A07.01_-_IFB_-_Atch_3_Geotech_Report_Dike_8_100__FinalGDR.pdf

Dike 8 Geotechnical Data Report Folsom Dam Raise Project Dikes 7, 8, and Mormon Island Auxiliary Dam (MIAD) Sacramento County, California

U.S. Army Corps of Engineers

Contract No. W91238-16-D-0018 Task Order W91238-18-F-0104 Mod. P00001

April 26, 2019

AECOM

2020 L Street, Suite 400 Sacramento, CA 95811 aecom.com

April 26, 2019

George Hu, PE U.S. Army Corps of Engineers, Sacramento District 1325 J Street Sacramento CA 95814

Dike 8 Geotechnical Data Report Folsom Dam Raise Project Dikes 7, 8, and Mormon Island Auxiliary Dam (MIAD), Sacramento County, California

Dear Mr. Hu, AECOM Technical Services, Inc. is pleased to present the attached Dike 8 Geotechnical Data Report for the Folsom Dam Raise Project. This report is a deliverable under Task Order W9123818F0104.

We appreciate the opportunity to be of service to the U.S. Army Corps of Engineers. Please contact the undersigned if you have any questions.

Sincerely, AECOM Technical Services, Inc.

Michael Hughes, PE Senior Project Manager

Task Order W9123818F0104 i

Table of Contents

1. Introduction

1.1 Overview

1.2 Purpose and Scope

1.3 Authorization

1.4 Coordinate System

2. Background Information

2.1 Ownership and Maintenance

2.2 Geologic and Geomorphic Setting

2.3 Construction History

2.3.1 Original Construction

2.3.2 Post-Construction Improvements

2.4 Performance History

3. Current Subsurface Investigation

3.1 Rationale for Explorations

3.2 Permitting and Utility Clearance

3.3 Field Exploration

3.3.1 Exploration and Sample Identification

3.3.2 Hand Auger Borings

3.3.3 Drilled Borings

3.3.4 Test Trenches

3.3.5 Sampling and Classification

3.3.6 Insitu Testing

3.3.7 Backfilling and Surface Restoration

3.4 Laboratory Testing

4. Previous Field Explorations

4.1 USACE Explorations 2017

5. Site Conditions

5.1 Site Topography

5.2 Subsurface Conditions

5.3 Groundwater Conditions

6. Acknowledgements and Limitations

6.1 Acknowledgements

6.2 Limitations

7. References

Task Order W9123818F0104 ii

Appendices

Appendix A - Dike 8 Construction Photos Appendix B - Laboratory Test Results on Hand Auger Samples (AECOM 2019) Appendix C - Geotechnical Data Report (SAGE 2019) Appendix D – Previous Dike 8 Borings (USACE 2017) Appendix E – Previous Dike 8 Test Trenches (USACE 2017) Appendix F – Previous Laboratory Test Data Dike 8

Figures Figure 1. Vicinity Map of Dike 8 Site Area Figure 2. Location of Dike 8 on Folsom Dam Map Figure 3. Dike 8 Location Map Figure 4. Dike 8 Typical As-Built Section Figure 5. Dike 8 Hand Auger Exploration Locations Figure 6. Dike 8 Boring and Test Trench Locations Figure 7. Historic Folsom Dam Lake Level Readings

Tables Table 1. Previous Exploration Locations

Acronyms and Abbreviations AECOM AECOM Technical Services, Inc.

bgs below ground surface CVP Central Valley Project deg degrees Folsom Dam Folsom Dam and Appurtenant Facilities GDR Geotechnical Data Report Geo-Ex Geo-Ex Subsurface Exploration JFP Joint Federal Project MIAD Mormon Island Auxiliary Dam NAD83 North American Datum of 1983 NAVD88 North American Vertical Datum of 1988 psi pounds per square inch SPT standard penetration test USCS United Soil Classification System USACE U.S. Army Corps of Engineers USBR U.S. Bureau of Reclamation

Task Order W9123818F0118

1. Introduction This Geotechnical Data Report (GDR) presents the results of a geotechnical investigation by AECOM Technical Services, Inc. (AECOM) completed between October 2018 to February 2019 and summarizes results of previous pertinent investigations. This GDR will be used in support of geotechnical problem identifications, alternatives evaluations, and geotechnical design of improvements to Dike 8, which are part of the Folsom Dam Raise Project. Dike 8 is an earthen embankment that is part of a larger system of dikes and dams that form Folsom Dam and Appurtenant Facilities (Folsom Dam) in Sacramento County, California. The U.S. Army Corps of Engineers (USACE) retained AECOM Technical Services, Inc.

(AECOM) to design a 3.5-foot raise for Dike 8 as part of system wide improvements to the dams and dikes of Folsom Dam with the primary purpose to provide flood risk reduction along the American River downstream of Folsom.

1.1 Overview

Folsom Dam is located on the main stem of the American River approximately 29 miles upstream from the City of Sacramento (Figure 1). It is a multipurpose dam owned and operated by the U.S. Bureau of Reclamation (USBR) as part of the Central Valley Project (CVP). The USACE prescribes storage requirements for flood risk management purposes at the dam. Folsom Dam is a multiuse facility authorized for flood risk management, fish & wildlife, water quality, water supply, hydroelectricity, recreation, and navigation. However, it is primarily operated to maximize flood risk management and water supply benefits.

Folsom Dam consist of four dams (Main Concrete Dam, Mormon Island Auxiliary Dam, Right-Wing Dam, and Left-Wing Dam, and 8 dikes (Dikes 1 through 8), which impound flows on the American River, forming Folsom Lake (Figure 2). Folsom Dam has an impound capacity of 977,000 acre-feet with a surface area of 11,450 acres.

Dike 8 is an earthen embankment near the southern end of Folsom Lake that spans a gently sloping saddle in the reservoir rim. The existing embankment has a crest length of about 740 feet, a height of up to 21 feet, and an approximate crest elevation of 482.84 feet, North American Vertical Datum of 1988 (NAVD88). An aerial image of Dike 8 is shown on Figure 3.

1.2 Purpose and Scope

Field investigation for this GDR entailed collecting geotechnical information to supplement existing data.

The new and existing geotechnical data will be used in support of AECOM’s design of the improvements to Dike 8.

AECOM’s scope of work for this GDR included:

Reviewing existing historical geotechnical information and summarizing pertinent data in an inventory.

