2023_A3Geo_Phase 2 Geotechnical Investigation.pdf

A3GEO-CE&G JV

821 Bancroft Way, Berkeley CA 94710

REACHES 5 AND 6 - PHASE 2 GEOTECHNICAL DATA REPORT

PAJARO RIVER FLOOD RISK MANAGEMENT PROJECT

SANTA CRUZ COUNTY

SEPTEMBER 6, 2023

Prepared for:

U.S. ARMY CORPS OF ENGINEERS

SAN FRANCISCO DISTRICT

Jimmy Chen, PE

450 Golden Gate Ave., 4th Floor

San Francisco, CA 94102-3404

Dona Kelly, PE 60947, GE 2901 Principal Engineer Technical Review Consultant

Timothy P. Sneddon, PE 66029, GE 2809 Principal Engineer

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Pajaro River Flood Risk Management Project SEPTEMBER 6, 2023

TABLE OF CONTENTS

1. Introduction and Project Background

1.1 Project Description

1.2 Previous investigations

1.3 Geologic Setting

1.4 Phase 2 Geotechnical Exploration Objective

1.5 Project Team

2. Geotechnical Investigation

2.1 Site Reconnaissance and Utility Clearance

2.2 Field Exploration

2.3 Soil Sampling

2.4 Surveyed Borehole Locations

2.5 Laboratory Testing

3. Site Conditions

3.1 Surface Conditions

3.2 Subsurface Conditions

4. Report Limitations

5. References

5.1 Technical References and Reports

5.2 ASTM International Standards

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TABLES

Table 2-1 Summary of Exploratory Boring Locations

Table 2-2 Summary of Exploratory Borings

Table 2-3 SPT Hammer Efficiency

Table 2-4 Summary of Laboratory Tests Performed

FIGURES

Figure 1. Vicinity and Location Maps

Figure 2. Exploration Map – Reach 5

Figure 3. Exploration Map – Reach 6

Figure 4. Regional Geologic Map

APPENDICES

Appendix A. Exploratory Boring Logs

Appendix B. Laboratory Test Results

Appendix C. Daily Field Reports

Appendix D. Survey Data

Appendix E. Hammer Energy Calibration Reports

Appendix F. (N1)60 Blow Count Corrections

Appendix G. Field Boring Logs

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Pajaro River Flood Risk Management Project September 6, 2023

1. INTRODUCTION AND PROJECT BACKGROUND

The A3GEO-CE&G JV (JV) has been retained by the U.S. Army Corps of Engineers, San Francisco District (herein referred to as USACE) under Contract No. W912P722D0001 and Task Order No. W2912P722F0028, dated July 18, 2022, to perform the Phase 2 Geotechnical Field Investigation in support of the Pajaro River Flood Risk Management Project located in Santa Cruz County, California. The JV prepared this Geotechnical Data Report (GDR) to summarize the findings of the field investigation.

USACE plans to construct flood risk reduction features along Salsipuedes Creek and Corralitos Creek, which are tributaries of the Pajaro River in Santa Cruz County. The Phase 1 geotechnical field investigation was performed by the JV in the spring of 2022 and consisted of 22 Cone Penetration Test (CPT) soundings. The Phase 2 geotechnical exploration is intended to supplement the Phase 1 exploration program, and consisted of fourteen (14) exploratory borings, index laboratory testing, and a survey of as-drilled locations. This GDR presents the results of the Phase 2 geotechnical exploration. Digital files of the report contents will be transmitted to USACE concurrently with the final submittal of this report.

1.1 PROJECT DESCRIPTION

The Pajaro River Flood Risk Management project is divided into eight reaches. This Phase 2 Geotechnical Field Investigation focuses on Reach 5 and Reach 6, which span approximately 4.5 miles. Reach 5 and Reach 6 are within the levee systems designated with National Levee Database (NLD) System ID numbers of 5305000025 and 5305000024. The regional project location and the Reach 5 and Reach 6 locations are shown on Figure 1. The Reach 5 segment is approximately 2.6 miles in length and spans from the confluence of Salsipuedes Creek and the Pajaro River (start of Reach) to the confluence of Corralitos Creek and Salsipuedes Creek at the intersection of Highway 152 and East Lake Avenue (end of Reach). The Reach 6 segment is approximately 1.9 miles in length and spans from the confluence of Corralitos Creek and Salsipuedes Creek at the intersection of Highway 152 and East Lake Avenue (start of Reach) to Green Valley Road (end of Reach).

The proposed improvements for Reach 5 and Reach 6 are anticipated to include floodwalls, a combination levee with a floodwall on top, setback levees, and erosion protection riprap.

1.2 PREVIOUS INVESTIGATIONS

Boring logs and laboratory data from previous subsurface explorations (performed by others) were provided to the JV by the USACE in a report titled: " Existing Subsurface

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Information”, dated March 2022. The Existing Subsurface Information report for Reaches 5 and 6 provided data from the following investigations:

USACE, 1990, Pajaro River and Salsipuedes Creek, Boring Logs

CH2MHill, 1996, Report of Field Activities, Corralitos-Salsipuedes Creek, Subsurface Soils Exploration

URS, 2000, Report of Field Activities, Subsurface Geotechnical Investigation, Pajaro River and Salsipuedes Creek

Haro, Kasunich & Associates, 2002, Geotechnical Engineering Study, Design Phase for Salsipuedes Creek Levee Stabilization Project

Caltrans, 1964, Highway 152 Bridge at Salsipuedes Creek, Log of Test Borings

(LOTB)

Caltrans, 1967, Highway 152 Bridge at Corralitos Creek As-Built, LOTB

Caltrans, 1988, Highway 129 Salsipuedes Creek Bridge Widening, LOTB

Caltrans, 1979, Green Valley Road Corralitos Creek Bridge Widening, LOTB

The Existing Subsurface Information report also included 11 CPTs that were performed by the United States Geological Survey between April 4, 1990 and June 17, 1991, in the vicinity of Reaches 5 and 6; however, these CPTs were not grouped under a specific project.

A Phase 1 Geotechnical Field Investigation for this project was performed by the JV. The investigation included 22 CPT soundings and was conducted between April 25, 2022 and May 2, 2022.

The locations of these explorations are shown on the Exploration Map Figures 2 and 3.

1.3 GEOLOGIC SETTING

The Pajaro Valley is located within the Coast Ranges geomorphic province of California.

The Coast Ranges separate the Great Valley (including the San Joaquin Valley) from the Pacific Ocean and extends south from the Oregon border to the Transverse Ranges in Southern California. The Pajaro Valley is located to the west of the upland Santa Cruz Mountains and San Andreas fault.

