WATER-SUPPLY ASSESSMENT OF THE LARAMIE-FOX HILLS AQUIFER IN PARTS OF

ADAMS, BOULDER, JEFFERSON, AND WELD COUNTIES, COLORADO

By Paul A. Schneider, Jr.

U.S. GEOLOGICAL SURVEY

WATER-RESOURCES INVESTIGATIONS

OPEN-FILE REPORT 80-32?

Prepared for the

U.S. Bureau of Reclamation

Lakewood, Colorado

1980

\

UNITED STATES DEPARTMENT OF THE INTERIOR

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

For additional information write to:

Colorado District Chief U.S. Geological Survey, MS 415 Box 25046, Denver Federal Center Lakewood, CO 80225

For sale by:

Open-File Services SectionBranch of DistributionU.S. Geological Survey, MS 306Box 25^25, Denver Federal CenterDenver, CO 80225(303) 23^-5888

CONTENTS

Metric conversions——---—-—-• Abstract ———————————————— • Introduction- — —— ———————— • Acknowledgments--—------——-.Laramie-Fox Hills aquifer------

Potentiometric surface----Th ickness------- — — ------Storage--- — ------ —— — — •Well yields—---------—-•Chemical quality of water-

Additional data requirements--- Summary----------—-——-—--•References ——— ————— — — —— •

Page IV

1 3 3 3 k5666

151617

Plate 1

Figure 1, 2.

ILLUSTRATIONS

Map showing potentiometric surface of Laramie-Fox Hills aquifer based on water-level measurements made during 1957~61 in parts of Adams, Boulder, Jefferson, and Weld Counties, Colorado— In

Map showing potentiometric surface of Laramie-Fox Hills aquifer based on water-level measurements made during 197^"78 in parts of Adams, Boulder, Jefferson, and Weld Counties, Colorado-- In

Map showing approximate aggregate sand thickness of Laramie-Fox Hills aquifer in parts of Adams, Boulder, Jefferson, and V/eld Counties, Colorado— ———— --- —— —————— — —— ——————— — In

Map showing reported well yields from the Laramie-Fox Hills aquifer in parts of Adams, Boulder, Jefferson, and Weld Counties, Colorado- —— - — — ---- — - —— — -- — -- — — -- — — — -- | n

Map showing chemical quality of water from the Laramie-Fox Hills aquifer in parts of Adams, Boulder, Jefferson, and Weld Counties, Colorado— — - — ------- — - — ---- — — -- — -- — — ---- j n

Map showing specific conductance of water from the Laramie-Fox Hills aquifer in parts of Adams, Boulder, Jefferson, and Weld Counties, Colorado--—-----——-—--------—-----—------__ j n

Page

pocket

pocket

pocket

pocket

pocket

pocket

Map showing location of study area----—---—----—--———--•Graph showing relation between well yield and aggregate sand

thickness- — - — — ------------------ — -------- —— --- — — -—.

II I

\

TABLES

PageTable 1. Construction details of selected wells shown on plate 3——————- 7

2. Summary of chemical analyses ——— ——————— ———— —— —— — — — — - 12

METRIC CONVERSIONS

Inch-pound units used in this report may be converted to metric units by using the following conversion factors:

Multiply inch-pound unit By To obtain metric unit

foot 0.30^8 metermile 1.609 kilometerfoot per mile 0.189^ meter per kilometeracre 0.^0^7 hectareacre-foot 0.001233 cubic hectometergallon per minute 0.06309 liter per second

NATIONAL GEODETIC VERTICAL DATUM OF 1929 (NGVD of 1929)

A geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called "Sea Level Datum of 1929" or "mean sea level" in reports. Although the datum was derived from the average sea level over a period of many years at 26 tide stations along the Atlantic, Gulf of Mexico, and Pacific Coasts, it does not necessarily represent local mean sea level at any particular place.

IV

WATER-SUPPLY ASSESSMENT OF THE LARAMIE-FOX HILLS AQUIFER IN PARTS OF

ADAMS, BOULDER, JEFFERSON, AND WELD COUNTIES, COLORADO

By Paul A. Schneider, Jr.

ABSTRACT

Ground water in the Laramie-Fox Hills aquifer is a potential source of supplemental municipal water supplies for the communities of Erie, Lafayette, Louisville, and Superior. The present water supplies for these communities are not always adequate to meet current demands. At the request of the U.S. Bureau of Reclamation, which is investigating and evaluating alternative sources of water for the communities, the U.S. Geological Survey made a water-supply assessment of the Laramie-Fox Hills aquifer.