Performing 15 hand auger borings along the downstream and upstream slopes of Dike 8.

Performing 5 test trenches along the downstream toe and the fill area near the left abutment.

Performing 3 borings at the abutments and downstream toe and performing borehole permeability testing.

Performing geotechnical laboratory testing of selected samples collected from the hand auger borings and test trenches.

Preparing this GDR.

1.3 Authorization

USACE authorized the work described in this GDR for under Contract W91238-18-D-0018, dated September 30, 2016, and Task Order W92138-18-F-0104, dated September 21, 2018.

1.4 Coordinate System

Unless noted otherwise, all elevation references in this GDR are in feet based on the North American Vertical Datum of 1988 (NAVD88). The horizontal datum is the North American Datum of 1983 (NAD83).

Survey data, elevations and horizontal coordinates are in feet based on California State Plane, Zone 2.

Figure 1. Vicinity Map of Dike 8 Site Area.

Figure 2. Location of Dike 8 on Folsom Dam Map.

Figure 3. Dike 8 Location Map.

2. Background Information

2.1 Ownership and Maintenance

Folsom Dam is owned and operated by the U.S. Bureau of Reclamation (USBR) as part of the Central Valley Project (CVP). The USACE prescribes storage requirements for flood risk management purposes at the Dam.

2.2 Geologic and Geomorphic Setting

Geologically, the project area is located between the Sierra Nevada and the Central Valley Geomorphic Provinces. The Sierra Nevada geomorphic province is characterized by a north-northwest trending mountain belt with extensive foothills on the western slope. The Folsom Lake region primarily consists of rolling hills and upland plateaus between major river canyons. There are three major geologic divisions within the study area. The oldest consists of a north-northwest trending belt of metamorphic rocks, into which younger granitic plutons have intruded and obliterated some of the metamorphic belt. The youngest geologic division consists of relatively flat deposits of volcanic ash, debris flows, and alluvial fan deposits.

These deposits overlie the older rocks.

Igneous, metamorphic, and sedimentary rock types are present within the Folsom Lake area. The four major rock types present in the Folsom Lake area are: (1) ultramafic intrusive rocks, (2) metamorphic rocks, (3) granodiorite intrusive rocks, and (4) volcanic mud flows.

Metamorphic rocks of the amphibolite series underlie the entire saddle at Dike 8. Bedrock consists of meta-basalts and meta-tuffs, and schistose rocks that are locally intruded by narrow dikes of aplite and quartz (USACE, 1955a). Prominent schistosity strikes N 43o to 64o E and dips 76o to 80o SE. Joints traversing the bedrock are short and generally filled in their upper reaches with red, plastic clay. All are bounded by a zone of iron-stained schist. The adjacent schist is layered and soft. Thin aplite dikes, less than 0.2-foot wide, locally intrude the schist at attitudes paralleling the planes of schistosity.

2.3 Construction History

2.3.1 Original Construction

The original construction of Dike 8 began in April of 1954 and was completed November 1954.

Construction was performed by Merritt, Chapman, Scott Corporation and Salvin Construction Corporation under Contract DA-04-167-eng-671 (USACE, 1955b). Dike 8 fills in a low topographic saddle; the center of which is divided into two inner saddles. Construction photographs are presented in Appendix A for reference.

Following stripping, cutoff trench excavation was performed through weathered bedrock (fine grained amphibolite schist) using the Euclid Scrapers until equipment refusal was met. This resulted in an average depth of the cutoff trench of about 4 feet below the stripped surface (USACE, 1955a). Available as-built drawings show the key trench was about 12 feet wide and has 1 horizontal to 1 vertical (1H:1V) side-slopes. A total of about 5,424 cubic yards of overburden were stripped from the foundation. Another approximately 2,300 cubic yards of material was excavated during the cutoff trench excavation (USACE, 1955b). Groundwater was not encountered during excavation (USACE, 1955a). No foundation grouting was performed below the cutoff trench. Figure 4 shows a typical cross section from the as-built drawings.

Figure 4. Dike 8 Typical As-Built Section

Existing documentation indicates foundation rock in the stripped foundation was platy, which precluded scarifying and recompacting the subgrade. Instead, initial lifts of embankment fill were placed in 6 to 9-inch lifts directly on top of the stripped subgrade and compacted with 8 or more passes with a 42,000 pound sheepsfoot roller. The initial lifts were compacted to densities that averaged 96 percent relative compaction (based on modified compaction effort (ASTM D1557)) at an average moisture content of

9 percent (USACE, 1955a). Field compaction records from the remaining embankment fill placement at Dike 8 are not available.

2.3.2 Post-Construction Improvements

No known improvements to the existing embankment at Dike 8 have been constructed after the original construction. However, as part of improvements to other Folsom Dam facilities as part of the JFP project, a haul road (referred to as the bench road) was constructed about 150 feet upstream (north) of Dike 8.

The top of the bench road is at the Gross Pool Elevation (Elevation 468.34 feet, NAVD88). In addition, waste fill from the JFP project was disposed along the upstream slope of Dike 8 between the bench road and the Dike 8 crest. Information regarding waste fill material, including gradations, compaction methods, density and other construction records from the waste fill placement are not available. Furthermore, it is not known if the existing rock slope protection was removed from the upstream face of Dike 8 prior to placement of waste fill. Test trenches performed in the waste fill by USACE in 2017 indicate the materials were primarily visually classified as clean sands with varying amounts of cobbles and boulders (see Section 4.0 for more information about test trenches). The waste fill was placed from the existing Dike 8 crest down to the bench road at a slope of approximately 13H:1V.

2.4 Performance History

There have been no reports of past seepage, slope instability, erosion, or other adverse performance of the Dike 8 embankment. However, the gross pool elevation is at or below the upstream embankment toe elevation, so Dike 8 is not regularly loaded. Based on historic records between 2005 and 2016, the reservoir water surface elevation has been between approximately elevation 462 feet and 467 feet NAVD88 only 6 times and has not risen above the Gross Pool elevation of 468.34 feet NAVD88.

3. Current Subsurface Investigation AECOM performed field investigation for the Dike 8 portion of the Folsom Dam Raise Project from October 2018 to February 2019. This work involved an initial phase of hand auger explorations completed by AECOM in October 2018 and a subsequent phase of borings and test trenches completed in February 2019 under the supervision of SAGE Engineers (SAGE), a sub-consultant to AECOM.

