GEOTECHNICAL ENGINEERING STUDY Athletic Field …

GEOTECHNICAL ENGINEERING STUDY

Concord High School Athletic Field Improvements

4200 Concord Boulevard Concord, California 94521

Prepared for:

Mt. Diablo Unified School District 1936 Carlotta Drive

Concord, California 94519

Prepared by:

GEOSPHERE CONSULTANTS, INC. 2001 Crow Canyon Road, Suite 210

San Ramon, California 94583 Geosphere Project No. 91-03875-A

April 20, 2017 Mt. Diablo Unified School District 1936 Carlotta Drive Concord, California 94519 Attention: John Willford, Project Manager Subject: Geotechnical Engineering Study Concord High School – Athletic Field Improvements

4200 Concord Boulevard Concord, California 94521 Geosphere Project No. 91-03875-A

Dear Mr. Willford: Geosphere Consultants, Inc. has completed a Geotechnical Engineering Study for the proposed improvements at Concord High School in Concord, California. Transmitted herewith are the results of our findings, conclusions, and recommendations for foundations, exterior concrete slabs, site preparation, grading, drainage, and utility trench backfilling. In general, the proposed improvements at the site are considered to be geotechnically feasible provided the recommendations of this report are implemented in the design and construction of the project. This report is not intended to function as a geohazard report which was not included in our scope of work. We note that a geohazard report is not required to be submitted according to Division of State Architect (DSA) Interpretation of Regulations IR A-4.13 provided that new bleacher or other field structures, if any, are seismically separated into areas of 4,000 square feet or less in covered area (Paragraph 3.2.3). Should you have questions or need additional information, please contact the undersigned at (925) 314-7180. The opportunity to be of service to Mt. Diablo Unified School District and to be involved in the design of this project is appreciated. Sincerely, GEOSPHERE CONSULTANTS, INC. Raghubar Shrestha, Ph.D., P.E. Corey T. Dare, P.E., G.E. Senior Engineer Principal Geotechnical Engineer Distribution: PDF to Addressee ([email protected]) RS/CTD:pmf

mailto:[email protected]

TABLE OF CONTENTS

1.0 INTRODUCTION ................................................................................................................................................. 1 1.1 Purpose and Scope ........................................................................................................................... 1 1.2 Site Description ................................................................................................................................ 1 1.3 Proposed Development .................................................................................................................... 2

2.0 PROCEDURES AND RESULTS ............................................................................................................................. 3 2.1 Literature Review ............................................................................................................................. 3 2.2 Drilling and Sampling ........................................................................................................................ 3 2.3 Laboratory Testing ............................................................................................................................ 4

3.0 GEOLOGIC AND SEISMIC OVERVIEW ................................................................................................................ 5 3.1 Geologic Setting................................................................................................................................ 5 3.2 Geologic Evolution of the Northern Coast Ranges ........................................................................... 5 3.3 Regional Faulting and Tectonics ....................................................................................................... 6

4.0 SUBSURFACE CONDITIONS ............................................................................................................................... 7 4.1 Subsurface Soil Conditions ............................................................................................................... 7 4.2 Groundwater .................................................................................................................................... 7 4.3 Field Infiltration Tests ....................................................................................................................... 7 4.4 Corrosion Testing ............................................................................................................................. 9

5.0 CONCLUSIONS AND RECOMMENDATIONS..................................................................................................... 12 5.1 Conclusions ..................................................................................................................................... 12 5.2 Seismic Design Parameters ............................................................................................................ 13 5.3 Site Grading .................................................................................................................................... 14 5.4 Utility Trench Construction ............................................................................................................ 17 5.5 Pier Foundations ............................................................................................................................ 19 5.6 Exterior Concrete Flatwork ............................................................................................................ 19 5.7 Athletic Track Asphalt Concrete Pavements .................................................................................. 20 5.8 Plan Review .................................................................................................................................... 20 5.9 Observation and Testing During Construction ............................................................................... 20

6.0 VALIDITY OF REPORT ...................................................................................................................................... 21 7.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS .......................................................................................... 22 8.0 REFERENCES .................................................................................................................................................... 23

TABLE OF CONTENTS (continued) FIGURES

Figure 1 - Site Vicinity Map Figure 2 - Development Site Plan Figure 3 - Site Plan and Site Geology Map Figure 4 - Site Vicinity Geology Map Figure 5 – Regional Fault Map Figure 6a - Geological Cross Section A-A’ Figure 6b - Geological Cross Section B-B’

APPENDIX A

Key to Boring Log Symbols Boring Logs

APPENDIX B LABORATORY TEST RESULTS Liquid and Plastic Limits Test Report Sieve Analysis Results R-Value Test Result Corrosivity Test Summary

GEOTECHNICAL ENGINEERING STUDY

Project: Concord High School – Athletic Field Improvements Concord, California

Client: Mt. Diablo Unified School District Concord, California

1.0 INTRODUCTION

1.1 Purpose and Scope

The purposes of this study were to evaluate the subsurface conditions at the site and prepare geotechnical

recommendations for the proposed improvements. This study provides recommendations for foundations,

exterior concrete slabs, site preparation, grading, drainage, utility trench backfilling, and guideline specifications

for grading. This study was performed in accordance with the scope of work outlined in our proposal dated January

9, 2017.

The scope of this study included the review of pertinent published and unpublished documents related to the site,

the drilling of 13 subsurface borings, drilling and testing of three percolation holes, laboratory testing of selected

samples retrieved from the borings, engineering analysis of the accumulated data, and preparation of this report.

The conclusions and recommendations presented in this report are based on the data acquired and analyzed

during this study, and on prudent engineering judgment and experience. This study did not include an assessment

of potentially toxic or hazardous materials that may be present on or beneath the site.

1.2 Site Description

Concord High School is located at 4200 Concord Boulevard in Concord, California, as shown on Figure 1, Site

Vicinity Map. The proposed site improvements will be located at the northeast part of the campus. These

improvements are planned to replace existing infrastructure, namely the baseball, softball, and soccer/football

fields. The site is relatively flat, with the general site vicinity topography sloping very gently to the west past the

track and field area. The campus is bounded on the northeast by lands of the former Concord Naval Weapons

Station now part of the Concord Re-Use Area; on the southeast by a city park and residential development, on the

south by Concord Boulevard, and on the northwest by residential development. The site is located at

approximately 37.9776 north latitude and 121.9867 west longitude based on the Google Earth application, and

2

ground surface elevations range from approximately 166 to 177 feet above mean sea level based on the provided

Improvement Plan.

1.3 Proposed Development

It is our understanding that the proposed site improvements are to consist of new baseball, softball, and

football/soccer fields to replace the existing facilities, with an athletic track surrounding the latter improvement.

Basic plans of the proposed improvement areas were provided to us at the time of this report preparation.

However, no detailed plans were available. Other improvements may include new bleacher structures, utility

upgrades, exterior concrete flatwork, and landscaping. The proposed improvement locations are shown on the

attached Figure 2, Development Site Plan.

3

2.0 PROCEDURES AND RESULTS

2.1 Literature Review

Pertinent geologic and geotechnical literature pertaining to the site area were reviewed. These included various

publications and maps issued by the United States Geological Survey (USGS), California Geological Survey (CGS),

water agencies, and other government agencies, as listed in the References section.

2.2 Drilling and Sampling

A subsurface exploration program was undertaken to evaluate the soil conditions at the site. A total of 13 borings

were drilled on March 3rd, 2017. Of this total, three borings were drilled on each baseball and softball field, and

six borings on the football/soccer field. The locations of the borings in relation to the proposed improvements are

shown on the attached Figures 2 and Figure 3, Site Plan and Site Geology Map. The borings were drilled using a

Mobile B-53 drill rig equipped with 8” hollow-stem augers.

