HomeMy WebLinkAboutGeotechnicalInvestigation(Jan.18,1989) (2). ~ Converse Consultants Inland Empire Consulting Engineers ~~/32
and Geologists
630 Eas~ Brier Drive, Suite 100 ~
San Bemardino. Calitomia 92a08
Telephone 774 /889~8004
FAX 714 889~4830
~~
`~
GEOTECHNICAL INVESTIGATION
TENTATIVE TRACT 24132
PLANNING AREAS 30, 31 and 32
PORTION OF THE MEADOWS
RANCHO CALIFORNIA, CALIFORNIA
PREPARED FOR
Rancho California Development Company
Post Office Box 755
28250 Ynez Road
Rancho California, California 92390
CCIE Project No. 88-81-148-O1-G
January 18, 1989
A Wholly Ownetl Su~sidiary ol '
Tne Converse Protess~onai Gro~p
Converse Consultants Inland Empire
Consulting Engineers
and Geologists
630 Eas~ Brier Drive, Suite 100
San Bemartlino. Calitornia 92408
Telephone 714 /889~8004
FAX 7~4 889~4830
~
January 18, 1989
Rancho California Development Company
Post Office Box 755
28250 Ynez Road
Rancho California, California 92390
Attention: Mr. Csaba F. Ko
Subject: GEOTECHNICAL INVESTIGATION
Tentative Tract 24132
Planning Areas 30, 31 and 32
Western Portion of "The Meadows"
Rancho California, California
CCIE Project No. 88-81-148-O1-G
Gentlemen:
Enclosed are the findings of our geotechnical investigation
performed for Planriing Areas 30, 31 and 32 which are a portion of
The Meadows Master Planned Community in Rancho California,
California. A preliminary "Slope Stability Analysis" letter dated
December 5, 1988 was written for this tract to expedite the County
submittal process.
Subsurface materials encountered in the exploratory excavations
generally consisted of loose to medium dense granular sediments
and soft sandstone bedrock of the Pauba Formation. Groundwater
was not encountered in the exploratory borings within this tract.
Results of our investigation indicate that the site is suitable
for the proposed residential development, provided that the
recommendations contained herein are incorporated into final
development plans. Development of the tract will involve
conventional mass grading. Anticipated depths of overexcavation
in proposed fill areas are indicated on the enclosed maps and
Z
A Whplly Ownetl Suus~tliary of
The Converse Pro(essronai Gmup
~ ~
Rancho California Development Company
CCIE Project No. 88-81-148-O1-G
January 18, 1989
Page 2
discussed in the appropriate sections of this report. Con-
ventional 2:1 (horizontal to vertical) cut and fill slopes are
proposed, with structure setbacks as recommended herein. Spread
footings may be used to support the proposed residential
structures.
We appreciate this opportunity to be of service. If you have
any questions, please feel free to contact the undersigned or
Mr. David Simon.
Very truly yours,
C VERSE CONSULTANTS INLAND EMPIRE
RMP/DBS/TC6:88y
Dist: 5/Addressee
i/Robert Bein, William Frost and Associates
1/Dr. Roy J. Shlemon
1/Mr. Robert Dieudonne (Costain Homes)
, V v~l/l.,
Robert M. Pride, GE 697
President
~
Converse Consultanis Inland Empire
; ,
TABLE OF CONTENTS
' GEOTECHNICAL INVESTI6ATION
PORTION OF THE MEADOWS
RANCHO CALIFORNIA, CALIFORNIA
CCIE PROJECT No. 88-81-148-Oi-G
Page
1. 0 I NTRODU CT I ON . . . . . . . . . . . . . . . . . . . . . . . . 1
2.0 PROJECT DESCRIPTION . . . . . . . . . . . . . . . . . . . . 3
2.1 Existing Site Conditions . . . . . . . . . . . . . . . 3
2.2 Proposed Development . . . . . . . . . . . . . . . . . 3
3.0 SCOPE OF INVESTIGATION . . . . . . . . . . . . . . . . . . . 5
3.1 Site Reconnaissance . . . . . . . . . . . . . . . . . . 5
3.2 Field Exploration . . . . . . . . . . . . . . . . . . . 5
3.3 Laboratory Testing . . . . . . . . . . . . . . 5
3.4 Research, Analyses and Report . . . . . . . . . . . . . 6
4.0 SITE GEOLOGY . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Earth Materials. . . . . . . . . . 7
4.1.1 Pauba formation (Map Symbol Qp) . . . . . . . 7
4.1.2 Terrace Oeposits (Map Symbol Qt). . . . . . . . 7
4.1.3 Colluvium (Map Symbol Qcol) . . . . . . . . 8
4.1.4 Recent Alluvium (Map Symbol Qal). . . . . . . . 8
4.1.5 Topsoi 1 . . . . . . . . . . . . . . . . . . . . 8
4.2 Groundwater. . . . . . . . . . . . . . . . . 8
4.3 Faulting and Seismicity . . . . . . . . . . . . . . . . 8
4.4 Subsurface Variations . . . . . . . . . . . . . . . . . 10
5.0 CONCLUSIONS AND TRACT DEVELOPMENT CONSIDERATIONS. ..... 11
6.0 EARTHWORK/SITE GRADING RECOMMENDATIONS. . . . . . . . . . . 12
6.1 General. . . . . . . . . . . . . . . . . . . . . 12
6.2 Removals/Overexcavation . . . . . . . . . . . . . . . . 12
6.3 Subdrains. . . . . . . . . . . . . . . . . . . . 13
6.4 Permanent Cut Slopes . . . . . . . . . . . . . . . . . 14
6.5 Permanent Fill Slopes. . . . . . . . . . . . . . . 14
6.6 Temporary Sloped Excavations . . . . . . . . . . . . . 15
6.7 Utility Trench Backfill . . . . . . . . . . . . . . . . 15
6.8 Shrinkage and Subsidence . . . . . . . . . . . . . . . 16
6.9 Site Drainage. . . . . . . . . . . . . . . . . . 16
6.10 Slope Protection and Maintenance . . . . . . . . . . 17
6.11 Asphalt Pavements. . . . . . . . . . : . . . . . . . 17
7.0 STRUCTURAL DESIGN RECOMMENDATIONS . . . . . . . . . . . . . 19
7.1 Residential foundation Design Criteria . . . . . . . . 19
7.2 School Foundation Design Criteria. . . . . . . . . 20
7.3 Slabs-on-Grade (Residential and School) . . . . . . . 21
7.4 Appurtenant Facilities . . . . . . . . . . . . . . . . 21
7.5 Corrosivity . . . . . . . . . . . . . . . . . . . . . . 22
~
Converse Consultants Inland Empire
Table of Contents
CCIE Project No. 88-81-148-01-6
~ Continued
~
8.0 GEOTECHNICAL SERVICES DURING CONSTRUCTION
9.0 CLOSURE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
REFERENCES
Drawing 1 "Geologic Map" (in pocket)
• Drawing 2"Tentative Tract Geologic Map" (in pocket)
Appendix A - Field Exploration
Appendix B- Laboratory Test Program
Appendix C- Recommended Earthwork Specifications
Appendix D - Stability Analyses
Page
23
24
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Converse Consultants Inland Empire
No. 31 96
E+o
i
Th mas C. Benson, r.
Project Engineer
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~ / avi . imon,
Senior Geologist
PROFESSIONAL REGISTRATION
For: CCIE Project No. 88-81-148-Oi-G
Dated: January 18, 1989
This report has been prepared by the
staff of Converse Consultants Inland
Empire under the professional direction
of the Senior Geologist and Project
Engineer whose seals and signatures
appear hereon.
The findings, recommendations, speci-
fications or professional opinions are
presented, within the limits prescribed
by the client, after being prepared in
accordance with generally accepted
professional engineering and engineer-
ing geologic practice. There is no
other warranty, either express or
implied.
