HomeMy WebLinkAboutUpdated Geotech Study (Aug.19,1996)
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E GEN C . . Soli Englneefing. Testing. Construction Materials Testing .lobofotOryTestIng.
n orpo ra t1 on . Environmental SOe Assessments. Hazardous Mote",," SOe Cleanup.
Environmental and Geotechnical Engineering Network Corporation . Special Inspections . Geology. Engineenng Geology .
UPDATED GEOTECHNICAL I GEOLOGICAL
ENGINEERING STUDY
Proposed Expansion of Existing Business Center
Parcels 1 through 10 of Parcel Map 24085
Diaz Road, Temecula
Riverside County, California
Project Number: T1075-G8
August 19, 1996
Prepared for:
Westside City Associates I, LLC
41975 Winchester Road
Temecula, California 92590
Los Angeles OffIce
Post Office Box 1497
lancaster, CA 93534
(805) 940-1200 I Fax: 940-1202
Orange Counly ONice
2615 Orange Avenue
Santa Ana. CA 92707
(714) 546-40511 Fax: 546-4052
Corporate Office
41607 Enterprise Circle North, Suite 1 . Temecula . California 92590 . (909) 676.3095 . Fax: (909) 676.3294
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Wests ide City Associates I, LLC
Project No. T1075-GS
TABLE OF CONTENTS
Section Number and Title
PaQe
1.0 EXECUTIVE SUMMARY ...................................................................................................2
2.0 INTRODUCTION ............................................................................. .... ..................... ..........2
2.1 Authorization
2.2 Scope of Study
2.3 Previous Site Studies.............. ...................................... .......................................33
3.0 PROPOSED DEVELOPMENT I PROJECT DESCRIPTION.............................................3
4.0 SITE DESCRiPTION......................................................... ........ .........................................4
4.1 Location
4.2 Legal Description
4.3 Topography
4.4 Vegetation
4.5 Structures
5.0 FIELD STUDY ..... ................................. ............................................................................4
6.0 LABORATORY TESTING ...................................... ............................. .................... ..........5
6.1 General
6.2 Classification
6.3 In-Situ Moisture Content and Density Test
6.4 Consolidation Test
6.5 Maximum Dry Density I Optimum Moisture Content Relationship Test
6.6 Direct Shear Test
6.7 Expansion Test
6.8 Particle Size Analysis Test
7.0 SITE CON DITIONS ..... .......................................................................................................6
7.1 Geologic Setting
7.2 Faulting
7.3 Earth Materials ................... ............... .......... ..................................................... ....11
7.3.1 Artificial Fill (At)
7.3.2 Alluvium (Qal)
7.4 Groundwater and Liquefaction
8.0 CONCLUSIONS AND RECOMMENDATIONS .........................0.......................................9
8.1 General
8.2 Earthwork Recommendations
8.2.1 General
8.2.2 Clearing
8.2.3 Excavation Characteristics
8.2.4 Suitability of On-Site Materials as Fill
8.2.5 Removal and Recompaction ..................................................................10
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EnGEN Corporation
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Wests ide City Associates I, LLC
Proiect No. T1075-GS
TABLE OF CONTENTS (Con!.)
Section Number and Title
PaQe
8.2.6 Fill Placement Requirements
8.2.7 Compaction Equipment
8.2.8 Shrinkage and Subsidence
8.2.9 Subdrains
8.2.10 Observation and Testing
8.2.11 Keyways
8.2.12 Benching
8.2.13 Fill Slopes
8.2.14 Cut Slopes
8.2.15 Soil Expansion Potential
8.3 Seismic Design Recommendations.......... ............................................................13
8.3.1 Design Fault Zone
8.3.2 Ground Accelerations
8.3.3 Design Parameters
8.4 Foundation Design Recommendations ................................................................14
8.4.1 General
8.4.2 Foundation Size
8.4.3 Depth of Embedment
8.4.4 Bearing Capacity
8.4.5 Settlement
8.4.6 Lateral Capacity
8.5 Slab-on-Grade Recommendations...................................................................... .16
8.5.1 Interior Slabs
8.5.2 Exterior Slabs
8.6 Pavement Design Recommendations ..................................................................17
8.7 Utility Trench Recommendations
8.8 Finish Lot Drainage Recommendations
8.9 Planter Recommendations
8.10 Temporary Construction Excavation Recommendations
9.0 PLAN REVI EW .................................. ..... ........................................................................ .21
10.0 PRE-BID CON FERENCE............................................................................................... .22
11.0 PRE-GRADI NG CONFERENCE....... .............................................................................. .22
12.0 CONSTRUCTION OBSERVATIONS AND TESTING .....................................................22
13.0 CLOSURE
................................................................................................................23
APPENDIX:
TECHNICAL REFERENCES
EXPLORATORY BORING LOG SUMMARIES
LABORATORY TEST RESULTS
DRAWINGS
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E GEN C . . Soli Engineering. Testing. Construction Materials Testing. laboratory Testing.
n 0 rporatl on . En~ronmental Site Assessments. Hazardous Motenals Site Cleanup.
Environmental and Geotechnical Engineering Network Corporation . Speciallnspectlons . Geology. EnglneeOng Gedogy .
August 19,1996
Westside City Associates I, LLC
41975 Winchester Road
Temecula, California 92590
(909) 693-1430 I FAX (909) 693-1429
Attention:
Mr. Max Harrison
Regarding:
UPDATED GEOTECHNICAL I GEOLOGICAL ENGINEERING STUDY
Proposed Expansion of the Existing Business Center
Diaz Road, City ofTemecula
Riverside County, California
Project Number: T1075-GS
References: A.
Preliminary Grading Plan, by Hector Correa, dated July 10, 1996, no
revisions.
B. GeoSoils Report, dated May 4, 1994, Supplemental Geotechnical
Investigation of Lots 14 through 22, Phase 1 of Tentative Parcel Map
24085, Temecula, Riverside County, Califomia; W.O. 686-A-RC
C. Schaefer Dixon Associates, Inc., Report on Geotechnical Investigation,
Assessment District No. 155, Parcel Map 24085, 24086, 21029, 21382,
and 21383, Rancho Califomia, Riverside County, California, dated June 7,
1989.
D. Leighton and Associates, Report on Preliminary Geotechnical
Investigation, Proposed Industrial I Commercial Site West of Cherry Street
and Diaz Road, A. D. No. 155, Rancho California, Riverside County,
California, dated June 23, 1986.
E. Technical References - see Appendix
Dear Mr. Harrison:
According to your request and signed authorization, we have performed an Updated Geotechnical
\ Geologic Engineering Study for the subject project. The purpose of this study was to evaluate
the existing geologic and geotechnical conditions within the subject property with respect to
recommendations for fine grading of the site and design recommendations for foundations, slabs
on-grade, pavements, etc., for the proposed development. Submitted, herewith, are the results of
this firm's findings and recommendations, along with the supporting data.
Los Angeles Office
Post Offk:e Box 1497
lancaster, CA 93534
(805) 940-1200 f Fax: 940-1202
Orange County Office
2615 Orange Avenue
Sanla Ana. CA 92707
(714) 546-4051 / Fax: 546-4052
Corporate Office
41607 Enterprise Circle North, Suite 1 . Temecula . California 92590 . (909) 676-3095 . Fax: (909) 676-3294
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1996
Page 2
1.0
EXECUTIVE SUMMARY
An updated geotechnical study of the subsurface conditions of the subject site has been
performed for the proposed development. Exploratory excavations have been performed
and earth material samples subjected to laboratory testing. The data have been analyzed
with respect to the project information furnished to us for the proposed development. It is
the opinion of this firm that the proposed development is feasible from a geotechnical I
geologic standpoint, provided that the recommendations presented in this report are
followed in the design and construction of the project.