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The Pajaro River extends from the southern portion of Santa Clara County through a water gap in the Santa Cruz Mountains, into Pajaro Valley located in the southern end of Santa Cruz County and the northern parts of San Benito County and Monterey County. The Santa Cruz Mountains and San Andreas Fault effectively bisect the river into an upper and lower watershed; Pajaro Valley is located in the lower watershed. The Pajaro Valley slopes gently westward and is bounded to the east by the Santa Cruz Mountains and to the west by the Pacific Ocean, including Monterey Bay. The valley is a structural low filled with late Tertiary to Quaternary age continental and marine sediments and characterized as a coastal lowland containing marine, alluvial, fluvial, and eolian deposits (Dupre, 1975).

In the vicinity of Reaches 5 and 6, near the confluence of the Corralitos-Salsipuedes creek with the Pajaro River, the surficial geologic units adjacent to the active river channel, included as Figure 4, consist of young alluvium of Holocene and younger age, and further from the active river channel are Pleistocene age deposits designated Terrace deposits of Watsonville (Brabb, 1997).

1.4 PHASE 2 GEOTECHNICAL EXPLORATION OBJECTIVE

The objective of the geotechnical exploration was to characterize the geotechnical properties of subsurface materials within Reaches 5 and 6. The collected data will supplement the existing data and be incorporated into the geotechnical evaluation for the project.

1.5 PROJECT TEAM

A licensed Professional Engineer (PE) from the JV oversaw the field activities and logged the boreholes. Drilling services were provided by Pitcher Services, LLC, laboratory testing was performed by Cooper Testing Labs, Inc., and survey data were acquired by Mid Coast Engineers. The principal team members responsible for the implementation of the Project include the following individuals:

Dona Kelly, PE, GE (Principal Engineer, JV) – Task Order Manager, Quality Control Reviewer

Tim Sneddon, PE, GE (Principal Engineer, JV) – Lead Engineer

Chris Nardi, PE, GE (Principal Engineer, JV) – Quality Control Reviewer

James Yang, PE, GE (Associate Engineer, JV) – Project Manager (Former Employee)

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Jeffrey Hoeft, PG, CEG (Senior Engineering Geologist, JV) – Geologist (Former Employee)

Dario Leekam, PE (Project Engineer, JV) – Field Engineer

William Vimahi, (Pitcher Services, LLC) – Lead Driller

Nejat Yolason (GeoTech Utility Locating LLC.) – Utility Location Project Manager

Jeff Nielsen (Mid Coast Engineers) – Lead Surveyor

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2. GEOTECHNICAL INVESTIGATION

A Phase 2 Geotechnical Exploration – Investigation Plan Memorandum, dated October 19, 2022 (A3GEO-CE&G JV, 2022b), was submitted to and approved by USACE. The geotechnical investigation generally followed the means and methods described in the memorandum and was performed in general accordance with ASTM standards.

The geotechnical investigation consisted of the following components:

1. Site reconnaissance to confirm access and mark drilling locations for utility clearance.

2. Drill, sample, and log fourteen (14) exploratory borings.

3. Survey borehole locations.

4. Perform laboratory testing on select samples.

5. Present the results of the investigation and laboratory testing in a geotechnical data report.

Field activities were recorded on Daily Field Reports, and boreholes were logged in the field. Final Boring Logs are provided in Appendix A. Results from laboratory testing are presented in Appendix B. Daily Field Reports are included in Appendix C. Boring location survey results are presented in Appendix D. The drill rig hammer calibration results are included in Appendix E. A summary of calculations for converting field sampler blow counts to corrected (N1)60 blow counts is included in Appendix F. The field boring logs are also included as Appendix G.

2.1 SITE RECONNAISSANCE AND UTILITY CLEARANCE

A site reconnaissance was performed on October 11, 2022. Representatives from the JV, Pitcher Services (drilling subcontractor), USACE, Geo-Tech Utility Locating (private utility locater), and Santa Cruz Flood Control and Water Conservation District were also in attendance for the 1-day site reconnaissance. The reconnaissance included observations of site conditions, confirming access routes, assessing potential for buried utilities, and marking the proposed boring locations. During the reconnaissance, several of the originally proposed borehole locations were adjusted or alternate locations were marked due to potential access constraints or utility conflicts.

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The boring locations were marked using a combination of wooden stakes with white flagging and/or white spray paint. The boring ID number was included on the markings.

Underground Service Alert (USA) tickets were submitted for each boring location. Positive confirmation from USA was obtained for each of the planned borehole locations. Additional details and photos related to the site reconnaissance and utility clearance activities are provided in the Daily Field Reports included in Appendix C.

2.2 FIELD EXPLORATION

Field activities began on October 24, 2022, and concluded on November 4, 2022. A total of fourteen (14) exploratory borings were performed at the locations shown on Figures 2 and

3. Borings were advanced using a truck-mounted CME 55 (PD-56) drill rig or a track-mounted Fraste XL (PD-81) drill rig. Both drill rigs used automatic hammers to drive split tube samplers and hydraulics to advance thin-walled tubes. A combination of Standard Penetration Tests (SPTs), Modified California Sampler (MC), and Shelby tubes were used to collect representative soil samples at each boring location. A summary of the borings including the drilling method, date completed, drill rig, boring location coordinates, and total depth achieved is included in Table 2-1 and Table 2-2.

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Table 2-1 Summary of Exploratory Boring Locations

Boring ID Northing* Easting* Latitude* Longitude* Ground

Elevation (feet)**

B-1 1794616.989 6198944.097 36.9168888 -121.7407072 42.6

B-2 1797357.835 6201054.515 36.9244924 -121.7336128 49.7

B-3 1798202.828 6200622.238 36.9267972 -121.7351296 54.4

B-4 1798598.501 6200878.369 36.9278931 -121.7342713 57.5

B-5 1799424.601 6200907.498 36.9301628 -121.7342089 63.8

B-6 1800752.574 6199084.389 36.9337435 -121.7405055 63.7

B-7 1801180.770 6197449.043 36.9348598 -121.7461194 71.2

B-8 1801210.432 6197426.690 36.9349404 -121.7461972 70.9

B-9 1801853.135 6195979.139 36.9366523 -121.7511786 79.3

B-10 1801897.724 6195991.248 36.9367752 -121.7511393 79.1

B-11 1800963.965 6194354.003 36.9341507 -121.7566974 85.1

B-12 1801363.430 6196613.675 36.9353308 -121.7489855 74.7

B-13 1800889.253 6193942.976 36.9339304 -121.7581001 87.5

B-14 1800871.560 6193917.454 36.9338808 -121.7581866 87.3

*Horizontal datum: NAD 83 (2007 Epoch) CCS Zone 3.

