geotechnical investigation · divide road water …...1.0 project information 1.1 purpose and scope...

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GEOTECHNICAL INVESTIGATION · DIVIDE ROAD WATER FACILITY GARFIELD COUNTY, COLORADO

March 7, 2012

Prepared For:

Mr. Kevin McDowell Encana Oil & Gas (USA), Inc. 370 17th Street, Suite 1700 Denver, CO 80202

Prepared By:

Yeh and Associates, Inc. 1525 Blake Avenue Glenwood Springs, CO 81601 Phone (970) 384-1500 Fax (970) 384-1501

Project No. 212-011

Divide Road Water Facility Project No. 212-011

TABLE OF CONTENTS

1.0 PROJECT INFORMATION ................................................................................... 1

1.1 Purpose and Scope ................................................................................... 1

1.2 Proposed Construction .............................................................................. 1

1.3 Site Conditions .......................................................................................... 2

1.4 Site Geology .............................................................................................. 2

2.0 SITE INVESTIGATION ............................................... : .......................................... 2

2.1 Subsurface Investigation ........................................................................... 2

2.2 Subsurface Conditions .............................................................................. 3 2.2.1 Groundwater .......................................................................................... 4

2.3 Site Grading ............................................................................................... 4

3.0 FOUNDATION RECOMMENDATIONS ................................................................ 5

3.1 Pump House Foundation ........................................................................... 5

3.2 Treatment Area and Storage Tank Foundations ....................................... 6

4.0 SEISMIC CONSIDERATIONS .............................................................................. 6

5.0 CONCRETE AND CORROSIVITY ........................................................................ 7

6.0 LIMITATIONS ........................................................................................................ 7

LIST OF FIGURES

Figure 1 - Approximate Site Location Figure 2 - Approximate Test Hole Locations Figure 3 - Treatment Area Drill Logs Figure 4 - Storage Tank Area Drill Logs Figure 5 - Drill Log legend Figures 6 and 7 - Sieve Analysis Test Results Laboratory Test Results and Summary Table

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1.0 PROJECT INFORMATION

1.1 Purpose and Scope

This report presents the results of our geotechnical investigation for the Divide Road Water

Facility in northern Garfield County. Colorado (Figure 1). The investigation was performed to

provide foundation design recommendations for proposed buildings. tanks. site grading and

surface drainage.

The site investigation consisted of geologic reconnaissance and exploratory test hole drilling to

investigate subsurface conditions. Test hole drilling was observed by a representative of Yeh

and Associates. Samples obtained during the field exploration were examined by the project

personnel and representative samples were subjected to laboratory testing to determine the

engineering characteristics of materials encountered. This report summarizes our field

investigation, the results of our analyses, and our conclusions and recommendations based on

the proposed construction, site reconnaissance, subsurface investigation, and results of the

laboratory testing.

1.2 Proposed Construction

From site plans dated January 28, 2012, provided by the client, proposed construction will

include new pads (upper and lower) with structures related to the collection, treatment and

storage of waste water associated with natural gas production. The upper pad will include

structures that include but are not limited to DAF units, sludge tanks, condensate storage tanks,

duplex pump houses, truck off load bays, off load tanks, fresh water tanks, separators, vapor

recovery units, generators, mcc, polymer storage, coagulant storage tanks, polymer and

coagulant mix tanks, flow equalizing tanks, high pressure pump house and a control equipment

room. We believe that the DAF units and high pressure pump house will be enclosed. Cuts of

5 feet or less are planned for the majority of the upper pad. Fills of up to 13 feet are planned on

the eastern edge to accommodate the access road and pump house. Fill slopes are planned

between 3H:1V and 4H:1V. A cut slope down to the lower pad is proposed at 2H:1V. The lower

pad area will consist of three storage tanks, 168 feet in diameter and 54 feet tall. A combination

of a berm and 5-foot high concrete containment wall is planned around the tanks. Cuts of

between 3 and 18 feet are planned for the tanks and cuts of up to 10 feet are planned for the

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Divide Road Water F acUity Project No. 212-011

pad with the exception of the south pad edge and corners, which will require up to 14.5 feet of

fill. Again, fill slopes are planned between 3H:1V and 4H:1V.

