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DIVIDLROADMIAtegMOLITY
CARRELS,COUNTY, COLORADO
March 7,, 202
Prepawl For:
Sevin Mcanwe
Encana Olt& Gan (USA), Inc.
370 471h Ctivet,Cmith 1700
DOnver, CO 80202
Prepweg By:
Yolvand Atadat.011, inc.
4,425'01816)4Wilin0
Dionwq00.4ptings, CO8-1801
1:4101.1f 384.1500
Fax 010)4144101.
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
Divide Road Water Facility Project No. 212-011
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 Facility 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:1 V and 4H:1 V.
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 Fomtation 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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Divide Road Water Facility
Project No. 212-011
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 diameter
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 D1586). 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 Togs 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 TI -I-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 Soll Classification System
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11
Divide Road Water Facility Project No. 212-011
(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:1 V to 4H:1 V 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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Divide Road Water Facility Project No. 212-011
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 altemative, 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 recommendations 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 pump 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
assoclated 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
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). 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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Divide Road Water Facility Project No. 212-011
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 a5 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 (Ss) and 1 -second period (51) 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 F, for the same periods are 1.2 and 1.7, respectively.
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Divide Road Water Facility Project No. 212011
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
negligible/low (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 negligible/low 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
Project No. 212-011
Keith E. Asay
Staff Engineer
8
Reviewed by:
Richard D. Johnson, P.E.
Project Manager
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Legend for Symbols Used on Test Hole Logs
Sample Types
® Bulk sample was obtained from auger cuttings at the depths indicated.
n
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 I.D. sampler 1.5 Inches.
Soil Lithology
a; Topsoil, brown, dark brown.
Sand, silty, clayey, loose, slightly moist to moist, brown (SM).
Bedrock Lithology
Weathered sandstone bedrock, medium hard, slightly moist, white, light brown, rust.
Sandstone bedrock, occasionally cemented, hard to very hard, slightly moist, white, light
brawn, 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.
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