STATE OF CALIFORNIA - THE RESOURCES AGENCY PETE UILSON Governor

gEPARTMEMt OF CONS~~VATI(llfj

DIVISION Of MINES AND GEOLOGY BAY AREA REGIONAL OFFICE 185 Berry Street, Suit~ 3600 San Franc;sco, CA 94107 Phon• (415) 904-7707

ATSS 539-7707 Fax (415) 904-7715

Curt Johnston, Asst. Director Dept. of Planning & Development 1000 Webster Street Fairfield, CA 94533

Dear Mr. Johnston:

• December 13, 1993

We are placing on open file the following report, submitted by the City of Fairfield in compliance with the Alquist-Priolo Special Studies Zones Act:

Alquist-Priolo study of Cordelia fault, Grobric Court, Cordelia, CA; by Engeo, Inc.; 8/14/84; plus Geotechnical investigation report for proposed Goodwill Industries Bldg., Lots 4 & 5, Grobric Court, Cordelia; by Balbi & Chang Assoc., 7/9/90.

Please note that, while the Engeo report does not identify the Cordelia fault, its trenches were rather shallow. Subsequent deeper trenching by Caltrans revealed faulted soils in the vicinity of the west end of Engeo•s trench 1. The location of the Cordelia fault also was verified by trenching just north of Highway I-80 and by air photo interpretation to the south. (This information is summarized in our 1981 Fault Evaluation Report FER-127 (with Supplements of 5/20/83 and 12/16/91) on the Cordelia fault, which is on file with the Fairfield Public Library.) Thus, the Cordelia fault appears to project through the subject site, possibly between Engeo•s trenches 1 and 3. You may wish to consider this in future development of the site and vicinity.

Please call me if you have any questions (415-904-7728).

EWH:ra cc: A-P filei-/

Sincerely,

EARL W. HART, CEG 935 senior Geologist &

Program Manager

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[707] 428-7461 DEPARTMENT OF PLANNING AND DEVELOPMENT

December 9, 1993

Mr. Earl Hart, Program Manager 185 Berry Street San Francisco, CA 94107

RE: Geologic Reports for Projects within the Alquist-Priolo Study Zone

Dear Mr. Hart:

This letter will serve as response to the letter from James F.Davis, State Geologist, dated December 1, 1993. This letter noted that the City of Fairfield had not submitted any geologic reports for projects within Special Study Zones to your office within the past four years. After reviewing of our records, we discovered that one project was approved and constructed in the Cordelia Fault Spec,'ial Studies Zone. The project is Goodwill Industries, an 18,640 square foot mixed use office, retail, and vocational facility at 180 Grobric Court. A copy of the project geotechnical study, and the original 1984 Alquist-Priolo Fault Study for the Grobric Court Subdivision is attached for your records.

Should you require any further information, please contact Curt Johnston, Assistant Director, at 707-428-7 461.

Sincerely,

CURT JOHNSTON Assistant Direct

•

nQ; HILLIARD V ~sistant Planner

CJ:JRH:jrh

cc: Gene Cortright, Public Works

s:\ .. \al-pri.Jtr

GROBRIC COURT SUBDIVISION

CORDELIA, CALIPORl!TIA

AI.QUIST-PRIOLO STUDY OP CORDELIA PAULT

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•• ENGE() INCORPORATED GEOTECHNICAL & ENVIRONMENTAL CONSULT ANTS

August 14, 1984

Gordon Fisk & P.O. Box 5469 Walnut Creek,

Attention:

subject:

Gentlemen:

Associates

CA 945 96

Gordon Fisk

Grobric Court Subdivision Cordelia, California

AI.QUIST-PRIOLO FAULT STUDY

In Reply Please Refer to:

N4-1992-Bl

As you authorized, we have undertaken a geologic exploration for the subject site. Our study was conducted in compliance with the requirements of the Alquist-Priolo Special Studies Act of 1972. This act requires special geologic studies within designated areas to assess the potential for earthquake fault rupture.

We conclude that there is no active trace of the Cordelia fault beneath the subject site. The site may be developed, from a geologic standpoint, as proposed. However, shallow groundwater conditions necessitate further study of soil and foundation conditions.

If you have any further questions, please do not hesitate to contact our office.

Very truly yours,

ENGEO, Inc.

Mark Peterson

John W. La Violette C.E.G. 1060

Copies: 4 to Client

Reviewed by:

William B. Wigginton

• 2280 Dl.>.MOl'D BLVD. • SUITE 200 • CONCORD, CALIFORNIA 94520-5719 • (415) 687-9700 • FAX (415) 687-0126

)

REPORT

to

GORDON FISK & ASSOCIATES

WALNUT CREEK, CALIFORNIA

ALQOIST-PRIOLO STOOY 011' CORDELIA FAULT

for

GROBRIC COURT SUBDIVISION

CORDELIA, CALIFORNIA

ENGEO PROJECT No. N4-1992-Bl

ADGOST 14, 1984

)

TABLE OP CONTENTS

Page

INTRODUCTION Purpose and Scope . . . . . . • • 1 Methods of Exploration • . • . • • • • • • 1 Site Location and Description. • • • . . • • • • • 2 Geologic Setting • • • • • • • • • • • • • • • • 2

EXPLORATION Seismic Setting . . • • • • • • • • • • • • • . • 3 Nearby Investigations. • • • • • • • • • . • . • 3 Aerial Photograph Interpretation • • • • • • 4 Trench Excavation. • • • • • • • • • • • . • 5 Geologic Reconnaissance. • • • • • • • • 5

CONCLUSIONS. • • . . • • • • • • • • • • • • 6 RECOMMENDATIONS. • . • • • • 7 LIMITATIONS • • • . • • • • • • • • a SELECTED REFERENCES. • • 9

ENGEO INCOKPORATtD 0

)

IHTRODIJC'l'ION

Puroose and Scoce

. The purpose of this study was to determine the potential for surface fault rupture within the subject site or in the site vicinity. This study is in accordance with the Suggested Guidelines for Evaluating

the Hazard of Surface Fault Rupture, Special Publication 42, published by the California Division of Mines & Geology. These guidelines suggest the procedures and report format needed to comply with the Alquist-Priolo Special Studies Zone Act of 1972. This law directed the State Geologist to delineate special study zones for California. Potentially active and active geologic fault traces (Figure 1) are mapped within these zones.

The site is within the Alquist-Priolo zone for the Cordelia fault.

Methods of Exoloration

The methods used in our study included:

ENGEO INCORPOR"-TED

1)

2)

3)

4)

5)

a review of published maps and literature concerning the Cordelia fault zone and geology of the site and its vicinity;

a review of recent geologic explorations near the site;

a review of 1981 stereo black and white photographs;

exploratory trenching totaling 1078 feet; and

preparation of this report detailing the findings of our exploration,

Site Location and Description

The site is located south of the intersection of Highway 680 and Interstate 80, off central Way, in Cordelia, California (Figure lJ. The site has been subdivided into eight parcels which vary from

less than one to l. B acres in size. All parcels are zoned for commercial use. A Pacific Gas and Electric right-of-way crosses· the property.