~
Converse ConsuHantslnland Empire
. ,
1.0 INTRODUCTION
~ This report presents the findings of our geotechnical investigation applicable
to tentative tract 24132 which is a portion of the western 707 acres that
' comprise The Meadows Master Planned Community at Rancho California. The 707
acres are located south of Pauba Road, north of California State Highway 79,
east of Margarita Road and west of proposed Buecking Parkway. Tentative Tract
24132 encompasses approximately 90.2 acres of The Meadows project as shown on
the site Location Map, Figure 1.
The purpose of this investigation was to evaluate subsurface cor.ditions and
pertinent engineering properties of the encountered materials such that
recommendations regarding general site grading, slope stability and
preliminary foundation design criteria can be provided for submittal of eight
Tentative Tract Maps to the County of Riverside. Converse Consultants Inland
Empire (CCIE) performed a concurrent investigation to evaluate the lique-
faction potential at the southerly portion of The Meadows (Converse, 1988).
It is our understanding that the subject tract will be developed according to
Specific Plan 219, The Meadows at Rancho California, dated September 6, 1988.
We understand that the proposed development of~"The Meadows" will consist of a
combination of residential, commercial, schools, a neighborhood park, Day Care
Center, greenbelt areas and an extensive circulation road network within the
comprehensive plan. Development of Vesting Tentative Tract Map 24132,
addressed herein will consist of residential structures and two school sites.
Pertinent geologic and geotechnicat data generated from this investigation of
the western portion of The Meadows project together with the location of
explorations are shown on Drawing 1, titled "Geologic Map" (pocket).
1
Converse Consultanis Iniand Empire
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REFERENCE:
Alquist-Priolo Special Studies Zone Map, Pechanga
Q~adrangle, California Division of Mines and
Geology, January 1, 1980, and USGS "Bachelor
Mountain" 7.5 minute Quadrangle, 1953,
photorevised 1973
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SCALE IN FEET
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SITE LOCATION MAP
WESTERN PORTION OF "THE MEADOWS" Pro~ectNO.
Rancho California~ California 88-81-148-O1-G
for: Rancho California Development Gompany
Converse Consultants Iniand Empire
_~.
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Figure No. ~
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~ 2.0 PROJECT DESCRIPTION
2.1 Existinq Site Conditions
Tentative Tract 24132 is located in the northeast corner of the western
portion of The Meadows Development. The approximately 90.2-acre site is
bounded on the north by Pauba Road, on the east by proposed Buecking Parkway,
on the south by undeveloped land scheduled to become Tentative Tracts 24131
and 24133, and on the west by undeveloped land scheduled to become Tentative
Tract 24134. Currently, the site is characterized by several east-west
trending ridges (hills), with intermittent drainages. In general, the site
topography slopes down both to the north and south with as much as 137 feet of
relief across the site. Site elevations range from approximately 1,325 feet
(lot 90), to elevation 1,188 feet (lot 222). Vegetation consists of a
moderate growth of weeds, shrubs, and grasses. Occasional unimproved roads
and barbed wire fences traverse the site. In general, the site is in a native
undeveloped state.
2.2 Proposed Development
Based upon Tentative Tract Map 24132, provided by Robert Bein, William Frost
and Associates, dated ~anuary 3, 1989, (scale 1" = 200'), site earthwork,
exciusive of any potential overexcavations, is anticipated to consist of cuts
on the order of 77 feet (lot 90) and fills on the order of 40 feet in
thickness (lot 223). This map was used as the base map for Drawing 2,
Tentative Tract 6eologic Map (pocket).
As depicted on Drawing 2, 221 residential lots are proposed. A 10-acre parcel
(lot 222), at the northwest corner of the tract has been desiynated as the
site of an elementary school. A Junior High School site is proposed for an
18.7 acre parcel (lot 223) located at the southeast portion of the tract.
Slopes as much as 30 feet in height are proposed. No retaining walls are
anticipated. For the purposes of this report, it is assumed that the
residential structures will consist of one to two-story wood frame single
family homes. School structures are anticipated to consist of masonry,
~
88-81-148-O1-G g
Converse Consultants inland Empire
concrete "tilt-up", or wood frame and stucco one to two-story structures, with
steel and/or wood frame roof systems. School structure loads are not expected
to exceed 5 kips per foot of wall, or 100 kips per column. All of the
proposed buildings are assumed to have concrete slabs-on-grade, without
basements.
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88-81-148-O1-G 4
Converse Consultants Inland Empire
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9
3.0 SCOPE OF INVESTIGATION
3.1 Site Reconnaissance
A CCIE geologist performed a site reconnaissance of the property for mapping
of geologic units and pertinent surficial features (Drawings 1 and 2). Aerial
photographs of the site vicinity were examined stereoscopically to assist the
geolooic reconnaissance. A set of aerial photographs (flown in 1983) was
obtained from Riverside County Flood Control District.
3.2 Field Exploration
A total of 23 exploratory borinqs and 55 exploratory trenches were excavated
within the 707 acres that comprise the western portion of The Meadows.
Borings were drilled using a bucket auger drill rig and the trenches were
excavated using a rubber-tired backhoe. All excavations were visually logged
by our field personnel who carefully described the materials encountered.
Selected borings were entered by a CCIE geologist who carefully observed and
documented the exposed materials.
Relatively undisturbed and bulk samples of representative materials
encountered were obtained from the borings. A description of the field
exploration and sampiing program are presented in Appendix A, Field
Exploration Program.
Approximate locations of the subsurface explorations for the 707-acre western
portion of The Meadows project are shown on Drawing 1. Approximate locations
of the exploratory borings and trenches within Tentative Tract 24132, as well
as exploratory excavations within immediately adjacer.t tracts utilized for
this analysis of Tentative Tract 24132, are shown on Drawing 2.
3.3 Laboratory Testing
Samples were tested in the laboratory to aid in the classification and to
determine certain engineering properties of the site soils and bedrock. These
tests include:
• in-situ dry unit weight and moisture content;
s maximum density and optimum moisture curves;
~~
88-H1-148-O1-G
Conve~se ConsuNants Inland Empire
5
~ • direct shear tests;
< o moisture sensitivity (collapse) tests;
s consolidation tests;
' e R-value test; ar,d
o pH, resistivity, and soluble sulfate and chloride testino.
A description of the laboratory test methods and test results are presented in
Appendix B, Laboratory Test Program. Moisture and density data are presented
on the boring summary sheets of Appendix A.
3.4 Research, Analyses and Report
In addition to pertinent published geologic literature concerning rock units
of the area, unpublished geotechnical reports were also reviewed, particularly
those of Pacific Soils En9ineering, Inc. (1987a, 1987b, 1987c) and Shlemon
(1987). Pertinent publications reviewed for this investigation are included
in the list of references.
This report was written to present the findinas of this geotechnical investi-
gation for the tentative tract, and to provide recommendations for the
proposed development. Based upon the field and laboratory findings, slope
stability analyses were performed, as presented in Appendix D, Stability
Analysis.
88-81-148-01-6 6
Converse Consultants Inland Empire
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~ 4.0 SITE 6EOLOGY
' A general description of the subsurface conditions and various materials
. encourtered at the site during field exploration is presented in this section.
Also, a discussion of site specific geologic hazards is.presented below.
4.1 Earth Materials
The site is underlain by bedrock materials of the Pauba Formation, terrace
deposits, coiluvium, and alluvium. These, in turn, are locally mantled by a
thin veneer of topsoil. Areal distribution of the earth materials is shown on
the geologic maps (Drawings 1 and 2), and these materials are described below
from geologically oldest to youngest.
4.1.1 Pauba Formation (Map Symbol Qp): The Pauba Formation of late-
Pleistocene age (Kennedy, 1977) underlies the site. In general, the
formation consists of distal alluvial fan and braided channel deposits,
with numerous intra-formation unconformities. Sedimentary features
characteristic of the depositional environment such as channel lag, scour
and fill and cross-bedding were observed in trench and boring exposures.
Within the subject site, lithology of the Pauba Formation is highly
variable, consisting of poorly interbedded to massive, moderately to well
consolidated, fine to coarse sandstones. The sandstones are alluvial
channel-type deposits with lenses of gravelly sandstone, siltstone and
silty claystone.
