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BRES2015-0352 Geotechnical Updatev Sladden Engineering 45090 Golf Center Parkway, Suite F, Indio, CA 92201 (760) 863-0713 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) 766-8778 October 23, 2015 Project No. 544-15280 15-10-448 Sun Vista Development Corporation P.O. Box 1144 La Quinta, California 92247woo Subject: Geotechnical Update_ Project: Custom Residence 52-560 Del Gato Drive — Lot 4 ��(`i 01 Tradition Golf Club OMMVN1 La Quinta, California G Ref: Report of Testing and Observation During Rough Grading prepared by Sladden Engineering dated July 30, 1997, Project No. 522-6138G1 Geotechnical Update report prepared by Sladden Engineering dated December 12, 1996; Project No. 444-6130 As requested, we have reviewed the referenced geotechnical reports as they relate to the design and construction of the proposed custom residence. The project site is located at 52-560 Del Gato Drive (identified as Lot 4) within The Tradition Golf Club 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 lot was previously graded during the initial rough grading of the Tradition Golf Club project site. The rough grading included over excavation and/or 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 grading report along with the compaction test results. The referenced reports include recommendations pertaining to the design and construction of residential structure foundations. 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. 3 October 23, 2015 . -2- Project No. 544-15280 15-10-448 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 1800 psf and 2000 psf, respectively. Allowable increase 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 3000 psf. The recommended allowable bearing pressures may be increased by one-third for wind and seismic loading. Increases in allowable bearing pressures may be realized with increased footing size. 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 0.48 between soil and concrete may be used with dead load forces only. A passive earth pressure of 300 pounds per square foot, per foot of depth, may be used for the sides of footings, which are placed against properly compacted native soils. 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. All slab reinforcement should be supported on concrete chairs to ensure that reinforcement is placed at slab mid -height. Because the lot has been previously graded, the remedial grading required at this time for the proposed residence 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 following presents additional coefficients and factors relevant to seismic mitigation for new construction based upon the 2013 California Building Code (CBC). The seismic design category for a structure may be determined in accordance with Section 1613 of the 2013 CBC or ASCET According to the 2013 CBC, Site Class D may be used to estimate design seismic loading for the proposed structures. The 2013 CBC Seismic Design Parameters are summarized on the following page. Sladden Engineering October 23, 2015 -3- Project No. 544-15280 15-10=448 Risk Category (Table 1.5-1): I/U/III Site Class (Table 1613.3.2): D Ss (Figure 1613.3.1):1.500g S1 (Figure 1613.3.1): 0:609g 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)): 0.9148 SDS (Equation 16-39 (2/3 X Sm5)):1.000g SD1(Equation 16-40 (2/3-X Sml)): 0.609g Seismic Design Category: D In addition, we have sampled the surface soil on the subject lots to determine the soluble sulfate content as it relates to selecting appropriate concrete mix designs. Testing indicates that the site soil is generally considered non- corrosive with respect to concrete. The testing indicated soluble sulfate content of 600 ppm (0.060 percent) that corresponds with the "negligible" exposure category in accordance with ACI 318-08, Table 3. Based upon this, the use of sulfate resistance concrete mixes should not be required. 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, SL.ADDEN ENGINEERINGaOFESS/n. _ BRETT L. rj ANDERSON Z No. C45389 m Brett L. Anderson W p• 9/30/16 CIVIL Principal Engineer ik ENGINEERING tp Letter/clb OF CAS-�F�� Copies: 4/ Sun Vista Development Corporation Sladden Engineering Please verify that soils reports contain all of the above Information. in addition, to assure continuity between the Investigation/reporting stage and the execution stage, please use the following checklist to verify that the conclusions and recommendations in the report cover all the required Blements. Only then can we be,assured that the construction documents address al 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" M' MIS: (a) the criterion Is considered significant and mitigation measures) noted, -or, (b) the criterion is considered insightficant and explicitly so stated. Yes . No Criterion i Cl Foundation criteria based upon bearing capacity of natural or compacted soil. ❑ Foundation criteria to mitigate the effects of expansive soils. ❑ Foundation ,criteria based upon bearing capacity. of natural or compacted soil. ❑ Foundation kriteria to mitigate.the effects of liquefaction. ❑ Foundation criteria. to' mitigate the effects of seismically. Induced differential settlement. ❑ Foundation arteria to mitigate the effects of long-term differential settlement. ❑ Foundation criteria to mitigate the effects of varying soil strength_ ❑ Foundation criteria to mitigate expected total and differential settlement. Any "No" answers to the -above checklist should be noted as specific required con'ections. Sladden Engineering 6.782 Stanton Ave., Suite A, Buena Park, CA 90621 (714) 523-0952 Fax (714) 523-1369 45090 Golf Center Pkwy, Suite F, Indio, CA 92201. (760) 863-0713 Fax (760) 863-0847 450 Egan Avenue, Beaumont, CA 92223 (951) 845-7743 Fax (951) 845-8863 Date: October•28, 2015 Account No.: 544-15280 Customer: Sun Vista Development Corporation Location: Traditions CC, Lot 4, 52-560 Del Gato, La Quinta Analytical Report Sulfate Series Soluble Sulfates Soluble Chloride per CA 417 per CA.422 PPM PPM 600 300 Ri dfala .rd& -i r.9Rn 1 n9R IR r. TAQLE 19=A•2-REQUIREMENTS FOR SPECIAL EXPOSURE CONDITIONS' " , - -• hTINIMUMl�, MAXIMUM • MOR D . WATER:MAE MIOUS : UG� EIGHT MATERmLS' RA1TO; BY.: AGGRECiATEgORCAE] EXPO5UAErONDt[TON •WEIGHT.�NbRMAC-WEIGHT• SUREAGGbEGATE CONCRETE • ' intended to haveh3wpermeability when x p.l)p689•lor MD- exposed to water 4,000 Conerele exposed to'freezing and tiaawing in a moist condition or to deicing chenucgls 0.45 For corrpsion projection for�tinforeed concrete 4500 exposed to chlorides from deicing Chemicals, salts or brackish:water. oespray-front thtsc'sotuces . 0.40 5,000 TABLE 19-A-3—REQUIREMENTS;FOIJCONC13ETE - OrPOSED TO SULFATE-c09TA1NING•SOLtUT10NS NORMAL-WEIGHT1. AGGEGATE AGOREG7►TE . CONCRETE Madmuin vlatar• WATER-SOLUBLE Cbmenthrous f" 'Normal- •talphtand SULFATE MdtarisWRetlo,-by:. ( t, Sqt' wdght, SULFATE PERCEMAGIE Naimol W�Igtit =,Uphtw61pht' ' -Aaaftata, . Concrilbe BY SULFATE (SO4) tN EXPOSURE W1IGH'r„ WATER, Ppm CEMEFTTYPE pilf Concrete) x01*6H9Tor6tPa Negligible D.00L0.IC 0-150 • Modecatc2_ 0.1D-0.2C 150-1,500 II, ]P(MS). is '050- 4,000 Seven 0.20-2.0U 45D0-110.000 V 0.45r ¢,500 Very seven Over20p Over 10,000 V plus 0.45 4500 . • , poaolanz _ _ to lower water-ccmzntidotu maxrials ratio orhigherstrm may be rrcluired for Inw pergcibilky�orforpmection ' gth against eotrosion'of cmbMdcj items or frecsin and $cawatcr_ g wing ('fables 19=A-2). . ?Fnz lan that has been dttcrmir-d by test or service tceotd to improve sulfate trsistan� when in bdsiing TFJ= V ccmrnL turd concrete cors- 2-264