1.3 Site Conditions

The proposed Divide Road Water Facility was approximately 21 road miles north and west of

Parachute, Colorado (Figure 1) and was located on the Roan Plateau in the northern Piceance

Basin of western Colorado, a major gas production area made up of high plateaus, mesas,

ridges and deep valleys. The proposed site was located on a southwest trending ridge and was

undeveloped with a two-track unimproved road along the top of the ridge. The existing grade

was nearly level along the southwest trend of the ridge with elevations ranging from 8261 to

8286 feet. Divide Road was located adjacent to the north end of the site. Existing vegetation

included sage, scrub oak and other natural brush and grasses. At the time of our investigation,

the site was snow covered with drifts up to 3 feet deep.

1.4 Site Geology

The Piceance Basin of western Colorado is a complex of numerous anticlines and synclines and

a major gas production area. The asymmetrical, arc-shaped basin is 100 miles long by 50 miles

wide, is oriented northwest-southeast, and is deepest on the east edge. It is bounded

structurally on the northeast by the Axial Uplift, on the east by the White River Uplift/Grand

Hogback and the Elk Mountains, on the south by the Uncompahgre Uplift and on the west by

the Douglas Creek Arch.

Exposed in the project area was Tertiary age sedimentary rocks including the slopes and ledges

of light brown and gray siltstone and sandstone and slopes of siltstone and claystone of the

Uinta Formation. The surficial deposits included alluvium and residuum of the erosional surface

of the Uinta Formation which included clay, silt, sand and gravel.

2.0 SITE INVESTIGATION

2.1 Subsurface Investigation

Eleven test holes were drilled on February 14 and 15,2012. Test holes TH-1 through TH-6

were drilled in the proposed treatment area (upper pad) and test holes TH-7 through TH-11

were drilled in the general area of the proposed water storage tanks (lower pad). Yeh and

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Associates chose test hole locations and used a hand held GPS unit to field locate test holes.

Location accuracy is only within the limits of the methods/instrument used. Test hole depths

were drilled at least 5 feet below proposed elevations at the test hole location.

The locations of the test holes are presented in Figure 2. All test holes were advanced using a

CME 55 rubber track rig and test holes were advanced using 4-inch continuous flight auger to

pre-determined depths where a modified California or split-spoon sampler was used to record

blow counts and obtain samples. Bulk samples were also obtained at depths indicated on test

hole logs presented on Figures 3 and 4.

To perform the modified California penetration resistance tests, a 2.0-inch inside diarneter

sampler was seated at the bottom of the test hole, then driven up to 12 inches with blows of a

standard hammer weighing 140 pounds and falling a distance of 30 inches utilizing a "cat head"

hammer (ASTM 01586). The number of blows (Blow Count) required to drive the sampler 12

inches or a fraction thereof, constitutes the N-value. The N-value, when properly evaluated, is

an index of the consistency or relative density of the material tested. Test hole logs and legend

are presented on Figures 3 through 5.

2.2 Subsurface Conditions

Subsurface conditions generally consisted of topsoil over about 1- foot of silty sand underlain by

weathered to comparatively unweathered sandstone bedrock. Differentiation between the

topsoil and natural silty sand soils was difficult and therefore, topsoil depths were approximated.

Hard to very hard sandstone bedrock was encountered in all test holes at depths of between 1

and 5 feet from existing grades. The sandstone bedrock was occasionally cemented, but able

to be penetrated with a 4-inch auger.

One sandstone bedrock sample (test hole TH-6 at 2 feet) had 12 percent fines (material passing

the No. 200 sieve). Atterberg limit testing indicated the sample was non-liquid and non-plastic.

One weathered bedrock sample (test hole TH-9 at 2 feet) tested indicated 37 percent fines and

was non-liquid and non-plastic. Additionally, a water soluble sulfate was also performed on this

sample. Results are reported under the foundation concrete and corrosion section of this

report. The silty sand Classified as an SM according to the Unified Soil Classification System

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(USCS). Results of the laboratory testing are summarized in the Summary of Laboratory Test

Results.

2.2.1 Groundwater

Groundwater was not encountered during drilling and test holes were backfilled at completion of

drilling and sampling. Variations in groundwater conditions may occur seasonally. The

magnitude of the variation will be largely dependent upon the amount of spring snowmelt,

duration and intensity of precipitation, site grading changes, and the surface and subsurface

drainage characteristics of the surrounding area.