Bedrock structure within the Pauba Formation can vary over a relatively
short distance. Bedding attitudes recorded at the site indicate strikes
being roughly east-west, with dips to the south at 5° to 10°. Numerous
horizontal and gradational bedding boundaries were also observed.
4.1.2 Terrace Deposits (Map Symbol Qt): Terrace deposits of Quaternary
age (Kennedy, 1977) crop out as an isolated remnant within the northeast
corner of the property, capping the top of a hill (see Drawings 1 and 2).
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Converse Consultants Inland Empire
; The terrace deposits consist of coarse sand and gravel and are slightly
porous and medium dense.
4.1.3 Colluvium (Map Symbol Qcol): Colluvial materials were encountered
at the toe of ravine slopes throughout the tract, as shown on Drawing 2.
These materials were classified as silty sand with minor amounts of sandy
silt. The colluvium was dry to slightly moist, loose to medium dense or
firm, and contained numerous rootcasts and pinhole voids. Colluvium was
encountered to a depth of 9 1/2 feet in Boring 11 at the south-central
region of the tract.
4,1.4 Recent Alluvium (Map Svmbol Qal): Recent alluvium was encountered
within the drainage channels (ravines) as shown on Drawings 1 and 2.
These materials were classified as silty sand, sand, and sandy silt. The
alluvium was dry to moist, loose to medium dense, and contained numerous
root casts and pinhole voids. Alluvium was encountered to a depth of
6 1/2 feet in Borina 13 at the northwest corner of the residential tract.
4.1.5 Topsoil: Topsoil materials mantled the majority of the site and
ranged in thickness, where observed, from 1 to 1 1/2 feet. These soils,
not differentiated on the geologic maps, consist of silty sands, are
generally loose to~medium dense and contain numerous rootcasts and
pinhole voids.
4.2 Groundwater
Groundwater was not encountered in the CCIE subsurface explorations within
Tentative Tract 24132.
4.3 Faulting and Seismicity
A site-specific fault investigation (which included 4,000 feet of fault
trenching) was performed for the 1,377 acres that comprise The Meadows project
by Pacific Soils Engineering (1987b) and Shlemon (1987). Other faults or
possible fault-related features in addition to those documented in the Pacific
Soils Engineering Investigation (1987b) were not observed during field
exploration, reconnaissance or analysis of aerial photographs.
~Qt
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Converse Consultants Iniand Empire
~ The findings of Pacific Soils Engineering (1987b) and Shlemon (1987) indicate
that the faults within The Meadows project do not displace Holocene-age (about
~ 11,000 years before present) sediments. As such, according to the California
- Divisien of Mines and Geology (CDh1G), these faults are not considered active,
and building restrictions are not mandated. However, additional studies will
be required in accordance with California Title 21, as discussed in CDMG Notes
37 and 48, for the proposed school structures. CCIE can perform these
additional studies upon request, once preliminary site layout and structural
design information are available.
In surmnary, there are no known active faults trending towards or through the
site. Also, the subject tract is not situated within a currently designated
State of California Alquist-Priolo Special Studies Zone.
During our concurrent liquefaction investigation (Converse, 1988), major
faults within a 100-km (62-mile) radius of the site were considered in regard
to generating significant ground shaking at The Meadows project. The faults
in Table 4-3 are those most likely to cause ground shaking at the site in case
of a major earthquake [Richter magnitude (hi) greater than 6.0]. Table 4-3
also summarizes important seismic characteristics for each causative fault.
TABIE 4-3
SEISMIC CHARACTERISTICS OF REGIONAL FAULTS
FAULT
Elsinore
(Wildomar Branch)
San Jacinto
Whittier
San Andreas (South)
E1 Modena
San Andreas (Central)
Peralta Hills
Sierra Madre (Cucamonqa)
HOR~ZONTAL CROUND MOTION
PARAMETERS
MINIMUM MAXIMUM* MAXIMUM P A t
SITE CREDIBLE GROUND OF STRONC
DISTANCE MACNITUDE ACCELERATION SHAKINC
(mi) EARTHOUAKE (g) (seconds)
1 1/2 7.5 0.63 25 - 35
20 7.5 0.30 23 - 32
33 7.5 0.70 21 - 30
36 7.5 0.17 20 - 25
43 6.5 0.07 5- 10
43 8.25 0.21 18 - 25
46 6.5 0.07 4- 8
59 7.0 0.08 7- 11
55 6.5 0.05 c5
* From Creensfelder (1974).
** From Seed and idriss (1982).
} From Bolt (1973).
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Cornerse ConsuHants Inland Empire
~ As is the case for most regions of Southern California, ground shaking
;
resulting from earthquakes along nearby and distant faults will occur. During
the life of the project, seismic activity associated with active faults in the
region (particularly the Elsinore, San Jacinto and San Andreas Fault Systems)
may generate moderate to strong ground shaking at the site.
The occurrences of ground acceleration during an average 100-year and 50-year
period were calculated for the site area as part of the liquefaction investi-
gation (Converse, 1988). Probable maximum horizontal ground accelerations are
0.29g once on the avera9e every 100 years and 0.23g once on the average every
50 years.
4.4 Subsurface Variations
Based on the results of our subsurface exploration and experience, variations
in the continuity and depth of subsoil and bedrock deposits shouid be antici-
pated. Due to the nature and depositional characteristics of the materials at
the site, care should be exercised in interpolating or extrapolating sub-
surface conditions between or beyond test borings and trenches. Variations in
groundwater levels can be expected due to seasonal changes, or artificial
changes such as variable regional irrigation.
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~ 5.0 CONCLUSIONS AND TRACT DEVELOPMENT CONSIDERATIONS
• The results of this investigation indicate that Tentative Tract 24132 is
- suitable for its intended usage and may be developed as planned.
As depicted on Drawing 2, lots with fill thickness of 40 feet are proposed,
and lots which transition from cut to fill are also propesed. Of geotechnical
concern for this project is the potential for differential settlement due to
the variable fill thicknesses proposed to underly the various pads. Fill
placed at depths 40 feet or more below finish grade should be compacted to at
least 95% of the ASTM D1557-78 maximum laboratory density, to reduce total and
differential settlements ir deep fill zones.
Much of the the residential distress which occurs in hillside graded lots is
due to changes in moisture in the fill mass. Therefore subdrains should be
installed as depicted or, Drawing 2. Landscape irrigation and surface drainage
should be controlled and provided such that the fill mass does not become
excessively moist or wet. Any appurtenant structures such as swimming pools,
retaining walls, grade changes and/or landscaping irrigation systems should be
designed such that these future improvements do not adversely affect the
graded lot stability or drainage. Therefore, it is stronaly recommended that
these improvements be reviewed by CCIE or an experienced Geotechnical Engineer
and/or Certified Engineering Geologist. These tract development consider-
, ations are described further in the following sections.
Design recommendations are presented below for earthwork/site grading and
structural design, for the development proposed on Drawing 2. Recommendations
for additional geotechnical services, to be performed after this report has
been approved by appropriate governing agencies, are also provided.
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3
6.0 EARTHWORK/SITE GRADIN6 RECOMMENDATIONS
- 6.1 6eneral
~ Site grading is expected to consist of cuts, removals and fill operations to
. prepare building pad areas. Cuts on the order of 77 feet (lot 90) are
proposed. Maximum fills are expected to be on the order of about 40 feet (lot
223, Junior High School site), based on site grade information as depicted on
Drawing 2. Grading is also expected to include backfill for utility trenches.
Loosely backfilled exploratory trenches located throughout the site and any
existing undocumented fill below proposed structures will reGuire over-
' excavation and recompaction prior to the placement of structural fills. See
Drawinq 1 for approximate locations of trenches and existing fill. All fill
should be placed in accordance with the recommendations presented in Appendix
C, titled "Recommended Earthwork Specifications". Structural fill should be
compacted to at least 90~ relative compaction (ASTM D1557-78), except fill
placed 40 feet or more below finish grade, fills deeper than 40 feet below
finish grade should be compacted to 95b relative compaction to reduce total
and differential fill settlements in deep fill zones.