Recharge to the aquifer is mostly in the western and southwestern parts of the study area. Ground-water movement is generally from the southwest to north­ east. Ground-water discharge in the study area is primarily by pumping wells. Since 1961, this pumping has caused water-level declines of about 250 to 300 feet from Broomfield to east of Erie, Colo. Generally, water levels in other parts of the area have remained the same.

The aggregate sand and aquifer thickness determined from well logs ranges from k2 to 360 feet and the mean thickness is 229 feet. The volume of ground water in storage in the study area is about 5 million acre-feet. Reported yields from 93 wells ranged from 1 to 90 gallons per minute and averaged 22 gallons per minute. Well yields tended to be larger in the areas where aggregate sand thick­ ness is the greatest.

The water changes from a sodium calcium bicarbonate type to a sodium calcium sulfate type as it moves through the aquifer away from the recharge areas. The maximum limit established by the U.S. Environmental Protection Agency for nitrite plus nitrate in public-water supplies was exceeded in water from three wells, the maximum limit for fluoride was exceeded in water from two wells, and the maximum limit for selenium was exceeded in water from three wells.

40olr-

Base from U.S. Geological SurveyState base map, 1969

0 5 I_______L

10 I

15 MILES I

0 5 10 15 KILOMETERS

Figure 1.--Location of study area.

INTRODUCTION

The towns of Erie, Lafayette, Louisville, and Superior, 15 to 20 miles northwest of Denver, Colo., are in a rapidly expanding urban area called the Front Range Urban Corridor. Population increases have caused an increased need for water. The present water supplies for these communities are not always adequate to meet current demands, and restrictions on water use have been imposed. In March 1978, at the request of the U.S. Bureau of Reclamation, which is investigat­ ing and evaluating alternate sources of water for the communities, the U.S. Geological Survey began a study to determine the quantity and quality of water in the Laramie-Fox Hills aquifer so that this source could be evaluated as a possible supplemental supply of municipal water.

The present study was limited to the Laramie-Fox Hills aquifer within an area defined by the U.S. Geological Survey topographic maps for the Erie, Lafayette, Louisville, and Niwot 7i~minute quadrangles (fig. 1). The volume of water in and the yield of water from abandoned coal mines in the area are not included in this study because the mines generally are in one or more stratigraphic horizons above the top of the Laramie-Fox Hills aquifer. Cochran and Robinson (1973) reported, "Miners and the mining company's safety inspector report the mine (Crown) was considerably wetter during the irrigation season than during the rest of the year. They also stated that the mine intercepted a well that flowed at the surface. The casing was broken during mining and the water from the underlying sandstone caused flooding in the mine until the hole was plugged * * »."

Well records from the Colorado State Engineer's Office and data from files and published reports of the U.S. Geological Survey were used to construct the maps showing the potentiometric surfaces and the maps showing aquifer thickness and reported well yields. Reported data were not always verified. Unpublished water-quality data collected in the area were evaluated and incorporated into the maps showing chemical quality and specific conductance of water. These data also were used to compile the table summarizing the chemical quality of the water.

ACKNOWLEDGMENTS

Many people assisted in the collection and interpretation of data for this study. Their help is greatly appreciated. The landowners, who permitted access to the wells for measurements and water samples, were especially cooperative. Ms. Susan Schwartz, a summer employee hired through the Minority Participation in Earth Sciences program and a student at State University of New York at Binghamton, is due recognition for her assistance in tabulating, plotting, and analyzing the data used in this report.

LARAMIE-FOX HILLS AQUIFER

The Laramie-Fox Hills aquifer consists of the major sandstone beds at the base of the Laramie Formation and the underlying Fox Hills Sandstone of Late Cretaceous age. The aquifer is underlain by the Upper Cretaceous Pierre Shale,

which includes the upper transition member. The thickness of the Pierre Shale is about 9,000 feet (Colton, 1978). The Pierre Shale is the underlying confining bed throughout the study area. Shales in the Laramie Formation above the aquifer form the upper confining bed in most of the study area. The outcrops of the aquifer are generally west of Louisville (Colton and Anderson, 1977; Machette, 1977; Spencer, 1961; and Trimble, 1975).

The extent and locations of the faults existing in the aquifer system have been discussed by Spencer (1961), Colton and Lowrie (1973), Trimble (1975), Colton and Anderson (1977), and Colton (1978).

Water-table conditions exist primarily in the outcrop-subcrop area along the western limit of the aquifer. Artesian conditions exist primarily throughout the rest of the study area, even where the aquifer is faulted to the surface, as evi­ denced by comparisons between water-level measurements made by the U.S. Geological Survey, and the top of the aquifer, as determined from drillers' logs.

