403, Construct a new SFR with garag, Studies & ReportsWestern Laboratories
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V V Soil and Foundation Engineering A McLaren Company
August 8, 1989 Work Order 89-576
Mr. & Mrs. Steve M. Calhoun
c/o Richard M. Linde & Associates, Inc.
2200 Amapola Court, Suite 200
Torrance, California 90501
Re: Soils and Geological Investigation - Proposed
Single Family Residence - Located at 2864
Palos Verdes Drive North, in the City of
Rolling Hills, California
Legal: Lot 992-A, Tract 28146, Los Angeles
County, California
Dear Mr. & Mrs. Calhoun:
At your request, a soils and geologic investigation was
performed at the above reference. The investigation was
performed in conjunction with Mr. •Raymond E. Eastman,
Engineering Geologist.
DESCRIPTION OF SITE
At the time of our investigation, the property was vacant of
any structures and it was evident that the site had recently
been disced. The site was covered with a minor growth of
vegetation and contained various trees. The property contains
a 10' wide easement for road, bridle trail and utility
purposes along the south and east property lines and a 5'
Southern California Edison easement along the west property
line. A restricted use area and area subject to flood hazard
has been noted on the site plan prepared by the architect and
should be considered during the design and construction phase
of the project. The upper portion of the property is
relatively level and is bounded by a slope which faces to the
north and west, varying in attitude from a 5 horizontal to 1
vertical to a 2 horizontal to 1 vertical slope, for a vertical
height of approximately 60 feet.
PROPOSED SITE DEVELOPMENT
It is proposed to construct a one-story over basement, single
family residence on the above referenced site. It is
anticipated that masonry block, timber and stucco will be
utilized in construction of the exterior walls of the
structure, and therefore, maximum anticipated loadings on the
order of 3 kips/lin.ft. for continuous foundations were
utilized for testing and design purposes.
22301 South Western Avenue, Suite 101, Torrance, CA 90501 (213) 782-9001 — FAX (213) 782-9113
Work Order 89-576
2
The purpose of our investigation was to explore subsurface
conditions and to develop preliminary soils engineering design
data to permit evaluation of the site with respect to the
proposed development.
FIELD EXPLORATION
Four (4) 24-inch wide exploratory test excavations were placed
at locations, as shown on the attached plan. The excavations
were logged by our Field Engineer and disturbed and
undisturbed samples were obtained for laboratory testing and
analysis. Logs are shown on Table I.
Standard Penetration Tests (SPT) were performed in the field
by driving a regulation 2 inch outside diameter split -barrel
sampler into in -situ soil to obtain a measure of the
resistance of the soil to the penetration of the sampler.
This test (ASTM D1586-84) gives the number of consecutive
blows required to drive the sampler 6 to 18 inches; its
reporting standard, however, is the extrapolated blowcount
used to drive the sampler 1.0 foot utilizing a 140 pound
hammer with a 30 inch fall. These test results (SPT
blowcounts or N-values as shown on Table I) are used
extensively in correlating and calculating the engineering
behavior of soils.
Bulk and relatively undisturbed soil samples were obtained at
depths appropriate to the investigation. The soil sampler
utilized in our investigation included a 2-3/4 inch inside
diameter drive barrel, lined with numerous 1 inch brass rings.
The central portion of these ring samples were retained for
testing. All samples were immediately sealed in airtight
containers and transported to the laboratory. SPT, bulk,
remolded, and relatively undisturbed soil samples serve as the
basis for the laboratory testing and engineering conclusions
contained in the report.
SUBSURFACE CONDITIONS
Disturbed top soils and fill soils, ranging from 1.0 to 5.0
feet below existing grade, were encountered in the
excavations. These soils classify as silty Clay and were low
in density (soft) and low in moisture content (dry).
The natural ground, as encountered beneath the low density
soils, classified as silty Clay and was noted to be stiff.
may s s
Western Laboratories
Soil and Foundation Engineering A McLaren Company
Work Order 89-576
3
No evidence of near surface ground water was encountered in
the exploratory excavations and no caving occurred. Likewise,
no discoloration of soils, odor or tactile trace was noted
which might indicate possible contaminates or hazardous
materials.
LABORATORY TESTS
A. Direct Shear Tests (ASTM D-3080) were performed with a
strain control type shear machine where the soil samples are
subjected to a 0.002 inch per minute rate of strain, under
varying loads and under conditions of saturation. The results
of these tests are given on Plate A.
B. Expansion Index Tests, in accordance with the require-
ments of the Uniform Building Code Standard No. 29-2, were
performed on typical specimens of the on -site soils. This
test measures the expansion index of the soils from 50 percent
saturation to total saturation under a surcharge of 1.0 pound
per square inch for a 24 hour saturation period, or until the
rate of expansion becomes constant. Results of these tests
are on Table II and reveal the upper soils to be medium to
high in expansion potential.