A Geosphere representative visually classified the materials encountered in the borings according to the Unified

Soil Classification System as the borings were advanced. Relatively undisturbed soil samples were recovered at

selected intervals using a three-inch outside diameter Modified California split spoon sampler containing six-inch

long brass liners, and a two-inch outside diameter Standard Penetration Test (SPT) sampler. The samplers were

driven by means of a 140-pound safety hammer with an approximate 30-inch fall. Resistance to penetration was

recorded as the number of hammer blows required to drive the sampler the final foot of an 18-inch drive. All of

the field blow counts recorded using Modified California (MC) split spoon sampler were converted in the final logs

to equivalent SPT blow counts using appropriate modification factors suggested by Burmister (1948), i.e., a factor

of 0.65 with inner diameter of 2.5 inches. Therefore, all blow counts shown on the final boring logs are either

directly measured (SPT sampler) or equivalent SPT (MC sampler) blow counts.

The boring logs with descriptions of the various materials encountered in each boring, a key to the boring symbols,

and select laboratory test results are included in Appendix A. Ground surface elevations indicated on the soil

boring logs were estimated to the nearest foot using Google Earth.

4

2.3 Laboratory Testing

Laboratory tests were performed on selected samples to determine some of the physical and engineering

properties of the subsurface soils. The results of the laboratory testing are either presented on the boring logs,

and/or are included in Appendix B. The following soil tests were performed for this study:

Dry Density and Moisture Content (ASTM D2216 and ASTM 2937) – In-situ dry density and/or moisture tests were

conducted on 15 samples to measure the in-place dry density and moisture content of the subsurface materials.

These properties provide information for evaluating the physical characteristics of the subsurface soils. Test

results are shown on the boring logs.

Atterberg Limits (ASTM D4318 and CT204) - Atterberg Limits tests were performed on two samples of cohesive

soils encountered at the site. Liquid Limit, Plastic Limit, and Plasticity Index are useful in the classification and

characterization of the engineering properties of soil, and help to evaluate the expansive characteristics of the soil

and determine the USCS soil classification. Test results are presented in Appendix B, and on the boring logs.

Particle Size Analysis (Wet and Dry Sieve) and Hydrometer (ASTM D422, D1140, and CT202) - Sieve analysis testing

was conducted on selected samples to determine the soil particle size distribution. This information is useful for

the evaluation of liquefaction potential and characterizing the soil type according to USCS.

R-Value Test (ASTM D2844 and CT301) – One R-value test was performed on a sample collected from the site to

evaluate the subgrade soil strength for pavement designs. The R-value test was conducted on bulk sample of near-

surface materials collected from cuttings generated from Boring B-8 at depth from about 2.5 feet. The R-value of

30 was determined from the laboratory test. The test result is presented in Appendix B, and on the pertinent

boring log.

Soil Corrosivity, Redox (ASTM D1498), pH (ASTM D4972), Resistivity (ASTM G57), Chloride (ASTM D4327), and

Sulfate (ASTM D4327) - Soil corrosivity testing was performed to determine the effects of constituents in the soil

on buried steel and concrete. Water-soluble sulfate testing is required by the California Building Code (CBC) and

International Building Code (IBC). Soil corrosivity test results are summarized in Appendix B and are discussed in

Section 4.4.

5

3.0 GEOLOGIC AND SEISMIC OVERVIEW

3.1 Geologic Setting

The site is located in the central portion of the northern Coast Ranges geomorphic province of California. The

Coast Ranges extend from the Transverse Ranges in southern California to the Oregon border and are comprised

of a northwest-trending series of mountain ranges and intervening valleys that reflect the overall structural grain

of the province. The ranges consist of a variably thick veneer of Cenozoic volcanic and sedimentary deposits

overlying a Mesozoic basement of sedimentary, metamorphic, and basic igneous Franciscan Formation and

primarily marine sedimentary rocks of the Great Valley Sequence. East-dipping sedimentary rocks of the Coast

Ranges are flanked on the east by sedimentary rocks of the Great Valley geomorphic province (Page, 1966).

Specifically, the project site is located east of San Francisco Bay and northwest of Mt. Diablo, which is the northern

peak of the Diablo Range. The site is situated near the northeastern margin of the northwest-trending Concord

Valley, and shown on the map by Graymer et al. (2006) as being underlain by Pleistocene-aged alluvium (Qpa)

consisting of sands, clays, and gravels. Dibblee (2006) shows the general site vicinity as underlain by Holocene-

age alluvial sediments of similar composition, with the hills to the northeast underlain by Eocene-age Markley

Sandstone on the northeast side of the Clayton – Marsh Creek Fault discussed in Section 3.3. According to the

Natural Resources Conservation Service, Web Soil Survey, the site soil is classified as the Clear Lake Clay unit and

partially Rincon Clay Loam, which generally have a medium to high plasticity and a moderate to high expansion

potential. The mapped geologic units in the site vicinity per Graymer et al. (2006) are shown on Figure 3 as well

as Figure 4, Site Vicinity Geologic Map.

3.2 Geologic Evolution of the Northern Coast Ranges

The subject site is located within the tectonically active and geologically complex northern Coast Ranges, which

have been shaped by continuous deformation resulting from tectonic plate convergence (subduction) beginning

in the Jurassic period (about 145 million years ago). Eastward thrusting of the oceanic plate beneath the

continental plate resulted in the accretion of materials onto the continental plate. These accreted materials now

largely comprise the Coast Ranges. The dominant tectonic structures formed during this time include generally

east-dipping thrust and reverse faults.

Beginning in the Cenozoic time period (about 25 to 30 million years ago), the tectonics along the California coast

changed to a transpressional regime and right-lateral strike-slip displacements as well as thrusting were

6

superimposed on the earlier structures resulting in the formation of northwest-trending, near-vertical faults

comprising the San Andreas Fault System. The northern Coast Ranges were segmented into a series of tectonic

blocks separated by major faults including the San Andreas, Hayward, and Calaveras. The project site is situated

between the active Concord and potentially active Clayton - Marsh Creek faults, but no known active faults with

Holocene movement (last 11,000 years) lie within the limits of the site.

3.3 Regional Faulting and Tectonics

Regional transpression has caused uplift and folding of the bedrock units within the Coast Ranges. This structural

deformation occurred during periods of tectonic activity that began in the Pliocene and continues today. The site

is located in a seismically active region that has experienced periodic, large magnitude earthquakes during historic

times. This seismic activity appears to be largely controlled by displacement between the Pacific and North

American crustal plates, separated by the San Andreas Fault zone located approximately 34 miles (54.4 km) west

of the site. This plate displacement produced regional strain that is concentrated along major faults of the San

Andreas Fault System including the San Andreas, Hayward, and Calaveras faults in this area, Figure 5 - Regional

Fault Map. The site is not mapped within an Alquist-Priolo Earthquake Fault Zone. The AP zone for the active

Concord Fault is located approximately 2.3 miles to the west of the site. The potentially active Clayton-Marsh

Creek Fault is situated within the low hills of the northern end of the Diablo Range between approximately 1 and

2.5 miles northeast of the site, where numerous strands of the fault have been mapped or inferred. Active faulting

can be found outside of the AP special studies zone; however, this is very rare.

7

4.0 SUBSURFACE CONDITIONS

4.1 Subsurface Soil Conditions

During our subsurface exploration program, we investigated the subsurface soils and evaluated soil conditions up

to a maximum depth of 10 feet in the borings performed for this study. From our collected data, we conclude that

where explored, the area of the proposed new development is generally underlain by a surficial layer of stiff to

very stiff, lean to medium plastic clays and sandy clays to the maximum depth explored.

Results of an Atterberg Limits laboratory test performed on samples of representative near-surface soil from

Borings B-2 and B-10 at depths from three to four feet indicated Liquid Limits of 38 and 45 and Plasticity Indices

of 18 and 25, respectively. Based on our visual observations and the laboratory test results, the surficial native

soils are judged to have a low to medium plasticity and a moderate expansion potential.