**Vertical datum: NAVD88.

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Table 2-2 Summary of Exploratory Borings

Boring ID Drill Rig Drilling Method Date Drilled Depth of

Exploration (feet)

B-1 CME 55 (PD-56) Rotary Wash 10/28/2022 36.5

B-2 Fraste XL (PD-81) Rotary Wash 11/3/2022 31.5

B-3 Fraste XL (PD-81) Rotary Wash 11/3/2022 41.5

B-4 CME 55 (PD-56) Rotary Wash 10/27/2022 31.5

B-5 CME 55 (PD-56) Rotary Wash 11/1/2022 36.5

B-6 CME 55 (PD-56) Rotary Wash 10/25/2022 36.5

B-7 CME 55 (PD-56) Rotary Wash 10/24/2022 46.5

B-8 CME 55 (PD-56) Hollow Stem Auger 10/24/2022 16.5

B-9 CME 55 (PD-56) Rotary Wash 10/26/2022 46.5

B-10 CME 55 (PD-56) Hollow Stem Auger 10/26/2022 16.5

B-11 CME 55 (PD-56) Rotary Wash 10/31/2022 51.5

B-12 CME 55 (PD-56) Rotary Wash 10/31/2022 41..5

B-13 CME 55 (PD-56) Rotary Wash 10/27/2022 36.5

B-14 CME 55 (PD-56) Hollow Stem Auger 10/27/2022 16.5

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2.3 SOIL SAMPLING

The fourteen (14) borings were performed using rotary wash and/or hollow stem auger (HSA) drilling techniques. Representative samples were obtained using SPT and MC split spoon drive samples or undisturbed thin-walled Shelby tubes following the methods specified in the Investigation Plan (A3GEO-CE&G JV, 2022b). Upon retrieval, samples were described and logged in the field by a California licensed Professional Engineer in accordance with ASTM D2488 and the Unified Soil Classification System (USCS). Samples were then labeled and placed in storage containers. MC liners and Shelby tubes were end-logged and tested with a pocket penetrometer or torvane if materials were classified as cohesive fine grain soils. Recovered materials from SPT samples were placed in zip-loc bags and labeled. Observations and notes related to the day’s activities were documented on the daily field reports (Appendix C), while notes related to drilling operations were documented on the boring logs (Appendix A).

2.3.1 SPT and MC Drive Sampling

Soil samples were obtained using a SPT sampler (2-inch outside diameter) without liners or using a MC sampler (2.4-inch inside diameter) with brass or stainless-steel sample tubes (6-inch-long sleeves). SPTs were collected in accordance with ASTM 1556, while MC samples were collected in accordance with ASTM D3550. The SPT and MC samplers were driven using a 140-pound mechanically automated trip hammer with an approximate 30-inch fall. The number of hammer blows required to drive the sampler each 6-inch interval was recorded on the boring logs. If refusal was encountered, the type of refusal was noted on the boring log (i.e. hammer bounce, or 50 blows within a 6 inch interval).

2.3.2 Shelby Tube Sampling

Undisturbed samples were obtained using a Shelby-type thin-walled tube following ASTM D1587. Hydraulic down-pressure used to advance the sampler was recorded on the boring log. Retrieved samples were end-logged and tested using a pocket penetrometer or torvane. Retrieved samples were labeled, and endcaps were taped on the ends of tubes and stored upright in a purpose-built rack to hold Shelby Tubes. Following collection, tubes were transported in general accordance with ASTM D4220. At the end of each field day, the ends of each tube was wax sealed. If the ends of Shelby Tubes were bent or coarse grained materials were observed in the ends a tube, this was noted for consideration during laboratory test assignment.

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2.3.3 Borehole Grouting and Backfill

Following completion of each exploration, boreholes were backfilled using a neat cement grout placed with a tremie pipe. Grout was pumped through the tremie pipe with the pipe placed at the bottom of the boring, and incrementally raised until grout reached the ground surface. Once grout reached the ground surface, the tremie pipe was removed and the ground surface was restored to comparable original conditions. Upon completion, the drilling site was photographed; photos are included in the daily reports (Appendix C).

2.3.4 Groundwater

Where HSA drilling methods were used, groundwater was not encountered during the investigation. Where rotary wash drilling methods were used, the drilling methods obscured measurements of groundwater levels. Review of publicly available creek water height measurements on Corralitos Creek indicate that the water height in the creek at the time of drilling was about 2 to 3 feet above the channel bottom.

2.3.5 Hammer Energy Analysis

One (1) Hammer Energy Analysis was performed for each drill rig used during the subsurface investigation. The Hammer Energy Analysis was performed in accordance with ASTM D4633 during the field investigation. The analysis was performed on November 1, 2022 for the CME 55 drill rig and on November 3, 2022 for the Fraste XL drill rig. The results for each drill rig are indicated in Table 2-3, and the calibration reports are included in Appendix E.

Table 2-3 SPT Hammer Efficiency

Drill Rig Energy Efficiency

CME 55 (PD-56) 76%

Fraste XL (PD-81) 87%

2.3.6 (N1)60 Blow Count Corrections

Following data collection and laboratory testing, (N1)60 blow count corrections were calculated using the following equation:

(𝑁 ) = 𝐶 𝐶 𝐶 𝐶 𝐶 𝑁

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CN is an overburden correction factor, CE = ERm/60%, ERm is the measured value of the delivered energy as a percentage of the theoretical free-fall hammer energy, CR is a rod correction factor to account for energy ratios being smaller with shorter rod lengths, CB is a correction factor for nonstandard borehole diameters, CS is a correction factor for sampler type, and Nm is the measured SPT blow count.

The correction factors and equations for each term follow the recommendations in the American Association of State Highway and Transportation Officials (AASHTO) LRFD (Load and Resistance Factor Design) Bridge Design Specifications (AASTHO, 2017). Note that CR was kept as 1.0 since an average energy correction from the measured hammer efficiency was utilized, and since the hammer energy was measured over various rod lengths.

Further, at the request of USACE, CS utilized correlations by Robertson and Wride (1997) for split spoon samplers, and Burmister (1948) for Modified California samplers. The results of the (N1)60 corrections are included in Appendix F.

2.4 SURVEYED BOREHOLE LOCATIONS

Borehole locations were surveyed on November 4, 2022, by Jeff S. Nielson, a California-licensed land surveyor with Mid-Coast Engineers. Dario Leekam, P.E. (JV Project Engineer) was onsite to oversee the survey operations. Coordinates of each exploration are included in Table 2-1, and Mid-Coast Engineer’s data report is included as Appendix D and provides additional information on survey methodology. Additional details and photos related to the surveying activities can be found in the Daily Field Reports included in Appendix C.

