A06_Rosebud_Geotechnical_Final_Rpt.pdf

Prepared for:

Bureau of Land Management

Prepared by:

North Wind Resource Consulting, LLC

May 26, 2015

30130.008-TR-001

Geotechnical Report Rosebud Quarters Building Design Bureau of Land Management West Desert District Salt Lake City, UT ID/UT IDIQ Contract No. L14PC00105

Geotechnical Report

Rosebud Quarters Building Design Bureau of Land Management

West Desert District

May 26, 2015

Prepared for:

Bureau of Land Management

Prepared by:

North Wind Resource Consulting, LLC

1425 Higham Street Idaho Falls, Idaho 83402

Project No. 30130.008

CHANGE MANAGEMENT RECORD

Project No.: 30130.008

Report Number: 30130.008-TR-001

Report Name: Geotechnical Report

Rosebud Quarters Building Design Bureau of Land Management

REVISION

NO. DATE DESCRIPTION OF CHANGES/AFFECTED PAGES

0 May 26, 2015 Base Document

Geotechnical Report v North Wind Resource Consulting, LLC Rosebud Quarters Building Design May 2015

CONTENTS

1. INTRODUCTION ........................................................................................................................... 1-1

1.1 Project Description ............................................................................................................. 1-1

1.2 Purpose and Scope .............................................................................................................. 1-1

1.3 Terms and Conditions / Warranties .................................................................................... 1-2

2. GENERAL DATA .......................................................................................................................... 2-1

2.1 Geologic Setting and Stratigraphy ...................................................................................... 2-1

2.2 General Geology ................................................................................................................. 2-1

2.3 Seismic Design Criteria ...................................................................................................... 2-1

2.4 Liquefaction ........................................................................................................................ 2-3

3. SUBSURFACE STRATIGRAPHY AND ENGINEERING LAYERING ..................................... 3-1

3.1 Summary of Field Investigation and Laboratory Testing ................................................... 3-1

3.2 Stratigraphy ........................................................................................................................ 3-1

3.2.1 Soil Survey Review ............................................................................................ 3-2

4. DISCUSSION AND RECOMMENDATIONS .............................................................................. 4-1

4.1 Foundation Recommendations ........................................................................................... 4-1

4.2 Lateral Earth Pressure and Sliding Analyses ...................................................................... 4-1

4.3 Slab-on-grade Considerations ............................................................................................ 4-4

4.4 Chemical Considerations .................................................................................................... 4-4

4.5 Site Preparation and Excavation Recommendations .......................................................... 4-4

4.5.1 Climate ................................................................................................................ 4-4

4.5.2 Clearing and Grubbing ........................................................................................ 4-5

4.5.3 Excavations and Backfill .................................................................................... 4-5

4.5.4 Grading and Filling ............................................................................................. 4-6

4.5.5 Slope Stability and Erosion ................................................................................. 4-6

4.5.6 Drainage .............................................................................................................. 4-6

4.6 Structural Fill and Aggregate Recommendations ............................................................... 4-7

5. LIMITATIONS ............................................................................................................................... 5-1

6. REFERENCES ................................................................................................................................ 6-1

Geotechnical Report vi North Wind Resource Consulting, LLC

FIGURES

Figure 2-1. Screen Shot of USGS Interactive Quaternary Fault Map. ....................................................... 2-2

Figure 4-1. Effect of Wall Movement on Wall Pressures (from NAVFAC DM7.02) ............................... 4-2

TABLES

Table 2-1. Static Equivalent Fluid Pressure. .............................................................................................. 2-2

Table 3-1. Laboratory Test Results. ........................................................................................................... 3-1

Table 4-1. Static Equivalent Fluid Pressure. .............................................................................................. 4-2

Table 4-2. Typical Properties of Compacted Soils (from NAVFAC DM 7.02). ....................................... 4-3

Table 4-3. Structural Fill Specifications. ................................................................................................... 4-7

APPENDICES

Appendix A: Test Pit Locations ................................................................................................................ A-1

Appendix B: Test Pit Logs ........................................................................................................................ B-1

Geotechnical Report vii North Wind Resource Consulting, LLC

ACRONYMS AND ABBREVIATIONS

AASHTO American Association of State Highway and Transportation Officials

ACI American Concrete Institute

ASTM American Society for Testing and Materials bgs below ground surface

CBR California Bearing Ratio

FS Factors of Safety ft feet

IBC International Building Code

in. inch

ISPWC Idaho Standard for Public Works Construction

LL liquid limit

NAVFAC DM Naval Facilities Engineering Command Design Manual

NWRC North Wind Resource Consulting, LLC

OSHA Occupational Safety and Health Administration pcf pounds per cubic foot

PI plasticity index

TP test pit

USCS United Soil Classification System

USDA United States Department of Agriculture

USGS United States Geological Survey

UW unit weight

Geotechnical Report 1-1 North Wind Resource Consulting, LLC

Geotechnical Report Rosebud Quarters Building Design

Bureau of Land Management West Desert District

Salt Lake City, UT

1. INTRODUCTION

This report presents the findings, conclusions, and recommendations of a geotechnical investigation and analysis for the proposed Bureau of Land Management (BLM) site to be constructed about 20 miles southwest of Rosette, UT, off State Highway 30. These findings, conclusions, and recommendations are based on surface and subsurface conditions encountered in the North Wind Resource Consulting LLC (NWRC) field and laboratory explorations and on project details presented to this office under the ID/UT IDIQ Contract No. L14PC00105, DO #08. The objective of this investigation was to determine general soil and ground water conditions for use by the architect and engineer for application to the design of buildings and grading plans in accordance with generally accepted geotechnical engineering practices.