Our interpretations of the subsurface geologic and soil conditions are presented in Figures 6a & 6b, Cross-Sections

A-A’ and B-B’. Additional details of materials encountered in the exploratory borings, including laboratory test

results, are included in the boring logs in Appendix A, and laboratory test summaries are presented in Appendix

B.

4.2 Groundwater

Groundwater was not encountered in any of the borings drilled to a maximum depth of 10 feet below ground

surface for this study. Groundwater levels can vary in response to time of year, variations in seasonal rainfall, well

pumping, irrigation, and alterations to site drainage. A detailed investigation of local groundwater conditions was

not performed and is beyond the scope of this study.

4.3 Field Infiltration Tests

Geosphere performed a total of four percolation tests in the respective areas of the baseball field, softball field,

and football/soccer field. A hand auger was used to create a vertical boring six to eight-inches in diameter down

to a depth of about 18 inches below the existing surface. All loose soil material was removed from the bottom of

the test holes. A perforated pipe was installed into each hole. About two-inch thickness of drain rock was placed

at the bottom of each hole to prevent scouring when pouring water in. The bored hole was saturated with water

for an hour to allow soils to absorb the water so that steady flow can be achieved during the actual test. After the

initial saturation, percolation rates were monitored over several percolation cycles; once the rate had settled, the

8

average of the final three recorded rates were reported as the groundwater percolation rate for each location. In

addition, the data was adjusted according to the Porchet Method which corrects the method for side effects in

the boring in order to obtain an interpreted vertical infiltration rate. The results of the tests are presented below

in Tables 4.3.1 through 3.3.4.

Table 4.3.1: Percolation Test Results @ 18” Depth Test Location P-1: Football Field Area (See Figure 3)

Tested By: JG Test Date: 3/23/2017

Time Interval (min) Water Level Drop

(in) Percolation Rate

(min/in) Infiltration Rate

(in/hr)

10 0.8 12.5 0.49

30 2.4 12.5 0.51

10 0.8 12.5 0.49

30 2.2 13.6 0.47

Average Infiltration Rate (Inches/hour) 0.49

Table 4.3.2: Percolation Test Results @ 18” Depth Test Location P-2: Football Field Area (See Figure 3)





(in/hr)

10 3.5 2.9 2.30

30 11.3 2.7 3.15

10 3.2 3.1 2.09

30 10.3 2.9 2.77


Table 4.3.3: Percolation Test Results @ 4.5 Feet Depth Test Location P-3: Softball Field Area (See Figure 3)





(in/hr)

10 1.0 10.0 0.22

30 3.1 9.7 0.23

10 0.7 14.3 0.15

30 1.0 30.0 0.07

10 0.6 16.7 0.13

30 0.8 37.5 0.06


9

Table 4.3.4: Percolation Test Results @ 18” Depth Test Location P-4: Baseball Field Area (See Figure 3)





(in/hr)

10 3.0 3.3 1.95

30 6.5 4.6 1.55

10 2.5 4.0 1.60

30 6.1 4.9 1.44


Based on the observed data, the interpreted vertical infiltration rates ranged from 0.14 inches/hour to 2.58

inches/hour. For design of natural drainage systems a factor-of-safety of 2 is recommended. Due to the relatively

low interpreted infiltration rates within the proposed development areas, we do not anticipate using natural

drainage as a viable infiltration option. Therefore, a subsurface drainage system will have to be considered for this

project.

4.4 Corrosion Testing

A sample collected from the upper two to four feet of the soil profile at Boring B-10 was tested to measure sulfate

content, chloride content, redox potential, pH, resistivity, and presence of sulfides. Test results are included in

Appendix B and are summarized on the following table.

Table 4.4.1: Summary of Corrosion Test Results

Soil Description Sample Depth (feet)

Sulfate (mg/kg)

Chloride (mg/kg)

Redox (mV)

Resistivity (ohm-cm)

Sulfide

pH

Dark Gray Sandy CLAY 2 - 4 91 6 369 1,231 Negative 7.4

Water-soluble sulfate can affect the concrete mix design for concrete in contact with the ground, such as shallow

foundations, piles, piers, and concrete slabs. Section 19.3.1.1 in American Concrete Institute (ACI) 318-14, as

referenced by the CBC, provides the following evaluation criteria:

10

Table 4.4.2: Sulfate Evaluation Criteria

Sulfate Exposure

Class Water-Soluble Sulfate in Soil,

Percentage by Mass or (mg/kg)

(ASTM C1580)

Dissolved Sulfate in Water, ppm (ASTM D516 or

D4130)

Cement Type

Max. Water Cementitious

Ratio by Weight

Min. Unconfined

Compressive Strength, psi

Negligible S0 < 0.10 ( < 1,000)

< 150 NA NA NA

Moderate S1 0.10 to < 0.20 (1,000 to <2,000)

150 to < 1,500 II, IP (MS), IS

(MS)

0.50 4,000

Severe S2 0.20 to < 2.00 (2,000 to < 20,000)

1,500 to < 10,000 V 0.45 4,500

Very Severe

S3 Over 2.00 (20,000) Over 10,000 V plus Pozzolan

0.45 4,500

The water-soluble sulfate content was measured to be 91 mg/kg or 0.0091% by dry weight in the soil sample,

suggesting the site soil should have negligible impact on buried concrete structures at the site. However, it should

be pointed out that the water-soluble sulfate concentrations can vary due to the addition of fertilizer, irrigation,

and other possible development activities.

Table 19.3.2.1 in ACI 318-14 suggests use of mitigation measures to protect reinforcing steel from corrosion where

chloride ion contents are above 0.06% by dry weight (of cement). Based on the California Department of

Transportation (Caltrans), if chloride ion content in soil is equal or greater than 500 ppm (0.5% by weight) it is

considered as corrosive. The chloride content was measured to be 6 mg/kg or 0.0006% by dry weight in the soil

sample. Therefore, the test result for chloride content does not suggest a corrosion hazard for mortar-coated steel

and reinforced concrete structures due to high concentration of chloride.

In addition to sulfate and chloride contents described above, pH, oxidation reduction potential (Redox), and

resistivity values were measured in the soil sample. For cast and ductile iron pipes, an evaluation was based on

the 10-Point scaling method developed by the Cast Iron Pipe Research Association (CIPRA) and as detailed in

Appendix A of the American Water Works Association (AWWA) publication C-105, and shown on Table 4.3.3.

11

Table 4.4.3: Soil Test Evaluation Criteria (AWWA C-105)

Soil Characteristics Points Soil Characteristics Points

Resistivity, ohm-cm, based on single probe or water-saturated soil box.

Redox Potential, mV

<700 10 >+100 0

700-1,000 8 +50 to +100 3.5

1,000-1,200 5 0 to 50 4

1,200-1,500 2 Negative 5

1,500-2,000 1 Sulfides

>2,000 0 Positive 3.5

PH Trace 2

0-2 5 Negative 0

2-4 3 Moisture

4-6.5 0 Poor drainage, continuously wet 2

6.5-7.5 0 Fair drainage, generally moist 1

7.5-8.5 0 Good drainage, generally dry 0

>8.5 5

Assuming fair site drainage, the tested soil sample had a total score of 1 point, indicating a potential for low

corrosive rating. When total points on the AWWA corrosivity scale are at least 10, the soil is classified as corrosive

to cast and ductile iron pipe, and use of cathodic corrosion protection is often recommended.

These results are preliminary, and provide information only on the specific soil sampled and tested. Other soil at

the site may be more or less corrosive. Providing a complete assessment of the corrosion potential of the site soils

are not within our scope of work. For specific long-term corrosion control design recommendations, we

recommend that a California-registered professional corrosion engineer evaluate the corrosion potential of the

soil environment on buried concrete structures, steel pipe coated with cement-mortar, and ferrous metals.