2.5 LABORATORY TESTING

Following completion of the field investigation, a senior geotechnical engineer and engineering geologist reviewed the boring logs and samples. Select soil samples were assigned for laboratory testing. The quantities and types of tests to be performed were reviewed and approved by a USACE representative. Laboratory testing was performed by Cooper Testing Laboratory. A summary of the tests and quantities selected are provided in Table 2-4. The laboratory test results and data sheets are presented in Appendix B. The results of the water content, dry density, particle size distribution, and Atterberg Limits tests are also presented on the boring logs (Appendix A) at the corresponding sample depths.

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Table 2-4 Summary of Laboratory Tests Performed

Type of Laboratory Test ASTM Quantity

Moisture Content D2216-19 64

Moisture & Dry Density D7263-21 18

Atterberg Limits D4318-17e1 55

Sieve with Fines Content (- #200) D422 55

Sieve with Hydrometer D422 11

Hydraulic Conductivity D5084-16 5

Triaxial Undrained Unconsolidated (UU) D2850-15 3

Triaxial Consolidated Undrained (CU) with pore pressure

D4767-11(2020) 2

Consolidation D2435/D2435M-11(2020) 9

Electric Resistivity Caltrans 643 1

Chloride Caltrans 422 1

Sulfate Caltrans 417 1 pH Caltrans 643 1

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3. SITE CONDITIONS

3.1 SURFACE CONDITIONS

Reaches 5 and 6 of the Pajaro River Flood Risk Management Project are located alongside the Salsipuedes and Corralitos creeks, respectively. From north to south, the reaches extend approximately 4.1 miles from Green Valley Rd to Highway 129. Explorations were performed between 30 and 200 feet from the centerline of the creeks, as shown on Figures 1 through 3. Surface conditions generally consisted of agricultural land, with the exception of Borings B-1 and B-5. Boring B-1 was performed on the crest of a paved levee path and Boring B-5 was performed on a paved, residential street. Regional geologic maps (Figure 4) indicate the geologic unit at the ground surface is Holocene age fluvial deposits, with unit Qyf representing Younger Flood Plain Deposits, and unit Qof representing Older Flood Plain Deposits (e.g., Brabb, 1997).

3.2 SUBSURFACE CONDITIONS

3.2.1 Reach 5

Subsurface conditions along Reach 5 generally consisted of fill over alluvium.

Fill: From Borings B-2 to B-6, the fill was between 1 and 4 feet thick, and consisted of silty sands, lean clays, and silts. At Boring B-1, the fill was encountered to a depth of 9 feet below the crest of the existing levee and consisted of a 1½-feet thick layer of silty sand over 7½ feet of silt.

The silty sands in the fill were generally dry to moist, and loose in relative density. The silt in Boring B-1 was moist, medium stiff to stiff in consistency, and exhibited no plasticity.

The silt contained approximately 0 to 7 percent gravel, 37 to 47 percent sand, and 53 to 56 percent fines. The silt in Boring B-6 was dry, very stiff and had low plasticity. The lean clay fills encountered in Borings B-4 and B-5 were generally dry, and stiff to very stiff in consistency. The clays had low to medium plasticity, and their sand content ranged from 2 percent to higher than 30 percent.

Alluvium: The alluvium extended from the bottom of the fill to the total depths explored and generally consisted of sand, silt, and clay materials.

The alluvial sands within Reach 5 generally consisted of poorly-graded sands with silts and interbedded silty and clayey sands. The sand materials were dry to moist and very loose to medium dense in relative density. The sands contained between 0 and 40 percent gravel, Reaches 5 and 6 - Phase 2 Geotechnical Data Report Page 14 and between 5 and 49 percent fines. The fines in the silty sands generally had no plasticity.

In the clayey sands, the liquid limit and plastic index of the fines ranged 24 to 33, and from 8 to 14, respectively.

The alluvial silts were generally moist and very stiff in consistency, with the exception of Boring B-1, where their consistency was very soft. The liquid limit and plastic index in the silts ranged from 30 to 32, and from 1 to 5, respectively. No gravel was encountered in the silts within Reach 5, and their fines content varied from 70 to 87 percent. No alluvial silts were encountered in Borings B-2, B-3, or B-6.

The alluvial clays in Reach 5 were generally moist, and very soft to hard in consistency. The liquid limit and plastic index in the clays ranged from 32 to 84, and 10 to 56, respectively.

The gravel and sand contents in the clay varied from 0 to 17 percent, and from 2 to 13 percent, respectively.

At the bottom of Borings B-1 through B-4, the fine-grained sediments had a distinctive blue-gray coloring. The layer is soft to stiff and ranges from low to high plasticity, with some sandy interbeds. The layer is encountered at different elevations among the boreholes, and is interpreted to likely be Qb Basin Fill or Qcf Abandoned Channel Fill deposits.

3.2.2 Reach 6

Subsurface conditions along Reach 6 generally consisted of a relatively thin layer of fill over alluvium.

Fill: The fill was between 1 and 3.5 feet thick, and consisted of gravel, silty and clayey sands, silts, and lean clays with sand.

Boring B-8 encountered 1½ feet of poorly-graded gravel with silt and sand. The gravel was medium dense and dry. The thicknesses of the clayey and silty sands were 1 foot or less.

The sand was dry, and very loose to medium dense in relative density. The fines in the silty sand had no plasticity, and the liquid limit and plastic index of the fines in the clayey sand were 28 and 10, respectively.

The fill silt materials encountered were dry to moist, stiff, and exhibited low plasticity. The silt had no gravel and a sand content of approximately 41 percent.

About 1 foot of lean clay with sand were encountered at Borings B-9 and B-10. The clay was very stiff and dry, and exhibited low plasticity.

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Alluvium: The alluvium extended from the bottom of the fill to the total depths explored and generally consisted of sands with interbedded layers of clays, silts, and gravels, with the exception of B-9 and B-10, where predominantly fine-grained materials with interbedded sands was encountered.

The alluvial sands at Reach 6 were generally dry to moist, and very loose to medium dense in relative density. The sands contained between 0 and 6 percent gravel, and between 9 and 45 percent fines. The fines in the silty sands and poorly-graded sand with silt had no plasticity. The liquid limit and plastic index in the clayey sands varied from 23 to 33, and from 9 to 17, respectively. A 5-foot layer of poorly-graded gravel with silt and sand was encountered at a depth of 10 feet in B-7. The gravel was moist, very loose to loose, with fine, subrounded gravel up to 1-inch in size.

Alluvial silts encountered were dry to moist, and medium stiff to stiff in consistency. The liquid limit and plastic index in the silts ranged from 0 to 28, and from 0 to 6, respectively.

No gravel was encountered in the silts within Reach 6, and their fines content varied from 75 to 53 percent.

