HomeMy WebLinkAboutCDP 06-16; Matsubara Residence; Soil Investigation; 2007-04-09CIVIL, GEOTECHNICAL, <& QUALFTY ENGINEERING
FOUNDATION DESIGN * LAND SURVEYING * SOIL TESTING
CLIENT: MATSUBARA
PROJECT: MAT 307-INV
DATE: 9 APRIL 2007
MR. TAEKO MATSUBARA T,l7rFTVFn
1360 Forrest Ave. RLCHlVlili
Carlsbad, CA. 92008 MAY 1 1 2007
Subject: Limited Soil Investigation for the Proposed Room Additions for ppJfJ^^iMT
Residence located on Chinquapin Ave., Carlsbad, CA.
(APN: 206-262-11)
Dear Mr. Matsubara:
Pursuant to your request, we have completed our site inspection for the
subject parcel. The purpose of this investigation was to determine the general
engineering characteristics ofthe soils on and underlying the site and to provide
specific recommendations for the design parameters for foundations and retaining
structures, slab-on-grade floors and site earthwork.
>-
The proposed development consists of the construction of a single/two
story, wood framed, stucco type residential structure on a vacant lot. At the time
of this investigation, the lot was covered with some low lying grasses and other
native vegetation.
On 19 March 2007, a field investigation was performed at the subject site.
This investigation consisted ofthe excavation of 2 test pits dug with a backhoe.
As the test pits were advanced, the soils were visually classified by our field
representative. Undisturbed and bulk samples, as well as in place density tests,
were obtained at various depths representative of the different soils horizons. All
samples were retumed to our laboratory for detailed testing.
Based on our visual inspections and observations in the field, and our
laboratory test results, the following conclusions were derived. It is our opinion ^
that the subject lot may support the proposed residential structure. However, the jjj
conclusions and recommendations found in the latter part of this report shall be mjm
incorporated in the design plans and specifications. ^
1611-A SO. MELROSE DRIVE #285, VISTA, CA 92081-5471 Ph: (760) 945-3150 Fax: (760) 945-4221
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GRADING
On the basis of our investigation, development of the site as proposed is
considered feasible fi*om a soils engineering standpoint provided that the
recommendations stated herein are incorporated in the design of foundation
systems and are implemented in the field.
Site preparation should begin with the removal the existing surface
vegetation and other deleterious matter. These materials are not suitable for
support of the proposed structure and should be exported fi*om the site. Also, any
subsurface structures such as cesspools, wells, or abandoned pipelines, which are
uncovered during the clearing operation, shall be removed or backfllled in
accordance with the requirements of the City of Carlsbad.
All on-site earth materials are considered suitable for the support ofthe
proposed structures. However, prior to construction or placing fill, the loose
surface materials occurring in the area of the proposed house pad shall be
removed to a depth where firm, dense native soils are encountered. The depth of
removal is anticipated to be approximately 3 to 5 feet below the existing surface.
This can be accomplished during the rough grading operation by over-excavating
the upper 3 to 5 feet of the surface soils, ripping the exposed bottom surface to a
minimum depth of 12 inches, and recompacting the soil to the design grade. All
structural fill shall be compacted to at least 90% of the maximum dry density at
near optimum moisture content as determined in accordance with ASTM Test
Procedure D 1557-01.
In the event that the fmish grade soils expose a transition lot condition; i.e.,
a cut/fill daylight line through the proposed structure, the cut portion ofthe house
pad shall be over-excavated and recompacted to a depth of 3 feet below the
finished grade. The limits of over-excavation shall extend a minimum of 5 feet
outside ofthe perimeter building foundations. This will provide a uniform fill
blanket for an even support of the structure and will help mitigate the effects of
differential settlement. It is anticipated that the building footings may experience
less than 1 inch settlement with less than V2 inch differential settlements between
adjacent footings of similar sizes and loads.
Site drainage should be dispersed by non-erodible devices in a manner to
preclude concentrated runoff over graded and natural areas in accordance with the
City of Carlsbad requirements.
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1611 -A so. MELROSE DRIVE #285, VISTA, CA 92081 -5471 Ph: (760) 945-3150 Fax: (760) 945-4221
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GEOLOGIC HAZARDS
According to published information, there are no known active or
potentially active faults on or in the immediate vicinity ofthe subject site.
