HomeMy WebLinkAbout1206 & 1206 1%2 S Newhope St - Soils ReportGEOTECHNICAL INTERNATIONAL
LAN & ASSOCIATES
-l'opographic Surrel" & ('ivil. Structural. (;eotechnical, Engineering
l-'i I 19 Ilarbor Boulerard. Garden Grorc. ( \ 9l8l..i
Tel (714) 4l.r-9215. F'ax (714)537-797,1.E-mail: l,anphanrOrihotnrail.c()rrl
Pro.ject No.SA-03-02- I 9
Dccember 27. 201 9-
R
Thoa Bui
1206 S. Newhope Street
Santa Ana. CA 92704
(714't 726 - 9919
I hoakimbui52,atlithoo.com
c.o Cung Nguyen
(714) 642 - s749
clrnggngu\ en?r.t ahoo.corr
c.o Michael Vu
(714\ 878 - 7430
\ cst indc\ eloplncntA) ahoo.com
S ubj ect:Soil Report For Proposed Attached ADU And Addition To Existing One-Story
House. I 206 S. Newhope Street. City of Santa Ana" Califomia 92704.
Dear Ms. Bui:
In accordance with your request and authorization, this soil report has been prepared ibr the
proposed residential development project.
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City of Santa Ana
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It is noted that Geotechnical lnternational was the geotechnical consultant of record for many
similar residential development projects located within the City oiSanta Ana. Therefore. we are
relatively familiar with the geotechnical conditions ofthe area.
Site Description and Proposed Development
The subject site is located on the westerly side ofNewhope Street, east of Euclid Street, north of
Edinger Avenue and south ofMcFadden Avenue. u'ithin a fully developed area.
The proposed development generally consists of construction of an attached ADU and room
addition to the existing one-story house. Please see the full scale plans prepared by the
architect/designer fbr clarification ofthe proposed development. as needed.
Major grading (raw cut/ raw fill) is not proposed
Based on the published geologic map prepared by the Califomia Division of Mines and Geology'
(CDMG). the site is underlain by alluvium/colluv iurn (map symbol Q,.).
The near ground surface earth materials generally consist of silty fine sand. damp. dense, and
have a very low expansion potential.
Seismicin
For conservative purposes, the Site Class D should be used for the soil properties at the subject
site.
Thc following seismic parameters can be uscd for the subject site.
Site Coefficients:
F
F
0
5
Mapped Spectral Accelerations Values:
S.= 1.481 (for the short period of 0.2 second)
Sr = 0.546 (for the l-second period)
Maximum Considered liarthquake Spectral Response Accelerations
SM. = F"S, = 1.481 (for the short period of0.2 second)
SMr = F,Sr :0.820 (for the l-second period)
Design Spectral Response Accelerations:
Page 2
Ceotechnical Conditions
The subject site is located, in Southern Califomia. which is a major earthquake-prone region.
Therefore. the current and l'uture property owners of this property should be aware ofthe seismic
risks associated with being located in this zone.
SD. = 273 SM, = 0.987 (for the short period of 0.2 second)
SDr = 2/3 SMr = 0.546 (for the l -second period)
PGA = 0.553
The above seismic parameters should be verified by the civilistructural design engineer and
approved by the govemmenlal agency prior to using.
The Seismic Design Category D can be used for the site
The civil/structural design engineer should consult with the project geotechnical consultant. il
additional geotechnical information is needed for structural design.
Based on the Seismic Hazard Zones Map. Newport Beach Quadrangle (which cover the subject
site), the site is located within a potential liquefaction zone. Therefore. liquefaction may occur at
the site. and the property owner(s) should be aware of the risks associated with being in a
potential liquefaction zone. We recommend the proposed new structure be designed based on
up-to-date building codes and be supponed by a strengthened lbundation system as
recommended in this report to reduce the potential adverse effects due to the potential
liquefaction to the proposed new structure.
The site is a flat areal therefore, slop€ instability is not a concem for the proposed development.