12

5.0 CONCLUSIONS AND RECOMMENDATIONS

The following conclusions and recommendations are based upon the analysis of the information gathered during

the course of this study and our understanding of the proposed improvements.

5.1 Conclusions

The site is considered geotechnically suitable for the proposed improvements provided the recommendations of

this report are incorporated into the design and implemented during construction. The predominant geotechnical

issues that need to be addressed at this site are summarized below.

Drainage System – The percolation rates of the subsurface soils were measured to be relatively low, ranging from

0.14 to 2.58 inches/hour. Therefore, a designed subsurface drainage system should be installed beneath the fields

in order to facilitate proper drainage of collected surface water.

Seismic Ground Shaking – The site is located within a seismically active region. As a minimum, the building design,

if any, should consider the effects of seismic activity in accordance with the latest edition of the California Building

Code (CBC).

Expansive Soils –The near-surface soils at the site appear to have a moderate expansion potential. Therefore, no

special treatment is needed to stabilize underneath soils to prevent damage due to expansion and shrinking of

the subgrade soils other than proper moisture conditioning of the subgrade soils immediately prior to construction

of the improvements. However, for potentially sensitive installations such as an artificial turf football field and

track, rendering the field and surrounding track subgrade to a non-expansive condition by chemically treating with

quicklime should be considered. In addition, the recommendations provided in this report to minimize effects of

moderate expansion for all other improvements should be followed.

Winter Construction – If grading occurs in the winter rainy season, appropriate erosion control measures will be

required and weatherproofing of the excavations, athletic tracks, fields, and/or pavement areas should be

considered. Winter rains may also impact subgrade excavations and underground utilities.

Other potential geotechnical considerations, including those that should not significantly impact the project are

explained below.

13

Corrosive Soil – The preliminary corrosion evaluation indicated the test sample was non-corrosive to concrete,

buried cast, and ductile iron pipe.

Groundwater – Groundwater was not encountered at the site within 10 feet at the time of drilling. Therefore,

subsurface groundwater is not expected to significantly impact the proposed improvements.

5.2 Seismic Design Parameters

Structural buildings, if any, should be designed in accordance with local design practice to resist the lateral forces

generated by ground shaking associated with a major earthquake occurring within the greater San Francisco Bay

region. Based on the subsurface conditions encountered in our borings and our evaluation of the geology of the

site, we judge Site Class “D”, representative of stiff soils averaged over the uppermost 100 feet of the subsurface

profile to be appropriate for this site. For design of the proposed site structures in accordance with the seismic

provisions of the CBC 2016 and American Society of Civil Engineers (ASCE) 7-10, the following seismic ground

motion values should be used for design.

Table 5.2.1: Seismic Coefficients Based on 2016 CBC (per ASCE 7-10)

Item Value 2013 CBC SourceR1 ASCE 7-10

Table/FigureR2

Site Class D Table 1613A.3.2. Table 20.3-1

Mapped Spectral Response Accelerations Short Period, Ss 1-second Period, S1

1.747g 0.613g

Figure 22-1 Figure 22-2

Site Coefficient, Fa 1.0

Table 1613A.3.3(1)

Table 11.4-1

Site Coefficient, Fv 1.5

Table 1613A.3.3(2)

Table 11.4-2

MCE (SMS) 1.747g Equation 16A-37 Equation 11.4-1

MCE (SM1) 0.920g Equation 16A-38 Equation 11.4-2

Design Spectral Response Acceleration Short Period, SDS 1-second Period, SD1

1.165g 0.613g

Equation 16A-39 Equation 16A-40

Equation 11.4-3 Equation 11.4-4

Modified Peak Ground Acceleration (PGAM) 0.662g

R1 California Building Standards Commission (CBSC), “California Building Code,” 2013 Edition. R2 U.S. Seismic “Design Maps” Web Application, https://geohazards.usgs.gov/secure/designmaps/us/application.php

ASCE 7-15 § 11.6-1 and 11.6-2 indicate that the Seismic Design Category for all Occupancy Categories is “D”.

https://geohazards.usgs.gov/secure/designmaps/us/application.php

14

5.3 Site Grading

5.3.1 General Grading, Fill Material Requirements and Site Drainage

Site grading is generally anticipated to consist of minor cuts and fills required to construct the athletic track and

field as well as the baseball and softball fields to establish new site grades as required. Existing onsite soils

generated from cut areas following clearing and grubbing that is free of organic material (three percent or less by

weight) or debris is suitable for use as structural, non-select fill at the site, as approved by the Geotechnical

Engineer. Imported select fill, if any, should be non-expansive, having a Plasticity Index of 15 or less, an R-Value

greater than 40, and enough fines so the soil can bind together. Imported soils should be free of organic materials

and debris, and should not contain rocks or lumps greater than three inches in maximum size. The Geotechnical

Engineer should approve imported fill prior to delivery onsite.

Final grading should be designed to provide drainage away from athletic fields or provide adequate subsurface

drainage system. Adjacent concrete hardscape should slope a minimum two percent away from buildings or

structures, if any. Roof leaders and downspouts, if any, should not discharge into landscape areas adjacent to

buildings, and should discharge onto paved surfaces sloping away from the structure or into a closed pipe system

channeled away from the structure to an approved collector or outfall.

5.3.2 Site Preparation and Demolition

Site grading should be performed in accordance with these recommendations. A pre-construction conference

should be held at the jobsite with representatives from the owner, general contractor, grading contractor, and

Geosphere prior to starting the clearing and demolition operations at the site.

Prior to commencement of grading activities, areas to receive fill, structures, or pavements should be cleared of

existing surface vegetation, organic-laden soils, building materials including foundations if present, existing loose

soil, concrete, asphalt concrete (AC) and aggregate base (AB) pavement sections, debris and other deleterious

materials. Debris resulting from site stripping operations should be removed from the site, unless otherwise

permitted by the Geotechnical Engineer.

Excavations resulting from the removal of abandoned underground utilities, or deleterious materials should be

cleaned down to firm soil, processed as necessary, and backfilled with engineered fill in accordance with the

grading sections of this report. The Geotechnical Engineer’s representative should verify the adequacy of site

clearing operations during construction, prior to placement of engineered fill.

15

Existing underground utilities proposed to be abandoned, if present, should be properly grouted, closed, or

removed as needed. If the utilities are removed, the excavations should be backfilled with properly compacted fill

or other material approved by the Geotechnical Engineer. The extent of removal/abandonment depends on the

diameter of the pipe, depth of the pipe, and proximity to buildings and pavement.

5.3.3 Project Compaction Recommendations

The following table provides the recommended compaction requirements for this project. Not all soils, aggregates

and scenarios listed below may be applicable for this project. Specific grading recommendations are discussed

individually within applicable sections of this report.

Table 5.3.3.1: Project Compaction Requirements

Description Min. Percent Relative Compaction

(per ASTM D1557)

Relative to Optimum

Moisture Content

Fill Areas, Engineered Fill, Onsite Soil 90 + 3

Fill Areas, Engineered Fill, Select Fill 90 ± 3

Athletic Fields, Onsite Soil – scarified subgrade or used as Fill 90 + 3

Athletic Fields, Aggregate Base or Select (non-expansive) Engineered Fill

90 + 3

Athletic Fields – Treated Soil 90 ± 3

Concrete Flatwork, Subgrade Soil 90 + 3

Concrete Flatwork, Aggregate Base 90 ± 3

Underground Utility Backfill 90 + 3

AC Pavement – Onsite Subgrades (upper 12 inches) 95 + 3

AC Pavement – Non-Expansive Subgrades in Non-Traffic (e.g., Field) Areas (upper 12 inches)

90 ± 3

Pavement – Class 2 Aggregate Base Section 95 ± 3

5.3.4 Athletic Fields (Football, Softball & Baseball) Grading

After demolition, site preparation, and grading to the required subgrade level, all of the field subgrade soil should

be scarified to a depth of at least eight inches, moisture conditioned to at least three percent over optimum

moisture, and compacted to the project compaction requirements listed on the above table as determined by

ASTM D1557 (Modified Proctor). If loose or soft soil is encountered, these soils should be removed to expose firm

soil and backfilled with engineered fill. Engineered fill should be placed in maximum eight-inch thick, pre-

16

compacted lifts. The fill should be moisture conditioned and thoroughly mixed during placement to provide

uniformity in each layer. After the final compacted soil subgrade has been reached, a minimum six-inch thick layer

of Aggregate Base (AB) should be placed immediately after grading to protect the subgrade soil from drying.