Geologic Setting

The site is underlain by rocks of Tertiary age, belonging to the Sonoma Volcanic Group (Wagner and Bortugno, 1982>. These rocks are composed of andesitic to basaltic lavas, with some rhylotic lava. Ashflow tuff, locally welded together with bedded agglomerate and t~ff breccia or pumiceous tuff, also occurs, rocks occur in the hill south of the site.

OU tcrops of these

Su::-!icial deposits at the site consist primarily of Quaternary alluvial sediments derived from erosion of the volcanic rocks.

These deposits are interbedded with marsh deposits on the west side of the property and stream channel deposits on the east side.

ENGEO INCORPOKAT!.D

E%PLORAT.IOH

Seismic Setting

The Green Valley fault is the major active fault in the site vicinity.

A main trace of this fault is mapped within approximately 6000 feet to the west of the site (Figure 1 l . The Green Valley fault is

considered active and has been pl:"oposed as a possible northwal:"d continuation of the Concord fault which is known to be active. The State Division of Mines and Geology considers it active within Quaternal:"y time Clast 2 million years) under the provisions of the Alquist-Priolo Act.

The Cordelia fault was first mapped by Helley and Herd Cl977l, as passing through the site. It was mapped in its present location based upon the alignment of suspect topographic features and limited field work. Previous mapping did not recognize the Cordelia fault. The Cordelia fault was added to the Alquist-Priolo Special Study Zone Map as a suspected active fault CCDMG 1983).

Nearby Investigations

A geological investigation on the Mangels Ranch property, north of the site, was completed in March 1978. Approximately 290 feet of trenching across the mapped trace of the Cordelia fault revealed

no active faulting. A seismic refraction survey, performed by Louke and Associates, likewise revealed no indications of faulting. Seismic Traverse No. 1 was 500+ feet in length and located 300+ feet south of the southern Mason Ranch boundary.

ENGEO INCDRPOll:AT£D

)

To the north, Applied Soil Mechanics <July 1978) studied the Anderson Ranch property with respect to hazards posed by the Cordelia fault.

Detailed field mapping of Anderson Ranch, and logging of roadcuts along Rockville Road, lead them to conclude that no active fault traces cross the Anderson Ranch in the mapped location of the

Cordelia fault. Faulting exposed along Rockville Road was determined to have occurred because of diapiric folding and not to be presently active or laterally extensive. An unfaulted, continuous layer of

volcanic rock has been deposited across the fault trace as mapped south of Rockville Road. This indicates that no movement has taken

place since the volcanic layer was deposited 5 to 25 million years ago.

Aerial Photograoh Interpretation

The following stereo black and white aerial photographs were studied as part of a previous investigation <ENGEO, 1978):

Flight Line Year Scale Source

AV-844-15-14 1968 1:30,000 ?acif ic Aerial Surveys AV-844-15-15 1968 1:30,000 u.c. Berkeley AB0-52-41 1937 1:20,000 u.c. Berkeley AB0-52-42 1937 1:20,000 u .c. Berkeley AB0-52-43 1937 1:20,000 u.c. Berkeley AB0-54-44 1937 1:20,000 u .c .. Berkeley

In addition, 1981 Pacific Aerial Surveys photographs <AV-2050-09-12) at a scale of l: 24, COO were analyzed for this study. The photographs were scrutinized for the presence of terrain features

characteristic of fault zones, such as linear discontinuities in rock or soil, offset water courses, linear breaks in slope or tonal lineations.

ENGEO IN(Ott:PORATtl)

scarps, topographic lows,

)

Tonal features consist of small patches of vegetation which appear randomly oriented and sometimes truncated by property boundaries.

No geomorphic features or linear discontinuities were noted which

would indicate faulting on the subject site.

Trench Excavation

Three trenches totaling 1078 feet were excavated across the projec­

tion of the Cordelia fault at the locations shown on Figure 2.

Continuous soil horizons were present in all three trenches as shown

on Figures 3 and 4. No evidence for active faulting was observed.

Perched ground water was observed in trenches l and 2 above impermeable bedrock.

Geologic Reconnaissance

The study site and vicinity was examined for any observable evidence of recent faulting or fault creep. Fences, asphalt and building

structures were checked for cracking or off sets that would indicate active fault creep, No superficial evidence of a fault trace crossing the subject property was found. In a quarry on the south side of the hill, located approximately 2000 feet south of the site a shear zone was observed in Tertiary-age Sonoma Volcanics.

ENGEO IN(091:POllA.T!D

\

CONCLUSIONS

1) The results of our exploratory trenching and field work show

the site to be free of evidence for active faulting. Studies done by others on air photo lineations used by Helley and Herd Cl977l to map a_Cordelia fault north of the site show them to be unrelated to faulting (see Bibliography>.

2 l Secondary seismic hazards pertinent to the proposed development include ground shaking and liquefaction. Ground shaking can

be expected during the life of the structures from the Green Valley fault as well as other active faults in the Bay Area.

3) Trenching revealed a high ground water level and the presence of localized granular soils in the western portion of the site. The liquefaction potential of this area should be further investigated in the soil exploration phase. The liquefaction

potential was not considered a serious concern by others for the adjacent Mangels or Anderson Ranches north of the site,

EN GEO fNCORl'OR.\T!D ©

RBCOMMBNDATIONS

1) We see no need for additional geologic studies at the site • ....-/

2) Because no active fault traces were found to traverse the site, no set-backs are deemed necessary.

3) A detailed soil and foundation investigation should be conducted\ on-site with particular attention to liquefaction potential/ since loose saturated sands were present locally.

4) Trenching has been loosely backfilled. These trenches should be precisely located so that further attention can be given to the effect on planned improvements.

EN GEO INCOKPOR.ATID

LIMITATIONS AND UNIFORMITY OF CONDITIONS

The recorrniendations of this report are based upon the assUU1ption

that the soil conditions do not deviate from those disclosed in

the borings. If any variations or undesirable conditions are

encountered during construction, or if the proposed construction

will differ from that planned at the present time, ENGEO INCOR~

PORATED should be notified so that supplemental recorrniendations

can be given.

This report is issued with the understanding that it is the

responsibility of the owner, or of his representative, to ensure

that the information and reco11111endations contained herein are

called to the attention of the Architect and Engineers for the

project and incorporated into the plans, and that the necessary

steps are taken to see that the Contractors and Subcontractors

carry out such reco11111endations in the field. The conclusions

and recommendations contained herein are professional opinions

derived in accordance with current standards of professional

practice and no warranty is expressed or implied.

SELECTED REFERENCES

Borcherdt, R.D. 1975, Studies for Seismic Zonation of the San Francisco Bay Region, O.S.G.S. Professional Paper 941-A.