The initial phase of investigation consisted of 15 hand auger borings to depths of 1.5 to 2.0 feet below ground surface (bgs). Eight hand augers were undertaken in the waste fill along the upstream face of the dike and 7 along the downstream slope of the dike (Figure 5).

Figure 5. Dike 8 Hand Auger Exploration Locations

The subsequent phase of investigation supervised by SAGE consisted of 3 borings to depths of 14.5 to

20.0 feet and 5 test trenches to depths of 4 to 9 feet bgs. Borings were located at the abutments at either end of the dike crest and at the dike toe. Test trenches were located along the dike toe (3 trenches) and in an area of fill downstream of the left abutment (2 trenches). Boring and trench locations are shown in Figure 6.

Figure 6. Dike 8 Boring and Test Trench Locations

3.1 Rationale for Explorations

Exploration locations were selected by AECOM at targeted locations to:

Collect shallow hand auger samples from downstream and upstream slopes of the existing embankment for filter design calculations.

Evaluate embankment and foundation conditions.

Evaluate suitability for reuse of soils during dike improvements.

Collect samples of foundation soils from the dike toe and adjacent fill area for geotechnical index property testing; this information will be used to support design of the dike 8 improvements.

3.2 Permitting and Utility Clearance

AECOM obtained the following approvals prior the start of Dike 8 field explorations:

Drilling Program Plan from the USACE.

Permits to Work from the Central California Area Office of the USBR.

Exploration locations were visually inspected for the presence of overhead and underground utilities. The locations were then staked and marked with white paint. Underground Service Alert was contacted a minimum of 48 hours prior to the start of exploration activities. An Underground Service Alert ticket number (including clearance date, expiration date and call-back-to-extend date) was obtained for each planned exploration location and was documented in the project file.

Proximity to overhead utilities was evaluated at each exploration location to maintain a clearance of at least 15 feet between the equipment and any overhead utilities (i.e., power lines).

3.3 Field Exploration

Field investigations as part of the current investigation for the raise of Dike 8 include hand auger borings, borings and test trenches. Results of laboratory testing on hand auger boring samples are presented in Appendix B. Details of the borings and test trenches, performed under the supervision of SAGE, are presented in a standalone Geotechnical Data Report prepared by SAGE (Appendix C).

3.3.1 Exploration and Sample Identification

At field program startup, each exploration was assigned a unique number by AECOM to differentiate it from previously completed exploration programs.

Samples were identified and labeled with the applicable exploration and sample numbers. Descriptions of exploration numbering and sample identification protocols are provided below.

Explorations were identified according to the following protocol:

HA – 8 – 101 – Hand auger at Dike 8 reference number 101

B – 8 – 101 – Boring at Dike 8 reference number 101

TT – 8 – 101 – Test trench at Dike 8 reference 101

3.3.2 Hand Auger Borings

Hand auger borings were performed at 15 locations on the upstream and downstream slopes of Dike 8 by AECOM in October 2018. The hand auger borings were advanced to depths of 1.5 to 2 feet bgs. Hand auger samples were sent to AECOM’s laboratory to perform gradation and Atterberg limits test.

Laboratory test results are presented in Appendix B.

3.3.3 Drilled Borings

Borings were performed in January and February 2019 in accordance to the USACE approved Drilling Program Plan and USBR approved Permit to Work. Drilling was performed by Geo-Ex Subsurface Exploration (Geo-Ex) of Dixon, California and supervised by SAGE, a sub-consultant to AECOM.

Laboratory testing was not performed on samples collected from the borings. Details of the field investigation, including copies of borings logs, are presented in a Geotechnical Data Report prepared by SAGE (Appendix C).

3.3.4 Test Trenches

Test trenches were excavated in January and February 2019 by AECOM and logged by SAGE. Borings logs and details of the field investigation are presented in Appendix C. Selected samples from the test trenches were sent to AECOM’s laboratory to perform gradation, Atterberg limits and compaction testing.

Laboratory test results on samples retrieved from the trenches are presented in Appendix C.

3.3.5 Sampling and Classification

Materials from the explorations were logged in general conformance with ASTM D2488. The logs were subsequently reviewed and updated as needed per ASTM D2487 (Unified Soil Classification System) based on laboratory testing results of select samples.

3.3.6 Insitu Testing

A falling head permeability test was performed in boring B-8-102 between the ground surface and a depth of 5 feet and packer tests were performed in all three borings in the weathered amphibolite schist. Details of the testing and results are presented in Appendix C.

3.3.7 Backfilling and Surface Restoration

Hand auger explorations were backfilled with hydrated bentonite pellets and the top 1 foot covered with native soils to match the existing grade. Borings were backfilled with neat cement grout to match existing grade. Test trenches were backfilled using excavated material compacted in approximately 6 to 12 inch loose lifts using a sheep’s foot roller. The surface of the backfilled trenches was seeded and covered with hay for erosion protection.

3.4 Laboratory Testing

Laboratory testing was performed on selected samples from hand auger borings and test trenches.

Testing included:

Compaction testing (ASTM D698)

Sieve Analyses (ASTM D422)

Atterberg Limits (ASTM D4318)

Results of laboratory testing are presented in Appendix B and Appendix C

4. Previous Field Explorations Previous investigation at Dike 8 include soil borings, test trenches, and laboratory testing, details of which are discussed in this section and summarized in Table 1. Relevant extracts from previous investigation and laboratory test reports are presented in Appendix D (Borings), Appendix E (Trenches) and Appendix F (Laboratory Testing).

Previous investigations for Dike 8 include those performed by USACE in 2017, as part of a larger investigation program for the Folsom Dam Raise Project, which the Right and Left Wing Dams, Dike 7 and 8 and Mormon Island Auxiliary Dam. Details of borings undertaken as part of these investigations are presented in the Technical Memorandum Exploratory Drilling Program – Folsom Dam Raise Work Package No. 2 - Right Wing Dam, Left Wing Dam, Dikes 7, 8 & Mormon Island Auxiliary Dam, dated August 2018. Details of trenches undertaken as part of these investigations are presented in the Technical Memorandum Trenching Program Folsom Dam Raise Work Package No. 2 - Dikes 7&8, dated July 2018. Details of laboratory testing are presented in the Folsom Dam Raise Material Properties for Dikes 7 & 8 and MIAD Report, dated August 2018.