The alluvial clays in Reach 6 were generally dry to moist, and soft to medium stiff in consistency. The liquid limit and plastic index in the clays ranged from 30 to 63, and 10 to 41, respectively. The gravel and sand contents in the clay varied from 0 to 2 percent, and from 5 to 45 percent, respectively.

At the bottom of Boring B-12, the fine-grained sediments had a distinctive blue-gray coloring. The layer was soft to stiff and ranges from low to high plasticity, with some sandy interbeds. The layer is interpreted to likely be Qb Basin Fill or Qcf Abandoned Channel Fill deposits.

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4. REPORT LIMITATIONS

This report has been prepared for the exclusive use of USACE. The data and interpretations presented in this report were developed in accordance with generally-accepted geotechnical principles and practices. The findings of this report are valid as of the present date. However, the passing of time will likely change the conditions due to natural processes or the works of man. In addition, due to legislation or the broadening of knowledge, changes in applicable or appropriate standards will occur. Accordingly, this report should not be relied upon after a period of three years without being reviewed by this office.

The scope of this investigation was limited to aspects of the Project that are geotechnical and/or geologic in nature. The scope of our investigation did not include an environmental assessment or investigation for the presence of hazardous, toxic, or corrosive materials on, below, or around the site.

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5. REFERENCES

5.1 TECHNICAL REFERENCES AND REPORTS

A3GEO-CE&G JV, 2022a, Geotechnical Data Report, Phase 1 Geotechnical Investigation, Pajaro River Flood Risk Management Project, Santa Cruz, County, June 14.

A3GEO-CE&G JV, 2022b, Phase 2 Geotechnical Exploration – Investigation Plan, Pajaro River Flood Risk Management Project, Santa Cruz, County, October 19.

American Association of State Highway and Transportation Officials (AASHTO), 2017, AASHTO LRFD, Bridge Design Specifications, 8th Edition, 2017.

Brabb, E.E., 1997, Geologic Map of Santa Cruz County, California: a digital database, U.S.G.S., Open-File Report OF-97-489, 1:62,500.

Burmister, D.M., 1962, Importance and Practical Use of Relative Density in Soil Mechanics, Proceedings, ASTM, Vol. 48, pp. 1249-1268.

Robertson, P. & Wride, C.E., 1997, Cyclic liquefaction and its evaluation based on SPT and CPT. Proc. NCEER Workshop on Evaluation of Liquefaction Resistance of Soils. Report NCEER-97-0022, National Center for Earthquake Engineering Research.

Dupre, W.R., 1975, Quaternary history of the Watsonville Lowlands, north-central Monterey Bay region, California: Stanford, Calif., Stanford University, Ph.D. thesis, 145 p.

5.2 ASTM INTERNATIONAL STANDARDS

ASTM D1557 - Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort

ASTM D1586 - Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils

ASTM D2166M - Standard Test Method for Unconfined Compressive Strength of Cohesive Soil

ASTM D2216 - Laboratory Determination of Water (Moisture) Content of Soil and Rock

ASTM D2434 - Standard Test Methods for Measurement of Hydraulic Conductivity of Coarse-Grained Soils

Reaches 5 and 6 - Phase 2 Geotechnical Data Report Page 18

ASTM D2435 - Standard Test Methods for One-Dimensional Consolidation Properties of Soils Using Incremental Loading

ASTM D2487 - Classification of Soils for Engineering Purposes (Unified Soil Classification System)

ASTM D2488 - Description and Identification of Soils (Visual-Manual Procedures)

ASTM D2850 - Standard Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils

ASTM D422 - Particle-Size Analysis of Soils

ASTM D4220 - Standard Practices for Preserving and Transporting Soil Samples

ASTM D4318 - Liquid Limit, Plastic Limit, and Plasticity Index of Soils

ASTM D4633 - Standard Test Method for Energy Measurement of Dynamic Penetrometers

ASTM D4767 - Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils

ASTM D4829 - Standard Test Method for Expansion Index of Soils

ASTM D7263 - Standard Test Methods for Laboratory Determination of Density and Unit Weight of Soil Specimens

Reaches 5 and 6 - Phase 2 Geotechnical Data Report

FIGURES

REACH 6

LOCATION

MAP

REACH 5

A3GEO-CE&G JV Ÿ821 Bancroft Way, Berkeley CA 94710

PAJARO RIVER FLOOD RISK MANAGEMENT PROJECT

PHASE 2 GEOTECHNICAL INVESTIGATION

SANTA CRUZ COUNTY, CALIFORNIA

- SEPTEMBER 2023 FIGURE

VICINITY & LOCATION MAP

PLAN

NORTH

CP CP

VICINITY MAP LOCATION MAP

PLAN

NORTH

SCALE: 1" = 1 MILE SCALE: 1" = 1500'

REACH 5

FLOODWALL

AND LEVEE

LOCATIONS

REACH 6

LEVEE

LOCATIONS

2022 M icrosoft Corporation © 2022 M axar ©

CN

ES (2022) D

istribution Airbus D

S 0+

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PAJ008_PASPT-42

PAJ008_PASPT-43

PAJ008_PASPT-44

PAJ008_PASPT-45

PAJ010_PAJ-6

PAJ010_PAJ-7

PAJ010_PAJ-8

PAJ015_PASPT-59

PAJ015_PASPT-60

PAJ015_PASPT-61

PAJ015_PASPT-62

PAJ015_PASPT-63

PAJ015_PASPT-64

PAJ015_PASPT-65

PAJ015_PASPT-66

PAJ017_1

PAJ017_2PAJ017_3

PAJ017_4 PAJ017_5

PAJ017_6

PAJ017_7

PAJ017_8

PAJC02_B-1PAJC02_B-2

PAJC03_B-1

PAJC03_B-1A

PAJC03_B-2PAJC03_B-3

PAJC04_B-1

PAJC04_B-2

PAJC04_B-3

USGS_SZC024

USGS_SZC025

USGS_SZC026

USGS_SZC028

USGS_SZC029

USGS_SZC030

USGS_SZC031

USGS_SZC032

USGS_SZC033

A3GEO-CE&G JV_CPT-10

A3GEO-CE&G JV_CPT-11

A3GEO-CE&G JV_CPT-12

A3GEO-CE&G JV_CPT-13

A3GEO-CE&G JV_CPT-14

A3GEO-CE&G JV_CPT-15

A3GEO-CE&G JV_CPT-16

A3GEO-CE&G JV_CPT-17

A3GEO-CE&G JV_CPT-18

A3GEO-CE&G JV_CPT-19

A3GEO-CE&G JV_CPT-20

A3GEO-CE&G JV_CPT-21

A3GEO-CE&G JV_CPT-22A

A3GEO-CE&G JV_CPT-22B

A3GEO-CE&G JV_B-1

A3GEO-CE&G JV_B-2

A3GEO-CE&G JV_B-3

A3GEO-CE&G JV_B-4

A3GEO-CE&G JV_B-5

A3GEO-CE&G JV_B-6

45+00

+0

5+

0+

A3GEO-CE&G JV Ÿ821 Bancroft Way, Berkeley CA 94710

PAJARO RIVER FLOOD RISK MANAGEMENT PROJECT

PHASE 2 GEOTECHNICAL INVESTIGATION

SANTA CRUZ COUNTY, CALIFORNIA

- SEPTEMBER 2023 FIGURE

PLAN

NORTH

EXPLORATION MAP - REACH 5

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PAJ015_PASPT-65

PAJ015_PASPT-66

PAJ015_PASPT-67

PAJ015_PASPT-69

PAJ015_PASPT-71

PAJ015_PASPT-72

PAJC01_B-1 (64)