Alternatively, the soil subgrade should be kept moist by watering until aggregate base or other field surface

material is placed. After the field soil subgrade is prepared, the artificial turf section with an AB layer as applicable

and with proper designed drainage system should be installed.

As an additional measure of protection against surface volume change effects on artificial turf and track sections,

consideration should be given to chemically treating the graded turf and track subgrade to a non-expansive

condition using quicklime. For design purposes, a three percent by dry weight mixture of quicklime added to the

upper 12 inches of turf/track subgrade may be considered. Quicklime treatment of the field/track subgrades may

also double as winterizing stabilization of the subgrade should construction take place during the wet season

(Section 5.3.6). Note: If the subgrade is lime treated, the six-inch thick AB section may be eliminated.

We should be given an opportunity to review the final proposed artificial turf section for this project. Re-evaluation

of the subgrade preparation recommendations may be required depending upon the specifically proposed design

section for the artificial turf.

5.3.5 Grading Flatwork Areas and Athletic Tracks

Areas to receive flatwork or asphalt concrete (AC) pavements below track surfaces should be scarified to a depth

of eight inches below existing grade or final subgrade, whichever is lower. Scarified areas should be moisture

conditioned and compacted. Where required, engineered fill should be placed and compacted to reach design

subgrade elevation. Once the compacted pavement subgrade has been reached, it is recommended that a

minimum of six inches of AB in paved (i.e., athletic tracks) and four inches of AB on-grade concrete slab areas be

placed immediately after grading to protect the subgrade soil from drying. Alternatively, the subgrade should be

kept moist by watering until AB is placed, or the artificial track surface pavement subgrade may be lime treated

as described in Section 5.3.4. If the track subgrade is lime treated, the AB section underlying AC may be omitted.

If an AB section is placed under the track AC course, the AB section should be vertically cut off along the pavement

boundaries using a deepened concrete curb or header to reduce the potential for moisture to migrate under the

pavement section. Cutoffs should extend a minimum two inches below the bottom of the AB layer.

17

Rubber-tired heavy equipment, such as a full water truck, should be used to proofload exposed subgrade areas

where pumping is suspected. Proof loading will determine if the subgrade soil is capable of supporting

construction equipment without excessive pumping or rutting.

5.3.6 Site Winterization and Unstable Subgrade Conditions

If grading occurs in the winter rainy season, unstable and unworkable subgrade conditions may be present and

compaction of onsite soils may not be feasible. These conditions may be remedied using soil admixtures, such as

lime. A four percent mixture of lime based on a soil unit weight of 125 pcf is recommended for planning purposes.

Treatment should vary between 8 to 12 inches, depending on the anticipated construction equipment loads and

degree of observed subgrade instability. More detailed and final recommendations can be provided during

construction. Stabilizing subgrade in small, isolated areas can be accomplished with the approval of the

Geotechnical Engineer by over-excavating one foot, placing Tensar TriAx TX-140, BX1100, or equivalent geogrid

on the soil, and then placing at least 12 inches of Class 2 aggregate base on the geogrid. The upper six inches of

the aggregate base should be compacted to at least 90 percent relative compaction.

5.4 Utility Trench Construction

5.4.1 Trench Backfilling

Utility trenches may be backfilled with onsite soil above the utility bedding and shading materials. If rocks or

concrete larger than four inches in maximum size are encountered, they should be removed from the fill material

prior to placement in the utility trenches. Utility bedding and shading compaction requirements should be in

conformance with the requirements of the local agencies having jurisdiction and as recommended by the pipe

manufacturers. Jetting of trench backfill is not recommended. Compaction recommendations are presented in

Table 5.3.3.1.

If rain is expected and the trench will remain open, the bottom of the trench may be lined with one to two inches

of gravel. This would provide a working surface in the trench bottom. The trench bottom may have to be sloped

to a low point to pump the water out of the trench.

5.4.3 Pipe Bedding and Shading

Pipe bedding material is placed in the utility trench bottom to provide a uniform surface, a cushion, and protection

for the utility pipe. Shading material is placed around the utility pipe after installation and testing to protect the

pipe. Bedding and shading material and placement are typically specified by the pipe manufacturer, agency, or

18

project designer. Agency and pipe manufacturer recommendations may supersede our suggestions. These

suggestions are intended as guidelines and our opinions based on our experience to provide the most cost-

effective method for protecting the utility pipe and surrounding structures. Other geotechnical engineers, agency

personnel, contractors, and civil engineers may have different opinions regarding this matter.

Bedding and Shading Material - The bedding and shading material should be the same material to simplify

construction. The material should be clean, uniformly graded, fine to medium grained sand. It is suggested that

bedding and shading material contain less than three percent fines with 100 percent passing the No. 8 sieve.

Coarse sand, angular gravel or aggregate base should be avoided since this type of shading material may bridge

when backfilling around the pipe, possibly creating voids, and may be too stiff as bedding material. Open graded

gravel should be avoided for shading since this material contains voids, and the surrounding soil could wash into

the voids, potentially causing future ground settlement. However, open graded gravel may be required for

bedding material when water is entering the trench. This would provide a stable working surface and a drainage

path to a sump pit in the trench for water in the trench. The maximum size for bedding material should be limited

to about ¾ -inch.

Bedding Material Placement - The thickness of the bedding material should be minimized to reduce the amount

of trench excavation, soil export, and imported bedding material. Two to three inches for pipes less than eight-

inches in diameter and about four to six inches for larger pipes are suggested. Bedding for very large diameter

pipes are typically controlled by the pipe manufacturer. Compaction is not required for thin layers of bedding

material. The pipe needs to be able to set into the bedding, and walking on a thin layer of bedding material should

sufficiently compact the sand. Rounded gravel may be unstable during construction, but once the pipe and shading

material is in place, the rounded gravel will be confined and stable.

Shading Material Placement – Jetting is not typically recommended since the type of shading material is unknown

when preparing the geotechnical report and agencies typically do not permit jetting. If the sand contains fines or

if the sand is well graded, jetting will not work. Additionally, if too much water is used during jetting, this could

create a wet and unstable condition. However, clean, uniformly graded and fine to medium sand can be placed

by jetting. The shading material should be able to flow around and under the utility pipe during placement. Some

compactive effort along the sides of the pipe should be made by the contractor to consolidate the shading material

around the pipe. A minimum thickness of about six-inches of shading material should be placed over the pipe to

protect the pipe from compaction of the soil above the shading material. The contractor should provide some

19

compactive effort to densify the shading material above the pipe. Relative compaction testing is not usually

performed on the shading material. However, the contractor is ultimately responsible for the integrity of the utility

pipe.

5.5 Pier Foundations

Foundations for bleacher structures, light towers, poles, and other athletic field features such as scoreboards and

goal post poles, if any, may consist of drilled pier foundations deriving their vertical supporting capacity through

skin friction between the side surfaces of the foundations and the adjacent soil. For design purposes, the allowable

skin friction for gravity loads may be assumed to be 400 psf for the portion of pier embedded in competent native

soils or engineered fills. These values assume a safety factor of 2, and may be increased by one-third for seismic

or transient loads. Uplift loads should be limited to two-thirds of these values. For piers situated adjacent to or on

slopes, the portion of pier with horizontal cover less than 10 feet, measured from outside perimeter of the pier to

the slope surface should be neglected in computing vertical capacity.

