CA FTBR PONDEROSA BRIDGE(1) Final Geotech Report.pdf

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SUBMITTED TO:

HDR Engineering 1670 Broadway, Suite 3400 Denver, CO 80202

BY:

Shannon & Wilson, Inc.

1722 3rd Street, Suite 100 Sacramento, CA 95811

(916) 438-2300 www.shannonwilson.com

GEOTECHNICAL DESIGN REPORT

CA FTBR (1), Ponderosa Bridge Replacement

PLACER COUNTY, CALIFORNIA

August 04, 2021 Shannon & Wilson No: 103897-002

CA FTBR (1), Ponderosa Bridge Replacement FINAL Geotechnical Design Report

103897-002 August 04, 2021

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Submitted To: HDR Engineering

1670 Broadway, Suite 3400

Denver, CO 80202

Attn: Mr. Alexander Whitney

Subject: FINAL GEOTECHNICAL DESIGN REPORT, CA FTBR (1), PONDEROSA

BRIDGE REPLACEMENT, PLACER COUNTY, CALIFORNIA

Shannon & Wilson prepared this report and participated in this project as a subconsultant to

HDR Engineering. Our scope of services was specified in Agreement Number

1000100048865 with HDR Engineering dated September 18, 2020. This report presents our geotechnical engineering design conclusions and recommendations and was prepared by the undersigned. We previously submitted a draft report on April 21, 2021. This final report supersedes the draft report.

We appreciate the opportunity to be of service to you on this project. If you have questions concerning this report, or if we may be of further service, please contact us.

Sincerely, SHANNON & WILSON, INC.

Debanik Chaudhuri, PhD, GE

Senior Associate

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CONTENTS

1 Introduction

1.1 General

1.2 Scope of Services

2 Project Description

3 Field Exploration

3.1 Subsurface Explorations

3.2 Rock Mapping

4 Geotechnical Laboratory Testing

5 Geology and Subsurface Conditions

5.1 Local Geology and Geologic Hazards

5.2 Generalized Subsurface

5.3 Groundwater

6 Conclusions and Recommendations

6.1 Seismic Design Considerations

6.2 Shallow (Spread Footing) Foundation Design

6.2.1 Bearing Resistance

6.2.2 Rock Slope Stability

6.2.3 Settlement

6.2.4 Lateral Resistance

6.3 Abutments

6.3.1 Lateral Earth Pressures

6.3.2 Drainage

6.4 Rock Scour Data

6.4.1 Rock Mass Rating

6.4.2 Erodibility Index

6.5 Soil Corrosion Potential

7 Construction Considerations

7.1 Earthwork

7.2 Excavation

7.3 Foundation Preparation

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7.4 Fill Placement and Compaction

7.5 Suitability of On‐Site Soils

8 Limitations

9 References

Exhibits Exhibit 6‐1: Seismic Design Parameters for Soil Profile Type B

Exhibit 6‐2: Abutment Backfill Earth Pressures

Exhibit 6‐3: Summary of Rock Mass Rating

Exhibit 6‐4: Erodibility Index Equation

Exhibit 6‐5: Summary of Erodibility Index

Exhibit 6‐6: Soil Corrosion Testing Results

Figures Figure 1: Vicinity Map

Figure 2: Site and Exploration Plan

Figure 3: Generalized Subsurface Profile A‐Aʹ

Figure 4: Design Caltrans ARS Curve Soil Profile Type B

Figure 5: Recommended Surcharge Loading for Temporary and Permanent Walls

Appendices Appendix A: Subsurface Exploration

Appendix B: Laboratory Testing

Important Information iv

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ACRONYMS

AASHTO American Association of State Highway and Transportation Officials

ARS Acceleration Response Spectrum bgs below ground surface

CALFIRE California Department of Forestry and Fire Protection

FHWA Federal Highway Administration

FS Factor of Safety

HDR HDR Engineering Inc.

K Erodibility Index ksf kilo‐pounds per square foot pcf pounds per cubic foot pH potential of Hydrogen

RMR Rock Mass Rating

SDC Seismic Design Criteria

SEE Safety Evaluation Earthquake

USGS United States Geological Survey

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1 INTRODUCTION

1.1 General

This geotechnical design report presents our geotechnical conclusions and recommendations in support of design for the planned CA FTBR (1) Ponderosa Bridge

Replacement Project (the Project) in Placer County, California. Shannon & Wilson performed our services in general accordance with our subconsultant agreement with HDR

Engineering, Inc. (HDR), dated September 16, 2020. Our understanding of the Project is based on:

a site visit with HDR’s structural engineer (John Maniscalco) on May 15, 2020 email exchanges with Mr. Alexander Whitney documents provided by HDR, including:

o U.S. Forest Service as‐built plan sheets of the existing bridge, dated January

1934 and revised in July 1938 o topographic survey plan sheets and the source AutoCAD drawing file prepared by Kjeldsen Sinnock Neudeck Inc., dated March 2020.

1.2 Scope of Services

Our scope of services included the following:

Drill two exploratory borings, one near each proposed abutment location

Perform laboratory tests on selected soil and rock samples

Perform geotechnical engineering analyses

Develop geotechnical design recommendations

Prepare a geotechnical engineering report summarizing our findings and recommendations.

2 PROJECT DESCRIPTION

The Project site is located where Ponderosa Way crosses the North Fork American River, about 3 miles southeast of Heather Glen, California as shown in the Vicinity Map, Figure 1.

The existing bridge is a one‐lane, three‐span, steel, through‐truss structure with a wood deck. We understand that the existing bridge was constructed in 1935 and has reached the end of its useful life. The bridge is supported on concrete footings founded on bedrock. We

103897-002 August 04, 2021 understand that the Project will replace the existing bridge with a new one‐lane bridge. The new bridge will also consist of three spans and be located on an offset alignment just west

(downstream) of the existing bridge as shown in the Site and Exploration Plan, Figure 2.

The existing bridge has a main span length of 129.5 feet and an overall length of 199.5 feet.

The proposed replacement bridge will be slightly longer with a main span length of 155 feet and an overall length of 223 feet.