Therefore, the potential for ground rupture at this site is considered low. There
are, however, several faults located within a close proximity to this site that the
movement associated with them could cause significant ground motion. The
following table presents the distance of major faults fi'om the site, the assumed
maximum credible earthquake magnitudes and estimated peak accelerations
anticipated at the site. The severity of ground motion is not anticipated to be any
greater at this site than in other areas of San Diego County.
SEISMICITY OF MAJOR FAULTS
MAXIMUM MOMENT SLIP RATE
FAULT/TYPE DISTANCE MAGNITUDE(RICHTER) mm/year
Rose Canyon (B) klOkm 6.9 1.5
Elsinore-Julian Seg(A) 24 mi. 7.1 5
San Jacinto-Borrego Seg(B) 47 mi. 6.6 4
San Andreas-South-Seg(A) 71 mi. 7.4 24
The following information is presented relative to the subject site and
Seismic Zone 4 per the Califomia Building Code, C.B.C:
(z) Seismic zone factor = 0.4 Table 16 A-I
(Na) Near-source factor = 1.0 Table 16 A-S
(B) Seismic source type = B Table 16 A-U
(Sd) Soil proflle type = Sd Table 16 A-J
(Ca) Seismic coefficient = 0.44 Na Table 16 A-Q
(Cv) Seismic coefficient = 0.64 Nv Table 16 A-R
(Nv) Near source factor = 1.0 Table 16 A-T
LIQUEFACTION POTENTIAL
Liquefaction analysis of the soils underlying the site was based on the
consideration of various factors which include the water level, soil type gradation,
relative density, intensity of ground shaking and duration of shaking.
Liquefaction potential has been found to be the greatest where the ground water
level is shallow and loose fine sands occur within a depth of 50 feet or less. These
conditions are not present within the site area and, therefore, the potential for
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1611-A SO. MELROSE DRIVE #285, VISTA, CA 92081-5471 Ph: (760) 945-3150 Fax: (760) 945-4221
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generalized liquefaction in the event of a strong to moderate earthquake on nearby
faults is considered to be low.
In general, the native soils at a depth of 1 to 4 feet below the existing
surface are considered to have a very low expansion potential (EI = 0) according
to our Expansion Test results. Enclosure (1). Therefore, additional foundation and
slab requirements are not considered necessary in regard to soil expansion.
Foundations shall be sized and constmcted in accordance with the Stmctural
Engineer's design, based on the earth pressures and the allowable bearing values
listed in the latter part of this report, along with the expected live and dead loads,
and the projected wind and seismic loads. All grading and/or foundation plans
shall be reviewed by our Engineer.
FOUNDATION DESIGN
The proposed stmcture for this project can be supported by conventional
isolated, spread and/or continuous footings using the following soil parameters.
For foundation design purposes, the following earth pressures were calculated
based on our Shear Test results Enclosure (1) for the native soils and based on a
foundation depth and width of 12 inches:
Test Pit No. 1 at 1 to 4 feet below the surface:
(Brown fine SAND)
Shear Test: Cohesion =171 psf; Angle of Friction = 34°.
Allowable Bearing Value = 1850 psf
Equivalent Fluid Pressure = 35 pcf
Passive Lateral Resistance = 400 pcf
At-rest Pressure = 55 pcf
Coefficient of Friction = 0.35
Expansion Index = 0 (Non-expansive)
These values are for dead plus live loads and may be increased by one-third
(1/3) for seismic and wind loads where allowed by code. These design bearing
values are in accordance with the Uniform Building Code.
The surface soil was tested for sulfate content by Clarkson Laboratory and
Supply, Inc., on March 23, 2007. The results of this test indicated that the water
soluble sulfate content was found to contain <0.001% (Negligible) per
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161 l-A SO. MELROSE DRIVE #285, VISTA, CA 92081-5471 Ph: (760) 945-3150 Fax: (760) 945-4221
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Califomia Test 417 (See enclosure 2). Therefore, per the 2001 Califomia
Building Code, Type II cement with a maximum water-cement ratio of 0.50 and a
minimum concrete strength (f c) of 2500 psi should be used for concrete in contact
with on-site earth materials.
