B08_Attachment_5_-_Geotechnical_Report_NB155038_Litchfield.pdf

Exhibit 3

Geotechnical Engineering Report

Proposed Litchfield Wild Horse & Burro Administrative Site

725 U.S. Highway 395 Litchfield, California

Terracon

July 23, 2015 Terracon Project No. NB145038

Sacramento, CA

(916) 928-4690

Proposed Litchfield Wild Horse & Burro Administrative Site

725 U.S. Highway 395 Litchfield, California

July 23, 2015 Terracon Project No. NB145038

Prepared for:

Chamberlin Architects

Grand Junction, Colorado

Prepared by:

Terracon Consultants, Inc.

Sacramento, California

Terracon Consul tants, Inc. 50 Goldenland Court , Suite 100 P [916] 928 4690 F [916] 928 4697 terracon.com

July 23, 2015

Chamberlin Architects 437 Main Street Grand Junction, CO 81501

Attn: Mr. Werner Duecker P: (970) 242-6804 F: (970) 685-9630 E: wduecker@chamberlinarchitects.com

Re: Geotechnical Engineering Report Proposed Litchfield Wild Horse & Burro Administrative Site 725 U.S. Highway 395 Litchfield, California 96117 Terracon Project No. NB155038

Dear Mr. Duecker:

Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for the above referenced project. This study was performed in general accordance with our proposal dated December 16, 2014. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of the new structure.

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, Inc.

Ryan R. King, P.E. Patrick C. Dell, G.E.

Professional Engineer 77326 Geotechnical Engineer 2186 Department Manager Senior Associate

Enclosures cc: 1 – Client (PDF) 1 – File

Proposed Litchfield Wild Horse & Burro Administrative Site ■ Litchfield, California July 23, 2015 ■ Terracon Project No. NB155038

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TABLE OF CONTENTS

CONTENTS

EXECUTIVE SUMMARY ............................................................................................................. i

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

Project Description Site Location and Description

3.0 SUBSURFACE CONDITIONS

Geology Typical Profile Groundwater Percolation Testing Faulting and Estimated Ground Motions Liquefaction

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

Geotechnical Considerations Earthwork

4.2.1 Site Preparation

4.2.2 Subgrade Preparation

4.2.3 Fill Material Requirements

4.2.4 Compaction Requirements

4.2.5 Grading and Drainage

4.2.6 Earthwork Construction Considerations

Foundations Floor Slab Seismic Considerations Lateral Earth Pressures Roadway Design Recommendations

4.7.1 Aggregate Surface Roadway Design Recommendations

4.7.2 Compacted Native Soils Access Road Design Recommendations

4.7.3 Pavement and Roadway Design and Construction Considerations

5.0 GENERAL COMMENTS

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TABLE OF CONTENTS (continued)

APPENDIX A – FIELD EXPLORATION

Exhibit A-1 Site Location Exhibit A-2 Exploration Plan Exhibit A-3 Field Exploration Description Exhibit A-4 to A-6 Boring and Percolation Logs

APPENDIX B – LABORATORY TESTING

Exhibit B-1 Laboratory Test Description Exhibit B-2 Grain Size Distribution

APPENDIX C – SUPPORTING DOCUMENTS

Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification

APPENDIX D – PERCOLATION TESTING

Exhibit D-1 & D-2 Percolation Test Sheets

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EXECUTIVE SUMMARY

A geotechnical investigation has been performed for the Proposed Litchfield Wild Horse & Burro Administrative Site to be located at 725 U.S. Highway 395 in Litchfield, California. One (1) geotechnical boring was drilled to an approximate depth of 5 feet below ground surface (bgs) where auger refusal was encountered. Additionally, two (2) percolation borings were drilled to an approximate depth of 3¼ feet bgs. This report provides geotechnical recommendations for the proposed structure.

Based on the information obtained from our subsurface exploration, the site is considered suitable for development of the proposed project provided the geotechnical engineering recommendations included in this report are implemented in the design and construction. The following geotechnical considerations were identified:

n The upper surface materials encountered at the site generally consisted of strongly cemented silty sand with a trace of sub-rounded gravel to a depth of approximately 4 feet bgs underlain by silty sand with gravel extending to the total depth of exploration. Groundwater was not encountered to the maximum depth of our exploration.

n Field and laboratory tests indicate the near surface silty sand soils are suitable for use as engineered fill for this project.

n The proposed building may be supported by spread footings bearing on undisturbed native soils extending to a depth of at least 18 inches below the lowest adjacent finished soil grade.

n The 2013 California Building Code (CBC) Seismic Site Classification for this site is D.

n 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.