Potentiometric Surface

The Laramie-Fox Hills aquifer in most of the study area is a confined aquifer, which means that the water in the aquifer is under pressure and will rise above the top of the aquifer in wells completed in the aquifer. In a few areas, the pressure is sufficient to cause the water in wells to rise above the land sur­ face where the wells will flow if not shut in. The imaginary surface connecting water levels in wells tapping only the confined Laramie-Fox Hills aquifer defines the potentiometric surface.

The rate and direction of movement of water through an aquifer is seldom uniform because of changes in permeability, saturated thickness, and recharge- discharge relationships. Recharge and discharge to the aquifer affect the shape of the potentiometric surface more than any other factor. The direction of flow is generally perpendicular to the potentiometric contours and water moves from areas of recharge downgradient to points of discharge.

The potentiometric surface (pis. 1,2) is highest in the southwestern part of the study area and lowest in the eastern and northeastern parts, indicating that ground-water movement, in general, is from the southwest to the northeast. The primary areas of recharge are in the western and southwestern parts of the area. The potentiometric surface under Rocky Flats has a gradient as steep as 200 feet per mile for about 3 miles east of the outcrop-subcrop area. The gradient and direction of ground-water movement indicate that the Laramie-Fox Hills aquifer is being recharged along the upturned edge of the aquifer as it subcrops beneath the saturated alluvium under Rocky Flats. Significant recharge also occurs on Davidson and Lake Mesas as a result of leakage from irrigation canals and from reservoirs cut into the underlying sandstones. Limited recharge occurs where saturated alluvium in stream valleys overlie the subcrop of the aquifer. Discharge from the aquifer is by pumpage and possibly by upward leakage into Boulder Creek downstream from the confluence with Coal Creek. Some leakage by gravity occurs from the aquifer to Boulder Creek valley upstream of the confluence of Coal Creek.

The mound in the potentiometric surface east of Lafayette is not the result of local recharge, but may be a remnant of the potentiometric surface that existed prior to extensive ground-water development in the area. The northeast-trending faults in the area may act as barriers to flow and may have minimized the effects of drawdown in this area. Another possible explanation for this mound is vertical leakage from overlying water-bearing formations along fault planes or directly down the well bore of corroded or improperly constructed wells.

Interpretations of the water-level data indicate that the general configura­ tion of the potentiometric surface has persisted for more than 20 years (pis. 1, 2), but increased pumping since 1961 has slightly modified the configuration. As pumping increased, isolated cones of depression developed rapidly around the pumping centers. In the past, these cones remained relatively isolated because movement of water through the aquifer was impeded in some areas by impermeable fault zones. However, as pumpage continues to increase and the drawdown cones continue to expand, the shape of the potentiometric surface will be greatly modi­ fied in the next 20 years. This change in shape will be disclosed by a greater depth to the potentiometric surface below land surface, thereby increasing pumping lifts and costs. Increased pumpage also will decrease discharge to Boulder Creek valley. The depth to the potentiometric surface may be determined at any location by subtracting the altitude of the potentiometric surface shown on plate 2 from the altitude of the land surface.

Pumping has lowered the hydraulic head and decreased the altitude of the potentiometric surface by about 250 feet at Broomfield, Colo. The area of decline has become elongated and presently (1978) extends to near Erie, 8 miles to the northeast. The greatest declines in the potentiometric surface—about 300 feet-­ have occurred in this part of the area since the early 1960's. Outside of this area, little change in the potentiometric surface has occurred during the last 20 years.

Thickness

The composition of the Laramie-Fox Hills aquifer in the area is mostly sand. Therefore, the thickness of the aquifer shown on plate 3 and the aggregate sand thickness are virtually the same. This thickness was determined by examination of drillers' lithologic logs and electrical-resistivity logs for wells in the area. In parts of the study area, wells are constructed so close together that they cannot be plotted as individual data points on the map. Where these circumstances occurred, values were averaged and shown as one data point. Based on data from well logs, the thickness of the Laramie-Fox Hills aquifer ranges from k2 to 360 feet and the mean thickness is 229 feet. Reported thickness exceeds the values on those data points shown on plate 3 which are followed by a plus sign, because these wells are bottomed in sand.

No attempt was made to infer the effect of faulting on the thickness lines. On the downthrown side of some faults, thickening of the aquifer indicates movement contemporaneously with deposition (Louis Gaz, oral commun., 1978). This mechanism may be the cause of the greater than expected thickness of the aquifer in areas adjacent to faults.