To reduce the potential for differentiai settlement across cut/fill transition
lots, the cut portion of the lot should be overexcavated 3 feet below final
grade. A fill zone "buffer" should then be backfilled to finish grade. All
fill should be properly benched into firm and unyielding native bedrock
materials, which are expected to consist solely of the Pauba Formation. In
areas where fill is to be placed above cut slopes, the fill slope shculd be
keyed into the firm and undisturbed bedrock, as discussed in Appendix C, and
depicted on Drawing C-2, titled "Typical Fill Above Cut Slope".
Grading recommendations for removals, subdrains, permanent slopes, temporary
sloped excavations, utility trench backfill, and site drainage are presented
below. Stability calculations for the anticipated slopes are presented in
Appendix D, "Stability Analyses".
6.2 Removals/Overexcavation
All surface trash and vegetation (including, but not limited to, heavy weed
growth, trees, stumps, logs, and roots) should be removed from the areas to be
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~ graded. Organic materials resulting from the clearing and grubbing operations
L should be hauled off the site. Non-organic debris from site clearing may be
hauled off site or stockpiled for crushing and/or placement by approved
' methods in deeper fill areas.
.
P,emoval of all topsoil, and loose shallow alluvium and/or disturbed bedrock
(such•as the shallow collapsible silty sands in ravines) will be necessary
prior to placement of structural fills. Although not encountered in CCIE
explorations, any existing fill should be excavated. Recommended removal
depths are depicted on Drawing 2 in triangles adjacent to the explorations,
and discussed below:
s Ravine Areas: Removal depths will ~~ary from 1 to 10 feet, with possible
ocal~ize~ areas of deeper colluvial and alluvial removals.
• Areas to Receive Fill Outside of Ravine Areas: Removal depths will
genera y vary rom 1 to 3 eet, wit possi e ocalized areas of deeper
colluvial removals. The topsoil/slopewash may be removed by stripping,
hedvy benching during grading, or a combination of both strippino and
benching.
• Ex ~loration Trenches: All exploratory trenches were loosely backfilled
an w~ ilT require overexcavation and recompaction for new improvements
support. Approximate locations of the trenches are shown on Drawing 1.
The bottom or the excavated areas must be observed by a CCIE representative
prior to placement of new fill. Soils removed during the overexcavation
procedures may be utilized as compacted fill, provided they have been stripped
of organics and other deleterious materials. All proposed fills should be
placed on competent native materials as determined in the field by a CCIE
representative and in accordance with the specifications presented in Appendix
C, titled "Recommended Earthwork Specifications".
6.3 Subdrains
A subdrain shouid be installed within the southeastern ravine, subsequent to
alluvial removals and prior to fill placement. Discharge from subdrains
should be directed to a suitable non-erosive drainage device. If the subdrain
discharges into the stormdrain, measures should be taken to prevent stormdrain
water from backing up into the subdrain. A typical subdrain detail is
provided in Appendix C. Subdrains should generally be installed where shown
on Drawing 2, but may be modified by the project Civil Engineer and/or
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~ Certified Engineering 6eologist based upon post removal observations. All
J subdrain devices should be accurately located by the project Land Surveyor.
6.4 Permanent Cut Slopes
Permanent cut slopes less than 25 feet are anticipated (lot 72). As shown in
Appendix D, cut slopes in the encountered materials not exceeding 35 feet in
height and cut no steeper than 2:1 (horizontal:vertical) have a calculated
factor-of-safety (fS) greater than 1.5. Cut slope ratios should not be
steeper than 2:1 (horizontal:vertical). A primary concern for cut slopes on
this site is the high potential `or erosion of the sand~~ material, and the
resultant surficial instability. Structures should be set back from slopes as
shown on Figure 29-1 of the 1988 Edition of the Uniform Buildina Code (UBC).
6eologic observation of all cut slopes should be conducted during grading to
observe if any adversely oriented planes of weakness (i.e. claystone or
siltstone beds) are present. Preliminary laboratory test results indicate low
strength parameters for claystones and siltstones. Accordingly, if these
materials are exposed in proposed cut slopes during grading and are found to
be adversely oriented, buttress or stabilization fills may be required.
6.5 Permanent Fill Slopes
Proposed fill slepes should be constructed with slope ratios no steeper than
2:1 (horizontal:vertical). Fill slopes in excess of 35 feet in height are not
anticipated. Fill slopes should be properly compacted out to the slope face.
This may be achieved by either overbuilding and cutting back to the compacted
core, or other methods which meet the intent of the project specifications.
Assuming that fill slopes are properly compacted to the slope face, are graded
ro steeper than 2:1 (horizontal:vertical) and are no taller than 35 fee± in
height, the calculated factor-of-safety for compacted fill slopes is greater
than 1.5.
fill slopes higher than 30 feet (if any) should be terraced as recommended in
Section 7012 of the Uniform Building Code (1988 Edition). Structures should
be set back from graded slopes in accordance with Chapter 29 (UBC Figure 29-1)
of the Uniform Building Code (UBC). Where fill is proposed over cut slopes,
fill should be benched into the bedrock as shown on Drawing C-2, in
Appendix C.
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6.6 Temporary Sloped Excavations
The use of sloped excavations may be applicable where plan dimensions for
excavation are not constrained by property lines, existing streets, or other
structures. Where constraints exist (i.e. Pauba Road), slot-cutting,
temporary shoring or a combination of slopes and shoring will be required.
Recommendations for shoring design or slot-cutting will be presented
separately from this report, if requested. Excavations adjacent to existing
roadways should not undercut the existing embankments.
Based upon soils encountered in the
sloped temporary excavations may be
presented in the following table.
explorations, it is our opinion that
made according to the slope ratios
TEMPORARY EXCAVATION SLOPES
MARIMUM
DEPTH OF CUT MAXI~tUM S~OPE RATIO*
(ftJ (horizontal:vertical)
0- 5 vertical to 1/2:1
5- 15 3/4:1 to 1 7/4:7
75 - 50 1.5:1 to 2:1
* Selection of temporary slope ratios
should be made by the grading
contractor based on actual materiats
encountered during excavation.
Slope ratios given above are assumed to be uniform from top to toe of slope.
Sandy surfaces exposed in sloped excavations should be kept moist but not
saturated to retard ravelling and sloughing during construction. Adequate
provisions should be made to protect the slopes from erosion during periods of
rainfall. Surcharge loads should not be permitted within 10 feet of the top
of slope, or distance of at least one-third the slope height, whichever is
greater.
6.7 Utility Trench Backfill
Buried utility conduits should be bedded and backfilled around the conduit in
accordance with the project specifications. Materials may be flooded/jetted
around large-diameter pipelines, below the spring line. Care should be taken
not to move or damage utilities during compaction operations. Where conduit
underlies concrete slabs-on-grade and pavement or is adjacent to proposed
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~
3 structures, the remaining trench backfill above the conduit should be placed
and compacted in accordance with Appendix C.
6.8 Shrinkage and Subsidence
Based on our test results, shrinkage and subsidence were estimated as follows:
• Alluvium and Colluvium: Alluvium and colluvium are expected to shrink on
an average o approximately 8% by volume, with variations from negligible
to 17% shrinkage by volume at various ravine locations. Subsidence in
ravines due to earthwork activities may range up to 0.4 foot.
• Pauba (Bedrock): Shallow porous Pauba bedrock may shrink from negligible
to 17% by v-Tme when properly recompacted. An average value of 9% can
, be used for preliminary shrinkage calculations. Porous, 4ieathered Pauba
is not anticipated to be thicker than 1 to 4 feet below the bedrock
. surface. Deeper, dense Pauba bedrock is expected to shrink less and may
bulk slightly. Shrinkage ranging from negligible to 10°6 is anticipated
in most of the dense Pauba bedrock. An average shrinkage of 5% by volume
. may be used to estimate shrinkage in the deeper bedrock. Subsidence of
the exposed surface in deep cuts into the Pauba bedrock is expected to be
negligible, exclusive of wet weather earthwork disturbance.
Volume losses due to stripping of organics should be included during the
calculations of earthwork quantities. These estimates are based upon the
assumption that all removals and compaction is performed as recommended
herein. Estimates provided above should be considered preliminary. Refined
estimates can be provided by CCIE during earthwork, based on exposed
conditions, additional compaction curve data, and field density test results.
