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Home My WebLink AboutCDP 2019-0009; AKIN RESIDENCE; RESPONSE TO THIRD-PARTY REVIEWER; 2020-04-24-... -... - .. - - - -... .. - -... - - -.. ---... ---- Geotechnical Exploration, Inc . SOIL AND FOUNDATION ENGINEERING • GROUNDWATER • ENGINEERING GEOLOGY 24 April 2020 Sadri and Rose Akin 8839 San Badger Way Elk Grove, CA 95624 Job No. 19-12322 Subject: Response to Third-Party Reviewer Akin Residence Project 3290 Carlsbad Boulevard Carlsbad, California Dear Mr. and Mrs. Akin: As requested, and as required by the City of Carlsbad third-party geotechnical reviewer, Hetherington Engineering, Inc., in a letter dated February 18, 2020, we herein respond to the review comments. The third-party reviewer has reviewed our "Report of Preliminary Geotechnical Investigation, "for the subject project, dated July 3, 2019, and a set of grading plans "Grading Plans for Akin Residence Project" by Christensen Engineering and Surveying, revise date February 15, 2017 (5 sheets). 1. REVIEW COMMENTS OF GEOTECHNICAL REPORT The consultant should provide an updated geotechnical report addressing the plans, and provide updated grading and foundation recommendations consistent with the 2019 California Building Code and ASCE 7-16. GEi Response: This document constitutes the updated geotechnical report addressing the grading plans and the required updated grading and foundation recommendations consistent with the 2019 California Building Code and ASCE 7-16 The reviewed grading plans revised dated February 15, 2017 in our opinion are in compliance with the grading recommendations presented in our geotechnical report dated July 3, 2019. The grading recommendations presented in that report remain valid in this update report. Regarding the foundation recommendations, the only report updated information that is 7420 TRADE STREET'• SAN DIEGO, CA. 92121 • (858) 549-7222 • FAX: (858) 549-1604 • EMAIL: geotech@gel-sd.com - - -- - --- --- - ""' -.... - -... .. - ... -..... ... -- Akin Residence Project Carlsbad, California Job No. 19-12322 Page 2 2. 3. 4. 5. required is the ASCE 7-16 seismic values needed for foundation design. Those updated values are presented in the table below for site soil type D .. TABLE I Mapped Spectral Acceleration Values and Design Parameters Ss Fa Sms 1.123 1.051 1.90 1.180 The consultant should review the project grading and foundation plans, provide any additional geotechnical recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations provided in the geotechnical report. GEI Response: We have reviewed the project grading plans (5 sheets) by Christiansen Engineering and Surveying, with revision date February 15, 2017, and found them to be in compliance with the recommendations of our geotechnical report dated July 3, 2019. We have not reviewed the foundation plans since they were not available for our review. After we review them, we will issue a compliance letter. The consultant should provide an updated plot plan utilizing the latest grading plan for the project. GEI Response: We have included an updated Plot Plan utilizing the latest grading plan for the project, (attached as Appendix A). The consultant should provide the results of the particles smaller than No.200 sieve laboratory test results . GEI Response: In the boring log for HP-2 of our geotechnical report dated July 2019, we included the Sieve No.200 results which yielded 23 and 25 percent passing the sieve No.200 of soil samples at 1.5' and 3' from ground surface respectively. The consultant should provide a statement regarding the impact of the proposed grading and construction on adjacent properties and improvements . at - - - "" - -... - ... -- --... - -.... - - ----- - - Akin Residence Project Carlsbad, California Job No. 19-12322 Page 3 6. 7. 8. GEi Response: It is our opinion that the proposed grading and construction should not have any impact, from the geotechnical engineering viewpoint, on the adjacent properties. The consultant should provide a list of recommended geotechnical observations and testing to be performed during grading and construction. GEi Response: During grading we should: observe the bottom of the excavation of removed soils to consist of firm soils, perform field density tests of placed and compacted soils at least every 2 feet in thickness, verify the adequacy of soil moisture content and relative compaction, obtain and verify the maximum dry density of the soils being placed as fill material, and verify the adequacy of imported