Ground Water
Grounduater uas not an issue lor the entire area
Deep footings are not proposedi therefore. adverse ef'fects due to groundwater,if any. is not
anticipated for the proposed development.
It is not anticipated. llowever, if wet soils are encountered during grading/construction, removal
of *'et soils and replacement with drier soils/slurry can be performed. In addition, if needed.
geogrid layers/crushed rocks can also be used for bridging.
CONCLUSIONS AND RE
General Conclusions
Construction of the proposed development at the subject site is considered geotechnically
feasible. provided the recommendations outlined in this report are implemented.
Nole: I'he conclusions and recommendations of this report are based on inlbrmation as
interpreted from our limited subsurf'ace investigation. It is not anticipated but they should be
Page 3
[.iquefaction Potential
Slone Stabilitv
revised accordingly if geotechnical conditions to be exposed during site preparation/ grading and
construction significantly differ from our lindings and interpretations.
Conventional shallow footings with slabs-on-grade can be used for support ofthe proposed new
structure.
The following recommendalions are considered minimum and may be superseded by more
restrictive requirements ol' the architect, c iv illstructural design engineer. building codes. or
governing agencies.
Geotechnical lmpact on Ncighboring Properties
The proposed development will not adversely impact the neighboring properties from the
geotechnical perspective. provided the recommendations outlined in this report are property
implemented.
Site Preparation/Grading
For the proposed new structures with new slabs-on-grade, the 2 ft. thick near ground surface
earth materials should be scarified/over-excavated and recompacted. The over-
excavation/scarification should be extended laterally beyond the outside perimeter of the new
structure a minimum distance equal to the depth of scarification/over-excavation and
recompaction ( | ft. in this case). For proposed new exterior slab areas including new driveway. if
any. depth of over-excavation/scarification and recompaction can also be one ft..
Deeper remedial removal is not anticipated. However, ifdeeper loose/soft soils such as due to
removal ol underground objects. if any, are encountered. deeper remedial removal and
recompaction will be required. This will be determined by the geotechnical consultant based on
the actual conditions to be exposed at the time of grading.
It is not anticipated. however. if wet soils are encountered during grading. removal ol'wet soils.
such as of about 2 ft. thick. and replacement with crushed rocksislurry can be performed.
Geogrids can also be used for bridging. This will be determined by the geotechnical consultant
based on the exposed conditions during excavation at the site.
lmported soils. if any. should have a low expansion potential and should be geotechncially
observed/tested and accepted by the geotechnical consultant prior to using at the site.
In general. the till/backfill materials, if any. should be free of organic mafter and oversized
materials. 6 inches or greater in diameter. placed in near-horizontal loose lills not to exceed eight
inches in thickness. and moisture conditioned to slightly over optimum moisture content prior to
compaction. Thicker lifis can be used if capable of being properly compacted to the required
relative compaction (such as by using heavy compaction equipment).
ln general. grading at the site. if any. should be performed in accordance with the requirements
of the City of Santa Ana and under the geotechnical observation and testing of the project
geotechnical consultant. The compaction criterion for fill and backfill materials is a minimum of
90% of the maximum density determined in accordance with ASTM Test Method D I 557.
Page 4
Geotechnical Parameters For Structural Desisn
For conservative purposes, the following values can be used for structural design, as needed.
a. Allowable vertical bearing earth pressure: 1.500 psf
An increase of one+hird is permitted when using the alternative load combinations that
include wind or earthquake loads.
b. Lateral bearing passive earth pressure: 100 psf per foot into competent materials below
the finished ground surface.
An increase of one third is permitted when using the altemative load combinations that
include wind or earthquake loads.
ln addition. the lateral resistance values are permined to be increased by the above-
recommended value for each additional foot of depth to a maximum ol I 5 times the
above-recommended value.
c. Lateral Sliding Resistance: cohesion = 130 psf
l he cohesion value is to be multiples bv the contact area.
ln no case shall the lateral sliding resistancc exceed one-halfthe dead load
d. Soil unit weight: 120 pcl'
Minimum depths fbr new building footings should be 24 inches below the adjacent finished
grades. Minimum widths for isolated columns/pad footings should be 24-inch, and lbr
continuous wall footings should be l5-inches for one-story, l8-inches for two-story. and 2l
inches for three-story portions, if any.