Storage

The volume of water stored in the aquifer was calculated using aggregate sand thickness of the aquifer, specific yield, and area of the aquifer within the study area. The mean value of 229 feet was used for the aggregate sand thickness. Specific yield is the ratio of the volume of water which can be drained by gravity to the volume of rock drained, and is equal to porosity minus specific retention. The value for specific yield of 0.22, used in the calculation of volume of water in storage, was estimated using existing data from core samples previously analyzed by the U.S. Bureau of Reclamation and by the U.S. Geological Survey (McConaghy and others, 1964). Many of the samples were cored from outcrops, although some samples were obtained during well drilling. The area of the aquifer within the study area is 114,000 acres. Using these values, about 5 million acre- feet of water is stored in the Laramie-Fox Hills aquifer within the study area. Using the probable extremes of the individual variables, the limits of this esti­ mate are a minimum of 2 million acre-feet and a maximum of 11 million acre-feet.

Well Yields

The yields of 93 wells completed in the Laramie-Fox Hills aquifer were obtained from data reported by well drillers to the Colorado State Engineer's Office and from data in reports publijhed by the U.S. Geological Survey (Jenkins, 1961; McConaghy and others, 1964). The reported well yields shown on plate 4 range from 1 to 90 gallons per minute and average 22 gallons per minute.

The yield of a well depends on the pump capacity, well construction (table 1), and the hydrogeologic characteristics and conditions of the aquifer. One of the characteristics that contributes to the potential yield of a well is the aggregate sand thickness. The relationship between reported well yield and aggregate sand thickness determined by data from 35 wells in the study area (fig. 2) shows that as sand thickness increases the yield increases. The band shown in figure 2 represents plus or minus one standard error of estimate. The reported well yields may not represent the maximum yields that could be obtained from the aquifer principally because most of the wells were constructed for domestic use. Properly constructed wells equipped with larger capacity pumps may yield several tim^s the amount of water normally obtained from domestic wells.

Chemical Quality of Water

The location of wells from which water samples were collected for chemical analysis or determination of specific conductance by the U.S. Geological Survey during 1975-78 (D. C. Hall, written commun., 1978) are shown on plates 5 and 6. The chemical analyses are listed in table 2. The water varied from a sodium calcium bicarbonate type to a sodium calcium sulfate type. The concentration of dissolved solids ranged from 171 to 2,910 milligrams per liter. Hardness ranged from 8 to 2,000 milligrams per liter.

Tabl

e 1.—Co

nstr

ucti

on d

etails of

sel

ecte

d we

lls

show

n on plate 3

Well

number

001

002

003

005

006

008

009

010

015

016

017

018

020

021

022

023

02 4

025

026

027

Total

wel

1 de

pth

(ft)

200

100

*595 310

300

308

154

^00

500

650

Hoo

1390

!200 300 174 875

500

600

475

^0

Casi

ng

diam

eter

(in.)

6-5/

8 4-

1/2

6 4 6 6 6-5/

8 4 6-

5/8

6 4-1/

2

6 6-5/

8 4-

1/2

6 5-5/

8 4-

3/8

6 6-5/

86 5 6 5 4-

1/2

6-5/

8

6 10

Casi

ng

depth

(ft)

0-22

10-35

0-23

23-35

0-35

0

0-12

4

0-21

10

-60

0-72

0-15

4

0-49

0

0-80

0-21

6 340-370

412-

570

612-

660

0-17

2

0-18

5 18

5-39

00-

21

0-70

0-18

0-56

9

0-40

40-1

10

110-

305

0-30

0

0-26

3

0-11

0

Perforated

casi

ng

inte

rval

(f

t)

35-2

00

35-100

2350-595

2124

-310

60-300

272-

308

490-640

640-700

80-300

216-340

370-412

570-612

2172

-400

221-200

270-300

18-174

2569-875

2305-500

2300

-600

2263

-475

110-

400

Perf

orat

ed

casi

ng

diam

eter

(f

t)

4-1/

2

4 4 4-1/

24 6 4-

1/2

4 8

Repo

rted

yi

eld

(gal

/min

)

7 10 20 10 6 20 3 8 40 35 30 15 15 60 4 25 15 30 15 79

Repo

rted

le

vel

,(f

t) 35 12

220 70 80 45 50 300 20 31 0 60 30 90 18 80 150 35 50 54

water

stat

ic(d

ate)

1-73

2-72

6-64

9-71

10-7

2

1-73

11-6

04-

65

6-66

2-77

8-64

9-72

7-71

4-67

3-72

3-66

8-74

6-65

7-71

4-66

Repo

rted

wa

ter

level

, pumping

(ft) 175

100

345

240

300

240

145

600

200

180

210

310

100

120

174

181

270

170

160

254

(dat

e)