The report presents the results of this study.

1.1 Project Description

The Rosebud Quarters Building Design project will consist of a parcel located about 20 miles southwest of Rosette, UT, off State Highway 30. Development of the site will consist of new quarters building, future RV parking areas, and future shop. Construction will consist of an approximate 2,300 square foot, single story, wood framed buildings, with concrete slab-on-grade floors. Maximum foundation loads (dead plus live) will be light to moderate, on the order of 1 to 2 kips per linear foot for perimeter and interior walls and 10 to 20 kips for isolated columns. Since the site generally slopes to the east with moderate slopes, we expect that grading will consist of moderate cuts and fills, between 2 to 4 feet in vertical extent. The buildings will be surrounded by landscaping, exterior concrete sidewalks, gravel roadways, and native terrain.

1.2 Purpose and Scope

The purpose of this investigation was to explore and evaluate the subsurface conditions at the project site, and to provide geotechnical engineering recommendations based upon our findings. Understanding of the project is based on a preliminary topographical drawings provided by the BLM and a site visit performed on Friday April 10, 2015.

The scope of this investigation included surface reconnaissance, subsurface exploration, analysis of field and laboratory data, research of pertinent geologic literature, and report preparation. This report provides conclusions and recommendations concerning the following:

General subsurface site conditions and geology Clearing and grubbing Site preparation and earthwork grading Conventional shallow spread foundation design Subgrade preparation for slab-on-grade concrete

Geotechnical Report 1-2 North Wind Resource Consulting, LLC

Lateral earth pressures and drainage recommendations for retaining structures Construction considerations including:

o Climate o Excavation and backfill o Slope stability and erosion protection o Drainage

Structural sections for concrete pavements

1.3 Terms and Conditions / Warranties

Geotechnical reports are written to provide test results, observations, and professional opinions regarding a specific site for a specific project. This report was prepared for BLM. The contents of this report may not be relied upon by any other party without the expressed written permission of NWRC, and the written permission of BLM. The report presents site conditions at the time of the investigation and for the aforementioned proposed development.

Each geotechnical report considers only the site boundaries and construction information presented at the time of the investigation. This geotechnical report cannot be used for an adjacent lot and modifications of construction plans (i.e. size, shape, location, weight, intended use) nullifies the conclusions and recommendations contained in this report, unless indicated otherwise by the geotechnical engineer.

The site conditions which existed at the time of the geotechnical investigation can change. Conditions can only be reported at a particular time and place and no guarantee exists to ensure that recommendations will apply after natural or man-made changes occur. Examples of some possible changes include: floods, earthquakes, fluctuation of groundwater, construction activities on or next to site, demolition of existing structures, and the addition or removal of soil. The report should be updated prior to construction if a minimum of one year has elapsed from the issued date.

Our professional services were performed, our findings obtained, and our recommendations proposed in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties either expressed or implied. Test findings and statements of professional opinion do not constitute a guarantee or warranty, expressed or implied.

Geotechnical Report 2-1 North Wind Resource Consulting, LLC

2. GENERAL DATA

2.1 Geologic Setting and Stratigraphy

The Project Site is located west of State Highway 30 just north of Immigant Trail Road east of the Grouse Creek Mountain in Box Elder County Utah. The site consists of several acres and is currently developed as field office for BLM including an recently demolished quarters building, sheds and several other small outbuildings, a helo pad, and a Division of Natural Resources quarters building. The site is accessed from the southeast and has a road that encircles the site with the exception of the Helo pad. The site and surrounding native high desert trees and shrubs and is moderately sloping up to the west towards the Grouse Creek Mountains. The site slopes are about 4 to 6 percent. Elevation at the site is about 5125 feet.

Drainage consists of percolation by site soils and overland flow to the southeast into native drainage swales. A spring also exists just north of the project site with flows mainly flowing to the west of the site.

Vegetation consists of native grasses, shrubs, and trees.

Surficial alluvium soils consist mainly of poorly to well graded sands and silts from approximately 0.5 ft to depths explored (approximately 7 ft).

2.2 General Geology

The geology map of the area indicates that most of the surface soils are described as Quaternary Age gravel, sand, and mud deposited in Lake Bonneville settings and in post-Lake Bonneville alluvial fans and streams. Deposits are intermixed such that they are difficult to distinguish with variable thicknesses, generally less than 20 feet thick.

2.3 Seismic Design Criteria

Based upon the regional geological maps of the area (see Figure 2-1), no active faults are known to transverse the site. Further, no indications of faulting were discovered during our field investigation.

Although no detailed earthquake hazard maps for the site are available, the published geologic map by the Utah Geological Survey (UGS 2003) show faults active during Quaternary time and will be considered the most likely to undergo future movement.

Geotechnical Report 2-2 North Wind Resource Consulting, LLC

Figure 2-1. Screen Shot of USGS Interactive Quaternary Fault Map.

Based upon the soil properties, site soils would be classified as Site Class D in accordance with Chapter 16 of the 2012 edition of the International Building Code (IBC). The site latitude and longitude coordinates along with the soil class were used in the United States Geologic Survey (USGS) NSHMP_HazardApp program to determine the short and one second period responses for the project site.

Table 2-1 summarizes the 2012 IBC soil parameters which may be used for design of structures at the subject site.

