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Home My WebLink AboutPD 2021-0019; SPEER RESIDENCE; ADDENDUM GEOTECHNICAL PLAN REVIEW; 2021-10-08I 17L' GEOTECHNICAL SOLUTIONS, INC. Consulting Geotechnical Engineers 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 760-602-7815 smsgeosol.incgmai1.com Project No. GI-20-09-136 October 8, 2021 I Mr. Jeff Speer I 16325 Alamo Canyon Road Santa Clarita, California 91387 I Addendum Geotechnical Plan Review, Proposed Residential Redevelopment, 3342 Donna Drive, Carlsbad, California (Project ID: GR2021-0014/PD2021-0019) Revised plans for the above-referenced redevelopment project were provided to us for review and comments. We understand constraints associated with the public easement disallow encroachments I for reconstruction or structural support of the existing failing transition retaining wall that marks the western margins of the level building pad, as recommended in the project prior pertinent geotechnical reports. Revised plans now propose a new retaining wall roughly 6 feet away from the I existing wall (along the eastern edge of easement) and backfihling between the two retaining walls with compacted fills creating a 2:1 maximum gradient backfill slope. The new retaining wall and compacted backfill mass are intended to leave the existing wall in-place, while enhancing its stability I without major reconstruction and/or shoring activities within the public easement boundaries. The new wall will also be incorporated onto the new pool/spa designs and construction, where it occurs. An updated Geotechnical Map, showing pertinent site conditions with an included Architectural Cross-Section, ARCH-ARCH', is attached herein as Figure 1. Updated Geologic Cross-Sections I A-A' and B-B' are attached as Figures 2 and 3. A revised Typical Detail is included, as Figure 4. Reference is also made to the following reports prepared by this office in support of this project: I A. "Geotechnical Grading Plan Review Update and Response to Third Party Review Comments, Proposed Residential Redevelopment, 3342 Donna Drive, Carlsbad, California, (Project ID: GR2021-0014/PD2021-0019)," Project No. GI-20-09-136, dated August 13, I 2021. I B. "Geotechnical Investigation, Proposed Residential Redevelopment, 3342 Donna Drive, Carlsbad, California, (A.P.N. 205-160-62)," Project No. GI-20-09-136, dated October 13, 2020. I I Addendum Geotechnical Plan Review October 6,2021 I Proposed Residential Redevelopment, 3342 Donna Drive, Carlsbad, California Page 2 The referenced reports are on file with our office and copies can be obtained upon request. I Based on our review, the proposed new retaining wall construction and backfihling between the two' retaining walls to a 2:1 slope configuration along the western property margin for enhancing the I stability Of the exis:ting wall, as shown on the attached drawing and substantially as proposed, is feasible from, a geotechnical viewpoint. The following comments, however, are appropriate and should be considered in the project designs and implemented during the construction phase, as I applicable and where appropriate. All conclusions and recommendations provided in the referenced reports will also remain valid, unless otherwise specifically amended or superseded below: I I. The new wall should be designed for a 2:1 sloping:'backfihl 'conditIon (65 pef EFP, also see Referenced .B report), and provided with a minimum two courses free-board for disallowing slope face:materials impacting the lower pool/improvement surfaces. I 2. Passive resistance of the existing wall should be considered as an additional 'active pressure on the new wall. Additional surcharging due of the existing wall foundations loading on the I new wall should also be considered by the project design consultant, as 'applicable. The new wall should be provided with a well constructed back drainage system (see Figure I 14 of Referenced B report). Backfill materials should consist ofgood quality clean sandy granular (SM/S W) import soils adequately processed, moisture conditioned at approximately 2%'above.the' optimum levels, placed in thin (6 to 8 inches) horizontal lifts and mechanically compacted at least 95% compaction level (based on ASTM 157) Out to the slope face. Compaction testing will be. required to, confirm adequate compaction levels throughout, .5. The finished slope face should be planted soon after completion of grading. Unprotected slope faces will be subject to severe erosion and shall not be allowed Over-watering of the slope faces should also not, be allowed. Only the amount of water to sustain vegetation should be 'provided.. In order to 'further" enhance graded slopes surficial and finish face stability, and promote growth of vegetation cover, a synthetic type slope face reinfOrcement mat (such as a LandlockTRM..or similar products) should be provided. Planting large trees between the two walls shall be avoided. A qualified landscape architect should be consulted in this regard. The new wall transitioning from thó swimming pool areas continuing onto either side should be adequately considered and accurately detailed on the project construction plans. The proposed western margin new wall construction shall. be properly considered .in the I proposed pool and spa designs and construction. The pool.design/build contractor shall be provided with the project pertinent reports' and design. plans/cross-sections for properly I I Addendum Geotechnical Plan Review October 6, 