HomeMy WebLinkAbout2838 Adeline Drive - Technical StudyP. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
671 ROCKDALE DRIVE
SAN FRANCISCO, CALIFORNIA 94127
TEL (415) 5840537 • FAX (415) 5843084
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SOIL REPORT
2836 ADELINE DRIVE
BURLINGAME
SAN MATEO, CA
P. WHITEHEAD & ASSOCIATES REPORT 2003 - 33
MARCH 11, 2003
APR - 1 2003
CITY OF
PLAPJPJING UFf, T .
CIVIL, STRUCTURAL, SOILS P. Whitsbsad, P.19. • President
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
SOIL REPORT 2003 - 33
TABLE OF CONTENTS
Page No.
INTRODUCTION.............................................................................. 1
SITECONDITIONS........................................................................ 2
SITE INVESTIGATION...................................................................2
SUBSURFACE CONDITIONS........................................................ 3
SEISMICITY.................................................................................... 3
SLIDEPOTENTIAL........................................................................4
RECOMMENDATIONS................................................................... 4
SITEDRAINAGE............................................................................ 6
DESIGN PARAMETERS.................................................................7
INVESTIGATION LIMITATIONS....................................................7
P.W. jw
Attachments:
1) Location Map
2) Boring Location Plan
3) Boring Logs
4) Laboratory Analysis
5) Soils Strength Data
6) foundation Details
7) Seismic Reaction Map
8) Excerpts from Deering's Civil Code.
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil report 2003 - 33
March 11, 2003
Page 1
Soil . report
2836 Adeline Drive
Burlingame
San Mateo, Ca
Introduction :
The report presents the results of a soil investigation for_ the proposed
2 story over garage single family dwelling structures to be constructed at
2836 Adeline Drive Burlingame San Mateo Ca. The purpose of this
investigation was to determine. the subsurface soil conditions .and to make
recommendations for the design of the foundation for the proposed
structures. The scope of the investigation included the following items:
• Drilling of three test bore holes in order to evaluate subsurface soil
Conditions
• Evaluation of Soil Classification
• Evaluation of subsurface conditions
• Evaluation of seismicity
• Evaluation of slide potential
• Presentation of the result of the investigation, including
recommendations, in a report
0 Determination of design parameters.
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil report 2003 - 33
March 11, 2003
Page 2
The investigation was carried out in conjunction the following: -
Site conditions:
The site consists of lot 11 block 5 situated in steeply to moderately
sloping terrain on the north side of Adeline Drive in Burlingame. The lot is
roughly rectangular in shape and extends an average depth of 247 feet from
the property line at Adeline Drive to the rear property line. The average width
of the lot is 110 feet. The lot initially slopes downward from the front property
line at a• slope averaging two horizontal to one vertical over a distance of 30
feet. The lot then slopes less steeply at a slope of three horizontal to one vertical
for a distance of 50 feet. The remainder of the lot is at a mild slope of six
horizontal to one vertical. The lot is vegetated with bushes grasses and
eucalyptus trees. Some minor erosion / swale were observed towards the centre
of the lot and parallel to the lot depth, reportedly runoff from Adeline Drive. The
condition has been corrected by the city with the construction of a berm at
Adeline Drive. No lateral instability of the soils was evidenced.
Slope Stability Maps prepared by the United States Government
Geological Survey Department indicate the site is located in a zone which
is classified as Category 3. Category 3 is defined as stable to moderately
stable areas that are not underlain by or immediately adjacent to landslide
deposits.
The site is not known as being in a zone of liquefaction potential.
Site investigation:
A detailed site reconnaissance and surface exploration performed
by the writer on February 24, 2003.
Three test borings were carried our to depths of 15 feet. Very stiff
clay was encountered varying in thickness from approximately four feet six
inches to eight feet below grade. Weathered sandstone bedrock was
encountered below the clay. Free water was not encountered. However,
sub -surface flows will probably occur during wetter winters. The borings
were drilled using a portable continuous flight auger. The approximate
locations of the borings are shown on the enclosed site plan. The boring
logs are included in the attachments of this report. The boring rig utilized was
provided by Access Soil Drilling Company. Sampling Penetration Resistance
Blow Counts were obtained with a split spoon sampler and a 140 pound
free falling hammer. Blow counts were taken at 5 feet and 15 feet depths.