PAJC01_B-1 (65)

PAJC01_B-2

PAJC01_B-3

PAJC02_B-1

PAJC02_B-2

PAJC02_B-3

PAJC03_B-1

PAJC03_B-1A

PAJC03_B-2

PAJC03_B-3

PAJC05_B-1

PAJC05_B1-A

PAJC05_B-2

PAJC05_B-3

A3GEO-CE&G JV_CPT-01

A3GEO-CE&G JV_CPT-03

A3GEO-CE&G JV_CPT-04

A3GEO-CE&G JV_CPT-05

A3GEO-CE&G JV_CPT-06

A3GEO-CE&G JV_CPT-07

A3GEO-CE&G JV_CPT-08

A3GEO-CE&G JV_CPT-09

A3GEO-CE&G JV_CPT-10

A3GEO-CE&G JV_CPT-11

A3GEO-CE&G JV_CPT-12

A3GEO-CE&G JV_CPT-13

A3GEO-CE&G JV_B-6

A3GEO-CE&G JV_B-7

A3GEO-CE&G JV_B-8

A3GEO-CE&G JV_B-9

A3GEO-CE&G JV_B-10

A3GEO-CE&G JV_B-11

A3GEO-CE&G JV_B-12

A3GEO-CE&G JV_B-13

A3GEO-CE&G JV_B-14

0+00 5+00

A3GEO-CE&G JV Ÿ821 Bancroft Way, Berkeley CA 94710

PAJARO RIVER FLOOD RISK MANAGEMENT PROJECT

PHASE 2 GEOTECHNICAL INVESTIGATION

SANTA CRUZ COUNTY, CALIFORNIA

- SEPTEMBER 2023 FIGURE

EXPLORATION MAP - REACH 6

PLAN

NORTH

CP CP

Qof Qof

Qyf

Qof

Qof

Qof

QofQof

Qof

Qwf Qwf

Qwf

Qb

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Qb

Qt

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Qt

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Qal

ZAYANTE FAULT

A3GEO-CE&G JV Ÿ821 Bancroft Way, Berkeley CA 94710

PAJARO RIVER FLOOD RISK MANAGEMENT PROJECT

PHASE 2 GEOTECHNICAL INVESTIGATION

SANTA CRUZ COUNTY, CALIFORNIA

- SEPTEMBER 2023 FIGURE

GEOLOGIC MAP

PLAN

NORTH

Younger flood-plain deposits (Holocene)—Unconsolidated, fine-grained, heterogeneous deposits of sand and silt, commonly containing relatively thin, discontinuous layers of clay. Gravel content increases toward the Santa Cruz Mountains and is locally abundant within channel and lower point-bar deposits in natural levees and channels of meandering streams. Thickness generally less than 20 ft

Older flood-plain deposits (Holocene)—Unconsolidated, fine-grained sand, silt, and clay. More than 200 ft thick beneath parts of the Pajaro and San Lorenzo River flood plain. Lower parts of these thick fluvial aggradational deposits include large amounts of gravel, and serve a major ground-water aquifer beneath Pajaro Valley

Terrace deposits of Watsonville - Fluvial facies (Pleistocene)—Semi-consolidated, moderately to poorly sorted silt, sand, silty clay, and gravel. May be more than 200 ft thick. Gravel, approximately 50 ft thick, is generally present 50 ft below surface of deposit and is both a local aquifer and significant source of gravel. Upper 5 to 15 ft of unit is moderately indurated owing to clay and iron oxide cementation in weathered zone

Basin deposits (Holocene)—Unconsolidated, plastic, silty clay and clay rich in organic material. Locally contain interbedded thin layers of silt and silty sand. Deposited in a variety of environments including estuaries, lagoons, marsh-filled sloughs, flood basins, and lakes. Thickness highly variable; may be as much as 90 ft thick underlying some sloughs

Terrace deposits, undifferentiated (Pleistocene)—Weakly consolidated to semiconsolidated heterogeneous deposits of moderately to poorly sorted silt, silty clay, sand, and gravel. Mostly deposited in a fluvial environment. Thickness highly variable;

locally as much as 60 ft thick. Some of the deposits are relatively well indurated in upper 10 ft of weathered zone

Alluvial deposits, undifferentiated (Holocene)—Unconsolidated, heterogeneous, moderately sorted silt and sand containing discontinuous lenses of clay and silty clay. Locally includes large amounts of gravel. May include deposits equivalent to both younger (Qyf) and older (Qof) flood-plain deposits in areas where these were not differentiated. Thickness highly variable; may be more than 100 ft thick near coast

Alluvial fan deposits (Holocene)—Unconsolidated, moderately to poorly sorted sand, silt, and gravel, with layers of silty clay.

Generally coarsest nearest mountain front. Thickness uncertain, but may locally be greater than 50 ft

Qt

Qal

Qyfo

Qb

Qwf

Qof

Qyf

Reaches 5 and 6 - Phase 2 Geotechnical Data Report

Appendix A. Exploratory Boring Logs

MAJOR DIVISIONS

COARSE

GRAINED

SOILS:

more than 50% retained on No. 200 sieve

FINE

GRAINED

SOILS:

50% or more passing No. 200 sieve

SANDS:

more than 50% passing on No. 4 sieve

SILTS AND CLAY:

Liquid Limit 50% or less

COARSE

GRAINED

SOILS:

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

SILTS AND CLAY:

Liquid Limit 50% or greater

HIGHLY ORGANIC SOILS

CLEAN

GRAVELS

GRAVELS

WITH

SAND

CLEAN

SANDS

SANDS

WITH

FINES

UNIFIED SOIL CLASSIFICATION CHART

BOUNDARY CLASSIFICATION AND GRAIN SIZES

SILT OR CLAY

SAND GRAVEL

COBBLES BOULDERS

FINE COARSEMEDIUM COARSEFINE

U.S. Standard Sieve Sizes

No. 200 No. 40 No. 10 No. 4 3/4" 3" 12"

0.075 mm 0.425 mm 2 mm 3/16"

Modified California (MC) Sampler (3" O.D.)