INTRODUCTION
Authorization: This report presents the results of the updated geotechnical \ geological
engineering study performed on the subject site for the proposed development.
Authorization to perform this study was in the form of a signed proposal from EnGEN
Corporation to Westside City Associates I, LLC, dated July 29, 1996, Proposal Number
P10097 -C - GS - EA1.
Scope of Studv: The scope of work performed for this study was designed to determine
and evaluate the surface and subsurface conditions within the subject site with respect to
geotechnical characteristics, and to provide recommendations and criteria for use by the
Design Engineers and Architect for the development of the site and for design and
construction of the proposed development. The scope of work included the following: 1)
site reconnaissance and surface geologic mapping: 2) subsurface exploration; 3)
sampling of on-site earth materials; 4) laboratory testing; 5) engineering analysis of field
and laboratory data; and 6) the preparation of this report. The scope of work performed
for this report did not include an environmental assessment of the property or opinions
relating to the possibility of surface or subsurface contamination by hazardous or toxic
EnGEN Corporation
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Westside City Associates I, LLC
Project No. T1075-G5
August 1996
Page 3
substances. In addition, evaluation of on-site private sewage disposal systems for the
proposed development was not part of this study.
2.3 Previous Site Studies: Previous subsurface explorations and testing have been
performed on the subject site (References S, C and D).
3.0 PROPOSED DEVELOPMENT I PROJECT DESCRIPTION
The proposed project is the rough grading of 10 parcels for future development. It is our
understanding that each parcel will be developed into commercial \ industrial sites. Parcel
Number 1 will be developed into a concrete tilt-up structure and will be approximately
~~l~are feet in area. The other parcels will be developed on an as-required basis
and should be reviewed by the Geotechnical Consultant to determine if additional
geotechnical studies are required. It is assumed that relatively light loads will be imposed
on the foundation soils. The foundation loads are not anticipated to exceed 4,000 pounds
per lineal foot (pit) for continuous footings. The proposed structure floor will consist of a
concrete slab cast on compacted subgrade. The proposed grading for the site will
typically encompass maximum cuts on the order of 15 to 17-feet and fills ranging from 0.0
to 10 and 11-feet. However, an isolated stockpile in the southwestern corner of the site
will require cuts of 42-feet maximum to facilitat~ the development. The objective of the
development is to create pads for industrial/commercial structures, with associated
driveways and parking area. The maximum slope height will be approximately 23-feet and
will be a 2:1 (horizontal to vertical) fill over cut slope. The above project description and
assumptions were used as the basis for the field and laboratory exploration and testing
programs and the engineering analysis for the conclusions and recommendations
presented in this report. This office should be notified if structures, foundation loads,
grading, and/or details other than those represented herein are proposed for final
EnGEN Corporation
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Westside City Associates J, LLC
Project No. T1075-GS
Augusl1996
Page 4
development of the site so a review can be performed, supplemental evaluation made,
and revised recommendations submitted, if required.
4.0 SITE DESCRIPTION
4.1. Location: The site encompasses approximately 65 acres and is located west of Diaz
Road and north of Avenida De Ventas, in the City of Temecula, Riverside County,
California.
4.2 LeQal Description: Parcels 1 through 10 of Parcel Map 24085, County of Riverside (APN
909-120-022).
4.3 TOPoQraphv: The topography of the site at the time of this study was relatively flat on the
eastern portion of the property and gently to moderately sloping on the west side of the
property. A portion of the west side of the property had been previously graded flat and
some fill had been stockpiled immediately south of the graded pad. Drainage on the
property was toward the northeast.
4.4 VeQetation: At the time of the field study, vegetation across the site was light to moderate
and consisted of seasonal grasses, weeds, and bushes.
4.5 Structures: At the time of the field study, there were no existing buildings or other types
of structures on the site. Heavy construction equipment was stored on the previously
graded pad at the west portion of the property.
5.0 FIELD STUDY
Site observations and geologic mapping were conducted on August 1, 1996, by our Staff
Geologist. A study of the property's subsurface condition was performed to evaluate
underlying eartl:1 strata and the presence of groundwater. Six (6) exploratory borings were
excavated on the study site on August 1, 1996. The borings were performed by Scott's
EnGEN Corporation
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Westside City Associates I, LLC
Project No. T1075-GS
August 1996
Page 5
Drilling, using a truck-mounted, CME-55 drill rig equipped with 8.0-inch outside diameter
hollow-stem augers. The maximum depth explored was approximately 41.5-feet below
the existing land surface at the excavation locations. Bulk and relatively undisturbed
samples of the earth materials encountered were obtained at various depths in the
exploratory borings and returned to our laboratory for verification of field classifications and
testing. Bulk samples were obtained from cuttings developed during the excavation
process and represent a mixture of the soils within the depth indicated on the logs.
Relatively undisturbed samples of the earth materials encountered were obtained by
driving a thin-walled steel sampler lined with 1.0-inch high, 2.42-inch inside diameter brass
rings. The sampler was driven with successive drops of a 140-pound weight having a free
fall of approximately 3D-inches. The blow counts for each successive 6.0-inches of
penetration, or fraction thereof, are shown in the Exploratory Boring Log Summaries
presented in the Appendix. The ring samples were retained in close-fitting moisture-proof
containers and returned to our laboratory for testing. The approximate locations of the
exploratory excavations are denoted on the Geotechnical Study Site Plan. The
exploratory boring excavations were backfilled with excavated soil.
LABORATORY TESTING
General: The results of laboratory tests performed on samples of earth material obtained
during the field study are presented in the Appendix. Following is a listing. and brief
explanation of the laboratory tests which were performed. The samples obtained during
the field study will be discarded 30 days after the date of this report. This office should be
notified immediately if retention of samples will be needed beyond 30 days.
Classification: The field classification of soil materials encountered in the exploratory
borings was verified in the laboratory in general accordance with the Unified Soils
EnGEN Corporation
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6.3
6.4
6.5
Westside City Associates I, LLC
Project No. T1075-GS
Augusl199S
Page S
Classification System, ASTM D2488-90, Standard Practice for Determination and
Identification of Soils (Visual-Manual Procedures). The final classification is shown in the
Exploratory Boring Log Summaries presented in the Appendix.
In-Situ Moisture Content and Densitv Test: The in-situ moisture content and dry
density were determined in general accordance with ASTM D2216-90 and D2937-
83(1990) procedures, respectively, for each selected undisturbed sample obtained. The
dry density is determined in pounds per cubic foot and the moisture content is determined
as a percentage of the oven dry weight of the soil. Test results are shown in the
Exploratory Boring Log Summaries presented in the Appendix.
Consolidation Test: Settlement predictions of the on-site soil and compacted fill behavior
under load were made, based on consolidation tests that were performed in general
accordance with ASTM D2435-90 procedures. The consolidation apparatus is designed to
receive a 1.0-inch high, 2.416-inch diameter ring sample. Porous stones are placed in
contact with the top and bottom of each specimen to permit addition and release of pore
water and pore pressure. Loads normal to the face of the specimen are applied in several
increments in a geometric progression under both field moisture and submerged
conditions. The resulting changes in sample thickness are recorded at selected time
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intervals. Water was added to the test apparatus at a load of 1600 psf to create a
submerged condition and to measure the collapse potential (hydroconsolidation) of the
sample. The resulting change in sample thickness was recorded.
Maximum Drv Densitv I Optimum Moisture Content Relationship Test: Maximum dry
density / optimum moisture content relationship determination was performed on samples
of near-surface earth material in general accordance with ASTM D1557-91 procedures
using a 4.0-inch diameter mold. Samples were prepared at various moisture contents and
compacted in five (5) layers using a 10-pound weight dropping 18-inches and with 25
EnGEN Corporation
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1996
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blows per layer. A plot of the compacted dry density versus the moisture content of the
specimens is constructed and the maximum dry density and optimum moisture content
determined from the plot.