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil Report 2003 - 33
'March 11, 2003
Page 3
Subsurface Conditions:
United Stites Department of the Interior Geological indicate that the
site is underlain by colluvium fill over sandstone bedrock. U.S.G.S. map of
San Mateo indicate the underlying rock to be Santo Clara Formation, a
conglomeration of sandstone and mudstone. The boring samples and blow
counts indicated the rock to be of medium hard properties.
Seismicity:
The San Francisco Bay Area is considered to be one of the most
seismically active regions of the United States. The nearest active faults
are the northwest trending Hayward Fault, mapped 17 miles northwest of the
site and the northwest trending San Andreas Fault, mapped approximately 3
miles southwest of the site. Referring to Borcherdt, Gibbs, and Lajois
1975, the site is located in a seismic category "D" area. It is expected
that the site. will be subjected to at least one moderate to severe
earthquake. The occurrence of fault offset through the site is possible and
violent shaking of the site and structures is to be expected. Because of
the inherent strength of the stiff subsurface material, cohesion and the
absence of near surface, water flows liquefaction :of the foundation soils is
not likely to occur.
SEISMIC ZONE SEISMIC SOURCE SOIL PROFILE NEAR SOURCE NEAR — SOURCE
TYPE TYPE FACTOR N. FACTOR Nv
4 A Sc 1.50 2.00
Slide Potential:
It is the writer's experience that slide action occurs due to the
following:
n Sloughage of surface soils off harder impermeable underlying rock.
n Slippage of surface soils at a weak subsurface material underlain by
impervious material.
n Saturation and resulting lubrication at the slide plane by surface and
subsurface water especially during periods of prolonged rainfall.
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil Report 2003 33
`March 11, 2003
Page 4
n Steep grading.
n Soft poorly compacted. native soils and fill soils.
r1 Over -excavation of the slope support toe.
The subject site is relatively steep sloped and contains some natural
overburden material. The underlying material is a weathered sandstone
material. However, no near surface water table is indicated. A potential for
creep exists. Foundations are to be of a pier and grade beam design.
All foundation excavation and grading work is to be witnessed and
approved by a Registered Engineer. Testing of the earthworks shall be
carried out as required by the Engineer and by the City. Extremely heavy
rains might cause local sloughage. Adequate drainage facilities will help
minimize such.
Recommendations:
Foundations:
Foundations for the proposed buildings should be of a drilled pier
and grade beam design penetrating into the underlying sandstone bedrock
material a minimum of 8 feet. The piers should be tied with well
reinforced grade beams spanning between the piers. Expected pier depth
is 18 feet piers are to be a minimum of 16" diameter.
In order to resist any creep movement the piers are to be designed
to resist a lateral active pressure of 50 P.C.F. acting on the top five feet
of the pier. Passive resistance shall be considered as acting over twice
the diameter of the pier.
Expected settlement under normal conditions is not anticipated to
exceed one inch in fifty feet.
Retaining: Walls:
Retaining walls located on the site must be designed to resist lateral
earth pressure plus additional lateral pressures that may be caused by
surcharge loads applied at the ground surface behind the walls.
P. WHITEHEAD AND ASSOCIATES
CONSUINTINB ENGINEERS
Soil report 2003 - 33
`March 11, 2003
Page 5
It is recommended that unrestrained walls, 12 feet in height, or less
that have a level surface or a sloping surface flatter than 4:1, be
designed to resist an equivalent fluid pressure of 40 pounds per cubic
foot. Where the sloping surface is at an inclination of 2:1, the walls be
designed to resist an equivalent fluid pressure of 60 pounds per cubic
foot. For walls having a sloping surface between 4:1, and 2:1, a straight
line interpolation between 40 and 60 pounds per cubic foot may be used.
The walls should also be designed to resist an additional uniform pressure
equivalent to one-third the maximum anticipated surcharge load applied at
the surface behind the walls. The above pressure assume that sufficient
drainage will be provided behind the walls to prevent the buildup of
.hydrostatic pressures from surface and subsurface water infiltration.
Adequate drainage should be provided by a sub -drain system consisting of
a four inch diameter perforated pipe (AES slotted ) bedded in drain rock
wrapped effectively with filter fabric to a height of two-thirds the height of
the wall. The remaining portion of the walls should be back -filled with on -
site or imported fill materials that are compacted to at least 90 percent
relative compaction. Building retaining walls should be water -proofed by a
positive method such as hot -mopping.