Table 2-1. Static Equivalent Fluid Pressure.

2012 INTERNATIONAL BUILDING CODE SEISMIC DESIGN PARAMETERS

Site Class D Mapped spectral acceleration for short periods [from Figure 1615(5)] SS 0.431g Mapped spectral acceleration for 1-second periods [from Figure 1615(6)] S1 0.138g Site coefficient [from Table 1615.1.2 (1)] Fa 1.46 Site coefficient [from Table 1615.1.2 (2)] Fv 2.25 Max considered earthquake spectral response acceleration for short periods SMS=FaSS 0.627g Max considered earthquake spectral response acceleration for 1-second periods

SM1=FvS1 0.310g

5% damped design spectral response acceleration at short periods SDS=2/3 SMS 0.418g 5% damped design spectral response acceleration at 1-second periods SD1=2/3 SM1 0.207g Peak Ground Acceleration (PGA) (%g) 0.2g

Project Site

Geotechnical Report 2-3 North Wind Resource Consulting, LLC

2.4 Liquefaction

Liquefaction is a phenomenon where saturated, relatively loose, granular soils lose their bearing strength during ground shaking (usually caused by seismic events). The liquefaction potential at the site would be considered low. Although there are some areas with potentially high groundwater in liquefiable soils the potential for adequate ground accelerations to induce liquefaction (about Magnitude 5) is low.

Geotechnical Report 3-1 North Wind Resource Consulting, LLC

3. SUBSURFACE STRATIGRAPHY AND ENGINEERING LAYERING

3.1 Summary of Field Investigation and Laboratory Testing

The field exploration conducted at the site consisted of excavating three exploratory test pits to depths of approximately 7 ft below the existing ground surface. The test pits were excavated with a rubber tired backhoe (Case 590 Super N) with a 24 inch bucket. The locations of the test pits are shown on the Test Pit Location Map, Plate No. 1 in Appendix A. The test pits were located in the field by sighting from features shown on the site topographic map; hence, accuracy of test pits shown on Plate No. 1 should be considered approximate.

A log of each test pit was maintained by visually classifying soils encountered according to the Unified Soil Classification System (USCS). Representative bulk soil samples were obtained and preserved in plastic sample bags for possible laboratory testing. Soil conditions encountered are presented on the logs of test pit found in Plates No. 2 through 4 in Appendix B.

Laboratory tests were performed on selected representative samples to aid in soil classification and to estimate the engineering properties of the native soils. The testing program consisted of: sieve analysis tests and Atterberg limits tests. Results of the laboratory tests are shown partially on the logs of each test pit and are summarized in the Laboratory Test Results Table 3-1, below. All laboratory testing was conducted in accordance with generally accepted industry standards and appropriate American Society for Testing and Materials (ASTM) standards.

Table 3-1. Laboratory Test Results.

Laboratory Test Results

Test Pit No.

Depth (ft)

USCS Soil Type

Grain Size Distribution Atterberg Limits % Gravel % Sand % Fines Liquid Limit Plasticity Index

TP2 0.5-2.5 ML 9 32 58.9 - NP

TP3 5.0-5.5 CL 0 18 82.3 31 12

3.2 Stratigraphy

Visual classification of each soil stratum encountered according to ASTM D2488 (Visual Manual Procedure) was made at the time of the field exploration test pits were excavated. The soil lithology encountered in the test pits was relatively consistent across the site. Generally the upper soils consisted of a light brown sandy silt top soil with crushed gavel, approximately 0.5 ft thick which was underlain by a light brown sandy silt with traces of gravel extending to approximately 3.5 ft below ground surface (bgs).

This sandy silt layer was underlain by a 2 inch lens of light tan silt. Below this silt layer the soils consisted of a brown lean clay with sand to depths explored, approximately 7 ft. A thin (2 inch) layer of light brown sandy gravel was noted in test pit TP-1 at approximately 2.5 feet bgs. A more detailed description of the soils encountered can be found in the Logs of Test Pits found in Appendix B, Plates No.

2 through 4. Test pit logs show subsurface conditions at the time and location of the field investigation and may not be representative of subsurface conditions at other locations and times. A test pit legend is presented in Plate No. 5.

No signs of groundwater were encountered during our field investigation. Groundwater levels could change due to rainfall, snowmelt, irrigation, construction activities, or other factors. The evaluation of these factors would require long term monitoring and is beyond the scope of this study. The design engineer should take this into consideration if grading encroaches into groundwater depths.

Geotechnical Report 3-2 North Wind Resource Consulting, LLC

3.2.1 Soil Survey Review

A review of the United States Department of Agriculture (USDA) Soil Conservation Service, Soil Survey of Box Elder County, Utah, Western Part (UT601), 2014, indicates one soil type: Kunzler-Lembos association, 1 to 5 percent slopes. Specific soil characteristics of this soil type can be found below:

Kunzler-Lembos association, 1 to 5 percent slopes – Kunzler-Lembos soils occur in alluvium derived from limestone and/or alluvium derived from sandstone and is found mainly in fan remnants. Characteristics of this soil type include well drained, moderate runoff, and low to moderate erosion hazard.

Geotechnical Report 4-1 North Wind Resource Consulting, LLC

4. DISCUSSION AND RECOMMENDATIONS

From a geotechnical engineering standpoint, it is the engineer’s opinion that the site is suitable for construction of the proposed buildings, provided all of the conclusions and recommendations presented in this report are incorporated into the design and construction. The following sections present the conclusions and recommendations for the proposed site.