C. Consolidation Tests (ASTM D-2435) were performed on in -
situ moisture and saturated specimens of typical soils. The
consolidometer, like the direct shear machine, is designed to
receive the specimens in the field condition. Porous stones,
placed at the top and bottom of the specimens, permit the free
flow of water into or from the specimens during testing.
Successive load increments were applied to the top of the
sample and progressive and final settlements under each
increment were recorded to an accuracy of 0.0001 inch. The
final settlements so obtained are plotted to create the
consolidation curves shown on Plate B.
D. Atterberg - Liquid Limit Tests (ASTM D-423) were
performed utilizing a mechanical liquid limit device into
which a pat of soil placed into a cup is cut by a groove of
standard dimensions which flows together at the base of the
groove for a distance of 0.5 inch when subjected to shocks
from the cup being dropped 10 mm at the rate of 2 shocks per
second. The results are secured from a minimum of three
trials, and the flow curve plotted.
___: Western Laboratories
® Soil and Foundation Engineering A McLaren Company
Work Order 89-576
4
E. Atterberg - Plastic Limit Tests (ASTM D-424) were
performed where soil is rolled into 1/8 inch diameter threads
on a piece of frosted glass. The plastic limit is defined as
the moisture content of the soil as the thread crumbles at the
specified diameter.
CONCLUSIONS
Development of the site, as proposed, is considered feasible
from a soils engineering standpoint, based on the
implementation and incorporation of the recommendations which
follow into the site preparation, grading and construction of
the proposed structure.
To satisfy the Los Angeles County Building Code, Section 309,
it can be stated that the proposed on -site building and
grading operation will not have an adverse effect on the
project site or adjacent properties, provided that it is
constructed according to the recommendations of this office.
All future certified areas of the property, as indicated in
our Supervised Compaction Report (to be submitted at the
conclusion of grading operations) will be safe from a soils
engineering standpoint from landsliding or slippage (including
surficial and gross); and proposed structures will not exhibit
excessive settlement.
Any existing or proposed slopes have not been checked for
stability.
A detailed grading plan should be submitted to this firm upon
completion as the folded nature of the Bedrock provides a
variable condition for cut slopes. It should be realized that
cut slopes that face north and west may undercut the strata
necessitating buttress or retaining wall construction.
RECOMMENDATIONS
The following recommendations are based on observations made
in the field, the results of laboratory tests on samples of
the materials encountered, the past experience of this office
and similar soils conditions in this general area, and on an
overall evaluation of the site conditions.
Western Laboratories
Soil and Foundation Engineering A McLaren Company
Work Order 89-576
- 5 -
GENERAL GRADING AND COMPACTION
All site grading operations should conform to the local
building and safety codes and to the rules and regulations of
those governmental agencies having jurisdiction over the
subject construction.
The grading contractor is responsible to notify governmental
agencies, as required, and the Soils Engineer prior to
initiating grading operations, and any time grading is resumed
after an interruption.
All vegetation should be stripped and hauled from the proposed
fill areas prior to the start of the grading operations.
In areas where subterranean removals are to be performed,
proper safety precautions should be provided and CAL -OSHA
requirements strictly adhered to.
Adequate protection shall be provided for adjacent buildings
or improvements on adjoining properties during grading
operations. Shoring may be required prior to excavation.
Any excavation without shoring should be cut at a one
horizontal to one vertical slope, to a maximum vertical height
of 15.0 feet and adequate safety protections should be
provided for any adjacent streets or structures. A visual
inspection by a representative of this firm should be
performed during the excavation; moisture variations and
differences in cohesive characteristics of the soil deposits
may require slope flattening or, conversely, permit steepening
of the cut at some locations. Temporary construction cut
slopes are suitable for short time duration, not to exceed
six weeks.
Following the excavation and haul off of soils to expose the
subterranean portion of the structure, an inspection by the
Soils Engineer shall be performed to ensure that all fill and
disturbed natural soils have been removed (i.e. in ramp area
or isolated pockets). Any remaining fill and disturbed
natural soils shall be excavated, cleansed of any debris and
recompacted to a minimum of 90 percent of the laboratory
standard, under the direction of the Soils Engineer, in
accordance with the attached "Specifications for Compacted
Fill Soils".
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V V Soil and Foundation Engineering A McLaren Company
Work Order 89-576
6
Likewise, the exposed natural ground shall be processed and
compacted in -place to a minimum of 90 percent of the
laboratory standard.
The existing low density (soft) disturbed top soils fill
soils, as noted in the attached Log of Excavations, are not
suitable in their present condition for slab, structural or
pavement support. These soils should be excavated to
competent natural ground, as verified by the Soils Engineer,
and the underlying supporting soils processed and compacted
in -place to a minimum of 90 percent of the laboratory
standard. This should also be performed in cut areas where
the natural soils are exposed. The excavated soils should
then be cleansed of any root structures and deleterious
debris, brought to proper moisture content and replaced,
utilizing compaction equipment to a minimum of 90 percent of
ASTM D-1557-78 under the direction of the Soils Engineer, in
accordance with the attached "Specifications for Compacted
Fill Soils".
