horrocks engineers inc. - jones & associates · horrocks engineers inc. 2162 west grove...

Engineering & Geosciences

14425 South Center Point Way Bluffdale, Utah 84065 Phone (801) 501-0583 | Fax (801) 501-0584

Geotechnical Investigation for the Pavement Design

1100 West and Highway 91 Intersection Project Brigham City, Utah

GeoStrata Job No. 320-010

January 4, 2013

Prepared for:

Horrocks Engineers Inc. 2162 West Grove Parkway, Suite 400

Pleasant Grove, Utah 84062

Attention: Mr. Doug Graham, P.E.

Copyright 2012 GeoStrata i R320-010

TABLE OF CONTENTS

1.0 EXECUTIVE SUMMARY ..................................................................................................................... 1

2.0 INTRODUCTION ................................................................................................................................... 2

2.1 PURPOSE AND SCOPE OF WORK ............................................................................................... 2

2.2 PROJECT DESCRIPTION ............................................................................................................... 2

3.0 METHOD OF STUDY ............................................................................................................................ 3

3.1 FIELD INVESTIGATION ................................................................................................................ 3

3.2 LABORATORY TESTING .............................................................................................................. 3

3.3 ENGINEERING ANALYSIS ........................................................................................................... 4

4.0 GENERALIZED SITE CONDITIONS ................................................................................................. 5

4.1 SURFACE CONDITIONS ............................................................................................................... 5

4.2 SUBSURFACE CONDITIONS ........................................................................................................ 5

4.2.1 Soils ......................................................................................................................................... 5

4.2.2 Groundwater ............................................................................................................................ 6

5.0 GEOLOGIC CONDITIONS .................................................................................................................. 7

5.1 GEOLOGIC SETTING ..................................................................................................................... 7

5.2 SEISMICITY AND FAULTING ...................................................................................................... 7

5.3 OTHER GEOLOGIC HAZARDS .................................................................................................... 8

5.3.1 Liquefaction ............................................................................................................................. 9

5.3.2 Lake Flooding .......................................................................................................................... 9

5.3.3 Seiches ................................................................................................................................... 10

5.3.4 Shallow Groundwater ............................................................................................................ 10

6.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS .......................................................... 11

6.1 GENERAL CONCLUSIONS ......................................................................................................... 11

6.2 EARTHWORK ............................................................................................................................... 11

6.2.1 General Site Preparation and Grading ................................................................................. 11

6.2.2 Excavations for Conventional Pavement Reconstruction ...................................................... 12

6.2.3 Excavation Observation and Plan Review ............................................................................. 12

6.2.4 Temporary Excavation Stability ............................................................................................ 12

6.2.5 Borrow, Granular Borrow, Granular Backfill Borrow and Compaction .............................. 13

6.3 MOISTURE PROTECTION AND SURFACE DRAINAGE ........................................................ 14

6.4 FLEXIBLE PAVEMENT DESIGN ................................................................................................ 14

6.5 SOIL CORROSION AND REACTIVITY ..................................................................................... 15

Copyright 2012 GeoStrata ii R320-010

7.0 CLOSURE .............................................................................................................................................. 17

7.1 LIMITATIONS ............................................................................................................................... 17

7.2 ADDITIONAL SERVICES ............................................................................................................ 17

8.0 REFERENCES CITED ..................................................................................................................... 19

APPENDIX

Appendix A Plate A-1 Site Vicinity Map

Plate A-2 Exploration Location Map

Plate A-3 Surficial Geologic Map

Appendix B Plates B-1 to B-4 Boring Logs

Plate B-5 Key to Soil Symbols and Terms

Appendix C Plate C-1 Lab Summary Report

Plate C-2 Atterberg Limits

Plate C-3 Grain Size Distribution

Plates C-4 to C-5 Compaction and CBR Tests

Copyright 2012 GeoStrata 1 R320-010

1.0 EXECUTIVE SUMMARY

This report presents the results of a geotechnical investigation conducted for the proposed

construction of the intersection of 1100 West and Highway 91 in Brigham City, Utah. The

proposed improvements will include the construction of approximately 1,100 feet of new

roadway along the 1100 West alignment as well as approximately 1,800 feet of additional

turning lane area along Highway 91. The purposes of this investigation were to assess the nature

and engineering properties of the subsurface soils at the proposed site and to provide

recommendations for general site grading and the design and construction of the new roadways.

Based on the four borings drilled for this investigation, subgrade soils along the proposed 1100

West alignment generally consist of 0 to 6 inches of fill soils composed of Poorly Graded

GRAVEL (GP-GM) with silt and sand. Native soils were encountered under the fill soils, and

generally consisted of soft to medium stiff Sandy Lean CLAY (CL) and Lean CLAY (CL), as

well as loose Silty SAND (SM). The subgrade soils along the Highway 91 alignment generally

consist of 6 to 10 feet of fill soils composed of Poorly Graded GRAVEL (GP-GM) with silt and

sand as well as Poorly Graded SAND (SP) with gravel. Native soils underling the fill soils

consist of Lean CLAY (CL), Sandy Lean CLAY (CL), Sandy SILT (ML) and Silty SAND (SM).

Groundwater was encountered in each of the boreholes at depths ranging from 1 to 13 feet below

the existing site grade. Groundwater conditions can be expected to rise several feet depending on

the time of year. Based on the subsurface conditions encountered at the site, it is our opinion that

the subject site is suitable for the proposed construction provided that the recommendations

contained in this report are complied with. The following recommendations and design

parameters are discussed within this report.

A California bearing ratio (CBR) of 4.1 was determined for the subgrade soil encountered along

the roadway alignments, indicating that the native soils can be expected to provide poor

pavement support. Asphalt, untreated base course, and granular borrow thickness

recommendations are presented in Section 6.4 of this report.

NOTICE: The scope of services provided within this report is limited to the assessment of the existing subsurface conditions for the proposed roadway improvement. In the event that existing conditions change, results and recommendations contained in this report may need to be modified. This executive summary is not intended to replace the report of which it is part and should not be used separately from the report. The executive summary is provided solely for purposes of overview. The executive summary omits a number of details, any one of which could be crucial to the proper application of this report.