1-73

2-72

6-64

9-71

10-72

1-73

11-60

4-65

6-66

2-77

8-64

9-72

7-71

4-67

3-72

3-66

8-74

6-65

7-71

4-66

Water

use

dome

stic

stoc

k

dome

stic

dome

stic

dome

stic

dome

stic

domestic

domestic

unused

stoc

k

i rri

gati

on

domestic

stoc

k

dome

stic

publ ic

dome

stic

sewe

r plant

dome

stic

commercial

Date of

con­

struction

1-73

2-72

6-64

8-71

10-72

1-73

11-6

04-65

6-66

2-77

8-64

9-72

7-71

4-67

3-72

3-66

8-74

6-65

7-71

3-66

Table 1.—Co

nstr

ucti

on d

etails of selected we

lls

show

n on p

late

3—Co

ntin

ued

co

Well

number

028

029

030

032

033

036

037

038

039

043

044

045

047

048

049

050

051

064

068

071

Total

wel

1 de

pth

(ft)

*365 200

780

3855

^00

520

^00

535

*487 655

*660

^00

^00

615

1,103

825

1,02

2

^00

650

239

832

Casing

d ia

mete

r (i

n.)

8-5/

8

6 4-1/

2

6 4-1/

2

10 7-7/

8 5-

5/8

6 6 6 8-5/

8

6 6 4-1/

2

5 6-5/

8 4-

1/2

4-1/

2

6 10 7-3/

45-

5/8

4 8 6-5/

8

Casi

ng

dept

h (ft)

0-76

0-35

0-62

5

0-31

50-

275

0-12

12-607

0-29

90-

300

0-35

1

0-38

0

0-40

5

0-21

21-3

59

0-33

4

0-79

5 795-819

0-62

2

0-10

1 10

1-76

0

0-52

6

0-31

31

-650

0-73

55-1

930-

23

23-700

Perf

orat

ed

Perforated

casing

casing

interval

diameter

(ft)

(f

t)27

6-36

5

235-

200

625-

750

6

2315

-600

2275

-520

2607

-800

2299

-535

2300-487

2351-655

380-660

6-5/

82405

-600

359-700

4-1/

2

2334-6l5

819-1,103

4-1/

2

2622

-825

760-1,022

2526

-800

400-

650

193-239

4

700-

832

6-5/

8

Repo

rted

yield

(gal/min)

37-5

0

2 13 25 8 15 25 25 25 20 15 15 12 65 12 16 25 20 30 15

Repo

rted

level

,(f

t)

160 18 325 50 175 22 150

100

180

212

180

250

150

191

200

273

220

150

181

260

wate

r st

atic

(date)

4-63

5-67

11-5

8

5-64

1-61

3-59

6-65

4-64

11-6

82-

74

4-71

6-67

5-63

8-66

3-68

6-58

7-65

9-58

5-60

10-5

8

Repo

rted

wa

ter

level

, pumping

(ft) 160

200

355

140

375

300

200

250

185

360

480

450

500

500

300

335

325

200

300

(dat

e)

4-63

5-67

11-5

8

5-64

1-61

3-59

6-65

4-64

11-6

82-

74

4-71

6-67

5-63

3-68

6-58

7-65

9-58

5-60

10-5

8

Wate

r use

municipal

domestic

domestic

dome

stic

domes t ic

domestic

domestic

dome

stic

dome

stic

domestic

domestic

domestic

commercial

domestic

dome

stic

dome

stic

dome

stic

Date

of

con­

struct ion

4-63

5-67

11-5

8

5-64

1-61

3-59

6-65

4-64

11-6

82-

74

4-71

6-67

5-63

7-66

3-68

6-58

7-65

9-58

5-60

10-5

8

Table 1.—Co

nstr

ucti

on d

etai

ls of sel

ecte

d we

lls

show

n on p

late 3—Co

ntin

ued

Total

Well

well

number

dept

h (f

t)

073

074

076

081

082

085

086

091

092

093

094

095

096

098

099

102

105

106

107

108

109

*575 647

^80

400

165

*255 250

1383

^00

*427

!210 200

205

282

458

580

*325 254

1,09

91516 150

Cas ing

d ia

mete

r (in.)