Brown, R.P., 1970, Faults that are historically active or that show evidence of geologically young surface displacements, San Francisco Bay region; A progress report, O.S.G.S. MF-331_.

California Division of Mines and Geology, 1983, State of California Special Studies Zones, Cordelia Quadrangle.

Del Davis Associates, Inc., 1977, EIR for Mangels Ranch Planned Development, City of Fairfield, California.

Dooley, R.L., 1973, Geology and land use considerations in the vicinity of the Green Valley fault, Solano County, California: California university, Davis, un­published M.S. thesis.

ENGEO Incorporated, 1977, Soil and Geologic Data for EIR of 1400 acres in Brown's Valley Area, Vacaville, California.

ENGEO Incorporated, 1978, Fault Investigation of Mason Ranch, Fairfield, California.

Frizzell, Brown, 1976, Map Showing Recently Active Breaks along the Green Valley Fault, Napa and Solano Counties, California, O.S.G.S. MF-743.

Geomechanics, 1972, Feasibility Study for Mangels Property, Fairfield, California.

Geomechanics, Inc., 1978, Geologic Investigation for Mangels Ranch, Cordelia, California.

EN GEO INCOR.rOllAT'ED

•

' I

Helley, E.J., Herd, D.G., 1977, Map Showing Faults with Quaternary Displacement, Northeastern San Francisco Bay Region, California, U.S.G.S. MF-881.

Helley, E.J., Herd, D.G., 1977(a), Field Observations and Air Photo Interpretation Map, Scale 1:24000, unpublished.

Jennings, 1975, Fault Map of California, C.D.M.G. Geological Data Map #1.

Larry Seeman Associates, 1978, Preliminary Draft EIR for Hofmann Property, Cordelia, California.

Sedway/Cooke, 1976, Health and Safety Final Draft, County of Solano.

Sims, Fox, Bartow, Helley, 1973, Preliminary Geologic Map of Solano County and Parts of Napa, Contra Costa, Marin and Yolo Counties, California, U.S.G.S. MF-484.

U.S.G.S., 1951, 7.5 Minute Topographic Map Series, Cordelia Quadrangle.

Wagner, D. L., and E. J. Bortugno, 1982, Geologic map of the Santa Rasa Quadrangle: California Division of Mines and Geology, Map No. 2A. Scale : 1:250,000.

ENGEO INCOR'O~AT!D

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S/2) lo :11H1

EN GEO LOG OF TRENCHES # 2 ANO

Grobric Cour1

INCORPORATED Cordelia~ CaU1ornia

#3

l:HG•l'lf£Eltt--ou~rsn SCALE r· • 10• IJ08 N4·1992·81 C:OMliU\. TANT$ ~ T"""' ... '"'-l[;CI DATE AuguSI 1984 INC. ;E..,.ll"T""'SCill:"flllCU

EAST

FIGURE NO.

4

•

• PREPARED FOR: Goodwill Industries

GEOTECHNICAL INVESTIGATION REPORT

PROPOSED GOODWILL INDUSTRIES BUILDINGS

LOTS 4 & S, GROBRIC COURT

CORDELIA, CALIFORNIA

JULY 9, 1990

BCA FILE No. 1984-1

BALBI & CHANG ASSOCIATES

-11 ~ BALBI & CHANG ASSOCIATES ~ .-_ Geole<hnic:il Consnll11nts _ _....._ Constru<tlon M111erlals Tes•ina

July 9, 1990 File No. 1984-1

Mr. Morris R. Wright Goodwill Industries 1301 Thirtieth Avenue Oakland, CA 94601 .

Subject: Geotechnical Investigation Report Lots 4 & 5 Grobric Court Cordelia, California

Dear Mr. Wright:

Balbi & Chang Associates is pleased to present the attached report which describes the results of our geotechnical investigation for the proposed buildings to be constructed at Grobric Court Lots 4 & 5 in Cordelia, California. This report describes the investigation conducted and provides our conclusions and recommendations for preparing site grading, foundation system, concrete slab-on-grade, lateral earth pressure, and asphalt concrete pavement.

We appreciate the opportunity of working with you on this project. If there are any questions concerning the attached report, or if we may be of further service, please contact our office at your convenience.

Very truly yours,

BALBI & CHANG ASSOCIATES

c2£{~ /~ _µg Philip Cc:n;, ;.E. ~ President GE 204

PLC/sc

151 Link Rd~ Cordelia, CA 94!'115 (707) 1164-lOlO Fax: (707) 864-8886

TABLE OF CONTENTS

Letter of Transmittal

I. INTRODUCTION

A. Project Description B. Purpose and Scope of Work c. Authorization

II. INVESTIGATIONS AND FINDINGS

A. Site Description B. Field Investigation and Laboratory Testing c. Subsurface Soil Conditions D. Groundwater Conditions

III. CONCLUSIONS AND RECOMMENDATIONS

A. Discussions and Conclusions B. Recommendations

I. Site Preparation and Grading 2. Excavation and Backfill 3. Foundation System 4. Concrete Slab-on-Grade s. Lateral Earth Pressure 6. Asphalt Concrete Pavement 7. Surface Drainage 8. Seismic Consideration 9. Plan Review and Construction Observation

IV. REPORT Lll\IITATIONS

DIAGRAMS

Plate 1 Plate 2

APPENDIX A

Plate A-1 Plates A-2 -- A-7 Table A-1

Site Vicinity Map Boring Location Map

Log Legend Log of Test Pits Summary of Laboratory Tests

Page

1

1 1 2

2

2 3 3 4

4

4 5

5 7 8 9

10 10 12 12 13

13

GEOTECHNICAL INVESTIGATION REPORT

PROPOSED GOODWILL INDUSTRIES BUILDINGS

LOTS 4 & 5, GROBRIC COURT

CORDELIA, CALIFORNIA

I. INTRODUCTION

This report presents the results of a geotechnical investigation for the proposed Goodwill Industries buildings to be located on Lots 4 & 5 of Grobric Court .in Cordelia, California. A detailed geotechnical investigation for the entire Grobric Court Subdivision had been previously performed by Balbi & Chang Associates in 1984. This report utilize the results of that previous investigation as well as other more up to date information. No additional field work was performed specifically for this investigation.

A. Project Description

It is our understanding that the proposed project will be industrial/warehouse type of development. No definite development scheme was available at the time this report was prepared, however, it is our understanding that there will be either one or two buildings constructed on these lots with a total building space of 27,000 square foot. Detailed structural information was not available either, however, we anticipate the building(s) will be one-story concrete tilt-up building(s) that generally do not exceed 3,000 pounds per linear foot of wall for wall loads and 40 kips per column for column loads.

B. Purpose and Scope of Work

The purpose of this investigation was to determine the feasibility of the proposed development with respect to site soil and geological characteristics and to provide recommendations and opinions concerning the following items:

Page l of 14

July 9, 1990 File No. 198'1.1

• Site preparation and grading; • Foundation system; • Concrete slab-on-grade; • Lateral earth pressures; • Trench excavation and backfill; • Asphalt concrete pavement; • Site. surface drainage; and • Seismic consideration.