2.0 INTRODUCTION

2.1 PURPOSE AND SCOPE OF WORK

This report presents the results of a geotechnical investigation conducted for the proposed

intersection to be constructed at 1100 West and Highway 91 in Brigham City, Utah. The

purposes of this investigation were to assess the nature and engineering properties of the

subsurface soils at the proposed site and to provide recommendations for general site grading and

the design and construction of the new roadway and other associated improvements.

The scope of work completed for this study included a site reconnaissance, subsurface

exploration, soil sampling, laboratory testing, engineering analyses, and preparation of this

report. Our services were performed in accordance with our proposal and signed authorization,

dated June 21, 2012 .The recommendations contained in this report are subject to the limitations

presented in the "Limitations" section of this report (Section 7.1).

2.2 PROJECT DESCRIPTION

The project as planned will consist of the reconstruction of the intersection of 1100 West and

1100 South (Highway 91) in Brigham City, Utah. We understand that this reconstruction will

involve the construction of approximately 1,100 feet of roadway along 1100 West as well as

adding approximately 1,800 feet of additional lane area along either direction of Highway 91.

The location of the project site is shown on the Site Vicinity Map, Plate A-1. It is our

understanding that the new portions of both roadways constructed approximately 0 to 10 feet

above native grades in order to tie in with the existing roadways. Improvements may also include

sidewalk and curb and gutter additions.


3.0 METHOD OF STUDY

3.1 FIELD INVESTIGATION

As a part of this investigation, subsurface soil conditions were explored by advancing four

exploratory boreholes along the proposed roadway alignments, with two boreholes located along

1100 West and another two boreholes located along Highway 91. The boreholes were advanced

to depths ranging from 5 to 17 feet below the existing site grade. The approximately locations of

the explorations are shown on the Exploration Location Map, Plate A-2 in Appendix A.

Exploration points were selected to provide a representative cross section of the subsurface soils

along the proposed roadway alignment. Subsurface conditions encountered in the explorations

were logged at the time of the exploration by a qualified engineer according to the USCS

Classification System and are presented in Appendix B, Plates B-1 to B-4. A Key to Soil

Symbols and Terms used on the boring logs may be found on Plate B-5.

The boreholes B-1 through B-3 were advanced using a truck-mounted CME-75 drill rig.

Relatively disturbed soil samples were obtained with use of standard split spoon, California-type,

and Shelby tube samplers. Bulk samples were also retrieved from the drill cuttings in the upper

few feet of the borings. Due to truck accessibility, borehole B-4 was hand augered. All samples

were transported to our laboratory for testing to evaluate engineering properties of the various

earth materials observed. The soils were classified according to the Unified Soil Classification

System (USCS) by the Geotechnical Engineer. Classifications for the individual soil units are

shown on the attached Borehole Logs.

3.2 LABORATORY TESTING

Geotechnical laboratory tests were conducted on bulk soil samples obtained during our field

investigation. The laboratory testing program was designed to evaluate the engineering

characteristics of onsite earth materials. Laboratory tests conducted during this investigation

include:

- Insitu Moisture Determinations

- Grain Size Distribution Analysis (AASHTO T-27)

- Atterberg Limits (AASHTO T-89/T-90)


- Maximum Dry Density and Optimum Moisture Content (AASHTO T-99)

- California Bearing Ratio (AASHTO T-193)

The results of laboratory tests are presented on the Boring Logs in Appendix B (Plates B-1 to B-

4) as well as the Laboratory Summary Table and the test results plates presented in Appendix C

(Plates C-1 to C-5).

3.3 ENGINEERING ANALYSIS

Engineering analyses were performed using soil data obtained from the laboratory test results

and empirical correlations from material density, depositional characteristics and classification.

Appropriate factors of safety were applied to the results consistent with industry standards and

the accepted standard of care.


4.0 GENERALIZED SITE CONDITIONS

4.1 SURFACE CONDITIONS

The proposed 1100 West roadway alignment is oriented approximately north-south, while

Highway 91 is oriented approximately east-west. Both alignments are roughly level. Currently,

1100 West terminates approximately 350 feet north of Highway 91. The proposed alignment of

1100 West along both sides of Highway 91 is currently occupied by undeveloped, moderately

vegetated, agricultural lots. The proposed alignment is bordered by commercial property to the

east and undeveloped properties to the north, south, and west.

4.2 SUBSURFACE CONDITIONS

As previously mentioned, the subsurface soil conditions were explored along the proposed

roadway alignments by advancing four exploratory boreholes to depths ranging from 5 to 17 feet

below the existing site grade. The soils encountered in the borings were visually classified and

logged during our field investigation and are included on the boring logs in Appendix B (Plates

B-1 to B-4). The subsurface conditions encountered during our investigation are discussed

below.

4.2.1 Soils

Based on our observations and geologic literature review, the subject alignment is overlain by 0

to 10 feet of fill soils. Underlying the fill we encountered upper Pleistocene-aged lacustrine

deposits which extended to the full depth of our investigation. The geologic units encountered

are discussed below;

Fill: Generally consists of medium dense, moist to very moist, brown to dark brown Poorly

Graded GRAVEL (GP-GM) with silt and sand as well as Poorly Graded SAND (SP) with gravel,

although occasional seams of clayey soil were observed throughout this material. Typically

gravel diameter ranged from approximately 1½ to 2 inches. Occasional clasts of concrete were

also observed. It is likely that the fill soils encountered in boreholes B-1 and B-2 within

Highway-91 right of way was placed and compacted in accordance with UDOT standards. Fill

soils were encountered in borehole B-3 is likely undocumented. Where encountered, the fill soils

ranged from 1 to 10 feet in thickness.


Upper-Pleistocene Lacustrine Deposits: The lacustrine deposits encountered at the site are

composed of Lean CLAY (CL), Sandy Lean CLAY (CL), Sandy SILT (ML), and Silty SAND

(SM). In general, these deposits were moist stiff to soft, moist to wet, and light brown to black in

color. The clay typically had low plasticity and the sand was typically fine-grained. Occasional

seams of orange iron staining as well as preserved organic material were observed throughout

this soil unit. These deposits persisted to the full depth of our investigation.