RETAINING WALLS
An equivalent fluid pressure of 35 pcf may be used for design of retaining
walls with level backfill and 55 pcf for 2H:1V sloping backfill. These figures are
based on a drained condition and use of granular backfill having a sand equivalent
of 30 or greater. Ifthe native soils are used as backfill, the equivalent fluid
pressure of 35 pcf (level) and 55 pcf (2H:1V slope) for active conditions and 60
pcf (level) and 70 pcf (2H:1V sloping) for at-rest conditions can be used.
FOUNDATIONS
It is recommended that the continuous perimeter foundations and concrete
slabs for a light-weight, wood fi-amed stmcture shall be reinforced in accordance
with the following minimum designs:
a. For slab-on-grade floors: it is recommended that the continuous perimeter
foundations for a single story stmcture shall extend a minimum depth of 15 inches
and a minimum widtii of 15 inches into the firm native or compacted fill material
as measured fi^om the lowest adjacent grade. A minimum of 18 inches deep by 15
inches wide shall be used for a two story stmcture.
b. All foundations shall be reinforced with at least four No.4 steel bars, two
bars shall be placed 3 inches fi-om the top ofthe foundation and the other bars
shall be placed 3 inches firom the bottom. As an altemative to the 4 steel bars, the
contractor may substitute two No. 5 steel bars, one top and one bottom.
c. Footings placed on or adjacent to the top of cut or fill slopes shall have a
minimum horizontal distance of 7 feet firom the bottom edge of the footings to the
face ofthe slope, for slopes less than 20 feet in height. For slopes greater than 20
feet, a horizontal distance of H/3 shall be used where H = height of slope, but
need not exceed 40 feet maximum. (See attachment A)
d. All interior concrete slabs shall be a minimum of 4 inches in thickness
and reinforced with a minimum of No. 3 rebar at 18 inches on center both ways
placed in the center oftiie slab. The bars shall be bent downward into the
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1611-A SO. MELROSE DRIVE #285, VISTA, CA 92081-5471 Ph: (760) 945-3150 Fax: (760) 945-4221
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perimeter footings and wire tied to the foundation steel at 18 inches on center. In
order to minimize vapor transmission, an impermeable membrane (ie: 10 mil
visqueen) shall be placed over 2 inches of clean, poorly graded, coarse sand,
decomposed granite, or cmshed rock. The membrane shall be covered with 2
inches of sand to protect it during constmction and the sand should be lightly
moistened just prior to placing concrete. All concrete used on this project shall
have a minimum compressive strength of 2500 psi unless otherwise stated on the
Building Plans.
e. Interior concrete slabs shall be provided with saw-cut joints spaced at a
maximum of 10 feet on center each way within 24 hours afl:er the pour and the
saw-cuts shall be 1/4 ofthe slab thickness. It is imperative that the drainage
system around the proposed stmcture shall be designed and implemented to
provide positive drainage away from all buildings in order to preclude moisture
intmsion into the subgrade soils beneath the building foundations and slabs.
f Exterior slabs for hardscape, pool decks, walkways, patios, etc. shall be a
minimum of 4 inches in thickness and reinforced with a minimum of No. 3 steel
rebars at 24 inches on center each way. The reinforcing steel shall be placed in the
upper 1/3 ofthe slab and held in place with concrete chairs.
If imported soil materials are used during grading to bring the building pad
to the design elevations, or if variations of soils or building locations are
encountered, foundation and slab designs shall be reevaluated by our firm upon
the completion of the rough grading operation.
LIMITATIONS AND UNIFORMITY OF CONDITIONS
The analysis and recommendations submitted in this Report are based in
part upon the data obtained from tiie test pit excavations performed on the site and
our experience and judgement. The nature and extent of variations between the
test pits may not become evident until constmction. If variations then appear
evident, it will be necessary to re-evaluate the recommendations of this Report.
Findings ofthe Report are valid as of this date; however, changes in
conditions of a property can occur witii passage of time whether they be due to
natural process 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
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1611 -A so. MELROSE DRIVE #285, VISTA, CA 92081 -5471 Ph: (760) 945-3150 Fax: (760) 945-4221
UJS^U EiHiiueeriiMif tne
be invalidated wholly or partially by changes outside our control. Therefore, this
Report is subject to review after a period of one year.
In the event that any changes in the nature, design, or location of buildings
are plaimed, the conclusions and recommendations contained in this Report shall
not be considered valid unless the changes are reviewed and the conclusions of
tills Report are modified or verified in writing.