8 4-1/

2

6 4-1/

2

6 6 4-1/

2

4-1/2

7-1/2

4-1/2

8-5/

8

6 6 4 6 4 6 6-5/

8

8 4-1/

2

4-1/

2

7-7/8

6-5/8

7 6 6

Casing

dept

h (f

t)

0-22

22-334

0-47

47-461

0-14

2

0-25

20

-260

0-60

0-51

0-15

10-

76

0-35

0-28

28

-210

0-20

10-60

0-42

0-6Q

0-177

0-8

30-1

75

0-32

30-44

0-74

0-73

2

0-31

00-

21

Perf

orat

ed

Perforated

casi

ng

casing

interval

diameter

(ft)

(f

t)23

34-5

75

2461-647

2142

-380

2260

-400

60-160

251-

255

2151

-250

70-3

8323

5-20

0

2210-427

60-210

242-

200

60-205

177-

282

8-30

21

75-4

58

2323-580

44-3

25

74-2

54

732-

1,09

323

10-516

221-

105

4-1/

2

6-5/

8

4 6-5/

8

5-5/

8

4-1/

2

5-5/

8

4-1/

2

7

Reported

yiel

d (gal/min)

10 10 20 10 90 15 15 40 2 15 15 40 9 12 10 10 12 12 75 25 50

Reported wa

ter

level

, st

atic

(ft)

180

160

110 97 25 25 40 130 18 150 15 50 20 96 18

260

200 38 80 8

(date)

6-61

1-58

3-67

10-59

3-60

10-5

9

12-5

96-72

5-67

9-71

6-71

8-69

10-6

88-59

9-58

8-72

7-58

8-72

7-69

8-64

Reported wa

ter

leve

l , pumping

(ft) 240

220

290

193

140

225

200

250

200

200

165

150

205

212 22 450

325

445

300 80

(dat

e)

6-61

1-58

3-67

10-5

9

3-60

10-59

12-59

6-72

5-67

9-71

6-71

8-69

10-6

88-

59

9-58

8-72

7-58

3-58

7-69

8-64

Water

use

domestic

domes

t ic

domestic

domes

t ic

dome

stic

dome

stic

domestic

dome

stic

domestic

domestic

domestic

domestic

domestic

dome

stic

domestic

comm

erci

al

dome

stic

municipal

Date o

f co

n­

stru

ctio

n

6-61

1-58

3-67

10-5

9

3-60

10-59

12-59

6-72

5-67

9-71

6-71

8-69

10-6

88-59

9-58

8-72

7-58

8-72

3-58

7-69

8-64

Table 1.—Co

nstr

ucti

on d

etai

ls of

selected we

lls

shown

on p

late

3—Continued

Tota

l Well

well

number

dept

h (f

t)

110

111

112

113

115

116

117

118

119

120

121

123

124

126

127

128

129

130

133

134

135

155

755

157S

*647

1,033

*565

1665

186S

*925

1,075

1,10

0

498

614

548

709

^00

575

620

1S6Q 580

390

Casing

Casing

diameter

dept

h (in.)

(ft)

6 8-5/8

6-5/8

6 6 4-1/

2

8-5/8

5 4-1/

2

6 5-5/

8

4 6-5/

8

4-1/

2

4 6 4-1/

2

6-5/

8

6 6 4-1/

2

6-5/

8

4-1/

2

6

0-21

0-37

0 395-540

0-32

5

0-47

47-461

0-78

0

0-87

87-301

0-42

4

0-73

0

0-83

5

0-77

5

0-948

0-28

0

0-37

3

0-36

0

0-37

2

0-35

0

0-31

0

0-400

0-660

0-323

0-24

0

Perf

orat

ed

Perf

orat

ed

casing

casing

interval

diam

eter

(f

t)

(ft)

221-155

370-395

6-5/

8 540-755

2325

-575

461-

647

780-

1,03

3 6-

5/8

2301-565

2424

-665

2730

-865

835-

925

4

769-

1,07

5 4-

1/8

948-

1,10

0 4-

1/2

2280-498

2373-6l4

2360-548

372-

709

4-1/

223

50-600

310-575

62400

-625

660-

960

6-5/

823

23-5

80

2240

-390

Repo

rted

yi

eld

(gal/min)

50 40 20 10 27 10 15 10 10 38 29 15 20 10 32 15 20 10 30 10 15

Reported wa

ter

level

, st

atic

(ft) 16

360

200

160

346

180

280

220

350

190

160 85 120

200

245

250

270

317

260

140

(date)

8-64

9-56

10-64

1-58

11-6

56-72

8-68

1-58

6-71

9-65

7-58

6-62

3-71

6-62

3-64

5-70

4-68

11-6

58-72

7-61

Repo

rted

water

leve

l , pumping

(ft) 56 280

220

8AO

400

500

535

550

290

224 85 170

350

314

3^5

325

270

350

450

350

(date)