The stratification lines shown on the enclosed test pit logs represent the approximate boundary

between soil types. The actual in-situ transition may be gradual. Due to the nature and

depositional characteristics of the native soils, care should be taken in interpolating subsurface

conditions; soil types may vary between and/or beyond exploration locations.

4.2.2 Groundwater

Groundwater was encountered in each of the boreholes advanced as part of our investigation at

depths ranging from 1 to 13 feet below the existing site grade. Based on the groundwater

elevations encountered in the boreholes, it appears that groundwater is near the native ground

elevation. Seasonal fluctuations in precipitation, surface runoff from adjacent properties, or other

on or offsite sources may also increase moisture conditions at the site. Based on the season of our

investigation (winter), we anticipate groundwater to be near its seasonal average, however

groundwater conditions can be expected to rise several feet depending on the time of year.


5.0 GEOLOGIC CONDITIONS

5.1 GEOLOGIC SETTING

The subject site is located at an elevation of approximately 4,260 feet in Brigham City, Utah.

Brigham City is located in the northern portion of the Salt Lake Basin, which is a deep,

sediment-filled structural basin of Cenozoic age flanked by the Wasatch Range and Wellsville

Mountains to the east and the Promontory Mountains, the Spring Hills, and the West Hills to the

west (Hintze, 1980). The southern portion of the Salt Lake Basin is bordered on the west by the

east shore of the Great Salt Lake. The Wasatch Range is the easternmost expression of

pronounced Basin and Range extension in north-central Utah.

The near-surface geology of the Salt Lake basin is dominated by sediments, which were

deposited within the last 30,000 years by Lake Bonneville (Scott and others, 1983; Hintze,

1993). As the lake receded, streams began to incise large deltas that had formed at the mouths of

major canyons along the Wasatch Range, and the eroded material was deposited in shallow lakes

and marshes in the basin and in a series of recessional deltas and alluvial fans. Sediments toward

the center of the valley are predominately deep-water deposits of clay, silt and fine sand.

However, these deep-water deposits are in places covered by a thin post-Bonneville alluvial

cover. Surface sediments at the site are mapped as upper Pleistocene-aged lacustrine silt and clay

related to the Provo and Bonneville shorelines (Personius, 1992).

5.2 SEISMICITY AND FAULTING

The site lies on the east side of the north-south trending belt of seismicity known as the

Intermountain Seismic Belt (ISB) (Hecker, 1993). The ISB extends from northwestern Montana

through southwestern Utah. An active fault is defined as a fault that has had activity within the

Holocene (<11ka). No active faults are reported to run through or immediately adjacent to the

site (Black and others, 2003). The site is located approximately ½ mile southwest of the Brigham

City segment of the Wasatch fault zone. The Brigham City segment is reported to be active and

thought to generate earthquakes of approximate magnitude 7.0 to 7.5 every 1300 ±200 years

(Black and others, 2004). The site is also located approximately 30 miles northeast of the East

Great Salt Lake fault zone (Hecker, 1993). Evidence suggests that this fault zone has been active

during the Holocene (0 to 10,000 yrs) and has segment lengths comparable to that of the

Wasatch fault zone, indicating that it is capable of producing earthquakes of a comparable


magnitude (7.5 Ms). Analyses of the ground shaking hazard along the Wasatch Front suggest

that the Wasatch Fault Zone is the single greatest contributor to the seismic hazard in Wasatch

front region.

Seismic hazard maps depicting probabilistic ground motions and spectral response have been

developed for the United States by the U.S. Geological Survey as part of NEHRP/NSHMP

(Frankel et al, 1996). These maps have been incorporated into both NEHRP Recommended

Provisions for Seismic Regulations for New Buildings and Other Structures (FEMA, 1997) and

the International Building Code (IBC) (International Code Council, 2006). Spectral responses

for the Maximum Considered Earthquake (MCE) are shown in the table below. These values

generally correspond to a two percent probability of exceedance in 50 years (2PE50) for a “firm

rock” site. To account for site effects, site coefficients which vary with the magnitude of spectral

acceleration are used. Based on our field exploration, it is our opinion that this location is best

described as a Site Class D. The spectral accelerations are shown in the table below. The spectral

accelerations are calculated based on the site’s approximate latitude and longitude of 41.4866˚

and -112.0349˚ respectively. Based on IBC, the site coefficients are Fa=1.00 and Fv= 1.50. From

this procedure the peak ground acceleration (PGA) is estimated to be 0.54g.

MCE Seismic Response Spectrum Spectral Acceleration Values for IBC Site Class Da

Site Location:

Latitude = 41.4866 N Longitude = -112.0349 W

Site Class D Site Coefficients: Fa = 1.00 Fv = 1.50

Spectral Period (sec) Response Spectrum Spectral Acceleration (g)

0.2 SMS=(Fa*Ss=1.00*1.36= 1.36

1.0 SM1=(Fv*S1=1.50*0.54= 0.81 a IBC 1615.1.3 recommends scaling the MCE values by 2/3 to obtain the design spectral response acceleration values; values reported in the table above have not been reduced.

5.3 OTHER GEOLOGIC HAZARDS

Geologic hazards can be defined as naturally occurring geologic conditions or processes that

could present a danger to human life and property or significantly impact the cost of

development. These hazards must be considered before development of the site. There are

several hazards in addition to seismicity and faulting that, if present at the site, should be

considered in the design of critical facilities such as structures designed for human occupancy or


critical facilities that support emergency response or life-sustaining activity. The hazards

considered for this site include liquefaction, lake flooding, seiche, and shallow groundwater.

5.3.1 Liquefaction

Certain areas within the Intermountain region possess a potential for liquefaction during seismic

events. Liquefaction is a phenomenon whereby loose, saturated, granular soil deposits lose a

significant portion of their shear strength due to excess pore water pressure buildup resulting

from dynamic loading, such as that caused by an earthquake. Among other effects, liquefaction

can result in densification of such deposits causing settlements of overlying layers after an

earthquake as excess pore water pressures are dissipated. The primary factors affecting

liquefaction potential of a soil deposit are: (1) level and duration of seismic ground motions; (2)

soil type and consistency; and (3) depth to groundwater.

