10-0097 (SFD) Geotechnical Engineering Report'k
Sladden. Engineering
45090 Golf Center Parkway, Suite F, Indio, CA 92201 (760) 863-0713 Fax (760) 863-0847
6782 Stanton Avenue, Suite A, Buena Park, CA 90621 (714) 523-0952 Fax (714) 523-1369
450'Egan Avenue, Beaumont, CA 92223 (951) 845-7743 Fax (951) 845-8863
800 E. Florida Avenue, Hemet, 92543 (951) 766-8777 Fax (951) 766-8778
March 18, 2010 Project No. 544-10030
10-03-057
Mr. Wayne Lunan
c/o Rick Johnson Construction
P. O. Box 2130
Rancho Mirage, California 92270
Project: Proposed Lunan Residence
55755 Pebble Beach
PGA West
La Quinta, California
Subject: Geotechnical Update
Ref: Geotechnical Engineering report prepared by Buena Engineers, Inc. dated April 17,
1986; Project No. B -14413-P3, Report No. 86-4-209
As requested, we have reviewed the referenced geotechnical report as it relates to the design and
construction of the proposed custom residence. The project site is located at 55755 Pebble Beach
within the PGA West development in the City of La Quinta, California. It is our understanding
that the proposed residential structure will be of relatively lightweight wood -frame construction
and will be supported by conventional shallow spread footings and concrete slabs on grade.
The referenced report includes recommendations pertaining to the construction of residential
structure foundations. Based upon our review of the referenced report,8 it is our opinion that the
structural values included remain applicable for the design and construction of the proposed
residential structure foundations.
Based upon our report review, our previous experience on the site and our understanding of the
proposed construction, it is our opinion that the structural values recommended in the previous
geotechnical report remain applicable for use in foundation design. Conventional shallow spread
footings should be properly .compacted fill material a minimum of 12 inches below lowest
adjacent grade. Continuous footings should be at least 12 inches wide and isolated pad footings
should be at least 2 feet wide. Continuous footings and isolated pad footings should be designed
utilizing allowable bearing pressures of 1800 psf and 2000 psf, respectively. The recommended
allowable bearing pressure may be increased by one-third when considering wind and seismic
loading. Increases in allowable bearing pressures may be realized with increased footing size.
Allowable increases of 200 psf for each additional 1 foot of width and 250 psf for each additional
6 inches of depth may be utilized, if desired. The maximum allowable bearing pressure should.
be 2500 psf.
i4 1
L March 18, 2010 -2- Project No, 544-10030
10-03-057
Resistance to lateral loads can 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 0.49 between soil and concrete may be used with dead load forces only. A passive
earth pressure of 350 pounds per square foot, per foot of depth, may be used for the sides of
footings that are placed against properly compacted native soil.
The bearing soil is non -expansive and falls within the "very low" expansion category in
accordance with Uniform Building Code (UBC) classification criteria. Pertinent 2007 CBC
Seismic Design parameters are summarized on the attached data sheet.
Because the lot has been previously graded, the remedial grading required at this time should be
minimal. The building areas should be cleared of surface vegetation, scarified and moisture
conditioned prior to precise grading. The exposed surface should be compacted so that a
minimum of 90 percent relative compaction is attained prior to fill placement. Any fill material
should be placed in thin lifts at near optimum moisture content and compacted to at least 90
percent relative compaction. -
Based on our field observations and understanding of local geologic conditions, the soil profile
type judged applicable to this site is So, generally described as stiff soil. The site is located within
UBC Seismic Zone 4. The following presents additional coefficients and factors relevant to
seismic mitigation for new construction based upon the 2007 California Building Code.
The seismic design category for a structure may be determined in accordance with Section 1613
of the 2007 CBC or ASCE7. According to the 2007 CBC, Site Class D may be used to estimate
design seismic loading for the proposed structures. The period of the structures should be less
than 1/2 second. This assumption should be verified by the project structural engineer. The 2007
CBC Seismic Design Parameters are summarized below.
Occupancy Category (Table 1604.5): I1
Site Class (Table 1613.5.5): D
Ss (Figure 1613.5(3)):1.50g
S1 (Figure 1613.5(4)): 0.60g
Fa (Table 1613.5.3(1)):1.0
Fv (Table 1613.5.3(2)): 1.5
Sms (Equation 16-37 {Fa X Ss)): 1.508
SmI (Equation 16-38 {Fv X S1)): 0.90g
SDS (Equation 16-39 {2/3 X Sms)): 1..00g
SDI (Equation 16-40 12/3 X Sm1)): 0.608
Seismic Design Category based on SDS (Table 1613.5.6(1)): D
Seismic Design Category based on SDI (Table 1613.5.6(2)): D
Sadden En--ineerinQ
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March 18, 2010 -3-
If you. have questions regarding this report, please contact the undersigned.
Respectfully submitted,
SLADDEN ENGINEERING
Brett L. And e �; m W m
Principal Engineer No. C 45389
Exp. 9-30-2010
Letter/gl `!'l9T CIVIL
F0F CALIF�P
Copies: 4/Rick Johnson Construction
Project No. 544-10030
10-03-057
.Sladden EnQineerinQ