soils by performing sieve tests and expansion index tests as well as maximum dry density and optimum moisture tests. In addition, we should verify soil moisture content and compaction of on-site soils being used for trench and retaining wall backfill, verify adequacy and moisture content of subgrade soils to receive pavement or flatwork improvements, in public street areas obtain soil samples and perform R-value tests in areas to receive pavement to verify adequacy of pavement cross section, verify adequacy of compaction of asphalt concrete, verify adequacy of grain size of base material as well as determination of maximum dry density in the laboratory as well as relative compaction in the field; and observe the bottom of foundation excavations and evaluate soil compaction adequacy of bearing soils. The consultant should provide the site risk category and seismic design category. GEi Response: The site risk category is II and the seismic design category is D. The consultant should provide a I ist of references utilized in preparation of this report. GEi Response: The list of references used in this response letter is as follows: NAVFAC Design Manual 7.01, Revalidated September 1986; Foundation Analysis and Design, by Joseph E. Bowles, 5th Edition, 1996, McGraw Hill Companies; Geotechnical Engineering Techniques and Practices, by Roy E. Hunt, McGraw Hill Company, 1986; Geotechnical and Geo-environmental Engineering Handbook, edited by R. Kerry Rowe; Kluwer Academic Publishers, 2001; California Building Code, 2019 Edition. - - -... .. -... -.. --.. .. "" ---... - ... - - - -- Akin Residence Project Carlsbad, California Job No. 19-12322 Page 4 9 . The consultant should provide recommendations for temporary excavations. GEi Response: Temporary excavations during grading are anticipated not to exceed 4 ft. Most of those excavations are going to be in the range of 3 ft. These excavations will not require shoring and can be made vertical. During construction, the excavations are anticipated to be in firm recompacted soils and formational soil and not to exceed 4 ft. A vertical cut up to 3 ft can be made in the lower part of the excavation, and at 1/2 to 1 (H to V) in the remaining upper part. During grading, in areas close to property lines, the grading excavations up to 4 ft in depth can be made in ABCD slot cuts and backfilling in the same fashion, where the cut and backfill segments should not exceed 8 ft in length. If excavations during grading do not exceed 3 ft, they can be made vertical. The contractor shall comply with OSHA Guidelines, in general. 10. The consultant should provide a statement that the foundation and slab recommendations (expansive soils) are consistent with the requirements of the Section 1808.6, 2019 California Building Code or revise accordingly GEi Response: Our recommendations in our July 3, 2019 report for the design of foundations and slab on grade are corresponding to soils ranging from very low to low expansive expansion classification. Those recommendations remain applicable. 11. The recommendations for allowable vertical foundation pressure, lateral bearing pressure, and lateral sliding resistant exceed the presumptive values for sandy soils included in the 2019 California Building Code and no strength testing was performed. The consultant should provide the basis for the recommended values or revise the recommended values accordingly. GEI Response: Based on our experience and a chart provided by NAVFAC Manual, Figure 7, page 7.1-149, we assigned properly compacted on-site silty sands a conservative value of 32 degrees and a cohesion value of 50 psf. We also used a soil total unit weight of 120 pcf to calculate the ultimate and allowable soil bearing capacity for footings embedded at least 18 inches in depth and a minimum width of 12 inches. The ultimate soil bearing capacity was calculated based on bearing capacity factors by Meyerhoff, as presented in Foundations Analysis and Design, by Joseph E. Bowles, 5th edition, page 223. The calculated ultimate bearing capacity is 7,761.5 psf. With a factor of safety of 3, we recommend an allowable soil bearing capacity for the shallow foundations of 2,500 psf for an acceptable allowable settlement. D - - - -... - -.. -.. -... ---... -.. - - -.. -.. - - -... -... Akin Residence Project Carlsbad, California Job No. 19-12322 Page 5 12 . To calculate the allowable passive resistance, we used a factor of safety of 1.5 applied to the ultimate passive resistance. The passive resistance was calculated from