4.1 Foundation Recommendations

Various foundation types may be considered for the support of the proposed structure. Some foundation types which may be considered include shallow, stem/spread footings, or interior piers tied together with grade beams bearing on native soils or structural fill. Minimum widths of stem/spread footing or grade beams are 12 inches. All exterior footings or grade beams shall be embedded a minimum of 30 inches below lowest adjacent exterior finished grade for frost protection and confinement. Interior footings may be founded at grade or embedded 12 inches below grade for confinement.

Foundations designed and constructed in accordance with this report and bearing in the sandy silt/clay or sandy silt layers may be loaded to a bearing capacity of 1,500 pounds per square foot total load (dead plus live). If a higher bearing capacity is desired, it is recommended that foundation be supported on a minimum of 2 feet of structural fill. For foundations supported on a minimum of 2 feet of structural fill a bearing capacity of 3,000 pounds per square foot total load may be used for design. The allowable bearing capacities may be increased by 1/3 for temporary wind and seismic loads.

Total settlement, either immediate or long term, of foundations will vary depending on the plan dimensions of the foundation and actual loads supported. Based on anticipated foundation dimensions and loads, the estimated maximum settlement of footings will be on the order of less than 1 inch.

Differential settlement between similarly loaded, adjacent footings is expected to be less than ½ inch. It is expected that settlement of all foundations should occur rapidly and should be essentially complete shortly after initial loading. Additional settlement should be expected during a strong seismic event.

To ensure adequate support of footing, extra precautions should be taken when footings are located adjacent to trenches. The bottom of footings should be 1 foot below the imaginary plane with inclination of 1.5 horizontal to 1 vertical extending upward from the nearest bottom edge of the adjacent trench.

Foundations should be placed on firm native soils or compacted structural fill. Footing excavations shall be cleaned of all debris, loose or soft soils, and water, prior to placement of steel or concrete.

4.2 Lateral Earth Pressure and Sliding Analyses

Recommended lateral earth pressures are required for design of retaining structures including foundations. For this project, these pressures are estimated by applying recommended pressure coefficients to the estimated moist unit weight of proposed fill material to calculate an equivalent fluid pressure. If, during backfill operations, the top of the soil-retaining structure is restrained against lateral deflection at the top, the at-rest equivalent fluid pressure should be used for design. If the top is allowed to deflect away from the soil mass, the active equivalent fluid pressure may be used for design. While, if the top is allowed to deflect into the soil mass, the passive equivalent fluid pressure may be used for design. The deflections that would typically generate the active and passive pressures are less than 0.5 in.

for active pressures and 1.5 in. for passive pressures. These deflections are calculated based on Figure 1 of the Naval Facilities Design Manual (NAVFAC DM) DM7.2 found on page DM7.2-60, presented in Figure 4-1 below.

Geotechnical Report 4-2 North Wind Resource Consulting, LLC

Figure 4-1. Effect of Wall Movement on Wall Pressures (from NAVFAC DM7.02)

The coefficients and static pressures recommended for design are listed in Table 4-1. These values are based on the correlated soil friction angles and bulk unit weights of typical compacted soils found in NAVFAC DM7.2, Table 1, Page 7.2-39, presented in this report as Table 4-2. The values of sandy silt ML and lean clay with sand CL were used.

Table 4-1. Static Equivalent Fluid Pressure.

Soil Type and Characteristics Lateral Earth Pressure Case and Coefficient Equivalent Fluid Pressure

Sandy Silt ‘ = 32o U.W. = 100 pcf

At-rest case, Ko = 0.47 47 pcf (unsaturated) Active case, Ka = 0.31 31 pcf (unsaturated) Passive case, Kp = 3.26 326 pcf (unsaturated)

Lean Clay with Sand ‘ = 28o U.W. = 95 pcf

At-rest case, Ko = 0.53 50 pcf (unsaturated) Active case, Ka = 0.36 34 pcf (unsaturated) Passive case, Kp = 2.77 263 pcf (unsaturated)

Geotechnical Report 4-3 North Wind Resource Consulting, LLC

Table 4-2. Typical Properties of Compacted Soils (from NAVFAC DM 7.02).

In addition to the lateral earth pressures found in Table 4-1, lateral surcharge loads from heavy equipment or storage materials should be considered for design of retaining structures. Lateral surcharge loads are in addition to the above coefficients. A lateral surcharge pressure coefficient of 0.45 acting uniformly over the entire below-grade soil-retaining structure should be used to estimate surcharge loads from heavy equipment operation and storage materials.

For sliding stability analyses, the frictional resistance of concrete footings or foundations placed against rock or soils shall be calculated as µR, where:

µ = coefficient of friction between concrete and granular soil, 0.55, and fine grained soils, 0.35.

(NAVFAC DM-7.2, page 7.2-63, Table 1)

R = the applied normal force delivered to the foundation soil/rock concurrent with the sliding force

This frictional resistance, when combined with any reliable passive resistance due to shear keys or soil embedment, shall be sufficient to resist the total lateral design forces with a minimum Factor of Safety (FS) of 1.5.

Geotechnical Report 4-4 North Wind Resource Consulting, LLC

4.3 Slab-on-grade Considerations

Prior to constructing concrete floor slabs, curb and gutter, or other slabs, the upper 8 inches of slab subgrade should be scarified, moisture conditioned, and compacted as structural fill. Scarification and compaction may not be required if slabs are to be placed directly on compacted structural fill.