Direct Shear Test: A direct shear test was performed on a selected in-situ sample of
near-surface earth material in general accordance with ASTM D3080-90 procedures. The
shear machine is of the constant strain type. The shear machine is designed to receive a
1.0-inch high, 2.416-inch diameter ring sample. Specimens from the sample were sheared
at various pressures normal to the face of the specimens. The specimens were tested in
a submerged condition. The maximum shear stresses were plotted versus the normal
confining stresses to determine the shear strength (cohesion and angle of internal friction).
Expansion Test: A laboratory expansion test was performed on a sample of near-surface
earth material in general accordance with the Uniform Building Code (UBC) Standard No.
29-2 procedures. In this testing procedure, a remolded sample is compacted in two (2)
layers in a 4.0-inch diameter mold to a total compacted thickness of approximately 1.0-
inch by using a 5.5-pound weight dropping 12-inches and with 15 blows per layer. The
sample should be compacted at a saturation between 49 and 51 percent. After remolding,
the sample is confined under a pressure of 144 pounds per square foot (pst) and allowed
to soak for 24 hours. The resulting volume change due to the increase in moisture content
within the sample is recorded and the Expansion Index (EI) calculated. The expansion
test result is presented on the UBe Laboratory Expansion Test Results sheet.
Particle Size Analysis Test: Particle size analyses were performed on selected samples
of earth materials in general accordance with ASTM D422-63(1990) procedures. The test
is performed by taking an oven dry sample of soil material, washing it over a No. 200
sieve, drying the soil retained on the No. 200 sieve, and then shaking it through a series of
nested sieves of various size openings. The weight of soil material retained on each sieve
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1996
Page 8
size is measured and the resulting percentage retained on each sieve is calculated based
on the original total dry sample weight. The cumulative results of the analyses are
presented on the Grain Size Distribution Test Report.
SITE CONDITIONS
GeoloQic SettinQ: The site is located in the Northern Peninsular Range on the southern
sector of the structural unit known as the Perris Block. The Perris Block is bounded on the
northeast by the San Jacinto Fault Zone, on the southwest by the Elsinore Fault Zone, and
on the north by the Cucamonga Fault Zone. The southern boundary of the Perris Block is
not as distinct, but is believed to coincide with a complex group of faults trending southeast
from the Murrieta, California, area. The Peninsular Range is characterized by large
Mesozoic age intrusive rock masses fianked by volcanic, metasedimentary, and
sedimentary rocks. Various thicknesses of colluvial I alluvial sediments derived from the
erosion of the elevated portions of the region fill the low lying areas. Man-made fill and
alluvium underlie the subject property and surrounding area. Alluvial materials underlie
the man-made fill materials on the site. The earth materials encountered on the subject
site are described in more detail in subsequent sections of this report.
FaultinQ: The Murrieta Creek Fault traverses the property and has been documented by
previous consultants (References C and D). Offsets have been surveyed and placed on
the rough grading plans (Reference A). In addition, the east portion of the subject site is
located within the limits of the County of Riverside Special Studies as currently delineated
by the Riverside County Special Studies Zone Maps. The Wildomar fault segment of the
Elsinore Fault Zone is located approximately 2,500 feet northeast of the subject site. A
maximum credible earthquake on the Elsinore Fault Zone could produce a peak ground
acceleration of 0.86g at the subject site.
EnGEN Corporation
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Westside City Associates I, LLC
Project No. T1075-GS
August 1996
Page 9
Elsinore Fault Zone: The Elsinore Fault Zone is a prominent and youthful structural
boundary between the Perris Block to the northeast and the Santa Ana mountains to the
southwest. The Elsinore Fault system is a major right lateral strike-slip fault system that
has experienced strong earthquakes in historical times, (1856, 1894, and 1910), and
exhibits late Quaternary movement.
7.3 Earth Materials: A brief description of the earth materials encountered in the exploratory
excavations is presented in the following sections. A more detailed description of the earth
materials encountered is presented on the Exploratory Boring Log Summaries presented
in the Appendix. The earth material strata as shown on the logs represent the conditions
in the actual exploratory locations and other variations may occur between the
excavations. Lines of demarcation between the earth materials on the logs represented
the approximate boundary between the material types; however, the transition may be
gradual.
7.3.1 Artificial Fill (Afll: Fill materials were observed stockpiled along Avenida De Ventas
near Diaz Road and near proposed Winchester Road. These fills are undocumented and
were previously stockpiled and are as high as approximately 40-feet in the southwestern
corner of the site near proposed Winchester Road and approximately G.O-feet near Diaz
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Road. These materials were observed to consist of silty sands and sandy silts and to be
slightly moist and loose. Undocumented fill materials also exist in the exploratory trenches
conducted during earlier geotechnical investigations by Schaefer Dixon and Associates
(Reference C).
7.3.2 SloDewash (no maD svmboll: Slopewash was encountered on the natural, gently to
moderately sloping area in the central portion of the property. Slopewash materials were
encountered to depths of 1.5 to 3.0-feet and consisted of silty sands to sandy silts and
were found to be dry and soft.
EnGEN Corporation \1,
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Westside City Associates I, LLC
Project No. T1 075-GS
August 1996
Page 10
7.3.3 Alluvium (Qall: Alluvium was encountered on the lower eastern portion of the property to
the maximum depth explored (41.5-feet). Alluvial materials consisted of sandy silt, silty
sand, silty clay, clayey silt and sand and were found to be slightly moist to wet and loose to
dense in place. Alluvium was also observed in the narrow drainage areas located south of
the graded pad area. Alluvium in these drainage areas appeared to be of minimal
thickness (2.0 to 3.0-feet) and consisted of silty sands.
7.3.4 Bedrock (Pauba Formation - Qp): Pauba Formation bedrock was encountered below
the slopewash and was exposed on the graded pad in the elevated portions of the site to
the maximum depths explored. Bedrock materials consist of sandstone, siltstone, sandy
siltstone and silty sandstone and were found to be slightly moist and dense in place. The
top 1.0 to 2.0-feet of bedrock is weathered. Earlier studies (Reference C) and
observations of in-situ samples reveal relatively horizontal bedding.
7.4 Groundwater: Groundwater was encountered at 24 to 28-feet below the existing ground
surface in the lower flat lying portions on the east side of the property.
7.5 liquefaction Evaluation: Liquefaction is a phenomenon where a sudden large decrease
of shearing resistance takes place in fine-grained cohesion less and/or low plasticity
cohesive soils due to the cyclic stresses produced by earthquakes causing a sudden, but
temporary, increase of porewater pressure. The increased porewater pressure occurs
below the water table, but can cause propagation of groundwater upward into overlying
soil and possibly to the ground surface and cause sand boils as excess porewater
escapes. Potential hazards due to liquefaction include significant total and/or differential
settlements of the ground surface and structures as well as possible collapse of structures
due to loss of support of foundations. It has been shown by laboratory testing and from
the analysis of soil conditions at sites where liquefaction has occurred that the soil types
most susceptible to liquefaction are saturated, fine sand to sandy silt with a mean grain
EnGEN Corporation
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Westside City Associates I, LLC
Project No. T1075-GS
August 1 996
Page 11
size ranging from approximately 0.075 mm to 0.5 mm. These soils derive their shear
strength from intergranular friction and do not drain quickly during earthquakes. Published
studies and field and laboratory test data indicate that coarse sands and silty or clayey
sands beyond the above-mentioned grain size range are considerably less vulnerable to
liquefaction. To a large extent, the relative density of the soil also controls the
susceptibility to liquefaction for a given number of cycles and acceleration levels during a
seismic event. Other characteristics such as confining pressure and the stresses created
within the soil during a seismic event also affect the liquefaction potential of a site.