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 the
recommendations contained herein are called to the attention of the project
Architect and Engineer and are incorporated into the plans. Further, the necessary
steps shall be taken to ensure that the contractor and subcontractors carry out such
recommendations in the field.
It is recommended that the Soil Engineer be provided the opportunity for a
general review of the final design plans and specifications for this project in order
that the recommendations of this report may be properly interpreted and
implemented in the design. It is also recommended that the Soil Engineer be
provided the opportunity to verify the foundation and slab constmction in the field
prior to placing concrete. (If the Soil Engineer is not accorded the privilege of
making these reviews, he can assume no responsibility for misinterpretation of his
recommendations).
The Engineer has prepared this Report for the exclusive use of the
client and authorized agents. This Report has been prepared in accordance with
generally accepted soil and foundation engineering practices. No other warranties,
either expressed or implied, are made as to the professional advice provided under
the terms of this agreement, and included in the Report.
B&B Engineering Inc. and Associates appreciate this opportunity to be of
service. Should you have any questions regarding this project, please do not
hesitate to contact us.
-!^!(^./ Sincerely,
Na 38523 Stephen B.Peter RCE 38623
, £»p.__ /^y Expires 3-31-(f?
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1611-A so. MELROSE DRIVE #285, VISTA, CA 92081-5471 Ph: (760) 945-3150 Fax: (760) 945-4221
Direct Shear Test Results
3.0
M
m
S. 25
m
m 2.0
• Shear Strength
inches of Defon
• Shear Strength
inches of Defon at 0.2
mation
t
p-
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Confining Pressure (ksf)
3.5 4.0 4.5 5.0
INTERNAL
FRICTION
COHESION
INTERCEPT
TP1@1-4 BRN FINE SAND (SHEAR REMOLDED TO 90% OF M.D.)
Shear Strenath at ^ ,
0.7 Inches of Deformation E^PtxKJ^IOi^ lOiTey. = O - A/OA^-£:y.PAAJ3l VB
^SlO SOUTHERN CALIFORNIA
(Sm^ SOIL & TESTING
B&B ENG (MAT 306 INV) ^SlO SOUTHERN CALIFORNIA
(Sm^ SOIL & TESTING BY: JJS/GBF DATE: 4/3/2007
^SlO SOUTHERN CALIFORNIA
(Sm^ SOIL & TESTING
JOB NUMBER: 0712032 APPENDIX 11-10
IJABUKATUK2C REPORT
Telephone (619) 425-1993 Fax 425-7917 Established 1928
CLARKSON LABORATORY AND SUPPLY INC.
350 Trousdale Dr. Chula Vista, Ca. 91910 www.clarksonlab.com
ANALYTICAL AND CONSULTING CHEMISTS
Date: March 23, 2007
Purchase Order Nuinber:
Sales Order Nuinber: 87765
Account Nuinber: B&B
To:
* *
B&B Engineering
1611-A SO. Melrose Drive #285
Vista, CA 92081
Attention: Dennis P. Beard
Laboratory Nuinber: S02254 Customers Phone: 760-945-3150
Fax: 760-945-4221
Sample Designation:
* *
Five soil samples received on 03/21/07 marked as follows:
ANALYSIS: Water Soluble Sulfate California Test 417
Sample S04%
Matsubara Mat 307 Inv.
TP-1@1-4'A <0 .001
Forbes For 307 TP-l@-2-3' 0 .013
Hackbart Hac 307 TP-1@2-12' 0 .045
Lattin Lat 307 Inv. TP-1@3'-A 0 .002
Lattin Lat 307 TP-1@10'-C 0 .002
Note: < Is the symbol for less than.
jaura Torres
LX/sd
FIGURE 1BA-I-1 2001 CAUFORNIA BUILDING CODE
FACE OF FOOTING
TOP OF SLOPE
'FACE OF
STRUCTURE
//A^W \ —1
^ WHK . - J A
//A\W
TOE OF SLOPE
'H/3 BUT NEED NOT
EXCEED 40 FT.
(12192 mm) MAX.
H
HI2 SUT NEED NOT EXCEED 15 FT. (4572 mm) MAX,
FIGURE 18A.I0—SETBACK DIMENSIONS
ATTACHMENT A