Any proposed import fill soils should be approved by the Soils
Engineer prior to importing to the site. Any additional fill
soils placed should also be compacted in accordance with the
attached "Specifications".
A diligent search for septic tanks, cesspools or underground
lines should be performed during grading operations. If any
are encountered they should be excavated and backfilled under
the supervision of a qualified Soils Engineer.
All backfills should be mechanically compacted to at least 90
percent of the maximum density obtainable by the ASTM D-1557-
78 method. Jetting or flooding should not be permitted in any
trench or wall backfill.
Utility trench backfills should be observed and tested during
backfill operations as the work progresses. If the testing
of a backfill is performed after completion, without observing
the backfill operations, then only the test results at the
test locations can be given.
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V V Soil and Foundation Engineering A McLaren Company
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FOUNDATION AND STRUCTURAL
Work Order 89-576
It is not recommended that a portion of the foundation system
be founded on compacted fill soils or natural ground and a
portion on unweathered Bedrock. In this respect, as it is
proposed to excavate a subterranean basement in the structure
which will expose Bedrock, all foundations should be excavated
into unweathered Bedrock.
If the recommendations contained in this report are followed,
the proposed structure may be founded on a conventional
foundation excavated to a minimum depth of 24 inches below
lowest adjacent grade into unweathered Bedrock with a
recommended safe bearing capacity value of 2150 lbs./sq.ft.
for continuous foundations.
The allowable soil pressures may be increased one-third for
combinations of vertical and horizontal forces where permitted
by the Uniform Building Code.
It should be brought to your attention that it will be
necessary to deepen foundations into competent natural ground,
if perimeter over -excavation of the low density fill soils
(5.0 feet beyond the building perimeter), is not accomplished
due to the close proximity of the property line.
Where foundations are to be located adjacent to utility
trenches, the foundation should extend below a one horizontal
to one vertical (1:1) plane projected upward from the inside
bottom corner of the utility trench.
Due to the expansive nature of the on -site soils, it is
recommended that a minimum reinforcement of one #5 Bar, top
and bottom, be utilized in the design of continuous
foundations. A continuous foundation system is recommended
throughout the structure.
All foundation excavations should be observed by the Soils
Engineer prior to pouring concrete to ensure uniform soils
conditions, in accordance with the aforementioned
recommendations.
__ Western Laboratories
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V V Soil and Foundation Engineering A McLaren Company
Work Order 89-576
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In designing for lateral loads within the certified areas, a
coefficient of friction of 0.25 may be assumed between the
slabs -on -grade, the foundations and the unweathered Bedrock.
Unweathered Bedrock around the foundations may be assumed to
develop passive earth pressures equivalent to those pressures
exerted by a fluid having a density of 400 lbs./cu.ft. with
a maximum of 3000 lbs./sq.ft. In cases where the direction
of thrust is towards a slope and the foundation wall is less
than 5.0 feet from the face of slope, or the inclination of
the slope is steeper than a two horizontal to one vertical
(2:1), then the passive resistance should be evaluated by the
Soils Engineer.
Active earth pressures against retaining walls, placed within
the certified area, will be equivalent to the pressure exerted
by a fluid having a density of 30 lbs./cu.ft., for granular
drained soils, where the slope of the retained material is
level and there is no surcharge and the maximum height of the
retained material is 15.0 feet. Additional active pressures
are given on the attached Table IV for utilization in cases
where the slope of the retained material is not level.
Planters adjacent to building areas should be properly sealed
to prevent the influx of moisture into the building area.
This and any other appropriate measure should be taken to
minimize infiltration of surface water into the pavement
areas.
Any pool or structures to retain water should be properly
sealed to prevent the intrusion of moisture into the
underlying soils.
It is anticipated that all foundations sized for the
recommended soil pressures will experience maximum ultimate
settlements on the order of one-half inch with maximum
differential settlements not exceeding one -quarter inch.
Due to the cohesive nature of the on -site soils, the majority
of this settlement will occur over the estimated 50 year life
of the project, after construction has been completed.
Western Laboratories
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Soil and Foundation Engineering A McLaren Company
- 9 -
CONCRETE SLABS -ON -GRADE
Work Order 89-576
All slabs -on -grade should be reinforced with a minimum of #3
Bars, placed 18 inches on center in both directions, and
positioned in the center of the slab. A minimum of 4 inches
of clean Sand, or granular material should be placed beneath
the slab and the underlying soils should be moisture
conditioned to 40 percent over optimum moisture content to a
depth of 18 inches prior to pouring concrete. In addition,
a moisture barrier (6 mil black polyethylene or equivalent)
should be utilized in areas to receive sensitive floor
coverings or where floor dampness would be undesirable. The
moisture barrier should be protected during construction.
These minimum reinforcement recommendations are based upon
the expansion potential of the on -site soils only. The
Structural Engineer for the project may need to address other
factors which may require modification of the above
recommendations.