Considering the quantities of earthwork proposed, significant shrinkage
variability from ravine to ravine, and hill to hill should be anticipated.
6.9 Site Drainage
Adequate positive drainage should be provided away from structures to prevent
ponding and to reduce percolation of water into the foundation soils. A
desirable slope for surface drainage is 2% to 4% in landscaped areas and 1% to
2% in paved areas. Planters and landscaped areas adjacent to the building
perimeter should be designed to minimize water infiltration into the subgrade
soils. Gutters and downspouts should be installed on the roof, and runoff
should be directed to the street through non-erosive devices. Surface
drainage should be directed to suitable non-erosive devices. Slope drainage
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~ devices should be constructed in accordance with Chapter 70 of the Uniform
Building Code (1988 Edition). Lot drainage should preclude the possibility of
flow over slope faces, with the use of brow ditches, earth berms and oiher
' methods.
6.10 Slope Protection and Maintenance ~
Proposed slopes should be planted as soon as possible after construction.
Slopes will require maintenance through time to perform in a satisfactory
manner. In most cases, slope maintenance can be provided along with normal
care of the grounds and landscaping. Cost of maintenance is less expensive
than repair resulting from neglect.
hlost hillside lot problems are associated with water. Uncontrolled water from
• a broken pipe, excess landscape watering, or exceptionally wet weather causes
most damage. Drainage and erosion control are important aspects of slope
stability and the provisions incorporated into the graded site must not be
altered without competent professional advice.
Terrace drains and brow ditches on the slopes should be periodically
maintained ard kept clear so that water will not overflow onto the slope,
causing erosion. All subdrains should be kept open and clear of debris and
soil which could block them.
Landscaping on the slopes should disturb the soil as little as possible and
utilize drought resistant plants that require a minimum amount of landscape
irrigation. Wet spots on or around the site should be noted and brought to
the attention of the soils engineer. These may be natural seeps or an
indication of broken water or sewer lines.
Watering should be limited or stopped altogether during the rainy season when
little irrigation is required. Over-saturation of the ground can cause
subsidence within subsurface soils. Slopes should not be over-irrigated.
Ground cover and other vegetation will require moisture during the hot summer
months; but, during the wet season, irrigation can cause ground cover to pull
loose. This not only destroys the cover, but also starts serious erosion. It
is suggested to consult a professional landscape architect for planting and
irrigation recommendations.
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6.11 Asphalt Pavements
~ Asphalt pavement sections have been designed based on an R-value of 25. Final
street structural sections should be provided by CCIE based on the actual soil
conditions after grading. Based upon the CALTRANS Traffic Indexes (TIs)
• provided below, either full depth or composite asphalt and base pavement
sections may be used as tabulated below:
ASPHALT PAVEMENT SECTIONS
CALTRANS ASPHALT OVER BASE FULL DEPTH
TRAFFIC INDEX A in A PHALT in ASPHALT (in)
4 4 2 1/2 5
, 5 6 3 6 1/2
6 7 4 7 1/2
7 77 4 9
In areas to support asphaltic pavement, the subgrade should be recompacted to
a depth of at least one foot below the final subgrade as recommended in
Appendix C. At the time of placing pavements, the subgrade should be firm and
unyielding during proof rolling, and be within 2% to 3% of optimum moisture.
All base material should be compacted to a minimum of 95Y of the ASTM D1557-78
laboratory maximum dry density. Base course should consist of CALTRANS Class
II agaregate base or equivalent. Placement of full depth asphalt will reGuire
that the compacted subgrade soils provide competent support for paving
equipment. Clean cohesionless sands are subject to yielding under rubber tire
and track loads from paving equipment. The paving contractor should confirm
in writing the acceptability of the compacted subgrade prior to placement of
full depth asphalt pavement.
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7.0 STRUCTURAL DESIGN RECOMMENDATIONS
' 7.1 Residential Foundation Design Criteria
Conventional spread footings, founded in properly compacted structural fill
may be used to support the proposed residences. Footings should be set back
at least 5 feet or one-third the slope height, whichever is greater, from the
_ top-of-slope. Alternatively, footings may be embedded such that there is
adequate setback between footings and the face of slopes. In any case,
footings should have a minimum embedment of 12 and 18 inches below lowest
adjacent grade for one and two stories, respectively. Residential footings
should have a minimum width of 12 inches. Footings for one to two-story wood
' frame homes may be designed for an allowable bearing pressure of 1,500
~ pounds-per-square foot (psf). All continuous footinas should be reinforced
with at least #4 reinforcing bars top and bottom, along the full width of the
footings to mitigate the potential for differential fill settlement. Addi-
tional reinforcement may be required by the project Structural Engineer.
Structure settlement will be due to relatively light foundation loads, as v~ell
as long-term consolidatior. of fill soils and compressible native materials
below the fill. Maximum anticipated structural load induced settlements of
continuous residential footings, desiqned as recommended above, are 1/2 inch
or less. Compacted fills will settle depending on the fill thickness and
future changes in the "as-compacted" moisture conditions. Properl_y compacted
fill is expected to settle if the soils are allowed to become saturated.
These fill settlements should be considered in structural design. Some
estimated ranges of fill settlement due to saturation are tabulated below for
assumed fill thicknesses:
ESTIMATED FILL
FILL DEPTH SETTLEMENT
(ft) (in)
15 1 to 2
ZS t to 3
35 2 to 4
45 3 to 5
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~ Residential structures lateral load resistance should be designed using Table
i
29-B of the 1988 Edition of the UBC, where residences are setback as
recommended herein. Where reduced foundation setback is required, CCIE can
' evaluate specific cases and provide appropriate geotechnical criteria for
design.
' 7.2 School Foundation Desi n Criteria
At this time, CCIE is unaware of the location or type of structures to be
constructed on the two school sites (lots 222 and 223). It is therefore
recommended that, once a proposed campus layout has been chosen, a
school-specific geotechnical investigation be performed. Geotechnical studies
for schools will be required to be performed in accordance with California
~ Title 21, as discussed in CDMG Notes 37 and 48. These reports will be
reviewed by the Office of the State Architect.
For preliminary design purposes, conventional spread footings, founded in
properly compacted structural fill may be used to support one to two-story
wood frame, tilt-up, or masonry school structures. Footings should have a
minimum embedment of 18 inches below lowest adjacent grade, and should have a
minimum width of 15 inches. Footings may be designed for an allowable bearing
pressure of at least 2,000 psf, but should not exceed 3,000 psf regardless of
width or depth of embedment.
The maximum anticipated structural settlement for an isolated square footing
designed with 2,000 psf bearing and supporting an assumed load of 70 kips will
be 1/2 inch or less. Settlements of continuous footings are estimated to be
less than 1/4 inch for loads up to 4 kips per lineal foot. However,
foundation design should also consider the potential for additional fill
settlement as discussed in the sections above.
Resistance to lateral loads can be provided by friction acting at the base of
the foundations and by passive earth pressure. A coefficient of friction of
0.33 may be assumed with the dead load forces. An allowable passive earth
pressure of 270 psf per foot of depth to a maximum of 2,000 psf may be used
for the sides of footings poured against properly compacted fill soils.
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i
Vertical and lateral bearing values indicated above are for the total dead
load and frequently applied live loads. If normal code requirements are
applied for design, the above vertical bearing values may be increased by 50~
' for short duration loading which will include the effect of wind or seismic
forces. The allowable passive pressure may be increased by 33% for lateral
loading due to wind or seismic forces.
7.3 Slabs-on-Grade (Residential and School)
Conventional 4-inch minimum thickness slabs-on-grade may be constructed for
support of nominal ground floor residential and school live loads. All slab
subgrades should be moisture conditioned and compacted as recommended in
Appendix C. Care should be taken to avoid slab curling if slabs are poured in
hot weather, A mix design shouid also be provided to reduce the potential for
shrinkage cracks. Slabs should be designed and constructed as promulgated by
the Portland Cement Association (PCA). If non-expansive soils are imported
(Expansion Index less-than 30), then the Structural Engineer need not design
the slabs for expansive soils. Reinforcement should be provided as
recommended by the Structural Engineer, and may include conventional, post-
tensioned, or fiber reinforced slabs.
