07-2524 (SFD) Geotechnical UpdateFR(",i+ SLADDEN PALM DESERT (FRO AUG 24 2007 11 :20/ST. 11 :19f No. 6802770373 P 1
Sladden Engineering
6782 Stanton Ave., Suite A. Buena Park, CA 90621 (714) 523-0852 Fax (714) 523-1369
39-725 Garand Ln., Suite 0, Palm Desert, CA 92211 (760) 772-3893 Fax (760) 772-3895
August 22, 2007
Benjamin Hertz Architect
645 Oleander Road
Palm Springs, California 92264
Attention: Mr. Benjamin Hertz
Subject: Geotechnical Update
Project: Madison Club — Lot 46A
Tentative Tract 33076
l,a Quinta, California
Project Nn.:544-07302
07-08-595
Ref; Geotechnical Investigation Report prepared by Sladden Engineering dated January
28, 2WS; Project No. 544.4810, Report No. 05-01-101.
Report of Testing and Observation during Rough Grading prepared by, Sladden
Engineering dated March 2, 2006; Project No. 522-4810; Report No. 06.02•120
As requested, we have reviewed the above referenced geotechnical report as it relates to the
design and construction of the proposed residence. The project site is located on lot 46A within
the Madison Club development on the northeast comer of Avenue 54 and Madison Stwet in the
City of La Quinta, Califomis. It is our. understanding that the proposed residence will :include a
subtcrancal basement level.
The referenced geotechnical reports include recommendations for the design and construction of
residential building foundations and retaining wall. Based upon our review of the referenced
report and our recent site observations, it is our opinion that the recommendations included in
the above referenced reports remain applicable for the proposed single family residence.
Footings should extend at least 12 inches beneath lowest adjacent grade. isolated square or
rectangular footings should be at least two feet square and continuous footings should be at least
12 inches wide. Continuous footings may be designed using an allowable bearing value of 1500
pounds per. square foot (psf) and isolated pad footings may be designed using an allowable
bearing pressure of 1800 psf. Allowable increases of 250 psf for each additional 1 foot -of width
and 250 psi for each additional 6 inches of depth may be utilized if desired. The maximum
allowable bearing pressure may be Increased to 3500 psf, When Lvnsidering basement wall
footings. The allowable bearing pressures are applicable to dead and frequently applied live
loads. The allowable bearing pressures may be increased by 1/3 to resist wind and seismic
loading.
FROLq SLADDEN PALM DESERT
(FR I) AUG 24 2007 11 :20/ST. 11 :19/No. 6802770373 P 2
August 22, 2007 -2- Project No. 54407302
07-08-595
The recommendations made in the preceding paragraph are based on the assumption that all
footings will be supported by properly compacted soils. Prior to the placement of the reinforcing
steel and concrete, we recommend that the footing excavations be inspected in order to verify
that they extend into the firm compacted soils and are free of loose and disturbed materials.
Settlements may result from the anticipated foundation loads. These estimated ultimate
vPttlements are calculated to be a maximum of 1 inch when using the recommended bearing
values. As a practical matter, differential settlements between footings can be assumed as one-
half of the total settlement. These elastic. settlements are expected to occur during cvnsts-uction.
Resistance to lateral loads may be provided by a combination of. friction acting at the base of the
slabs or foundations and passive earth pressure along the sides of the foundations. A coefficient
of friction of 0 90 between soil and concrete may be used for dead load forces only. A passive
earth pressure of 250 pounds per square foot, per foot of depth, may be used along the sides of
footings which are poured against properly compacted native or approved import soils.
Retaining walls may be required to accomplish the proposed construction. Cantilever, retaining
walls may be designed using "active" pressures. Active pressures may be estimated using an
equivalent fluid weight of 35 pcf for native backfill soils with level free-drainin3 backfill
conditions. For walls that arc restrained (such as the basement walls), "at rest' pressures should
be utilized in design. At rest pressures may be estimated using an equivalent fluid weight of 55
pcf. Walls should be provided with adequate drainage.
T'he site was previously graded during the rough grading of the Madison Club project site and
was recently regraded. The rough grading included overexcavation of the native surface soil
along with the placement of engineered fill material to construct the building pads. Because the
subject lot has been previously rough graded, the remedial grading necessary at this time should
be minimal except for the subteranem level. It is likely that the basement level will extend
through the previously placed engineered fill material. If the basement extends through the
compacted fill, additional overexcavation will be required.
It should be noted that the cite is Incated within a seismically active area of Southern California
and it is likely that the proposed structures will experience strong ground shaking as a result of
an earthquake event along one of the faults in the region during the expected I& of the
development. As a minimum, structures should be designed based upon Seismic Zonc 4 design
criteria included in the Uniform Building Code (UBC). The potential for liquefaction or other
geologic/seismic hazards occurring at the site is considered to be negligible.
Sladden Engineering
FROM,SLADDEN PALM DESERT
August 22, 2007
(FRO AUG 24 2007 11 :20/ST. 11 :19,,No. 6802770373 P 3
-3-
Project Na 544-07302
07-08=595
We appreciate the opportunity toprovide service to you on this project, if youi have any
,questions regarding this letter or the referenced reports please contact the undersigned.
Respectfully submitted,
,SLADDEN ENGINEERING-�
Brett L; A�ehlo c� �o V ► ; 0
w x•
Principal Engineer * Exp. 9.30-2000
SER/Sl T . CNS
Copies; 4/Benjamin Hertz Architect
Sludden Engineering
FR0.14:SLADDEN PALM DESERT
(FRO AUG 24 2007 11 :20/ST. 11 :19!No, 6802770373 P 4
August 22, 2007 -4- Project No. 544-07302
07=0&595
2001 CALIFORNIA BUILDING CODE SEISMIC DESIGN INFORMATION
The California Code of. Regulations, Title 24 (2001 California Building Code) and 1997 Uniform
Building Code, Chapter 16 of this code, contain substantial revisions and additions to earthquake
engineering design criteria. Concepts contained in the code that will be relevant to construction
of the proposed Aructures are summarized below.
Ground shaking is expected to be the primary hazard most likely to affect the site, based upon
proximity to significant faults capable of generating large earthquakes. Major fault zones
considered to be most likely to create strong ground shaking at the site are listed below.
Fault Zone
Approximate Distance
From Site
Fault TyBe
(1997 UBC)
A
San Andreas
8.9 km
San Jacinto
30.9 km
A
Based on our field observations and understanding of local geologic conditions, the soil profile
type judged applicable to this site is Sv; generally described as stiff or dense soil. The site is
located within UBC Seismic Zone 4. The following table presents additional coefficients and
factors relevant to seismic mitigation for new construction upon adoption of the 1997 oode.
Sladden Enjnneenng
Near -Source
Near -Source
Seismic
Seismic
Seismic
Acceleration
Velocity
Coefficient
Coefficient
Source
Factor, NA
Factor, N.
(;,
C�
San Andreas
1.04
1.29
0.44 Na
0164 N.
`San acinto
1.0
1.0
0.44 N�
0.64 N„
Sladden Enjnneenng