8-64

10-64

1-58

11-65

6-72

8-68

1-58

6-71

9-65

7-58

6-62

3-71

6-62

8-62

3-64

5-70

4-68

11-65

8-72

7-61

Water

use

muni

cipa

l

i rrigat ro

n

domestic

domest ic

domestic

domest ic

domestic

domestic

domest ic

domestic

domestic

domestic

domestic

dome

st ic

domestic

domestic

domest ic

dome

st ic

municipal

dome

stic

Date o

f con­

struction

8-64

9-56

10-64

1-58

11-65

6-72

8-68

1-58

6-71

9-65

7-58

6-62

3-71

6-62

8-62

3-64

5-70

4-68

11-65

8-72

7-61

Table 1.—Co

nstr

ucti

on d

etai

ls of sel

ecte

d we

lls

show

n on p

late 3 — Continued

Well

number

136

142

145

147

151

152

153

154

155

156

157

158

159

160

Total

well

dept

h (ft)

J550 93 450

610

185

175

M80

1,09

9

1,10

3480

500

1 ,2

01 545

585

Casing

d ia

mete

r (i

n.)

6-1/

2

4-1/2

4-1/2

4-1/2

6 6 6 7 5 4-1/2

6 6 8

Casing

depth

(ft)

0-300

0-20

0-322

0-41

00-

22

0-22

0-21

0-732

0-22

22-330

0-80

0-189

Perf

orat

ed

Perforated

casing

casing

interval

diam

eter

(f

t)

(ft)

2300-550

20-9

0 4-1/2

2322-450

2410

-610

22-185

4-1/2

222-175

221-180

2732-1,093

2330-480

80-300

6 30

0-50

0

2l89-545

Repo

rted

yi

eld

(gal/min)

15 1 7 15 30 10 14 75 10 40 14

Reported

leve

l ,

(ft)

110 20 225

225 6

260 20 140 20 20

wate

r stat ic

(date)

7-71

11-6

09-

617-73

7-68

8-72

5-64

6-63

6-66

5-64

Reported wa

ter

level

, pumping

(ft) 360 93 350

380 80 450

160

445

270

200

160

(dat

e)

7-71

11-6

09-61

7-73

7-68

8-72

5-64

3-58

6-63

6-66

5-64

Wate

r use

domest ic

i rr ig

at ion

domest ic

domest i c

domest i c

domestic

comm

erci

a 1

domest i c

domest i c

dome

stic

domest i c

domest ic

comme re

i a

1

Date of

con­

struction

7-71

11-6

09-61

7-73

7-68

8-72

5-64

5-58

8-66

6-63

6-66

2-57

5-64

7-54

does not

comp

lete

ly pe

netrate

aquifer.

20pe

n ho

le.

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PH

Watertemperature

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Hardness(mg/L)

Noncarbonatehardness

(mg/L)

Dissolvedcalcium (Ca)

(mg/L)

Dissolvedmagnesium (Mg)

(mg/L)

Dissolvedsodium (Na)

(mg/L)

Percentsod 5 urn

Sod i urnadsorption ratio

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Dissolvedchloride (Cl)

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Dissolvedfluoride (F)

(mg/L)

Dissolved sol ids(sum of consti tu-

ents) (mg/L)

Dissolvednitrite (N)

(mg/L)

Dissolved nitriteplus nitrate (N)

(mg/L)

Dissolved ortho-phosphorus (P)

(mg/L)

Dissolvedboron (B)

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Dissolvedmanganese (Mn)

(yg/L)

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03

0311 o o3rt3*

C Oa.

40

30

20

10

100 200 300AGGREGATE SAND THICKNESS, IN FEET

400 500

Figure 2.— Relation between well yield and aggregate sand thickness.

Interpretation of the data indicates that as the water in the aquifer moves downgradient and away from the recharge area it changes from a sodium calcium bicarbonate type to a sodium calcium sulfate type. This change in water type is a result of ion exchange as the water moves through the coal and carbonaceous clay and shale existing in the formation. The diversity of water type across the study area is controlled by the amount and type of water recharged to the aquifer, vertical leakage from overlying or underlying water-bearing formations, and resi­ dence time of the water in the formation. Other factors which may contribute to the deterioration of water quality are improper well construction and deteriora­ tion of casing, which would allow more mineralized water from other water-bearing zones to enter the wel1.

Nitrite plus nitrate concentrations in water from three wells, fluoride concentrations in water from two wells, and selenium concentrations in water from three wells exceeded the maximum limits for public-water supplies established by the U.S. Environmental Protection Agency (1976). Dissolved-solids concentrations in water from eight wells, the iron concentration in water from one well, manga­ nese concentrations in water from two wells, and sulfate concentrations in water from seven wells exceeded the recommended limits for public-water supplies established by the U.S. Environmental Protection Agency (1977). At least one constituent in water from 12 of the 1^4 wells exceeded either the maximum or recom­ mended 1imi ts.