CLOSURE
The geologist should review the grading plans and make
specific recommendations for all cut or fill slopes of
significance. Grading and plot plans showing the location of
the proposed structure, all driveways, paved areas, slabs -on -
grade and pool areas should be reviewed by McLaren Western
Laboratories, prior to grading operations. The final
recommendations in this report are subject to the review of
the grading plans.
Grading operations shall be supervised by the Geologist and
Soils Engineer to insure compliance with all recommendations.
Following the completion of grading operations, a supervised
compaction report with certification will be issued by McLaren
Western Laboratories stating that the aforementioned
recommendations have been complied with during grading
operations.
r.. Western Laboratories
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V Soil and Foundation Engineering A McLaren Company
Work Order 89-576
- 10 -
Findings in this report are valid as of this date; however,
changes in conditions of a property can occur due to the
passage of time, whether they are due to natural processes or
works of man, on this or adjacent properties. In addition,
changes in applicable or appropriate standards occur whether
they result from legislation or broadening of knowledge.
Accordingly, findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this
report is subject to review after a period of one year.
The information and recommendations of this report are based
upon the assumption that the soil conditions do not deviate
from those disclosed in the excavations. If any variations
or undesirable conditions are encountered during construction,
or if the proposed construction'will differ from that planned
at the present time, McLaren Western Laboratories should be
notified so that supplemental recommendations can be given.
This report is issued with the understanding that it is the
responsibility of the owner or of his representative, to
ensure that the information and recommendations contained
herein are called to the attention of the Architect and
Engineers for the project and incorporated into the plans and
that the necessary steps are taken to see that the Contractors
and Subcontractors carry out such recommendations in the
field.
This report is subject to review by the controlling
authorities for the project.
We appreciate this opportunity to be of service to you.
Respectfully submitted,
McLAREN WESTERN LABORATORIES
Thomas C. Hare
R.G.E. 380
.=-
=NO Western Laboratories
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V V Soil and Foundation Engineering A McLaren Company
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Work Order 89-576
SPECIFICATIONS FOR COMPACTED FILL
PREPARATION
The existing fill should be removed under the observation of
the Soils Engineer to expose subgrade competent to support the
engineered fill. After the foundation for the engineered fill
has been exposed, it shall be scarified until it is uniform
and free from large clods, moisture conditioned where
necessary and compacted to not less than 90% of the maximum
dry density in accordance with ASTM D-1557-78 (5 layers - 25
blows per layer; 10 lb. hammer - 18 inch drop).
MATERIALS
On -site materials may be used for the fill, or imported fill
materials shall consist of materials approved by the Soils
Engineer, and may be obtained from the excavation of banks,
borrow pits or any other approved source. The materials used
should be free of vegetable matter and other deleterious
substances and should not contain rocks or lumps greater than
eight inches in maximum dimension.
PLACING, SPREADING AND COMPACTING FILL MATERIALS
A. The selected fill material should be placed in layers
which when compacted shall not exceed six inches in thickness.
Each layer should be spread evenly and thoroughly mixed during
the spreading to attain uniformity of material and moisture
of each layer.
B. Where the moisture content of the fill material is below
the limits specified by the Soils Engineer, water should be
added until the moisture content is satisfactory to attain
thorough bonding and thorough compaction.
C. Where the moisture content of the fill material is above
satisfactory limits, the fill materials should be aerated,
blended or dried by other methods until the moisture content
is satisfactory.
D. After each layer has been placed, mixed and spread evenly
it should be compacted to not less than 90% of the maximum dry
density in accordance with ASTM D-1557-78 (5 layers - 25 blows
per layer; 10 lb. hammer - 18 inch drop) or other density
tests which will attain equivalent results.
__:Western Laboratories
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V Soil and Foundation Engineering A McLaren Company
Work Order 89-576
-2-
Compaction should be by sheepsfoot roller, multi -wheel
pneumatic tire roller or other types of acceptable rollers.
Compaction equipment should be of such design that they will
be able to compact the fill to the specified density.
Compaction should be accomplished while the fill material
moisture content is within the compactable range. Compaction
of each layer should be accomplished by covering the entire
area and the roller should make sufficient trips to attain
desired density. The final surface of the lot areas to
receive slabs -on -grade should be rolled to a dense, smooth
surface.
E. The outside of all fill slopes should be compacted by
means of sheepsfoot rollers or other suitable equipment.
Compaction operations should be continued until the outer face
of the slope is at least 90% compacted. Compacting of the
slopes should be done progressively in increments not to
exceed 4.0 feet as the fill is brought to grade.
F. Field density tests should be made by the Soils Engineer
of the compaction of each layer of fill. Density tests should
be made at intervals not to exceed two feet of fill height
provided all layers are tested. Where the sheepsfoot rollers
are used, the soils may be disturbed to a depth of several
inches and density readings should be taken in the compacted
material below the disturbed surface. When these readings
indicate the density of any layer of fill or portion thereof
is below the required 90% density, the particular layer or
portion should be reworked until the required density has been
obtained.