Retaining Wall Lateral Loads:
Lateral loads may be resisted by passive pressure against the piers.
On slopes the piers must have at least. five feet of " dense " soils
between the slopes face and the " theoretical piers top " to develop the
recommended passive pressure. Values are tabulated under " Design
Parameters ". Lateral bearing ( passive pressure) may be considered as
acting over 2 times the pier diameter. It is recommended that the factor
of safety against sliding and overturning for retaining walls be at least 1.5.
Site preparation earthwork operation:
The site should be stripped to . sufficient dept to remove surface
vegetation, bushes and trees. All cleared and stripped materials should be
removed from site.
After the site has been properly cleared and stripped, excavation
required for the proposed structure should commence. These excavation
operations are to be performed during the dry months of the year to
avoid potential problems that can occur during periods of prolonged
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil report 2003 - 33
`March 11, 2003
Page 6
rainfall. During the excavation operations, temporary cut slopes and/or
temporary shoring should be used as required to prevent the movement of
materials exposed in the face of the excavations. The need for temporary
shoring should be carefully analyzed along all portions of the property
:lines adjacent to existing driveway, buildings, and retaining walls. An
excerpt from Deering's Civil Code is included in the attachments of this
report.
All on -site soils below the stripped layer having an organic content
of less than three percent by volume are suitable for use as structural
backfill except where permeable material is required. Any imported fill
materials required at the site should be non -expansive material with a
Plasticity Index of 12 or less. All fill materials placed at the site should
not contain rocks or lumps greater than 6 inches in greatest dimension
with not more than 15percent larger than 2.5 inches. All structural fill
placed at the site should be compacted to at least 90 percent relative
compaction by mechanical means .as determined by ASTM Test
Designation D1557-70. Fill materials should be spread and compacted in
lifts not exceeding 8 inches in un-compacted thickness.
All design and construction supervision of the foundations should be
carried out by a Registered Civil Engineer.
SITE DRAINAGE
The upper areas of the area will direct surface and surface water
onto the building pad. A sub -drain system should be installed beneath the
lower level slabs. The sub -drain system should consist of one foot wide
trenches extending at least one foot below the existing grade of the
garage and building pad. Four inches diameter perforated pipes bedded
on drain rock as described under "Retaining Walls" should be installed at
the bottom of trenches. The gravel material in the trenches should be
contiguous with the layer of free draining gravel required under the slabs.
In addition, an uphill deep subsurface drainage system should be
installed across the lot to the rear of the proposed residence and
improvements. The subsurface drainage system should consist of 18
inches wide trenches that are excavated to a depth of 6 to 8 feet below
the existing adjacent site grades. Four inch diameter perforated or slotted
pipes embedded in drain rock as described in "Retaining Walls" and
P. WBITEBEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil Report 2003 - 33
March 11, 2003
Page 7
should be installed at the bottom of the trenches. The trench top should
be plugged with compacted on -site materials. All perforated drains should
connect to solid' pipes that connect to the City systems. A minimum of
2% slope is required in all pipes. Cleanouts and catch basins shall be
installed to City standards. The requirements for this drain will vary
depending on the design and location of uphill retaining walls and
drainage facilities.
Positive surface drainage should be provided adjacent to the building
to direct surface water runoff away from foundations. Concentrated water
which might cause erosion or weakening of surface soils should not be
allowed to flow across any slopes. Rainwater collected on the roof of the
building should be transported through gutters, downspouts and closed
pipes to the City storm drainage facilities.
Concrete Slabs - on - Grade:
In order to provide free drainage, slabs - on - grade are to be
founded on 4" of 3/4" crushed rock. A six mil thick plastic sheet water
vapor barrier is to be incorporated beneath the slab and is to be
protected by a two inch layer of sand.
Design parameters:
Material - Weathered Bedrock
Allowable Foundation Pressure lbs. / sq. ft.
3000.
Lateral Bearing, lbs. / sq. ft. of Depth Below Natural Grade. 400.
Lateral Sliding Coefficient 0.35.
Skin Fraction Lbs. / Sq. ft. 650
Investigation Limitations
This report has been prepared in order to aid in the evaluation of
the subsurface soils of the property and for the foundation for the
proposed structure. These services consist of professional opinions and
recommendations made in accordance with generally accepted engineering
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Soil Report 2003 - 33
March 11, 2003
Page 8
principles and practices. This acknowledgment is in lieu of all warranties
:either expressed or implied.