Liquefaction of soil does not generally occur below depths of 40 to 50-feet below the
ground surface due to the confining pressure at that depth. Moreover, saturated fine
sands with relative densities of approximately 70 percent or greater are not likely to liquefy,
even under very severe seismic events.
A liquefaction analysis was performed as part of this study using a computer program
(Liquefy2, Version 1.30, by Thomas F. Blake). The analysis revealed factors of safety
below 1.0. Therefore, the potential for liquefaction of the site is considered to be
moderate-to-high due to the following conditions:
. The existence of nearby major faults m?y cause exceptionally high ground
accelerations at the site.
. The fine grained nature (silty fine sands, fine sands, fine to medium sands, and
fine sandy silts) of the earth materials encountered make them susceptible to
liquefaction.
. Low to medium relative densities of some of the in-situ soils above and below the
groundwater table as determined by the Standard Penetration Resistance tests
performed and blow counts obtained in driving the ring sampler during the field
study and the in-situ densities of the soils.
. Historically, the groundwater table within the vicinity of the site has risen to less
than 10-feet below ground surface. This data was taken into consideration when
analyzing for the potential for liquefaction.
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Westside City Associates I, LLC
Project No. T1075-GS
Augusl1996
Page 12
Based on the proposed removal depths (see below) and the planned fills, a blanket of
engineered fill greater than 10-feet thick is expected below future proposed structures.
The proposed thickness (minimum of 10-feet) of this engineered fill is expected to mitigate
for the effects of liquefaction.
8.0
CONCLUSIONS AND RECOMMENDATIONS
8.1
General: The conclusions and recommendations presented in this report are based on
the results of field and laboratory data obtained from the exploratory excavations located
across the property, experience gained from work conducted by this firm on projects within
the property and general vicinity, and the project description and assumptions presented in
the Proposed Development / Project Description section of this report. Based on a review
of the field and laboratory data and the engineering analysis, the proposed development is
feasible from a geotechnical I geologic standpoint. The actual conditions of the near-
surface supporting material across the site may vary. The nature and extent of variations
of the surface and subsurface conditions between the exploratory excavations may not
become evident until construction. If variations of the material become evident during
construction of the proposed development, this office should be notified so that EnGEN
Corporation can evaluate the characteristics of the material and, if needed, make
revisions to the recommendations presented herein. Recommendations for general site
grading, foundations, slab support, pavement design, slope maintenance, etc., are
presented in the subsequent paragraphs.
Specific earthwork and foundation
recommendations for each parcel should be made when specific grading and foundation
plans become available.
Earthwork Recommendations:
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8.2.1
8.2.2
8.2.3
8.2.4
Westside City Associates I, LLC
Project No. T1075-GS
August 1996
Page 13
General: The recommendations presented in this report are based on the Reference A
grading plan. When precise grading plans become available, they should be reviewed by
this office to determine if additional recommendations are necessary. No construction of
habitable structures should take place in the designated fault zones (restricted use zones).
The grading recommendations presented in this report are intended for: 1) the use of a
conventional shallow foundation system and concrete slabs cast on-grade; and 2) the
rework of unsuitable, near-surface earth materials to create an engineered building pad
and suitable support for exterior hardscape (sidewalks, patios, etc.) and pavement. If
pavement subgrade soils are prepared at the time of rough grading of the building site and
the areas are not paved immediately, additional observations and testing of the subgrade
soil will have to be performed before placing aggregate base material or asphaltic concrete
or PCC pavement to locate areas which may have been damaged by construction traffic,
construction activities, and/or seasonal wetting and drying.
The following
recommendations may need to be modified and/or supplemented during rough grading as
field conditions require.
ClearinQ: All debris, grasses, weeds, brush and other deleterious materials should be
removed from the proposed building, exterior hardscape and pavement areas and areas
to receive structural fill before grading is performed. No disking or mixing of organic
material into the soils should be performed. Man-made objects encountered should be
overexcavated and exported from the site.
Excavation Characteristics: Excavation and trenching within the subject property is
anticipated to be relatively easy.
Suitabilitv of On-Site Materials as Fill: In general, the on-site earth materials present
are considered suitable for reuse as fill. Fill materials should be free of significant amounts
of organic materials and/or debris and should not contain rocks or clumps greater than
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1 996
Page 14
3.0-inches in maximum dimension.
8.2.5 Removal and Recompaction: All existing uncontrolled or undocumented fills (including
former exploratory trenches not located in the fault zone - see Reference C) and/or
unsuitable, loose, or disturbed near-surface slopewash and alluvium in proposed areas
which will support structural fills, structures, exterior hardscape (sidewalks, patios, etc.),
and pavement should be prepared in accordance with the following recommendations for
grading in such areas.
Parcel 1: All undocumented fill should be removed. All unsuitable alluvium should be
removed to competent alluvium. In the building pad area, and to within 5.0-feet outside
perimeter footings, the alluvium shall be removed to at least 4.0-feet below native grade,
but not less than 10-feet below finished pad grade. The alluvial removal over the
remainder of the site should be 2.0-feet below natural grade. The exposed surface should
be scarified to a depth of 12-inches, brought to within 2.0 percent of optimum moisture,
and compacted to at least 90 percent of maximum density.
Parcels 8, 9, and 10: All undocumented fill shall be removed. All unsuitable alluvium
should be removed to competent alluvium. Removal depths in the alluvial soils are
expected to be approximately 2.0-feet. All natural bottom areas should be inspected by
the Project Engineering Geologist or the Project Geotechnical Engineer, or their
representatives. Prior to placing fill, the exposed surface should be scarified 12-inches,
brought to within 2.0 percent of optimum moisture content, and compacted to a minimum
of 90 percent relative compaction before placement of fill. Maximum dry density and
optimum moisture content for compacted materials should be determined according to
ASTM D1557-91 procedures. Although removals are not necessary within the designated
fault zones, removals may be required in these areas in the future if they exist within a 1:1
plane projected outward from future proposed perimeter building footings.
Parcels 2, 3, 4, 5, 6 and 7: All undocumented fill, slopewash, alluvium and weathered
bedrock should be removed to competent bedrock. Removals in these areas are
expected to be 1.0 to 4.0-feet. All natural bottom areas should be inspected by the Project
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Westside City Associates I, LLC
Project No. T1075-GS
August 1996
Page 15
Engineering Geologist or the Project Geotechnical Engineer, or their representatives. In
areas to receive fill, the existing ground surface should be scarified 12-inches, brought to
within 2.0 percent of optimum moisture content, and compacted to a minimum of 90
percent relative compaction before placement of fill. Maximum dry density and optimum
moisture content for compacted materials should be determined according to ASTM
D1557 -91 procedures. Although removals are not necessary within the designated fault
zones, removals may be required in these areas in the future if they exist within a 1: 1
plane projected outward from future proposed perimeter building footings.
The proposed grading will probably leave cut I fill transition areas in graded Parcel
Numbers 2, 3, 4, 5, 6 and 7. These areas will need to be addressed when final
grading and building plans become available. It should be noted that since most of the
former exploratory trenches are located in the fault zone, recompaction of these trenches
will not be necessary. However, trench SDA-9 and portions of trench SDA-4 lie outside
the fault zone and will need to be excavated and recompacted if the bottoms of these
trenches are deeper than the alluvial removals. These trenches are located on the
attached Site Plan.
8.2.6 Fill Placement Requirements: All fill material, whether on-site material or import, should
be approved by the Project Geotechnical Engineer and/or his representative before
placement. All fill should be free from vegetation, organic material, debris, and oversize
material. Import fill should be no more expansive than the existing on-site material as
determined by UBC 29-2 procedures. Approved fill material should be placed in horizontal
lifts not exceeding 10-inches in compacted thickness and watered or aerated to obtain
near optimum moisture content (:t2.0 percent of optimum). Each lift should be spread
evenly and should be thoroughly mixed to ensure uniformity of soil moisture. Structural fill
should meet a minimum relative compaction of 90 percent. Maximum dry density and
optimum moisture content for compacted materials should be determined in accordance
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Project No. T1075-GS
August 1996
Page 16
with ASTM D1557 -91 procedures. Moisture content of fill materials should not vary more
than 2.0 percent from optimum, unless approved the Project Geotechnical Engineer.