2021 Proposed Residential Redevelopment, 3342 Donna Drive, Carlsbad, California Page 3 incorporating pertinent design parameters and recommendations to his/her designs. Bearing soils undermining below a 2:1 projected line influence zone and surcharging from adjacent foundations are considered the most significant concern. We understand considerations are being given to extend the new wall foundation under the entire pool/spa bottom or incorporate the new wall as a part of the pool/spa structures. LIMITATIONS This geotechnical plan review is not a "Plan Check Review" and does not relieve the responsibility of the project design consultant(s) and contractor(s) to get completely familiarized with the requirements of the project soil report(s) and fully incorporate its recommendations into the project design, plans and construction works, where appropriate, and as applicable. Our review and comments are for general geotechnical conformance of the project plans with the intent of the project soil reports and design recommendations. Review of structural and civil engineering calculations, architectural intent and structural and civil engineering design modeling and basis, verification of set back requirements, easements and right-of-ways, as well as code, city and county compliance are beyond geotechnical engineering services. It is the owner's or his (her) representative's responsibility to provide copies of all pertinent soil report(s), updates, addendums and plan review letters to respective design consultant(s), and general contractor and his (her) subcontractor(s) for full compliance. This opportunity to be of service again is sincerely appreciated. Should any questions arise I concerning this report, please do not hesitate to contact this office. Reference to our Project: GI-20- 09-136 will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. lNlGeotechnical Solutions, Inc. I S. Shariat 4G #2885 Distribution: Addressee (3, e-mail) Christensen Engineering (e-mail) bogdancolega-la.com zaid@colega-la.com 5M5 GEOTECHNICAL SOLUTIONS, INC. [1 I U U I I I I I I I I I LOT S PN 167464-08.00 ADDI& 3436 SEACAEBT DR rw 7771 GEOTECHNICAL MAP 3342 DONNA DRIVE, CARLBAD, CA SCALE: F'= 20' I 01 20' New Retaining Wall (By Others, / Under a Separate Report) 'm Arch :*\/ Legend r Proposed Building Location Geologic Cross Section Approximate Location of Boring Approximate ' Geologic Contact tat Undocumented Fill Qvop Very Old Paralic Deposits Approx. Top of 1:1 Temp. Backcut Slope ARCHITECTURAL CROSS SECTION ARCH - ARCH' SCALE: 1/16" = 1' S DONN47kch' SMSGEOTECHNICAL SOLUTIONS INC 5931 Sea Lion Place, Suite 109 - Carlsbad, CA 92010 Project Number: GI-20-09-136 Figure Number: 1 UPDATED GEOLOGIC CROSS-SECTION A-A' 3342 DONNA DRIVE, CARLSBAD, CA SCALE: l"lO' I 0' 10' Legend L Proposed Building Existing Topography Location Boring Location Geologic Contact U Approximated Approximated Groundwater Uaf Artifical Fill Very Moist/Wet Zone Qvop I Very Old Paralic Deposits T.D. Time of Drilling £ al 280 275 270 265 260 255 Proposed Second Floor Proposed First Floor Existing Retaining Walls (To Be Removed) B2 ::: :Jj:jtJ:1: Proposed Driveway — - -. Proposed Grade Existing PL Retaining Wall Proposed Max. Ease ent(?) 2:1 Slope - Existing Grade Proposed Wall 2 G.W. at 8' .'?. T.D. at 10' 245 ? 240 T.D. at 10' Very Old Paralic Deposits (Qvop) - T.D. at 19' SMS GEOTECHNICAL SOLUTIONS INC Project Number: GI-20-09-136 5931 Sea Lion Place, Suite 109 Figure Number: 2 Carlsbad, CA 92010 UPDATED GEOLOGIC CROSS-SECTION B-B 1 3342 DONNA DRIVE, CARLSBAD, CA SCALE: 1"- 10' 1 1 0' 10' Legend - L I Proposed Building - Existing Topography Location Boring Location -. • Geologic Contact Approximated pproximated 2.. Groundwater [ Uaf Artifical Fill Very Moist/Wet Zone Qvop Very Old Paralic Deposits T.D. Time of Drilling 280 Proposed Second Floor 275 270— r - - PL I I 265 - Proposed : Existing Residence Proposed First Floor /Wall I B-2 / B-3 (Projected) 260- - --- - Artifical Fill (Uaf) - -------------------- 255— I Proposed Basement 250— - - T.D. at 10'in B-2 Very Old Paralic Deposits (Qvop) 245 - L T.D.atl9'inB-3 240 Existing Retaining Wall (To Be Removed) /Proposed Grade Existing Grade PL SMS GEOTECENICAL SOLUTIONS INC 5931 Sea Lion Place, Suite 109 Carlsbad, CA 92010 Project Number: GI-20-09-136 Figure Number: 3 PL Easement(?) -I Waterproofing Per Project Waterproofing Consultant Proposed Wall Pr opodGrsde ' / Existing Grade '77JI - -' ' mm. ' - ack Drain Btm. of OX G.W. at 8' 7 ,' Proposed (Typ.) (Typ.) Benches 1L,' Walls Level Back Drain (Typ.) Temporary Excavation Slope Very Old Paralic Deposits (Qvop) TYPICAL DETAIL SCHEMATIC AND CONCEPTUAL ONLY SCALE. 1" - 10' 0' 10' 280 Proposed Second Floor I 275 — I I Protect Off Site Improvement During Excay. and Grading. I 270 - Temp. Shoring May be Required Based on Field/GW Condition and Should be Expected. 265— Proposed First Floor Existing Retaining Walls (To Be Removed) 260 - PL - - - BasementProposed - - - - - - 255— Proposed Driveway - - - - -. T.D. at 10' -- - 245 B. of OX. - Composite/Crushed Rock Blanket Underdrain (I'r.) " Min 15' Keyway may be Necessary as Directed in Field (See Report) 240 - "1_, Temporary Excavation Slope A' Note: Dewater as Necessary Fills/Backfihls Placed in Potential Groundwater Saturation/Inundation Zones Shall Be Crnpac1cd tO Mm Compaction I evels Per ASTM D!55711. SMS GEOTECIINICAL SOLUTIONS INC Project Number: GI-20-09-136 5931 Sea Lion Place, Suite 109 Figure Number: 4 Carlsbad, CA 92010