Respectfully submitted,
,J"
-11
Philip W itehead,
President
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P. WHITEBEDD ANDASSOCIATES
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j Project No. Ub33J3
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j Project No. Zoo?, -34
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03127/2003 16:59 94153303030 SMITH EMERY PAGE 02/02
SMITH -EMERY C;OMP.?I.NX
The Full;ervice lndepea„lent Testiv. Laboratory, 1 stoblished 1904
March 27, 2003
P Whitehead & Associates
Consulting Engineers
671 Rockdale Drive
San Francisco, California 94127
Attention: Mr. Philip Whitehead
RE: 2883 Adeline Drive, Burlingame
SUBJECT: Report of Tests
SECo File No. 60906
SECo Report No, 03-221
TEST STANDARD: ASTh4. D2937 (Density), ASTM D2216 (Moisture Content) and
UBC 18-2/ASTM D4829 (Expansion Index)
SOURCE: Sample tt B-1, B-2, and B-3 from the above referenced site were sampled by your
representative and submitted to our laboratory on February 25, 2003.
REPORT OF TESTS
Iq, compliance with your request, we have conducted the subject tests with the results presented below.
Sample Number Description Source
B4 Dark Brown Clay with trace sand Onsite
BI Brown Clay with sand and trace gravel Onsite
B113 Dark Brown silty clayey Sand Onsite
ASTM D2937 (Density)
B=1 122.3 pcf
B2 124.1 pcf
B=3 82.7 pcf
UBC 18-2/ASTM D4829 (Expansion Index)
B=1 75, Medium Expansion Potential
Respectfully submitted,
SMITH -EMERY COMPANY
PATRICK MORRISON, R.G. 97174
Gcoservices Manager, San Francisco
2--Addressee
ASTM D2216 (Moisture Content)
13.9 %
14.1 %
16.7 %
Unified Sall Classification System
(ASTM D-2407)
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
PRIMARY DIVISIONS
GROUP
SECONDARY DIVISIONS
SYMBOL
GRAVELS.
CLEAN
(?W
Wall graded gravel*. Wavel-sand mixtures. little or no
<
MORE THAN HALF
GRAVELS
lines
LAP
Poorly graded gravel* or Wavel-*and m atures, little or
(LESS THAN
OF COARSE
ex
no lines
GRAVEL
'QM
Silly Wav*1&, gravel -sand mixtures. non-plealio lines.
_ d
FRACTION 18
C
U.
=
o
ttj
LARGER THAN
WITH
Z
0o
NO. 4 SIEVE
FINE$
QC
Clayey gravels. gravel -sand -clay mixtures, plastic lines.
p�
O
J
x
cc
;
Lu
SANDS
CLEAN
SW
Well Graded sands. Wevolly sands. little or no lines.
N
<
W
O
MORE THAN HALF
SANDS
(LESS THAN
,_
of
j
OR COARSE
6x PINES)
SP
Poorly graded sands or Wavally sands, little or no lines.
V
W
t0
FRACTION is
SANDS
SM
Silly *and*, sand -slit mixtures, non-plgglio ling&.
Z
SMALLER THAN
WITH
NO. 4 SIEVE
FINES
Sc
Clayey sonde. sand -clay rninima&, plastic lines.
co
U.
a
lu
U
SILTS AND CLAYS
ML
noroan o a le end very In* sands. took flour. a ly or
clayey fine sonde or clayey But* vilh alight plasticity.
n
o
U.N
.Ji
lu
CL
norgsn s clays o ow to medium play) g ly. gravelly
J
<
a
LIQUID LIMIT I$
plays. sandy slays, silly slay*. loan clays.
q
x
m
q
LEB8 THAN 80%
OL
Organlo slits and organic e111y clays of for plasticity.
<'
_
40
p
ti
SILTS AND CLAYS
MH
Inorgan o slits, mloateou* or alomsaeous line sandy or
O
6
silly &oils. elastic slits.
ZCC
w
p
¢
1W-
=
LIQUID LIMIT IS
CH
inorganic slays of high plasticity. let clays.
D-
GREATER THAN $OK
OH
Orpenle clays of medium to high pla*tlolly, organic sills.
HIGHLY ORGANIC SOILS
Pt
Peat and *that highly organic *oil*.