3 FIELD EXPLORATION

3.1 Subsurface Explorations

For this Project, we drilled and sampled two geotechnical borings, designated SWB‐1 and

SWB‐2. Boring SWB‐1 was drilled to a depth of 60.5 feet below ground surface (bgs) and was located near the northwestern (north) abutment location. Boring SWB‐2 was drilled to a depth of 37.1 feet bgs and located near the southeastern (south) abutment location.

Approximate boring locations are shown in Figure 2.

A Shannon & Wilson geotechnical staff member observed the drilling, collected samples, and prepared field logs of the borings. Approximate boring locations and ground elevations were determined by measuring distances from existing bridge features and surveying with an optical level and rod with respect to the existing bridge deck. Appendix

A presents additional details regarding the exploration program, including boring logs and drilling and sampling methodology.

3.2 Rock Mapping

In addition to our subsurface explorations, a Shannon & Wilson geological staff member performed rock mapping surveys of rock outcrops throughout the Project site. The initial rock mapping survey was performed on October 16, 2020, and a follow up survey was performed on December 2, 2020. During these rock mapping surveys, we recorded rock discontinuity features including, strike and dip angles, persistence, spacing, aperture width, and roughness. Rock mapping survey data was used to determine the Rock Mass Rating

(RMR) and Erodibility Index (K), see Sections 6.4.1 and 6.4.2, and to develop the rock descriptions shown in the borings logs presented in Appendix A.

4 GEOTECHNICAL LABORATORY TESTING

Geotechnical laboratory tests were performed on selected soil and rock samples collected from the borings. Laboratory tests included visual‐manual classification, moisture content, 103897-002 August 04, 2021 grain size analysis, modified Proctor compaction, soil corrosivity, and rock unconfined compressive strength. Details of the laboratory testing and results of the tests are included in Appendix B.

5 GEOLOGY AND SUBSURFACE CONDITIONS

5.1 Local Geology and Geologic Hazards

We conducted a limited literature review to characterize geology and geologic hazards. Our review of geologic maps indicates that the bedrock near the Project site belongs to the

Mariposa Formation, which is reported to consist primarily of slate and metamorphosed graywacke and conglomerate (Saucedo and Wagner, 1992). These rocks are reported to be

Middle to Late Jurassic, approximately 150 million years or more old. At the Project site, metamorphosed conglomerate has been mapped (Chandra, 1961).

Published maps do not indicate presence of active faults crossing the Project site, and the site is not located in an Alquist‐Priolo Earthquake Fault Zone. The Grass Valley Fault and the Gillis Hill Fault lie about one‐half mile west and one mile east of the site, respectively.

Neither of these faults are considered active by the California Geological Survey (Jennings and Bryant, 2010). The Wolf Creek Fault is the closest active fault, located about 9 miles west of the Project site. Because of its distance to the site, the potential for ground surface fault rupture is low.

5.2 Generalized Subsurface

Near the north abutment location (SWB‐1), we encountered very dense sand, with silt, gravel, and boulders to a depth of 6 feet bgs underlain by moderately hard to hard metaconglomerate bedrock. Near the south abutment location (SWB‐2), we encountered moderately hard to very hard metaconglomerate bedrock beginning at the ground surface.

We observed the metaconglomerate bedrock to be coarse‐grained with gravel and cobble sized particles contained within a dark gray fine‐grained matrix. Discontinuities in the bedrock tended to be closely to widely spaced with localized very closely spaced zones occurring between approximate elevations 785 feet to 800 feet. Discontinuities tended to be smooth to slightly rough, tight to partly open, with some oxide staining, and were oriented near vertical (70‐90 degrees) and near horizontal (5‐15 degrees) resulting in a blocky rock mass. The generalized subsurface conditions for the Project are shown in the Generalized

Subsurface Profile A‐A’, Figure 3.

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5.3 Groundwater

We did not observe groundwater in either of our borings prior to encountering bedrock and switching the drilling method to rock coring. However, we did measure the North Fork

American River’s water surface to be at 37 feet below the deck of the existing bridge (Elev.

786 feet) on October 15, 2020.

6 CONCLUSIONS AND RECOMMENDATIONS

6.1 Seismic Design Considerations

According to Caltrans SDC 2.0, the design Safety Evaluation Earthquake (SEE) response spectrum is based on a design ground motion that has a 5% probability of exceedance in 50 years (975‐year return period). This return period is equivalent to a 7% probability of exceedance in 75 years. This characterization of the design ground motion matches the 75‐ year design life of the proposed bridge. The design ground motion parameters were developed using the Caltrans ARS online tool version 3.0.2, which utilizes the USGS 2014

National Seismic Hazard data. Considering the rock conditions encountered by the explorations advanced at the site, we recommend the bridge design consider Soil Profile

Type B subsurface conditions and be designed using the Caltrans SDC (Caltrans, 2019) parameters presented in Exhibit 6‐1 below. The characteristic moment magnitude is 6.3.

The design SEE acceleration response spectrum is presented in the Design Caltrans ARS

Curve Soil Profile Type B, Figure 4.

Exhibit 6-1: Seismic Design Parameters for Soil Profile Type B

Spectral Acceleration

Peak Ground Acceleration

(g)

Short Period

(0.2 second)

(g)

Long Period

(1 second)

(g)

SEE Response Spectrum Values 0.13 0.27 0.09

NOTES:

g = acceleration due to gravity; SEE = Safety Evaluation Earthquake

6.2 Shallow (Spread Footing) Foundation Design

We understand that the proposed bridge abutment and pier foundations are planned to be spread footings founded on bedrock. Dimensions of the proposed abutment footings will be 5.5 feet long (parallel to bridge alignment) and between 28 and 30 feet wide, while the proposed pier footings will be 11 feet long by 17 feet wide.

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6.2.1 Bearing Resistance

Based on data from our subsurface explorations and our engineering analysis and judgement, we recommend a nominal bearing resistance of 50 ksf for the bedrock material present at the Project site, provided the footings are founded on competent, unweathered bedrock. We recommend a bearing resistance factor of 0.45 for spread footings founded on rock (AASTHO, 2020).