4.1 USACE Explorations 2017

In November 2017, USACE’s Omaha District drilled 3 hollow stem auger borings from the Dike 8 crest to depths ranging from 19.3 to 20.3 feet below the top of the embankment. Each boring extended at least 10 feet into the dam foundation and encountered clayey sand and silty sand embankment fill founded on weathered amphibolite. A location plan and copies of the borings logs are presented in Appendix D.

Sampling consisted of alternating Standard Penetration Test (1.375 inch inside diameter) and California Modified (2.5 inch inside diameter) drive samples taken at 2.5-foot intervals. Selected samples collected from these borings were tested by USACE’s Savannah District geotechnical laboratory. The geotechnical testing included:

Grain Size Distribution

Atterberg Limits

Moisture Content

Unit Weight

Hydraulic Conductivity

Direct Shear

Consolidated Undrained Compressive Strength

Engineering property tests (hydraulic conductivity, unit weight, direct shear and consolidated undrained compressive strength) were run on the relatively undisturbed California Modified samples, whereas index property tests (gradation, Atterberg Limits and moisture content) were run on both disturbed and relatively undisturbed samples. Results of laboratory testing are presented in Appendix F.

In addition to the auger borings, USACE performed 8 test trenches: three trenches along the downstream toe; three trenches along the upstream waste fill slope; and one trench at each abutment (Appendix E).

Near the abutments, the test trenches were excavated to depths of between 4.5 feet and 6 feet. Along the downstream toe, the test trenches were excavated to depths ranging from 5 to 8 feet. Along the upstream waste fill slope, the test trenches were excavated to 3.5 to 9 feet deep. No laboratory testing was performed on samples from the test trenches.

Table 1. Previous Exploration Locations

Exploration ID Exploration Location

Date Completed

Exploration Type

Drilling / Backhoe

Contractor

Approximate Surface

Elevation (ft) Depth

(ft) Length

(ft) Groundwater

Depth (ft) Northing, Easting (ft)1

2F-18-4 Dike Crest 11/15/2017 Boring USACE 483.0 21.4 N/A N/E2 2015494.3, 6808944.6

2F-18-5 Dike Crest 11/17/2017 Boring USACE 483.0 19.3 N/A N/E 2015489.4, 6809106.7

2F-18-6 Dike Crest 11/28/2017 Boring USACE 483.1 29.3 N/A N/E 2015485.6, 6809287.9

4F-17-48 (D8-T-4) Upstream of Embankment 08/24/2017 Test Trench Geo-Ex 479.7 13.5 9.5 N/E 2015538.9, 6809227.3

4F-17-49 (D8-T-3) Upstream of Embankment 08/24/2017 Test Trench Geo-Ex 480.0 9.0 4.0 N/E 2015540.6, 6809101.7

4F-17-50 (D73-T-2) Upstream of Embankment 08/24/2017 Test Trench Geo-Ex 479.2 8.0 3.5 N/E 2015548.5, 6808935.7

4F-17-51 (D8-T-1) Abutment 08/24/2017 Test Trench Geo-Ex 483.8 9.0 4.5 N/E 2015505.8, 6808691.5

4F-17-52 (D8-T-5) Abutment 08/25/2017 Test Trench Geo-Ex 484.3 6.0 10.0 N/E 2015499.1, 6809492.3

4F-17-53 (D8-T-6) Downstream of Embankment 08/25/2017 Test Trench Geo-Ex 470.4 10.1 6.0 N/E 2015451.2, 6808933.7

4F-17-54 (D8-T-7) Downstream of Embankment 08/25/2017 Test Trench Geo-Ex 475.8 10.0 7.4 N/E 2015454.6, 6809199.2

4F-17-55 (D8-T-8) Downstream of Embankment 08/25/2017 Test Trench Geo-Ex 463.7 10.0 5.0 N/E 2015430.9, 6809288.9

1 Borehole or test trench coordinates (California State Plane, Zone 2) 2 Not encountered 3 D7 is stated on the trench log, but is considered a typo and should be D8

5. Site Conditions

5.1 Site Topography

The existing embankment at Dike 8 spans a gently-sloping saddle, the center of which is divided into two inner saddles. The crest of the existing embankment is at approximately elevation 482.8 feet NAVD88.

The existing downstream elevation is approximately 462 feet NAVD88 at the left4 inner saddle and approximately 469 feet NAVD88 at the right inner saddle. Downstream of the existing dike toe, the ground gently slopes south at a 5 to 10 percent grade toward an existing church property on a raised building pad approximately 200 feet from the downstream toe. A stormwater pipe collects surface water runoff from the area between Dike 8 and the Church property and directs it to a detention basin. The hillslopes to the east and west of the existing dike crest are sloped at approximately 5H:1V along the left abutment and 2.5H:1V along the right abutment.

As part of the Dike 8 raise project, AECOM hired Telamon, Inc. to complete a topographic survey of the Dike 8 area. Telamon’s field survey was completed in 10/15/18 and is the basis of the elevations for all field explorations completed during the current investigation.

5.2 Subsurface Conditions

In general, excavations performed in the waste fill on the upstream side of the dike encountered sand with silt and clay with a fines content of less than 10%. The waste fill also contains cobble and boulders and has a maximum thickness of approximately 6.5 feet based on test trench excavations. Waste fill overlies approximately 1 to 2.5 feet of silt/lean clay, with weathered amphibolite schist beneath.

Borings in the embankment encountered medium dense to very dense silty sand and clayey sand to depth of between 8 and 19 feet, overlying weathered amphibolite schist. At the right abutment, weathered amphibolite was encountered at a depth of 2 feet and at the left abutment weathered amphibolite was encountered at the ground surface.

Hand auger explorations performed on the downstream embankment of the dike encountered primarily clayey and silty sands with an average fines content of between 16% and 21% below a depth of 1.0-foot.

The upper one foot of the embankment slope was covered with surface protection consisting of poorly-graded gravel.

Boring and test trench explorations located at the downstream toe encountered weathered amphibolite schist bedrock beneath approximately 0 to 4 feet of overburden soils.

Test trenches performed in the area of fill to the south of the left abutment (placed to create a turning circle for traffic) indicated fill to a depth of greater than 9 feet.

5.3 Groundwater Conditions

No groundwater monitoring instrumentation has been installed at Dike 8. No groundwater was encountered in the explorations completed as part of the current investigation, that was conducted in late January/early February during a period of heavy rainfall. None of the explorations completed by USACE in November 2017, encountered groundwater.