OBSERVATION
Observation by the Soils Engineer should be made during all
filling and compacting operations so that he can verify that
the engineered fill was consistent, competent and in
compliance with the recommendations.
SEASONAL LIMITATIONS
No fill materials should be placed, spread or rolled during
unfavorable weather conditions. When work is interrupted by
heavy rains, fill operations should not be resumed until the
field tests by the Soils Engineer indicate that the moisture
content and density of the fill are as previously specified.
Western Laboratories
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V V Soil and Foundation Engineering A McLaren Company
13
TABLE I
LOG OF EXCAVATIONS
Test Excavation 1
Work Order 89-576
0.0 - 1.0 DISTURBED TOPSOILS - Silty CLAY (CL) -
soft, dry
1.0 - 4.0
4.0 - 5.0
5.0 - 9.0
9.0 - 10.0
10.0 - 12.0
Test Excavation 2
0.0 - 1.0
1.0 - 5.0
5.0 - 6.0
NATURAL GROUND - Silty CLAY (CL) -
Black, stiff, moist
SPT- 28 Blows @ 1.5 Feet
Silty CLAY (CL) - Brown, stiff, moist
SPT- 30 Blows @ 4.5 Feet
Bedrock TUFF - MH - Tan, hard, moist
SPT- 60 Blows @ 6.0 Feet
BENTONITE - Light Green, very stiff,
moist
Bedrock TUFF - MH - Tan, hard, moist
DISTURBED TOP SOILS - Silty CLAY (CL) -
soft, dry
NATURAL GROUND - Silty CLAY (CL) -
Black, stiff, moist
Diatomaceous Weathered Shale BEDROCK
(CL) - Tan/Brown, medium stiff,
moist
6.0 - 12.0 Sandy Bedrock TUFF - MH - with rock
fragments - Brown, hard, moist
Tao Western Laboratories
V V Soil and Foundation Engineering A McLaren Company
) I/
Test Excavation 3
0.0 - 1.0
1.0 - 6.0
6.0 - 12.0
12.0 - 13.0
13.0 - 14.0
Test Excavation 4
0.0 - 5.0
5.0 - 9.0
9.0 - 12.5
12.5 - 13.5
Work Order 89-576
TABLE I
(Continued)
DISTURBED TOP SOILS - Silty CLAY (CL)
soft, dry
NATURAL GROUND - Silty CLAY (CL)
Black, stiff, moist
Sandy SILT (ML) with rock fragments
Brown, dense, moist
SPT- 39 Blows @ 6.0 Feet
Diatomaceous Shale BEDROCK (CL)
Tan/Brown, hard, moist
Sandy Bedrock TUFF - MH - Brown, hard,
stiff
FILL SOILS - Silty CLAY (CL) with rock
fragments - soft, dry
NATURAL GROUND - Silty CLAY (CL)
Black, stiff, moist
Sandy CLAY (CL) with rock fragments
Brown, stiff, moist
BENTONITE - Green/Tan, stiff, moist
13.5 - 15.0 Sandy Bedrock TUFF - MH - Brown, hard,
moist
Western Laboratories
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V V Soil and Foundation Engineering A McLaren Company
Work Order 89-576
TABLE II
EXPANSION TESTS
Sample Classification Expansion Index
A Silty CLAY 90
B Shale BEDROCK 57
C Shale BEDROCK 64
Samples remolded to 50% saturation
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V V Soil and Foundation Engineering A McLaren Company
/40
Work Order 89-576
TABLE III
RETAINING STRUCTURES
All retaining structures should be designed
utilizing the following active pressures.
Surface Slope of Equivalent
Retained Material Fluid Weight
(Horizontal to Vertical) Lbs./Cu.Ft.*
Level 30
5 to 1 32
4 to 1 35
3 to 1 38
2 to 1 43
* These values are for drained soils to
a maximum depth of 20.0 feet and are
not inclusive of any surcharge which
should be taken into consideration in
design of the retaining structure.
•
__. Western Laboratories
Y Soil and Foundation Engineering A McLaren Company
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08-Aug-89 Work Order 89-576
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.0
Phi =
Cohesion =
R"2 =
10
4.0
3.5
3.0
S 2.5
0
1.0
0.5
0.0
2.0 3.0 4.0 0.0 1.0 7.0 3.0 40
(Thousand.)
Narmd Slaw (poi
(Thousand.