6.2.2 Rock Slope Stability

We performed kinematic and limit equilibrium analyses to evaluate the stability of the rock foundations and slopes and determine if the rock slopes supporting the bridge footings meet design factors of safety or if any additional support measures were needed. The analytical methods and our conclusions are presented in this section.

We used Rocscience’s Dips and Slide2 Modeler software (Rocscience, 2021a and 2020b) to perform kinematic and equilibrium analyses, respectively. Our kinematic analysis identified that plane shear and complex plane shear (multi‐segment plane shear) are kinematically admissible and are critical failure modes for the north and south pier and abutment foundations. We also identified toppling as a kinematically admissible failure mode but toppling is not a critical failure mode due to the site‐specific geometry of the bridge foundation elements.

Based on the results of our kinematic analysis, our limit equilibrium analysis incorporated the potential for plane shear and multi‐segment complex plane shear failure modes but not toppling. We modeled the north and south foundation geometry and external bridge loading using survey data and footing loading summary data provided by HDR. For seismic (pseudo‐static) analysis, we incorporated a horizontal seismic coefficient equal to 50 percent of peak ground acceleration corresponding to the SEE.

For the model’s material properties, we used an anisotropic strength function and generalized Hoek‐Brown strength criteria to model the rock mass strength parameters. We modeled discontinuity shear strength using suggested values published by Wyllie and Mah

(2004) for conglomerate rock. We performed our analysis using the Janbu simplified method of slices and target factors of safety (FS) of 1.5 and 1.1 for static and seismic loading conditions respectively.

During our limit equilibrium analysis, results of a back analysis indicated that rock bridging is present in some form. To model the presence of rock bridges, we used methodologies published by Jennings (1971) and Wyllie and Mah (2004) to determine scaled Mohr‐

Coulomb cohesion and friction angle values for discontinuity shear strength. We performed

103897-002 August 04, 2021 a forward analysis and sensitivity analysis for a range of rock bridging percentages. Based on our analyses and field observations, we concluded that a minimum 3% rock bridges exist and evaluated rock slope stability using 3% rock bridges.

Based on the results of this analysis, we conclude that the proposed bridge foundations meet the target FS values, without requiring additional support (i.e., rock dowels), and the bearing resistance presented in Section 6.2.1 are not impacted by the presence of rock slopes.

6.2.3 Settlement

Foundations bearing on intact rock are expected to experience nominal total settlement of less than 0.5 inch. Total settlement is expected to be comprised solely of immediate (elastic) settlement and to be substantially completed during construction. Total settlement assumes the Contractor will construct spread footing foundations in a manner consistent with the plans, specifications, and our recommendations and stated construction considerations.

6.2.4 Lateral Resistance

Resistance to lateral forces caused by wind, earthquake, and other forces can be provided by the frictional resistance of the rock acting against the base of the foundation. We recommend a nominal coefficient of friction of 0.7 and a resistance factor of 0.8 for cast‐in‐ place concrete (AASHTO, 2020).

6.3 Abutments

6.3.1 Lateral Earth Pressures

We anticipate that imported fill, or suitable recovered on‐site soils, will be used as backfill within a 1H:1V (horizontal to vertical) plane behind the proposed bridge abutments. The active and at‐rest static earth pressures are applied as a triangular equivalent fluid pressure distribution, while the increase in earth pressures due to seismic loading is applied as a uniformly distributed pressure increase, as shown below in Exhibit 6‐2. These estimates are based on the specified fill soil properties described in Section 7.4.

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Exhibit 6-2: Abutment Backfill Earth Pressures

Retained Material

Type

Unit Weight

(pcf)

Friction Angle

(deg)

Active At-Rest

Earth Pressure Coeff., Ka

(dim.)1

Equivalent Fluid

Density

(pcf)

Seismic Uniform.

Dist. Press.

Increase

(psf)

Earth Pressure Coeff., K0

(dim.)1

Equivalent Fluid

Density

(pcf)

Seismic Uniform.

Dist. Press.

Increase

(psf)

Structural Backfill

125 34 0.25 32 5H 0.44 55 4H

NOTES:

deg = degrees; dim. = dimensionless; ft = feet; H = wall height in feet; pcf = pound per cubic foot; psf = pounds per square foot

Surcharge loads from motor vehicles/traffic and construction equipment will induce additional lateral loads on the abutments. For evaluating surcharge loading on the abutments, Figure 5, Recommended Surcharge Loading for Temporary and Permanent

Walls can be used.

6.3.2 Drainage

We assume that the abutments will incorporate a drainage system such that groundwater will not accumulate in the retained fill. Accordingly, our design recommendations do not include hydrostatic pressure behind the abutments.

6.4 Rock Scour Data

We understand that HDR will perform a scour analysis of the bedrock present at the Project site. To support this analysis, we determined the RMR and K values that are characteristic of the bedrock we observed during our field explorations and reconnaissance.

6.4.1 Rock Mass Rating

The RMR is a classification method that characterizes the overall quality of the rock mass

(FHWA, 2012). There are five measurable parameters used to determine a rock massʹ RMR.

These parameters include:

Strength of intact rock material (Point Load Index or Unconfined Compressive Strength)

Drill core quality (i.e., rock quality designation, RQD)

Joint spacings

Joint conditions

Ground water conditions

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A series of relative ratings are assigned to the range of values that may be encountered for each of the five listed parameters. The numerical value of the RMR is determined by summing the individual relative ratings determined for the five parameters.

Our determination of the required input parameters and RMR for the Project site is presented in Exhibit 6‐3. These values were determined by relating the measured data collected from our rock mapping surveys and subsurface exploration against tables published in Section 4.7.2 of the FHWA Hydraulic Engineering Circular No. 18 (FHWA, 2012).

Exhibit 6-3: Summary of Rock Mass Rating

Parameters Parameter Values

Relative Ratings

(dim.)

Rock Mass Rating, RMR1

(dim.)