Groundwater conditions at Dike 8 are likely influenced by lake level, precipitation and land use. Historic data from the Department of Water Resources shows that the lake level has not risen above elevation

465.51 feet National Vertical Geodetic Datum of 1929 (467.85 feet North American Vertical Datum 1988) since 1990 (Figure 7).

4 Left and right are denoted assuming a downstream (southerly) direction.

Figure 7. Historic Folsom Dam Lake Level Readings

6. Acknowledgements and Limitations

6.1 Acknowledgements

AECOM’s key team members for preparation of this report are listed below:

Ken Myers, PE: Task Order Manager

Mike Hughes, PE: Senior Project Manager

Rich Millet, PE, GE: Senior Technical Reviewer

Dmitriy Lukashov, GIT: Geologist

Subcontractors used by AECOM for this work include:

Geo-Ex: Drilling

SAGE: Field Supervision and Logging

This report was prepared in coordination with SAGE. AECOM would like to thank them for support for this

GDR.

SAGE

Darren Mack, PE: Principal Engineer

Jerry Pascoe, PE: Principal Engineer

Zack Washburn, PG, CEG: Senior Engineering Geologist

Alma Luna, PE: Senior Project Geotechnical Engineer

6.2 Limitations

Fieldwork and reporting conducted for the current investigation have been performed in accordance with the standard of care commonly practiced in the engineering profession. Standard of care is defined as the ordinary diligence exercised by fellow practitioners in this area performing the same services under similar circumstances during the same time period.

Discussions of subsurface conditions summarized in this report are based on subsurface information at limited exploration locations and at limited times. Variations in subsurface conditions almost certainly exist between exploration locations and between times, and AECOM may not be able discern or present all adverse conditions in the levee and its foundation.

No warranty, express or implied, is made in the furnishing of this report. AECOM makes no warranty, express or implied, that actual encountered site and subsurface conditions will exactly conform to the conditions described herein, or that interpretations and recommendations in this report will be sufficient for all construction planning aspects of the work. AECOM does not attest to the accuracy, completeness, or reliability of geotechnical borings and other subsurface data by others that are included or referenced in this report. AECOM has not performed independent validation or verification of data by others.

Data presented in this report are time-sensitive in that they apply only to locations and conditions existing at the time of the exploration or collection of the data. Data should not be applied to any other projects in or near the area of this study; nor should they be applied at a future time without appropriate verification.

This report is for the use and benefit of USACE and their consultants in connection with the execution of the Dike 8 raise portion of the Folsom Dam Raise Project. Use by any other party is at their own discretion and risk.

7. References SAGE, 2019. Geotechnical Data Report, Folsom Dam Raise – Dike 8, Sacramento County, California.

USACE, 2018. Technical Memorandum to File, Exploratory Drilling Program – Folsom Dam Raise. Work Package No. 2 – Right Wing Dam, Left Wing Dam, Dikes 7 & 8, Mormon Island Auxiliary Dam, Sacramento County, California. August

USACE, 2018. Technical Memorandum to File, Trenching Program – Folsom Dam Raise. Work Package 2 – Dikes 7 & 8, Sacramento County, California. July

USACE, 2018. Folsom Dam Raise Material Properties Report for Dikes 7 & 8 and MIAD, Sacramento County, California. July

Appendix A - Dike 8 Construction Photos michael.hughes02 Stamp michael.hughes02 Stamp michael.hughes02 Text Box View of Upstream Slope of Dike 8 - Looking Southwest (June 29, 1954) michael.hughes02 Text Box michael.hughes02 Text Box View of Along Dike 8 Crest - Looking West (June 29, 1954) michael.hughes02 Text Box View of Along Dike 8 Crest - Looking East (June 29, 1954) michael.hughes02 Stamp michael.hughes02 Stamp michael.hughes02 Text Box View of Along Dike 8 Crest - Looking East (November 10, 1954) michael.hughes02 Text Box View of Along Dike 8 Crest - Looking West (November 10, 1954) michael.hughes02 Text Box View of Along Dike 8 Crest - Looking East (June 23, 1955)

Appendix B - Laboratory Test Results on Hand Auger Samples

(AECOM 2019)

Gradation Data Upstream Slope

Mesh Dia (mm)

75 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 50 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

37.5 84.1 100.0 100.0 100.0 100.0 91.3 100.0 100.0 87.6 100.0 100.0 100.0 25 84.1 90.2 100.0 100.0 100.0 89.5 100.0 100.0 87.6 93.9 100.0 100.0 19 84.1 90.2 98.3 100.0 100.0 85.7 100.0 100.0 87.6 92.4 100.0 100.0

12.5 81.8 89.5 95.6 100.0 96.0 83.5 100.0 97.6 86.4 91.1 96.4 97.7

9.5 80.3 89.1 95.0 98.1 93.2 82.6 97.7 96.0 85.2 90.0 94.3 95.7

4.75 78.0 85.3 89.3 89.6 83.4 76.6 92.0 89.7 78.7 83.5 85.6 88.6 2 73.8 64.7 66.0 67.7 62.5 58.9 70.6 67.5 59.5 61.7 61.8 64.0

0.85 68.4 43.1 44.1 48.1 44.1 41.5 49.6 46.8 41.1 41.6 41.7 43.1

0.425 64.0 29.7 30.8 33.8 30.7 28.5 35.2 32.8 29.6 29.3 29.5 30.1

0.25 59.9 21.0 21.7 24.0 21.3 19.7 24.7 23.4 21.5 21.2 21.2 21.7

0.15 55.5 14.7 15.2 16.8 14.6 13.2 17.2 16.3 15.5 15.2 14.9 15.3

0.106 51.9 11.3 11.8 13.0 11.1 9.9 13.2 12.6 12.3 12.0 11.6 11.9

0.075 48.1 9.1 9.4 10.4 8.7 7.6 10.5 10.0 10.0 9.6 9.2 9.4

Gradation Data Downstream Slope

Mesh Dia (mm)

75 100.0 100.0 100.0 100.0 100.0 100.0 100.0 50 100.0 100.0 100.0 100.0 100.0 100.0 100.0

37.5 100.0 100.0 100.0 100.0 100.0 100.0 100.0 25 100.0 100.0 100.0 100.0 100.0 100.0 100.0 19 100.0 100.0 96.5 100.0 100.0 100.0 100.0