2.3 Site Grading

Cuts of up to 18 feet and fills of up to 14.5 feet are planned for the proposed construction.

Based on drilling and our observations, we believe that material can be excavated by

conventional construction equipment; however, hard to very hard sandstone bedrock

(occasionally cemented) may need to be excavated by means of heavy ripping and/or blasting.

We believe that proposed fill slopes of 3H:1V to 4H:1V and cut slopes of 2H:1V are appropriate

for the soil conditions at the site.

The on-site (cut) soils can be used in site grading fills provided the material is substantially free

of organic material, debris and particles are no larger than 6 inches. Areas to receive fill should

be stripped of vegetation, organic soils and debris. Topsoil is not recommended for fill material.

Fill should be placed in thin, loose lifts of 8 inches thick or less. We recommend fill materials be

moisture conditioned to within 2 percent of optimum moisture content and compacted to at least

95 percent of maximum standard Proctor dry density (ASTM D 698). Placement and

compaction of fill should be observed and tested by a representative of the geotechnical

engineer.

We believe that 3 to 13 feet of fill (northwest to southeast building corners) would likely result in

differential settlement of the pump house. For a differential fill depth of 10 feet, we would

estimate differential settlements on the order of 1 to 2 inches (or about 2 to 3 inches of total

movement), provided the fill is placed in general conformance with the recommendations above.

Total and differential movements cannot be totally eliminated. Movement tolerances should be

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determined by the structural engineer. If movements exceed the tolerances of the structure,

several alternatives such as moving the pump house into the cut side of the excavation or

penetrating the fill with a deep foundation system could be employed.

As an alternative, a deep foundation system could include drilled bedrock piers (shafts), helical

piers or micropiles. Typically, helical piers and micropiles are designed and installed by a

specialty contractor. We could provide recornrnendations for a deep foundation system, if

needed.

3.0 FOUNDATION RECOMMENDATIONS

We believe that the site is favorable for proposed construction. We believe structures for both

the upper pad (treatment area excluding purnp house) and lower pad (storage tanks) can be

supported by a footing, mat or pad foundation placed on sandstone bedrock. We believe that

the pump house can be supported by a footing, mat or pad foundation placed on controlled fill.

We believe that consolidation of the controlled fill would be low and therefore, a low risk of

associated foundation movement. If movements exceed structure tolerances, then alternatives

such as moving the structure or a deep foundation as described above should be employed.

Foundation recommendations for structures supported by sandstone bedrock and controlled fill

are presented below.

3.1 Pump House Foundation

Foundations should be constructed on undisturbed, controlled fill. We believe that 3 to 13 feet

of fill (northwest to southeast building corners) would likely result in differential settlement of the

purnp house. For a differential fill depth of 10 feet, we would estimate differential settlernents on

the order of 1 to 2 inches (or about 2 to 3 inches of total movement). Settlement is discussed in

more detail in section 2.3. Loose, disturbed soils encountered at foundation level should be

removed and the foundation should be extended to undisturbed controlled fill and/or natural

soils.

1. Foundations can be designed for a maximum allowable soil pressure of 3,000 psf.

2. Resistance to sliding at the bottom of the mat foundation can be calculated based on a coefficient of friction of 0.35. Passive pressure against the side of the footing can also

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be considered for the sliding resistance if it is properly compacted. Passive pressure can be estimated based on an equivalent fluid density of 350 pcf for a level backfill.

3. The soils below foundations should be protected from freezing. We recommend the bottom of foundations be constructed at least 3.5 feet below finished exterior grade or as required by local municipal code.

4. All foundation excavations should be observed by a representative of the geotechnical engineer prior to placement of concrete.

3.2 Treatment Area and Storage Tank Foundations

Foundations should be constructed on undisturbed, sandstone bedrock. Loose, disturbed

bedrock encountered at foundation level should be removed and the foundation should be

extended to undisturbed bedrock.

1. Foundations can be deSigned for a maximum allowable soil pressure of 4,000 psf.

2. Resistance to sliding at the bottom of the mat foundation can be calculated based on a coefficient of friction of 0.40. Passive pressure against the side of the footing can also be considered for the sliding resistance if it is properly compacted. Passive pressure can be estimated based on an equivalent fluid density of 350 pcf for a level backfill.