Strength of Intact Rock Material 10,000 - 17,500 psi 7

Class No. III

Fair Rock

Drill Core Quality 60% 13

Spacings of Joints 1 - 3 ft 20

Condition of Joints Joints open 0.05 in. - 0.2 in., Continuous Joints 6

Ground Water Conditions Moist Only (Interstitial Water) 7

Orientation of Joints

(for Foundations) Fair -7

NOTES:

The Rock Mass Rating is the sum of all relative ratings.

% = percent; ft = feet; in. = inch; psi = pounds per square inch

6.4.2 Erodibility Index

K is a classification system that quantifies the erosion resistance of a rock mass and can be compared to a stream flowʹs erosive power (FHWA, 2012). The equation used to compute K is present in Exhibit 6‐4.

Exhibit 6-4: Erodibility Index Equation

Equation Variable and Definition

K 𝑀 𝐾 𝐾 𝐽

K Erodibility Index

MS Intact Rock Mass Strength Parameter

Kb Block Size Parameter

Kd Shear Strength Parameter

JS Relative Orientation Parameter

Reference: FHWA, 2012

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Our calculation of K for the bedrock observed at the Project site is presented in Exhibit 6‐5.

The input parameters were determined by relating the measured data collected from our rock mapping surveys and subsurface exploration against tables published in Section 4.7.2 of the FHWA Hydraulic Engineering Circular No. 18 (FHWA, 2012).

Exhibit 6-5: Summary of Erodibility Index

Variables Input Parameters Input Parameter Values Variable Numbers

Erodibility Index, K

Rock Mass Strength

Parameter, MS

Rock Hardness Very Hard Rock

70.0

14083

Unconfined Compressive Strength 68.9 – 120.7 MPa

Block Size Parameter, Kb

RQD

Rock Quality Designation 60% 60

17.961

Rock Joint Set Number, Jn

Number of Joint Sets 3 Joint/Fissure Sets + Random 3.34

Shear Strength

Parameter, Kd

Joint Roughness Number, Jr

Condition of Joint Smooth Undulating 2.0

2.02

Joint Alteration Number, Ja

Joint Separation 1.0 mm

1.0 Description of Gouge Unaltered joint walls, surface

staining only

Relative Orientation Parameter, JS

Dip Direction of Closer Spaced Joint Set In Direction of Stream Flow

0.56 Dip Angle of Closer Spaced Joint Set 70°

Ratio of Joint Spacing 1:1

NOTES:

Block Size Parameter is calculated as Kb = RQD/Jn.

Shear Strength Parameter is calculated as Kd = Jr/Ja.

Erodibility Index is calculated as K = (MS)(Kb)(Kd)(JS).

° = degrees; % = percent; MPa = megapascal; mm = millimeters

6.5 Soil Corrosion Potential

As mentioned earlier, we encountered a relatively thin layer of soil above bedrock near the north abutment location. We submitted one soil sample to Sunland Analytical of Rancho

Cordova, California, for analytical testing to evaluate the potential for corrosive attack on buried metals and reinforced concrete using 2020 California Department of Transportation

(Caltrans) Test Methods (CTM). Tests included pH and resistivity (CTM 643), water‐soluble chloride (CTM 422), and water‐soluble sulfate (CTM 417) concentrations (Caltrans, 2020).

Results of the corrosion testing are included in the enclosed Sunland Analytical report and summarized in Exhibit 6‐6 below.

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Exhibit 6-6: Soil Corrosion Testing Results

Boring ID

Sample Depth

(ft) pH

Minimum Resistivity

(ohm-cm x 1,000)

Chloride

(ppm)

Sulfate

(ppm)

SWB-1 1.5 7.08 7.5 2.4 17.6

NOTES:

ft = feet; ohm-cm = ohm centimeter; ppm = parts per million

Caltrans considers a soil to be corrosive to foundation elements if one or more of the following conditions exist: chloride concentration greater than or equal to 500 parts per million (ppm), sulfate concentration greater than or equal to 1,500 ppm, or pH of 5.5 or less

(Caltrans, 2018). The corrosivity test results suggest that the site soils are not corrosive to exposed buried metal or reinforced concrete.

7 CONSTRUCTION CONSIDERATIONS

7.1 Earthwork

Earthwork, including site preparation, embankment construction, placement of fill, and subgrade preparation, should conform to the requirements provided in Division 200 of the

Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP‐14 (FHWA, 2014).

7.2 Excavation

The native soil can likely be excavated using conventional excavating equipment. However, excavation equipment should be selected to handle occasional boulders present in the native soil overburden. Specialized equipment will be required to excavate the in‐place bedrock.

If blasting is required to reach the design footing elevations, all blasting activities must be performed in accordance with FP‐14 Division 205 guidelines for controlled blasting (FHWA, 2014). Alternatives to blasting include ripping and hydraulic, or mechanical, splitting or breaking (FHWA, 2011). Based on the strength of the bedrock and orientation of the joints, we expect that the in‐place bedrock will be difficult to effectively excavate by ripping. For these alternatives, the requirements for final slope face, including scaling and dressing, are the same as for slopes formed by blasting.

7.3 Foundation Preparation

We recommend that a Shannon & Wilson representative be present to provide construction support services during construction. For foundations founded on bedrock, the excavated surface shall be cleaned of all loose material and cut to a firm surface exposing competent, 103897-002 August 04, 2021 unfractured bedrock. Seams shall be cleaned out and filled with cement, grout, or mortar.

Prior to installation of the footings, a Shannon & Wilson representative should review the exposed bedrock to confirm the rock type, evaluate joints and fractures, and evaluate the stability of the bedrock. Once the Shannon & Wilson representative has inspected the footing excavations, the Contractor can pour the concrete ʺneatʺ (without forming) against the prepared bedrock. If forming is necessary, we recommend backfilling excavations outside the footing limits with plain structural concrete. If an irregular rock surface and differing rock characteristics are encountered, the use of plain (Class B) concrete is considered appropriate to provide positive contact between the footings and bedrock.

If overexcavation is required to expose competent, intact rock at footing locations, the overexcavation should be backfilled with plain structural concrete to the design footing elevation, up to a depth of 3 feet below the footing. If overexcavation greater than 3 feet is required, Shannon & Wilson should be contacted to evaluate the rock mass and provide supplemental recommendations as necessary.