Referring to the “Liquefaction Potential Brigham City,” published by the Utah Emergency

Operations Plan, the subject site is located within an area currently designated as "high" for

liquefaction potential. Groundwater was encountered during our investigations at depths ranging

from 1 to 13 feet below the existing site grade. Due to the presence of this shallow groundwater,

there is a high potential that the site will be impacted by liquefaction. A liquefaction analysis was

beyond the scope of this investigation. However, if the client wishes to have a greater

understanding of the liquefaction potential for soils at depth, a liquefaction analysis should be

completed.

5.3.2 Lake Flooding

A flood is the stage or height of water above some given datum, such as a commonly occupied

lake shoreline. Floods are recurrent natural events which become a hazard to residents of a flood

plain or shoreline whenever water rises to the extent that life and property are threatened.

Although fluctuating water levels are a problem in lakes, they are especially acute in lakes

which, like the Great Salt Lake, have no outlet. Natural factors causing fluctuations include

precipitation, evaporation, runoff, groundwater, ice, aquatic growth, and wind.

Using available historical and scientific data on the Great Salt Lake, lake experts have

recommended that properties located at elevations lower than 4,217 feet be reserved as

“Beneficial Development Areas”. Within these areas, it is recommended that development take

place in a manner that will encourage the maximum use of the land for the people of Utah while


avoiding unnecessary disaster losses. As mentioned previously, the subject site is located at an

elevation of 4,260 feet. As such, it is considered very unlikely that the site will be impacted by

lake flooding from the Great Salt Lake.

5.3.3 Seiches

Oscillations in the surface of a landlocked body of water can produce unusually large waves, or

sieches. Seiches may be generated by wind, landslides, and/or earthquake effects such as ground

shaking or surface fault rupture. The magnitude of the seiches caused by landslides or surface

fault rupture depends on the amount of water and ground displacement, whereas the magnitude

of the seiches caused by wind and ground shaking is determined by the degree or resonance

between the water body and periodic driving force.

Studies of wind seiches in the Great Salt Lake concluded that the maximum wave amplitude is

expected to be about 2 feet; no systematic or theoretical studies of landslide or earthquake-

induced seiches have been made. However, seiches more than 12 feet in height were reported on

the lake during the 1909 Hansel Valley earthquake (magnitude 6). The elevation of the surface of

the Great Salt Lake as measured in October of 2012 was approximately 4,201 feet, whereas the

site is located at an elevation of approximately 4,260 feet. As such, it is considered very unlikely

that the site will be impacted by seiches created during a seismic event.

5.3.4 Shallow Groundwater

Shallow groundwater flooding is a hazard that can cause the flooding of excavated areas where

the depth of excavation exceeds the depth of the local water table. Shallow groundwater can lead

to increased construction costs and delays, as well as potentially dangerous conditions in

excavated trenches. Shallow groundwater flooding should be considered when designing

habitable structures that require excavation that may exceed the depth to the shallow

groundwater.

During our subsurface investigation, shallow groundwater was observed to vary from 1 to 14 feet

below the existing site grade. This was largely due to the presence of undocumented fill soils at

various portions of the site. It should be anticipated that the groundwater can rise several feet

during wet cycles and could impact site development. The contractor should anticipate

dewatering trenches and excavations deeper than 1 foot or possibly shallower during spring or

other times of the year when groundwater may fluctuate.


6.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS

6.1 GENERAL CONCLUSIONS

Supporting data upon which the following recommendations are based have been presented in

the previous sections of this report. The recommendations presented herein are governed by the

physical properties of the soils encountered in the exploratory borings and our understanding of

the project as discussed in the PROJECT DESCRIPTION section of this report. If subsurface

conditions other than those described in this report are encountered in conjunction with

construction, and/or if design and layout changes are initiated, GeoStrata must be informed so

that our recommendations can be reviewed and revised as changes in conditions may require.

Changes in subsurface conditions that would necessitate further review include but are not

limited to: fluctuating groundwater or moisture content conditions, soils that are soft, collapsible,

expansive, or pumping, and soil types encountered that were not encountered during this

exploration or addressed in this report.

Based on the subsurface conditions encountered at the site, it is our opinion that the subject site

is suitable for the proposed development provided that the recommendations contained in this

report are incorporated into the design and construction of the project. The majority of the

subgrade soils encountered along the alignment consist of relatively soft, moist, fine-grained

material. Based on the results of our laboratory testing, these soils are anticipated to provide

relatively poor pavement support.

The following sub-sections present our recommendations for general site grading, fills, and

pavement sections.

6.2 EARTHWORK

Prior to the placement of any roadway improvements, general site grading is recommended to

provide proper drainage and moisture control on the subject property and to aid in preventing

differential movement as a result of variations in moisture conditions.

6.2.1 General Site Preparation and Grading

Below any proposed improvements, we recommend that all vegetation, heavily rooted topsoil,

debris, or otherwise unsuitable soils be removed. Where fill soils are exposed, the subgrade

should be scarified at least 12 inches and recompacted. All A-1 soils should be compacted to at


least 96% of the maximum dry density, as determined by AASHTO T180 (modified Proctor). All

other soils should be compacted to 96% of the maximum dry density as determined by AASHTO

T99 (standard proctor). The moisture content should be within 3% of optimum. Once the

scarification and recompaction is completed, the exposed soils should be proof-rolled with heavy

rubber-tired equipment such as a scraper or loader. Any soft/loose areas identified during proof-

rolling should be removed and replaced with structural fill as described in Section 6.2.5 of this

report or stabilized as recommended in Section 6.2.6. Following proof rolling and removal of

soft/loose areas, grading may be conducted to bring the site to grade.