.!Atl3l & CHANG ASSOCIATES

The scope of our work consisted of the field exploration of subsurface soils, laboratory testing of soil samples, review of local geology, engineering analysis of collected data, and the preparation of this report.

C. Authorization

Work covered by this report was performed in accordance with our proposal dated May 30, 1990 and the written authorization given by Mr. Morris R. Wright of Goodwill Industries.

II. INVESTIGATIONS AND FINDINGS

A- Site Description

The project site is located at the end of Grobric Court, immediately south of Central Way, in Cordelia, California as shown on the Site Vicinity Map, Plate 1. The site is consisted of two parcels, Lot 4 and Lot 5, and totaling 3.8 acres in plan area. The site

1 is bounded on the north by Lots 3 and 6 of the Grobric Court Subdivision, to the east by the Green Valley Creek, to the south by open field, and to the west by Green Valley School. The topography of the site is relatively flat with a slight downward slope toward the Green Valley Creek. The site is currently vacant and the ground surface was covered with moderate to heavy growth of weeds.

Page 2 of 1.i

July 9, 1990 File No. 1984-1

B. Field Investigation and Laboratory Testing

llALBI & CHA.c'iG ASSOCL\ TES

The subsurface investigation program, which was completed in 1984, consisted of the excavation of six: test pits. The approximate locations of those test pits are shown on the Test Pit Location Map, Plate 2. The test pits were excavated by a Ford 555 tractor mounted backhoe with a 24-inch wide bucket. All test pits were logged by our field engineer, who also obtained representative soil samples for laboratory testing. The soils encountered in test pits are shown on the Test Pit Logs, Plates A-2 through A-7, of Appendix: A. A copy of the Unified Soil Classification System used to identify the site soils is presented on Plate A-1.

Representative soil samples were obtained by pushing 2-inch LD. Modified California Sampler containing thin brass liners into the bottom of test pit with the weight of the backhoe. When the sampler was withdrawn from the borings, the brass liners containing the samples were removed, examined, and sealed to preserve their natural moisture content for laboratory testing. A penetrometer was utilized in the test pit sidewalls to evaluate the in-situ strength of cohesive soils.

Laboratory tests were performed on selected samples obtained from the test borings to evaluate their strength and other physical properties. Tests performed included moisture content, dry unit weight, Atterberg limits, R-Value and unconfined compressive strength. A summary of laboratory test results is presented on Table A-1 of Appendix: A.

All test pits were backfilled upon the completion of field exploration program. The backfill was compacted to the extent possible with the equipment at hand but not to the requirements of structural fill. If structures, concrete flatwork, pavements, utilities, or other improvements are to be located in the vicinity of any of these test pits, the backfill should be removed and recompacted in accordance with the requirements for structural fill contained in the following "Site Preparation and Grading" section of this report. Failure to compact the backfill properly could result in excessive settlements of improvements located over, or immediately adjacent to the test pits.

C. Subsurface Soil Conditions

Available geologic literatures indicate the soils underlying the project site are mainly alluvium of the Quaternary period (the most recent 3 million years.) A generalized view of site soil conditions is presented below. Detailed descriptions of subsurface soils encountered at each test boring are presented on the Boring Logs in Appendix A.

Page 3 of 14

July 9, 1990 File No. 19~-\

!!ALB! & CRA.'IG ASSOCL\ TES

A generalized profile across the site would consist of a surface and near surface layer of soft to medium stiff, moderate to highly plastic silty clay, that extends to depths on the order of 4 to 5 feet below existing grade. This clayey soil is considered to have a moderate to high potential for volume change with fluctuations in moisture content.

Underlying the clay stratum is several feet of loose to medium dense, medium to low plastic, clayey silty sand that grades to a fine grained silty sand. The silty fine sand stratum has interbedded silt layers and extends to the ma'<imum explored depth. This silty sand is generally loose, wet, and very low to non-plastic.

D. Groundwater Conditions

Free groundwater was observed in the test pits at the time of our field exploration. Groundwater levels measured immediately after excavation was completed are about 7 to 10 feet below the existing ground surface. Water level in the site area is generally on the order of 5 feet below the ground surface and may raise to less than 2 feet below the ground surface during winter months.

This relatively high groundwater table is not expected to have significant impact on the proposed construction. However, it may limit the selection of foundation types during planning stages and may pose some constrains on the construction schedule. Ground­water conditions at the site are anticipated to fluctuate in the future due to factors such as seasonal rainfall, groundwater pumping and recharging, seepage conditions and construction activities. However, the influence of these factors could not be detennined at the time of our investigation.

III. CONCLUSIONS AND RECOMl\IENDATIONS

A- Discussions and Conclusions

Based upon the results of our investigation, it is our opinion that the site may be developed for the proposed structure from a geotechnical engineering standpoint. The major geotechnical engineering concerns for this site are the expansive clays, weak near surface soils, and the high groundwater table.

Page 4 of 14

July 9. 1990 File No. 1984-1

dALBl & CHANG ASSOCL\TES

The near surface site soils are moderate to highly expansive. Such soils will undergo volume change with variations in moisture content. Significant distress could result to foundations and concrete slabs if present in the final subgrade elevation. It is our opinion that replacing part of the site soil with non-expansive fill as well as careful moisture conditioning and compaction control will be necessary to reduce the impact to future structures.

The soft and loose soils at the existing site grade can only attain low bearing capacity. Excessive settlements may result if spread footing foundation is used. However, the high groundwater table and the lack of suitable support stratum within a reasonable depth make pier and grade beam foundation infeasible. Consider the type of proposed project, it is our opinion that the most economical solution is to suppon the proposed structures on spread footing foundations founded in subgrades reconstructed from non-expansive fill.

Detailed recommendations for foundation system and other geotechnical engineering related items are presented in the following sections of this report.

B. Recommendations

1. Site Preparation and Grading

Grading plans for the project are not available at the time this report was prepared. However, because the site grades are slightly lower than the adjacent street grades and building pads should be above the flood plain, we anticipate two to three feet of fill may be required for proper site development.

In addition to site drainage consideration, non-expansive engineered fill is also required to support the proposed structures because of the expansive site soils. We recommend to combine these two fill requirements and construct an engineered fill building pad in accordance with the following recommendations for site preparation and grading.

a. All areas to be graded should be stripped of vegetation and organic material. It is estimated that this will require the removal of 2 to 6 inches of near surface material. This material can be stockpiled and reused for landscaping purposes; however, it should not be incorporated into structural fills.

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.. July 9, 1990 File No. 198+.!