Where located adjacent to a utility trench, footings should be extended to have the footing
bottom located below a one-to-one imaginary plane projected from the inside bottom edge ofthe
trench.
Minimum reinforcement for continuous footings should be two #5 re-bars at top and two #5 re-
bars at bottom-
New Buildinq Slabs-on-Crade
Page 5
BUILDING IOUNDA'llON DI]SIGN Gl.JlDF-LINES
New Building Footings
New building slabs-on-grade should be minimum 5 inches thick. reinforced with #4 re-bars at
I 2-inches on-centers both ways. or equivalent. placed at mid-height of the slab.
New slabs should be underlain by a 4 inch thick layer of clean sand. For moisture sensitive floor
areas. the slabs should be underlain by minimum l0-mil polyethylene moisture barrier (such as
Visqueen). Note: our recommendations are only minimum. The capillary break-/vapor barrier in
accordance with the city requirements and or applicable Califomia Building code / Cal Creen
Code will govem and should be followed. ln addition. the entire slab system including the
capillary break/vapor barrier must be properly designed by the civil / structural design engineer
of record (but not the geotechnical engineer) and be reviewed and approved by the city prior to
construction-
To reduce the potential for excessive cracking. new exterior concrete slabs-on-grade. if any.
should be minimum 4 inches thick. provided with construction or weakened plane joints at
frequent intervals (e. g.. every 6 feet or less). Provision of a 2-inch thick layer of crushed rock.
gravel. or clean sand to be placed beneath the slabs and/or reinforcement. such as #3 rebars at l8
inches on-centers, or equivalent, placed at the mid-height of the slab should be considered. The
subgrade soils lor the exterior slabs should be properly recompacted.
Slab Subgrade Pre-Saturation
Due to the low expansion polential of the on-site soils. presaturation of the slab subgrade earth
materials is not considered necessary. However. sprinkling with water the slab subgrade earth
materials, prior to concrete pour/placement of moisture barrier membrane should be considered.
Other Recommendations fbr R educins Slab Crackins
While not a geotechnical issue. the potential lbr slab cracking may also be reduced by caret'ul
control of water/cement ratio and slump of concrete. The contractor should take appropriate
curing precautions during the pouring of concrete in hot weather to reduce cracking of slabs.
A slip sheet (or equivalent) can be utilized if grouted tile, marble tile. or other crack-sensitive
floor covering is planned directly on concrete slabs.
Scttlement
The total settlement of I inch and a differential settlement of l/2 inch over a horizontal distance
of 40 feet which are considered tolerable for residential buildings are anticipated and would
occur during the construction stage.
New Driveway
The minimum section required by the govemmental agency can be used for a new driveway. if
any. If there is no minimum requirement by the governmental agency. a 6-inch thick concrete
slab. reinforced with #3 rebars at l8 inches on-centers, 6 in. thick asphalt concrete, or equivalent
placed at mid-height ofslabs, over a 4-inch thick layer of aggregate base (AB) can be used. The
Page 6
Nerv Exterior S labs-on-Grade
aggregate base and subgrade should be Drooerly compacted to a mininrum of- 959/o an<l 9rtJ9t.
respectively, of the maximum density determined in accordance with ASTM D I 557 prior to
placement of the concrete slab. Spraying the compacted subgrade soils with water should be
perlormed prior to concrete pour.
Ifrequired. a permeable driveway covered with pavers can be used.
Site Drainaqe
In general. surface drainage at the site should be checked and improved. as needed, to ensure
surf'ace water flows away f'rom all improvement structures and into a drainage system for proper
discharge.
Irrigation at lhe site. if any. should be kept to a minimum required to support plant lit'e
ln the future. sources of uncontrolled water, such as leaky sewer, water (domestic, irrigation) or
drain pipes should be repaired if identified.