If blasting is required to excavate the bedrock, any loose, fractured rock caused by overbreak below the design footing elevations should be removed and replaced with concrete at the Contractorʹs expense.

7.4 Fill Placement and Compaction

Abutment backfill should meet the requirements of Structural Backfill (FP‐14 704.04) defined as:

Maximum particle size: 3 in. (75 mm)

Material passing #200 sieve: ≤ 15%, less if below flood stage

Plasticity Index: ≤ 6

Fill should be placed in uniform, horizontal layers with the loose lift thickness not exceeding

8 inches for heavy, self‐propelled compactors, or 4 inches for hand‐operated mechanical compactors. The appropriate lift thickness will depend on the Contractorʹs equipment and the moisture content and quality of the backfill material. Compaction of backfill adjacent to abutments can result in higher lateral earth pressures against the abutments. Therefore, small equipment that is hand‐operated should be required with a line extending upward from the base of the structure at 0.5H:1V, to a maximum horizontal distance of 5 feet from the face of the abutment to reduce this potential.

Backfill material should be moisture conditioned within 2 percent of the optimum moisture content and to at least 95 percent of the maximum dry density as determined by AASHTO

T99 (standard Proctor compaction effort) in accordance with FP‐14 Section 208.

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Backfill material must be free of organics, debris, and other deleterious material. It should be noted that as the fines percent, amount of soil particles passing the No. 200 sieve, increases soil becomes more sensitive to small changes in moisture content, and adequate compaction becomes more difficult to achieve.

7.5 Suitability of On-Site Soils

Gradation and modified Proctor compaction curve testing on a bulk, near surface, soil sample collected from boring SWB‐1 is reported in Appendix B. The gradation testing results indicate that the on‐site soils meet the requirements for FP‐14 Structural Backfill and is suitable as an alternative to import fill if proper preparation of the on‐site soils is performed. Preparation for reuse of on‐site soils must require that all particles greater than

3 inches in size be removed before the on‐site soils may be used. The compaction test results, as determined by ASTM D 1557, indicate that the on‐site soils may be expected to provide:

Maximum Dry Density = 142.4 pcf

Optimum Moisture Content = 5.4%

However, we recommend additional tests on processed soil to determine maximum dry density and optimum moisture content. Verification of the on‐site soilʹs suitability as

Structural Backfill material, as described in Section 7.4, should be performed prior to construction.

8 LIMITATIONS

This report was prepared for the exclusive use of HDR and other members of the design team for specific application to this Project. Our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions included in this report. The analyses, conclusions, and recommendations contained in this report are based on site conditions as they presently exist and further assume that the explorations are representative of the subsurface conditions throughout the site; that is, the subsurface conditions everywhere are not significantly different from those disclosed by the explorations. If subsurface conditions different from those encountered in the explorations are encountered or appear to be present during construction, we should be advised at once so that we can review these conditions and reconsider our recommendations, where necessary. If there is a substantial lapse of time between the submission of this report and the start of construction at the site, or if conditions have changed because of natural forces or construction operations at or adjacent to the site, we recommend that we review our report to determine the applicability of the conclusions and recommendations.

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Within the limitations of scope, schedule, and budget, the analyses, conclusions, and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical engineering principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

These conclusions and recommendations were based on our understanding of the Project as described in this report and the site conditions as observed at the time of our explorations.

Unanticipated subsurface conditions are commonly encountered and cannot be fully determined by merely taking soil and rock samples from test borings. Such unexpected conditions frequently require that additional expenditures be made to attain a properly constructed project. Therefore, some contingency fund is recommended to accommodate such potential extra costs.

The scope of our present work did not include environmental assessments or evaluations regarding the presence or absence of hazardous or toxic substances in the soil, surface water, groundwater, or air on, below, or around this site or for the evaluation or disposal of contaminated soils or groundwater should any be encountered.

Shannon & Wilson has prepared the document, “Important Information About Your

Geotechnical/Environmental Report,” to help you and others in understanding the use and limitations of this report.

9 REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 2020, Bridge Design Specifications, 9th Edition, 555 12th Street, NW, Suite 10000, Washington, DC

California Dept. of Transportation (Caltrans), 2020, California Test Methods: Available:

https://dot.ca.gov/programs/engineering‐services/california‐test‐methods

California Dept. of Transportation (Caltrans), 2018, Corrosion guidelines, ver. 3.0, Sacramento, California.

California Dept. of Transportation (Caltrans), 2019, Seismic Design Criteria, ver. 2.0, Sacramento, California.

Chandra, D. K., 1961, Geology and Mineral Deposits of the Colfax and Foresthill

Quadrangles, California: State of California Division of Mines, Special Report 67, 50 p.

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Federal Highway Administration (FHWA), 2011, Context Sensitive Rock Slope Design

Solutions, FHWA‐CFL/TD‐11‐002, Washington, DC

Federal Highway Administration (FHWA), 2012, Evaluating Scour at Bridges, 5th Edition, Hydraulic Engineering Circular No. 18, Publication No. FHWA‐HIF‐12‐003, Washington, DC

Federal Highway Administration (FHWA), 2014, Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP‐14, Washington, DC

Jennings, C., and Bryant, W., 2010, 150th Anniversary fault activity map of California:

California Geological Survey Map No. 6, scale 1:750,000.

Jennings, J.E., 1971, A mathematical theory for the calculation of the stability of slopes in open cast mines, in Van Rensburg, P.W.J., ed., Symposium on the planning open pit mines with special reference to slope stability, 1970, Johannesburg, South

Africa, Proceedings: Cape Town, South Africa, A. A. Balkema, P. 87‐102.

Rocscience, Inc., 2020a, Dips (v. 8.006), Graphical & Statistical Analysis of Orientation Data:

Toronto, Ontario, Rocscience, Inc.

Rocscience, Inc., 2020b, Slide2 Modeler (v. 9.008), 2D Limit Equilibrium Analysis for Slopes:

Toronto, Ontario, Rocscience, Inc.