.ALB! & CHANG ASSOCL\ TES

b. The non-expansive engineered fill for building pad should extend at least 2 feet below the bottom of footing and one foot below the floor supporting material of concrete slab-on-grade floors. The fill should also extend 3 feet beyond the limits of the foundation. Dependent on existing site grades, some over-excavation of the stripped areas may be required to accommodate this engineered fill. The on-site soil generated from over-excavation should not be incorporated into structural fills because they are quite expansive.

c. After site preparation, all areas to receive fill and at grade should then be scarified to a minimum depth of 12 inches and recompacted to a relative density between 88 and 92 percent of the maximum dry density as determined by ASTM 01557-78 Standard Test Method. The moisture content of the recompacted soil should be at 3 to 5 percent above the optimum moisture as determined by ASTM 01557-78.

d. Near surface on-site soils generated from excavation should not be used as structural fill material because of the expansion potential, however, they may be used in landscaping areas. Structural fill should consist of non-expansive on-site or imported material. Imported material, if needed, should be approved by the soils engineer prior to being brought to the site. All imported materials should be non-expansive, free of perishable organic materials, with a Plasticity Index (P.I.) of 12 or Jess and a Liquid Limit (LL) of 30 or less, and meet the partic:le size requirements as listed in Table 1 below.

TABLE 1

IMPORTED MATERIAL SIZE REQUIREMENTS

Sieve Slze

6inches 3inches No. 200

Percent Passing

100

95 -100

5 - 25

e. Aii structural fill material, on-site and imported, should be compacted in lifts no greater than eight inches in thickness by mechanical means. Compaction by jetting or flooding should not be allowed except specifically instructed by the geotechnical engineer. Structural fill should be compacted to a minimum relative compaction of 90 percent of the maximum dry density, at 1 to 3 percent above the optimum

Page 6 of 14

July 9, 1990 File No. 198-1-1

BALBI & CHA..'!G ASSOCL\ TES

moisture content as determined by ASTM 01557-78. Non-structural fill, such as those for the landscaping areas, may be compacted to 85 percent, however, excessive settlement may resulted from such low compaction effort.

f. The top 12 inches of subgrade soils for all paved areas should be properly compacted to provide adequate pavement support. For on-site soil subgrade, the compaction requirement should be 92 to 94 percent of maximum dry density at 2 to 4 percent over the optimum as determined by ASTM 01557-78. For imported fill subgrade, the minimum compaction should be 95 percent and the moisture content should be at 1 to 3 percent over the optimum moisture content.

g. Compaction specification recommended above is not the only criteria for proper fill placement. Other than the degree of relative compaction and the percentage of water content, the stability of the fill material is also an important factor to the performance of the fill. A fill can be unstable even if the fill material meets required compaction specifications. Therefore, a fill should not be considered compacted, regardless of the degree of relative compaction, if the material is unstable (such as "pumping") or if future instability is suspected.

h. Finish grading for building pad shoulo consist of rolling the surface to a dense condition for uniform slab support. The surface should be sloped away from the pad so that drainage will be directed away from foundations.

1. All site preparation and fill placement should be observed by a representative of the geotechnical engineer. It is important that during the stripping and scarification process a representative of the geotechnical engineer be present to observe whether any undesirable material is encountered in the construction area.

2. Trench Excavation and Backfill

Excavation for footings and utility trenches can be readily made with either a backhoe or trencher in either native soil or compacted fill. We expect the walls of the footing trenches to stand vertically without significant sloughing in the native soil or compacted fill material provided it contains sufficient cohesive fines. Where trenches are extended deeper than five feet, the excavation may become unstable and should be sloped back or shored to protect personnel and to provide stability. Walls of deep trench should be inspected to verify their stability prior to personnel entering the trenches.

Page 7 of 14

July 9, 1990 File No. 1984-1

BALBI & CHA..'!G ASSOCL\TES

Backfills for trenches or other excavations within pavement areas and beneath slabs should be compacted mechanically in 6 to 8 inches lifts to assure adequate subgrade support. Jetting or flooding should not be permitted. We recommend a minimum relative compaction of 90 percent of maximum dry density as determined by ASTM 01557-78 for all backfills except the landscaping areas. The uppermost 12 inches within the pavement area should be compacted to a minimum of 95 percent. The moisture content of compacted backfill soils should be at or slightly over the optimum moisture content. Poor compaction in utility trench backfill may cause excessive settlements resulting in damage to the pavement structural section.

3. Foundation System

The proposed structures may be supported by conventional spread footings founded in non-expansive engineered fill. The engineered fill should extend at least 2 feet below the bottom of the footing and 3 feet beyond the limits of the foundation. The minimum footing width should be 12 inches and the minimum embedment depth should be 18 inches. Footing embedment depth is measured from the lowest adjacent soil subgrade to the bottom of footing.

Footings constructed in accordance with the recommendations stated above may be designed for an allowable soil bearing pressure not exceeding 2,000 pounds per square foot for dead plus live loads. This bearing pressure may be increased by one-third for transient loads, including seismic or wind effects. The weight of foundation concrete extending below grade may be disregarded in footing sizing computation. All footings should be properly reinforced as recommended by the structural engineer.

Soils exposed in footing excavations should not be allowed to dry prior to the construction of footings. If shrinkage cracks should appear in footing excavations, the soils should be thoroughly moistened to close all cracks prior to the placement of footing concrete. Openings for utilities within the perimeter waJI footings should be sealed to prevent moisture migration.

All footing excavations should be observed by a representative of the geotechnical engineer to verify the competence of the bearing material. If soft or undesirable material is encountered within the footing excavation, the area should be over-excavated and replaced with either engineered fill or concrete.

Page 8 of 14

.. July 9, 1990 File No. 1984- l

JlALBl & CIL\."G ASSOC LA TES

We estimate that post-construction settlement of the structures will be less than one inch. Differential settlements for foundations proportioned for the bearing values recommended above are expected to be less than half of an inch. If the structural design requires unusual foundation configurations or imposes loads greater than those anticipated for the proposed structures, our finn should be contacted for possible modification to these recommendations.

4. Concrete Slab-on-Grade Floor

Because of the high expansion potential of on-site soils, concrete slab-on-grade floors should be placed on at least one foot of non-expansive engineered fill. This one-foot engineered fill may be part of the previously described engineered fill pad and is in addition to the slab supporting material described below.

Concrete slabs should be properly reinforced to control shrinkage cracks. Structural details of the concrete slab-on-grade floor, such as the floor thickness and reinforcement, location and pattern of construction joints, should be determined by the architect I engineer of the project. However, we recommend using deformed reinforcing bars instead of welded wire mesh as the slab reinforcement unless it can be guaranteed that wire mesh will remain in the center of the slab after construction as it was designed to.

Concrete slab-on-grade should be constructed on at least four inches of clean coarse sand, gravel or crushed rock for unifonn support. Material used to support the slabs should be compacted to at least 90 percent of maximum dry density and at or slightly above the optimum moisture content as determined by ASTM 01557-78 Standard Test Method. We recommend that the slab supporting material be placed as soon as the subgrade soil

. is compacted to prevent drying of the soil. If the subgrade soil is allowed to dry out prior to the construction of concrete slabs-on-grade, the subgrade soils should be pre-saturated by spraying or flooding and the process verified by the geotechnica\ engineer.