Normal Strom (pl
EXCAVATION #1 @ 4.0' EXCAVATION #2 @ 5.0'
37 deg 36.5 deg
250 psf 370 psf
0.92 0.65
Undisturbed Undisturbed
PLATE A
DIRECT SHEAR TEST DATA
Prepared for: Calhoun
auv v
Western Laboratories
V V Soil and Foundation Engineering A McLaren Company
TEST EXCAVATION 2
DEPTH
/8
J
J
0
2
3
4
5
CONSOLIDATION -%
CONSOLIDATION - PRESSURE CURVE
aAT R AEDI:D
02 025 04 05 06 08 10
DATE:
8-8-89
SCALE:
WORK ORDER:
89-576
.AT 10.0 FEE''
1
Ill I I 1
I 1
III .1
1 1
2.0 4.0
NORMAL LOAD
IN KIPS PER SQUARE FOOT
PREPARED FOR
6.0 8.0 10.0 20.0
PLATE B
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MR . & MRS . STEVE CALHOUN
22301 S. Western Avenue, Suites 101 & 102
Torrance, California 90501
1,
APPROXIMATE LOCATION OF
EXPLORATORY TESTS
= TEST EXCAVATION 0 =BORING
.ATV
s_8_ 89 STEVE M. CALH-f OUN
.ORK ORDER:
89-576
® III ►_ Western Laboratories
®0 Soil and Foundation Engineering
A McLaren Company
0
ENGINEERING GEOLOGIC INVESTIGATION
PROPOSED RESIDENCE
2864 PALOS VERDES DRIVE NORTH
ROLLING HILLS, CALIFORNIA
FOR:
WESTERN LABORATORIES
22301 S. WESTERN AVENUE, SUITE 101
TORRANCE, CALIFORNIA 90501
JULY 18, 1989
PROJECT NO: 820
" The Geologic Oust"
RAY A. EASTMAN
ENGINEERING GEOLOGIST
41111111.
"The Geologic Ou(fit"
RAY A. EASTMAN
ENGINEERING GEOLOGIST
2925 Ricker Way
(714) 630-4442 Anaheim, California 92806
July 18, 1989
Western Laboratories
22301 S. Western Avenue
Torrance, California 90501
Subject: Engineering Geologic Investigation
Proposed Residence
2864 Palos Verdes Drive North
Rolling Hills, California
Gentlemen:
Protect No.: 820
Page 1
Pursuant to your request, we have made an engineering geologic
investigation at the subject site. Purposes thereof were to identify
pertinent geologic factors with respect to proposed residential
development and to provide engineering geologic data for use in
tentative design.
The development plans are still preliminary and the discussions and
recommendations provided herein must be considered as general. It
is understood, however, that proposed development will encompass
a one or two-story, wood frame residence; the proposed foundation
system will encompass continuous footings. Also, it is assumed that
structural loads will be on the order of 1,200 pounds per lineal foot
of bearing wall. It is further understood that proposed site grading
will comprise a nominal amount of cut and fill with slopes on the
order of 10 feet in height. •
SCOPE OF WORK
The scope of work carried out was based upon the preliminary
planning information made available and was conducted in
accordance with generally accepted engineering geologic practice for
the particular circumstances. In turn, the investigation
encompassed the following points:
1) Review of available geologic maps;
2) Field geologic examination of the site;
3) Subsurface geologic examination by
exploratory pits;
4) Visual classification and evaluation of the
with respect to proposed construction; and
5) Preparation of this report.
Project No.: 820
Page 2
means
of four
units encountered
Field geologic examination was conducted at the site on July 11, 1989.
Concurrently, the exploratory pits were made by backhoe equipment
at the site at the locations shown on the accompanying geologic
map. A field geologist logged the soil and rock profile and obtained
pertinent geologic measurements of the strata.
Findings of the field geologic examination and exploratory pit
programs are presented on the accompanying geologic map, sections
and logs of test pits.
SITE CONDITIONS
The site under consideration encompasses approximately one acre of
land situated on the northern flank of the Palos Verdes Hills. It is
bounded on the west by an unnamed canyon and in general by
residential development; Palos Verdes Drive North is located at
approximately 400 feet to the north.
Topography of the site is comprised by two main features: an upper
level pad and a moderately steep, descending slope. The slope, in
turn, faces to the north and west at approximately 5:1 to 2:1 and
has a relief of approximately 60 feet.
Site vegetation is comprised by a native grasses, weeds and scattered
trees. Rainfall runoff is sheet flow towards the canyon and erosion
has not been a serious factor at the site.
An overview of the site and its topography is also shown on the
accompanying base maps.
Project No.: 820
Page 3
GEOLOGIC CONDITIONS
Geology at the site is encompassed by three basic units: namely, fill,
colluvium and sedimentary bedrock. An overview of the geology is
also shown by the accompanying geologic maps, sections, and logs.
The bedrock is assigned to the Altamira member of the Monterey
formation. At the site, it consists mainly of firm, gray and brown
sandy tuff with gray -tan bentonitic beds and diatomaceous shale.
The tuff proper is massive but the other beds indicate a fold that
has bedding towards the west on the west side with the reverse on
the east side; the area trend has bedding that is moderately steep
towards the northeast.
The colluvium consists mainly of two zones: an upper zone of
moderately stiff black -brown sandy clay and a lower zone of
moderately stiff, brown sandy silt to clay with numerous rock
fragments. Its thickness varies from approximately 5 to 13 feet.