Saucedo, G. J., and Wagner, D. L., 1992, Geologic Map of the Chico Quadrangle: State of

California Department of Conservation Map No. 7 A, 5 sheets, scale 1:250,000.

Wyllie, D.C., and Mah, C.W., 2004, Rock Slope Engineering – Civil and Mining (4th ed.):

London, Spon Press, p. 431.

VICINITY MAP

PROJECT

LOCATION

CA FTBR (1)

Ponderosa Bridge Replacement

Placer County, California

Aerial imagery downloaded from Google Earth Pro on 11-10-20.

103897-002

Fi le na m e:

E

:\J

D

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\1

7\

2\

-0

F ig

Vi ci ni ty M ap _P on de ro sa

B rid ge .d w g

D at e:

1-

-2

L og in

: S

AC

0 8000 16000

Approximate Scale in Feet

FIG. 1

Sacramento

CALIFORNIA

Project Location

Los Angeles

San Francisco

SEE FIGURE 2

SEE INSET

Pon de ros a W ay

Po nd er os a W ay

Heather Glen

Applegate

Clipper Gap

Meadow Vista

Bowman

North Auburn

Chain

Foresthill Rd

G ol de n

Hwy

U pp er L ak e

C le m en tin e

Lake Clementine

Ponderose Way

Foresth ill R d

Cool

1" = 1000 Ft.

August 2021

0+

1+00

2+00

2+56

0+

1+50

2+50

SWB-1

SWB-2

Ponderosa Way

P o n d e r o s a

W y

North Fork

American River

A

A

F i l e n a m e

E

J D

E N

P l a n a n d

P r o f i l e P o n d e r o s a

B r i d g e d y o u t

P l n t e o g i n

S

A C

SITE AND EXPLORATION PLAN

August 2021

40 80

Scale in Feet

FIG. 2

SWB-1

Boring Designation and

Approximate Location

Generalized

Subsurface Profile

(See Figure 3)

LEGEND

NOTE

Drawing based on topo survey, 2307-0020_

Ponderosa_Bridge_Topo, received 12-7-20.

Proposed bridge structures adapted from Drawing

RG3178-A, General Plan and Elevation.pdf Sheet

1 of 30 prepared by HDR, dated April 2021.

APPROXIMATE

PROPOSED BRIDGE

CA FTBR (1)

Ponderosa Bridge Replacement

Placer County, California

103897-002

A

Contour Interval = 5 Feet

Datum: NAD 83

PROPOSED PIER 2

PROPOSED PIER 3

PROPOSED ABUTMENT 4

PROPOSED WINGWALL D

PROPOSED WINGWALL B

PROPOSED ABUTMENT 1

PROPOSED WINGWALL A

PROPOSED WINGWALL C

APPROXIMATE ROADWAY

CENTERLINE ALIGNMENT

E l e v a t i o n i n

F e e t

N

A V

D

Northwest

A

Southeast

A'

APPROXIMATE PROPOSED BRIDGE LIMITS

PROPOSED

PIER 2

PROPOSED

PIER 3

12+00 13+0011+00

PROPOSED

ABUTMENT 4

PROPOSED

ABUTMENT 1

GRAB

50/5"

10-16-20

SWB-1

10-19-20

SWB-2

(Proj. 13' SE) (Proj. 1' NE)

F i l e n a m e

E

J D

E N

P l a n a n d

P r o f i l e P o n d e r o s a

B r i d g e d y o u t

P r o f i l e t e o g i n

S

A C

GENERALIZED SUBSURFACE

PROFILE A-A'

August 2021

FIG. 3

CA FTBR (1)

Ponderosa Bridge Replacement

Placer County, California

103897-002

Existing Ground Surface

1. Ground surface based on topo survey, 2307-0020_ Ponderosa_Bridge_Topo, received

12-7-20. Proposed bridge structures adapted from Drawing RG3178-A, General Plan and

Elevation.pdf Sheet 1 of 30 prepared by HDR, dated April 2021.

2. This subsurface profile is generalized from materials observed in soil borings. Variations may exist between profile and actual conditions.

NOTES

Vertical = Horizontal

SWB-1

10-16-20

(Proj. 13' SE) Designation of Boring

Projected Distance and Direction

Grab Sample

Sample and Penetration

Resistance in Blows/Foot or Blows per Inches Driven

Rock Core Sample

Rock Coring Recovery (%)

Rock Quality Designation (%)

LEGEND

Approximate Rock Contact

USCS Symbol

Bottom of Boring

Date of Completion

20 40

Scale in Feet

0 50 100

50/5"

North Fork American River

Approximate Ordinary High Water

Stationing Along Proposed Roadway Centerline

FIG. 4

CA FTBR (1)

Ponderosa Bridge Replacement

Placer County, California

DESIGN CALTRANS ARS CURVE

SITE CLASS B

August 2021 103897-002

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NOTES

1.

2. Abbreviation definitions:

ARS = Acceleration Response Spectrum

Design curve was generated using the Caltrans ARS Online tool (v3.0.2)

0.0

0.1

0.2

0.3

0.4

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

S p e c tr a l A c c e le ra ti o n

S a g

Period (seconds)

RECOMMENDED SURCHARGE

LOADING FOR TEMPORARY AND

PERMANENT WALLS

File: J:\Support\library\Standard Figures\Surcharge Loading Remp-Perm Wall_Letter.dwg Date: 03-12-2014 Author: SAC

103897-002August 2021

FIG. 5

For m ≤ 0.4:

H

= 0.28 (psf) (see Note 3)

W a l l

PLAN VIEW

2.0

1.5 e p t h

F a c t o r

Z

B

1.0

0.0

0.5

W a l l

Z

Wall Line

UNIFORM SURCHARGE

EARTH BERM

(see Note 4)

Note:

H z=nH

Bottom of

Excavation x = mH

Point Load in Pounds

H

(psf)

ELEVATION VIEW

x = mH

H

Bottom of

Excavation

W a l l z=nH

Line Load in

Pounds/Foot

B) LATERAL PRESSURE DUE TO LINE LOAD

i.e. NARROW CONTINUOUS FOOTING

PARALLEL TO WALL

C) LATERAL PRESSURE DUE TO STRIP LOAD

W a l l

W a l l

W a l l

A) LATERAL PRESSURE DUE TO POINT LOAD

i.e. SMALL ISOLATED FOOTING OR WHEEL LOAD

D) LATERAL PRESSURE DUE TO

EARTH BERM OR UNIFORM

SURCHARGE

Bottom of

Excavation

Bottom of

Excavation

E) LATERAL PRESSURE DUE

TO ADJACENT FOOTING

(see Notes 5 and 6)

0 0.5 1.0

L

B

NOTES

Figures are not drawn to scale.