For slab-on-grade with moisture sensitive surfacing, such as carpet or vinyl tile, we recommend the slab supporting material be consisted of free draining granular material graded such that 100% will pass l·inch sieve and none will pass No. 4 sieve. Also recommended is an impermeable membrane placed over the rock to prevent migration o( moisture vapor through the concrete slabs. In order to promote a more unifonn curing of the slab and to provide protection of the vapor membrane, it is advisable that one to two inches of moist fine sand be placed on top of the membrane prior to placement of the slab concrete.

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July 9, 1990 File No. 1984-1

5. Lateral Earth Pressure

BALBI & CHA..'IG ASSOCL\ TES

Lateral earth pressures will be imposed on all below-ground structures, including walls and foundations. The recommended lateral earth pressure values for horizontal and backfill are presented in Table 2 on the next page as equivalent fluid densities.

TABLE 2

LATERAL EARTH PRESSURES

Earth Pressure

Active At Rest Passive

Equivalent Fluid Density

45 pcf 65 pcf

300 pcf

The above recommended lateral earth pressures are ultimate values and appropriate factor of safety should be applied by the design engineer. Also, these values are for on­site soils only and do not include any allowance for hydrostatic pressures. Coefficient of sliding friction of 0.25 is recommended for use in design between underside of concrete structure and native soil.

Where backfill is placed against retaining structures, it is recommended that granular materials be used in the zone immediately adjacent the structure. This is to reduce the probability of hydrostatic pressure build-up from groundwater seepage and infiltration of surface water. The width of this granular backfill zone should be equal to or greater than one·half the embedment depth. Backfills should be compacted to between 85 and 90 percent of ma-:imum dry density and at or near optimum moisture content as determined by ASTM Dl557-78 Standard Test Method. Over-compaction may induce lateral earth pressures greater than those recommended above, therefore, should be avoided.

6. Asphalt Concrete Pavement

Asphalt pavements for access roads and parking spaces had been planned for the development. Anticipated traffic loads wt11 most likely consist of light passenger vehicles

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July 9, 1990 File No. 1984-1

BALBI & CHANG ASSOCL\ TES

and occasional delivery trucks. Heavy truck traffic is not anticipated. Based upon this use of pavement and a 10-year design life, we recommend a Traffic Index (TI) of 6.0 for access roads, travel Janes, and loading areas and a TI of 4.0 for parking stalls for the design of asphalt pavement section. Laboratory testing on sample from the near surface site soil had resulted a Resistance Value (R-value) of 5. Based on observed soil type variations during field exploration, we recommend a design R-value of 5 be utilized in pavement design.

Recommended asphalt pavement structural section designs based on the above described Traffic Indices and soil R-value are presented in Table 3 below as two alternates. Alternate I consists of a pavement section of asphalt concrete over aggregate base and aggregate subbase. Alternate II is an equivalent pavement section consisting of asphalt concrete over aggregate base only.

TABLE 3

ASPHALT CONCRETE PAVEMENT SECTION

Alternate I Tl:6.0

Tl=4.0

Alternate II

Tl=6.0 Tl,,,,4.0

Type B Asphalt Concrete

3.o· 2.5"

3.o· 2.5"

Class 2 Aggregate Base,R:::78+

1.0· 4.0"

15.0"

9.0"

Class 2 Aggregate Subbase,R=SO+

9.0"

6.0"

The above recommended sections are considered adequate provided that the following conditions are met:

a. All trench excavation has been properly backfilled and compacted as previously specified in the "Trench Excavation and Backfill" section of this report.

b. All pavement subgrade soils have been prepared in accordance with recommendations contained in the "Site Preparation and Grading" section of this report and are stable and non-pumping at the time the base rock is placed.

Page 11 of 14

July 9, 1990 File No. 198-1-1

JIALBI & CUA.'IG ASSOCL\TES

c. An adequate drainage system is provided to prevent both surface water and subsurface seepage from saturating subgrade soils and aggregate base. This is especially important where pavement abuts landscaped areas.

d. The aggregate base material is compacted to 95 percent of the relative compaction and meet the requirements of Caltrans standard Specifications for Oass 2 Aggregate Base. Subbase material, if used, is also compacted to 95 percent and meet the requirements of Class 2 Aggregate Subbase.

7. Surface Drainage

Final elevations at the site should be planned so that drainage is directed away from all foundations, and final building pad elevation should be at least one foot above 100-year flood plane. Paved areas should be sloped and drainage gradients maintained to carry all surface water off the site.

Continuous roof gutters are recommended for all proposed structures. All down-spouts should be connected to non-perforated drain pipes or other appropriate drainage structures that can carry collected rain water away from the building foundations. Ponding of water or concentrated seepage should not be permitted under the building or adjacent to the foundations system and paved areas.

8. Seismic Consideration

Based on the review of available geologic literatures, the project site is located within an Alquist-Priolo Special Study Zone established for the Cordelia fault. In order to detennine the potential of surface fault rupture within the subject site or in the site vicinity for the purpose of planning and construction, a special study in accordance with the guidelines set forth by the Alquist-Priolo Special Studies Zone Act of 1972 must be conducted.

Even though there was no special studies conducted specifically for this site. There was a special study performed for the entire Grobric Court Subdivision, which encompasses the project site, by ENGEO in 1984. The ENGEO report concluded there was no evidence of active faulting within the site area.

Page 12 of 14

July 9, 1990 File No. 198-1-1

BALBI & CHANG ASSOCL\ TES

Even though no active faulting was found within the project site, there are a couple of active faults in the vicinity of the site. The Green Valley fault is located about 2 miles west of the site while the Midland fault is approximately 10 miles east from the site. The primary seismic hazard of this site is strong ground shaking during earthquakes generated by these and other more distant active fault zones in the greater Bay Area region.

It is our opinion that the proposed structure could be subjected to strong ground shaking during its useful life. The effects· of ground shaking on the proposed structures may be mitigated by design and construction detailing in accordance with applicable seismic provisions of seismic zone "4" and site coefficient of "S3" as specified in the 1988 edition of Uniform Building Code.

9. Plan Review and Construction Observation

Continued coordination between the design engineer and our firm is recommended to assure that the design is compatible with the soils conditions defined by this investigation. All final designs of foundation system, retaining walls, and grading plans should be reviewed and/or approved by our firm or a qualified geotechnical engineer prior to construction.

We also recommend that our firm be retained to provide construction monitoring and testing services during construction phase. The purpose of construction observation is to verify predicted subsurface conditions, to observe compliance with the design concepts, specifications and recommendations, and to allow design changes if necessary.

IV. REPORT LIMITATIONS

This report has been prepared for the exclusive use of Goodwill Industries and their consultants for specific application to the proposed project. The use of this report, its contents, or any part by a party, or its agents, other than the one for whom this report is prepared, is herewith disallowed. The use of any information contained in this report for purposes other than those explicitly stated in the report is at the user's own risk.