The requirements of the govemmental agency and the current CBC should be followed, as
needed.
We recommend the proposed new structure be designed to meet the current building codes and
requirements of the governing agency. The seismic parameters provided in the "Faulting and
Seismicity" section of this report can be used. The c iv il/structural design engineer should consult
with the project geotechnical consultant, if additional geotechnical information is needed for the
seismic design.
Cement Tvpe For Concrete in Contact with On-Site Earth Materials
Sulfate attack was not observed for the existing building at the site and other buildings in the
vicinity. It appears sulfate attack on concrete is not a problem for the entire City oi Santa Ana.
Therefbre. Type V cement with a maximum water/cement ratio o10.45 and a minimum concrete
strength. l. of 4,500 psi is not considered necessary. Concrete strength designed by the
c iv illstructural design engineer such as 2,500 psi can be used. lf required, sulfate content tesling
can be performed for the final subgrade soils after completion of the precise grading/site
preparation but prior to concrete pour. Based on the results of sulfate content test. modification
ofour recommendations would be performed. as needed.
Corrosion'fo Ferrous Metals and Copper
For conservative purposes. the on-site soils can be considered severely corrosive to ferrous
metals and copper. Underground/buried ferrous metals or coppcr are not planned to be used for
these project. However, if underground/buried ferrous metals or copper are planned to be used at
the site. they should be properly protected. A corrosion specialist can be consulted. Testing can
Page 7
Roofgutters and downspouts should be properly provided and maintained.
Seismic Desien
be performed for verification of the potential corrosion of the on-site soils to ferrous metals and
copper, ifneeded. The test can be performed during and/or after completion ofgrading.
All utility and drain line trench backfills should be compacted to a minimum relative compactron
of 90 percent (per ASTM D1557). The existing subgrade earth materials cannot be densified
adequately by water flooding and jetting techniques. Therefore. native trench backfill materials
should be placed in lifts approximately 6 inches in thickness, watered as necessary to achieve
near optimum moisture conditions, and then mechanically compacted in place to a minimum
relative compaction of 90 percent (per ASTM D|557). A representative of the project
geotechnical consultant should probe and test the backfills to verify adequate compaction. Note:
The pipes should be embedded and shaded with about 6 inch thick layer of imported clean sand
(for protection ofthe pipes) prior to backfilling with native soils.
As an altemative. where drain pipe or utility lines may be damaged by mechanical compaction
equipment, imported clean sand having a sand equivalent (SE) value of 30 or greater may be
utilized. The clean sand backfill materials should be watered to achieve near optimum moisture
conditions and then tampcd into place. No specific rclative compaction will be required tbr
clean sand backfill: however. observation. probing. and if deemed necessary, testing should be
performed by a representative ofthe project geotechnical consultant to verify an adequate degree
of compaction ofclean sand backfill.
If imported clean sand is to be used for backfill of exterior trenches. it is recommended that the
upper l2 inches of trench backfill materials be consisted of properly compacted on-site soil
materials. This is to reduce the potential substantial infiltration of irrigation and rainwater into
granular trench backfi ll materials.
Where an utility trench is proposed near a building footing, the bottom ofthe trench should not
extend below a l:l (horizontal to vertical) plane projected downward from the bottom edge of
the adjacent footing. Where this condition occurs. the adjacent fboting should be deepened or
the utility line should be installed first and the trench backfilled and compacted prior to
constructing the footing.
Ceotechnical lntemational will cooperate with the c iv illstructural design engineer and other
consultants of record for this project and geotechnically review the foundation plan and other
plans. if any (to be used for this project) to ensure that our recommendations have been properly
interpreted and incorporated into the design and preparation of the plans. After acceptance of the
plans. we will sign and stamp on the plans.