12.5 100.0 100.0 96.0 100.0 98.9 100.0 97.9

9.5 99.5 98.5 94.9 100.0 98.6 98.9 96.1

4.75 98.5 94.0 91.1 98.3 98.4 98.5 86.4 2 86.3 81.1 80.6 86.4 92.8 88.9 74.0

0.85 66.2 61.2 61.7 67.7 77.7 68.1 51.7

0.425 52.1 47.6 49.1 52.1 63.8 53.0 38.4

0.25 39.7 37.5 38.7 39.8 50.1 41.2 29.8

0.15 28.9 28.7 29.8 29.3 38.8 30.9 23.2

0.106 22.9 23.6 24.6 23.0 32.3 25.0 19.4

0.075 18.7 19.7 21.0 18.1 27.9 20.6 16.5

H-8-106 (1.5-2.0 ft)

H-8-107 (1.0-1.5 ft)

H-8-107 (1.5-2.0 ft)

H-8-108 H-8-109 H-8-110 H-8-111 H-8-112 H-8-113 H-8-114

H-8-101 H-8-102

(1.0-1.5 ft) H-8-102

(1.5-2.0 ft) H-8-103 H-8-103A H-8-104

H-8-105 (1.0-1.5 ft)

H-8-105 (1.5-2.0 ft)

H-8-106 (1.0-1.5 ft)

\\sacdata01.us.ie.urs\Projects6\US Army Corps\W91238-16-D-0018-Dikes7-8.MIAD\Working Files\Dike 8\100 Percent\GDR\Appendices\Appendix D\HandAuger Samples-GSD-Dike 8.xlsx

Dike 8 Gradation Results for Upstream Slope

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GRAVEL SAND SILT AND CLAY

COARSE FINE COARSE FINEMEDIUM

HYDROMETER

Dike 8 Gradations Downstream Slope

\\sacdata01.us.ie.urs\Projects6\US Army Corps\W91238-16-D-0018-Dikes7-8.MIAD\Working Files\Dike 8\100 Percent\GDR\Appendices\Appendix D\HandAuger Samples-GSD-Dike 8.xlsx

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GRAVEL SAND SILT AND CLAY

COARSE FINE COARSE FINEMEDIUM

HYDROMETER

DESCRIPTION / CLASSIFICATION

● H-8-108 B-1_1.0-2.0 1.0-2.0 10.7 25 4

▪ H-8-109 B-1_1.5-2.0 1.5-2.0 9.3 27 8 u H-8-110 B-1_1.5-2.0 1.5-2.0 9.6 29 10

H-8-111 B-1_1.5-2.0 1.5-2.0 13.3 26 3

H-8-112 B-1_1.5-2.0 1.5-2.0 12.3 30 15

H-8-113 B-1_1.5-2.0 1.5-2.0 11.7 28 7

H-8-114 B-1_1.5-2.0 1.5-2.0 5.6 32 13

Project Name: PLASTICITY CHART

Project Number:

Folsom Dam Raise - Dike 8

60585093

Brown Clayey SAND (SC)

Boring Number Sample Number

Depth (ft) Water Content

LL

Dark yellowish brown Silty,Clayey SAND (SC-SM)

Dark yellowish brown Clayey SAND (SC)

PI

Dark yellowish brown Silty SAND (SM)

Dark yellowish brown Clayey SAND (SC)

Dark yellowish brown Clayey SAND (SC)

Olive Silty SAND (SM)

CL-ML

CL or OL CH or OH

ML or OL MH or OH

0 10 20 30 40 50 60 70 80 90 100 110

P L

A S

T

IC

IT

Y

I N

D E

X

LIQUID LIMIT (%)

Atterberg Limits Summary Plot.xlsx AECOM

Appendix C - Geotechnical Data Report (SAGE 2019)

2251 Douglas Blvd., Ste. 200, Roseville, CA 95661, (916) 677-4800 1 Kaiser Plaza, Ste. 1125, Oakland, CA 94612, (510) 701-2266

865 Aerovista Pl. Ste. 230, San Luis Obispo, CA 93401, (805) 439-3666 SAGEengineers.com

March 8, 2019 Project No. 18-072.00

Mr. Michael Hughes

2020 L Street, Suite 400 Sacramento, CA 95811

Re: GEOTECHNICAL DATA REPORT Folsom Dam Raise – Dike 8 Sacramento County, California

Dear Mr. Hughes:

SAGE Engineers, Inc. (SAGE) is pleased to submit this Geotechnical Data Report (GDR), which summarizes our field investigation activities and subsurface observations for the Folsom Dam Raise project at Dike 8 (Project). SAGE also performed geotechnical investigations at other locations around Folsom Reservoir as a part of the Folsom Dam Raise project; a separate GDR will be provided for each location.

BACKGROUND

Folsom Reservoir is a multipurpose facility operated by the U.S. Bureau of Reclamation (USBR). The main concrete gravity dam is flanked by two earthen wing dams. In addition, there is an auxiliary dam (Mormon Island Auxiliary Dam) and eight smaller earthfill saddle dikes (See Figure 1). The Folsom Dam Raise Project will modify these facilities to increase flood storage capacity. The principal modifications include raising the crest elevations of the left and right-wing dams, Mormon Island Auxiliary Dam (MIAD), and the saddle dikes by 3.5 feet. Modifications to the main dam spillway will also be made to enhance the utilization of the increased flood storage capacity.

Dike 8 is located on the southern end of Folsom Reservoir in Folsom, California. Further information regarding the embankment including size, geometry, original construction dates, and anticipated material composition can be found in the Design Documentation Report (DDR), Folsom Dam Raise Project Dike 8, prepared by AECOM, dated November 21, 2018 (65% Draft).

SCOPE OF WORK

The geotechnical investigation was performed in general accordance with the statement of work listed in the Project contract documents (AECOM Task Order 105770 Mod 02 dated February 18, 2019), which included providing geotechnical support for the planning and supervising of field investigation work necessary for design of Dikes 1 through 8 and MIAD. The field investigation included logging exploratory test trenches and borings, as well as performing falling head and packer permeability testing. Specifically, the scope included the following tasks:

Geotechnical Data Report

Project No. 18-072.00

Exploratory Trenches Marking USA and coordinating utility clearances;

Logging test trenches;

Collecting representative bulk bag samples from each identified soil stratum;

Taking photographs of the side wall of the trench and excavated materials;

Preparing hand-drafted logs and supplying copies to AECOM; and

Delivering bulk samples to the AECOM office in Sacramento.