Standard Penetration Test:

SPT (2" O.D.)

Water Levels At time of drilling At end of drilling After drilling

HQ ROCK CORE ( )

Pitcher Tube ( T)

SYMBOLS

ABBREVIATIONS NOTES

Item Meaning LL Liquid Limit (%) (ASTM D 4318) PI Plasticity Index (%) (ASTM D 4318) -200 Passing No. 200 (%) (ASTM D 1140) TX CU Laboratory consolidated undrained triaxial test of undrained shear strength (psf) (ASTM D 4767) U Laboratory

(ASTM D 2 )

psf/tsf pounds per square foot / tons per square foot psi pounds per square inch OD Outside Diameter

1. Stratification lines represent the approximate boundaries between material types and the transitions may be gradual.

2. Recorded blow counts have not been adjusted for hammer energy.

KEY TO EXPLORATORY BORING LOGS

TYPICAL NAMES

Well graded gravels and gravel-sand mixtures, little or no fines Poorly graded gravels and gravel-sand mixtures, little or no fines Silty gravels and gravel-sand-silt mixtures Clayey gravels and gravel-sand-clay mixtures Well graded sands and gravelly sand, little or no fines Poorly graded sands and gravelly sand, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Inorganic silts, very fine sands, rock flour, silty or clayey fine sands Inorganic clays or low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sands or silts, elastic clays Inorganic clays of high plasticity, fat clays Organic clays of medium to high plasticity Peat, muck, and other highly organic soilsPT

OH

CH

MH

OL

CL

ML

SM

SP

SW

SC

GC

GM

GP

GW

Tube ( T)

HSA from ground surface

Gravel=7% Sand=37% Silt=45% Clay=11%

Corrosivity Test

Gravel=0% Sand=47% -#200=53%

LL=NP, PI=NP

switch to mud rotary Gravel=0% Sand=63% -#200=37%

LL=46, PI=21

Consolidation TXUU Su=895 psf

Gravel=0% Sand=13% -#200=87%

LL=32, PI=5

LL=58, PI=32

Consolidation

TXCU

Asphalt (4'') over Aggregate Base (8")

SILTY SAND (SM) - brown, dry, few fine to coarse gravel, up to 1-inch diameter (FILL) [Levee Embankment]

SANDY SILT (ML) - stiff, brown, moist, non-plastic, fine sand

- at 5 feet, medium stiff

SILTY SAND (SM) - loose, brown, moist [Qyf Younger Flood Plain Deposits]

LEAN CLAY (CL) - very soft, brown, moist, low to medium plasticity

POORLY-GRADED SAND WITH SILT (SP-SM) - loose, yellowish brown, moist, fine to medium sand

SILT (ML) - very soft, bluish gray, moist, low plasticity, few fine sand [Qb Basin Deposits or Qcf Abandoned Channel Fill Deposits]

FAT CLAY (CH) - soft to medium stiff, bluish gray, moist, medium to high plasticity

50 psi

0 psi 0.7

GB

S-1

SPT

S-2

SPT

S-3

SPT

S-4

SPT

S-5

SPT

S-6

ST

S-7

SPT

S-8

ST

S-9

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A P

H

IC

LO

G OTHER LAB

TESTS / NOTESMATERIAL DESCRIPTION

R E

C O

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(Continued Next Page)

D E

P T

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(t sf

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T

Y P

E

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N

U M

B E

R

BORING NUMBER B-1

HOLE SIZE HSA 8'' / RW 4''

GROUND WATER LEVELS:

DATE STARTED 10/28/22 COMPLETED 10/28/22

AT TIME OF DRILLING --- N/A due to drilling method

AT END OF DRILLING --- N/A due to drilling method

AFTER DRILLING --- N/A due to drilling method

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL RIG AND METHOD CME 55 Truck Rig / HSA and Mud Rotary

Location (Lat/Long) NAD83 CCS zone 3 (36.9168888, -121.7407072)

CHECKED BY JSH

GROUND ELEVATION 42.63 ft NAVD88

PROJECT NAME Pajaro FRM Reaches 5 and 6 Phase 2 Investigation

PROJECT LOCATION Santa Cruz County

CLIENT San Francisco District, U.S. Army Corps of Engineers

PROJECT NUMBER 1201-1A

P A

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P J

Gravel=0% Sand=2% Silt=64% Clay=34%

Gravel=0% Sand=29% -#200=71%

LL=30, PI=1

Torvane = 0.35 tsf

FAT CLAY (CH) - soft to medium stiff, bluish gray, moist, medium to high plasticity(continued)

SILT (ML) - stiff, bluish gray, moist, medium plasticity

SILTY SAND (SM) - loose, bluish gray, moist, fine sand

SILT (ML) - very soft, bluish gray, moist, low plasticity

LEAN CLAY (CL) - medium stiff, bluish gray, moist, medium plasticity, some organic material

Bottom of borehole at 36.5 feet.

Backfilled using neat cement grout to ground surface using tremie method.

GWT obscured by drilling method.

1.2

0.8

MC

S-10

SPT

S-11

MC

S-12

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H

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G OTHER LAB

TESTS / NOTESMATERIAL DESCRIPTION

R E

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P O

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(t sf

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N

U M

B E

R

BORING NUMBER B-1

HOLE SIZE HSA 8'' / RW 4''

GROUND WATER LEVELS:

DATE STARTED 10/28/22 COMPLETED 10/28/22

AT TIME OF DRILLING --- N/A due to drilling method

AT END OF DRILLING --- N/A due to drilling method

AFTER DRILLING --- N/A due to drilling method

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL RIG AND METHOD CME 55 Truck Rig / HSA and Mud Rotary

Location (Lat/Long) NAD83 CCS zone 3 (36.9168888, -121.7407072)

CHECKED BY JSH

GROUND ELEVATION 42.63 ft NAVD88

PROJECT NAME Pajaro FRM Reaches 5 and 6 Phase 2 Investigation

PROJECT LOCATION Santa Cruz County

CLIENT San Francisco District, U.S. Army Corps of Engineers

PROJECT NUMBER 1201-1A

P A

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Rotary wash from ground surface

Gravel=0% Sand=95% -#200=5%

Gravel=7% Sand=85% -#200=8%

LL=NP, PI=NP

Gravel=0% Sand=92% -#200=8%

LL=NP, PI=NP

Gravel=16% Sand=13% Silt=34% Clay=37%

LL=66, PI=46

Consolidation

SILTY SAND (SM) - loose, brown, moist, fine sand, with roots

(FILL)

POORLY GRADED SAND WITH SILT (SP-SM) - loose, yellowish brown, moist, fine sand [Qof Older Flood Plain Deposits]

