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BRES2015-0391 Geotechnical UpdatesSladden Engineering .:-':.r 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-I369 450 Egan Avenue, Beaumont, CA 92223 (95I) 845-7743 Fax (951) 845-8863 800 E. Florida Avenue, Hemet, CA. 92543 (951) 766-8777 Fax (951) 766-8778 August 27, 2015 Project No. 544-15206 15-08-353 Discovery Builders California, Inc. 80-955 Avenue 52 La Quinta, California 92253 Subject: Geoted-inical Update OCT 09 2015 Project: Proposed Custom Residence 81-382 Amundson Avenue By The Madison Club — Lot 23B La Quinta, California Ref: Geotechnical Investigation Report prepared by SIadden 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 81-382 Amundson Avenue within the Madison 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 subject Iot 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. Sladden Engineering ►v►vw.Sladdenengineering. com 115} Geer August 27, 2015 -2- Project No. 544-15206 15-08-353 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 0.48 times the normal dead Ioad 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 structures. The 2013 CBC Seismic Design Parameters are summarized below. Risk Category (Table 1.5-1): I/H/M Site Class (Table 1613.32): D Ss (Figure 1613.3.1):1.516g S1 (Figure 1613.3.1): 0.71lg Fa (Table 1613.3.3(1)):1.0 Fv (Table 1613.5.3(2)):1.5 Sms (Equation 16-37 (Fa X Ss)): 1.5168 Smi (Equation 16-38 (Fv X SIj):1.066g SDS (Equation 16-39 (2/3 X Sms)):1.011g SDI (Equation 16-40 (2/3 X Sm1)): 0.7118 Seismic Design Category: D Sladden Engineering August 27, 2015 -3- Project No. 544-15206 15-08-353 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 Brett L. Anderson E r: =°' r' Principal Engineer SER/nh�' / is Copies: 4/ Discovery Builders California, Inc. Sladden Engineering ISOSr-35� 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 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 measures) no or; (b) the criterion is considered insignificant and explicitly so stated. Y s . Bio Criterion ❑ Foundation criteria based upon bearing capacity of natural or compacted soil. C3 Foundation criteria to mitigate the effects of expansive soils. 0 Foundation criteria based upon bearing capacity of natural or compacted soil. ❑ Foundation criteria to mitigate the effects of liquefaction. - Ca 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 strength. ❑ Foundation criteria to mitigate expected total and differential settlem_ e ' t. Any "No" answers to the -above checklist should be noted as specific required corrections. E3 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, CA. 92543 (951) 766-8777 Fax (951) 766-8778 August 27,2015 Discovery Builders California, Inc. 80-955 Avenue 52 La Quinta, California 92253 Project No. 544-15206 15-08-353 Subject: Geotechnical Update CITY ®F L1 QUI NTA BUILDING & SAFETY DEPT. Project: Proposed Custom Residence A P P IIV E 81-382 Amundson Avenue FOR CONS UCTION The Madison Club — Lot 23B La Quinta, California DATE J ZZ Ref: Geotechnical Investigation Report prepared by Sladden 01neering dated January 28,2005; Project No. 5444810, 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 81-382 Amundson Avenue within the Madison 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 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. Sladden Engineering www.Sladdenengineering.com August 27, 2015 -2- Project No. 544-15206 15-08-353 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 0.48 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 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):1.516g S1 (Figure 1613.3.1): 0.71lg Fa (Table 1613.3.3(1)):1.0 Fv (Table 1613.5.3(2)):1.5 Sms (Equation 16-37 {Fa X Ss)): 1.516g Sm1 (Equation 16-38 (Fv X Si)): 1.066g SDS (Equation 16-39 (2/3 X Sms)): 1.0118 SM (Equation 16-40 (2/3 X Sm1)): 0.711g Seismic Design Category: D Sladden Engineering www.Sladdenengineering.com August 27, 2015 -3- Project No. 544-15206 15-08-353 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�CFESS';O�gl i BRETT