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BRES2017-0041 Geotechnical UpdateMar0617,11:55a Richard Doan Construction W 858-755-1852 p.1 03q Sfadden .Engineering 45090 Golf Center Parkway, Suite F, Indio, CA 92201 (764863-0713 Fax (760) 863-0847 6782 Stanton Avenue, Suite C, 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. CA. 92543 (951) 766-8777 Fax (951)166-V18 N December 19, 2016 Project No. 544-16335 16.12-511 Mr. Richard Doan✓'T�!' �����/ P.O. Box 8011 C Rancho Santa Fe, California 92067��E.� pEpTd G Subject•. Geotechnical Update & SA gvILD�N ® V APP Project: Proposed Custom Residence FQR GONS 81-753 Baffin Avenue 6Y The Madison Club— Lot 118B DATE La Quinta, California Ref: GeotechnicalIhvestigation Report prepared by Sladden Engineering dated January '28, 2005; 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 reports as they relate to the design and construction of the proposed custom residence to be constructed on the site located at 81-753 Baffin Avenue within the Madison Club development in the City of LaQuinta, 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 subject. lot was previously graded during the rough grading of the Madison Club project site. The rough grading included over -excavation and recompaction of the native surface soil along, with the placement of engineered fill material to construct the building pads. The site grading is summarized in the referenced report of Testing and Observation During Rough Grading along with the compaction test results. Because the lot has been previously rough graded, the remedial grading required at this time should be minimal provided that the building area that falls within the previously assumed building envelope. The building areas should be cleared of surface vegetation, scarified and moisture conditioned prior to precise grading. The exposed surface should be compacted to a minimum of 90 percent relative compaction prior to fill placement. The previously removed soil and any fill material should be placed in thin lifts at near optimum moisture content and compacted to. at least 90 percent relative compaction. RECEIVED MAR 1.6 2017 QUINTA .a1_uurrrurvWpf748{yrYWDEI/EI.0P� E� www.Sladdenengineeripig.com Mar 0617, 11:55a. Richard Doan Construction December 19, 2016 858-755-1852 p;2 -2- Project No. 544-16335 16-12-511 The referenced reports include recommendations pertaining to the construction of residential structure foundations. The previous reports also address the potential for liquefaction, subsidence and differential -settlement- Based upon our review of the referenced reports, it is our Opinion that the structural values included in .these reports remain applicable for the design and construction of the proposed residential structure foundations. The allowable bearing pressures recommended in the referenced Geotechnical Investigation report remain applicable. Conventional shallow spread footings should be bottomed into 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 1500 psf and 2000 psf, respectively' Allowable increases of 300 psf for each additional 1 foot of width and 300 psf for each. additional 6 inches of depth may be utilized, if desired. The maximum allowable bearing pressure should be 3000 psf. The recommended allowable bearing pressures may be increased by one-third for wind. and seismic loading.. Lateral forces may be resisted by friction along the base of the foundations and passive resistance along the sides of the footings. A friction coefficient of 048 times the normal dead load forces is recommended for use in design. Passive resistance may be estimated using an .equivalent fluid weight of 300 pcf. If used in combination with. the passive resistance, the frictional resistance. should be reduced by one third to 0.33 times the normal dead load forces. The bearing soil is generally non -expansive and falls within the "very low" expansion category in accordance with the 2013 (CBC) classification. criteria. Pertinent 2013 CBC Seismic Design parameters are summarized on the following page. Sladden has reviewed the 2013 California: Building Code (CBC) and summarized the current, seismic design parameters for the proposed. structure. The seismic design category for a structure may be determined in accordance with Section 1613 of the 2013 CBC or ASCE7. According to the 2013 CBC, Site Class D may be used to estimate design seismic loading for, the proposed structure. The 2013 CBC Seismic Design Parameters are summarized below. Risk Category (Table 1.5-1): I/II/B1 Site Class (Table 161332): D Ss (Figure 1613.3=1): 1500g Si. (Figure 1613`.3.1): 0.700g. Fa (Table 1613.3.3(1)):1.0 Fv (Table.161353(2)):1.5 Sms (Equation 16-371Fa X Ss)):.1.500g Sm1 (Equation ,16-381Fv X Si)):1.049g SDS (Equation 16-39 (2/3 X Sms)):1.000g SDI (Equation 16-4.012/3 X Smi)): 0.700g Seismic Design Category: D i" Sladden Engineering www.Sladdenengincering.com Mar 0617, 1.1:55a Richard Doan Construction 858-755-1852 p:3 December 1.9, 2016 -3= Project No. 54-16335 16-12-511 We appreciate the opportunity to provide service to you on this project. If you have any questions regarding this letter or the referenced reports, please contact the undersigned:. Respectfully submitted,. SLADDEN ENGINEERING Q�CFES."Zi BRETT L_ �yc ANDERSON . No. C453" Z Brett L. Anderso Exp..9r30118 Principal Engineer ENGINEERING SER/cibQF CA`CQ��� Copies: Q W. Richard Doan G Sladden Engineering www.Sladdenengineering com.