimum reporting level: >. greater Ihan: --, not appliclIble)

Nltrogen- Oxygen-Nitrate 151 18/

Chloride, plus nitrogen- oxygen- Primary source

Well Date total nitrite, 14 stable 16 stable

Well site description of nitrate, inferred

number (mg/L)

total isotope isotope from chemical and (mg/L as ratio in ratio In physical data

N) nitrate nitrate (permil) (permil)

46 05-04-94 17) 24 Within established neighborhood in Human wasle. 11-08·96 16 Helena eil)' limits. May be old (greater 05-13-97 18 8.98 -3.99 Ihall 20 years) . unused septic systems; 12-18-97 18 unlikely thilt they are still leaking.

60 05-31-90 1.5 Within actively used horse corral and Either organic nitrogen 05-14-93 2.0 near septic systems. Residentia[ devel- from soiL or a combi-03-03-94 23 2.1 opment nearby. nation of sources. 11-07-96 2.2 05-12-97 2.6 6.13 1.23 12-16-97 2.5

87 08-13-96 \44 6.4 Within established neighborhood in Human waste. 11-08·96 6.4 Helena eil)' limits. Sewer [inc located 05-1 J-97 5.2 9.32 -2.68 within 10 feet orwelJ; old (greater than [2-18-97 6.9 20 years), unused seplic systems

located at a fanher distance.

106 08-13-96 [8 5.4 Near edge of i.nfrequently used cattle Either fcrt i [izer or a 11-08-96 2.6 pasture. One septic system within 500 combination of 05-13-97 1.2 633 3.48 feet. sources. 12-18-97 2.4

163 03-05-94 17 2.9 WithiJl established (about 20 years old) Either organic nitrogen 11 -07-96 3.2 subdivision with septic systems on 1-2 from soil or a combina-05-13-97 2.6 6.39 -3.75 acre parcels. tion of sources. 12-16-97 3.0

173 08-21-96 \42 4.2 Near top of mountain; Ont: septic sys- E ilher organ ie uitrogen I ) -07-96 4.1 tem within 500 feec. from soil or a combina-05-12-97 2.7 7.91 -1.56 tion of sources. indud-12-16-97 2.5 ing human or animal

waste.

180 08-19-96 9 .70 Ncar forested and secluded area; one Atmospheric deposi-11-07-96 .70 septic system within 1,000 feet. lion. 05-13-97 .70 3. [2 3.36 12-16-97 .70

187 09-05-96 <1 10 Near heavily grazed. horse pastuJC in Eilher organic nitrogen 11-07-96 8.6 drainage; one seplic system wilhin 500 from soi[ or combina-05-13-97 i .2 6.05 -1.90 feet. tion of sources. 12-16-97 7.3

195 03-03-94 1130 [ 7 Near top of hill: two septic systems Human or animal 11-08-90 14 loealed within 1.000 feCI; large horse waste. 05-13-97 16 10.04 -6.09 pasture with three horses within 20 feel. 01-15-98 16

I Because humans conswne and dispose of sail (sodium chloride l. Inrge concentration$ (>40 mglL) of chloride may indicate a human source,

TABLE 7 117

Table 8. Volatile organic compounds, EPA Maximum Contaminant Levels, minimum reporting level, and concentrations of volatile organic compounds in water samples collected from selected wells

[Analyses by Energy Labo .. tones, Billings. Monl. Vnlatile: organic compounds analy%cd lIsing EPA Method 524.2. Abbreviation~: EPA. U.S. Environmental Prot~tion Agency: MCL. Maximum Conlllminanl Level: NA. not applicable to (his mctllOd; ND. not detected above minimum reponing level; Nit no currently regulated concenrr:llion: llg/L. micrograms per liter. S>'ffibol: '-, nOl applicnbk\

Volatile organic compound EPAMCL

(!Jg/L)