6.2.2 Excavations for Conventional Pavement Reconstruction

Unsuitable soils that include soft, loose, or otherwise deleterious soils beneath pavements should

be over-excavated and replaced with structural fill. If over-excavation is required, the excavation

should extend a minimum of one foot laterally for every foot of depth of over-excavation.

Excavations should extend laterally at least two feet beyond pavements. If materials are

encountered that are not represented in the borehole logs or may present an engineering concern,

GeoStrata should be notified so observations and further recommendations as required can be

made.

Prior to placing engineered fill, any loose soils in the excavation bottom should be removed or

moisture conditioned as necessary at, or slightly above, optimum moisture content (OMC), and

compacted. All A-1 soils should be compacted to at least 96% of the maximum dry density, as

determined by AASHTO T180 (modified Proctor). All other soils should be compacted to 96%

of the maximum dry density as determined by AASHTO T99 (standard proctor). The moisture

content should be within 3% of optimum.

6.2.3 Excavation Observation and Plan Review

We recommend that a GeoStrata representative be on-site during all excavations to assess the

exposed subgrade soils for pavements. We further recommend that the Geotechnical Engineer be

allowed to review the grading plans when prepared to evaluate the compatibility of these

recommendations.

6.2.4 Temporary Excavation Stability

Based on Occupational Safety and Health Administration (OSHA) guidelines for excavation

safety, trenches with vertical walls up to 5 feet in depth may be occupied, however, the presence


of fill soils, loose soils, or wet soils may require that the walls be flattened to maintain safe

working conditions. When the trench is deeper than 5 feet, we recommend a trench-shield or

shoring be used as a protective system to workers in the trench. Based on our soil observations,

laboratory testing, and OSHA guidelines, native soils at the site classify as Type C soils. Deeper

excavations, if required, should be constructed with side slopes no steeper than one and one-half

horizontal to one vertical (1.5H:1V). If wet conditions are encountered, side slopes should be

further flattened to maintain slope stability. Alternatively shoring or trench boxes may be used to

improve safe work conditions in trenches. The contractor is ultimately responsible for trench and

site safety. Pertinent OSHA requirements should be met to provide a safe work environment. If

site specific conditions arise that require engineering analysis in accordance with OSHA

regulations, GeoStrata can respond and provide recommendations as needed.

It should be understood that the excavation recommendations presented above are based on the

native soil and groundwater conditions encountered within our borings. It is possible that utility

trenches or other features will be encountered which will present differing conditions, such as

soft and loose soils or localized areas of high groundwater. Caving of trenches in these areas

where such conditions are encountered is possible and the contractor should plan accordingly.

We recommend that a GeoStrata representative be on-site during all excavations to assess the

exposed foundation soils. We also recommend that the Geotechnical Engineer be allowed to

review the grading plans when they are prepared in order to evaluate their compatibility with

these recommendations.

6.2.5 Borrow, Granular Borrow, Granular Backfill Borrow and Compaction

All fill placed for the support of the roadway or flatwork concrete should consist of Borrow,

Granular Borrow, or Granular Backfill Borrow in accordance with UDOT standards. We

anticipate that the majority of the existing near surface soils along the alignment will not be

suitable for use as Borrow. All borrow material should meet the requirements of and be placed in

accordance with UDOT Standard Specifications Section 02056. All borrow material should be

free of vegetation and debris, and contain no inert materials larger than 3-inches in nominal size,

nominal size will be less for the granular backfill borrow. All backfill should be placed in

maximum 12-inch loose lifts or less, depending on the size of compaction equipment, and

compacted on a horizontal plane, unless otherwise approved by the Geotechnical Engineer. All

A-1 soils in compacted fills beneath all footings and pavements should be compacted to at least

96% of the maximum dry density, as determined by AASHTO T180 (modified Proctor). All

other backfill soils should be compacted to 96% of the maximum dry density as determined by


AASHTO T99 (standard proctor). The moisture content should be within 3% of optimum for all

structural fill. Any imported fill materials should be approved prior to importing. Also, prior to

placing any fill, the excavations should be observed by the Geotechnical Engineer to confirm

that unsuitable materials have been removed. In addition, proper grading should precede

placement of fill, as described in the General Site Preparation and Grading subsection of this

report.

6.3 MOISTURE PROTECTION AND SURFACE DRAINAGE

Precautions should be taken during and after construction to minimize over-wetting of soils

beneath flatwork concrete and pavements. Moisture should not be allowed to infiltrate soils in

the vicinity of the proposed roadway alignment. Grading should be planned and executed to

provide positive surface drainage away from the alignment. We recommend using a minimum

surface slope of 2 percent for graded earth surfaces.

Over-wetting of soils prior to or during construction may result in softening and pumping of the

subgrade. This may result in equipment mobility problems and/or difficulty in achieving

compaction, and consequently, necessitate soil stabilization measures.

6.4 FLEXIBLE PAVEMENT DESIGN

As mentioned previously, 1 to 10 feet of fill soil was encountered within our borings. The fill

sections were thickest in boreholes B-1 and B-2, which were drilled within the existing Highway

91 pavement section. Boreholes B-3 and B-4 were advanced along the proposed 1100 West

alignment, where fill sections of 0 to 1 foot were encountered. The SPT blow counts indicate that

the fill soils are generally medium dense to dense; however, it should be understood that there

may be areas of fill with debris and/or low densities which could cause pavement settlement and

distress. Complete removal and replacement of the existing fill would be required to eliminate

this risk; however, removal and replacement of the entire existing fill could be cost prohibitive.

In general, the deeper the existing fill is removed and replaced the lower the risk of adverse

effects. As a minimum we recommend that where undocumented fill soils are exposed, the

subgrade should be scarified at least 12 inches and recompacted as recommended in Section

5.2.1; however, the risk associated with leaving the undocumented fill soils below the pavement

should be understood by the project owner prior to construction.


A bulk sample of the near surface soils was obtained from boring B-3 to assess the moisture-

density relationship and their capacity for pavement support. Laboratory testing yielded a CBR

value of 4.1% for the near surface soils. A second bulk sample of the fill soils was obtained from

boring B-1, and laboratory testing completed on this sample yielded a CBR value of 49%.

