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BRES2015-0380 Geotechnical UpdateSladden Engineering 45090 Golf Center Parkway, Suite F, Indio, CA 92201 (760) 863-0713 Fax (769) 863-0847 6782 Stanton Avenue, Suite C, Buena Park, CA 90621 (714) 523-0952 Fax (716.) 523-1369 450 Egan Avenue, Beaumont, CA 92223 (951) 845-7743 Fax (951) 845 -EM 800 E. Florida Avenue, Hemet, CA 92543 (951) 766-8777 Fax (951) 766-3778 August 3, 2015 Mr. & Mrs. Scott Spehar c/o Ochoa Design Associates 73-626 Highway 111 Palm Desert, California 92260 Project: Proposed Custom Residence 80-750 Via Montecito — Lot 74D The Hideaway La Quinta, California Subject: IGeoteehni" calCUpdW Project No. 544-15186 15=08-322 R F --- E V F D NOV 2 A, 1-00 CITY (_)t LP, "4upk VTA COMMUNITY DEVELOPMENT Ref: Geotechnical Engineering Report prepared by Earth Systems Southwest (ESSW) dated September 22, 2000; File No. 07117-10, Report No. 00-09-772 Report of Testing and Observation During Rough Grading prepa-ed by ESSW dated August 28, 2002; File No. 07117-11, Report No. 01-07-718 Report of Testing and Observation During Rough Grading prepared by Sladden Engineering dated October 12, 2003; Project No. 544-2199 Report Ne. 03-10-647 As requested, we have reviewed the above referenced geotechnical reports as they relate to the design and construction of the proposed custom residence. The project site is located at 80-750 Via Montecito within the Hideaway Golf Club development in the City of LE Quinta, California. It is our understanding that the proposed residence will be a relatively light-rveight wood -frame structure supported by conventional shallow spread footings and concrete slays on grade. The subject lot was previously graded during the rough grading of the Hideaway project site and was subsequently regraded. The rough grading included over -excavation of the native surface soil along with the placement of engineered fill soil to construct the building pads. The regrading included processing the surface soil along with minor cuts and fills to construct the individual building pads to the current configurations. Some additional over -excavation was performed in areas where the building envelopes were reconfigured. The most recent site grading is summarized in the referenced Report of Testing and Observations During Rough Grading prepared by Sladden Engineering along with the compktko t� 5tfte.� �Z. l A Q 1 ! I NTA vu�i v• ru i .. The referenced reports include recommendations pertaining fr�o, e_cons t o esiden ial structure foundations. Based upon our review of the ref erenced--eportrts i -r o nidn that he structural values included in the referenced grading report Fpre�a r i}T � li ineer ng remain applicable for the design and construction of the proposeddential strut re foundations. I DATE 1212�f11.5 S'adden Engineering August 3, 2015 -2- Project No. 544-15186 15-08-322 Because the lot has been previously rough graded, the remedial grading required at this time should be minimal provided that the building falls within the previously established building envelope. The building area 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 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. The allowable bearing pressures recommended in the referenced grading report prepared by Sladden Engineering 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 foundation.,/slabs and passive resistance along the sides of the footings. A friction coefficient of 0.50 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 pas3ive resistance, the frictional resistance should be reduced by one third to 0.33 times the normal dead load forces. The bearing soil is non -expansive and falls within the "very low" expansion category in accordance with 2013 California Building Code (CBC) classification criteria. Slab thickness and reinforcement should be determined by the structural engineer. We recommend a minimum floor slab thickness of 4.0 inches and minimum reinforcement of #3 bars at 24 inches on center in both directions. All slab reinforcement should be supported on concrete chairs to ensure that reinforcement is placed at slab mid -height. Slabs with moisture sensitive surfaces should be underlain with a moisture vapor retarder consisting of a polyvinyl chloride membrane such as 10 -mil Visqueen, or equivalent. All laps within the membrane should be sealed and at least 2 inches of clean sand should be placed over the membrane to promote uniform curing of the concrete. To reduce the potEntial for punctures, the membrane should be placed on a pad surface that has been graded smooth without any sharp protrusions. If a smooth surface can not be achieved by grading, consideratiora should be given to placing a 1 -inch thick leveling course of sand across the e-r-ie=e.lacemPnt n membrane. MYpn P I A n " i K rr Based on our field observations and understanding of ]c type judged applicable to this site is So, generally descril additional coefficients and factors relevant to seismic miti the 2013 California Building Code (CBC). BUILDING &.SAFETY DEPT. as DATE BY Shidden Engineering August 3, 2015 -3- P=oject No. 544-15186 15-08-322 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 :)e used to estimate design seismic loading for the proposed structures. The 2013 CBC Seismic Design Parameters are summarized below. Risk Category (Table 1.5-1): I/II/III Site Class (Table 1613.3.2): D Ss (Figure 1613.3.1): 1.500g Si (Figure 1613.3.1): 0.683g Fa (Table 1613.3.3(1)): 1.0 Fv (Table 1613.5.3(2)):1.5 Sms (Equation 16-37 (Fa X Ss)): 1.500g Smi (Equation 16-38 (Fv X SI)): 1.024g SDS (Equation 16-39 (2/3 X SMS)): 1.000g SDI (Equation 16-40 12/3 X Smi)): 0.683g Seismic Design Category: D If you have questions regarding this letter or the referenced reports, please contact the undersigned. Respectfully submitted, SLADDEN ENGINEERING Brett L. Anderson Principal Engineer SER/gvm Copies: 4 / Addressee VxO BBETT L. a GOANc­R80N No. C4439 41 Fxp. Ei3G/16 CIVIL ENG,NE EP,ING _ CA' . CITY OF LAQUINTA BUILDING & SAFETY DEPT. APP�iOVED FOR CONSTRUCTION DATE BY Skdden Engineering 1571 8C /S- of$-3zZ Please verify that soils reports contain all of the above information. In addition, to assure continuity between the investigation/reporting stage and the execution stag a, please use the following checklist to verify that the conclusions and recommendations on the report cover all the required elements. Only then can we be assured that the construction documents address all of the site soil conditions. La Quinta Geotechnical Report Checklist Does the "Conclusions and Recommendations" section of the report address each of the following criteria? "Address" means: (a) the criterion is considered significant and mitigation measure(s) noted, or; (b) the criterion is considered insignificant and explicitly so stated. Yds . No Criterion ❑ Foundation criteria based upon bearing capacity of natural or ccmpacted soil. ❑ Foundation criteria to mitigate the effects of expansive soils. ❑ Foundation criteria based upon bearing capacity. of natural or ccmpacted soil. ❑ Foundation criteria to mitigate.the effects of liquefaction. ❑ Foundation criteria to mitigate the effects of seismically induced differential settlement. ❑ . Foundation criteria to mitigate the effects of long-term differential settlement. ❑ Foundation criteria to mitigate the effects of varying soil strep* gtl;.. f ❑ Foundation criteria to mitigate expected total and differential set-Jement. Any "No" answers to the .above checklist should be noted as corrections. CITY OF LA QUINTA BUILDING & SAFETY DEPT. APPROVED FOR CONSTRUCTION DATE EE, Mo. 05339 `R 9/30/16 t?►)))