Exploratory Boreholes Marking USA and coordinating utility clearances;

Logging borings;

Collecting representative samples of the soil and bedrock encountered using Standard Penetration Test (SPT), Modified California (Mod Cal), and HQ Core samplers and placing rock core, in the sequence recovered, in core boxes;

Taking photographs of rock core samples;

Conducting falling head and packer permeability tests in rock borings;

Preparing hand-drafted logs and supplying copies to AECOM; and

Delivering soil samples and rock core to AECOM office in Sacramento.

FIELD INVESTIGATION

Subsurface conditions at Dike 8 were explored by drilling three test borings, excavating five test trenches, and performing falling head and packer permeability tests in the drilled borings. Boring and trench coordinates were provided in the Drilling Program Plan (DPP) prepared by AECOM dated January 31, 2019, and revised February 15, 2019. SAGE field representative(s) located the boring and test trenches using a Trimble GeoExplorer XT 6000/7000 hand-held Global Positioning System (GPS) with an external antenna, which is capable of sub-meter accuracy. The locations of the exploratory boreholes and test trenches are shown on Figure 2. Details of the field exploration activities are described in the remainder of this section.

Borings Three test borings were drilled to evaluate the subsurface conditions at Dike 8, designated as B-8-101 through B-8-103. The borings were drilled between January 31st and February 1st, 2019 by Geo-Ex Subsurface Exploration of Dixon, California. The borings were drilled under the direction of a SAGE field representative(s) to the maximum depths below ground surface (bgs) shown in the table below and in general accordance with the DPP.

Boring Maximum Depth (ft bgs) B-8-101 14.5 B-8-102 19.8 B-8-103 20.0

Project No. 18-072.00

The borings were advanced using a truck-mounted CME-75 drill rig equipped with 4.5-inch-diameter solid flight augers. During drilling, the SAGE field representative logged the materials encountered and obtained samples for visual classification and laboratory testing. Logs of the borings are presented in Appendix A.

Soil samples were obtained using a SPT sampler with a 2.0-inch outside diameter and 1.5-inch-inside diameter without liners and a Mod Cal sampler with a 3.0-inch-outside diameter and 2.43-inch-inside diameter driven with liners. The samplers were driven with a 140-pound, auto-safety hammer falling 30 inches. The hammer blows required to drive the sampler each 6-inch increment of the 18-inch drive (uncorrected blow count) are shown on the boring logs in Appendix A. Where sampler refusal occurred, the number of hammer blows and the corresponding depth of penetration (in inches) was recorded.

Once the augers were advanced through the overburden, the borings were advanced an additional 10 to 15 feet into bedrock using wire-line rock coring methods using HQ-diameter cores. During rock core logging, fractures (mechanical or natural) in the rock were recorded, and voids and core losses were marked with Styrofoam blocks as well as on the logs. Rock cores were carefully handled and preserved in wooden core boxes. Photographs of the core boxes are attached in Appendix C.

After completion of the borings, the holes were backfilled with neat cement grout.

Falling Head Test Falling head permeability testing was performed at borehole B-8-102 on February 1, 2019. The test consisted of drilling a second hole immediately adjacent to boring B-8-102 to a depth of five feet, filling the hole with water, and recording the water level at specified time intervals. The test hole was backfilled with cement-bentonite grout at the completion of the test. The falling head permeability test log is provided in Appendix B.

Packer Test Borehole permeability tests were conducted using the single packer method in each borehole on January 31st and February 1st, 2019. The tests were performed at about 8½ feet below the ground surface in B-8- 101, at 15 feet in B-8-102 and at 15 feet in B-8-103. Test interval lengths were 6 feet, 4.8 feet, and 5 feet for boreholes B-8-101, B-8-102, and B-8-103, respectively.

Prior to performing the permeability testing, each borehole was conditioned by circulating clear water to remove cuttings and polymer-based drilling fluid. For each interval, a maximum test pressure (Pmax) of approximately 1 psi/foot of depth to the center of the test section was used to reduce the potential for hydrofracturing in the formation.

Testing generally followed the steps laid out in the Ground Water Manual (USBR, 1995), which consisted of a five-step test at varying pressures approximately equal to ½ Pmax, ¾ Pmax, Pmax, ¾ Pmax, and ½ Pmax. At each step, the pressure was held constant until a steady rate of flow could be maintained, which was then monitored for 20 minutes for the first three steps and five minutes for the last two steps. At the completion of the fifth step, the packer was deflated and removed from the borehole. The packer test logs and falling head test documentation are provided in Appendix B.

Test Trench Excavations Between January 31st and February 2nd, 2019, we visited the site to log the conditions exposed in five test trenches, designated as TT-8-101 through TT-8-105. The test trenches were excavated using a Case 580

Project No. 18-072.00 backhoe operated by AECOM, under the direction of our field representative(s) to the depths shown in the table below.

Test Trench Excavated Depth (ft bgs)

TT-8-101 6

TT-8-102 4

TT-8-103 8

TT-8-104 9

TT-8-105 4

Upon completion, the test trenches were backfilled with the soil excavated from the pits. The backfill was placed in lifts and compacted using a sheepsfoot compaction wheel attached to the excavator. In areas where the backfill contained larger cobbles, the backfill was tamped into place with the bucket of the backhoe. After the backfill was completed the backhoe operator spread seed and straw for erosion control.

LABORATORY TESTING

Soil and rock core samples collected during our field investigation were delivered to AECOM in their Sacramento office. The samples were then sent to AECOM’s laboratory in Anaheim, CA where they were tested to determine atterberg limits, compaction characteristics, and grain-size distribution sieve analysis.

Test results are shown on the exploration logs and provided in Appendix D.

SUBSURFACE CONDITIONS

In general, Borings B-8-101 and B-8-102 encountered two to three feet of surficial soil over decomposed Schist bedrock and Boring B-8-103 encountered decomposed bedrock at the ground surface. The surficial soils encountered consisted of moist, brown to strong brown, loose to dense silty sand. The bedrock was intensely to closely fractured with some crushed zones. The shallower rock (about 6 feet) in B-8-103 was decomposed to intensely weathered, and rock observed in the other two borings was generally intensely weathered. The bedrock was also friable to weak with low hardness and generally harder and stronger with depth.