Applicable surcharge pressures should be added to appropriate permanent wall lateral earth and water pressure.

If point or line loads are close to the back of the wall such that m 0.4, it may be more appropriate to model the actual load distribution (i.e., Detail E) or use more rigorous analysis methods.

See text for recommended K values.

The stress is estimated on the back of the wall at the center of the length, L, of loading.

The estimated stress is based on a Poisson's ratio of 0.5.

W a l l

Bearing

Pressure q (psf)

1.

2.

3.

4.

5.

6.

I p

, Influence Factor

= 2(I p

) q s

Lateral Footing

Pressure on Wall

(derived from NAVFAC DM 7.02, 1986; and Sandhu, Earth Pressure on Walls Due to Surcharge , 1974)

(derived from Poulos and Davis, Elastic

Solutions for Soil and Rock Mechanics , 1974; and Terzaghi and Peck, Soil

Mechanics in Engineering Practice , 1967)

(NAVFAC DM 7.02, 1986)

(derived from Fang, Foundation

Engineering Handbook , 1991)

(NAVFAC DM 7.2, 1986)

Point Load in Pounds

= Unit Weight of Earth Berm

Bearing

Pressure

Earth

Berm

= Lateral Pressure in radians

ELEVATION VIEW

(see Note 3)

(see Note 3) q s

L

2B

Q p

H n

(0.16 + n

For m > 0.4:

H

= 1.77 (psf)

Q p

H m n

(m

+ n

Q p

H

H cos

(1.1) (psf)

H

H

For m ≤ 0.4:

H

= 0.20 (psf) (see Note 3)

Q l

H n

(0.16 + n

For m > 0.4:

H

= 1.28 (psf)

Q l

H m n

(m

+ n

Q l

Q p

≤ 33°

H s

≤ 15 Feet

(K)()(H s

= (K)q s

(see Note 4) q

= ( - sin cos2) (psf)

2q

= 0.25

= 0.5

= 1

L

2B

L

2B

L

2B

F I G

CA FTBR (1)

Ponderosa Bridge Replacement

Placer County, California

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Appendix A: Subsurface Explorations

Appendix A

Subsurface Explorations

CONTENTS

A.1 Introduction

A.2 Borings

A.3 Sample Classification

A.4 Soil and Rock Sampling

A.4.1 Standard Penetration Test (SPT) Samples

A.4.2 Bulk Samples

A.4.3 Rock Core Samples

Exhibits Exhibit A‐1: Photo of truck rig positioned on boring SWB‐1 location, looking northeast

Exhibit A‐2: Photo of truck rig positioned on boring SWB‐2 location, looking south

Figures Figure A‐1: Soil Description and Log Key (3 sheets)

Figure A‐2: Log of Boring SWB‐1 (3 sheets)

Figure A‐3: Log of Boring SWB‐2 (2 sheets)

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A.1 INTRODUCTION

The subsurface exploration program was conducted from October 15 to 19, 2020, and consisted of drilling and sampling two exploratory borings designated SWB‐1 and SWB‐2.

The borings were advanced at the locations shown in the Site and Exploration Plan, Figure

2. The methods used to conduct the subsurface exploration program are described below.

A.2 BORINGS

Prior to drilling the borings, we screened each boring location for utility conflicts using USA

North 811 public utility location. Boring SWB‐1 was advanced to 60.5 feet below ground surface (bgs) and located near the proposed bridge’s north abutment. Boring SWB‐2 was advanced to 37.1 feet bgs and located near the proposed bridge’s south abutment.

We retained Taber Drilling of West Sacramento, California to perform the borings. Borings were drilled using a truck mounted drill rig, as shown in the following photo Exhibits.

Exhibit A‐1 shows a close up of the rig position at boring SWB‐1 and Exhibit A‐2 shows an overview photo of the rig position at boring SWB‐2. The borings were drilled using a 4‐ inch‐diameter solid‐stem auger through the soil overburden and rock coring was used to advance the borings once bedrock was encountered. The borings were backfilled with neat cement grout up to within 5 feet bgs and the remainder of the borehole was backfilled with soil.

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Exhibit A-1: Photo of truck rig positioned on boring SWB-1 location, looking northeast.

Exhibit A-2: Photo of truck rig positioned on boring SWB-2 location, looking south.

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A.3 SAMPLE CLASSIFICATION

A representative from Shannon & Wilson observed drilling operations, logged the borings, retrieved representative soil and rock samples for laboratory testing, and prepared logs of the explorations. Soil samples were classified in general accordance with the ASTM

International (ASTM) Designation: D2488, Standard Recommended Practice for Description of Soils (Visual‐Manual Procedure)1. The system is called the Unified Soil Classification

System (USCS) and is summarized in the Soil Description and Log Key, Figure A‐1.

A.4 SOIL AND ROCK SAMPLING

Soil samples were collected during the subsurface explorations at selected borehole depths using a Standard Penetration Test (SPT) split‐spoon sampler or from drill cuttings for bulk soil samples. Rock samples were collected via continuous sampling using a double tube HQ wireline core barrel system once bedrock was encountered in the boring. The types and depths of the sampling are indicated on the boring logs presented in Figures A‐2 and A‐3.

