HomeMy WebLinkAbout20122894.tiff Geotechnical Engineering Report
Bear Tracker - Angus Compressor Station
Southwest of County Roads 71 and 130
Weld County, Colorado
May 18, 2012
Terracon Project No. 21125016
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Prepared for:
GWD Engineering, Inc.
Denver, Colorado
Prepared by:
Terracon Consultants, Inc.
1289 15t Avenue
Greeley, Colorado 80631
Phone: 970-351-0460
Fax 970-353-8639
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Geotechnical • Environmental • Construction Materials • Facilities
May 18, 2012 !elJ! ra a
GWD Engineering, Inc.
621 17th Street
Suite 1200
Denver, Colorado 80293
Attn: Ms. Jennifer A. Robertson
Senior Project Controls Engineer/ Procurement Specialist
•
•
Re: Geotechnical Engineering Report
Bear Tracker-Angus Compressor Station
Southwest of County Roads 71 and 130, Weld County, Colorado
Terracon Project No. 21125016
Dear Ms. Robertson:
Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for
the project referenced above. These services were performed in general accordance with our
proposal number P21120042 and agreement dated April 17. 2012. This geotechnical
engineering report presents the results of the subsurface exploration and provides geotechnical
recommendations concerning earthwork and the design and construction of foundations, floor
slabs, and roadways for the proposed project.
We appreciate the opportunity to be of service to you on this project. If you have any questions
concerning this report, or if we may be of further service, please contact us.
Sincerely,
Terracon Consultants, In,
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Jason Mapes, P.E. Eric Bernhardt, P.E.
Geotechnical Engineer Geotechnical Department Manager
Copies To: Addressee (1 via email)
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TABLE OF CONTENTS
Page
Executive Summary
1.0 INTRODUCTION 1
2.0 PROJECT INFORMATION 1
2.1 Project Description 1
2.2 Site Location and Description 2
3.0 SUBSURFACE CONDITIONS 2
3.1 Typical Subsurface Profile 2
3.2 Groundwater 3
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 3
4.1 Geotechnical Considerations 3
4.1.1 Very Loose Foundation Bearing Soils 3
4.1.2 Structural Recommendations 3
4.2 Earthwork 4
4.2.1 Site Preparation 4
4.2.2 Excavation and Dewatering 4
4.2.3 Import Material Specifications 5
4.2.4 Fill Materials and Placement 6
4.2.5 Compaction Requirements 6
4.2.6 Grading and Drainage 7
4.2.7 Exterior Slab Design and Construction 7
4.2.8 Corrosion Protection 7
4.3 Foundations 8
4.3.1 Design Recommendations—Spread Footings 8
4.3.2 Design Recommendations—Reinforced Mat Foundations 9
4.3.3 Construction Considerations—Shallow Foundations 9
4.4 Seismic Considerations 10
4.5 Floor Systems 10
4.5.1 Design Recommendations 10
4.6 Roadway and Parking Lot Design and Construction 11
4.6.1 Compliance 12
4.6.2 Roadway and Pavement Performance 12
4.6.3 Construction Considerations 12
5.0 GENERAL COMMENTS 13
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TABLE OF CONTENTS (cont'd)
APPENDIX A— FIELD EXPLORATION
Exhibit A-1 Field Exploration Description
Exhibit A-2 Boring Location Diagram
Exhibits A-3 to A-5 Boring Logs
APPENDIX B- LABORATORY TESTING
Exhibit B-1 Laboratory Testing
Exhibits B-2 to B-4 Laboratory Testing Results
Appendix C —SUPPORTING DOCUMENTS
Exhibit C-1 General Notes
Exhibit C-2 Unified Soil Classification
Exhibit C-3 Rock Classification
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EXECUTIVE SUMMARY
A geotechnical investigation has been performed for a proposed compressor station to be
constructed southwest of County Roads 71 and 130 in Weld County, Colorado. Three (3) test
borings, presented as Exhibits A-3 to A-5, were performed to depths of approximately 20 to 30'/:
feet below the existing ground surface. This report specifically addresses the recommendations for
the proposed foundations, slabs, and roadways.
Based on the information obtained from our subsurface exploration, the site can be developed for
the proposed project. The following geotechnical considerations were identified:
o The compressor units, slug catcher, and other ancillary equipment may be supported on
shallow foundations consisting of thickened slabs with turned down edges, reinforced
mat foundations, or spread footing foundations bearing on a minimum of two (2) feet of
moisture conditioned and compacted soils.
o Gravel-surfaced roadways may be constructed on 12-inches of scarified, moisture
conditioned, compacted native soils.
o On-site native soils typically appear suitable for use as general engineered fill beneath
foundations and slabs on the project.
o The 2009 International Building Code, Table 1613.5.2 IBC seismic site classification for
this site is D.
o Close monitoring of the construction operations discussed herein will be critical in
achieving the design subgrade support. We therefore recommend that Terracon be
retained to monitor this portion of the work.
o This summary should be used in conjunction with the entire report for design purposes.
It should be recognized that details were not included or fully developed in this section, and
the report must be read in its entirety for a comprehensive understanding of the items
contained herein. The section titled GENERAL COMMENTS should be read for an
understanding of the report limitations.
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GEOTECHNICAL ENGINEERING REPORT
Bear Tracker - Angus Compressor Station
Southwest of County Roads 71 and 130
Weld County, Colorado
Terracon Project No. 21125016
May 18, 2012
1.0 INTRODUCTION
This report presents the results of our geotechnical engineering services performed for the
proposed Bear Tracker Facility to be located southwest of County Roads 71 and 130 in Weld
County, Colorado. The purpose of these services is to provide information and geotechnical
engineering recommendations relative to:
® Subsurface soil and bedrock conditions a Foundation design and construction
® Groundwater conditions m Floor system design
m Grading and drainage ® Roadway design and construction
m Lateral earth pressures ® Earthwork
® Seismic considerations
Our geotechnical engineering scope of work for this project included the advancement of three
(3)test borings to depths ranging from approximately 20 to 30'h feet below existing site grades,
laboratory testing for soil engineering properties and engineering analyses to provide
foundation, slab, and roadway design and construction recommendations.
Logs of the borings along with a Boring Location Diagram (Exhibit A-2)are included in Appendix
A of this report. The results of the laboratory testing performed on soil and bedrock samples
obtained from the site during the field exploration are included in Appendix B of this report.
2.0 PROJECT INFORMATION
2.1 Project Description
Item Description
Site layout Refer to the Boring Location Diagram(Exhibit A-2 in Appendix A)
We understand the site will be developed with up to 3 compressor
Structures units, a slug catcher,water tank, access roads, and other ancillary
equipment.