If a moisture-sensitive floor covering (such as vinyl tile) is used, slabs
should be protected by a 6-mil thick polyethylene vapor barrier. If the
barrier is used, it should be protected with 2 inches of sand placed above and
below to prevent punctures and to aid in the concrete cure. Vapor barrier
seams should be lapped a minimum 6 inches and sealed.
7.4 Appurtenant Facilities
It is anticipated that residential lots will be customized, including home
additions and construction of garden walls, pools, landscape ponds, retaining
walls, general regrading, and modifications of landscaping. Any of these
modifications may adversely change the foundation conditions, lot stability,
and/or adversely affect adjacent lots. It is therefore strongly recommended
that proposed lot modifications be reviewed by CCIE or an experienced
Geotechnical Engineer and/or Certified Engineering Geologist. All homeowners
should be made aware of the need for geotechnical evaluation of proposed
foundation, grading, irrigation, and/or landscaping modifications.
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~ 7.5 Corrosivity
A A bulk sample obtained from the exploration was tested for resistivity, pH,
and soluble sulfate and chloride content. Relatively low sulfate
` concentrations were measured, and therefore conventional Type I and II
portland cements may be used. Relatively high resistivity and pH and low
~ chloride content were also measured, which would indicate low corrosivity.
Some variations over this large site should be anticipated.
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~ 8.0 GEOTECHNICAL SERVICES DURING CONSTRUCTION
' This report has been prepared to aid in evaluation of the site, to prepare
. site grading recommendations, and to assist the Structural Engineer in the
. design of the proposed structures. As indicated above, additional studies may
be required for appurtenant structures. It is recommended that this office be
provided the opportunity to review the final design drawings and specifica-
tions to determine if the recommendations of this report have been properly
: implemented.
Recommendations presented herein are predicated upon the assumption that
continuous earthwork monitoring will be provided by CCIE. Removal excavation
bottoms should be observed by a CCIE representative. Structural fill and
backfill should be placed and compacted durina observation and testing by
this office. Footing excavations should be observed prior to placement of
steel and concrete to see that footings are founded on satisfactory soil and
that excavations are free of loose and disturbed materials.
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~ 9.0 CLOSURE
The findings and recommendations of this report were prepared in accordance
with generally accepted professional engineering and engineering geologic
principles and practice. Our conclusions and recommendations are based on the
results of the field and laboratory investigations, combined with an inter-
polation of subsurface conditions between and beyond exploration locations.
As the project evolves, our continued consultation and construction monitoring
should be considered an extension of our investigation services performed to
date. CCIE should review plans and specifications to check if the recom-
mendations presented herein have been appropriately interpreted, and that the
design assumptions used in this study are valid. Where significant design
changes occur, CCIE may be required to augment or modify the recommendations
presented herein. Subsurface conditions may differ in some locations from
those encountered in the explorations, and may require additional analyses
and possibly modified recommendations. This report was written for Rancho
California Development Company, and only for the proposed development
described herein. We are not responsible for technical interpretations by
others of our exploratory information which has not been described or
documented in this report. Specific questions or interpretations concerning
our findings and conclusions may require a written clarification to avoid
future misunderstandings.
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REFERENCES
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REFERENCES
BOLT, B.A., 1973; "Duration of Strong Ground Motion," Proceedings on Fifth
ti~orld Conference on Earthquake Engineering, V. 2, No. 292, p.10
CALIFORNIA DIVISION GN MINES AND GEOLOGY, 1980; "Alquist-Priolo Special
Studies Zone Map, Pechanga 7 1/2' Quadrangle".
CONVERSE CONSULTAPlTS INLAND EMPIRE, 1988; "Liquefaction Investigation, The
Meadows at Rancho California APN Nos. 926-13-9, -10, -12, -13, and -14,
Rancho California, California" (CCIE No. 88-81-148-02), dated December 9,
1488, prepared for Rancho California Development Company.
DUNCAN, J.M., and BUCHIGNANI, A.L., March 1975; "An Engineering Manual for
Slope Stability Studies", University of California, Berkeley, Department
of Civil Engineering.
6REENSFELDER, R., 1974; "Maximum Credible Rock Accelerations from Earthquakes
in California", California Division of Mines and ~eology, Map Sheet 23.
MARACHI, N.D., and DIXON, S.J., 1972; "A Method for Evaluation of Seismicity,"
Proceedings of the International Conference on Microzonation, Seattle,
Washington.
PACIFIC SOILS ENGINEERING, INC., 1987a; "Geotechnical Report for Environmental
Impact Purposes, Butterfield Hills, Rancho California, County of
Riverside, California" (WO #400082A), dated May 5, 1987, prepared for
Turrini and Brink, Planning Consultants, Irvine, California.
PACIFIC SOILS ENGINEERING~, INC., 1987b; "Fault Study, 1,400 acre, The Meadows
at Rancho California, Rancho California" (WO ~400082F), dated August 17,
1987, prepared for Bedford Properties, Rancho California, California.
PACIFIC SOILS ENGINEERING, INC., 1987c; "Evaluation of Liquefaction Potential,
A Portion of Vail Meadows Located North of Highway 79 and South of De
Portola Road, between Margarita Road and future Butterfield Stage Road,
Rancho California, California" (WO #400082A), dated September 30> 1987,
prepared for Bedford Properties, Rancho California, California.
PLOESSEL, M.R „ and SLOSSON, J.E., 1974; "Repeatable High Ground Accelerations
from Earthquakes," California Geology, September.
SHIEMON, R.J., 1987, "Fault Study, 1,400 Acre Vail Meadows Project, Rancho
California, County of Riverside, California", dated July 15, 1987,
prepared for Bedford Properties, Rancho California, California.
UNIFORM BUILDING CODE (UBC), 1988 ed., International Conferences of Building
Officials.
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DRAWINGS
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APPENDIX A
FIELD EXPLORATION
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APPENDIX A
FIELD EXPLORATION
Field exploration included a site reconnaissance and subsurface exploration
program. During the site reconnaissance, the surface conditions were noted,
and the locations of the test borings and trenches were determined. The
exploratory borings and trenches were approximately located using existing
boundary and other features as a guide. Elevations shown on the logs were
interpolated from the contours shown on the provided site topographic map.
Exploratory borings were advanced using 18, 24, and 26-inch diameter bucket
auger drilling equipment. Exploratory trenches were excavated by a backhoe
equipped with a 24-inch width bucket. Soils were continuously logged by an
experienced geologist and classified in the field by visual examination in
accordance with the Unified Soil Classification system. Where deemed appro-
priate, the exploratory borings and trenches were entered by an engineering
geologist who observed the exposed earth materials. Where appropriate, field
descriptions and classifications have been modified to reflect laboratory test
results.
Ring samples of the subsurface materials were obtained at frequent intervals
in the exploratory borings and trenches using a drive sampler (2.4-inch inside
diameter, 3-inch outside diameterj lined with sample rings. The steel ring
sampler was driven into the bottom of the borehole or trench with successive
drops of a driving weight. Successive drops of telescoping kelly drove the
samples in the bucket auger borings. The soil is retained in brass rings
(2.4 inches inside diameter, 1.0 inch in height). The central portion of the
sample was retained and carefully sealed in waterproof plastic containers for
shipment to the laboratory. Bulk samples of typical soil types were aiso
obtained. Blow counts for each sample interval are presented on the boring
logs.
Logs of the exploratory borings and trenches are presented in the boring and
trench surrmiary sheets A-1 through A-87. Boring and trench summary sheets also
include descriptions of the materials, pertinent field data and supplementary
laboratory data. A key to soil symbols and terms is presented on the key
sheet which is the last page in Appendix A.
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APPENDIX B
LABORATORY TEST PROGRAM
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APPENDIX B
LABORATORY TEST PROGRAM
Labora*ory tests were conducted in the Converse Consultants Pasadena (CCP)
laboratory on representative samples for the purpose of evaluating their
physical properties and engineering characteristics. Test results are
presented on the exploration logs and in this appendix. A surtunary of the
various laboratory tests conducted is presented below.