L. F� ANDERSON C No. C45389 Z Brett L. Anderson Exp. 9130116 rn Principal Engineer p � ENGINEERING � SER/nh F OF CAS-�F�, Copies: 4/ Discovery Builders California, Inc. Sladden Engineering www.Sladdenengineering.com /S--off-3Sj 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 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. Ys . No Criterion C3 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 criteria to mitigate.the effects of liquefaction. ❑ Foundation criteria to mitigate the effects of seismically induced differential settlement. O Foundation criteria 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 corrections. gladden 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, CA 92543 (951) 766-8777 Fax (951) 766-8778 September 23, 2015 Discovery Builders California, Inc. 80-955 Avenue 52 La Quinta, California 92253 Project: Proposed Custom Residence 81-382 Amundson Avenue The Madison Club — Lot 23B La Quinta, California Subject: Soluble Sulfate Content Project No. 544-15206 15-09-393 Ref: Geotechnical Update prepared by Sladden Engineering dated August 27, 2015 Project No. 544-15206, Report No. 15-08-353 -As requested, we have sampled the surface soil on the subject lot to determine the soluble sulfate content as it relates to selecting appropriate concrete mix designs. Testing indicates that the site soil is considered potentially with respect to concrete. The testing indicated a soluble sulfate . content of 1000 ppm (0.100 percent) that corresponds with "moderate" exposure category in accordance with Table 3 of ACI 318-08 Chapter 9. Based upon the laboratory test results, sulfate resistant concrete mixes will be necessary for structural concrete in contact with the soil. Structural concrete in contact with the soil should have a minimum compressive strength of 4000 psi and maximum water/cement ratio of 0.50. If you have questions regarding this letter, please contact the undersigned. Respectfully submitted SLADDEN ENGINEERING � p; �3SOp���9 Brett L. AndersonOR Principal Engineer CO ANDERSON J No. 045389 n W Exp. 9130/ ra Letter/clb Club r ENGINEERING Copies: 4 / Addressee �nf cm1 • I Sladden Engineering 6782 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: September 22, 2015 Account No.: 544-15206 Customer: Discovery Builders Location: Madison Club, 81-382 Amundson Avenue, Lot 23B, La Quinta Analytical Report Sulfate Series Soluble Sulfates Soluble Chloride per CA 417 per CA 422 ppm ppm 1000 220 Sulfate 544-15206 092215 TABLE 19=A-2—REQUIREMENTS FOR SPECIAL EXPOSURE CONDITIONS lA1NIMUMf�, MAXIMUM - • NO AL`-WeGW AND . WATER�EMENTTi[OUS UGHYWEIGHT- - MATERIkLS` RATIO; BY.:' AGGREGATECONCgET� EXPOSURE CONOtTION WOGHTlNORAIAL'=WE7GKT• AGGREGATE CONCRETE = =:=Pgl=: Congrete intended to have low permeability when x o.pp6B9•lor MPs exposed to water Concrete exposed toTrcezing and thawing in a moist 0.50 4,000 condition or to deicing chemicals For corrosion protection for reinforced concrete 0.45 4,500 exposed to chlorides from deicing chcmica.1s, salts or brackish:waccr, orspray.from these 'sources' 0.40 5,000 J. TABLE 19-A-3—REQUIREMENTS-FOR CONCRETE EXPOSED TO SULFATE NORMAL-WEIGHT IGG REEIGH GATE AGGREGATE CONCRETE Maxlmum'Water- WATER -SOLUBLE Cemertt(tlous !",'Normal - 'Welght•and SULFATE M6tada1a_ Ratlo; by:. = ,whtwdlght - SULFATE EXPOSURE jSOSj IN SOIL, Weig• ht, •- PEtRGrEINiTTAGEBY SULFATE(SO�)IN n,4aFWelgtit. ' -AggMpate, . concratb,.Pitt WEIGHT Aggregate WATER, ppm CEMERTTYPE Coneretat • 1 • x GZM9'torMPa. Negligible 0.00-0,10 0-150 Mode-mccz, 0.10-0.20 150-1,500 II. IP(MS), LS '0.50• 4,000 (MS) Scvcrc 0.20-2.00 1500-40,000 V 0.45 4,500 Very severe Over 2.00 Over 10,000 V0 p[us .45 4,500 pozzolan3 IA. lowerwa[er-ccrncntitiousmatcrialsratio orhi rsc may belt i for low permeability or Forprotcetion ' ghc (t jkwi 19 against contusion"of cmbEddcd items or Erecring and thawing (table 19=A -A_ 2). Z Seawater_ _ ?Pozzolan that has been determined by cast or Service record to improve sulfate taisiing 7Yp V ccmcnL resistance when us4d in concrete con - 2 -264