8.2.7 Compaction Equipment: It is anticipated that the compaction equipment to be used for
the project will include a combination of rubber-tired and sheepsfoot rollers to achieve
proper compaction. Compaction by rubber-tired or track-mounted equipment, by itself,
may not be sufficient. Adequate water trucks, water pulls, and/or other suitable equipment
should be available to provide sufficient moisture and dust control. The actual selection of
equipment is the responsibility of the contractor performing the work and should be such
that uniform and proper compaction of the fill is achieved.
8.2.8 ShrinkaQe and Subsidence: There will be a material loss due to the clearing and
grubbing operations. Shrinkage of loose fill that is excavated and replaced as compacted
fill should be anticipated. It is estimated that the average shrinkage of the near-surface
soils within the anticipated cuts when compacted to 90 percent relative compaction will
vary across the property, being estimated at less than 5.0 percent in the western portion of
the site (Parcels 3, 4, 5, and 6); on the order of 10 percent in the central section of the site
(Parcels 2 and 7); and on the order of 15 percent in the western portion of the site (Parcels
1, 8, 9, and 10). A higher relative compaction would mean a larger shrinkage value.
Subsidence of the natural deposits due to the placement of fill is only expected to affect
Parcels 1, 8, 9, and 10, where a blanket of fill on the order of 4.0 to 10-feet thick will be
placed during grading. The results of calculations indicate that subsidence of 3.0 to 5.0-
inches may be experienced. The majority of that subsidence is expected to be rapid,
occurring within the time frame anticipated for construction. Some secondary
consolidation, however, is expected to be realized as long-term settlement, but is
projected as being relatively uniform across the limits of anyone parcel.
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1996
Page 17
8.2.9 Subdrains: Although the need for subdrains is not anticipated at this time, final
recommendations should be made during grading by the Project Engineering Geologist.
8.2.10 Observation and Testing: During grading, observation and testing should be conducted
by the Geotechnical Engineer and/or his representative to verify that the grading is being
performed according to the recommendations presented in this report. The Project
Geotechnical Engineer and/or his representative should observe the scarification and the
placement of fill and should take tests to verify the moisture content, density, uniformity
and degree of compaction obtained. Where testing demonstrates insufficient density,
additional compaction effort, with the adjustment of the moisture content where necessary,
should be applied until retesting shows that satisfactory relative compaction has been
obtained. The results of observations and testing services should be presented in a formal
Finish Grading Report following completion of the grading operations. Grading operations
undertaken at the site without the Geotechnical Engineer and/or his representative present
may result in exclusions of the affected areas from the finish grading report for the project.
The presence of the Geotechnical Engineer and/or his representative will be for the
purpose of providing observations and field testing and will not include any supervision or
directing of the actual work of the contractor or the contractor's employees or agents.
Neither the presence and/or the non-presence of the Geotechnical Engineer and/or his
field representative nor the field observations and testing shall excuse the contractor in
any way for defects discovered in the contractor's work.
8.2.11 Kevwavs: The proposed grading will create fill slopes over cut slopes. If the proposed fill
slope is to be placed over natural ground with gradients steeper than 5: 1 (horizontal to
vertical) then a keyway should be installed. The keyway should be sloped downward (a
minimum of 2 percent gradient) into the slope and be a minimum of 15-feet wide into
competent bedrock. All keyways should be inspected by the Project Geotechnical
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Wests ide City Associates I, LLC
Project No. T1075-GS
August 1996
Page 18
Engineer or the Project Engineering Geologist and/or their representative.
8.2.12 BenchinQ: Compacted fill placed on natural slope surfaces inclined at 5: 1 (horizontal to
vertical) or steeper should be placed on a series of level benches excavated into
competent native materials. The benches should have a minimum 4.0-foot high backcut
into competent material.
8.2.13 Fill SloDes: Finish fill slopes should not be inclined steeper than 2: 1 (horizontal to
vertical). Fill slope surfaces should be compacted to 90 percent relative compaction to the
face of the finished slope. Fill slopes should be constructed in a skillful manner so that
they are positioned at the design orientations and slope ratio. Achieving a uniform slope
surface by subsequent thin wedge filling should be avoided. Add-on correction to a fill
slope should be conducted under the observation and recommendations of the project
Geotechnical Engineer or Engineering Geologist. The proposed add-on correction
procedures should be submitted in writing by the contractor before commencement of
corrective grading and reviewed by the project Geotechnical Engineer or Engineering
Geologist. Compacted fill slopes should be backrolled with suitable equipment for the type
of soil being used during fill placement at intervals not exceeding 4.0-feet in vertical height.
As an alternative to the backrolling of the fill slopes, over-filling of the slopes will be
considered acceptable and preferred. The fill slope should be constructed by over-filling
with compacted fill a minimum of 3.0-feet horizontally, and then trimmed back to expose
the dense inner core of the slope surface.
8.3.14 Cut SloDes: Finish cut slopes in bedrock should not be inclined steeper than 2: 1
(horizontal to vertical). All cut slopes should be observed by the project Geotechnical
Engineer, Engineering Geologist and/or their representative during grading to provide
supplemental recommendations for safe slopes, if required. Cut slopes that face in the
same direction as the prevailing natural Slope will require top of cut paved interceptor
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Westside City Associates J. LLC
Project No. T1075-GS
August 1996
Page 19
swales.
8.2.15 Soil Expansion Potential: Upon completion of fine grading of the building pad, near-
surface samples should be obtained for expansion potential testing to verify the
preliminary expansion test results and the foundation and slab-on-grade recommendations
presented in this report. The results of recent testing indicate an expansion index of 64
which is classified as a Medium expansion potential.
8.3 Seismic DesiQn Recommendations:
8.3.1 DesiQn Fault Zone: The most significant earthquakes that may affect the site are
anticipated to occur along the Elsinore Fault Zone.
8.3.2 Ground Accelerations: An earthquake originating along the Elsinore Fault Zone with a
maximum credible magnitude of 7.5 could be expected to generate a peak ground
acceleration at the site in excess of approximately 0.86g. It should be noted that the
intensity of the anticipated motions will depend on the magnitude of the earthquake and on
the distance of the zone of maximum energy release from the site.
8.3.3 DesiQn Parameters: The above acceleration is a peak acceleration and is not considered
representative for design parameters. Recent studies suggest that the repeatable
horizontal acceleration should be of greater concern in structural design than the single
maximum peak acceleration for sites that are less than 20 miles from the epicenter. The
repeatable horizontal acceleration for the site is considered 65 percent of the peak
acceleration. Therefore, it is expected that, during the design life of the project, the
proposed structures will experience repeatable horizontal ground surface accelerations of
approximately 0.56g. Higher repeatable horizontal ground surface accelerations are
possible within the subject property; however, the probability of these accelerations
occurring is considered low. Uniform Building Code (UBC) seismic design requirements
are based upon criteria limited to fulfilling life safety concepts. An Effective Peak
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8.4
8.4.1
8.4.2
Westside City Associates I, LLC
Project No. T1075-GS
August 1 996
Page 20
Acceleration (EPA) of 0.40g (Z = 0.40) for Seismic Zone 4 has been assumed for the
derivation of seismic formulas presented in the 1994 UBC. Based on the Structural
Engineers Association of California, Seismology Committee, 1980, structures designed
according to the provisions of the UBC should be able to resist major earthquakes of the
severity anticipated at the subject site without collapse, although structural damage could
occur. However, as repeatable accelerations for the site may approach 0.56g, the
Structural Engineer may want to incorporate additional design parameters.