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

PROPOSED LITCHFIELD WILD HORSE & BURRO ADMINISTRATIVE SITE

725 U.S. Highway 395

LITCHFIELD, CALIFORNIA 96117

Terracon Project No. NB155038 July 23, 2015

1.0 INTRODUCTION

This report presents the results of our geotechnical engineering services performed for the Proposed Litchfield Wild Horse & Burro Administrative Site to be located at 725 U.S. Highway 395 in Litchfield, California. The Site Location Map (Exhibit A-1) is included in Appendix A of this report. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

n subsurface soil conditions n groundwater conditions n earthwork n foundation design and construction n seismic considerations n floor slab design and construction

Our geotechnical engineering scope of work for this project included the advancement of one (1) geotechnical boring drilled to an approximate depth of 5 feet below the existing ground surface (bgs) where auger refusal was encountered, and two (2) percolation borings drilled to an approximate depth of 3¼ feet bgs.

Logs of the borings along with an Exploration Plan (Exhibit A-2) are included in Appendix A of this report. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included in Appendix B of this report. Descriptions of the field exploration and laboratory testing are included in their respective appendices.

2.0 PROJECT INFORMATION

Project Description Item Description

Site layout See Appendix A, Exhibit A-1 and A-2: Site Location and Exploration Plan.

Structures

We anticipate the proposed structure will consist of one new facility approximately 1,320 square feet in plan area consisting of office space, public restroom, employee restroom, shower/locker room and break room.

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Item Description

Construction

The building will be a single-story, wood framed structure with a concrete slab-on-grade floor, and will be supported on a shallow spread footing foundation system. The development may include at grade gravel parking and drive areas.

Finished Floor Elevation Within one foot of existing grade (assumed).

Maximum loads

■ Maximum Column Loads: 20 kips (assumed)

■ Maximum Wall Loads: less than 2 kips/ft. (assumed)

■ Maximum Floor Loads: less than 100 psf (assumed)

Grading Based on the site topography, cuts and fills on the order of less than one (1) foot are anticipated to provide a level building pad.

Site Location and Description

Item Description

Location The project site is located at 725 U.S. Highway 395 in Litchfield, California.

Existing site features The project site currently consists of the Litchfield Wild Horse and Burro Facility. The immediate area is developed by three structures with scattered automobile and semi-truck parking areas.

Surrounding developments

North: Fenced turn-outs and pastures.

East: On-site structures followed by large pastures South: Vacant land.

West: U.S. Highway 395 followed by vacant land.

Current ground cover The current ground surface consists of sparse vegetation and aggregate road base.

Existing topography Existing topography is relatively flat.

3.0 SUBSURFACE CONDITIONS

Geology

The project area is situated within the Basin and Range Geomorphic Province of California. The native soils underlying the site are considered to be lake deposits (Q l) as described on the Geologic Map of the area1. According to the CGS map, the sediments are mid Quaternary in age (2.6 million years ago and present) and consist of consolidated alluvial sediments (lake deposits) typified by

1 Geologic Map of California: Westwood Sheet: Lydon et all, 1960; scale: 1:250,000) by the California Geological Survey (CGS)

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Typical Profile

Based on the results of the borings and percolation test holes, subsurface conditions on the project site can be generalized as follows:

Stratum Approximate Depth to

Bottom of Stratum Material Description Consistency / Density

1 4 feet Silty Sand Medium Dense to Dense

5 feet

(Maximum Depth of Exploration) Silty Sand with Gravel Very Dense

Conditions encountered at the boring locations are indicated on the individual boring logs.

Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Details for the borings can be found on the boring logs in Appendix A of this report.

Three samples of near surface silty sand were deemed non-plastic and contained 31, 35, and 36 percent silt and clay sized particles passing the U.S. No. 200 sieve, respectively. One sample of silty sand with gravel was deemed non-plastic and contained 19 percent gravel sized particles retained on the No. 4 sieve. Laboratory test sheets are presented in Appendix B of this report.

Groundwater

Groundwater was not observed in the test borings at the time of field exploration. These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times, or at other locations.

Based on the surrounding data reviewed, groundwater level in the project vicinity is approximately 150 feet below the ground surface.2

2 http://www.water.ca.gov/waterdatalibrary/ - Well 403961N1203091W001, located 0.60 miles north of the project site. Measurement taken 3-26-2015

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Percolation Testing

Two (2) percolation borings were advanced at the site to an approximate depth of 3.3 feet bgs.