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May 18, 2012 a Terracon Project No.21125016
Item Description
The structures will be supported on shallow foundations consisting
Building construction of thickened slabs with turned down edges, reinforced mat
foundations, and spread footings.
Compressors: 78 kips
Maximum loads
Other equipment: Unknown
Maximum allowable settlement 1-inch(assumed)
Grading Cuts and/or fills of 3 feet or less are anticipated.
Basement level None
Traffic loading Truck traffic: 12 trucks per day(assumed)
2.2 Site Location and Description
Item Description
Location Southwest of County Roads 71 and 130 in Weld County, Colorado.
North:Agricultural property
East:Weld County Road 71 followed by agricultural property
West:Agricultural property and a battery of storage tanks with a
Surrounding developments
well pump
South: Agricultural property with an access road to the battery of
storage tanks
Current ground cover Native grasses and weeds
Existing topography Relatively flat sloping gently down towards the south and east
3.0 SUBSURFACE CONDITIONS
3.1 Typical Subsurface Profile
Specific conditions encountered at each boring location are indicated on the individual boring
logs included in Appendix A of this report. Stratification boundaries on the boring logs represent
the approximate location of changes in soil types; in-situ, the transition between materials may
be gradual. Based on the results of the borings, subsurface conditions on the project site can
be generalized as follows:
Material Description Approximate Depth of Bottom Consistency/Density/Hardness
of Stratum(feet)
Vegetative layer/topsoil 0.75 -
Silty sand About 5 to 9 feet below existing Very loose to loose
site grades.
About 20 to 24 feet below existing
Silty sand with gravel Medium dense to very dense
site grades.
Siltstone Maximum depth of exploration Firm to hard
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3.2 Groundwater
The borings were observed while drilling for the presence and level of
groundwater. Groundwater was not encountered within the borings at the time of drilling. The
borings were immediately backfilled with auger cuttings following the completion of drilling
operations; therefore, subsequent groundwater measurements were not obtained.
These observations represent groundwater conditions at the time of the field exploration, and
may not be indicative of other times or at other locations. Groundwater levels can be expected
to fluctuate with varying seasonal and weather conditions, and other factors.
Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff
and other factors not evident at the time the borings were performed. Therefore, groundwater
levels during construction or at other times in the life of the structure may be higher or lower
than the levels indicated on the boring logs. The possibility of groundwater level fluctuations
should be considered when developing the design and construction plans for the project.
4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION
4.1 Geotechnical Considerations
4.1.1 Very Loose Foundation Bearing Soils
Very loose to loose silty sand was encountered in our borings completed at this site at
anticipated foundation and slab depths. Terracon believes there is a risk for potential settlement
of foundations and floor slabs constructed directly on this material.
Based on information from the geotechnical engineering analysis and subsurface exploration, it
is our opinion that the shallow foundations and floor slabs should be supported on at least 2 feet
of engineered fill.
4.1.2 Structural Recommendations
Based on information from the geotechnical engineering analyses, subsurface exploration, and
laboratory testing results, it is our opinion the proposed structures can be supported by shallow
foundations consisting of mat foundations or spread footings bearing on a minimum of 2 feet of
properly prepared engineered fill as described in the 4.2 Earthwork section of this report.
Slabs-on-grade may be utilized for the interior floor system of the building, provided they are
constructed in a minimum of 2 feet of properly prepared engineered fill.
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Bear Tracker—Angus Compressor Station a Weld County,Colorado
May 18,2012 a Terracon Project No.21125016
Design and construction recommendations for foundation systems, slabs, roadways, and other
earth related phases of the project are described below.
4.2 Earthwork
The following presents recommendations for site preparation, excavation, subgrade preparation
and placement of engineered fills on the project. The recommendations presented for design
and construction of earth supported elements including foundations and slabs are contingent
upon following the recommendations presented in this section.
Earthwork on the project should be observed and evaluated by Terracon. The evaluation of
earthwork should include observation and testing of engineered fill, subgrade preparation,
foundation bearing soils, and other geotechnical conditions exposed during the construction of
the project.
4.2.1 Site Preparation
Strip and remove existing vegetation, the recommended depth of over-excavation and any other
deleterious materials from the proposed areas of construction. Stripped materials consisting of
vegetation and organic materials should be wasted from the site, or used to revegetate
landscaped areas after completion of grading operations. All exposed surfaces should be free of
mounds and depressions which could prevent uniform compaction.
4.2.2 Excavation and Dewatering
It is anticipated that excavations for the proposed construction can be accomplished with
conventional earthmoving equipment.
In order to reduce potential movements of slab-on-grade floor systems and shallow foundations at
this site, Terracon recommends over-excavation to a depth of at least 2 feet below the bottom of
the floor slabs and shallow foundations and replacement with moisture conditioned, compacted
engineered fill. Prior to placement of over-excavation backfill, the base of the over-excavation
should be scarified, moisture conditioned, and compacted as described in the 4.2.4 Subgrade
Preparation section of this report.
The soils to be penetrated by the proposed excavations may vary significantly across the site.
The soil classifications are based solely on the materials encountered in widely spaced
exploratory test borings. The contractor should verify that similar conditions exist throughout the
proposed area of excavation. If different subsurface conditions are encountered at the time of
construction,the actual conditions should be evaluated to determine any excavation modifications
necessary to maintain safe conditions.
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May 18,2012 m Terracon Project No.21125016
Although evidence of fills or underground facilities such as septic tanks, vaults, basements, and
utilities was not observed during the site reconnaissance, such features could be encountered
during construction. If unexpected fills or underground facilities are encountered, such features
should be removed and the excavation thoroughly cleaned prior to backfill placement and/or
construction.
Depending upon depth of excavation and seasonal conditions, surface water infiltration may be
encountered in excavations on the site. It is anticipated that pumping from sumps may be utilized
to control water within excavations.
The subgrade soil conditions should be evaluated during the excavation process and the stability
of the soils determined at that time by the contractors' Competent Person. Slope inclinations
flatter than the OSHA maximum values may have to be used. The individual contractor(s) should
be made responsible for designing and constructing stable, temporary excavations as required to
maintain stability of both the excavation sides and bottom. All excavations should be sloped or
shored in the interest of safety following local, and federal regulations, including current OSHA
excavation and trench safety standards. If any excavation, including a utility trench, is extended to
a depth of more than 20 feet, it will be necessary to have the side slopes and/or shoring system
designed by a professional engineer.
As a safety measure, it is recommended that all vehicles and soil piles be kept to a minimum
lateral distance from the crest of the slope equal to no less than the slope height. The exposed
slope face should be protected against the elements.