Page 13 of 14

July 9, 1990 File No. 1984-1

JALBI & CHA."IG ASSOCL\ TES

The services provided under this contract as descnbed in this report include professional opinions and judgments based on the data collected. These services have been performed according to generally accepted soil and foundation engineering practices. The recommendations contained in this report are based on information obtained from:

1. Six test pits; 2. The observations of our field engineer; 3. The results of laboratory tests; and 4. Data from existing literatures.

The test pit logs do not provide a warranty as to the conditions that may exist at the entire site. The nature and extent of subsurface soil variations may not become evident until construction occurs. If subsurface conditions encountered in the field during construction are different from those described in this report, our firm should be contacted immediately to provide any necessary revisions to these recommendations. In addition, if the scope of the proposed construction changes from that assumed in the preparation of this report, our firm should be notified and a review of the recommendations be performed.

The validity of the recommendations contained in this report depends upon an adequate testing and monitoring program during the construction phase. Unless the construction monitoring and testing program is provided by or coordinated with our firm, Balbi & Chang Associates will not be held responsible for compliance with design recommendations presented in this report and other addendum submitted as part of this report.

Respectfully submitted,

BALBI & CHANG ASSOCL4 TES

Page 14 or 14

< \. •, .~i -~- I •'.-'

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Base Map: Cordel" ia Q uadranqel Sh . . . s. eet, O S G - -2000· Scale• 1 •

LOTS 4 & 5, GROBRIC CO URT

sultanu / Material• T ntlnQ

BALBI & CHAN GeolecMlcal Con G ASSQCIA TES

SITE VICINITY MAP

1984-1

PREPAREO av

PROJECT NO

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LEGEND

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APPENDIX

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UNIFIED SOIL CLASSIFICATION SYSTEM

IU.J'OI GIQtlP D£SCl[PitOlf woo GICIUP D.ESClIPTIOlll DlvtStON SYMBQL DlVtsio11 SY1UJ1Qt.

•• ~•ll~qr•4•d ;r&v•l• t:lf' 11ra•tl 1U1A4 ,. lnar;an1c •ilta ind ~'*fY C1n•

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satid •i:,;t11-t1n, littlit cir na fiMu1. li'lAVtt.t.Y C:t.A'fS <• I~~t~•Q1C ~lay$ ~f la• co ••div•

•• Silty ;r1v•l1, ~ravit1·~•A~-,11t •la•ticity ;r•T•lly clays, aandy SOit.S ili:lt'll'"~~. Lt.iSO Cl4y:.. ~ultY eh1ys, l•aa cl1y1.

CO.l.l!.C oc Clayity ;rav•ls. 1t•••l·~•Ad~~tay TI.XE •• Or;anic 1ilta an4 arqanic stltT 11111.:t~[•:I. Clays ol low plaati~1ty

C:RAtM1:D 'AAtlllD .. V•ll·vr•d.d aanda ar 11rav•lly " tnaroa~~~ stlt~. •i~~~•QQS Ot .sou.s SAIUI •anda. lilt~~ ot dQ ft4••· IOtI.S SU.TS diatQmte.oua tini!I ~andy or 1ilty

SQtla. •laatic 1ilta • ... .. Poot1Y·w~•d~d •aada or ;rav~llv ... sand, l~ttl• or ~Q (1nt•. Cl [aor1aaic ~lay1 o( biqb plaatici,y.

$.UDY l;T,.ll$. l•t -cl•y'I.

SOIU .. Silty sand•. san4-~ilt Ai~tur•~- t.t.>~0 •• Ot1anic cl&ya of 2~diu• to lti;h pla~t.i~tfy, ocq•ti~(: .t.tlt:s

SC Cl•Y•Y 1anda, •.uwl.~~lay •i~tur~•. 11.J:GtU.'t " Pi!11.t 4nd O(bier b.tQ~lY oC';ani~ ORt;AIUC son.s 11i,il1

0 ST>HDlRO PENETRATION SPLJT SPOOH s1xPt.i

[!] SHELBY TU8t SAMPLE

~ KOO!F!ED PORTEK SlJIPLl ll.S•io. l.D,)

I KOD!f!ED CALIFORNIA SlJIPLE 12.0·in. !.D.)

:'.!'. VATER LEVtL OBSERVED IN BORING

NR NO KECOVERY

NFWE HO FREE •A~ER ENCOUHTEREO

Pp POCXET P!'.HETROMETER I hold!

NOTE: THE LIHU stPAUTING STRATA OH THE I.O<;S REPIEStllT APPROllKATE BOUllOAR!ES ONLY. THE ACTUAL Tll.IJIS!TlOH KY BE GRADUAL. HO VARR.IJITY IS PROVIDED AS TO THE CONTINUITY OF SOIL STRATA BETVtEN BORINGS. LOGS REPRESENT THE SOIL SECTION OBSERVED AT THE 80KlHG LOCATION OH THE DATE or DRILLING ONLY.

LOTS 4 Ii s. GROBRIC COCJRT LOG LEGEND

BALBI & CHA NC ASSOCIATES PROJECT NO. 1984-1 OATE 07/06/90

Geot•oftnl<;al Coneultanta I M•t•rlala THtlng PREPAREO BY LC Pl.ATE A-1

.. r---------------------

" " ~' --"' " c

2-

102.0 21.3

4-

6-

a-

10-.

12-

14-

16

.

.

Date Excavated: 12/12/84

LOTS 4 & S, GnOBRIC COIJl{T

DlSC!il:IPl'IO."il

..... ----2-I I

CU'i -

cyOl silty, moderate to highly expan- -­sive, dark brown, very moist, stiff,

.---4-I ._.. ....

6-I I

10-I

SM

SAND - fine to medium grained, very silty very clayey, brown, moiBt, loose, ·

L..-L'TIN'D - fine grained, very silty, dark SM blue gray, saturated, loose to medium dense-

Test Pit terminated at 15 feet.

Groundwater seepage observed at 13~ feet during excavating .

No caving of trench sidewalls noted •

LOG OF TEST PIT NO. TP-1

BALBI & CHANG ASSOCIATES PROJl!CT NO. 1984-1 DATE 07/06/90

PRE;PARl!D BY LC PLAT!! A-2

" " ... " ;;; 0

Ory 0t"tt~t¥ Conlcnl .'-toiUur• I

it>llt' '> V<CS OESCR11'110N o--l...~:__~...!....~,..,....~.i.-~~'--,..,....,..,....t--~t--~~--~~.....,~~~--,~~~~~,..,....--4

Slaw/ FL

2-

4-

6-

s_

10-

12-

, 4-

16

-

-

Date Excavated: 12/12/84

LOTS 4 & 5, GROBRIC COOR~

SM SAND - fine to medium grained, very silty _1- _ slightly clayey, dark brown,

L...-..- saturatedt looset

CL CLAY - silty, moderately plastic, brown, very moist, stiff, _ ...... _

........