Slab thickness and structural-reinforcing requirements within the slab should be determined by the design engineer. A minimum of 4 inches of clean gravel or Type 2 aggregate base should be placed beneath the slab-on-grade. Clean gravel shall be well graded between a maximum of 1 inch and minimum of ¼ inch.

If moisture sensitive floor coverings are planned, impervious vapor retarder such as 10 mil visqueen, or equivalent, should be placed over gravel/base to reduce the migration of moisture vapor through the concrete slab. The vapor retarder should be protected during construction by 2 inches of fine, moist sand conforming to ACI 302.1R. The sand should be moist but not saturated at the time of concrete placement.

If the sand is saturated or standing water is evident, concrete should not be placed until sand is dried sufficiently or is replaced. Excess moisture in the sand can lead to moisture related issues in sensitive flooring placed on the concrete slab.

In order to control normal shrinkage and stress cracking in slabs, adequate reinforcement should be used together with sufficient control joints. Exterior finish grades should be at or below the floor subgrade level unless special drainage and waterproofing features are employed to reduce the potential for moisture migration under the slab. Due to the bearing soils susceptibility to movements from frost heave, the design of all slabs on grade should account for such potential movements.

4.4 Chemical Considerations

Concrete durability requirements include exposure to naturally occurring chemicals in the soils. These chemical exposures include sulfates and chlorides. The geotechnical investigation on the project site did not include testing for chemical exposure. However, the USGS Soil Survey documented a corrosion rating for concrete to be high and for steel to be high.

The reactivity of cement to sulfate and chloride concentrations in soils is an important factor for determining cement type. Based on ACI 318 Chapter 4, “Durability Requirements,” the sulfate and chloride values reported at the Project Site from the soil survey are high. We recommend the use of ASTM C 150 Type V cement unless further documentation or testing indicates otherwise. Uncoated reinforcing steel or building steel should not be placed in direct contact with soil without having a protective coating.

4.5 Site Preparation and Excavation Recommendations

4.5.1 Climate

If construction is to be conducted during the dry seasonal conditions, many problems related to soft soils may be avoided. However, shallow groundwater conditions related to springtime runoff or irrigation may result in some problems with soft soils. Lack of moisture during the dry season may cause problems with compaction of moisture sensitive soils and exposed soils. Low cohesion soils (i.e. gravels, sands, and silts) exposed in excavations may become dry, increasing the chances of sloughing or caving. Measures for these, as well as excess dust should be considered as part of the overall health and safety management plan.

Geotechnical Report 4-5 North Wind Resource Consulting, LLC

Wet weather conditions present problems with soft/wet soils and must be considered as part of the construction plan. During cooler and wetter times of year, fine-grained soils such as silts and clays become unstable with increased moisture content.

Prior to placement of structural fill materials or concrete, frozen soils must either be allowed to thaw or be removed to depths of non-frozen soils. Frozen soils shall not be placed as structural fill until allowed to thaw and return to optimal moisture conditions.

4.5.2 Clearing and Grubbing

The excavation boundaries, building pads, roadways, and parking areas should be initially cleared of all vegetation, trees, brush, roots, irrigation lines, near surface debris, organic soils, deleterious materials, and disturbed soils. All vegetation and debris materials should be removed from the site. Undocumented fill and underlying native loose soils should be removed to native undisturbed soils. Clean top soils and disturbed soils can be stockpiled and placed as a final lift in landscaped areas only.

Remove all buried structures (i.e., foundations, pipes, abandoned utilities, or duct banks) and clean loose soils and debris from excavations. Further, over-excavate a minimum of 3 ft below removed structures.

Old water wells, monitoring wells, and test boreholes that penetrate the bedrock shall be abandoned according to local and state regulations. Voids resulting from removed structures shall be properly backfilled and compacted during grading operations.

4.5.3 Excavations and Backfill

The site soils (sandy silts and clays) can be excavated using conventional excavation equipment. These soils should be excavated as needed but should extend a minimum of 5 ft beyond the building footprint for over excavations and large cuts.

Temporary shallow excavations that do not exceed 4 ft in depth may be constructed with side slopes approaching vertical, provided that proper moisture conditions are maintained. Below this depth or if trenches are allowed to dry out, the excavations may become unstable. Therefore it is recommended that slopes be constructed in accordance with Occupational Safety and Health Administration (OSHA) regulations (29 Code of Federal Regulations [CFR], Section 1926, Subpart P). Based on these regulations, most of the onsite soils are classified as “Type B” soils and as such, excavations up to 20 ft in depth shall have a maximum slope of 1 foot horizontal to 1 foot vertical (1 H:1V).

Flatter slopes and/or shoring might be required if loose, cohesionless soils are encountered along the slope face. Sloughing of granular soils could occur if soils are allowed to dry or are wetted during rain/snow periods. Sloping and benching for excavations greater than 20 ft deep shall be designed by a registered professional engineer. Slopes will further need to be monitored by competent personnel during construction and throughout the construction process in order to protect workers from being injured from falling material and sloughing.

When open slope excavations conflict with existing buildings or utilities, or when soil conditions limit or prohibit open cut slopes, temporary excavation support (shoring) systems may need to be used.

Temporary shoring systems should be selected and installed with minimal disturbance to existing facilities. Examples of shoring systems that could be used at the site are sheet piles or pre-drilled soldier piles with pressure treated wood lagging system. It is beyond the NWRC scope of work to provide a detailed analysis for temporary shoring design. As design plans are finalized, we recommend that NWRC be retained to perform the analyses on the temporary excavation support systems and observations of slopes, as needed.