The stability of the subgrade may be affected by precipitation, repetitive construction traffic or
other factors. If unstable conditions develop, workability may be improved by scarifying and
drying. Alternatively, over-excavation of wet zones and replacement with granular materials
may be used, or crushed gravel and/or rock can be tracked or "crowded" into the unstable
surface soil until a stable working surface is attained.
4.2.3 Import Material Specifications
Clean on-site soils or approved imported materials may be used as fill material. Imported soils
(rf required)should meet the following material property requirements:
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May 18, 2012 m Terracon Project No.21125016
Gradation Percent finer by weight(ASTM C136)
4" 100
No.4 Sieve 50-100
No. 200 Sieve 15-50
Soil Properties Value
Liquid Limit 30 (max)
Plastic Limit 15 (max)
Maximum Expansive Potential (%) Non-expansive'
1. Measured on a sample compacted to approximately 95 percent of the ASTM D698 maximum dry density at
optimum water content. The sample is confined under a 100 psf surcharge and submerged.
4.2.4 Fill Materials and Placement
All exposed areas which will receive fill, once properly cleared, should be scarified to a minimum
depth of 8 inches, moisture conditioned to near optimum moisture content, and compacted to at
least 95 percent of the maximum dry unit weight as determined by ASTM D698 prior to
placement of fill.
The on-site soils or approved granular and low plasticity cohesive imported materials may be used
as fill material. The soil removed from this site that is free of organic or objectionable materials,
as defined by a field technician who is qualified in soil material identification and compaction
procedures, can be re-used as engineered fill.
All fill materials should be inorganic soils free of vegetation, debris, and fragments larger than four
inches in size. Pea gravel or other similar non-cementitious, poorly-graded materials should not
be used as fill or backfill without the prior approval of the geotechnical engineer.
It is noted that if crushed gravel or certain other granular materials are used it may be
appropriate to specify compaction criteria based on a relative density test. Compaction criteria
based on relative density should be evaluated based on a project specific basis.
4.2.5 Compaction Requirements
Engineered fill should be placed and compacted in horizontal lifts, using equipment and
procedures that will produce recommended moisture contents and densities throughout the lift.
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Item Description
Fill lift thickness 8 to 12-inches or less in loose thickness
95% of the maximum dry unit weight as determined by ASTM
Compaction requirements
D698
Moisture content -3 to+3% of the optimum moisture content
1. We recommend engineered fill be tested for moisture content and compaction during
placement. Should the results of the in-place density tests indicate the specified moisture or
compaction limits have not been met, the area represented by the test should be reworked and
retested as required until the specified moisture and compaction requirements are achieved.
2. Import granular and on-site granular soils approved by the geotechnical engineer need only be
moisture conditioned sufficiently to allow compaction to the required criteria.
4.2.6 Grading and Drainage
Positive drainage should be provided away from the structures during construction and
maintained throughout the life of the proposed project. Infiltration of water into utility or foundation
excavations must be prevented during construction. Downspouts, roof drains or scuppers should
discharge into splash blocks or extensions when the ground surface beneath such features is not
protected by exterior slabs. Backfill against footings, exterior walls and in utility trenches should
be well compacted and free of all construction debris to reduce the possibility of moisture
infiltration.
Estimated movements described in this report are based on effective drainage for the life of the
structure and cannot be relied upon if effective drainage is not maintained.
4.2.7 Exterior Slab Design and Construction
Exterior slabs and utilities founded on, or in backfill or the site soils will likely experience some
movement due to the volume change of the material. Potential movement could be reduced by:
• Minimizing moisture increases in the backfill
• Controlling moisture-density during placement of the backfill
• Using designs which allow vertical movement between the exterior features
and adjoining structural elements
® Placing control joints on relatively close centers
4.2.8 Corrosion Protection
Results of water soluble sulfate testing indicate that ASTM Type I or II Portland cement should
be specified for all project concrete on and below grade. Foundation concrete should be
designed for low sulfate exposure in accordance with the provisions of the ACI Design Manual,
Section 318, Chapter 4.
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4.3 Foundations
The structures on the project may be supported by shallow foundations bearing on at least 2 feet of
properly prepared engineered fill. Design recommendations for foundation alternatives are
presented in the following paragraphs.
4.3.1 Design Recommendations—Spread Footings
Description Value
Bearing material Minimum of 2 feet of engineered fill.
Allowable bearing pressure' 2,000 psf
Active, Ka=0.28
Lateral earth pressure coefficients2 Passive, Kp=3.5
At-Rest, Ko=0.44
Coefficient of base friction 0.5
Moist soil unit weight y= 125 pcf
Minimum embedment depth below finished grade 36 inches
Total estimated settlement Up to 1 inch
Estimated differential settlement V2 to V4 of total settlement
1. The design bearing pressure applies to dead loads plus design live load conditions. The design
bearing pressure may be increased by one-third when considering total loads that include wind or
seismic conditions.
2. The lateral earth pressure and sliding coefficients given above are ultimate values and do not
include any factor of safety. The foundation designer should include appropriate factors of safety.
The lateral earth pressure coefficients and sliding coefficient given are based on compacted on-site
sand.
Differential movements may be on the order of one-half to three-quarters of the estimated total
movement. Additional foundation movements could occur if water from any source infiltrates
the foundation soils; therefore, proper drainage should be provided in the final design and
during construction. Footings should be proportioned to reduce differential foundation
movement. Proportioning on the basis of equal total settlement is recommended; however,
proportioning to relative constant dead-load pressure will also reduce differential movement
between adjacent footings. Footings and foundations should be reinforced as necessary to
reduce the potential for distress caused by differential foundation movement.
Exterior footings should be placed a minimum of 36 inches below finished grade for frost
protection. Interior footings within heated areas can be supported a minimum of 12 inches
below finished grade. Finished grade is the lowest adjacent grade for perimeter footings and
floor subgrade level for interior footings.
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4.3.2 Design Recommendations—Reinforced Mat Foundations
Thickened slabs with turned down edges or reinforced mat foundations may be used to support
structures on the site. The turned down edges or the bottom of the reinforced mats should be
constructed at a depth of at least 36 inches below finish grade for frost protection. They should
also be constructed at a depth sufficient to resist overturning moments caused by lateral loads
on the structure.
Description Value
Bearing material Minimum of 2 feet of engineered fill.
Allowable bearing pressure' 1,000 psf
Modulus of subgrade reaction 90 pci
Active, Ka=0.28
Lateral earth pressure coefficients2 Passive, Kp=3.5
At-Rest, Ko=0.44
Coefficient of base friction 0.50
Moist soil unit weight y= 125 pcf
Minimum embedment depth below finished grade 36 inches
Total estimated settlement Up to 1 inch
Estimated differential settlement 1/3 to'/2 of total settlement
1. The design bearing pressure applies to dead loads plus design live load conditions. The design
bearing pressure may be increased by one-third when considering total loads that include wind or
seismic conditions.