the equation PP = yh tan ( 45 + ~)2 + 2c tan ( 45 + ~), where y is the soil unit weight in pcf, h is the depth of footing in feet (we used 1 foot rather than 1 ½ for calculation purposes), and <p is the soil friction angle in degrees. The calculated ultimate soil passive resistance value yielded 570 pcf. With a factor of safety of 1.5, the value is 380 pcf. We recommended 300 pcf in our report . Regarding the allowable friction coefficient, the ultimate value of the soil is tan <p, which for 32 degrees is 0.62. After applying a factor of safety of 1.5, the allowable friction coefficient is 0.42; we recommended 0.40 in our report . The consultant should provide the basis for the recommended active and at rest design lateral soil loads provided for retaining walls. GEi Response: The recommended soil active equivalent fluid pressure is based on the compacted soil friction angle of 32 degrees and a soil unit weight 2 of 120 pcf. By using the active pressure coefficient Ka= tan ( 45 -~) , the value of active pressure coefficient is 0.307 and the assigned soil weight of properly compacted soil (120 pcf), the active pressure equivalent fluid weight is calculated as 36.87 pcf, which we rounded up to 38 pcf. The at rest pressure coefficient is based on Ko=(l-sincp), that is Ko=l-0.530=0.47. The at rest lateral soil pressure is equal to 0.47 x 120=56.4, which we rounded down to 56 pcf. If you have any questions regarding this letter, please contact our office. Reference to our Job No. 19-12322 will help expedite a response to your inquiry. Respectfully submitted, R.C. . Senior Geo Leslie D. Reed, President C.E.G. 999/P.G. 3301 - - - - "" APPENDIX A .. - -... -... - --- - - -------,.,. 4~ji -... ~ -- C a: ! .J :) 0 m C ~ CJ) .J a: ~ 7g.12322-p3.a/ l ~ I;.._. I ~ ... ~,, EXISTWATER WTTHe,/fr'MEl ~~~= ~ ~ ABBREVATIONS FYSB .•.. ____ ..... FRONT YARD SETBACK SYSS.-•. ~ ........ SJOE YARD SETBACK ~::::·::::::::::~~~~~li~Ol. NOTET REFERENCE: This Pk>t Plan is not to be used for legaJ purposes.Locationsanddimensionsareapproximate. Actual property dimensions and kications of utilities may be obtained from the Approved Building Plans orthe"As-Built"GradingPlans. REFERENCE: This Plot Plan was ptBPalBd from an exkiing undet.ed GRADING PLAN prowded by CHRISTENSON ENGINEERING & SURVEYING and from on-sle field reconnaissancepenormedbyGEI. THE TIJRF BLOCK IN TI-IE FRONT YARD SETBACK AREA SHAU. BE PERMANENTI. Y MAINTAINED, TO THE SATISFACTION OF ntE CfTY PlMNER, ANO MAY NOT BE REPI..ACED WITH CONCRETE PA.YEAS OR OTH§_R_ftA~f! MAlEIIAl..,_ F1RU: CHllSTENSEN £NGIHEIRINC 4 St.R~nHC ADDR£SS: 7MB SI \fRI<W A.l.f'Mf' SZE ·c CTY,STATC:~ TElfffiOHE,~ ... ~ ~ UNAIJTHORl2ED Oi.AHGES & USES CAUTlON:TheEnglnNrp,wpe.rtng.,_.pler,awWnatt.~for. orbbletor,unauthorlndc:hangatootUMSoftheMplans. MchangN tohpllnsmUltbelowrtlingandmuetbeac:,pn:,vedt,ythep,~of .......... 8~ ---"'m""rOH""r'""K.'CHRJ"°""STr""'N"S£N.,--"-'"' R.C.£. N0.:,_.,54!!>0"'21-,---,--,,------- R!GtSTRATIDH !XPIRATION DA7E:_,_f2-=c-Jo<.cl-'-"2Q"'-'>1 __ _ 1 .. ..,..., .... I I I I I I I I APPIJCABLE BMPs FROM STANDAAD PROJECT REQUIREMENTS CHECKUST PROTECT TRASH STORAGE AREAS FROM RAINFAU. Rl.NOFF ANO WIND DtSPERSAL A.. LANDSCAPE/OUTDOOR PESTICIOE USE B. RERJSE AREA SD-3 MINIMIZE IMPEfMOUS AREA MNIMIZE SotL COMPACTION IMPERVIOUS AREA CMSPERSION LANDSCAPING WITH NATIVE OA DROUGHT TOLERANT SPECIES 0 SCALE: 1" = 10' Scale: l" = 10' (approximate) ~~~M~-::-'~i;grrE LANOSCAPE/OIJTDOOA PESTIQDE USE WIU. BE LIMITED OAOUGHT TOLERANT SPECIES OF PLANTINO Will. BE UTILIZED NJ SHOWN ON SEPARATE LANDSCAPE Pl.AN TRASH CONTAINER WILL BE STORED IN OAAAOES PLOT PLAN LEGEND - Proposed Akin Residence 5290 Carlsbad Boulevard Carlsbad, CA. Figure No. II Job No. 19-12322 ~ Geotechnical ~1'"11 Exploration, Inc. ~ June2019 ~ (Updated April 2020) Approximate Location of Existing Structure Approximate Location of Proposed Structure iill Approximate Location HP.3 of Exploratory Handpit Qaf Artificial Fill Qop Quaternary Old Paralic Deposits (units 6-7) 6-7 "AS BUILT" Approximate Location of GeologlcCl51'l=-RC[__ EXP--- RE~ate Location of Geop~~ical Traverses OATt ~ t-----+--+-----------t----+--+--t--;CTTII c1Tlc£lo.~~~~~DJl::r] 1----1'----t-----------+---t--+---I,--~ i<>IUl>ING ?W'S FOR: AKIN RESIDENCE ~2020-0QQ_~ GfiAOING PLAN SHEET 1----lt----t-----------+---+--~~-~ IAPPRO~ JASON s. GELOERT QTY ENCl'EER RCE 63912 EXPIRES 9/J0/20 DA.T! REVISION DESCRIPTION r I·· I om '"'""-1 IO\\t< BY: ..£8lL__II PR&tct NO. A N NO. -~~~ ---~ --.............~~ ~~ === COP2019-0009 52:2-SA