ADDITIONAL DATA REQUIREMENTS

Examination and interpretation of the available data have indicated that there are some data deficiencies that need to be eliminated if a complete definition and understanding of the hydrologic system of the area is to be made. Additional well data, such as location, depth, water level, and yield, are needed in selected parts of the study area. Water-level data are needed particularly across the northern and southern parts of the study area to better define the potentiometric surface. Data to determine the relationship between faulting and the potentiometric surface are needed.

Aquifer tests are needed throughout the study area to refine the estimates of specific yield used in calculating the volume of water in storage. These tests and data also would aid in making better estimates of potential well yield.

Additional water-quality data would contribute to a more complete description of the water quality of the area. It also would provide a basis for a better understanding of the changes in water quality that could occur and the factors that control these changes.

15

SUMMARY

Water in the Laramie-Fox Hills aquifer is a potential source that could be used to supplement the existing municipal water supplies of the communities of Erie, Lafayette, Louisville, and Superior. The altitude of the potentiometric surface has declined as much as 300 feet in parts of the area in and adjacent to the major centers of pumping, but the data also i---d'cate little change in water levels in the area generally west and north of Coal Creek. The increase in con­ struction of wells and the associated increase in pumping over the last 20 years has slightly modified the shape of the potentiometric surface. The shape and modification of the potentiometric surface also is affected by faulting of the aquifer in the area. In the next 20 years increased pumpage probably will cause a greater change in the potentiometric surface than has occurred during the last 20 years. These changes will include greater depths to the potentiometric sur­ face, an increase in pumping lifts and costs, and decreased discharge to Boulder Creek valley.

Aggregate sand thickness of the aquifer determined from well logs ranges from k2 to 360 feet and the mean thickness is 229 feet. About 5 million acre-feet of water is in storage in the aquifer.

Reported yields from 93 wells ranged from 1 to 90 gallons per minute. The average yield was 22 gallons per r.Jnute. A plot of well yield versus aggregate sand thickness indicates that yields tended to be larger from areas of greater aggregate sand thickness.

Water moving through the aquifer comes into contact with coal and other beds of carbonaceous material which causes the water to change from a sodium calcium bicarbonate type to a sodium calcium sulfate type. Analyses of water samples collected from \k wells indicate that there is a change in water quality down- gradient from the recharge areas. Nitrite plus nitrate concentrations in water from three wells, fluoride concentrations in water from two wells, and selenium concentrations in water from three wells exceeded the maximum limits for public- water supplies established by the U.S. Environmental Protection Agency (1976).

16

REFERENCES

Cochran, D. M., and Robinson, C. S., 1973, Ground water in Paclamar Farm area, Boulder County, Colorado, and results of pumping test of Crown Mine: Lakewood, Colo., Charles S. Robinson & Associates, Inc., 34 p.

Colton, R. B. , 1978, Geologic map of the Boulder-Fort Col 1ins-Greeley area, Colo­ rado: U.S. Geological Survey Miscellaneous Investigations Series Map 1-855-G, scale 1:100,000.

Colton, R. B., and Anderson, L. W., 1977, Preliminary geologic map of the Erie quadrangle, Boulder, Weld, and Adams Counties, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-882, scale 1:24,000.

Colton, R. B., and Lowrie, R. L., 1973, Map showing mined areas of the Boulder- Weld coal field, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-513, scale 1:24,000.

Jenkins, E. D., 1961, Records and logs of selected wells and test holes, and chem­ ical analyses of ground water in the Boulder area, Colorado: Colorado Water Conservation Board Ground-Water Basic-Data Report 5, 30 p.

Lohman, S. W., 1972, Ground-water hydraulics: U.S. Geological Survey Professional Paper 708, 69 p.

Machette, M. N., 1977 [1978], Geologic map of the Lafayette quadrangle, Adams, Boulder, and Jefferson Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-1392, scale 1:62,500.

McConaghy, J. A., Chase, G. H., Boettcher, A. J., and Major, T. J., 1964, Hydro- geologic data of the Denver Basin, Colorado: Colorado Water Conservation Board Ground-Water Basic-Data Report 15, 224 p.

Spencer, F. D., 1961, Bedrock geology of the Louisville quadrangle, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-151, scale 1:24,000.

Trimble, D. E., 1975, Geologic map of the Niwot quadrangle, Boulder County, Colo­ rado: U.S. Geological Survey Geologic Quadrangle Map GQ-1229, scale 1:24,000.

U.S. Environmental Protection Agency, 1976, National interim primary drinking water regulations: U.S. Environmental Protection Agency 570/9~76-003, 159 p.

____1977, National secondary drinking water regulations: Federal Register, v. 42, no. 62, Thursday, March 31, 1977, Part I, p. 17143-17147.

17