Lateral resistance for drilled pier foundations may be determined for onsite soils using an allowable passive

resistance equal to an equivalent fluid weighing 350 pounds per cubic foot (pcf) acting against the foundation for

lateral load resistance against the sides of foundations perpendicular to the direction of loading where the

foundation is poured neat against undisturbed material (i.e., native soils, engineered fills or existing fills). The top

foot of passive resistance at foundations not adjacent to and confined by pavement, interior floor slab, or

hardscape should be neglected. For pier foundations, passive pressure can be assumed to act across two times

the pier diameter. For piers situated adjacent to or on slopes, the portion of pier with horizontal cover less than

10 feet, measured from outside perimeter of the pier to the slope surface should be neglected in computing lateral

capacity.

5.6 Exterior Concrete Flatwork

Exterior concrete flatwork with pedestrian traffic should be at least four-inches thick. If an underlying aggregate

base layer is used, the AB layer should be at least four inches thick and should be cut off from direct moisture

transmission from directly adjacent landscape areas by use of a concrete cutoff or a deep header board extending

at least two inches below the base of the aggregate base layer. In any case, due to the moderately expansive

conditions, we recommend that the upper eight-inches of flatwork subgrade be moisture conditioned to a

minimum of three to five percent over optimum moisture. This moisture should be verified within 24 hours of

placing aggregate base over the subgrade and again prior to concrete pouring.

20

5.7 Athletic Track Asphalt Concrete Pavements

R-value testing was conducted on a representative soil sample of potential subgrade material. Laboratory test

results indicated a measured R-Value of 30. Based on the test result and anticipated loading, we recommend using

a minimum three-inch thickness of ½” nominal maximum size asphalt concrete (AC) mix underlain by a six-inch

thick layer of Class 2 aggregate base (AB) on the compacted subgrade. However if the subgrade is lime treated, as

discussed in Section 5.3.4, we recommend a minimum four-inch thickness of ½” nominal maximum size AC mix

placed directly over the lime treated subgrade (i.e., AB layer not required).

5.8 Plan Review

We recommend that Geosphere be provided the opportunity to review the final project plans prior to

construction. The purpose of this review is to assess the general compliance of the plans with the

recommendations provided in this report and confirm the incorporation of these recommendations into the

project plans and specifications.

5.9 Observation and Testing During Construction

We recommend that Geosphere be retained to provide observation and testing services during site preparation,

mass grading, underground utility construction, foundation excavation, and to observe final site drainage. This is

to observe compliance with the design concepts, specifications and recommendations, and to allow for possible

changes in the event that subsurface conditions differ from those anticipated prior to the start of construction.

21

6.0 VALIDITY OF REPORT

This report is valid for three years after publication. If construction begins after this time period, Geosphere should

be contacted to confirm that the site conditions have not changed significantly. If the proposed development

differs considerably from that described above, Geosphere should be notified to determine if additional

recommendations are required. Additionally, if Geosphere is not involved during the geotechnical aspects of

construction, this report may become wholly or in part invalid; Geosphere’s geotechnical personnel should be

retained to verify that the subsurface conditions anticipated when preparing this report are similar to the

subsurface conditions revealed during construction. Geosphere’s involvement should include grading and

foundation plan review, grading observation and testing, foundation excavation observation, and utility trench

backfill testing.

22

7.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS

The recommendations of this report are based upon the soil and conditions encountered in the borings. If

variations or undesirable conditions are encountered during construction, Geosphere should be contacted so that

supplemental recommendations may be provided.

This report is issued with the understanding that it is the responsibility of the owner or his representatives to see

that the information and recommendations contained herein are called to the attention of the other members of

the design team and incorporated into the plans and specifications, and that the necessary steps are taken to see

that the recommendations are implemented during construction.

The findings and recommendations presented in this report are valid as of the present time for the development

as currently proposed. However, changes in the conditions of the property or adjacent properties may occur with

the passage of time, whether by natural processes or the acts of other persons. In addition, changes in applicable

or appropriate standards may occur through legislation or the broadening of knowledge. Accordingly the findings

and recommendations presented in this report may be invalidated, wholly or in part, by changes outside our

control. Therefore, this report is subject to review by Geosphere after a period of three (3) years has elapsed from

the date of issuance of this report. In addition, if the currently proposed design scheme as noted in this report is

altered Geosphere should be provided the opportunity to review the changed design and provide supplemental

recommendations as needed.

Recommendations are presented in this report which specifically request that Geosphere be provided the

opportunity to review the project plans prior to construction and that we be retained to provide observation and

testing services during construction. The validity of the recommendations of this report assumes that Geosphere

will be retained to provide these services.

This report was prepared upon your request for our services, and in accordance with currently accepted

geotechnical engineering practice. No warranty based on the contents of this report is intended, and none shall

be inferred from the statements or opinions expressed herein.

The scope of our services for this report did not include an environmental assessment or investigation for the

presence or absence of wetlands or hazardous or toxic materials in the soil, surface water, groundwater or air, on,

below or around this site. Any statements within this report or on the attached figures, logs or records regarding

odors noted or other items or conditions observed are for the information of our client only.

23

8.0 REFERENCES

American Society for Testing and Materials, West Conshohocken, Pennsylvania. American Society of Civil Engineers (ASCE), third printing 2013, Minimum Design Loads for Buildings and Other Structures; Standard 7-10.

California Building Code, 2016, Title 24, Part 2. California Department of Transportation (Caltrans); California Standard Specifications, 2015. California Geological Survey, 2008, Guidelines for evaluating and mitigating seismic hazards in California: California Geological Survey Special Publication 117A, 98 p.

Dibblee, T.W. Jr., 2006, Geologic Map of the Clayton Quadrangle, Contra Costa County, California: Santa Barbara Museum of Natural History, Dibblee Geology Center Map #DF-192, edited by Minch, J.A., scale 1:24,000. Graymer, R.W., Moring, B.C., Saucedo, G.J., Wentworth, C.M., Brabb, E.E., and Knudsen, K.L., 2006, Geologic Map of the San Francisco Bay Region, California: U.S. Geological Survey Scientific Investigations Map 2918, Scale 1:275,000. Jennings, C.W., and Bryant, W.A., compilers, 2010: 2010 Fault activity map of California: California Geological Survey, Geologic Data Map No. 6, scale 1:750,000, with 94-page Explanatory Text booklet. Page, B.M., 1966, Geology of the Coast Ranges of California: in Bailey, E.H., Jr., editor, Geology of Northern California: California Geological Survey Bulletin 190, p. 255-276. 2007 Working Group on California Earthquake Probabilities (WGCEP), 2008, The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2): U.S. Geological Survey Open-File Report 2007-1437. U. S. Geological Survey Earthquake Information Center, 2012, website, earthquake.usgs.gov Publications may have been used as general reference and not specifically cited in the report text.

