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Home My WebLink AboutCUP 2017-0008; OAKMONT OF CARLSBAD; RESPONSE TO THIRD-PARTY GEOTECHNICAL REVIEW COMMENTS; 2019-10-30RECORD COPY vk~~jm_' _tIqlt Initial Date RESPONSE TO THIRD-PARTY GEOTECHNICAL REVIEW COMMENTS OAKMONT OF CARLSBAD CARLSBAD OAKS NORTH BUSINESS PARK - LOT I CU P201 7-0081GR201 9-001 3IDWG 517-4A CARLSBAD, CALIFORNIA OC T O 2019 LANID tLO )7%4ENT PREPARED FOR OAKMONT SENIOR LIVING WINDSOR, CALIFORNIA OCTOBER 30, 2019 PROJECT NO. 06442-32-29 GEOCON INCORPORATED GEOTECHNICAL . ENVIRONMENTAL U MATERIALS Project No. 06442-32-29 October 30, 2019 Oakmont Senior Living 9240 Old Redwood Highway, Suite 200 Windsor, California 95492 Attention: Mr. Gregg Wanke Subject: RESPONSE TO THIRD-PARTY GEOTECHNICAL REVIEW COMMENTS OAKMONT OF CARLSBAD CARLSBAD OAKS NORTH BUSINESS PARK - LOT 1 CUP20I7-008/GR2019-00 13/DWG 5174A CARLSBAD, CALIFORNIA References: 1. Update Geotechnical Report, Oak'nont of Carlsbad, Carlsbad Oaks North Business Park - Lot.1, Carlsbad, California, prepared by Geocon Incorporated, dated May 20, 2019 (Project No. 06442-32-29). Grading Plans For: Oakmont of Carlsbad, Lot 1 of Tract No. 14926, by Alliance Land Planning & Engineering, Inc., dated September 3, 2019. Structural Plans, Oakmont of Carlsbad, Faraday Avenue, Carlsbad, California, by Structural Edge, Revision 2 dated September 6, 2019 (Project No. SE 18-386). Plan Review, Oakmont of Carlsbad, Carlsbad Oaks North Business Park - Lot 1, Carlsbad, California, prepared by Geocon Incorporated, dated September 20, 2019 (Project No. 06442-32-29). Dear Mr. Wanke: This correspondence has been prepared to respond to comments provided in a third-party geotechnical review prepared by Hetherington Engineering Inc, dated October 9, 2019. The comments along with our responses are presented below. Comment 1: The consultant should review the project grading, foundation, and improvement plans, provide any additional geotechnical analyses/recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations Response: We have reviewed Reference Nos. 2 and 3 to determine if the plans and details have been prepared in substantial conformance with the recommendations presented in our referenced geotechnical report (Reference No. 1). 6960 Flanders Drive 8 Son Diego, California 92121.2974 • Telephone 858.558.6900 0 Fax 858.558.6159 Based upon our review of the project plans and the information contained within the geotechnical report, it is the opinion of Geocon Incorporated that the plans and details have been prepared in substantial conformance with recommendations presented in the geotechnical report. It should be understood that our review was limited to geotechnical aspects of project development and did not include the review of other details on the referenced plan. Geocon Incorporated has no opinion regarding other details found on the referenced plans, structural or otherwise, that do not directly pertain to geotechnical aspects of site development. Comment 2: The Consultant should provide geologic cross-sections utilizing the current grading plan to clearly show (at a minimum): a) existing site topography, b) proposed structures/improvements, c) proposed finish grades, d) geologic contacts, e) geologic structure, j) locations of the subsurface exploration, g) temporary construction slopes, and h) remedial grading, etc. Response: Geologic Cross-Section A-A' has been prepared at the location shown on the Geologic Map, Figure 1. Cross-Section A-A' is presented as Figure 2. The geotechnical information shown on the cross-section was collected during rough grading of the sheet-graded pad. Comment 3: The consultant should provide estimated depths of remedial grading removals. Response: The site was previously graded in 2006 to achieve the current sheet-graded elevations. Grading recommendations were provided in Section 6.5 of Reference No. 1. As such, during planned excavations for the subterranean garages on Buildings I and 2, cut-fill transitions will be exposed. The bedrock portion of the of the cut-fill transition should be over-excavated (undercut) a minimum of 3 feet below finish pad grade or at least 2 feet below the lowest foundation element, whichever is deeper, and replaced with low to medium expansive soil fill. No remedial grading is expected for Building 3, except prior to placing additional fill, the ground surface should be scarified, moisture conditioned, and compacted to at least 90 percent of the applicable maximum dry density at slightly over optimum moisture content. Comment 4: The consultant should provide recommendations for temporary slopes/excavations. Response: Temporary slopes should be excavated in accordance with current OSHA guidelines. It is the responsibility of the contractor