The fill is present at the upper pad where it forms a slope of
approximately 5-10 feet in height. At exploratory pit no. 4, it
consists of uncompact, dark brown and gray brown sandy clay with
rock fragments.
Finally, it may also be noted that groundwater seepage was not
encountered at the time of our field work.
SEISMICITY
The nearest faults of known activity and greatest significance to the
site encompass the following:
Fault Zone
Palos Verdes
Newport -Inglewood
Santa Monica -Malibu
Whittier -Elsinore
San Fernando -Santa Susana
Sierra Madre -Cucamonga
San Cayetano
San Andreas
San Jacinto
An overview of the seismicity is
fault and epicenter maps.
Project No.: 820
Page 4
Approximate Location to Site
1 mile to northeast
8 miles to northeast
21 miles to north
23 miles to northeast
36 miles to north
36 miles to northeast
52 miles to northwest
52 miles to northeast
62 miles to east
also shown on the accompanying
CONCLUSIONS AND RECOMMENDATIONS
It is our professional opinion that proposed residential development at
the site is feasible from an engineering geologic standpoint, subject to
the more specific conclusions and recommendations presented below:
1) Geologic Stability - The site is considered to be geological stable in
as much as landslides or active faults are not known to be present.
Also, the bedrock characteristics appear to be such as to be suitable
for gross stability of the existing slopes.
2) Seismicity - Provisions of the current Uniform Building Code are
considered adequate for the anticipated site conditions.
3) Site Grading - It is anticipated that site grading can be
accomplished with conventional earth moving equipment with
moderate to very heavy ripping. It is further anticipated that
nearly all of the excavated materials will be suitable for use in
compacted fills. As should be expected, stripping of loose soils to
expose underlying competent soils and/or bedrock will be required
prior to placement of compacted fill. It is anticipated that such
stripping will be required to depths on the order of 5 to 15 feet or as
determined by the soils engineer.
Project No.: 820
Page 5
4) Proposed Cut and Fill Slopes - The folded nature of the bedrock
provides a variable condition for cut slopes and same_ will require
confirmation when a detailed grading plan is available. On a
tentative basis, it appears that cut slopes that face north and west
will undercut the strata and buttress measures and/or retaining
walls will be required. Cut slopes in the colluvium are anticipated
to be of low height and a ratio of 2:1 appears to be suitable.
Fill slopes of compacted fill are anticipated to be stable at 2:1 to
heights of at least 20 feet.
5) Expansive Soils Experience with the geologic units in the site
area indicates that these materials are expansive to some degree and
precautions are required relative thereto.
6) Soluble Sulfates - The on -site soils and bedrock are not anticipated
to be high in water soluble sulfates.
7) Foundation Criteria - Two basic considerations must be fulfilled
with respect to the engineering geologic aspects of the foundation
criteria: (1) the foundations must be safe against shear failure of the
soils or rock, and (2) post -construction settlement must be within
permissive limits.
Adequate support for compacted fills and/or building foundations is
anticipated to be provided by the bedrock, subject to the conditions
under geologic stability and cut and fill slopes. Naturally, it is
recommended that all fills and building foundations be established in
competent bedrock or compacted fill as the case may be. Also, in
addition to the usual criteria, the foundations should be setback to at
least a 1:1 projection from the base of any adjacent excavations.
8) Engineering Geologic Inspection - It is recommended that our
geologist have the opportunity to review the proposed grading and
construction plans when available in order to verify our findings as
presented in this report. Further, it is also recommended that site
inspections be made by our geologist during construction and grading
2(
Project No.: 820
Page 6
in order to verify our findings to the geologic conditions encountered.
Additional recommendations may, of course, be required if conditions
other than anticipated are found.
REMARKS
Several of the afore items also fall under the purview of the soils
engineer and may require further confirmation, laboratory testing,
analysis, and recommendations. These items include the site
grading, slope stability, expansive soils, soluble sulfates, retaining
walls, shoring and foundation design criteria.
The conclusions and recommendations expressed in this report reflect
our best evaluation of the project requirements as based upon
information obtained at the geologic exposures and exploratory pit
locations. It must be recognized, however, that evaluation of
subsurface deposits such as those present at the site is subject to the
influence of undisclosed and unforeseen variations in conditions that
may occur in intermediate, unexplored areas. It must be the
responsibility of the owner/contractor to bring to our attention any
unusual condition which may be encountered in the course of
project development.
We trust this report will t with your needs at this time.
However, please feel free contact us if you have any questions.
Respectfully submittkd,
Ray A. Eastman
CEG 423
mlc
6 copies submitted
attachments
1
Project No.: 820
Page 7
SELECTED REFERENCES
California. Division of Mines and Geology, 1976, Geology of the
Northeast Part of the Palos Verdes Hills, Los Angeles County: Map
Sheet 27.
South Bay Engineering Co., July 8, 1988, Topographic Survey of Site.
U.S. Geological Survey, 1946, Geologic Map and Sections of Palos
Verdes Hills, Los Angeles County: Professional Paper 207.