2. The lateral earth pressure and sliding coefficients given above are ultimate values and do not
include any factor of safety. The foundation designer should include appropriate factors of safety.
The lateral earth pressure coefficients and sliding coefficient given are based on compacted on-site
sand.
4.3.3 Construction Considerations—Shallow Foundations
Shallow foundation construction should only be considered if some foundation movement can
be tolerated.
Foundation excavations should be observed by the geotechnical engineer. If the soil conditions
encountered differ significantly from those presented in this report, supplemental
recommendations will be required.
Over-excavation for compacted backfill placement below foundations should extend laterally
beyond all edges of the foundations at least 8 inches per foot of over-excavation depth below
foundation base elevation. The over-excavation should then be backfilled up to the footing base
elevation with well-graded granular material placed in lifts of 8 to 12 inches or less in loose
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thickness and compacted to at least 95 percent of the maximum dry unit weight as determined
by ASTM D698.
4.4 Seismic Considerations
Code Used Site Classification
2009 International Building Code(IBC)' D2
1. In general accordance with the 2009 International Building Code, Table 1613.5.2.
2. The 2009 International Building Code (IBC) requires a site soil profile determination extending a
depth of 100 feet for seismic site classification. The current scope requested does not include the
required 100 foot soil profile determination. Borings extended to a maximum depth of approximately
30% feet. Additional exploration to deeper depths could be performed to confirm the conditions
below the current depth of exploration. Alternatively, a geophysical exploration could be utilized in
order to attempt to justify a higher seismic site lass.
4.5 Floor Systems
Slab-on-grade floor systems may be utilized for interior floor systems, provided they are
constructed on a minimum of 2 feet of engineered fill. Some movement of slab-on-grade floors
should be expected. If very little movement can be tolerated, a structurally-supported floor
system should be used.
4.5.1 Design Recommendations
Some differential movement of slab-on-grade floor systems is possible if the moisture content of
the subgrade soils is increased. To reduce potential slab movements, the subgrade soils
should be prepared as described in the 4.2 Earthwork section of this report.
For structural design of concrete slabs-on-grade, a modulus of subgrade reaction of 90 pounds
per cubic inch (pci)may be used for floors supported on compacted engineered fill at the site.
Additional floor slab design and construction recommendations are as follows:
▪ Positive separations and/or isolation joints should be provided between slabs
and all foundations, columns, or utility lines to allow independent movement.
• Control joints should be provided in slabs after concrete placement in
accordance with ACI Design Manual, Section 302.1 R-37 8.3.12 (tooled control
joints are not recommended)to control the location and extent of cracking.
® Interior utility trench backfill placed beneath slabs should be compacted in
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accordance with the recommendations presented in the 4.2 Earthwork
section of this report.
® Floor slabs should not be constructed on frozen subgrade.
® Other design and construction considerations, as outlined in the ACI Design
Manual, Section 302.1R are recommended.
4.6 Roadway and Parking Lot Design and Construction
We understand that roadways and parking lots on this site will be gravel surfaced. Terracon
assumed a maximum of 12 trucks per day at the site for the design of the gravel surfaced
roadways.
Design of the gravel-surfaced access roads for the project has been based on the procedures
outlined in the 1993 Guide for Design of Pavement Structures prepared by the American
Association of State Highway and Transportation Officials (AASHTO).
Based upon AASHTO criteria, Colorado is located within Climatic Region VI of the United
States. This region is characterized as being dry, with hard ground freeze and spring thaw.
The spring thaw condition typically results in saturated or near-saturated subgrade soil moisture
conditions. The AASHTO criteria suggest that these moisture conditions are prevalent for
approximately 12-1/2 percent of the annual moisture variation cycle.
For gravel-surfaced access road design, a base elastic modulus for aggregate base layer of
30,000 psi was utilized along with an allowable depth of rutting of 2.5 inches. Based on the
subsurface conditions encountered at the site and the laboratory test results, it is recommended
that the access road areas be designed using a correlated R-value of 20. Additionally, a design
life of 20 years was used. Based on Figure 4.3, Design Chart for Aggregate-Surfaced Roads
Considering Allowable Rutting, 1993 Guide for Design of Pavement Structures by the American
Association of State Highway and Transportation Officials (AASHTO), the recommended
thickness of the gravel-surfaced road base section was determined to be 12 inches for the main
traffic corridor. Terracon should be notified if any of the assumptions made for the roadway
design are not correct.
We should be contacted to confirm and/or modify the recommendations contained herein if
actual traffic volumes differ from the assumed values shown above.
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May 18,2012 a Terracon Project No.21125016
Recommended Thickness(Inches)
Traffic Area Gravel Portland
Surface Cement Total
Concrete
Automobile parking 5 - 5
Main traffic corridors 12 - 12
Aggregate base course (if used on the site) should consist of a blend of sand and gravel which
meets strict specifications for quality and gradation. Use of materials meeting Colorado
Department of Transportation (CDOT) Class 6 specifications is recommended for base course.
Aggregate base course should be placed in lifts not exceeding 6 inches and compacted to a
minimum of 95 percent of the maximum dry unit weight as determined by ASTM D698.
4.6.1 Compliance
Recommendations for roadway design and construction presented depend upon compliance
with recommended material specifications. To assess compliance, observation and testing
should be performed under the observation of the geotechnical engineer.
4.6.2 Roadway and Pavement Performance
The performance of all roadways and pavements can be enhanced by minimizing excess
moisture which can reach the subgrade materials. The following recommendations should be
considered at minimum:
m Site grading should provide a minimum 2 percent grade onto or away from the
roadways.
Frequent grading will be required to minimize surface rutting of the proposed roadway
and/or pavements.
a Water should not be allowed to pond near the edges of roadways and/or pavements.
a Utility trenches should be compacted to the same criteria as the subgrade soils.
4.6.3 Construction Considerations
Roadways may be constructed on native soils. The subgrade should be scarified to a depth of
12 inches, moisture conditioned, and recompacted. Site grading is generally accomplished
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early in the construction phase. However, as construction proceeds, the subgrade may be
disturbed due to utility excavations, construction traffic, desiccation, or rainfall. As a result, the
subgrade may not be suitable for roadway construction and corrective action will be
required. The subgrade should be carefully evaluated at the time of pavement construction for
signs of disturbance or excessive rutting. If disturbance has occurred, subgrade areas should
be reworked, moisture conditioned, and properly compacted to the recommendations in this
report immediately prior to roadway construction.