Traffic information for a section of Highway 91 that includes the subject interchange was

provided by the client. Based on the information provided, we estimate traffic for the Highway

91 turn lane and 1100 West will consist of 500 cars and 25 large trucks per day with 5 percent

growth per year. Using this traffic and a 20 year design lie, the total design equivalent axel loads

(ESAL’s is approximately 738,980 ESAL’s which was used for our assessment. For our

assessment a CBR value of 4.1% was utilized, and only a flexible pavement section was

considered. The software program WinPas was used in the design of the pavement section.

Based on the information presented above we recommend a minimum conventional pavement

section of 4½-inches of asphalt over 8-inches of untreated base and 13-inches of granular borrow

for both of the subject roadway alignments. Due to the shallow groundwater it is likely that soft

soils will be exposed following site grading and excavation recommend in Section 6.2.1 and

6.2.2. Where soft soils are encountered we recommend that that the granular borrow be increased

to 24 inches and that the granular borrow be underlain by a Tensar® TX-140, BX-1200, or

equivalent geotextile placed over native soils. This pavement section assumes that there is no

mixing over time between the granular borrow and the softer native layers below. In order to

prevent mixing of fines migration, and thereby prolong the life of the pavement section, we

recommend that the owner give consideration to placing a non-woven filter fabric between the

native soils and the granular borrow. We recommend that a Propex Geotex® NW-401, NW-406,

or a GeoStrata approve equivalent be used. It is anticipated that approximately 4 to 5 feet of

structural fill will be required in order to bring the proposed Highway 91 turn lanes up to design

grade. The recommended pavement sections should be incorporated into any planned fill

sections.

6.5 SOIL CORROSION AND REACTIVITY

Based on our experience in the area as well as with similar soils, the native silty soils are

anticipated to have a relatively low potential for sulfate attack on concrete, it is anticipated that

conventional Type I/II cement may be used for all concrete for this project.

Corrosion potential testing was not completed as part of this investigation; however, based on

our observations we anticipate that native soils will be corrosive to ferrous metal. Considerations


should be given to retaining the services of a qualified corrosion engineer to provide an

assessment of any metal that may be associated with the construction.


7.0 CLOSURE

7.1 LIMITATIONS

The recommendations contained in this report are based on limited field exploration, laboratory

testing, and our understanding of the proposed construction. The subsurface data used in the

preparation of this report were obtained from the explorations made for this investigation. It is

possible that variations in the soil and groundwater conditions could exist between and beyond

the points explored. The nature and extent of variations may not be evident until construction

occurs. If any conditions are encountered at this site that are different from those described in

this report, GeoStrata should be immediately notified so that we may make any necessary

revisions to recommendations contained in this report. In addition, if the scope of the proposed

construction changes from that described in this report, we should be notified.

This report was prepared in accordance with the generally accepted standard of practice at the

time the report was written. No warranty, expressed or implied, is made.

It is the Client's responsibility to see that all parties to the project including the Designer,

Contractor, Subcontractors, etc. are made aware of this report in its entirety. The use of

information contained in this report for bidding purposes should be done at the Contractor's

option and risk.

7.2 ADDITIONAL SERVICES

The recommendations made in this report are based on the assumption that an adequate program

of tests and observations will be made during the construction. GeoStrata staff should be on site

to observe compliance with these recommendations. These tests and observations should include,

but not necessarily be limited to, the following:

Observations and testing during site preparation, earthwork, and placement of granular

borrow, base course, and asphalt pavement.

Consultation as may be required during construction.

Asphalt compaction testing.


We also recommend that project plans and specifications be reviewed by GeoStrata to verify

compatibility with our conclusions and recommendations. Additional information concerning the

scope and cost of these services can be obtained from our office.

We appreciate the opportunity to be of service on this project. Should there be any questions

regarding the report or wish to discuss additional services, please do not hesitate to contact us at

(801) 501-0583.


8.0 REFERENCES CITED

Black, B.D., Hecker, S., Hylland, M.D., Christenson, G.E., and McDonald, G.N., 2003,

Quaternary Fault and Fold Database and Map of Utah: Utah Geological Survey Map 193DM. Federal Emergency Management Agency [FEMA], 1997, NEHRP Recommended Provisions for

Seismic Regulations for New Buildings and Other Structures, FEMA 302, Washington, D.C.

Frankel, A., Mueller, C., Barnard, T., Perkins, D., Leyendecker, E.V., Dickman, N., Hanson, S.,

and Hopper, M., 1996, National Seismic-hazard Maps: Documentation, U.S. Geological Survey Open-File Report 96-532, June.

Hecker, S., 1993, Quaternary Tectonics of Utah with Emphasis on Earthquake-Hazard

Characterization: Utah Geological Survey Bulletin 127, 157p. Hintze, L. F., 1980, Geologic Map of Utah: Utah Geological and Mineral Survey Map-A-1, scale

1:500,000. Hintze, L.F. 1993, Geologic History of Utah, Brigham Young University Studies, Special

Publication 7, 202p. International Building Code [IBC], 2006, International Code Council, Inc. Personius, S.F., 1992, Map of the Brigham City Segment and Adjacent Parts of the Weber

Segment of the Wasatch Fault Zone, Box Elder and Weber Counties, Utah, United Stated Geological Survey, Miscellaneous Investigations Series Map I-2107, Scale 1:50,000.

Scott, W.E., McCoy, W.D., Shorba, R.R., and Meyer, R., 1983, Reinterpretation of the exposed

record of the last two cycles of Lake Bonneville, western United States: Quaternary Research, v.20, p. 261-285.