FIGURES

Figure 1 - Site Vicinity Map Figure 2 - Development Site Plan

Figure 3 - Site Plan and Site Geology Map Figure 4 - Site Vicinity Geology Map

Figure 5 – Regional Fault Map Figure 6a - Geological Cross Section A-A’ Figure 6b - Geological Cross Section B-B’

158

160

162

164

166

168

170

172

174

176

0 50 100 150 200 250 300 350 400158

160

162

164

166

168

170

172

174

176

0 50 100 150 200 250 300 350 400

Schematic Geologic Cross-Section A-A'Distance Along Baseline (ft)

SUBSURFACE DIAGRAM

A

Ele

va

tio

n (

ft)

CL - Unified Soil Classification System (USCS)14 - Blows Per Six Inches, Standard Penetration Test(21) - N Value

A'

CLIENT Mount Diablo Unified School District

PROJECT NUMBER 91-03875-A

PROJECT NAME Concord High School - Athletic Fields

PROJECT LOCATION 4200 Concord Boulevard, Concord, California 94521

2001 Crow Canyon Road, Suite 210San Ramon, CA 94583Telephone: (925) 314-7100Fax: (925) 855-7140

4-4-5(9)

3-4-8(12)

2-4-3(7)

CL

CL

5-10-12(22)

5-5-11(16)

2-3-3(6)

CL

CL

4-5-8(13)

4-5-10(15)

12-13-17(30)

CL

CL

CL

3-4-6(10)

3-5-6(11)

4-5-10(15)

CL

CL

5-6-6(12)

3-3-6(9)

4-4-5(9)

CL

CL

4-5-7(12)

6-7-13(20)

3-3-4(7)

CL

5-6-8(14)

3-3-5(8)

9-16-30(46)

CL

CL

GS

Figure a

B- 1 B- 2

B- 4

B- 6

B- 9

B-10

B-11

164

165

166

167

168

169

170

171

172

173

174

175

0 20 40 60 80 100 120 140164

165

166

167

168

169

170

171

172

173

174

175

0 20 40 60 80 100 120 140

Distance Along Baseline (ft)

SUBSURFACE DIAGRAME

leva

tio

n (

ft)

CL - Unified Soil Classification System (USCS)14 - Blows Per Six Inches, Standard Penetration Test(21) - N Value






3-4-5(9)

5-8-10(18)

5-9-16(25)

CL

GC

5-6-6(12)

3-3-6(9)

4-4-5(9)

CL

CL

3-6-11(17)

5-6-9(15)

6-10-23(33)

GS

CL

GC

Figure bSchematic Geologic Cross-Section B-B'

B B'

B- 7B- 9B-12

APPENDIX A

Key to Boring Log Symbols Boring Logs

KEY TO EXPLORATORY BORING LOGS

110

PLASTICITY CHART

LIQUID LIMITS (%)

PLA

ST

ICIT

Y IN

DE

X (

%)

"A" L

INE

CL-ML

CL-OL

CH-OH

OL-M

L

OH-MH

0-30(Low)

30-50(Medium)

>50(High)

50

60

40

30

20

10

050 60403020100 100908070

Grab Bulk Sample Initial Water Level Reading

Shelby Tube

Standard Penetration Test

2.5 Inch Modified California

Final Water Level Reading

No Recovery

Blow Count

The number of blows of the sampling hammer required to drive the sampler through each of three 6-inch increments. Less than three increments may be reportedif more than 50 blows are counted for any increment.The notation 50/5” indicates 50 blows recorded for 5 inches of penetration.

N-Value

Number of blows 140 LB hammer falling 30 inchesto drive a 2 inch outside diameter (1-3/8 inch I.D)split barrel sampler the last 12 inches of an 18inch drive (ASTM-1586 Standard Penetration Test)

CU -DS - Results of Direct Shear test in terms of total cohesion (C, KSF) or effective cohesion and friction angles (C’, KSF and degrees)LL - Liquid LimitPI - Plasticity IndexPP - Pocket Penetrometer testTV - Torvane Shear Test results in terms of undrained shear strength (KSF)UC - Unconfined Compression test results in terms of undrained shear strength (KSF)#200 - Percent passing number 200 sieveCu - Coefficient of UniformityCc - Coefficient of Concavity

Consolidated Undrained triaxial test completed. Refer to laboratory results

General Notes

1. The boring locations were determined by pacing, sighting and/or measuring from site features. Locations are approximate. Elevations of borings (if included) were determined by interpolation between plan contours or from another source that will be identified in the report or on the project site plan. The location and elevation of borings should be consideredaccurate only to the degree implied by the method used.

2. The stratification lines represent the approximate boundary between soil types. The transition may be gradual.

3. Water level readings in the drill holes were recorded at time and under conditions stated on the boring logs. This data has been reviewed and interpretations have been made in the text of this report. However, it must be noted that fluctuations in the level of the groundwater may occur due to variations in rainfall, tides, temperature and other factors at the time measurements were made.

4. The boring logs and attached data should only be used in accordance with the report.

COMPONENTS

PARTICLES SIZES

SIZE OR SIEVE NUMBER

Cu<4 and or [ 1 or Cc 3]Cc< >

Cu<6 and or [Cc<1 or Cc>3]

>

MC1-1

MC1-2

MC1-3

106 17

3" TOPSOIL : (CL) CLAY : Dark brown, moist, stiff, w/ organics.

(CL) CLAY : Brown, moist, stiff, w/ gravels.

Gravelly Sand Lense.

becomes medium stiff.

Bottom of borehole at 10.0 feet.

4-4-5(9)

3-4-8(12)

2-4-3(7)

3.3

3.8

1.5

NOTES

GROUND ELEVATION 166 ft

LOGGED BY JG

DRILLING METHOD Hollow Stem Auger 8"

HOLE SIZE 8 inches

DRILLING CONTRACTOR Exploration Geoservices Inc. GROUND WATER LEVELS:

CHECKED BY CTD

DATE STARTED 3/3/17 COMPLETED 3/3/17

AT TIME OF DRILLING ---

AT END OF DRILLING ---

AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10

MATERIAL DESCRIPTION

SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 1






MC2-1

MC2-2

MC2-3

112 18 38 20 18 6518

3" TOPSOIL : (CL) CLAY : Dark brown, moist, very stiff, w/ some gravelsand organics.

(CL) SANDY CLAY : Brown, moist, very stiff, w/ fine sand andgravels.

Clayey Sand Lense.

becomes moist to very moist, medium stiff.


5-10-12(22)

5-5-11(16)

2-3-3(6)

3.3

4.5

1.5

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 2






MC3-1

MC3-2

MC3-3

106 20

3" TOPSOIL : (CL) CLAY : Dark brown, moist, stiff, w/ some gravels andorganics.


becomes moist to very moist, medium stiff.


4-5-6(11)

4-5-7(12)

2-3-2(5)

2.5

4.0

1.3

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 3






MC4-1

MC4-2

MC4-3

3" TOPSOIL : (CL) CLAY : Dark brown, moist, stiff, w/ some gravels andorganics.

(CL) CLAY : Brown, moist, very stiff, w/ gravels.

(CL) GRAVELLY CLAY : Brown, moist, hard, w/ sand.


4-5-8(13)

4-5-10(15)

12-13-17(30)

2.8

>4.5

>4.5

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 4






MC5-1

MC5-2

MC5-3

110 18

3" TOPSOIL : (CL) CLAY : Dark brown, moist, very stiff.


(GS) SANDY CLAYEY GRAVEL : Brown, moist, mediumdense.


8-12-12(24)

3-3-6(9)

6-8-11(19)

3.5

3.8

2.0

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 5






MC6-1

MC6-2

MC6-3

102 22 69

3" TOPSOIL : (CL) SANDY CLAY : Dark brown, moist, stiff, fine.

(CL) CLAY : Brown, moist, stiff.

becomes very stiff, w/ gravels.


3-4-6(10)

3-5-6(11)

4-5-10(15)

3.8

4.0

3.5

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 6






MC7-1

MC7-2

MC7-3

104 24

1" AGGREGATE BASE : Gray

(CL) CLAY : Dark brown, moist, stiff, w/ some gravels.

becomes very stiff.

(GC) SANDY CLAYEY GRAVEL : Mottled brown, olive, red,and orange, damp, medium dense.


3-4-5(9)

5-8-10(18)

5-9-16(25)

3.5

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 7






MC8-1

MC8-2

MC8-3

107

114

21

16

9" GRAVELLY SAND : Gray, w/ fine gravels

(GS) GRAVEL w/ SAND : Gray, damp, medium dense.