Soil percolation testing was conducted at these locations on the day they were advanced.

Percolation tests were performed in accordance with Lassen County Environmental Health Department procedures. Percolation test sheets are presented in Appendix D of this report.

Faulting and Estimated Ground Motions

The site is located in Northern California, which is a seismically active area. The type and magnitude of seismic hazards affecting the site are dependent on the distance to causative faults, the intensity, and the magnitude of the seismic event. The table below indicates the distance of the fault zones and the associated maximum credible earthquake that can be produced by nearby seismic events, as calculated using the USGS Earthquake Hazard Program 2008 interactive deaggregations.

Characteristics and Estimated Earthquakes for Regional Faults

Fault Name Approximate Distance to Site (kilometers)

Maximum Considered Earthquake (MCE) Magnitude

Honey Lake Char (Type B Fault) 18.9 6.9 Honey Lake GR (Type B Fault) 20.6 6.7

The mapped Maximum Considered Earthquake (MCE) peak ground acceleration at the subject site is expected to be about 0.428g per the ASCE 7-10 standard with July 2013 errata.

The site is not located within an Alquist-Priolo Earthquake Fault Zone based on our review of the State Fault Hazard Maps.3

Liquefaction

Liquefaction is a mode of ground failure that results from the generation of high pore-water pressures during earthquake ground shaking, causing loss of shear strength. Liquefaction is typically a hazard where loose sandy soils exist below groundwater. The California Geologic Survey (CGS) has designated certain areas within California as potential liquefaction hazard zones. These are areas considered at a risk of liquefaction-related ground failure during a seismic event, based upon mapped surficial deposits and the likely presence of a relatively shallow water table. The project site is not located within a mapped potential liquefaction hazard zone as indicated by the CGS. Based on the absence of groundwater together with the relatively dense

3 California Department of Conservation Division of Mines and Geology (CDMG), “Digital Images of Official Maps of Alquist-Priolo Earthquake Fault Zones of California, Northern Region”, CDMG Compact Disc 2000- 0003, 2000.

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4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

Geotechnical Considerations

Based on the results of the subsurface exploration, laboratory testing, and our analyses we recommend the proposed building be supported on spread footing foundations that bear in undisturbed native soils.

Geotechnical engineering recommendations for foundation systems and other earth connected phases of the project are outlined below. The recommendations contained in this report are based upon the results of field and laboratory testing (which are presented in Appendices A and B), engineering analyses, and our current understanding of the proposed project.

Earthwork

The following presents recommendations for site preparation, excavation, subgrade preparation and placement of structural fills on the project. The recommendations presented are for the design and construction of earth supported elements including foundations and concrete slabs and are contingent upon following the recommendations outlined in this section. All grading for the structure should incorporate the limits of the proposed structure plus a lateral distance of at least two feet beyond the outside perimeter (the building pad).

Earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of structural fill, subgrade preparation, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project. Such evaluation is considered an extension of this study.

4.2.1 Site Preparation

Strip and remove any vegetation and other deleterious materials within the footprint of the proposed construction that might be encountered. This should include the removal of all existing obstructions that may exist within the area of the proposed construction. Exposed surfaces should be free of mounds and depressions which could prevent uniform compaction.

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Due to the presence of nearby pre-existing structures, underground utilities may be present within the proposed construction area. Existing underground facilities and any loose fill soils that might be encountered during construction should be removed from the footprint of the proposed building pad area and the excavations backfilled according to Sections 4.2.3 and 4.2.4 prior to further fill placement and/or construction.

4.2.2 Subgrade Preparation

Foundations may be supported on undisturbed native soils. Floor slabs may be supported on scarified and recompacted native soils. Native soils, once properly cleared, should be scarified, moisture conditioned, and compacted to a minimum depth of 10 inches. The moisture content and compaction of subgrade soils should be maintained until foundation and slab construction.

Any exposed areas which may receive fill, once properly cleared, should be scarified to a minimum depth of 10 inches, moisture conditioned, and compacted per the compaction requirements in Section 4.2.4.

Subgrade soils beneath aggregate roadways or exterior slabs should be scarified, moisture conditioned, and compacted to a minimum depth of 10 inches. The moisture content and compaction of subgrade soils should be maintained until slab or pavement construction.

4.2.3 Fill Material Requirements

All fill materials from any source should be inorganic soils free of vegetation, debris, and fragments larger than three 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.