SM

SAND - fine to medium grained, silty, slightly clayey, brown, very moist, loose to medium dense,

·-'-- -~-

SM

SAND - fine grained, very silty, blue gray, very moist. to saturated, loose to medium dense,

Test Pit terminated at 14 feet •

Approximately 4" of standing surface water at this excavation site. No soil sa111pling possible.

Slight caving of trench sidewalls during excavation.

-

-

LOG OF TEST PIT NO. TP-2

BALBI & CHANG ASSOCIATES PAOJecT NO. DAT&: 07/06/90 PREPARED SY LC PLATE

... " ... " ;; :::

."-'oi11ur11

Or"J' O~iit&tfl' Con1."1 lb/it' " u•c•

o-.l-_.:.:..::....~1--_;_~-+-~~4--~...,....J._:_-+-~~~--~-:---:-:~-:-~,..---:---:--:--~-; CLAY - 3ilty, highly plastic, dark brown,

OfSCRIP'TIC)N

2-

96.0 25.5 2-I

4-

4-I

6-6-I

8-

1 0-.

10-I 1 2-

1 4-

16-

-

Date Bxoavated: 12/12/84

LOT 4 & 5, GR08RIC COURT

uery moist to saturated, medium C!i stiff,

........ -_.... SANO - fine to medium grained, uery silty

SM

_ .... _

slightly clayey, brown, vary moist, loose to medium dense,

grades more clayey,

i...-,.... SAND -

SM

fine to medium grained, very silty, blue gray, very moist to saturated, loose to medium dense

Test Pit terminated at ·13 feet •

No free groundwater observed during excavation.

No caving of trench sidewalls noted.

LOG OF TEST PIT NO. TP-3

BALBI & CHANG ASSOCIATES PROJECT NO. 1984-1 DAT! 07/06/90

PREPARED BY LC PLATE A-4

" " ... c

fr 0

L.

.1.AoiU1,1r..-Cry Otrn~lt Conlent llowl 5.i.mpllf'

··' ' fl u U5CS OlSCRIPTION 0 _1 _ _::~:':w __ _;.~ __ :.._ __ ~1--.:..::..·--~~~~::_-r-J~:.:.:.~~"1'\""..,...~-;;:;:-;::;:;--;;;;;rr;;;:;;-;;r;-;-;:;;;;;:i--:--~~-gIItvi

Jo SAND - nne co meaium grain"'", very silty SM dark brown, saturated, loose .---... - CLA'f - siley, highly plastic:, dark brown,

very moist, medium stiff, 2-

2-I C-1 95.0 26.9

4- .---'- ..... SAND - fine to medium grained, very

4-I silty, clayey, brown, moist, loose

6- SM medium densei

6-I

a-grades light brown, less clayey,

, o-10-I

~"""­..... ~ SAND - fine to medium grained, very

12-

14-

16·

-

-

Date Excavated: 12/12/84

LOT 4 ~ S. GROBRIC COURT

BALBI & CHANG ASSOCIATES GeotecMlcal Conoulunu /Materiel• Teatlng

silty, blue gray, very moist, SM loose, medium dense,

grades slightly silty

Test Pit terminated at 14 feet •

No free groundwater observed during excavation.

No caving of trench sidewalls noted.

LOG OF TEST PIT NO. TP-4

PROJECT NO. 1984_1 DATE 07106/90 PREPARED BY PLATE A-S

... .. ... -c. .. c::

I)" D•n-Nty Conl•"' -~oi11urtr I

lblrr-1 ' uses O~SCA:IP'TION O-r-~~~-;--~~~+-~~t--~-.-i--~+-~~~~~~~~~~~~~~~~--1

SM SAND - fine to medium grained, very silty

2

87.0 34.$

4-

4-I

6-

6-I

8-

10-

10-I

12-

14·

16-

-

-

Date ExcaYated: 12/12/84

LOTS 4 l S, Grobric Court

.-.... _ slightly clayey, dark brown, ,__. saturated, loose,

CLAY - silty, highly plastic, dark brown, very moist, medium stiff,

.~--/

I:--- SAND - fine to medium grained, very silty slightly clayey, light brown, very moist to saturated, loose to

SM

medium dense,

grades slightly silty fine sand

Test Pit terminated at 14 feet.

Groundwater seepage at 10~ feat during excavation .

No caving of sidewalls noted,

-

LOG OF TEST PIT NO. TP-5

BALBI & CHANG ASSOCIATES PROJt:CT NO. 1984-1 OJ, Tl! 07 /06/90

ClleoteoMlo•I Cona .. 11an11 / Meterlala Testing Pflt:PAAED BY LC PL4Ti A-6

2-

6-

8-

1 0-

1 2-

14 <; " ... c

e. .. 0

1 OS. 0 21 • 6 4-I

10-I

Date Excavated: 12'12'84

LOTS 4 ' 5, GROBRIC COCRT

CGAY - silty, sandy, highly plastic, Qi dark brown, saturated to very

moist, soft to medium stiff,

-~'-­'"'" .....

SM

SAND - fine to medium grained, very silty, slightly clayey, light brown, very mcist, loose to medium dense,

Test Pit terminated at 11~ feet.

No free groundwater observed during excavai:ion.

No caving of trench sidewalls noted.

LOG OF TEST PIT NO. TP-6

BALBI & CHANG ASSOCIATES PAOJl!CT NO. 1984-1 DATI! _____ ·--,.,,

Geotechnlcal con•ult•nt• I Mater•••• Testing PREP AA!!D IY Pl.ATE A-7

I ,

•

I

July 9, 1990 File No. 19~-l

Bori'ng Nl>lll>er

TP·1

TP•3

TP-4

TP•5

TP·6

Bulk

*TB-1 "TB· 1 *TB-4 •ra·6 •ra-10 *T3•11

BALBI & CIIANG ASSOCL\ TES

TABLE A·1

SUMMARY OF LABORATORY TESTS

SOn'l>le Dry Unit "'ois.t1..1re Unconfl"ed Atterberg A-Value Depth i.l•ight Cont~t coq:iress f ve Li191i ts (ft) (pc:f) co Str~th L.L. P.!.

............... ----- ------+- ............ ..................... ...... ··--2.0 - 2.5 102.Q 21.3

2.0 . 2.5 96.0 25.5

2.0 • 2.5 95.0 26.9

2.0 . 2.5 87.0 34.5

s.o • 5.5 105.Q 21.6

5

2.0 - 2.5 48 34 11. 0 . 11.5 95.0 24.9 0. 7 tsf 2.0 . 2.5 108.0 15,4 3.6 Uf 2.0 - 2.5 55 l7 6.0 - 6.S 93.0 25.6 1.2 tsf 6.0 - 6.5 102.0 21.3 1.4 tsf ~ 29

*Mot•: D•ta from other borings in the vf cinity of the project site.