A.4.1 Standard Penetration Test (SPT) Samples

SPTs were performed in the borings at selected depths in general accordance with ASTM

Designation: D1586, Standard Method for Penetration Testing and Split‐barrel Sampling of

Soils (ASTM, 2019). The SPT consists of driving a 2‐inch outside diameter, split‐spoon sampler a distance of 18‐inches into the bottom of the borehole with an automatic 140‐ pound hammer falling 30‐inches. The number of blows required to achieve each three 6‐ inch increments of sampler penetration is recorded and the number of blows required for the last 12‐inches of penetration is termed the Standard Penetration Resistance (N‐value).

The N‐value is an empirical parameter that provides a means for evaluating the relative density, or compactness, of granular soils and the consistency, or stiffness, of cohesive soils.

The N‐values are plotted on the boring logs.

The SPT samplers used during the penetration testing recovered disturbed samples of the soil, which were field classified and recorded on the logs by our field representative. The samples were collected in plastic jars and sealed to preserve the moisture in the sample and transported to our laboratory.

A.4.2 Bulk Samples

In addition to SPTs, a bulk soil sample was collected from near surface drill cuttings in boring SWB‐1. The approximate depth range that the sample was retrieved was estimated

1 ASTM International, 2020, Annual Book of Standards, Construction, v 4.08, Soil and Rock (I); D 1586: West Conshohocken, PA, ASTM International, 1 v.

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A.4.3 Rock Core Samples

Rock samples were collected using HQ double tube wireline coring methods (2.375‐inch nominal diameter rock core). During coring, cuttings were removed from the borehole by circulating water down through the drill rods and back up the annulus of the boring. Core runs were approximately 5 feet in length. Percent recovery and rock quality designation

(RQD) values are shown on the boring logs where coring was completed. Percent recovery is the ratio, expressed as a percent, of the length of recovered core to the total length of the core run. RQD is the ratio, expressed as a percent, of the sum of the length of intact core pieces greater than 4 inches long in a run to the total length of the core run. Following drilling, the core samples were logged by the Shannon & Wilson field representative and stored in plastic corrugated core boxes and transported to our laboratory for review and testing.

August 2021 103897-002

Ponderosa Bridge Replacement

Placer County, California

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

CONSTITUENT2

SOIL DESCRIPTION

AND LOG KEY

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. A-1

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All percentages are by weight of total specimen passing a 3-inch sieve.

2The order of terms is: Modifying Major with Minor.

3Determined based on behavior.

4Determined based on which constituent comprises a larger percentage.

5Whichever is the lesser constituent.

COARSE-GRAINED

SOILS

(less than 50% fines)1

NOTE: Penetration resistances (N-values) shown on boring logs are as recorded in the field and have not been corrected for hammer efficiency, overburden, or other factors.

PARTICLE SIZE DEFINITIONS

RELATIVE DENSITY / CONSISTENCY

Sand or Gravel 4

30% or more coarse-grained:

Sandy or Gravelly 4

More than 12% fine-grained:

Silty or Clayey 3

15% to 30% coarse-grained:

with Sand or with Gravel 4

30% or more total coarse-grained and lesser coarse-grained constituent is 15% or more:

with Sand or with Gravel 5

Very soft Soft Medium stiff Stiff Very stiff Hard

Very loose Loose Medium dense Dense Very dense

RELATIVE

DENSITY

FINE-GRAINED SOILS

(50% or more fines)1

COHESIVE SOILS

< 2 2 - 4 4 - 8

8 - 15 15 - 30

> 30

COHESIONLESS SOILS

Silt, Lean Clay, Elastic Silt, or

Fat Clay 3

PERCENTAGES TERMS 1, 2

Trace

Few

Little

Some

Mostly

WELL AND BACKFILL SYMBOLS

Bentonite Cement Grout

Bentonite Grout

Bentonite Chips

Silica Sand

Perforated or Screened Casing

S&W INORGANIC SOIL CONSTITUENT DEFINITIONS

S O

IL

_C

LA

S

S _K

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_P G

7-

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Placer County, California

GC

SC

Inorganic

Organic

(more than 50% of coarse fraction retained on No. 4 sieve)

MAJOR DIVISIONS GROUP/GRAPHIC

SYMBOL

CH

OH

ML

CL

TYPICAL IDENTIFICATIONS

Gravel

Sand

Silty Sand; Silty Sand with Gravel

Clayey Sand; Clayey Sand with Gravel

Clayey Gravel; Clayey Gravel with Sand

Sheet 2 of 3

Gravels

Primarily organic matter, dark in color, and organic odor

SW

(more than 12% fines)

Silts and Clays

Silts and Clays

(more than 50% retained on No.

200 sieve)

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

(liquid limit less than 50)

(liquid limit 50 or more)

Organic

Inorganic

FINE-GRAINED

SOILS

SM

Sands

Silty or Clayey Gravel

Silt; Silt with Sand or Gravel; Sandy or Gravelly Silt

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

HIGHLY-

ORGANIC

SOILS

COARSE-

GRAINED

SOILS

OL

(less than 5% fines)

GW

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

(less than 5% fines)

PT

FIG. A-1

(more than 12% fines)

MH

SP

GP

GM

Silty or Clayey Sand

Silty Gravel; Silty Gravel with Sand

(50% or more passes the No.

200 sieve)

SOIL DESCRIPTION

AND LOG KEY

Elastic Silt; Elastic Silt with Sand or Gravel; Sandy or Gravelly Elastic Silt

Fat Clay; Fat Clay with Sand or Gravel;

Sandy or Gravelly Fat Clay

Organic Silt or Clay; Organic Silt or Clay with Sand or Gravel; Sandy or Gravelly Organic Silt or Clay

Poorly Graded Sand; Poorly Graded Sand with Gravel

Well-Graded Sand; Well-Graded Sand with Gravel

Well-Graded Gravel; Well-Graded Gravel with Sand

Poorly Graded Gravel; Poorly Graded Gravel with Sand

Lean Clay; Lean Clay with Sand or Gravel; Sandy or Gravelly Lean Clay

Peat or other highly organic soils (see

ASTM D4427)

NOTES

1. Dual symbols (symbols separated by a hyphen, i.e., SP-SM, Sand with Silt) are used for soils with between 5% and 12% fines or when the liquid limit and plasticity index values plot in the CL-ML area of the plasticity chart.