On-site soils may be used as structural fill for the proposed buildingon-site. Imported soils for use as compacted structural fill material within the proposed building areas should conform to low volume change materials as indicated as follows:

Percent Finer by Weight Gradation (ASTM C 136) 3” No. 4 Sieve ..................................................................................... 50-100 No. 200 Sieve ................................................................................. 20 - 40 n Liquid Limit ....................................................................... 30 (max) n Plasticity Index ................................................................. 12 (max) n Maximum expansive index* .............................................. 20 (max)

*ASTM D 4829

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Structural fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. Fill lifts should not exceed ten inches loose thickness.

4.2.4 Compaction Requirements

Recommended compaction and moisture content criteria for structural fill materials are as follows:

Material Type and Location

Per the Modified Proctor Test (ASTM D 1557)

Minimum Compaction Requirement

Range of Moisture Contents for Compaction Above Optimum Minimum Maximum

Approved import structural fill soils:

Beneath foundations: 90% 0% +4%

Beneath slabs: 90% 0% +4%

Utility trenches (structural areas): 95% 0% +4%

On site Soils:

Bottom of excavation receiving fill: 90% 0% +4%

Miscellaneous backfill: 90% 0% +4%

Utility trenches (Landscape areas): 90% 0% +4%

Beneath asphalt pavements: 95% 0% +2%

Beneath concrete pavements: 95% 0% +2%

Aggregate base (beneath pavements): 95% 0% +2%

4.2.5 Grading and Drainage

All final grades must provide effective drainage away from the building during and after construction. Water permitted to pond next to the building can result in greater soil movements than those discussed in this report. These greater movements can result in unacceptable differential floor slab movements, cracked slabs and walls, and roof leaks. 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.

Exposed ground should be sloped at least 2 percent away from the building extending a minimum of 10 feet beyond the perimeter of the building. After building construction and landscaping, we recommend the Civil Engineer/Surveyor verify final grades to document that effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary, as part of the structure’s maintenance program.

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Planters located within 10 feet of the structure should be self-contained to prevent water accessing the building and pavement subgrade soils. Locate sprinkler mains and spray heads a minimum of 5 feet away from the building line. Collect roof runoff in drains or gutters. Discharge roof drains and downspouts onto pavements which slope away from the building or extend down spouts a minimum of 10 feet away from the structure.

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 or paving. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent to the foundation system should be minimized or eliminated.

4.2.6 Earthwork Construction Considerations

It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The contractor should understand that refusal to boring was encountered approximately 5 feet bgs. Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable. The workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of the floor slab. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become desiccated, saturated, frozen, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and re-compacted prior to floor slab and pavement construction.

The contractor is responsible for designing and constructing stable, temporary excavations (including utility trenches) as required to maintain stability of both the excavation sides and bottom. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards.

The geotechnical engineer should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation;

proof-rolling; placement and compaction of controlled compacted fills; backfilling of excavations to the completed subgrade.

We recommend that the earthwork portion of this project be completed during extended periods of dry weather if possible. If earthwork is completed during the winter/wet and snow seasons (typically November through February) it may be necessary to take extra precautionary measures

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Foundations

The proposed structure can be supported by a spread footing foundation system bearing on undisturbed native soils per Section 4.2. Design recommendations for foundations for the proposed structure and related structural elements are presented in the following subsections.

DESCRIPTION RECOMMENDATION

Foundation Type Conventional Shallow Spread Footings

Bearing Material Undisturbed native soils

Allowable Bearing Pressure 2,000 psf

Minimum Plan View Dimensions Walls: 12 inches; Columns: 24 inches

Minimum Embedment Below Finished Grade 18 inches (Lassen County Minimum Frost Depth)

Total Estimated Settlement 1-inch

Estimated Differential Settlement ¾ inch over 40 feet

Finished grade is defined as the lowest adjacent grade within five feet of the foundations. The allowable foundation bearing pressures apply to dead loads plus design live load conditions. The design bearing pressure may be increased by one-third when considering total loads that include transient conditions, such as wind or seismic. The weight of the foundation concrete below grade may be neglected in dead load computations.

Foundations should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement.

Foundation excavations and bearing soils should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, then supplemental recommendations will be required.

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Floor Slab

Item Description

Floor slab support1 Floor slabs may bear directly on scarified, recompacted native soils.