We recommend the roadway areas be rough graded and then thoroughly proof rolled with a
loaded tandem axle dump truck prior to final grading and placement of the gravel surfacing
material. Particular attention should be paid to high traffic areas that were rutted and disturbed
earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions
are located should be repaired by removing and replacing the materials with properly
compacted fills. All roadway areas should be moisture conditioned and properly compacted to
the recommendations in this report immediately prior to paving.
5.0 GENERAL COMMENTS
Terracon should be retained to review the final design plans and specifications so comments
can be made regarding interpretation and implementation of our geotechnical recommendations
in the design and specifications. Terracon also should be retained to provide observation and
testing services during grading, excavation, foundation construction and other earth-related
construction phases of the project.
The analysis and recommendations presented in this report are based upon the data obtained
from the borings performed at the indicated locations and from other information discussed in
this report. This report does not reflect variations that may occur between borings, across the
site, or due to the modifying effects of construction or weather. The nature and extent of such
variations may not become evident until during or after construction. If variations appear, we
should be immediately notified so that further evaluation and supplemental recommendations
can be provided.
The scope of services for this project does not include either specifically or by implication any
environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or
prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the
potential for such contamination or pollution, other studies should be undertaken.
This report has been prepared for the exclusive use of our client for specific application to the
project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranties, either express or implied, are intended or made. Site
safety, excavation support, and dewatering requirements are the responsibility of others. In the
event that changes in the nature, design, or location of the project as outlined in this report are
Responsive m Resourceful m Reliable
13
Geotechnical Engineering Report �������s�j�
Bear Tracker—Angus Compressor Station o Weld County, Colorado
May 18,2012 o Terracon Project No.21125016
planned, the conclusions and recommendations contained in this report shall not be considered
valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this
report in writing.
Responsive m Resourceful a Reliable
14
APPENDIX A
FIELD EXPLORATION
Field Exploration Description
The scope of the services performed for this project included site reconnaissance by a
geotechnical engineer, subsurface exploration program and laboratory testing.
Three (3) test borings were performed on May 10, 2012. The borings were advanced to
approximate depths of 20 to 30 feet at the approximate locations shown on the Boring Location
Diagram, Exhibit A-2. The borings were advanced with a truck-mounted drilling rig, utilizing 4-
inch-diameter solid-stem augers.
The borings were located in the field by the client. Ground surface elevations at the boring
locations were provided by the project surveyor. The accuracy of boring locations and elevations
should only be assumed to the level implied by the methods used to determine each.
A lithologic log of each boring was recorded by the geotechnical engineer during the drilling
operation. The logs of borings are presented in Appendix A. Relatively undisturbed samples
were obtained at selected intervals utilizing a standard split-spoon and ring-barrel samplers.
Penetration resistance values were recorded in general accordance with the standard penetration
test (SPT)or similar manner with the ring-barrel. This test consists of driving the sampler into the
ground with a 140-pound hammer free-falling through a distance of 30 inches. The number of
blows required to advance the sampler the final 12 inches, or the interval indicated on the boring
log, is recorded as the penetration resistance value which is recorded or correlated to a standard
penetration resistance value (N-value). The blow count values are indicated on the boring logs at
the respective sample depths. Ring-barrel sample blow counts are not considered N-values.
A CME automatic SPT hammer was used to advance the samplers in the borings performed on
this site. A greater efficiency is typically achieved with the automatic hammer compared to the
conventional safety hammer operated with a cathead and rope. Published correlations between
the SPT values and soil properties are based on the lower efficiency cathead and rope method.
This higher efficiency affects the standard penetration resistance blow count value by increasing
the penetration per hammer blow over what would be obtained using the cathead and rope
method. The effect of the automatic hammer's efficiency has been considered in the interpretation
and analysis of the subsurface information for this report.
The penetration test provides a reasonable indication of the in-place density of sandy type
materials, but only provides an indication of the relative stiffness of cohesive materials since the
blow count in these soils may be affected by the soils moisture content. In addition, considerable
care should be exercised in interpreting the blow counts in gravelly soils, particularly where the
size of the gravel particle exceeds the inside diameter of the sampler.
Responsive u Resourceful GI Reliable
Exhibit A-1
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BORING LOG NO. 1 Page 1 of 1
PROJECT: Angus Compressor Station CLIENT:GWD Engineering,Inc.
SITE: Southwest of County Roads 71 and 130
Weld County,Colorado
O LOCATION See Exhibit A-2 Z ur STRENGTH TEST
Lz O a I-
U c WF 1 w� E W Lo s.-7 Cx Z..
NU '`
I K> 0S n F X W ]1-
0. z ¢� >U
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QN u_ D >i
O Approximate Surface Elev.:5212 3 m0 co m - M y m O
DEPTH ELEVATION , 0
o.8 VEGETATIVE LAYER-9 inches 5211.5
j SILTY SAND —
loose,slightly moist to moist,brown — J\
•
2-2-3 6
N=5
5.0 5207 A 6-5 5 92
°La SAND with GRAVEL 5 — N=11 / —
Df medium dense to very dense,moist,light brown,brown,rust —
o _
'sic —
'04 — �/ 2 1-26-41
aI0 10- - N=67 1
O 01F
ta 4 —
• )o —
2 o
u 18-38 5
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15- N=56
ic
iii- oi C —
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• st _
6-8-10
X
lt o rn 20 - _ N=18 _ 25
o 0• 4` —
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2• DO 24.0 5188 _
z SILTSTONE BEDROCK X 28-39 26
o medium hard,slightly moist,brown 25- N=57
tre& _
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X 12-19-22 32
i 30.5 5181.5 30- N=41
3▪ Boring Terminated at 30.5 Feet
O
2
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re
0
Stratification lines are approximate.In-situ,the transition may be gradual. Hammer Type: Automatic
m Advancement Method: See Exhibit A-1 for description of field procedures. Notes:
is 0'-30.5'4-solid flight auger
o See Appendix B for description of laboratory
3 procedures and additional data.Of any).
- -
i abbreviations,
Abandonment Method: - See Appendix C for explanation of symbols and
N_
Borings backfilled with soil cuttings upon completion.
O
O
WATER LEVEL OBSERVATIONS
Boring Started:5/10/2012 Boring Completed:5/1012012
• Not Encountered lierracon
E
_ Drill Rig:CME-55 Driller:BEN
O ----- 1289 First Avenue
5 Greeley,Colorado Project No.:21125016 Exhibit A-3
BORING LOG NO. 2 Page 1 of 1
PROJECT: Angus Compressor Station CLIENT: GWD Engineering, Inc.