Geotechnical Report 4-6 North Wind Resource Consulting, LLC

Heavy construction equipment, building materials, excavated soils and vehicular traffic should not be allowed within 1/3 of the slope height from the top of any excavation without special consideration. In addition to heavy loads on slopes, other geological hazardous features should be evaluated. Some of these hazards include discontinuities in soil layers and collapsible clays. Collapsible clays are often found in loess materials and should be evaluated for stability and maintained with good drainage. During wet weather, earthen berms or other methods should be used to prevent runoff from entering excavations.

Backfill in the pipe zone (material within 6 in. below and 12 in. above the pipe) of underground utilities shall, as a minimum, consist of clean, granular materials free of clay and organic material, with 100% passing a 1-in. sieve and not more than 8% fines (passing a No. 200 sieve). See Table 4-5 for structural fill and trench fill material criteria. Trench zone backfill (material from pipe zone to subgrade) shall consist of structural fill materials placed in the structural areas (i.e., under foundation, roadways, paved areas, and other slabs) and native soils in non-structural areas. Soils used for backfill should be uniformly moisture conditioned, placed, and compacted per the structural fill section criteria. Jetting and flooding shall not be permitted for compaction of backfill. Poor compaction in utility trench backfill may cause excess settlements or unstable soils, resulting in damage to overlying structures, pavements, and slabs.

4.5.4 Grading and Filling

After clearing and grubbing operations and any excavation cuts have been completed the subgrade soils shall be scarified a minimum of 8 in., moisture conditioned, and compacted to dry densities of 95% of the maximum dry densities obtained by the Standard Test Methods for Laboratory Compaction Characteristics of Soil, using the Modified Effort per ASTM D 1557. The soil should be moisture conditioned to within 2% (plus or minus) of the optimum moisture content obtained in the same test. Fill placed on the building pads and in pavement areas should be non-expansive and placed as structural fill.

4.5.5 Slope Stability and Erosion

Stability of permanent cut and fill slopes is dependent upon shear strength, unit weight and moisture content of soils, and slope angle. Cut and fill slopes at the Site should be stable at inclinations of up to 2 horizontal to 1 vertical. However, if granular, cohesionless soils are prevalent, then a 3 horizontal to 1 vertical slope should be used. It is recommended that permanent slopes be flatter whenever feasible.

Slope performance will be primarily affected by surface runoff. Therefore, it is recommended that drainage be directed to flow away from slope faces by interceptor ditches or other means. Slope faces should further be protected from direct rain impact and melting snow by permanent erosion control measures, such as riprap, geosynthetics, and/or vegetation.

4.5.6 Drainage

Special care should be taken to ensure adequate drainage is provided throughout the life of the structure.

Final elevations at the Site should be planned so that drainage is diverted away from all building foundations and roadway/pavement sections. Drainage grading should be sloped and maintained to carry surface water away from bearing soils and off the Site. Roof gutters and downspouts are recommended to be designed to discharge water on splash blocks a minimum of 2 ft from the structure, or to be connected to tight lines that drain away from the building or to a storm drain system. Flatwork adjacent to buildings should slope a minimum of 2 percent for a distance of 5 ft. Exposed exterior subgrade soils should slope away from the structure a minimum of 5 percent for a distance of 10 ft beyond the building perimeter.

Geotechnical Report 4-7 North Wind Resource Consulting, LLC

4.6 Structural Fill and Aggregate Recommendations

Structural fill will be required beneath any shallow foundations, heavily loaded floor slabs, and areas adjacent to retaining wall structures. No significant native gravel alluvium with acceptable structural fill material was encountered during our field investigation. There was a thin layer of sandy gravel that could potentially be classified as structural fill but did not appear in large quantities. If this material is found to be more abundant then laboratory testing for these soils should be performed to confirm that they are within the granular structural fill specifications established in this Section.

The layers of sandy silts located in the upper 3 feet are not acceptable as structural fill material.

However, if field material becomes sandier during earth working operations, it could be checked for acceptability as fill beneath pavements and lightly loaded floor slabs. There were no naturally occurring utility trench bedding or aggregate base course materials encountered during the site investigation so they will need to be imported.

See Section 3 for additional information on subsurface soil strata and characteristics. All structural fill shall meet the specifications outlined in Table 4-5.

Table 4-3. Structural Fill Specifications.

Structural Fill Product Allowable Use

Material Specifications Sieve Size

Passing

Granular Structural Fill Foundation, heavily loaded floor over-excavation Wall backfill

Soil classified as GP, GP-GM, GW, SP, SP-SM according to the United Soil Classification System (USCS), and meeting the gradation provided.

Soil consisting of inert earth materials with <3% organics or other deleterious substances (wood, metal, plastic, waste, etc.)

4 in. 100 3 in. 90-100 No. 4 30-60

No.

<10

Utility Trench Bedding Soil may not contain particles larger than 1 in. in median diameter and must meet the required gradation with a maximum PI of 6.

1 in. 100 No. 10 0-50 No. 40 0-30

No.

0-15

Aggregate Base Course Over-excavations Foundation and slab support General structural fill

Soil may not contain particles larger than 1 in.

in median diameter and must meet the required gradation

1 in. 100 ¾ in. 90-100 No. 4 40-65 No. 8 30-50 No.

3-9

General Structural Fill Lightly loaded floor slab and pavement

Soil classified as SM, GM or granular structural fill according to the USCS and meeting the gradation.