Aggregate base course/capillary break 4-inches of crushed, washed ¾-inch gravel; or, 6 inches of compacted Aggregate Base (CalTrans Class 2)

Modulus of subgrade reaction 150 pounds per square inch per inch (psi/in) (The modulus was obtained based on our experience with similar subgrade conditions).2

1. Upon completion of grading operations in the building area, the recommended subgrade moisture content and density should be maintained to construction of the building floor slabs.

2. This value is for a small load area (1 sq. ft. or less) such as for forklift wheel loads or point loads and should be adjusted for large loaded areas.

The use of a vapor retarder should be considered beneath concrete slabs-on-grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

In areas of exposed concrete, control joints should be saw-cut into the slab after concrete placement in accordance with ACI Design Manual, Section 302.1R-37 8.3.12 (tooled control joints are not recommended). To control the width of cracking (should it occur), continuous slab reinforcement should be considered in exposed concrete slabs.

Interior trench backfill placed beneath slabs should be compacted in accordance with recommendations outlined in the Earthwork section of this report. Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1R are recommended.

Some differential movement of a slab-on-grade floor system is possible should the moisture content of the subgrade soils vary significantly. Such movements are anticipated to be within general tolerance for normal slab-on-grade construction. To reduce potential slab movements, the subgrade soils should be prepared as outlined in the Earthwork section of this report.

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Seismic Considerations

Code Used Site Classification

2013 California Building Code (CBC)1 D 2

Site Latitude 40.3851° N

Site Longitude -120.3095° W

Ss Spectral Acceleration for a Short Period 0.973g

S1 Spectral Acceleration for a 1-Second Period 0.346g

1. In general accordance with the 2013 California Building Code, Table 1613.5.2.

2. The 2013 California Building Code 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 for this report extended to a maximum depth of approximately 5 feet and this seismic site class assignment considers that dense silty sands continue below the maximum depth of the subsurface exploration. Additional exploration to greater depths could be considered to confirm the conditions below the current depth of exploration. Alternatively, a geophysical exploration could be utilized in order to attempt to justify a more favorable seismic site class.

Lateral Earth Pressures

For on-site native soils and fill materials, or imported granular fill materials above any free water surface, recommended equivalent fluid pressures for foundation elements are:

ITEM On-site & Imported Granular Materials

Active Case 45 psf/ft.

Passive Case 360 psf/ft.

At-Rest Case 60 psf/ft.

Coefficient of Friction 0.35

The lateral earth pressures herein do not include any factor of safety and are not applicable for submerged soils/hydrostatic loading. Additional recommendations may be necessary if such conditions are to be included in the design.

Fill against foundation and retaining walls should be compacted to densities recommended in the Earthwork section of this report. Compaction of each lift adjacent to walls should be accomplished with hand-operated tampers or other lightweight compactors.

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Roadway Design Recommendations

4.7.1 Aggregate Surface Roadway Design Recommendations

Aggregate surface roadway design was conducted in general accordance with the Army Corps of Engineers (ACOE), Technical Manual TM-5-822, Design of Aggregate Surface Roads and Airfields (1990). The design of pavement thickness was based on traffic containing less than 70 vehicles per day with 30 percent trucks, and about 10 percent of the total traffic composed of trucks having three or more axles, and no tracked vehicles. Terracon should be contacted if significant changes in traffic loads or characteristics are anticipated.

As a minimum, the aggregate surface course should have a minimum thickness of 4 inches. The recommended thickness should be measured after full compaction and constructed directly above 10 inches of scarified, moisture conditioned, and compacted native soils. This aggregate road section should be considered suitable for variable weather conditions anticipated at the location of the project with periodic maintenance.

The aggregate surface course should have a plasticity index (PI) between 6 and 12, and conform to specifications of Class II aggregate base in accordance with the California Department of Transportation.

The aggregate surface course should be compacted to a minimum of 95 percent of the soil’s maximum dry density as determined by the ASTM D 1557 test method. Typically, a minimum of 6 inches of loose aggregate surface course will be required to meet the 4-inch minimum constructed thickness. The surface course should be compacted at a moisture content not more than 4 percent above the optimum moisture content determined by the ASTM D 1557 test method.

4.7.2 Compacted Native Soils Access Road Design Recommendations

Based upon the soils conditions encountered in the test borings, the use of on-site soils for construction of on-site roads is considered acceptable. Without the use of asphalt concrete or other hardened material to surface the roadways, there is an increased potential for erosion of the roadway to occur.

If high traffic loading is anticipated during wet seasons or when the upper soils are in saturated conditions, the proposed compacted soils road may experience wheel path rutting and depression up to 3 inches deep.