Geotechnical Obserl ation and I'estins During Construction
We recommend that a qualified geotechnical consultant be retained to provide geotechnical
engineering services, including geotechnical observation/testing. during the construction phase
of the project. This is to verify the compliance with the design, specifications and/or
Page 8
Utilitv and Drain Line Trench Backflll
Cooperation With Pro.iect Civil/Structural Desiqn Ensineer And Other Consultants And
Ceotechnical Review of Plans
recommendations, and to allow design changes in the event that subsurface conditions diller
from those anticipated.
Geotechnical observation/testing can be performed at the following stages:
. During ANY grading operations, including excavation. removal. filling and backfilling.
etc.. After excavation for building footings to verify the adequacy ofunderlying materials.. After pre-saturation ofslab subgrade earth materials, ifany, prior to pouring concrete.. During backfill ofdrainage and utility line trenches, ifany, to verify proper compaction
and materials used.r After compaction ofsubgrade soils and aggregate base for new driveway. ifany.. When/lfany unusual geotechnical conditions are encountered.
Note: ll'Gcotechnical lntcrnational is not provided the opportunity to perfbrm t he geotec lr rr ica I
observation/testing during the construction phase. Ceotechnical lntemational will take no
responsibility for the conclusions and recommendations contained in our report in the event that
subsurface conditions dilfer from those interpreted and anticipated during our preliminary
investigation phase prior to the start ofconstruction.
Page 9
The conclusions and recommendations contained in this report are presented based on
geotechnical data as described herein which are believed representative of the total project area.
However. earth materials can vary in characteristics. both laterally and vertically. and those
variations could affect the conclusions and recommendations contained herein. As such.
observation and testing by a qualified geotechnical consultant during the construction phase of
the project are essential to confirming the basis of this report.
This report has been prepared consistent with that level of care being provided by other
prolessionals providing similar services at the locale and time period. The contents of this report
are prol'essional opinions and as such, are not to be considered a guaranty or warranty.
This report should be reviewed and updated after a period of one year or if the property
ownership. site conditions or proposed development change from that described herein.
The following are anached and complele our report:
Appendix A Relcrenccs
Figure I Vicinity Map
F'igure 2 Site Plan/Ceotechnical Map
Ilyou have any questions or require clarification. please contact this olllce. This opportunity to
be ofservice is sincerely appreciated.
Very truly yours.
tA
Lan N. Pham, P.E.
Chief Geotechnical Engineer
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CLOSURE
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APPENDIX A
RI'FDIIENCDS
Page ll
REFERENCES
Califomia Division of Mines and Geology (CDMC). the Resources Agency.
Dept. of Conservation. 198I. "Geology Map of Orange County Showing
Mines and Mineral Deposits". scale l:48.000. l" = 4000'. or l" = 0.76 miles.
prepared in corporation with County of Orange EMA. compiled by P.K.
Morton and R.V. Miller. dated 1981.
2. Califomia Division of Mines and Geology (CDMC). Department of
Conservation. 1997. 1998, "Seismic Hazard Zones. Newport Beach
Quadrangle". Scale l:24.000 (1" = 2.000 ft or l" = 0.38 miles). Liquefaction
Zone released April 7. 1997. Landslide Zone released April 15. 1998.
Page 12
APPENDIX B
GEOTECIINICAL LOG OF
TDST IIOLD
Page 13
GEOTECHNICAL LOG OF TEST HOLE
Date:
Project No.
Hole Diameter:
DEPT}I
December 23. 2019
Bui Santa Ana
4 + inches
TEST HOLE No. I
Job No. SA-03-12-19
Equipment: and-Auger
0- l+'
t" -2 +'
DESCRIPTION
Crey/Brown clayey silt, damp, stiff/dense.
Grey/Brown fine sandy silt to sihy fine sand, damp. stiff/dense
Crey/Brown fine sandy silt to silty fine sand, damp, dense.2'end
Total Depth: 5 ft. +
No Caving
No Free Standing Groundwater
Hole back-filled with on-site soils
Page I ,l
L{I}ORATO RY I'E S'f RE STIL'I'S
Page 15
APPENDIX C
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