Soil consisting of inert earth materials with <3% organics or other deleterious substances (wood, metal, plastic, waste, etc.)

3 in. 100

No.

<50

General Fill General site grading

Soils classified as SP, SM, ML, CL with a liquid limit < 40% and a plasticity index < 22. Soil consisting of inert earth materials with <3% organics or other deleterious substances (wood, metal, plastic, waste, etc.).

3 in. 100

Geotechnical Report 4-8 North Wind Resource Consulting, LLC

All fill materials shall be placed in maximum 8-in. thick lifts. Each lift shall be moisture conditioned to near optimum moisture content and compacted to a minimum of 95% of ASTM D 1557 Modified Proctor. The maximum loose-lift thickness is based on using large, 5-ton, smooth-drum vibratory rollers and should be reduced when smaller or lighter compaction equipment is used.

Granular structural fill material with significant gravel content (>30% retained on the ¾” sieve) may be used as granular structural fill material if it meets the above criteria, but cannot be tested for density. This coarse fill material will need to have a method developed by the contractor based on means and methods of compaction and material characteristics. The Geotechnical Engineer will approve all compaction methods and will be retained to monitor compaction efforts during construction.

Geotechnical Report 5-1 North Wind Resource Consulting, LLC

5. LIMITATIONS

The recommendations of this report are based on field explorations, laboratory tests, and the engineer’s understanding of the proposed construction. If the proposed construction is modified or re-sited, or if subsurface conditions are found to differ from those found in this report, the conclusions and recommendations of this report shall be considered invalid, unless changes and/or conditions are reviewed and modified or approved in writing.

The conclusions and recommendations of this report are based on the site conditions as they existed at the time of the field exploration. It is assumed that the subsurface soils encountered in the test pits are representative of the subsurface conditions throughout the site.

The engineer’s professional services were performed, findings obtained, and recommendations proposed in accordance with generally accepted engineering principles and practices. This warranty is in lieu of all other warranties either expressed or implied. Test findings and statements of professional opinion do not constitute a guarantee or warranty, expressed or implied.

The scope of services did not include any environmental assessment or investigation for present or absence of wetlands, hazardous or toxic materials in the soils, surface water, groundwater or air, on or below or around this site. The use of information contained in this report for bidding purposes shall be at the contractor’s option and risk.

Geotechnical Report 6-1 North Wind Resource Consulting, LLC

6. REFERENCES

29 CFR 1926, Subpart P, 2002, Title 29, “Labor,” Part 1926, “Safety and Health Regulations for Construction,” Subpart P, “Excavations,” Code of Federal Regulations, Office of the Federal Register.

AASHTO, GDPS, 1993, “AASHTO Guide for Design of Pavement Structures,” American Association of State Highway and Transportation Officials, Washington, D.C., 1993.

ACI 302.1R-04, “Guide for Concrete Floor and Slab Construction,” American Concrete Institute, Farmington Hills, MI, 2004.

ACI 318-14, “Building Code Requirements for Structural Concrete and Commentary,” American Concrete Institute, Farmington Hills, MI, 2014.

ASTM D1557-12, “Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)),” ASTM International, West Conshohocken, PA, 2012.

ASTM D2488-09a, “Standard Practice for Description and Identification of Soils (Visual-Manual Procedure),” ASTM International, West Conshohocken, PA, 2009.

ASTM C150 / C150M-12, “Standard Specification for Portland Cement,” ASTM International, West Conshohocken, PA, 2012.

IBC-2012, “International Building Code, 2012 Edition,” International Code Council, Washington, D.C.

2012.

NAVFAC DM-7.2, “DM-7.02 Foundations and Earth Structures,” Naval Facilities Engineering Command, Alexandira, VA, September 1986.

USGS, http://earthquake.usgs.gov/hazards/qfaults/map/ , United States Geological Survey, Washington D.C.

Web Soil Survey, http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx, “Box Elder County, Utah, Western Part (UT601),” United Stated Department of Agriculture, Natural Resources Conservation Service, 2014.

30130.008‐TR‐001

Geotechnical Report A‐1 North Wind Resource Consulting, LLC

Appendix A

Test Pit Locations

N

S

W E

DATE:

NWI DWG FILE:

JOB NUMBER:

FIGURE NUMBER:

REV NUMBER:

DWG SCALE:

LEGEND

TP-1

TP-2

TP-3

30130.008‐TR‐001

Geotechnical Report B‐1 North Wind Resource Consulting, LLC

Appendix B

Test Pit Logs

GRAB

S1

GRAB

S2

Passing #200 = 58.9%, Non-plastic

2" lens of sandy gravel

2" lens of light tan silt

Terminated test pit

ML

CL-

ML

0.0-0.5 ft Topsoil

0.5-3.5 ft Sandy silt, moist, medium stiff to stiff consistency

3.5-7.0 ft Sandy silty clay, moist, medium stiff to stiff consistency

NOTES

GROUND ELEVATION

LOGGED BY GLT

EXCAVATION METHOD Test Pit

TEST PIT SIZE

EXCAVATION CONTRACTOR BLM GROUND WATER LEVELS:

CHECKED BY BC

DATE STARTED 4/10/15 COMPLETED 4/10/15

AT TIME OF EXCAVATION ---

AT END OF EXCAVATION ---

AFTER EXCAVATION ---

D E

P T

H (f t)