- at 5 feet, medium dense

- at 8 feet, medium dense, few fine gravel

- at 10 feet, medium dense, trace fine gravel

- at 13 feet, medium dense, few fine gravel

- at 15 feet, loose, with laminated oxidation

FAT CLAY (CH) - medium stiff, bluish gray, moist, medium plasticity, trace fine sand, trace fine gravel [Qb Basin Deposits or Qcf Abandoned Channel Fill Deposits]

- at 23 feet, stiff, 10 to 15% coarse to fine-grained sand

GB

S-1

SPT

S-2

SPT

S-3

SPT

S-4

SPT

S-5

SPT

S-6

SPT

S-7

SPT

S-8

MC

S-9

G R

A P

H

IC

LO

G OTHER LAB

TESTS / NOTESMATERIAL DESCRIPTION

R E

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(Continued Next Page)

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BORING NUMBER B-2

HOLE SIZE 4''

GROUND WATER LEVELS:

DATE STARTED 11/3/22 COMPLETED 11/3/22

AT TIME OF DRILLING --- N/A due to drilling method

AT END OF DRILLING --- N/A due to drilling method

AFTER DRILLING --- N/A due to drilling method

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL RIG AND METHOD Fraste XL Truck Rig / Rotary Wash

Location (Lat/Long) NAD83 CCS zone 3 (36.9244924, -121.7336128)

CHECKED BY JSH

GROUND ELEVATION 49.67 ft NAVD88

PROJECT NAME Pajaro FRM Reaches 5 and 6 Phase 2 Investigation

PROJECT LOCATION Santa Cruz County

CLIENT San Francisco District, U.S. Army Corps of Engineers

PROJECT NUMBER 1201-1A

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LL=46, PI=23

FAT CLAY (CH) - medium stiff, bluish gray, moist, medium plasticity, trace fine sand, trace fine gravel [Qb Basin Deposits or Qcf Abandoned Channel Fill Deposits](continued)

LEAN CLAY (CL) - very stiff to hard, light brown, moist, low to medium plasticity, sandy in some pockets

Bottom of borehole at 31.5 feet.

Backfilled using neat cement grout to ground surface using tremie method.

GWT obscured by drilling method.

>4

>4

MC

S-10

MC

S-11

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TESTS / NOTESMATERIAL DESCRIPTION

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BORING NUMBER B-2

HOLE SIZE 4''

GROUND WATER LEVELS:

DATE STARTED 11/3/22 COMPLETED 11/3/22

AT TIME OF DRILLING --- N/A due to drilling method

AT END OF DRILLING --- N/A due to drilling method

AFTER DRILLING --- N/A due to drilling method

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL RIG AND METHOD Fraste XL Truck Rig / Rotary Wash

Location (Lat/Long) NAD83 CCS zone 3 (36.9244924, -121.7336128)

CHECKED BY JSH

GROUND ELEVATION 49.67 ft NAVD88

PROJECT NAME Pajaro FRM Reaches 5 and 6 Phase 2 Investigation

PROJECT LOCATION Santa Cruz County

CLIENT San Francisco District, U.S. Army Corps of Engineers

PROJECT NUMBER 1201-1A

P A

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Gravel=0% Sand=80% -#200=20%

Gravel=3% Sand=91% -#200=6%

LL=NP, PI=NP

LL=32, PI=16

Gravel=40% Sand=45% -#200=15%

Gravel=10% Sand=76% -#200=14%

SILTY SAND (SM) - loose, brown, moist, fine sand, (FILL)

SILTY SAND (SM) - loose, light yellowish brown, fine sand

- at 5 feet, fine to medium sand, yellowish brown

POORLY GRADED SAND WITH SILT (SP-SM) - medium dense, yellowish brown, moist, trace fine gravel

LEAN CLAY WITH SAND (CL) - medium stiff, brown, moist, low to medium plasticity, fine to medium sand, trace fine gravel LEAN CLAY (CL) - medium stiff, brownish yellow, moist, medium plasticity, trace fine gravel [Qof Older Flood Plain Deposits]

CLAYEY SAND WITH GRAVEL (SC) - medium dense, light brown, moist, fine gravel

CLAYEY SAND (SC) - dense, yellowish brown, moist, few fine gravel

SILTY SAND (SM) - medium dense, olive brown, moist, fine sand

LEAN CLAY (CL) - very stiff, olive brown, moist, low to medium plasticity, with oxidized laminations

GB

S-1

SPT

S-2

SPT

S-3

SPT

S-4

SPT

S-5 S-6

MC

S-7

SPT

S-8 S-9

G R

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TESTS / NOTESMATERIAL DESCRIPTION

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(Continued Next Page)

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BORING NUMBER B-3

HOLE SIZE 4"

GROUND WATER LEVELS:

DATE STARTED 11/3/22 COMPLETED 11/3/22

AT TIME OF DRILLING --- N/A due to drilling method.

AT END OF DRILLING --- N/A due to drilling method.

AFTER DRILLING --- N/A due to drilling method.

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL RIG AND METHOD Fraste XL Truck Rig / Rotary Wash

Location (Lat/Long) NAD83 CCS zone 3 (36.9267972, -121.7351296)

CHECKED BY JSH

GROUND ELEVATION 54.37 ft NAVD88

PROJECT NAME Pajaro FRM Reaches 5 and 6 Phase 2 Investigation

PROJECT LOCATION Santa Cruz County

CLIENT San Francisco District, U.S. Army Corps of Engineers

PROJECT NUMBER 1201-1A

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Consolidation

Gravel=17% Sand=2% -#200=81%

LL=44, PI=19

GRAVELLY LEAN CLAY (CL) - stiff to very stiff, grayish blue, moist, medium plasticity, fine gravel [Qb Basin Deposits or Qcf Abandoned Channel Fill Deposits] LEAN CLAY (CL) - stiff to very stiff, grayish blue, moist, medium plasticity

- at 30 feet, some gravel

- at 36.5 feet, very stiff, few fine sand

Bottom of borehole at 41.5 feet.

Backfilled using neat cement grout and ground surface using tremie method.

GWT obscured by drilling method.

3.4

2.4

3.0

MC

S-10

MC

S-11

MC

S-12

SPT

S-13

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TESTS / NOTESMATERIAL DESCRIPTION

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BORING NUMBER B-3

HOLE SIZE 4"

GROUND WATER LEVELS:

DATE STARTED 11/3/22 COMPLETED 11/3/22

AT TIME OF DRILLING --- N/A due to drilling method.

AT END OF DRILLING --- N/A due to drilling method.

AFTER DRILLING --- N/A due to drilling method.

LOGGED BY DGL

DRILLING CONTRACTOR Pitcher Services LLC

DRILL…