In-Situ Moisture Content and Dr Density
Data obtained from these tests, performed on relatively undisturbed ring
samples obtained from the field, were used to aid in the classification and
correlation of the earth materials and to provide qualitative information
regarding strength and compressibility. The percent of moisture as a
function of dry weight, and the encountered dry density in units of
pounds-per-cubic-foot (pcf) are provided in the right-hand columns on the
exploration logs.
Laboratory Maximum Density and Optimum Moisture Tests
Laboratory maximum density and optimum moisture tests were performed on
representative butk samples of the site materials. These tests were run in
accordance with the ASTM D1557-78 laboratory procedure. Laboratory maximum
density and optimum meisture curves are presented on Drawings B-1 and B-2.
Shear Tests
Direct shear tests were performed on both undisturbed ring and remolded
samples. Individual rings were prepared, soaked and vertical surcharge
applied. Each ring was then sheared at a constant rate of strain. A range of
normal loads was applied and the shear strength envelope was determined.
Results of the tests are presented on Drawings B-3 through B-8.
Collapse Tests
To evaluate the moisture sensitivity (collapsibility) of the encountered
soils, ring samples were loaded up to approximately 2 kips-per-square-foot
(ksf), allowed to stabilize under load, and then submerged. The percent of
consolidated measured after the sample was submerged is reported on the logs
in the far right column as percent collapse.
Consolidation Tests
Data obtained from this test, performed on relatively undisturbed and remolded
soil saniples, were used to evaluate the settlement characteristics o` on site
soils and remolded soils under load. This test involved loading specimens
into the test apparatus which contained porous stones tc accommodate vertical
drainage during testing. Normal vertical axial loads were applied to one end
of the sample through the porous stones, and the resulting vertical
deflections were recorded at various time periods. The load was increased
after the sample reached a reasonable state of equilibrium.
as-si-iaa-oi-c
3~
Converse Consultants Inland Empfre
B - 2
Samples were loaded at field moisture and submerged for additional loading.
Test results are shown on Drawings B-9 through B-19 entitled Consolidation
Test, including a time-rate of consolidation plot.
Resistance R-Value Test
A selected bulk soil sample was tested in a Converse Consultants laboratory to
determine the "R" value using the California "R" Value Test Method No. 301
(ASTM D 2844-69). Results of the "R" value test is presented below:
SAMPLE RESISTANCE
BORINC SAMPLE DEPTH ~~R~~
No. No. (ft) SOIL DESCRIPTION VALUE*
BH-2 B-2 10-11 SILTY SAND (SM), fine 26
* By exudation.
Corrosivity and Chemical Attack
A bulk sample was sent to an analytical laboratory to test the soil pH,
resistivity, and soluble sulfate and chloride content. These tests were
performed to evaluate the corrosivity and chemical attack potential for the
site soils. The results are as follows:
SAMPLE
BORINC DEPTH
No. (ft)
BH-3 30-37
RESISTIVITY SOLUBLE ( m)
'DESCRIPTION ~ (ohm - cm) UL A HL R
CLAYEY SILT (CL/ML) 7.9 4,290 242 158
Sample Storage
Soil samples presently stored in our laboratory will be discarded 30 days
after the date of this report unless this office receives a specific request
to retain the samples for a longer period.
~
88-81-148-O1-G
Converse ConsuNants Inland Empire
APPENDIX C
RECOMMENDED EARTHWORK SPECIFICATIONS
3°~
88-81-148-O1-G
Converse Consultants Inland Empire
APPENDIX C
RECOMMENDED EARTHWORK SPECIfICATIONS
Grading
1. Areas to receive compacted fill shall be stripped of all vegetation,
organics, debris and existing structure remnants. Any existing fill
materials shall be excavated. Any other unsuitable soils shall be
excavated as recommended by Converse Consultants Inland Empire (CCIE).
All areas that are to receive compacted fill shall be observed by CCIE
prior to placement of fill.
2. Subsequent to the removal of unsuitable materials, subgrade soil surfaces
that will receive compacted fill shall be scarified to a depth of at
least 6 inches. The scarified soil shall be moisture-conditioned to at
or slightly above optimum moisture content. Scarified soil shall be
compacted to at least a relative compaction of 90%. Relative compaction
is defined as the ratio of the inplace soil density to the laboratory
maximum dry density as determined by the ASTM D1557-78 test procedure.
3. Subdrains shall be installed in canyons and ravines as indicated by the
project Certified Engineering Geologist (CE6). Subdrains shall be
installed as depicted on the attached Drawings C-la and C-lb.
Fill shall be placed in suitable lifts, with lift thickness modified as
necessary to achieve adequate compaction. All fill soils shall be
compacted mechanically throughout to the specified density. Each layer
shall be compacted to at least a minimum relative compaction of 90%,
except fill placed 40-feet or more below final arade shall be compacted
to 95% relative compaction. Pavement base material shall be compacted to
at least 95% of the ASTM D1557-78 laboratory maximum density. Fills
shall be benched into unyielding bedrock on slopes steeper than 4:1
(horizontal:vertical). Where fill is to be placed above cut slopes,
fill shall be benched into bedrock as shown on Drawing C-2. The fieid
density of the compacted soil shall be measured by the ASTM D1556-82 or
D2922-81 test methods or equivalent.
5. Fill soils shall consist of excavated on site non-expansive soils
essentially cleaned of organic and deleterious material or imported soils
approved by CCIE. All imported fill shall be granular and non-expansive
with an Expansion Index (EI) less than 30, as defined by the Uniform
Building Code (UBC) Standard 29-2. Rocks larger than 6 inches in
diameter shall not be used unless they are sufficiently broken down.
CCIE shall evaluate and/or test import materials for conformance with
specifications prior to delivery to the site. The contractor shall
notify CCIE at least two normal working days prior to importing fill to
the site.
CCIE shall observe the placement of compacted fill and conduct inplace
field density tests on the compacted fill to check for adequate moisture
content and the required relative compaction. Where less than the
specified relative compaction is indicated, additional compactive effort
L~O
88-81-148-O1-G
Converse Consultants Inland Empire
C-2
shall be applied and the soil moisture-conditioned as necessary until the
specified relative compaction is attained. The contractor shall provide
level testing pads for the soils engineer to conduct field density tests
on. The contractor shall provide safe and timely access for CCIE
personnel throughout the grading site, to allow continued monitoring and
testing.
7. Wherever, in the opinion of the Owner's or CCIE's Representatives, an
unstable condition is being created, either by cutting or filling, the
work shall not proceed in that area until an investigation has been made
and the grading plan revised if found necessary.
Erosion Control
1. Fill and cut slopes shall be graded and landscaped to reduce
water-induced surficial erosion/sloughing. Permanent erosion control
measures shall be initiated immediately after completion of slope
construction.
2. All interceptor ditches, drainage terraces, down-drains and any other
drainage devices shall be maintained and kept clear of debris. Runoff
shall be directed to a suitable non-erosive drainage device, and shall
not flow uncontrolled offsite.
A suitable proportion of slope plantings shall have root systems which
will develop well below 3 feet, such as drought-resistant shrubs and low
trees, or equivalent. Intervening areas shall be planted with
lightweight surface plantings with shallower root systems. In any event,
lightweight, low-moisture planting shall be used.
4. Construction delays, ctimate/weather conditions, and plant growth rates
nay be such that additional short-term, nonplant erosion control measures
may be needed; including matting, netting, sprayed compounds, deep
(5 feet) staking, etc. These measures shall be reviewed by CCIE.
5. Rodent burrowing, human trespass (footprints), small concentrations Or
uncontrolled surface/subsurface water, or poor compaction of utility
trench backfill on slopes shall be repaired and controlled as soon as
possible.
6. All possible precautions shall be taken to maintain moderate, uniform
soil moisture. Slope irrigation systems shall be properly operated and
maintained, and system controls shall be placed under continued control
by a landscape architect or similar qualified person.