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Construction of the un-surfaced roadways should consist of a minimum 10-inches of compacted on-site soils. More specifically, the upper ten inches of subgrade soils beneath existing grade, and any fill required to raise site grades should be moisture conditioned and compacted to a minimum density of 95 percent of the maximum dry density as determined by the ASTM D 1557 test method.

4.7.3 Pavement and Roadway Design and Construction Considerations

Regardless of the design, un-surfaced roadways will display varying levels of wear and deterioration. We recommend a system of site inspection at a minimum of once per year to verify the adequacy of the roadways. Preventative measures should be applied as needed for erosion control and regrading. An initial site inspection should be completed approximately three months following construction.

If it is desired to reduce maintenance of the access road, we recommend that the surface of the aggregate base be sealed with asphalt oil as soon as possible after final grading. This is to reduce the potential for moisture to migrate into the aggregate base and to reduce dust from the aggregate base in the dry months. The aggregate base should be sealed every year for the first few years until the aggregate base appears relatively stable and impermeable.

Shoulder build-up on both sides of proposed roadways should match the aggregate surface elevation and slope outwards at a minimum grade of 10 percent for a minimum of five feet.

Materials and construction of pavements for the project should be in accordance with the requirements and specifications of the State of California Department of Transportation, or other approved local governing specifications.

Positive drainage should be provided during construction and maintained throughout the life of the roadways. Proposed roadway design should maintain the integrity of the road and eliminate ponding. The un-surfaced roads are expected to function with periodic maintenance. The owner may want to consider having a stockpile of class 2 aggregate base on site to fill in depressions or rutted areas as they develop rather than wait until failure occurs.

Base course or surfacing materials should not be placed when the surface is wet or frozen.

Surface drainage should be provided away from the edge of roadways to reduce lateral moisture transmission into the subgrade.

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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 expressed 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 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.

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APPENDIX A

FIELD EXPLORATION

T O

P O

G R

A P

H

IC

M A

P I

M A

G E

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July 23, 2015 ■ Terracon Project No. NB155038

Responsive ■ Resourceful ■ Reliable Exhibit A-3

Field Exploration Description

Our field exploration for this project included performing one (1) test boring to an approximate depths of 5 feet bgs and two (2) percolation test borings to approximate depths of 3¼ feet bgs on June 22, 2015. The approximate exploration locations are shown on the Exploration Plan, Exhibit A-2. Exploration locations were located in the field by measuring from the existing site features shown on an aerial photo. The exploration locations should only be considered accurate to the degree implied by the means and methods used to define them.

The test borings were advanced with a truck-mounted CME-55 drill rig which utilized 8-inch diameter hollow-stem auger. A continuous log of the borings was recorded during drilling operations. At selected intervals, samples of the subsurface materials were taken by driving variable sizes of split-spoon samplers. These logs included visual classifications of the materials encountered during drilling as well as the field engineer’s interpretation of the subsurface conditions between samples. Final boring logs included with this report represent the engineer's interpretation of the field logs and include modifications based on laboratory observation and tests of the samples.

Samples of the soils encountered in the borings were obtained using the split barrel sampling procedures described below. The samples were stored in moisture tight containers and transported to our laboratory for further visual classification and testing.

Penetration resistance measurements were obtained by driving the split-spoon and Modified California sampler into the subsurface materials with a 140-pound automatic hammer falling 30 inches. This test is referred to as the standard penetration test (SPT) and displayed on the logs as an “N” value when the standard 2-inch outer diameter sampler is used. The penetration resistance value is a useful index in estimating the consistency or relative density of materials encountered.

The samples were tagged for identification, sealed to reduce moisture loss, and taken to our laboratory for further examination, testing, and classification. Information provided on the borings logs attached to this report includes soil descriptions, consistency evaluations, borings depths, sampling intervals, and groundwater conditions. The borings were backfilled with soil cuttings.

4.0

5.0

SILTY SAND (SM), medium grained, gray to light brown, dense, strong cementation, trace of subrounded gravel

SILTY SAND WITH GRAVEL (SM), medium to coarse grained sand, gray to brown, very dense, strong cementation, subrounded gravel to 2 inches

Auger Refusal at 5 Feet

5-5-50/5" 31

94 NP

NP

Hammer Type: Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 40.3851° Longitude: -120.3089°

G R

A P

H

IC

L O

G See Exhibit A-2

T H

IS

B

O R

IN

G

L O

G

IS

N O

T V

A

LI

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IF

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P A

R A

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G L

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A C

O N

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7/

/1

725 U.S. Highway 395 Litchfield, CA

SITE:

Advancement Method:

8 inch hollow stem auger

Abandonment Method:

Backfilled with soil cuttings upon completion.