0 1,000 2,000 3,000 4,000500Feet

1:24,000

Site Vicinity MapPlateA-1

Copyright GeoStrata, 2012

All Locations are Approximate. Base Map: USGS Topographic Map

obtained from the State of Utah AGRC

1100 West/U-91 IntersectionHorrocksBrigham City, UtahProject Number: 320-010

Approximate Site Location

0 100 200 300 40050Feet

1:3,000

Exploration Location MapPlateA-2


All Locations are Approximate. Base Map: 2009 HRO 1 Foot Orthophotography


1100 West/U-91IntersectionHorrocksBrigham City, UtahProject Number: 320-010

LegendBoring

B-1

B-3

B-2

B-4

0 1,100 2,200 3,300 4,400550Feet

1:24,000

Surficial Geologic MapPlateA-3


All Locations are Approximate. Base Map: USGS Topographic Map


1100 West/U-91 IntersectionHorrocksBrigham City, UtahProject Number: 320-010

Approximate Site Location

LegendContactFault, normal, approximately locatedFault, normal, well locatedWater BoundaryQa - surficial alluvium and colluviumQl - surficial Lake Bonneville depositsQm - surficial marsh depositsPCs - sedimentary and metasedimentary Fmswater

PlasticLimit

Dry

Den

sity

(pcf

)

Per

cen

t m

inu

s 2

00

N*

Mo

istu

re C

on

ten

t %

SPT BLOW COUNT

Project Number 320-010

Pla

stic

ity

In

dex

NE

W_L

OG

OF

BO

RIN

G (

A)

- IN

PR

OG

RE

SS

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2

FILL; (A-1-a) Poorly Graded GRAVELwith silt and sand - medium dense,brown to dark brown, moist to verymoist, with clay lenses, max particlesize 1.5"

WA

TE

R L

EV

EL

NOTES:

MATERIAL DESCRIPTION

N* - CORRECTED N1(60) EQUIVALENT SPT BLOW COUNT

- 2" O.D./1.38" I.D. SPLIT SPOON SAMPLER- 3" O.D./2.48" I.D. SAMPLER- 3" O.D. THIN-WALLED SHELBY SAMPLER- GRAB SAMPLE- Modified California Sampler

- MEASURED

WATER LEVEL

B-1

7.1

Moisture Content

and

Atterberg Limits

Bottom of Boring @ 11.5 Feet

(A-2-4) Silty SAND - light brown,moist to wet, loose, orange staining

(A-4) Sandy SILT - light brown, moist,medium stiff, orange staining

(A-6) Lean CLAY - brown, moist,medium stiff

- concrete debris

21

NP

18

13

20

100

SM

ML

CL

NP

Sheet 1 of 1

50-4

Liq

uid

Lim

it

UN

IFIE

D S

OIL

CL

AS

SIF

ICA

TIO

N

DEPTHS

AM

PL

ES

1020304050607080900

1

2

3

4

5

6

Copyright (c) 2012, GeoStrata

Plate

ELEVATION

J. Mattson

CME 75

Horrocks Engineering Inc.1100 West IntersectionBrigham City, UT

B - 1

10/30/12

10/30/12

10/30/12

N - OBSERVED UNCORRECTED BLOW COUNT

STATION

0

5

10

15

GR

AP

HIC

AL

LO

G

SAMPLE TYPE

GeoStrata Rep:

Rig Type:

Boring Type:

102030405060708090

ME

TE

RS

BORING NO:

LOCATION

OFFSET

STARTED:

COMPLETED:

BACKFILLED:

- ESTIMATED

DA

TE

MoistureContent

N

LiquidLimit

FE

ET

Per

cen

t m

inu

s 2

00

N*

Dry

Den

sity

(pcf

)

Mo

istu

re C

on

ten

t %

Moisture Content

and

Atterberg Limits

NP

PlasticLimit


Pla

stic

ity

In

dex

Sheet 1 of 1

NE

W_L

OG

OF

BO

RIN

G (

A)

- IN

PR

OG

RE

SS

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2




- MEASURED

WATER LEVEL

B-2

NOTES:

WA

TE

R L

EV

EL

FILL; (A-1-a) Poorly Graded GRAVELwith silt and sand - brown to darkbrown, moist to very moist, mediumdense, with clay lenses, max particlesize 1.5"

19.2

Bottom of Boring @ 17 Feet

(A-6) Lean CLAY - brown, moist tovery moist, medium stiff

(A-4) Sandy CLAY - black, moist tovery moist, medium stiff, roots andorganics throughout

FILL; (A-1-a) Poorly Graded SANDwith gravel - brown, very moist towet, medium dense, max particle size2"

67

11

64

75

41

15

100

CL

CL

NP19.2

93

Liq

uid

Lim

it

DEPTHS

AM

PL

ES

102030405060708090


STATION

SPT BLOW COUNT


Plate

0

1

2

3

4

5

6

ELEVATION

J. Mattson

CME 75


B - 2

10/30/12

10/30/12

10/30/12

UN

IFIE

D S

OIL

CL

AS

SIF

ICA

TIO

N

GeoStrata Rep:

Rig Type:

Boring Type:

0

5

10

15

GR

AP

HIC

AL

LO

G

SAMPLE TYPE

102030405060708090

LOCATION

BORING NO:

FE

ET

OFFSET

STARTED:

COMPLETED:

BACKFILLED:

ME

TE

RS

- ESTIMATED

MoistureContent

DA

TE

N

LiquidLimit

NP

Per

cen

t m

inu

s 2

00

Dry

Den

sity

(pcf

)

PlasticLimit

WA

TE

R L

EV

EL

Mo

istu

re C

on

ten

t %

Moisture Content

and

Atterberg Limits

SPT BLOW COUNTN*MATERIAL DESCRIPTION


Pla

stic

ity

In

dex

Sheet 1 of 1

NE

W_L

OG

OF

BO

RIN

G (

A)

- IN

PR

OG

RE

SS

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2



- MEASURED

WATER LEVEL

B-3

NOTES:

FILL; (A-1-a) Poorly Graded GRAVELwith silt and sand - brown, moist,dense

79.1

Bottom of Boring @ 11.5 Feet

(A-6) Lean CLAY - grey, very moist towet, soft, orange staining

(A-2-4) Silty SAND - light brown, verymoist to wet, loose, orange staining

(A-4) Sandy Lean CLAY - light brown,very moist, medium stiff, orangestaining

(A-4) SILT with sand - light brown,very moist, medium stiff, someorganics

CL

5

9

8

8

15

SM

CL

ML

NP

11

Liq

uid

Lim

it

DEPTHS

AM

PL

ES

102030405060708090


STATION


Plate

0

1

2

3

4

5

6

ELEVATION

J. Mattson

CME 75


B - 3

10/30/12

10/30/12

10/30/12

UN

IFIE

D S

OIL

CL

AS

SIF

ICA

TIO

N

GeoStrata Rep:

Rig Type:

Boring Type:

0

5

10

15

GR

AP

HIC

AL

LO

G

SAMPLE TYPE

102030405060708090

ME

TE

RS

BORING NO:

LOCATION

OFFSET

STARTED:

COMPLETED:

BACKFILLED:

- ESTIMATED

DA

TE

MoistureContent

N

LiquidLimit

FE

ET

B-4

LOCATION



- 2" O.D./1.38" I.D. SPLIT SPOON SAMPLER- 3" O.D./2.48" I.D. SAMPLER- 3" O.D. THIN-WALLED SHELBY SAMPLER- GRAB SAMPLE- Modified California Sampler WATER LEVEL

NOTES:

WA

TE

R L

EV

EL

Dry

Den

sity

(pcf

)

- MEASURED

BORING NO:

NE

W_L

OG

OF

BO

RIN

G (

A)

- IN

PR

OG

RE

SS

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2

(A-4) Sandy Lean CLAY - dark brown,moist, medium stiff, organics androots in top 6".

SPT BLOW COUNT


Pla

stic

ity

In

dex

Sheet 1 of 1F

EE

T

23.9

CL

23.9

Per

cen

t m

inu

s 2

00

Bottom of Boring @ 5 Feet

(A-2-4) Silty SAND - brown, wet,loose to medium dense.

(A-4) Sandy Lean CLAY - brown, verymoist, medium stiff.

N*

PlasticLimit

CL

SM

Mo

istu

re C

on

ten

t %

Moisture Content

and

Atterberg Limits

12.9

102030405060708090

STATION


UN

IFIE

D S

OIL

CL

AS

SIF

ICA

TIO

N


SA

MP

LE

S

SAMPLE TYPE

Liq

uid

Lim

it

GeoStrata Rep:

Rig Type:

Boring Type:

DEPTH

J. Mattson

Hand Auger


B - 4

102030405060708090

ELEVATION

0

5

10

15

GR

AP

HIC

AL

LO

G

- ESTIMATED

11/16/12

11/16/12

11/16/12

Plate

OFFSET

MoistureContent

ME

TE

RS

STARTED:

COMPLETED:

BACKFILLED:

0

1

2

3

4

5

6

LiquidLimit

N

DA

TE

Copyright GeoStrata , 2012

Soil Symbols Description Key

Plate

B-5

Horrocks Engineering Inc.

1100 West Intersection

Brigham City, Utah

Project Number: 320-010

Horrocks Engineering, Inc.

1100 West Intersection

Brigham City, UT

Project Number: 796-001

Copyright GeoStrata , 2012

Lab Summary Report

Plate

C - 1

Boring

No.

Sample

Depth

(feet)

USCS Soil

Classification

Natural

Moisture

Content

(%)

Optimum

Moisture

Content

(%)

Maximum

Dry

Density

(pcf)

Gradation Atterberg Limits

CBR (%) Gravel

(%)

Sand

(%) Fines (%)

Liquid

Limit

Plasticity

Index

B-1 0-5 SP-SM 7.1% 138.4 43.1 49.8 7.1 NP NP 49.0

B-2 10.0 ML 19.2% NP NP

B-3 0-5 ML 14.0% 110.3 5.8 15.1 79.1 NP NP 4.1

B-4 4.5 SM 23.9% 0.0 87.1 12.9

ATTERBERG LIMITS' RESULTS - ASTM D 4318

LIQUID LIMIT (%)

PL

AS

TIC

ITY

IN

DE

X (

%)

B-1

B-2

B-3

100

50

40

30

20

0 20 40 80

60

10

0

LL(%)

60

CL-ML

CL

ML MH

Sandy SILT, A-4

CH

PlateHorrocks Engineering Inc.1100 West IntersectionBrigham City, UTProject Number: 320-010 C - 2

C_A

TT

ER

BE

RG

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2

PL(%)

PI(%)

Fines(%)

Classification

NP

NP

NP

NP

NP

NP

NP

Depth(ft)

NP SILT with sand, A-4

Sample Location

0.0

10.0

1.0

Poorly Graded SAND with silt and gravel, A-1-a

NP

50

0.264

5.325

HYDROMETER

fine

LL

B-4

B-3

Cu

606

B-1

60

10 1 0.1 0.01 0.001

50

0.845

40

65

70

75

80

85

90

95

100

55

100

45

0

5

10

15

20

25

30

35

4.5

%Silt

GRAIN SIZE DISTRIBUTION - ASTM D422

14

Classification

50

%Gravel

1.0

3

B-1

B-3

B-4

1003/4

0.0

NP

12.5

%Sand

NP

49.8

NP

NP

40

PE

RC

EN

T F

INE

R B

Y W

EIG

HT

GRAIN SIZE (mm)

43.1

5.8

1/2

Plate

C - 3

Horrocks Engineering Inc.1100 West IntersectionBrigham City, UTProject Number: 320-010

0.0

15.1

87.1

35.50NP

NP

3/8

Cc

2001.5

medium

68

U.S. SIEVE OPENING IN INCHES

PI

U.S. SIEVE NUMBERS

2

D10

4

D100

SILT OR CLAY

4

D30

10

%Clay

C_G

SD

B

OR

ING

LO

GS

.GP

J G

EO

ST

RA

TA

.GD

T

12/1

7/1

2

0.137

PL

Poorly Graded SAND with silt and gravel, A-1-a

Silty SAND, A-2-44.5

1403

fine coarse

20

SILT with sand, A-4

79.1

0.15

0.0

7.1

12.9

30

Sample Location Depth

Sample Loctaion Depth

GRAVEL

4.75

16

COBBLESSAND

0.89

D60

1

coarse

1.0

horrocks engineers inc. - jones & associates · horrocks engineers inc. 2162 west grove...

Documents