3. The soils below foundations should be protected from freezing. We recommend the bottom of foundations be constructed at least 3.5 feet below finished exterior grade or as required by local municipal code.

4. All foundation excavations should be observed by a representative of the geotechnical engineer prior to placement of concrete.

4.0 SEISMIC CONSIDERATIONS

Based upon the nature of the sUbsurface materials, a Site Class C, should be used for the

design of the structures for the proposed project (2006 International Building Code, Table No.

1613.5.3 (1) and (2)). The project site is located in seismic area with a mapped maximum short

period (85) and 1-second period (8,) ground motion, respectively, of 0.28g and 0.068g as

indicated on Figures 1613.5 (1) and (2), in the 2006 International Building Code. The site

coefficients, Fa and Fv, for the same periods are 1.2 and 1.7, respectively.

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5.0 CONCRETE AND CORROSIVITY

The concentration of water-soluble sulfate measured in the laboratory on a shallow sample (test

hole TH-9 at 2 feet) was 0.006 percent. This concentration of water-soluble sulfate represents a

negligiblellow (Class 0 exposure) degree of sulfate attack on concrete exposed to this material.

The degree of attack is based on a range of 0.00 to less than 0.10 percent as presented in the

American Concrete Institute Guide to Durable Concrete. Due to the negligiblellow degree

indicated by the test results. no special requirements for concrete are necessary for Class 0

exposure.

6.0 LIMITATIONS

This study was conducted in accordance with generally accepted geotechnical engineering

practices in this area for use by the client for design purposes. The conclusions and

recommendations submitted in this report are based upon the data obtained from exploratory

test holes, field reconnaissance and anticipated construction. The nature and extent of

subsurface variations across the site may not become evident until excavation is performed. If

during construction, conditions appear to be different from those described herein; this office

should be advised at once so reevaluation of the recommendations may be made. We

recommend on-site observation of excavations by a representative of the geotechnical

engineer.

The scope of services for this project did not include, specifically or by implication, any

environmental or biological (e.g., mold, fungi, and bacteria) assessment of the site or

identification or prevention of pollutants, hazardous materials or conditions or biological

conditions. If the owner is concerned about the potential for such contamination, conditions or

pollution, other studies should be undertaken.

The report was prepared in substantial accordance with the generally accepted standards of

practice for geotechnical engineering as exist in the site area at the time of our investigation.

No warranties, express or implied, are intended or made.

Respectfully Submitted:

YEH AND ASSOCIATES, INC.

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Divide Road Water Facility

Keith E. Asay Staff Engineer

8

Reviewed by:

Richard D. Johnson, P.E. Project Manager

Project No. 212-011

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I~ Yeh and Associates, Inc. Consulting Engineers & Scientists

DRAIJN BY, SV

CHECKED BY' RDJ DESIGNED FOR, E.-.o:o.no Oil 8. Go. 5, USA

PROJECT NUMBER, 2 12-011

SCALE

HOR!Z, NOT TO SCALE VERT,

DATE,3/1/2012

DATE,3/112012

NOT TO SCALE

PROJECT,

Topographic maps created with TOPOI®O National Geographic

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Divide Road Water Facility

Approximate Site Location

FIGURE

~ BORE HOL E LUCA I IUN

~

NOTE 1 BORING LOCAT IONS ~ERE Nor SURVlYlO AND AR E AP PROXIMA TE 2: DRAI,./!NG BASED ON P LAN s r I DA Tro ,JANUARY 2 8. 2 012, PROVID ED BY ENCANA DIL 8-GAS

I~ jO<!:CKED

~r. ..... [ Yeh and Associates. Inc. >OIll

""rs & Scientists Consulting EngiL ~ "'y[~T ~

Divide Road Water Faci lity

Approximate Test Hole Locations

,,~

2

N

~ to " a ~

i<

" 00 g .0 q N ;; W N

TH~ TH~ 8 286 Treatment ~'j'ea'GO"d"91R!tl~iQrage Tank Trea'~eot Area'~~L' !'1 Elida 8 286 , I evatlOn: , TH-4 leval1on: . I '

8,284'

8,282' TH-1

Ttatment ArealOff-load Tank 8,280 " .~I.~~~I.i0.1:. ~?!.~·9.~ ....