7. If completion of new slopes occurs during the rainy season, contingency
plans shall be developed to provide prompt temporary protection against
major erosion/sloughing. Offsite improvement shall be protected from
site runoff.
8. Any erosion damage which occurs prior to the completion of the project
shall be repaired by the Contractor.
a~
88-81-148-O1-G
Converse Consultants Inland Empire
.) • .
f
i
t
I
~ ' ' •~ ~ • ' ' PROPOSED COMPACTED FILL :. ~ ~~ ~ '
• -'• • . , , .
~ ' ~ . ' . . . , .
.~.. , . . . . , . .
~~ •'. • ..' .'... ' .• • . • .
- ,: ~\ ~ ~ -~ NATURAL GRADE : : : • • •
~ ~~~ ~ ~~ UNSUffABLE MATERWL ~
.'~i: .. • •
~ ' ' . -; - :
~. •~ ~\~~',..~ " ~~• • '~~
`\ ~~~L~~/~
• . • • •~ \ .•• .
TYPICAL BENCHING~ ~ ~ o
SEE DETAIL BELOW
NOTES:
COMPETENT MATERIAL
Pipe ahall be a minim~m of
4 inehes diameter and nna of
500 teet or mwe shell uee 8-inch
diametet DiDe~ a ea recommerded by
, the aoil erqineer
• ' • • . .
. . . ~ . . ,
.\• . •, . _ - •~ . '
" • , - MINIMUM CLEARANCE ..:~~
~ ~ . DIMENSIONS
e a O e
~ Q o O ~ ~ v
n O O O Z ~O ~ Op
e ~ od
O o .
a p N O 6 p
;
l
~~
0
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9
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Deptl1 and 68ddkq
Me
Ve
WIM o O
Q O
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Y
ry e p
e e
Plpe end LOad a e °
e
Charaeterlatlea.
' F
8' MIN.
8' MIN.
3
eet Typlcel
p o s
~
O o ~ e
z e •
o
°
~ o ° 0 0
Q O ~
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0 O 0 O 0 p
18' MIK
~ Feet TYPIC
~~ i
. ~ . ,. .
. ' ' •i~' . .
. i//!
, '~~ .
./
~ NOTE:
Downatream 20' o} pipe at outlat ehalt
De nompertorated and bsckfllled
wiM flnrprained matMal
FlLTEA MATERIAL - Mirim~m o} rine cubic
+aef ~ root or dags.. oraW~~ c-, b fa.
n~ter ma,eria~ flraaenc~
ALTERNATE In Iieu ot Niter material nine
cubk feet of flrevel par foot of pipe may Da
eneaeed in fitter fabric. Sea Drewinp C-1b
fa pravel apecHicatlonn.Fitter taDric shall
be Mirafl 140 w equivalaM. Fltter fabrle
ahell be lapped a minim~m of 12 ineAee on
all joirtta
MirtirtNm 4~nefrdiart~etx, PVC SCFL 40 or
ABS Cless SDR-35 with a auehinp strerql~
ot at leeat 100o parWe, wtth a mi~imm of
8~Y'aDeCOC pBf}OfBUOfp DBf 100I W
WPe, Mstalled wim perforatlons on Donan of
WPe.
TYPICAL CANYON SUBDRAIN
N/ESiERN PORTIO~J OF "THE 1v1EADOWS" PrqeCtNO.
Rancho California, California 88-81-148-01
for: Rancho California Development Company
Co~v~rse Consuttants Inland Empire
Drawing No. - ~n
C-ta ~~
FLTER MATERIAL•
F~TER MATERIAL
MIPL 9.CU. FT.
PER LINEAL FT.
PERFORATED P~E
6' MIN.
Flltx m~terial shell be Claas 2 pertneeble
m~terlal (Caltrsrm Standard Specificstlon
88-1.025) w approvad altemeta.~
Claae 2 padirq ae followa:
SIEVE SIZE
t'
3/4'
~g
No, 4
Na 8
No. 30
Na 60
No. soo
too
eo-ioo
ao-ioo
25-40
18-33
5-16
o-~
o-s
SUBDRAIN ALTERNATE A: Perforated Pipe Surrounded with Fitter Materiai
6' MIN. OVERLAP ~
~ I
MIRAFI 140 FILTER FABRIC o°o° o~
OR APPROVED EQUIVAIENT o. ~~ o
1-1/2' MIN. GRAVEL OR
APPROVED EQUIVALENT
NOTE:
In addNion to the wreooed R*vsl,
outlet D~on ot tha eubdrai~ shadd
- ee ea~ooed w~m a m~dn.n, a
,o raec ~«w ver+«atea ape cw.,eccea
~fn a ranPeiiorated dGe hevirq a
mirimm of 5 feet in lerqth hefda
the wrepped RaveL
SUBDRAIN ALTERNATE B: 1-1/2' Gre~el Wrapped in Fiker Fabric
o'
~
0
+
e
9
O
SUBORA?I OiSTALLATpN - ~ aln dpe ehatl be IrreffiIled wlth peAoratla~s down a, at loeatlam deei~ated by
Ul! pBOt6CMp1 COfIl1/Mfll. . ..
SUBDRAN TYPE - S~drain typ~ ehell Ds AST.1 C508 Aabeetos Ceme~N Pips UC~ a ASTM 02751. SDR 235,
a ASTM D1627, ScAed~Ae i0 AayloritrFh &Radlens Styrene (ABS) a ASTM D3034, 3DR 235, a ASTM D1785,
Sehad~e 40 Potyvirryf Chlarfds Plnatic ff'VC) pipe a the approved earvebrR
TYPICAL CANYON SUBDRAIIV (continued)
~P!ESi ERtv PORTION OF °THE ME?,C01V5" °rojci "°
Rancho California, Califomia 88-81-148-01
for: Rancho California Development Companv
Conv~~~~: ~onsultants Inland Empire
Drawing No. 1
C-15 ~~
CUT/fill COHTACT SHOWN ~ COAIPACTFD FILI
ON GtiADING PIAN . ..
i
1'I
c
0
u
0
~
i
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<
CUT,'F0.L CONTACT TO BE COMPE7ENT MATERIAI I
SNOWN ON "AS•BUILT~ ' ~ ~
. J~
I. ~ ' ~.
9'ui-1 ~/~~NSU~ZPBtEMA~R,AL_~
~ .
~ VARIABIE . _~' . I .
~ . ~E~Ov
NATURAL 6iiADE ~ • • ' MIN -
~ f f' ~• ' MINIAIUM MEIGHT OF BENCHE$
---~ , :~ ' • . ~ IS < fE[i OR A$ RECOM-
CUT SLOPE -~ MENDED BY TME SOIL ENG~•
_' NEcA .
""-.. MINIMUAt i' TILT BACK
o ~ - OA 2% SIOPE •
(WHICHEVER IS GREATEi~
CUTSLOPETOBELONSTRUC7EDPRIOR J BEDROCK Oii APPROVED
TO PUCEIAENT OF FI~L LOMP~NT MATFRIAL
KEYWAV IN COMPE'iENT MAT•
EfiIAL NINIMUM WIDTH OF 15
FprT OR A$ RECOMAIENDED
8v THE SOII ENGINEER
TYPICAL FILL ABOVE CUT SLOPE
WESTERN PORTION OF "THE MEADOWS" Pr01eGtNO.
Rancho Califorriia, California 88-81-148-O1
for~ Rancho California Develo~ment Comoanv
Converse Consultants Inland Empire
APPE~DIX D
STABILITY ANALYSES
88-81-148-O1-G
~~~
Converse Consultants inland Empire
`BY ~ DATE - ~' °' •°-- CUENT SHEET N0. ~ Of ~
i CHKD. BY _ DATE PRWECT NO. P^ '%%- ~~'% -~Ti
PROJECT r,uc M~ ~. r- •~< F~! ^: ~ ~ r ~~: cr -~:i=
SURFICIAL STABILITY CALCULATIONS
___ _ __. _ _ _
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STABIUTY CHARTS FOR INFINITc SLOPES.
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~ SMEET
Converse Consultants SIGNED ~'
~ REG. N0. D~3
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