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RAY A. EASTMAN
ENGINEERING GEOLOGIST
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SEDIMENTARY ROCKS
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tune sand
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Qtc 1
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those on lowest terrace consti•
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b ; diatomite, ltmeatons, sandstone,
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1 including Miral.ate tuff bed. Tint. and
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concretion,) j
IGNEOUS ROCKS
Basalt
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" The Geologic Oust "
RAY A. EASTMAN
ENGINEERING GEOLOGIST
2/2
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" The Geologic Outfit"
RAY A. EASTMAN
ENGINEERING GEOLOGIST
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" The Geologic OuVit "
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RAY A. EASTMAN
ENGINEERING GEOLOGIST
1/2
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RAY A. EASTMAN
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AF
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Qc Colluvium
Tsh Tuff / Shale
/ Strike and Dip of Strata
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35
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"The Geologic Outfit"
RAY A. EASTMAN
ENGINEER►NG GEOLOGIST
Stratificat ion
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"The Geologic Outfit"
RAY A. EASTMAN
ENGINEERING GEOLOGIST
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- - -
- ----- - ; - - - - —
GEOLOGIC LOG - TEST P I T
Project No.: 820 Date. 7 / 1 1 /89 Pit. No.:
Equipment: Backhoe Pit Dimensions: W= 2' D = 17' L = 12'
Surface
558- Datum plan
Elevation.
Depth, ft. Description Geologic Unit
C-I
1 -4'
Loose dry die, brn sdy clay
Mod st moist black sdy clay
`:,/ frk chip
'N
Mod st damp hrn sdy clay
Firm (lamb tar} k. hrn to iff
wichert f gc.
It gr bentonite at 9-10' -
N5E288
•No seepage.
Colluvium
nitciiiiira
32
Project No.:' 9
Depth, ft.
GRAPHIC LOG — TEST PIT
Date: -- Pit No.:, 1,
Description
Scale ) _ ��-
3
GEOLOGIC LOG - TEST PIT
Project No.: 820 Date: 7/1 > /89 Pit No. 2
Equipment: Backhoe Pit Dimensions: W= n.
4 D = l 7' L = 1 4'
Surface `
Elevation:
554 Datum: plan .
Depth, ft. Description Geologic Unit
0-I
i-)
g-1.1•
v IT
Loose dry dk brn sdy clay Colluvium
Mod stiff moist black sdy clay
Mod firm moist tan & brn highly
weathered diatomaceous shale
Dense damp brn sdy buff .,//occ
rk f gs - massive
No seepage
Altamira
4 0
Project No.:
•
GRAPHIC LOG - TEST PIT
Date: — Pit No.: 0-
Description
Depth, ft.
4
1
111011•1
Scale 221,
1
Project No.:
Equipment:
Surtace
Elevation'
Depth, ft.
0-1
r -6.
6 - 1 ')'
1 2-1.a'
820
Backhoe
556'
GEOLOGIC LOG - TEST P I T
Date: 7/ 1 1 /89 Pit No.:
z
J
Pit Dimensions: W= D = 17' L = 14'
Datum. plan
Description Geologic Unit
I oose dry dk brn sdy clay w/rk Colluvium
fgs
Mod stiff moist dk brn sdy clay
Mod V stiff b 1 moist V 1 r/ V I I\ brn 1 1 V 4 }' clay
I
*, /rk fgs
Mon stiff damp brn sdy silt
w/numerous rk fgs
Firm darnp gr , tan
diatomaceous shale w/chert
here - N50F3ON
Dense damp brn sdy tuff -
massive
No seepage
Altam i ra
GRAPHIC LCG - TEST PIT
Project No.:' Date: ---
Pit No.: 3
1
1 i
! I ,
,
, 1
1 1 ,
11
, !
1 1
11 I I
•--1.---Z ! 1 _ ... • _i ___t. ___...- _1 i
, 1
11 i
I ,
1 ,
- .--------- . -- -1----t- -4- i 1 1 1
1 1
I 1 I 1 i 1 1 i
1 i
I 1 I 1 I I
) I 1
GEOLOGIC LOG - TEST P I T
Project No.: 820 Date. 7/1 1 /89 Pit No: 4
Equipment; Backhoe Pit Dimensions: W= D = 17. L = 15'
Surface 575' Datum. plan
Elevation.
Death, ft Description Geologic Unit
� J-5'
5-9'
i- I
1 i') C,- 1 7 C�
I L,J I J.J
i
Uncomp damp dk brn w/gr brn Fill
sdy clay w/rk fgs
Stiff moist black sdy clay
Stiff moist brn sdy clay
w/numerous rk fgs
Mod firm moist gr & tan
hentonite - N 1 OE7ON
Dense damp brn sdy tuff -
massive
No seepage
ColluvIUPI
Alta� ia..
rnira
Project No.:'
Depth, ft.
GRAPHIC LOG - 'TEST PIT
Date: —
Description
-7/
Pit No.: I/
Scale )
LJ