8,278 1 •.

TH-2 Treatment Area/Off-Load Tank

o ~.I~?~i.~: . . ~2??.q.~.

8,276

1" . ~ ~ Proposed Elevalion~751: : : I ~8,274 o ~ a; 8,272',

ill 50/5

8,270

8,2681 ........ L: .... J ... ,J. 5011_5

5011,5

8,266 1 .,"

8,264"

8,262"

50/1.5

5011.5

Treatment Area/Fresh Water Tank-DAF Unit Bldg. Eleval\on: 8283.5 ft

Proposed Elevalion=8279 ft.

" .. \. 5012··

2QJbounce

-50f1· .

Proposed Elev.ation=8278_5 ft ..TtI,6 ..

Traatment Area/Between MeC & Pump House Elevation: 8276.0ft

80~

5012.5

'8,284

"8,282

'8,280

"8,278

,'8,276

"8,274

'8,272

'8,270

,'8,268

"'8,266

"'8,264

"8,262

8,2601· . . . .... 18,260

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

~I'~ i JI Project Number: 212-011 Figure 3 Ii'

YEH AND ASSOCIATES, INC. GEOTECHNICAL ENGINEERING CONSULTANTS

Divide Road Water Facility Upper Pad-Treatment Area

N

~ S ~ ~

'" " u;

§ -' ;;; N

N w

.. IH,7.. . ............. ....... . ....... ... .. .. Tank 8,2801' Futur8,&!'rme.O ft

Eleva ..... .. TH-9 St~geTankO f't TH-10

ElevatlOO: 8274. , SJ~.TMk. .... .. ..........• .. " .. TH-8 .... ... .... ... . ... ... . ..... "i:i8vation: 82n.O ft I ~ ~: .. .. .... ... ElevatJOO: 8272.01\ ) ~: sn5 ..... •. . _ .

' . .> . '''12 .'--' 1 ~ ,~""j;""""" roo' ..

::: .~ ': .. ... . . . .......... .. ........... ;: . . TH-11 0."" , . 1m ~. ~ , __ • : : : 5014 . .. : : : 15 5't><ag.r",

8,2651 ' ...... I· :' 1" ............ 1"':·:1 .. ·· .... .. ·· .. .. · ........ 1:·:·:1 .................... .. ........ ...... 1:·"1 .................... ·.... Pl _8,2601 1 ~ 5OI4 1 ~ 5OIJ II P="E""ti~'''' l ~ so/1 M E .. .

2O.<>ouoea 50IJ

c o ~ 8,255 . L.:..: ~!2 .

5O~ ~"'" L.:...: I....:....:.... W 9 50Q 5014 L

8,250' " ............. .

8,2451•• • •• • •••••• •• • • • • • . .............. . ... ....... .

. .......... 18,280

.......... 18.275

S,270

"S,265

" 8,260

" 8,255

" S,250

" 8,245

8,240' " ...... ... . . . ..... . .. ····· ·· ··· ·· .. ····· .. ·· .. ··8,240

8,2351 .• .•..•• .. • ... • .•..•..••.••• . • •..•..•.. • ..••.••..••..•..•..•• ..•.. . • .•...•..•••• ············ · ··········· ·· ·· · ·~m

8,2301" ............. .......... ..... . .... ....... .. ...... .............. ..... ..... ...... .. .. .. ................ . .. . .. ....... ..... 18,230

~ <~------------------------,--------------------------J

~ Ig ~L~::~~:::::: ________________________________________________ ~p~rO~je~ct~~N~um~b~e~r:~2~1~2~-0~1~1 ______________________________________ F~ig~u_ffi_4~ ~

YEH AND ASSOCIATES, INC. GEOTECHNICAL ENGINEERING CONSULTANTS

Divide Road Water Facility Lower Pad-Storage Tanks

l ,jYEH AND ASSOCIATES, INC. Project: Divide Road Water Facility .41 GEOTECHNICAL ENGINEERING CONSULTANTS Project Number: 212·011

Legend for Symbols Used on Test Hole Logs

Sample Types

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D

• Bulk sample was obtained from auger cuttings at the depths indicated.