REGULATED VOLATILE ORGANIC COMPOUNDS

benzene 5

carbon tetrachloride 5

ell lorobenzene 100

1,2-diehlorobenzene 600

1,4-d ichlorobenzene 75

1.2-dichloroethane 5

I.I-d ichloroethene 7

cis-I,2-dichloroelhenc 70

Iram-I.2-dichloroethenc 100

1.2-dichloropropane 5

ctJlylbenzene 700

melhylene chloride 5

slyrene 100

lellOehloroethene 5

toluene 1,000

1.2.4-lrichlorobenzene 70

1.1 .I-trich loroelhane 200

l,I.2-lrichloroetJlane 5

uichlorocthene 5

vinyl chloride 2 m+p-xylenes

o-xylene

lolal xyknes 10.000

Minimum reporting level

(!Jg/L)

0.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

.50

REGULATED VOLATILE ORGANIC COMPOUNDS: TRlHALOMETHANES

bromodichloromethane TOlalof .50

bromofonn all four .50 chlorodibromomclhane conlpounds .50

chloroform is 100 .50

OTHER EPA LISTED VOLATILE ORGAN[C COMPOUNDS

bromobenzenc NR .50 bromochloromethane NR .50

bromomethane NR .50

n-butylbenzene NR .50

scc-butylbenzene NR .50

tcn-butylbenzcne NR .50

chloroelhane NR .50

chloromelbane NR .50

2-chlorotoluene NR .50

118 Hydrology of the Helena Area Bedrock, West-Central Montana. 1993-98

Concentra­tionln

selected wefls1

(!Jg/L.)

ND NO ND ND ND ND ND ND NO NO NO NO NO ND ND NO ND ND NO NO NO NO NO

ND NO ND N1)

NO ND NO ND ND ND NO NO NO

Table 8. Volatile organic compounds, EPA Maximum Contaminant levels, minimum repor! ing level, and concentrations of volatile organic compounds in water samples collected from selected wells (Continued)

Volatile organic compound EPA Mel

(llgll)

Minimum reporting level

(llgll)

Concentra­tion in

selected wells1

(flgll)

OTHER EPA LISTED VOLATILE ORGANIC CO!~'IPOUNnS-Conllnlled

4-chlorotoluene

1.2-dibromo-3-chloropropane

1.2-dibromoethane

dibromomethane

1.3-dichlorobeTl7.ene

d ich lorodi tluoromethane

I.I-dichloroelhane

I,l-dichloropropene

1.3-dichloropropBne

cis-IJ-dichloropropene

!ralls-l J-dichloropropcne

2.2-dichloropropane

fluorotrichloromethane

hexachlorobuladienc

isopropylbenzcne p-isopropyl\ol uene

naphthalene

n-propylbt:nzene

1.I.l.2-tetrachloroethane

1.1.2.2-letrachloroethanc

1,2,3-trichlorobcnzene

1.2,3-lIichloropropane

1,2,4-trimelhylbenzene

1.3,5-trimelhylbenzcne

NR .50

NA .50

NA .5{)

NR .50

NR .50

NR .50 NR .50

NR .50

NR .50 NR .50

NR .50

NR .50 NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NR .50

NO

NO NO NO NO NO NO ND

ND

ND

NO NO NO NO NO ND ND

ND

NO NO NO ND ND NO

t Wells sampled and corresponding date: well 21, 08-0f;-96; well 39,08-13-96; well 61. 08-21-%: we)) 87. 08-1.3-96 (replicate sample taken. analysis detected no compounds); well 98. 08-21-96: well 104.08-13-96: well 145. 0!!-20-96: well 165.08-20-96 (replicate sample taken. analysis detected 110 compounds): well 186.09-05-96 (replicate sample !!Iken, ~nal­y~is detected no compounds): well 199, 08-20-96.

TABLE 8 119

-:r U.S. GOVERN"f~T PRINDNG orrrCE: 1000 - 67].699 / 4~OOO Region "0. 8