to ensure that all excavations and trenches are properly shored and maintained in accordance with applicable OSHA rules and regulations in order to maintain safety and maintain the stability of adjacent existing improvements. The contractor's "competent person" should evaluate the soil conditions during the excavations and make adjustments to the soil types as deemed necessary. For preliminary planning, compacted fill should be considered a Type B soil, or Type C if groundwater of seepage is encountered, and the bedrock should be considered a Type A soil, or Type B if groundwater or seepage is encountered. In accordance with OSHA guidelines, Type B soil may be excavated at 1:1 (H:V) up to 20 feet high, and Type A soil may be excavated at 3h:1 (H:V) up to 20 feet high. Project No. 06442-32-29 -2 - October 30, 2019 Comment S. Foundation and slab design criteria for expansive soils should be consistent with Section 1808.6 of the 2016 California Building Code. The Consultant should update foundation recommendations, as necessary. Response: The foundation and concrete slab-on-grade recommendations presented in Reference No. I are considered appropriate for low to medium expansive soils in accordance with the 2016 California Building Code. Comment 6: The consultant should address impacts to adjacent property and improvements as a result of site grading and construction. Response: The grading and construction of the subject site should have no impact on adjacent properties and improvements. Comment 7: The Consultant should provide the site seismic design category. Response: As stated in Section 6.8.9 of Reference No. 1, the Structural Engineer should determine the Seismic Design Category for the project in accordance with Section 1613.5 of the 2016 CBC or Section 11.6 of ASCE 7-10. Based on this, a Seismic Design Category of D was assigned. Comment 8: The Consultant should provide a list of recommended testing/observation during grading and construction. Response: A complete list of requested special inspections in accordance with the 2015 IBC 1705.6 was provided in Reference No. 3 and the requested soil inspections are summarized below: SOILS CONSTRUCTION (IBC 1705.6) Item Continuous Periodic Verify Subgrade Is Adequate To Achieve Design x Bearing Capacity Verify Excavations Extend To Proper Depth And Material Verify That Subgrade Has Been Appropriately x Prepared Prior To Placing Compacted Fill Perform Classification And Testing Of Compacted Fill Materials Verify Proper Materials, Densities, And Lift Thicknesses During Placement And Compaction Comment 9: The Consultant has provided preliminary asphalt concrete pavement design recommendations. Final pavement recommendations should be based on R-value testing of the subgrade soils at the completion ofgrading. Response: Acknowledged. Project No. 06442-32-29 - 3 - October 30, 2019 If there are any questions regarding this correspondence, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON iNCORPORATED f1f \J Trevor E. Myers coo RCE 63773 TEM:DBE:dmc IV (email) Addressee (email) Alliance Land Planning and Engineering, Inc. Attention: Ms. Ashley Holland 11. David B. Evan X. CEO 1860 DAVID B. EVANS NO. 1860 CERTIFIED ENGINEERING GEOLOGIST. * Project No. 06442-32-29 -4- October 30, 2019 I Qu o o,/vbsvt p,1000 .00 0 GRAPHIC SCALE O'Do "Do, J6x24) SCALE 0 1"=30'(on 9 -7 x \ Is ii-- / 0 -21 253 + - 0 - - - - \ \ 0 - -_-------- \\ __ - - - - 7 0 \\ \ \ ( / N 0 0 —/---_ ---- \ \ \ \c. S JS•• __ 0 / •• / o F \ \ / 0 0 - o \\ - 00 / o 0 0 _ - GEOCON LEGEND \ \ -_-- -a- - - - - - - - Qc ........ COMPACTED FILL \ \ \ - Quc....COMPACTED FILL IN UNDERCUT AREA \ \\ \ \ \ \ \ - \ \ Kp....POINT LOMA FORMATION NNN. p\IENUE - - _- (Dotted Where Buried) - - - - - FAD - -_- APPROX. LOCATION OF GEOLOGIC CONTACT GEOLOGIC MAP - - - - - — _- (Queried Where Uncertain) OAKMONT OF CARLSBAD - - - —\-- APPROX LOCATION OF PERMEABILITY TEST CARLSBAD OAKS NORTH BUSINESS PARK LOT 1 - — - F3281 - - - APPROX. ELEVATION (Feet) AT BASE OF FILL CARLSBAD, CALIFORNIA - - - - __ DATE (T SCALE 1" = 30' 10 - 30 - 2 - - A A.APPROX. LOCATION OF GEOLOGIC CROSS INCORPORATED __- SECTION GEOTECHNICAL• ENVIRONMENTAL UMATERIALS PROJECT NO. - 32-29 Plottecl:I 0/29/2019 1 1:33AM I By:ALVIN LADRILLONO I File Location:Y:\PROJECTS\06442-32-29 (Oakmont of Carlsbad)\SHEETS\06442-32-29 Goo Map.dwg -290 -j 260 z 0 -200 -170 A 320—i 290 - a 260 z 0 I- > w _j 230- w 200- 170- DISTANCE GEOLOGIC CROSS-SECTION A-A' SCALE: 1" = 30 (Vert. = Horiz.) GEOCON LEGEND Q cf....COMPACTED FILL Kp ........ POINT LOMA FORMATION QUC....COMPACTED FILL IN UNDERCUT AREA APPROX. LOCATION OF GEOLOGIC CONTACT Plotted:10/29/2019 2:30PM I By:ALVIN LADRILLONO I File Localion:Y:\PROJECTS\06442-32-29 (Oakmont of Cerlsbad)\SHEETS\06442-32-29 XSection.dwg