Modified California Sampler. The symbol 29/12 indicates that 29 blows from a 140 pound hammer falling 30 inches was used to drive 2~inch I.D. sampler 12 inches .

Split Spoon Sampler. The symbol 50/1.5 indicates that 50 blows from a 140 pound hammer falling 30 inches was used to drive 1.5-inch 1.0. sampler 1.5 inches.

Soil Lithology

Topsoil, brown, dark brown.

Sand, silty, clayey, loose, slightly moist to moist, brown (8M).

Bedrock Lithology

~ Weathered sandstone bedrock, medium hard, slightly moist, white, light brown, rust.

[J. : :: Sandstone bedrock, occasionally cemented, hard to very hard, slightly moist, white, light brown, rust.

NOTES: 1. Test holes were drilled on February 14 and 15,2012 with 4-inch continuous flight auger. 2. Groundwater was not encountered. 3. Test hole descriptions are subject to explanations contained in this report. 4. Elevations were estimated from topography by others.

Figure 5

,

Sieve Analysis Hydrometer Analysis

Sieve Opening in Inches I U.S. Standard Sieves Size of Particles in mm

12" 6" 3" 2" ' " 314" 1/2" 318" 4 8 10 16 3040 50 100 200 Sieve %

100 Size Passing

3" "

90 2 '12" -

I

80 I 2" -

70 I 1 '12" -t- - - ~ 1= ~ l=- I-~

.-r- ==-- 1-~ I- - I--

1" -Cl 60 I

c: "iii %" -II) I

"' I I Q. 50 - r Y2" -c:

'" " ~ 40 '" %" 100 Q. I

30 I- f--1- - - f- l- t--- l- f-IV I - t- - #4 100

20 #10 91 r

#40 64 10 I

I I

I #200 12

0 100 10 1 0.1 0.01

Particle Size (mm)

Gravel (%) 0 LL NL Project Name: Divide Road Water Facility

I~ Yeh & Associates! Inc. Geotechnical Engineering Consultants

Sand (%) 88 PL NP Sample 10: TH-6

Sample SIEVE ANALYSIS

Fines (%) 12 PI NP 2 Depth (ft.): Drawn By: MA Project No. : 212-011

Sample Checked By: KA Description:

Sandstone Bedrock Date: Figure No.: 6

Revised 04/2712004

Sieve Analysis Hydrometer Analysis

Sieve Opening in Inches I U.S. Standard Sieves Size of Particles in mm

,,- 6" 3" ,- 1" 314" '/2" ,.,. 4 • '0 ,. 30 40 50 '00 200

Sieve % Size Passing

100 3" -

90 2 'h" -

80 2" -

70 1 'h" -1" -

'" 60 c I I ·iii %" -<II I IV I I n. 50 - I I %" -C I .,

<.J ~ 40 .,

%" 100 n.

30 #4 92

20 #10 75

#40 60 10

#200 37 0

100 10 1 0.1 0.01 Particle Size (mm)

Gravel (%) 8 LL NL Project Name: Divide Road Water Faci lity

I~ Yeh & Associates! Inc. Geotechnical Eng ineering Consultants

Sand (%) 55 PL NP SamplelD: TH-9

Sample SIEVE ANALYSIS

Fines (%) 37 PI NP 2 Depth (ft.): Drawn By: MA Project No.: 212-011

Sample Checked By: KA Description:

Weathered Sandstone Bedrock Date: Figure No. : 7

Revised 04/27/2004

.~ YEH & ASSOCIATES, INC

Summary of Laboratory Test Results

Project No· 212-011

Sample Location Moisture

Sample Content Test Hole Depth (It) Type (%)

TH-6 2 CA 7.5

TH-9 2 CA 13.0

CA - Indicates Modified California Sampler NL - Indicates non-liquid NP - Indicates non-plastic

Dry Density (pc!)

98

Project Name: Divide Road Water Facility

Grain Size Analysis Atterberg Limits Water Gravel

Sand Fines Soluble

>#4 (%)

<#200 LL PL PI Sulfate (%) (%) (%)

0 88 12 NL NP NP

8 55 37 NL NP NP 0.006

Page 1 of 1

Soil Description

Sandstone Bedrock

Weathered Sandstone Bedrock

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geotechnical investigation · divide road water …...1.0 project information 1.1 purpose and scope...

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