S A

M P

LE

T

Y P

E N

U M

B E

R

TP-01

PROJECT NAME Rosebud Quarters Building Design

PROJECT LOCATION Box Elder County, UT

CLIENT Bureau of Land Management

PROJECT NUMBER 30130.008

REMARKS

U .S

.C .S

G R

A P

H

IC

LO

G

MATERIAL DESCRIPTION

Plate No.2

2" lens of light tan silt

Terminated test pit

ML

CL-

ML

0.0-0.5 ft Topsoil

0.5-3.5 ft Sandy silt, moist, medium stiff to stiff consistency

3.5-7.0 ft Sandy silty clay, moist, medium stiff to stiff consistency

NOTES

GROUND ELEVATION

LOGGED BY GLT

EXCAVATION METHOD Test Pit

TEST PIT SIZE

EXCAVATION CONTRACTOR BLM GROUND WATER LEVELS:

CHECKED BY BC

DATE STARTED 4/10/15 COMPLETED 4/10/15

AT TIME OF EXCAVATION ---

AT END OF EXCAVATION ---

AFTER EXCAVATION ---

D E

P T

H (f t)

S A

M P

LE

T

Y P

E N

U M

B E

R

TP-02

PROJECT NAME Rosebud Quarters Building Design

PROJECT LOCATION Box Elder County, UT

CLIENT Bureau of Land Management

PROJECT NUMBER 30130.008

REMARKS

U .S

.C .S

G R

A P

H

IC

LO

G

Plate No.3

GRAB

S1

GRAB

S2

2" lens of light tan silt

Passing #200 =

82.3%, LL = 31,

PI = 12%

Terminated test pit

ML

CL

1.0-3.5 ft Sandy silt, dry to moist, medium stiff to stiff consistency

3.5-7.0 ft Lean clay with sand, dry to moist, medium stiff to stiff consistency

NOTES

GROUND ELEVATION

LOGGED BY GLT

EXCAVATION METHOD Test Pit

TEST PIT SIZE

EXCAVATION CONTRACTOR BLM GROUND WATER LEVELS:

CHECKED BY BC

DATE STARTED 4/10/15 COMPLETED 4/10/15

AT TIME OF EXCAVATION ---

AT END OF EXCAVATION ---

AFTER EXCAVATION ---

D E

P T

H (f t)

S A

M P

LE

T

Y P

E N

U M

B E

R

TP-03

PROJECT NAME Rosebud Quarters Building Design

PROJECT LOCATION Box Elder County, UT

CLIENT Bureau of Land Management

PROJECT NUMBER 30130.008

REMARKS

U .S

.C .S

G R

A P

H

IC

LO

G

Plate No.4

GRAVEL

AND

GRAVELLY

SOILS

CLAYEY GRAVELS, GRAVEL - SAND -

CLAY MIXTURES

WELL-GRADED SANDS, GRAVELLY

SANDS, LITTLE OR NO FINES

POORLY-GRADED SANDS,

GRAVELLY SAND, LITTLE OR NO

FINES

SILTY SANDS, SAND - SILT

MIXTURES

CLAYEY SANDS, SAND - CLAY

MIXTURES

INORGANIC SILTS AND VERY FINE

SANDS, ROCK FLOUR, SILTY OR

CLAYEY FINE SANDS OR CLAYEY

SILTS WITH SLIGHT PLASTICITY

INORGANIC CLAYS OF LOW TO

MEDIUM PLASTICITY, GRAVELLY

CLAYS, SANDY CLAYS, SILTY CLAYS,

LEAN CLAYS

ORGANIC SILTS AND ORGANIC

SILTY CLAYS OF LOW PLASTICITY

INORGANIC SILTS, MICACEOUS OR

DIATOMACEOUS FINE SAND OR

SILTY SOILS

INORGANIC CLAYS OF HIGH

PLASTICITY

SILTS

AND

CLAYS

MORE THAN 50%

OF MATERIAL IS

LARGER THAN

NO. 200 SIEVE

SIZE

MORE THAN 50%

OF MATERIAL IS

SMALLER THAN

NO. 200 SIEVE

SIZE

MORE THAN 50%

OF COARSE

FRACTION

PASSING ON NO.

4 SIEVE

MORE THAN 50%

OF COARSE

FRACTION

RETAINED ON NO.

4 SIEVE

SOIL CLASSIFICATION CHART

(APPRECIABLE

AMOUNT OF FINES)

(APPRECIABLE

AMOUNT OF FINES)

(LITTLE OR NO FINES)

FINE

GRAINED

SOILS

SAND

AND

SANDY

SOILS

SILTS

AND

CLAYS

ORGANIC CLAYS OF MEDIUM TO

HIGH PLASTICITY, ORGANIC SILTS

PEAT, HUMUS, SWAMP SOILS WITH

HIGH ORGANIC CONTENTS

LETTERGRAPH

SYMBOLS

MAJOR DIVISIONS

COARSE

GRAINED

SOILS

TYPICAL

DESCRIPTIONS

WELL-GRADED GRAVELS, GRAVEL -

SAND MIXTURES, LITTLE OR NO

FINES

POORLY-GRADED GRAVELS,

GRAVEL - SAND MIXTURES, LITTLE

OR NO FINES

SILTY GRAVELS, GRAVEL - SAND -

SILT MIXTURES

CLEAN

GRAVELS

GRAVELS WITH

FINES

CLEAN SANDS

(LITTLE OR NO FINES)

SANDS WITH

FINES

LIQUID LIMIT

LESS THAN 50

LIQUID LIMIT

GREATER THAN 50

HIGHLY ORGANIC SOILS

NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

Plate No. 5