SITE: Southwest of County Roads 71 and 130
Weld County,Colorado
O LOCATION See Exhibit A-2 1n w STRENGTH TEST
-, 0a E
n a Wl- w ow ° R ri i a0 >x
¢� o aw wz = 0 Eel az ow
O Approximate Surface Elev.:5212 3m y LL w 1- O0 H
DEPTH ELEVATION O
...
0.8 VEGETATIVE LAYER-9 inches 5211.5
SILTY SAND —
very loose to loose,slightly moist to moist,brown — _
— - N=9,_.._ ---0 _ 4 104
--_
5 - X 3-1-2
6 N=3
-
i 6.0 5206
SILTY SAND with fntAVFI
°L.
medium dense to very dense,moist,buff —
° 27-38 3
a 4 10 - N=65
5 °( —
O 0 —
uci C
0 i — X 23-30-25
rc ° 15 - N=55 4
I° —
a▪ 0
to 4" —
II,F
✓ 4� -
2 x 120.0 5192 8-13 16
T Boring Terminated at 20 Feet 20 N=21
O
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Stratification lines are approximate.In-situ.the transition may be gradual. Hammer Type: Automatic
a.
to Advancement Method: See Exhibit A-1 for description of field procedures. Notes:
at 0-20 4-solid flight auger
o See Appendix B for description of laboratory
g procedures and additional data.(if any).
See Appendix C for explanation of symbols and
O Abandonment Method:
abbreviations.
N_
6onngs backfilled with soil cuttings upon completion.
O _
o WATER LEVEL OBSERVATIONS
0 — - — Boring Started:5/10/2012 Boring Completed:5/10/2012
Not Encountered
O • n
. Drill Rig:CME-55 Driller:BEN
m
E ---- 1289 First Avenue
x Greeley.Colorado Project No.:21125016 Exhibit A-4
BORING LOG NO. 3 Page 1 of 1
PROJECT: Angus Compressor Station CLIENT:GWD Engineering, Inc.
SITE: Southwest of County Roads 71 and 130
Weld County,Colorado
0 LOCATION See Exhibit A-2 wz IP . STRENGTH TEST
E jF 0 9 a 2 �- i-n
V == Qul FJ E o.o. NF 0 WI JF
Qcr
LL 6 wa p �� m wz = Qr >V.
M1' O QN W4' H E8 K 3z put
0
0 Approximate Surface Elev.:5213.6 3 Q y u-
ro r o ff to 0
DEPTH ELEVATION 0
'� 0.8 VEGETATIVE LAYFR-9 inches 5213
SILTY SAND —
loose,slightly moist to moist,brown —
2-2-2 6
n N=4
X 4-6 4
5 - N=10
I 9.0 5204.5 _
° AILMAtIla silthaiala ) N=24 8
17-12-12
.111 a a( medium dense,slightly moist,buff,brown 10 - _
a o
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a a� —
u co D
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i 03
°u 18-22 -- - --
g Do 15- N=40. ,
w o —
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hs�19.0• 5194.5
`" SS TY SAND X 7-7-10 21
1.3 loose,slightly moist,brown 20 - N=17
o —
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a —
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i- —
24.0 5189.5
z SILTSTONF BEDROCK 19-32 35
o firm to hard,slightly moist,brown 25- N=51 ,
cg
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� 29.7 5184 38-50/3 25
3 Boring Terminated at 29.7 Feet N=88/3 t ----- -----
a
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a
0
i- Stratification lines are approximate.In-situ.the transition may be gradual. Hammer Type: Automatic
i
co Advancement Method: See Exhibit A-1(or description of field procedures. Notes:
Si 7'0'-29. 4-solid flight auger See Appendix B for description of laboratory
procedures and additional data,(if any).
O Abandonment Method: See Appendix C for explanation of symbols and
abbreviations.Borings backfilled with soil cuttings upon completion.
m
0
WATER LEVEL OBSERVATIONS
0 Boring Started:5/102012 Boring Completed:5/102012
a Not Encountered r j..' ;, .,
o c[.�, d I] Drill Rig:CME-55 Driller:BEN
m
w 1289 First Avenue
F Greeley.Colorado Project No.:21125016 Exhibit A-5
APPENDIX B
LABORATORY TESTING
Laboratory Testing
The soil and bedrock samples retrieved during the field exploration were returned to the
laboratory for observation by the project geotechnical engineer. At that time, the field
descriptions were reviewed and an applicable laboratory testing program was formulated to
determine engineering properties of the subsurface materials.
Laboratory tests were conducted on selected soil and bedrock samples. The results of these
tests are presented in Appendix B. The test results were used for the geotechnical engineering
analyses, and the development of foundation and earthwork recommendations. The laboratory
tests were performed in general accordance with applicable locally accepted standards. Soil
samples were classified in general accordance with the Unified Soil Classification System
described in Appendix C.
® Water Content
▪ Grain-Size Distribution
® Plasticity Index
® Water-Soluble Sulfate Content
® Dry Density
Responsive o Resourceful o Reliable Exhibit B-1
ATTERBERG LIMITS RESULTS
ASTM D4318
60
50
P A L
s O
40
Tsz‘ Ot
30
O"
I m t
N 20 • o — - --
E • C>
MH or OH
10
CL-ML ML or OL
0
0 20 40 60 80 100
LIQUID LIMIT
Boring ID Depth LL PL PI Fines USCS Description
• 1 2.0 20 NP 20 32 SM SILTY SAND
m 2 14.0 22 NP 22 14 SM SILTY SAND with GRAVEL
8 • 3 4.0 17 NP 17 25 SM SILTY SAND
0
O
- - -
K -
6
l'1
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rc _.
0
u
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0
re
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to PROJECT: Angus Compressor Station PROJECT NUMBER: 21125016
SITE: Southwest of County Roads 71 and 130 1 r
CLIENT: GWD Engineering,Inc.
Weld County,Colorado
2 1289 First Avenue
Greeley,Colorado EXHIBIT: B-2
GRAIN SIZE DISTRIBUTION
ASTM D422
U.S.SIEVE OPENING IN INCHES I U.S.SIEVE NUMBERS I HYDROMETER
4 2 1 1/2 3 6 10 16 30 50 100 200
6 3 1.5 i 3/4 ip e 4 8 14 20 40 60 i 140
100
90 — \ — —
--85 - h __ \ -
80 '� ---
75
70 \q\ I \ - _
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at
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15 -
i
O
i' 10 __ - _ _ _ -
K
5
a.