Foundation DesiQn Recommendations:
General: Foundations for the proposed structure may consist of conventional column
footings and continuous wall footings founded upon properly compacted fill. The
recommendations presented in the subsequent paragraphs for foundation design and
construction are based on geotechnical characteristics and a medium expansion potential
for the supporting soils and should not preclude more restrictive structural requirements.
The Structural Engineer for the project should determine the actual footing width and
depth to resist design vertical, horizontal, and uplift forces.
Foundation Size: Continuous footings should have a minimum width of 12-inches.
Continuous footings should be continuously reinforced with a minimum of two (2) No. 4
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steel reinforcing bar located near the top and two (2) No. 4 steel reinforcing bar located
near the bottom of the footings to minimize the effects of slight differential movements
which may occur due to minor variations in the engineering characteristics or seasonal
moisture change in the supporting soils. Column footings should have a minimum width of
18-inches by 18-inches and be suitably reinforced, based on structural requirements. A
grade beam, founded at the same depths and reinforced the same as the adjacent
footings, should be provided across doorway and garage entrances.
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Page 21
8.4.3 Depth of Embedment: Exterior and interior footings founded in properly compacted fill
should extend to a minimum depth of 18-inches below lowest adjacent finish grade for the
one (1) story structure. The foundations should be founded in properly compacted fill.
8.4.4 Bearinq Capacitv: Provided the recommendations for site earthwork, minimum footing
width, and minimum depth of embedment for footings are incorporated into the project
design and construction, the allowable bearing value for design of continuous and column
footings for the total dead plus frequently-applied live loads is 2500 psf for continuous
footings and 2500 psf for column footings in properly compacted fill material. This value
may be increased by 20 percent for each additional foot of depth and/or foot of width to a
maximum of 3.0 times the designated allowable value. The allowable bearing value has a
factor of safety of at least 3.0 and may be increased by 33.3 percent for short durations of
live and/or dynamic loading such as wind or seismic forces.
8.4.5 Settlement: The settlement estimates presented in this section address only the
proposed development on Parcel 1. All other parcels will need to be evaluated on an
individual basis. Footings designed according to the recommended bearing values for
continuous and column footings, respectively, and the maximum assumed wall and
column loads are not expected to exceed a maximum settlement of 0.75-inch or a
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differential settlement of 0.25-inch in properly compacted fill.
8.4.6 Lateral Capacitv: Additional foundation design parameters based on compacted fill for
resistance to static lateral forces, are as follows:
Allowable Lateral Pressure (Equivalent Fluid Pressure), Passive Case:
Compacted Fill - 200 pcf
Bedrock -
Allowable Coefficient of Friction:
Compacted Fill - 0.35
Bedrock -
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Page 22
Lateral load resistance may be developed by a combination of friction acting on the base
of foundations and slabs and passive earth pressure developed on the sides of the
footings and stem walls below grade when in contact with undisturbed, properly,
compacted fill material. The above values are allowable design values and have safety
factors of at least 2.0 incorporated into them and may be used in combination without
reduction in evaluating the resistance to lateral loads. The allowable values may be
increased by 33.3 percent for short durations of live and/or dynamic loading, such as wind
or seismic forces. For the calculation of passive earth resistance, the upper 1.0 foot of
material should be neglected unless confined by a concrete slab or pavement. The
maximum recommended allowable passive pressure is 5.0 times the recommended
design value.
8.5 Slab-on-Grade Recommendations: The recommendations for concrete slabs, both
interior and exterior, excluding PCC pavement, are based upon a medium expansion
potential for the supporting material as determined by Table 29-C of the Uniform Building
Code. Concrete slabs should be designed to minimize cracking as a result of shrinkage.
Joints (isolation, contraction, and construction) should be placed in accordance with the
American Concrete Institute (ACI) guidelines. Special precautions should be taken during
l.
placement and curing of all concrete slabs. Excessive slump (high water / cement ratio) of
the concrete and/or improper curing procedures used during either hot or cold weather
conditions could result in excessive shrinkage, cracking, or curling in the slabs. It is
recommended that all concrete proportioning, placement, and curing be performed in
accordance with ACI recommendations and procedures.
8.5.1 Interior Slabs: Interior concrete slabs-on-grade should be a minimum of 4.0-inches in
thickness and be underlain by a minimum of 1.0-inch of clean coarse sand or other
approved granular material placed on properly prepared subgrade per the Earthwork
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Project No. T1075-GS
August 1996
Page 23
Recommendations Section of this report. Minimum slab reinforcement should consist of
#3 reinforcing bars placed 18-inches on center in both directions, or a suitable equivalent.
The reinforcing should be placed at mid-depth in the slab. The concrete section and/or
reinforcing steel should be increased appropriately for anticipated excessive or
concentrated floor loads. In areas where moisture sensitive floor coverings are anticipated
over the slab, we recommend the use of a polyethylene vapor barrier with a minimum of
6.0 mil in thickness be placed beneath the slab. The moisture barrier should be
overlapped or sealed at splices and covered by a 1.0-inch minimum layer of clean, moist
(not saturated) sand to aid in concrete curing and to minimize potential punctures.
8.5.2 Exterior Slabs: All exterior concrete slabs cast on finish subgrade (patios, sidewalks,
etc., with the exception of PCC pavement) should be a minimum of 4.0-inches nominal in
thickness and be underlain by a minimum of 12.0-inches of soil that has been prepared in
accordance with the Earthwork Recommendation section of this report. Reinforcing in the
slabs and the use of a compacted sand or gravel base beneath the slabs should be
according to the current local standards.. Subgrade soils should be moisture conditioned
to at least optimum moisture content to a depth of 6.0-inches and proof compacted to a
minimum of 90 percent relative compaction based on ASTM D1557-91 procedures
immediately before placing aggregate base material or placing the concrete.
8.6 Pavement Desi~n Recommendations: The following are our recommendations for the
structural pavement section for the proposed parking and driveway areas for the subject
development. The pavement section has been determined in general accordance with
CAL TRANS design procedures and is based on an assumed Traffic Index (TI) and an R-
Value of at least 20 based on past laboratory test results of the site vicinity (see Reference
"8"). In areas where normal loads (cars, pickup trucks) are anticipated, the assumed TI is
4.0 and the pavement section should consist of a minimum of 3.0-inches of asphaltic
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Project No. T1075-GS
August 1996
Page 24
concrete (AC.) over 4.5-inches of Class 2 Aggregate Base (AB.). In areas where heavy
loads (large trucks, trash trucks, heavy machinery, etc.) are anticipated, the assumed TI is
5.0 and the pavement section should consist of a minimum of 3.0-inches of AC. over 7.0-
inches of Class 2 AB. Asphalt concrete pavement materials should be as specified in
Section 39 of the current CAL TRANS Standard Specifications or a suitable equivalent.
Aggregate base should conform to Class 2 material as specified in Section 26-1.02B of the
current CAL TRANS Standard Specifications or a suitable equivalent. The subgrade soil,
including utility trench backfill, should be compacted to at least 90 percent relative
compaction. The aggregate base material should be compacted to at least 95 percent
relative compaction. Maximum dry density and optimum moisture content for subgrade
and aggregate base materials should be determined according to ASTM 01557-91
procedures. In dumpster pick-up areas, and in areas where semi-trailers are to be parked
on the pavement, such that a considerable load is transferred from small wheels, it is
recommended that rigid Portland Cement concrete pavement with a minimum thickness of
6.0-inches be provided in these areas. This will provide for the proper distribution of loads
to the subgrade without causing deformation of the pavement surface. Special
consideration should also be given to areas where truck traffic will negotiate small radius
turns. Asphaltic concrete pavement in these areas should utilize stiffer emulsions or the
areas should be paved with Portland Cement concrete. If pavement subgrade soils are
prepared at the time of rough grading of the building site and the areas are not paved
immediately, additional observations and testing will have to be performed before placing
aggregate base material, asphaltic concrete, or PCC pavement to locate areas that may
have been damaged by construction traffic, construction activities, and/or seasonal wetting
and drying. In the proposed pavement areas, soil samples should be obtained at the time
the subgrade is graded for R-Value testing according to California Test Method 301
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Project No. T1075-GS
August 1996
Page 25
procedures to verify the pavement design recommendations.