50 Goldenland Ct., Ste. 100 Sacramento, California

Notes:

Project No.: NB155038

Drill Rig: CME-55

Boring Started: 6/22/2015

BORING LOG NO. B-1

Chamberlin ArchitectsCLIENT:

Grand Junction, CO

Driller: Andresen

Boring Completed: 6/22/2015

Exhibit: A-4

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

Elevations were provided by Google Earth

PROJECT: Proposed Litchfield Wild Horse & Burro Administrative Site

F

IE

LD

T

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T pc f)

ATTERBERG

LIMITS

LL-PL-PI

Surface Elev.: 4064 (Ft.)

ELEVATION (Ft.)

S A

M P

LE

T

Y P

E

W A

T E

R L

E V

E L

O B

S E

R V

A T

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N

S

D E

P T

H

F t.)

Groundwater not encountered

WATER LEVEL OBSERVATIONS

3.3

SILTY SAND (SM), medium grained, gray to light brown, moderate cementation, trace of subrounded gravel

Boring Terminated at 3.25 Feet

Gravels Encountered at 3 feet below existing grade.

5-7-7 3615 NP

Hammer Type: Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 40.3852° Longitude: -120.3089°

G R

A P

H

IC

L O

G See Exhibit A-2

T H

IS

B

O R

IN

G

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725 U.S. Highway 395 Litchfield, CA

SITE:

Advancement Method:

8 inch hollow stem auger

Abandonment Method:

Backfilled with soil cuttings upon completion.

50 Goldenland Ct., Ste. 100 Sacramento, California

Notes:

Project No.: NB155038

Drill Rig: CME-55

Boring Started: 6/22/2015

BORING LOG NO. P-1

Chamberlin ArchitectsCLIENT:

Grand Junction, CO

Driller: Andresen

Boring Completed: 6/22/2015

Exhibit: A-5

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

Elevations were provided by Google Earth

PROJECT: Proposed Litchfield Wild Horse & Burro Administrative Site

F

IE

LD

T

E S

T R

E S

U

LT

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P E

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ATTERBERG

LIMITS

LL-PL-PI

Surface Elev.: 4066 (Ft.)

ELEVATION (Ft.)

S A

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W A

T E

R L

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S E

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F t.)

3.3

SILTY SAND (SM), medium grained, gray to light brown, moderate cementation, trace of subrounded gravel

Boring Terminated at 3.25 Feet

Gravels Encountered at 3 feet below existing grade.

4-7-7

Hammer Type: Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual.

LOCATION

DEPTH

Latitude: 40.3849° Longitude: -120.3087°

G R

A P

H

IC

L O

G See Exhibit A-2

T H

IS

B

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IN

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/1

725 U.S. Highway 395 Litchfield, CA

SITE:

Advancement Method:

8 inch hollow stem auger

Abandonment Method:

Backfilled with soil cuttings upon completion.

50 Goldenland Ct., Ste. 100 Sacramento, California

Notes:

Project No.: NB155038

Drill Rig: CME-55

Boring Started: 6/22/2015

BORING LOG NO. P-2

Chamberlin ArchitectsCLIENT:

Grand Junction, CO

Driller: Andresen

Boring Completed: 6/22/2015

Exhibit: A-6

See Exhibit A-3 for description of field procedures.

See Appendix B for description of laboratory procedures and additional data (if any).

See Appendix C for explanation of symbols and abbreviations.

Elevations were provided by Google Earth

PROJECT: Proposed Litchfield Wild Horse & Burro Administrative Site

F

IE

LD

T

E S

T R

E S

U

LT

S

P E

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ATTERBERG

LIMITS

LL-PL-PI

Surface Elev.: 4064 (Ft.)

ELEVATION (Ft.)

S A

M P

LE

T

Y P

E

W A

T E

R L

E V

E L

O B

S E

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A T

IO

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S

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F t.)

July 23, 2015 ■ Terracon Project No. NB155038

APPENDIX B

LABORATORY TESTING

July 23, 2015 ■ Terracon Project No. NB155038

Responsive ■ Resourceful ■ Reliable Exhibit B-1

Laboratory Testing

Samples retrieved during the field exploration were taken to the laboratory for further observation by the project geotechnical engineer and were classified in accordance with the Unified Soil Classification System (USCS) described in Appendix C. At that time, the field descriptions were confirmed or modified as necessary and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials.