DEFINITION OF TERMS
U.B. STANDARD SERIES
SIEVE
CLEAR SQUARE SIEVE OPENINGS
200 40
10
4 3/40 3' 12'
BAND
GRAVEL.
SILTS AND
CLAYS
COBBLES
BOULDERS
FINE
MEDIUM
COARSE
I FINE
COARSE
DRAIN SIZES
BANDS AND GRAVELS
BLOWS/FOOT t
VERY LOOSE
0-4
LOOSE
4 - 10
MEDIUM DENSE
10 - 30
DENSE
30 - 60
VERY DENSE
OVER 60
RELATIVE DENSITY
SILTS AND CLAYS
STRENGTHI
BLOWSIFOOT'
VERY SOFT
0-1/4
0-2
SOFT
114 - 112
2-4
FIRM
112 - 1
4 - 8
STIFF
1-2
8 - 16
VERY STIFF
2-4
/8 - 32
HARD
OVER 4
OVER 32
CONSISTENCY
f Number of blows at 140 pound hammer falling 30 Inches to drive a 2 Inch O.D. (1-3/8 inch I.D.)
split spoon (ASTM D-1688).
't Unconfined compressive strength In Ionalsq. It. as determined by laboratory testing or approximated
by the standard penetration test (ASTM D-1688), pockel penetromster. torvans, or visual observation.
CIVIL, STRUCTURAL, SOILS
ki
.V
92
0
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
L� rA P/r/L
Z o 6;Sicl�-j
e 77H
r O lJ t-, A � %-- l o w �O�F7 %— A[ L
11
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
37`
45
30
p 10 20 KILOMETERS
FIGURE 43.—Estimated relative intensities of ground shaking in
the south San Francisco Bay region from large earthquakes
on the San Andreas and Hayward faults (Borcherdt, Gibbs,
and Lajoie, 197A5). 1906 violent, Francisco en�(C) Very shquake trong,
e of
Wood (1908): (A)
(D) Strong, (E) Weak- Note that areas of violent intensity (B)
lie immediately adjacent to the faults in the regions underlain
by bedrock but lie at successively greater distances from the
faults in areas underlain by alluvium and bay mud. This
broadening of the higher intensity zones is due to seismic am-
plification of the bedrock waves by the unconsolidated sedi-
mentary deposits.
P. WHITEHEAD AND ASSOCIATES
CONSULTING ENGINEERS
Excerpt from ee in 's Civil Code
Section 1. Section 832 of the Civil Code is amended to read:
832. Each conterminous owner is entitled to the lateral and subjacent
support which his land receives from the adjoining land*subject to the right
of the owner of the adjoining land to make proper and usual excavations on the
same for the purposes of construction or improvement, under the .following
conditions:
1. Any owner of land or his lessee intending to make or to permit an
excavation shall give reasonable notice to the owner or owners of adjoining
lands and of buildings or other structures, stating the depth to which such
excavation is intended to be made, and when the excavation will begin.
2. In making any excavation, ordinary care and skill shall be used, and
reasonable precautions taken to sustain the adjoining land as such, without
--regard to any building or other structure which may be thereon, and there
shall be no liability for damage done to any such building or other structure
by reason of the excavation, except as otherwise provided or allowed by law.
3. If at any time it appears that the excavation is to be of a greater
depth than are the walls or foundations of any adjoining building or other
structure, and to be so close as to endanger the building or other structure
in any way, then the owner of the building or other structure must be allowed
at least 30 days, if he so desires, in which to take measures to protect the
same from any damage, or in which to extend the foundations thereof, and he
must be given for the same purposes reasonable license to enter on the land.on
which the excavation is to be or is being made.
4. If the excavation
depth of foundations, which
the adjacent curb level, at
the curb and if on the land
other structure the wall o
deeper, then the owner of
shall, if given the necessai
the said adjoining land ar
without cost to the owner i
and shall be liable to th
excepting only for minor set
As amended June 25, 1968
Senate Bill 1225
Effective November 15, 1968
is intended to be or is deeper than the standard
depth is defined to be a depth of nine feet below
the point where the joint property line intersects
of the coterminous owner, there is any building or
r foundation of which goes to 'standard depth or
the land on which the excavation is being made
•y license to enter on the adjoining land, protect
d any such building or other structure thereon
hereof, from any damage by reason of excavation,
e owner of such property for any such damage,
tlement cracks in buildings or -other structures.