8.7 Utilitv Trench Recommendations: Utility trenches within the zone of influence of
foundations or under building floor slabs, exterior hardscape, and/or pavement areas
should be backfilled with properly compacted soil. All utility trenches within the building
pad and extending to a distance of 5.0-feet beyond the building exterior footings should be
backfilled with on-site or similar soil. Where interior or exterior utility trenches are
proposed to pass beneath or parallel to building, retaining wall, and/or decorative concrete
block perimeter wall footings, the bottom of the trench should not be located below a 1:1
plane projected downward from the outside bottom edge of the adjacent footing unless the
utility lines are designed for the footing surcharge loads. It is recommended that all utility
trenches excavated to depths of 5.0-feet or deeper be cut back according to the
"Temporary Construction Cut" section of this report or be properly shored during
construction. Backfill material should be placed in a lift thickness appropriate for the type
of backfill material and compaction equipment used. Backfill material should be
compacted to a minimum of 90 percent relative compaction by mechanical means. Jetting
or flooding of the backfill material will not be considered a satisfactory method for
compaction unless the procedures are reviewed and approved in writing by the Project
Geotechnical Engineer. Maximum dry density and optimum moisture content for backfill
material should be determined according to ASTM D1557 -91 procedures.
8.8 Finish Lot DrainaQe Recommendations: Positive drainage should be established away
from the tops of slopes, the exterior walls of structures, the back of retaining walls, and the
decorative concrete block perimeter walls. Finish lot surface gradients in unpaved areas
should be provided next to tops of slopes and buildings to guide surface water away from
foundations and slabs and from flowing over the tops of slopes. The surface water should
be directed toward suitable drainage facilities. Ponding of surface water should not be
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8.9
8.10
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allowed next to structures or on pavements. In unpaved areas, a minimum positive
gradient of 2.0 percent away from the structures and tops of slopes for a minimum
distance of 5.0-feet and a minimum of 1.0 percent pad drainage off the property in a
nonerosive manner should be provided. Landscape trees and plants with high water
needs should be planted at least 5.0-feet away from the walls of the structures.
Downspouts from roof drains should discharge to a permanent all-weather surface which
slopes away from the structure a minimum of 5.0-feet from the exterior building walls. In
no case should downspouts from roof drains discharge into planter areas immediately
adjacent to the building unless there is positive drainage away from the structure and the
5.0-foot minimum discharge distance criteria is followed.
Planter Recommendations: Planters around the perimeter of the structures should be
designed to ensure that adequate drainage is maintained and minimal irrigation water is
allowed to percolate into the soils underlying the buildings. The planters should drain
directly onto surrounding paved areas or into a properly designed subdrain system.
TemDorarv Construction Excavation Recommendations: Temporary construction
excavations for rough grading, foundations, retaining walls, utility trenches, etc., more than
5.0-feet in depth and to a maximum depth of 15-feet should be properly shored or cut back
to the following inclinations:
Earth Material
Compacted Fill
Inclination
1:1
Alluvium
1.5:1
0.75:1
Pauba Formation Bedrock
No surcharge loads (spoil piles, earthmoving equipment, trucks, etc.) should be allowed
within a horizontal distance measured from the top of the excavation slope equal to 1.5
EnGEN Corporation
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times the depth of the excavation. Excavations should be initially observed by the project
Geotechnical Engineer, Geologist and/or their representative to verify the
recommendations presented or to make additional recommendations to maintain stability
and safety.
Moisture variations, differences in the cohesive or cementation
characteristics, or changes in the coarseness of the deposits may require slope flattening
or, conversely, permit steepening upon review by the project Geotechnical Engineer,
Geologist, or their representative. Deep utility trenches may experience caving which will
require special considerations to stabilize the walls and expedite trenching operations.
Surface drainage should be controlled along the top of the slope to preclude erosion of the
slope face. If excavations are to be left open for long periods, the slopes should be
sprayed with a protective compound and/or covered to minimize drying out, raveling,
and/or erosion of the slopes. For excavations more than 5.0-feet in depth which will not
be cut back to the recommended slope inclination, the contractor should submit to the
owner and/or the owner's designated representative detailed drawings showing the design
of shoring, bracing, sloping, or other provisions to be made for worker protection. If the
drawings do not vary from the requirements of the OSHA Construction Safety Orders
(CAL OSHA or FED OSHA, whichever is applicable for the project at the time of
construction), a statement signed by a Registered Civil or Structural Engineer in the State
of California, engaged by the contractor at his expense, should be submitted certifying that
the contractor's excavation safety drawings comply with OSHA Construction Orders. If
the drawings vary from the applicable OSHA Construction Safety Orders, the drawings
should be prepared, signed, and sealed by a Registered or Structural Engineer in the
State of California. The contractor should not proceed with any excavations until the
project owner or his designated representative has received and acknowledged the
properly prepared excavation safety drawings.
EnGEN Corporation
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Project No. T1075-GS
August 1996
Page 28
9.0 PLAN REVIEW
Subsequent to formulation of final plans and specifications for the project, but before bids
for construction are requested, grading and foundation plans for the proposed
development should be reviewed by EnGEN Corporation to verify compatibility with site
geotechnical conditions and conformance with the recommendations contained in this
report. If EnGEN Corporation is not accorded the opportunity to make the recommended
review, we will assume no responsibility for misinterpretation of the recommendations
presented in this report.
10.0 PRE-BID CONFERENCE
It may be desirable to hold a pre-bid conference with the owner or an authorized
representative, the Project Architect, the Project Civil Engineer, the Project Geotechnical
Engineer, and the proposed contractors present. This conference will provide continuity in
the bidding process and clarify questions relative to the grading and construction
requirements of the project.
11.0 PRE-GRADING CONFERENCE
Before the start of grading, a conference should be held with the owner or an authorized
representative, the contractor, the Project Architect, the Project Civil Engineer, and the
Project Geotechnical Engineer present. The purpose of this meeting should be to clarify
questions relating to the intent of the grading recommendations and to verify that the
project specifications comply with the recommendations of this geotechnical engineering
report. Any special grading procedures and/or difficulties proposed by the contractor can
also be discussed at that time.
EnGEN Corporation
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Project No. T1 075.GS
August 1996
Page 29
12.0 CONSTRUCTION OBSERVATIONS AND TESTING
Rough grading of the property should be performed under engineering observation and
testing performed by EnGEN Corporation. Rough grading includes, but is not limited to,
overexcavation cuts, fill placement, and excavation of temporary and permanent cut and
fill slopes. In addition, EnGEN Corporation should observe all foundation excavations.
Observations should be made before installation of concrete forms and/or reinforcing steel
to verify and/or modify the conclusions and recommendations in this report. Observations
of overexcavation cuts, fill placement, finish grading, utility or other trench backfill,
pavement subgrade and base course, retaining wall backfill, slab presaturation, or other
earthwork completed for the subject development should be performed by EnGEN
Corporation. If the observations and testing to verify site geotechnical conditions are not
performed by EnGEN Corporation, liability for the performance of the development is
limited to the actual portions of the project observed and/or tested by EnGEN
Corporation. If parties other than EnGEN Corporation are engaged to perform soils and
materials observations and testing, they must be notified that they will be required to
assume complete responsibility for the geotechnical aspects of the project by concurring
with the recommendations in this report or providing alternative recommendations.