(CL) CLAY : Dark brown, moist, very stiff.

becomes stiff, w/ traces of fine gravels.

(GC) SANDY CLAYEY GRAVEL : Mottled brown, olive, red,and orange, moist, very dense.


4-5-10(15)

4-4-8(12)

25-33

2.8

3.3

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 8






MC9-1

MC9-2

MC9-3

100 24 76

3" TOPSOIL : (CL) CLAY w/ SAND : Dark brown, moist, stiff, fine.

(CL) CLAY : Brown, moist.

becomes stiff.


5-6-6(12)

3-3-6(9)

4-4-5(9)

1.5

3.0

2.5

NOTES


LOGGED BY JG


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B- 9






MC10-1

MC10-2

MC10-3

105

105

21

19

45 20 25 8325

3" TOPSOIL : (CL) CLAY w/ SAND : Dark brown, moist, stiff, w/ fine sandand traces of gravel.

becomes very stiff.

becomes dark brown to brown, medium stiff.


4-5-7(12)

6-7-13(20)

3-3-4(7)

2.3

4.3

2.6

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B-10






MC11-1

MC11-2

MC11-3

109 17

3" TOPSOIL : (CL) CLAY : Dark brown, moist, stiff, w/ traces of gravels.

(CL) CLAY : Brown, moist, stiff, w/ some gravels.

(GS) SANDY CLAYEY GRAVEL : Mottled brown, olive, red,and orange, damp, dense.


5-6-8(14)

3-3-5(8)

9-16-30(46)

3.8

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B-11






MC12-1

MC12-2

MC12-3

97

110

24

17

9" SAND : Gray, w/ fine gravel

(GS) GRAVEL w/ SAND : Gray, damp, medium dense.

(CL) CLAY : Dark brown, moist, very stiff, w/ traces of gravels.

(GC) SANDY CLAYEY GRAVEL : Mottled brown, olive, red,and orange, moist, dense.


3-6-11(17)

5-6-9(15)

6-10-23(33)

0.50

3.3

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B-12






MC13-1

MC13-2

MC13-3

100 24

3" TOPSOIL : (CL) CLAY : Brown, moist, stiff, w/ traces of organics.

w/ traces of gravels.

becomes lighter brown, medium stiff.


3-4-8(12)

4-4-10(14)

2-3-3(6)

1.3

3.3

1.6

NOTES


LOGGED BY NA


HOLE SIZE 8 inches


CHECKED BY CTD




AFTER DRILLING ---

SA

MP

LE

TY

PE

NU

MB

ER

RE

CO

VE

RY

%(R

QD

)

DR

Y U

NIT

WT

.(p

cf)

MO

IST

UR

EC

ON

TE

NT

(%

)

LIQ

UID

LIM

IT

PL

AS

TIC

LIM

IT

PL

AS

TIC

ITY

IND

EX

FIN

ES

CO

NT

EN

T(%

)

ATTERBERGLIMITS

PL

AS

TIC

ITY

IND

EX

GR

AP

HIC

LO

G

DE

PT

H(f

t)

0

5

10


SP

T B

LO

WC

OU

NT

S(N

VA

LU

E)

PO

CK

ET

PE

N.

(tsf)

PAGE 1 OF 1

BORING NUMBER B-13






APPENDIX B LABORATORY TEST RESULTS

Liquid and Plastic Limits Test Report

Sieve Analysis Results R-Value Test Result

Corrosivity Test Summary

Tested By: MA Checked By:

Dark brown sandy CLAY. 38 20 18 85.6 65.3 CL

Brownish black lean CLAY with sand. 45 20 25 95.0 82.9 CL

91-03875-A Geosphere Consultants,Inc.

MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS

Project No. Client: Remarks:

Project:

Soil Mechanics Lab

Oakland, California Plate

Depth: 4.5' Sample Number: B-2 2-2

Depth: 4.5' Sample Number: B-10 10-2

PLA

ST

ICIT

Y I

ND

EX

0

10

20

30

40

50

60

LIQUID LIMIT0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

CL o

r OL

CH o

r OH

ML or OL MH or OH

Dashed line indicates the approximateupper limit boundary for natural soils

4

7

LIQUID AND PLASTIC LIMITS TEST REPORT

Concord HS-Athletic Fields

Tested By: MA Checked By:

Soil Mechanics Lab

Oakland, California

Client:

Project:

Project No.: Plate

Geosphere Consultants,Inc.

Concord HS-Athletic Fields

91-03875-A

SYMBOL SOURCESAMPLE DEPTH

Material Description USCSNO. (ft.)

SOIL DATA

PE

RC

EN

T F

INE

R

0

10

20

30

40

50

60

70

80

90

100

GRAIN SIZE - mm.

0.0010.010.1110100

% +3"Coarse

% Gravel

Fine Coarse Medium

% Sand

Fine Silt

% Fines

Clay

0.0 0.0 4.7 4.3 5.4 20.3 65.3

0.0 0.0 5.8 1.4 3.7 20.2 68.9

0.0 0.0 4.1 3.3 3.2 13.3 76.1

0.0 0.0 0.7 1.5 2.8 12.1 82.9

6 in.

3 in.

2 in.

1½

in.

1 in.

¾ in.

½ in.

3/8

in.

#4

#10

#20

#30

#40

#60

#100

#140

#200

Particle Size Distribution Report

B-2 2-2 4.5' Dark brown sandy CLAY. CL

B-6 6-1 2' Dark brown sandy CLAY. CL

B-9 9-1 2' Brownish black lean CLAY with sand. CL

B-10 10-2 4.5' Brownish black lean CLAY with sand. CL

R-VALUE TEST REPORT

CONSOLIDATED ENGINEERING LABORATORIES -- SAN RAMON, CA

R-VALUE TEST REPORT

Date: 4/5/2017

Project No.: 9103875A

Project:Concord High School-Athletic Improvements

Location: B-8 Depth @ 2.5"

Sample Number: 10S170405-1

Remarks:

Checked by: WY

Tested by: JLA

Brown Fat Clay with Gravel

Sampled on 3/3/17 by N. Anastasio

10S170405-1

Material DescriptionTest Results

No.

Compact.

Pressure

psi

Density

pcf

Moist.

%

Expansion

Pressure

psi

Horizontal

Press. psi

@ 160 psi

Sample

Height

in.

Exud.

Pressure

psi

R

Value

R

Value

Corr.

Resistance R-Value and Expansion Pressure - ASTM D 2844

R-value at 300 psi exudation pressure = 30

1 160 116.5 17.0 0.00 104 2.50 316 32 32

2 130 116.9 17.1 0.00 114 2.50 239 27 27

3 180 117.5 16.1 0.00 94 2.50 427 41 41

Exudation Pressure - psi

R

-valu

e

100 200 300 400 500 600 700 8000

20

40

60

80

100

CTL # Date: PJ

Client: Project:Remarks:

Chloride pH Sulfide MoistureAs Rec. Min Sat. mg/kg mg/kg % Qualitative At Test

Dry Wt. Dry Wt. Dry Wt. EH (mv) At Test by Lead %Boring Sample, No. Depth, ft. ASTM G57 Cal 643 ASTM G57 ASTM D4327 ASTM D4327 ASTM D4327 ASTM G51 ASTM G200 Temp °C Acetate Paper ASTM D2216

B-10 - 2-4 - - 1,231 6 91 0.0091 7.4 369 20 Negative 23.3 Dark Gray Sandy CLAY

Corrosivity Tests Summary

(Redox)

PJ

91-03875-A

Resistivity @ 15.5 °C (Ohm-cm)

Proj. No:Checked:3/10/2017

Geosphere Consultants

Soil Visual Description

724-155

Concord HS Athletic Field

Sample Location or ID Sulfate ORP

Tested By:

Date post:	11-Apr-2022
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

GEOTECHNICAL ENGINEERING STUDY Athletic Field …

Documents