Laboratory tests were conducted on selected soil samples and the test results are presented on the logs of the borings or in the body of the report. The laboratory test results were used for the geotechnical engineering analyses, and the development of engineering, earthwork, and construction recommendations. Laboratory tests were performed in general accordance with the applicable ASTM, local, or other accepted standards.

Selected soil samples obtained from the site were tested for the following engineering properties:

n In-situ Water Content n Percent Passing the No. 200 Sieve n Unit Weight n Atterberg Limits n Grain Size Analysis

0.0010.010.1110100

% FINES % CLAY USCS

B-1

B-1

P-1

0.0

0.0

0.0

1.0

19.0

0.0

68.0

46.0

64.0

0.198 0.535 0.169

GRAIN SIZE

SILTY SAND(SM)

SILTY SAND with GRAVEL(SM)

SILTY SAND(SM)

16 20

REMARKS

SILT OR CLAYCOBBLES

GRAVEL SAND

medium

31.0

35.0

36.0

GRAIN SIZE IN MILLIMETERS

PERCENT FINER

3/4 1/23/8

SIEVE

(size)

D60

30 403 60

HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS

44 10063 2 fine coarse

SOIL DESCRIPTION

CU

BORING ID

10 14 506 2001.5 81 140 coarse fine

COEFFICIENTS

% COBBLES % GRAVEL % SAND

D30

D10

CC

P E

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% SILT

GRAIN SIZE DISTRIBUTION

ASTM D422

SM

SM

SM

DEPTH (Ft)

2.5

4.5

0.5

50 Goldenland Ct., Ste. 100 Sacramento, California

PROJECT NUMBER: NB155038

PROJECT: Proposed Litchfield Wild Horse &

Burro Administrative Site

SITE: 725 U.S. Highway 395 Litchfield, CA

CLIENT: Chamberlin Architects Grand Junction, CO

EXHIBIT: B-1

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EXHIBIT: B-2

July 23, 2015 ■ Terracon Project No. NB155038

APPENDIX C

SUPPORTING DOCUMENTS

GENERAL NOTES

Exhibit: C-1

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification

Group Symbol Group Name B

Coarse Grained Soils:

More than 50% retained on No. 200 sieve

Gravels:

More than 50% of coarse fraction retained on No. 4 sieve

Clean Gravels:

Less than 5% fines C

Cu 4 and 1 Cc 3 E GW Well-graded gravel F

Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F

Gravels with Fines:

More than 12% fines C

Fines classify as ML or MH GM Silty gravel F,G,H

Fines classify as CL or CH GC Clayey gravel F,G,H

Sands:

50% or more of coarse fraction passes No. 4 sieve

Clean Sands:

Less than 5% fines D

Cu 6 and 1 Cc 3 E SW Well-graded sand I

Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I

Sands with Fines:

More than 12% fines D

Fines classify as ML or MH SM Silty sand G,H,I

Fines classify as CL or CH SC Clayey sand G,H,I

Fine-Grained Soils:

50% or more passes the No. 200 sieve

Silts and Clays:

Liquid limit less than 50

Inorganic:

PI 7 and plots on or above “A” line J CL Lean clay K,L,M

PI 4 or plots below “A” line J ML Silt K,L,M

Organic:

Liquid limit - oven dried

0.75 OL

Organic clay K,L,M,N

Liquid limit - not dried Organic silt K,L,M,O

Silts and Clays:

Liquid limit 50 or more

Inorganic:

PI plots on or above “A” line CH Fat clay K,L,M

PI plots below “A” line MH Elastic Silt K,L,M

Organic:

Liquid limit - oven dried

0.75 OH

Organic clay K,L,M,P

Liquid limit - not dried Organic silt K,L,M,Q

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 B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name.

C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay

E Cu = D60/D10 Cc =

DxD

)(D

F If soil contains 15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H If fines are organic, add “with organic fines” to group name.

I If soil contains 15% gravel, add “with gravel” to group name.

J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant.

L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to group name.

M If soil contains 30% plus No. 200, predominantly gravel, add

“gravelly” to group name.

N PI 4 and plots on or above “A” line.

O PI 4 or plots below “A” line.

P PI plots on or above “A” line.

Q PI plots below “A” line.

Exhibit: C-2

July 23, 2015 ■ Terracon Project No. NB155038

APPENDIX D

PERCOLATION TESTING

rc o la ti o n T e s t R e s u lt s f o r

O J E

C T

A

D D

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