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Neither the presence of the Geotechnical Engineer and/or his field representative, nor the
field observations and testing, shall excuse the contractor in any way for defects
discovered in the contractor's work. The Geotechnical Engineer and/or his representative
shall not be responsible for job or project safety. Job or project safety shall be the sole
responsibility of the contractor.
EnGEN Corpor2.tion
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Project No. T1075-GS
August 1996
Page 30
CLOSURE
This report has been prepared for use by the parties or project named or described in this
document. It mayor may not contain sufficient information for other parties or purposes.
In the event that changes in the assumed nature, design, or location of the proposed
development as described in this report are planned, the conclusions and
recommendations contained in this report will not be considered valid unless the changes
are reviewed and the conclusions and recommendations of this report modified or verified
in writing. This study was conducted in general accordance with the applicable standards
of our profession and the accepted geotechnical engineering principles and practices at
the time this report was prepared. No other warranty, implied or expressed beyond the
representations of this report, is made. Although every effort has been made to obtain
information regarding the geotechnical and subsurface conditions of the site, limitations
exist with respect to the knowledge of unknown regional or localized off-site conditions
which may have an impact at the site. The recommendations presented in this report are
valid as of the date of the report. However, changes in the conditions of a property can
occur with the passage of time, whether they are due to natural processes or to the works
of man on this and/or adjacent properties. If conditions are observed or information
becomes available during the design and construction process which are not refiected in
this report, EnGEN Corporation should be notified so that supplemental evaluations can
be performed and the conclusions and recommendations presented in this report can be
modified or verified in writing. This report is not intended for use as a bid document. Any
person or company using this report for bidding or construction purposes should perform
such independent studies and explorations as he deems necessary to satisfy himself as to
the surface and subsurface conditions to be encountered and the procedures to be used
in the performance of the work on this project. Changes in applicable or appropriate
EnGEN Corporation
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standards of care or practice occur, whether they result from legislation or the broadening
of knowledge and experience. Accordingly, the conclusions and recommendations
presented in this report may be invalidated, wholly or in part, by changes outside the
control of EnGEN Corporation which occur in the future.
Thank you for the opportunity to provide our services. If we can be of further service or you
should have questions regarding this report, please contact this office at your convenience.
Respectfully submitted,
EnGEN Corporation
Thomas E. Dewey, CE~
Project Engineering Geologist
Exp. 11-30-97
H. Wayne
President
Exp. 06-30-97
TED/OB/df
Distribution: (4) Addressee
FILE: D:\ENGEN\ REPORTS\GS\T1075GS
?ft.
EnGEN Corporation
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APPENDIX
TECHNICAL REFERENCES
Westside City Associates I, LLC
Project No, T1075-GS
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Project No. T1075-GS
TECHNICAL REFERENCES
1.
Allen, C.R, and others, 1965, Relationship between seismicity and geologic structure in the southern
California region: Bulletin of the Seismoiogical Society of America, v. 55, no. 4, p. 753-797.
2.
Califomia Division of Mines and Geology, 1954, Geology of southern Califomia, Bulletin 170.
3.
California Division of Mines and Geology, 1969, Geologic map of California, San Bernardino Sheet,
Scale 1 :250,000.
Department of Conservation, Geology map of the Santa Ana 1 :100,000 Quadrangle, California,
Division of Mines and Geology Open File Report 91-17.
5.
Tb, T.W, Jr., 1970, Regional geologic map of San Andreas and related faults in eastern San Gabriel
Mountains and vicinity: U.S. Geologic Society, Open-File Map, Scale 1:125,000.
Engel, R, 1959, Geology of the Lake Elsinore Quadrangle, California: California Division of Mines
and Geology, Bulletin 146.
Envicom Corporation, 1976, Seismic safety and safety elements, Technical report for County of
Riverside Planning Department.
Hart, E. W., 1992, Fault-rupture hazard zones in California: California Division of Mines and
Geology, Department of Conservation, Special Publication 42, 9 p.
Hileman, JA, Allen, C.R and Nordquist, J.M., 1973, Seismicity of the southern California region, 1
January 1932 to 31 December 1972: Seismological Laboratory, California Institute of Technology.
Housner, G.W, 1969, Earthquake Engineering, Weigel, R L. (ed.), Prentice Hall, Inc., 1970, Chap.
4.
Jennings, C.W, 1975, Fault map of California with locations of volcanoes, thermal springs and
thermal wells, 1 :750,000: California Division of Mines and Geology, Geologic Data Map No.1.
Jennings, CW., 1985, An explanatory text to accompany the 1:750,000 scale fault and geologic
maps of California: California Division of Mines and Geology, Bulletin 201, 197p., 2 plates.
Kennedy, M.P., 1977, Recency and character of faulting along the Elsinore fault zone in southern
Riverside County, California: California Division of Mines and Geology, Special Report 131,12 p., 1
plate, scale 1 :24,000.
Lamar, D.L., Merifield, P.M. and Proctor, RJ., 1973, Earthquake Recurrence Interval on Major
Faults in Southern California, in Moran, Douglas E., et. ai, 1973, Geology, Seismicity &
Environmental Impact, Association of Engineering Geology, Special Publication.
Leeds, D.J., 1973, Geology, Seismicity & Environmental Impact, Association of Engineering
Geology, Special Publication.
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Wests ide City Associates I, LLC
Project No. T1 075-GS
TECHNICAL REFERENCES (Con!.)
16.
Mann, J.F., Jr., October 1955, Geology of a portion of the Elsinore fault zone, California: State of
California, Department of Natural Resources, Division of Mines, Special Report 43.
17.
Ploessel, M.R. and Slosson, J.E., 1974, Repeatabie High Ground Accelerations from Earthquakes:
Important Design Criteria, California Division of Mines and Geology, California Geology, Vol. 17, No.
9, pp 195-199.
Riverside County Planning Department, June 1982 (Revised December 1983), Riverside County
Comprehensive General Plan - Dam Inundation Areas - 100 Year Flood Plains - Area Drainage
Plan, Scale 1 Inch = 2 Miles.
Riverside County Planning Department, January 1983, Riverside County Comprehensive General
Plan - County Seismic Hazards Map, Scale 1 Inch = 2 Miles.
Riverside County Planning Department, February 1983, Seismic - Geologic Maps, Murrieta -
Rancho California Area, Sheet 146, Sheet 147 (Revised 11-87), Sheet 854B (Revised 11-87), and
Sheet 854A (revised 11-87), Scale 1" = 800'.
Rogers, T.H., 1966, Geologic Map of California, Olaf P. Jenkins Edition, Santa Ana Sheet, CDMG.
Schnabel, P.B. and Seed, H.B., 1972, Accelerations in rock for earthquakes in the western United
States: College of Engineering, University of California, Berkeley, Earthquake Engineering Research
Center, Report No. EERC 72-2.
Seed, H.B. and Idriss, I.M., 1970, A simplified procedure for evaluating soil liquefaction potential:
College of Engineering, University of Califomia, Berkeley.
Seed, H.B. and Idriss, I.M., 1982, Ground motions and soil liquefaction during earthquakes:
Earthquake Engineering Research Institute, Volume 5 of a Series Titled Engineering Monographs on
Earthquake Criteria, Structural Design, and Strong Motion Records.
State of California, January 1, 1980, Special Studies Zones, Elsinore Quadrangle, Revised Official
Map, Scale 1" = 2 Mi.
State of California Department of Water Resources, Water Wells and Springs in the Western Part of
the Upper Santa Margarita River Watershed, Bulletin No. 91-21.
Uniform Building Code (UBC), 1991 Edition.
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Project No. T1075-GS
EXPLORATORY BORING LOG SUMMARIES
(B-1 through B-6)
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LABORATORY TEST RESULTS
Wests ide City Associates I, LLC
Project No. T1075-GS
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Project No. T1075-GS
DRAWINGS
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