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u 0
S 100 10 1 0.1 0.01 0.001
GRAIN SIZE IN MILLIMETERS
D COBBLESr _ _GRAVEL SAND SILT OR CLAY
h coarse I fine 1 coarse I medium I fine -1_
W
1 Specimen Identification USCS Classification LL PL PI Cc Cu
• 1 2.0 SILTY SAND(SM) 20 NP 20
o RI 2 14.0 SILTY SAND with GRAVEL(SM) 22 NP 22
a
it' ♦ 3 4.0 SILTY SAND(SM) 17 NP 17
_
z
O -
2
O
2 Specimen Identification D100 Dm D30 D10 %Gravel %Sand %Silt %Clay
w • 1 2.0 12.5 0.155 0.7 67.2 32.1
m 2 14.0 12.5 2.32 0.421 15.5 63.5 13.8
m • 3 4.0 9.5 0.187 0.084 0.4 74.2 25.4
c —
r
z
co PROJECT: Angus Compressor Station PROJECT NUMBER: 21125016
0lrz SITE: Southwest of County Roads 71 and 130 rr CLIENT: GWD Engineering,Inc.
2 Weld County,Colorado
So 1289 First Avenue
i
Greeley,Colorado EXHIBIT: B-3
r
Summary of Laboratory Results
__ __ Sheet 1 of 1 Water BORING Depth
USCS Classification Compressive Liquid Plastic Plasticity cW2W % % % % Content Density
ID and Soil Description Strength Limit Limit Index Sieve Gravel Sand Slit Clay (%) Urn
1 2-3.5 SILTY SANDISM) 20 NP 20 32.1 0.7 67.2 5.6
1 4-5 5.3 91.9
1 9-10.5 1.3
•
1 14-15 4.5
1 19-20.5 25.1
1 24-25 26.4
1 29-30.5 32.1
2 2-3 4.2 104.5
2 4.5.5 _ - 5.6
2 9-10 2.5
2 14.15.5 SILTY SAND with GRAVEL(SM) 22 NP 22 13.8 15.5 63.5 4.4
2 19-20 16.3
3 2-3.5 5.8
3 4-5 SILTY SAND{SM) 17 NP 17 25.4 0.4 74.2 4.0
3 9-10.5 8.2
3 14-15 8.9
•
3 19-20.5 21.2
3 24-25 34.7
3 29-29.8 25.2
a
0
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5
F
O
PROJECT: Angus Compressor Station PROJECT NUMBER: 21125016
o SITE: Southwest of County Roads 71 and 130 1 r
CLIENT: GWD Engineering,Inc.
EE
Weld County,Colorado
o 1289 First Avenue
Greeley,Colorado EXHIBIT: B-4
r
APPENDIX C
SUPPORTING DOCUMENTS
EXPLANATION OF BORING LOG INFORMATION
DESCRIPTION OF SYMBOLS AND ABBREVIATION
® Z V Water Level Initially (HP) Hand Penetrometer
O Encountered
a
Auger Split Spoon 4 Specified w Water Level After Period of Time (n Torvane
I
I
CL
N Water Level After fl)a Specified Period
of me F (bit) Standard Penetration
N Test(blows per foot)
02
Shelby Tube Macro Core C ,xi No Water Level Observed UI
(PID) Photo-Ionization Detector
a
Water levels indicated on the soil boring 0
Qj logs are the levels measured in the I I
y UI borehole at the times indicated.Water LL (OVA) Organic Vapor Analyzer
No Recovery Rock Core —1 level variations will occur over time.In
lig W low permeability soils,accurate
ivA
FAII Q determination of water levels is not
possible with short term water level
Ring Sampler > observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil classification is based on the Unified Soil Classification System.Coarse Grained Soils have more than 50%of their dry
weight retained on a#200 sieve;their principal descriptors are:boulders,cobbles,gravel or sand.Fine Grained Soils have
less than 50%of their dry weight retained on a#200 sieve;they are principally described as clays if they are plastic,and
silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be
added according to the relative proportions based on grain size.In addition to gradation,coarse-grained soils are defined
on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.
LOCATION AND ELEVATION NOTES
Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device.The accuracy
of such devices is variable.Surface elevation data annotated with+/-indicates that no actual topographical survey was
conducted to confirm the surface elevation. Instead,the surface elevation was approximately determined from topographic
maps of the area.
RELATIVE DENSITY OF COARSE-GRAINED SOILS CONSISTENCY OF FINE-GRAINED SOILS
(More than 50%retained on No.200 sieve.) (50%or more passing the No.200 sieve.)
Density determined by Standard Penetration Resistance Consistency determined by laboratory shear strength testing,field
visual-manual procedures or standard penetration resistance
N Descriptive Term Std.Penetration Resistance Descriptive Term Undrained Shear Strength SW.Penetration Resistance
2 (Density) (blows per foot) (Consistency) (kips per square foot) (blows per foot)
00
LU F Very Loose 0.3 Very Soft less than 0.25 0-1
=r Loose 4-9 Soft 0.25 to 0.50 2-4
Z Medium Dense 10-29 Medium-Stiff 0.50 to 1.00 5-7
W
I—
CO
Dense 30-50 Stiff 1.00 to 200 8-14
Very Dense ≥50 Very Stiff 2.00 to 4.00 15-30
Hard above 4.00 I ≥30
RgI ATIVE PROPORTIONS OF SAND AND GRAVFI GRAIN SIZE TERMINOLOGY
Descriptive Terms) Percent of Descriptive Terms) percent of
of other constituents pry Weight of other constituents Dry Welaht
Trace <15 Boulders Over 12 in.(300 mm)
With 15.29 Cobbles 12 in.to 3 in.(300mm to 75mm)
Modifier >30 Gravel 3 in.to#4 sieve(75mm to 4.75 mm)
Sand #4 to#200 sieve(4.75mm to 0.075mm
Silt or Clay Passing#200 sieve(0.075mm)
RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION
J)escdetive Term(st Percent of Ielm Plasticity Index
of other constituents Pry Weiaht Non-plastic 0
Trace <5 Low 1 -10
With 5-12 Medium 11-30
Modifier ≥12 High ≥30
1 err Exhibit C-1
UNIFIED SOIL CLASSIFICATION SYSTEM
Soli Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Group Group Names
Symbol
Gravels: Clean Gravels: Cu≥4 and 1 ≤Cc≤3E GW Well-graded gravel
More than 50%of Less than 5%fines` Cu<4 and/or 1>Cc>3 E GP Poorly graded gravel r
coarse fraction retained Gravels with Fines: Fines classify as ML or MH GM Silty grevelr�"
Coarse Grained Soils: on No.4 sieve More than 12%Ines` Fines classify as CL or CH GC Clayey gravel`'°"
More than 50%retained
on No.200 sieve Sands: Clean Sands: Cu≥6 and 1s Cc≤3a SW Well-graded sand'
50%or more of coarse Less than 5%fines" Cu<8 and/or 1 >Cc>3 E SP Poorly graded sand'
fraction passes No.4 Sands with Fines: Fines classify as ML or MH SM Silty sand°H1
sieve 'More than 12%fines Fines classify as CL or CH SC Clayey sand°"'
PI>7 and plots on or above"A"lined CL Lean clay K.LM
Inorganic: N.L.M
Slits and Clays: PI<4 or plots below"A"lined ML Silt
-
Liquid limit less than 50 Liquid limit-oven dried Organic day K.LM."