The trenches generally exposed two different subsurface conditions. Test trenches TT-8-101, TT-8-102, and TT-8-105 encountered 1 to 3 feet of surficial soils underlain by Schist bedrock, very similar to materials observed in the borings. The surficial soils in all three trenches have an increased clay content and graded to silt and sandy clay in TT-8-101.

Trenches TT-8-103 and TT-8-104 were excavated in a fill slope that forms a turn-out along the existing access road. TT-8-103 encountered about 7 feet of fill materials underlain by native soils, and TT-8-104 encountered fill materials to the full depth explored, about 9 feet. The fill soils generally consisted of brown to reddish and yellowish brown, mixtures of sand and gravel with variable silt and clay content with variable amounts of cobbles. Some rock fragments and boulders (largest side dimension of approximately two feet) were also mixed in the fill. The native soil at the bottom of TT-8-103 is medium stiff, reddish brown clayey silt with some fine-grained sand, similar to TT-8-101.

Project No. 18-072.00

Groundwater was not encountered in any of the borings or test trenches. Representative photographs at each test trench are provided in Appendix C.

LIMITATIONS

This report has been prepared for the sole use of AECOM and USACE and is specific to the conditions observed at the Folsom Dam Raise Dike 8 site as described herein. The opinions contained in this report are based upon information obtained from our geotechnical investigation, experience, and engineering/geology judgment, and have been formulated in accordance with generally accepted geotechnical practices at the time this report was prepared; no other warranty is expressed or implied.

Actual conditions may vary.

The opinions presented in this report are valid as of the date of this report. Changes in the condition of a site can occur with the passage of time, whether due to natural processes or the works of man. In addition, changes in applicable standard of practice can occur, whether from legislation or the broadening of knowledge. Accordingly, this report may be invalidated, wholly or partially, by changes outside of SAGE’s control. In any case, this report should not be relied upon after a period of three years without prior review and approval by SAGE.

Sincerely yours, SAGE Engineers, Inc.

Darren Mack, PE, GE Jerry Pascoe, PE, GE Principal Engineer Principal Engineer

Figures: Figure 1 – Dike & Dam Locations Figure 2 – Dike 8 Exploration Site Plan

Appendices: Appendix A – Boring & Test Trench Logs Appendix B – Falling Head & Packer Test Logs Appendix C – Photographs Appendix D – Laboratory Data

FIGURES

GRAPHIC SCALE

0 1 mile0.50.25

DIKE / DAM

PL

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F rid ay , M ar ch

8, TI

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:2

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FIGURE

Date: By: Scale: Project No:

OF

1 2

DIKE & DAM LOCATIONS

FOLSOM DAM RAISE PROJECT

FOLSOM RESERVOIR, CALIFORNIA

3/8/2019 P. Barber No Scale 18-072.00

NOTE:

DIKE LOCATIONS AND IMAGERY FROM

PROJECT DRILLING PROGRAM PLAN, PREPARED

BY AECOM, DATED JANUARY 31, 2019 AND

UPDATED FEBRUARY 15, 2019.

X

X

X

X

X

X

X

X

X

X

X

X

G

A

T

E

X

X

X

X

FOOT PATH

FOOT PATH

ACCESS ROAD

DIRT TURNAROUND

S

A

N

S

A

N

S

A

N

S A

N

S

A

N

S

A

N

AC

AC

AC

DIRT

X

X

X

X

X

X

X

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E

E

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E

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B-8-101

B-8-102

B-8-103

TT-8-101

TT-8-102

TT-8-103

TT-8-104

TT-8-105

FOLSOM POINT ACCESS ROAD

SANITARY SEWER

MANHOLE

GATE

GATE

CHAIN LINK FENCE

SANITARY SEWER LINE

OVERHEAD POWER LINES

DIKE 8 CREST

DENSE BRUSH

PL

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FIGURE

By: Scale: Project No:

OF

2 2

DIKE 8 EXPLORATION SITE PLAN

FOLSOM DAM RAISE PROJECT

FOLSOM RESERVOIR, CALIFORNIA

3/8/2019 P. Barber 1" = 80' 18-072.00

DIKE 8

EXPLORATION

ID LATITUDE LONGITUDE

B-8-101 38.6933 -121.1344

B-8-102 38.6931 -121.1324

B-8-103 38.6932 -121.1316

TT-8-101 38.6932 -121.1342

TT-8-102 38.6931 -121.1335

TT-8-103 38.6931 -121.1319

TT-8-104 38.6930 -121.1320

TT-8-105 38.6931 -121.1324

LEGEND

BORING

TEST TRENCH

NOTE:

1. TOPOGRAPHIC BASE MAP PROVIDED BY AECOM,

DATED MARCH 2019.

APPENDIX A

Boring & Test Trench Logs

2251 Douglas Blvd., Ste. 200

Roseville, CA 95661

P (916) 677-4800 www.SAGEengineers.com

BULK

Disturbed grab sample

SPT

Standard Penetration Test (SPT) split-barrel sampler with a 2.0-inch outside diameter and a 1.5-inch inside diameter

CA

California split-barrel sampler with 2.5-inch outside diameter and 1.93-inch inside diameter

Modified California split-barrel sampler with 3.0-inch outside diameter and 2.5-inch inside diameter

MCA

Pitcher tube sampler using

3.0-inch outside diameter, thin-walled Shelby tube

PT

ST

Shelby tube (3.0-inch outside diameter, thin-walled tube) advanced with hydraulic pressure

O

Osterberg piston sampler using

3.0-inch outside diameter, thin-walled Shelby tube

C Core barrel

SAMPLER TYPE

Sampling attempted without recovery

Unstabilized (initial) groundwater level

Stabilized groundwater level

CC

CME Continuous Sample

Tube System sampler advanced with hollow stem auger

NOTE:

Shaded portion of sampler symbol represents portion of sample recovered

Examples:

MCA SPT CC

Portion recovered

UNIFIED SOIL CLASSIFICATION SYSTEM

Major Divisions Symbols Typical Names

C o a r s e

G r a i n e d

S o i l s m o r t h a n l f o f s o i l

N o s e v z e

Gravels

(More than half of coarse fraction >

No. 4 sieve size)

GW Well-graded gravels or gravel-sand mixtures, little or no fines

GP Poorly-graded gravels or gravel-sand mixtures, little or no fines

GM Silty gravels, gravel-sand-silt mixtures

GC Clayey gravels, gravel-sand-clay mixtures

Sands

(More than half of…