Fine-Grained Soils: Organic: <0.75 OL M.I MD
50%or more passes the Liquid limit-not dried Organic�sLlt
No.200 sieve PI plots on or above"A"line CH Fat day
j Inorganic: KIM
and Clays: PI plots below"A"line MH Elastic Silt
Liquid limit 50 or more Liquid limit-oven dried Organic day"'t'M°
Organic: Liquid limit-not dried <0.75 OH Organic silt"'LM°
Highly organic soils: Primarily organic matter,dark in color,and organic odor PT Peat
A Based on the material passing the 3-inch(75-mm)sieve • "If fines are organic,add"with organic fines"to group name.
°If field sample contained cobbles or boulders,or both,add With cobbles ' If soil contains≥15%gravel,add"with graver to group name.
or boulders,or both"to group name. ' If Atterberg limits plot in shaded area,soil is a CL-ML,silty day.
`Gravels with 5 to 12%fines require dual symbols: GW-GM well-graded " If soil contains 15 to 29%plus No.200,add'with sand"or With gravel,'
gravel with silt,GW-GC well-graded gravel with day,GP-GM poorly whichever is predominant.
graded gravel with silt,GP-GC poorly graded gravel with day. ` If soil contains≥30%plus No.200 predominantly sand,add-sandy'to
°Sands with 5 to 12%fines require dual symbols: SW-SM well-graded group name.
sand with silt,SW-SC well-graded sand with day,SP-SM poorly graded M If soil contains≥30%plus No.200,predominantly gravel,add
sand with silt,SP-SC poorly graded sand with day "gravelly'to group name.
"PI≥4 and plots on or above"A'line.
)2
ECu=DsdD,° Cc= °PI<4 or plots below'A"line.
D10 x D60 'PI plots on or above"K line.
°PI plots below"A"line.
E If soil contains≥15%sand,add"with sand"to group name.
°If fines classify as CL-ML,use dual symbol GC-GM,or SC-SM.
60
For classification of fine-grained •
soils and fine-grained fraction
50 of coarse-grained soils ....ce/ . ..„e
Equation of"A"-line +J 4-
0- Horizontal at P1=4 to LL=25.5.
x 40 then P1=0.73(LL-20) ---- - - -
w •' t0
p Equation of"U"-line `-O
Z Vertical at LL=16 to PI=7,
30 then PI=0.9(LL-8) '
v d''
of
CO Z0 V - • -. -
5 G MH or OH
•
10 _.
- Li
4 -- ML Or OL
0
0 10 16 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT(LL)
lierrecon Exhibit C-2
DESCRIPTION OF ROCK PROPERTIES
WEATHERING
Fresh Rock fresh,crystals bright,few joints may show slight staining. Rock rings under hammer if crystalline.
Very slight Rock generally fresh, joints stained, some joints may show thin clay coatings, crystals in broken face show
bright. Rock rings under hammer if crystalline.
Slight Rock generally fresh,joints stained, and discoloration extends into rock up to 1 in.Joints may contain clay. In
granitoid rocks some occasional feldspar crystals are dull and discolored. Crystalline rocks ring under hammer.
Moderate Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull
and discolored; some show clayey. Rock has dull sound under hammer and shows significant loss of strength
as compared with fresh rock.
Moderately severe All rock except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority
show kaolinization. Rock shows severe loss of strength and can be excavated with geologist's pick.
Severe All rock except quartz discolored or stained. Rock"fabric"clear and evident, but reduced in strength to strong
soil. In granitoid rocks, all feldspars kadinized to some extent. Some fragments of strong rock usually left
Very severe All rock except quartz discolored or stained. Rock"fabric"discernible,but mass effectively reduced to"soil"with
only fragments of strong rock remaining.
Complete Rock reduced to"soil". Rock"fabric"not discernible or discernible only in small,scattered locations. Quartz may
be present as dikes or stringers.
HARDNESS(for engineering description of rock—not to be confused with Moh's scale for minerals)
Very hard Cannot be scratched with knife or sharp pick. Breaking of hand specimens requires several hard blows of
geologist's pick.
Hard Can be scratched with knife or pick only with difficulty. Hard blow of hammer required to detach hand specimen.
Moderately hard Can be scratched with knife or pick. Gouges or grooves to'A in.deep can be excavated by hard blow of point of
a geologist's pick. Hand specimens can be detached by moderate blow.
Medium Can be grooved or gouged 1/16 in. deep by firm pressure on knife or pick point Can be excavated in small
chips to pieces about 1-in.maximum size by hard blows of the point of a geologist's pick.
Soft Can be gouged or grooved readily with knife or pick point. Can be excavated in chips to pieces several inches in
size by moderate blows of a pick point. Small thin pieces can be broken by finger pressure.
Very soft Can be carved with knife. Can be excavated readily with point of pick. Pieces 1-in.or more in thickness can be
broken with finger pressure. Can be scratched readily by fingernail.
Joint,Bedding,and Foliation Spacing in Rock a
Spacing Joints Bedding/Foliation
Less than 2 in. Very close Very thin
2 in.—1 ft. Close Thin
1 ft.-3 ft. Moderately close Medium
3 ft.-10 ft. Wide Thick
More than 10 ft. Very wide Very thick
a. Spacing refers to the distance normal to the places,of the described feature,which am parallel to each other or nearly so.
Rock Quality Designator(RQD)a Joint Openness Descrptors
RQD,as a percentage Diagnostic description Openness Descriptor
Exceeding 90 Excellent No Visible Separation Tight
90—75 Good Less than 1/32 in. Slightly Open
75—50 Fair 1/32 to 1/8 in. Moderately Open
50—25 Poor 1/8 to 3/8 in. Open
Less than 25 Very poor 3/8 in.to 0.1 ft. Moderately Wde
a RID(given as a percentage)=length of core in pieces Greater than 0.1 ft. Wide
4 in.and longer/length of run.
References: American Society of Civil Engineers. Manuals and Reports on Engineering Practice-No. 56.Subsurface Investigation for
Design and Construction of Foundations of Buildings. New York: American Society of Civil Engineers, 1976. U.S.
Department of the Interior,Bureau of Reclamation,Engineering Geology Field Manual.
lierrac h u=; Exhibit C-3
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