Loading...
HomeMy WebLinkAboutCDP 2016-0006; MFD-01; GEOTECHNICAL UPDATE, PROPOSED ARELLANO 4-UNIT APARTMENTS; 2018-03-15Project No. GI-15-12-50 March 15, 2018 Ohms Collaborative Mr. Hector Aramburo 536 Sears A venue San Diego, California 92114 SNS GEOTECHNICAL SOLUTIONS. INC. Consulting Geotechnical Engineers & Geologists --·-··-5931 Sea Lion Place, Suite 109 ll -~··:... ·. . .t' y l Carlsbad, California 920 I 0 .1.'\....:.."-' ~ ~ ·-~ ~ .J Office: 760-602-7815 £Nri-/µ'l£ -~!!,.-smsgeosol.inc@gmail.com TPW::, Date ---· .. ··----·· ··--···-·· -.... LANf'°: :;: \: . , l;': ''. NT E:.r·~u.;·~~'"-· ~~. ~u GEOTECHNICAL UPDATE, PROPOSED ARELLANO 4-UNIT APARTMENTS 2637 JEFFERSON STREET, CARLSBAD, CALIFORNIA Project revised Drainage & BMP Plan (Sheet 2 of2), prepared by Victor Rodriguez-Fernandez, dated September 15, 2017 for the proposed multi-unit residential development at the above-referenced property, were provided to us for an update review and comments. A copy of the revised Drainage & BMP Plan is enclosed herein as Figure I. We are in receipt of the City of Carlsbad "red line" review comments of our report entitled "Revised PICP Construction Procedure Alternative, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad," dated April I 0, 2017 (Reference 2 below). A copy of the City of Carlsbad "red line" review comments is attached with this transmittal as Appendix I. Project property was the subject of a detail surface and subsurface geotechnical study completed by this office in connection with the proposed development. The following reports pertinent to the project development are available and were reviewed as a part of this effort: 1. "Geotechnical Plan Review, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad, California," dated May 8, 2018. 2. "Revised PICP Construction Procedure Alternative, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad," dated April 10, 2017. 3. "Alternative PICP Construction Procedure, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad, California," dated February 14, 2017. 4. "Geotechnical Plan Review Update, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad, California," dated October 24, 2016. Geotechnical Update, Proposed Arellano 4-Unit Apartments 2637 Jefferson Street, Carlsbad, California March 15, 2018 Page2 5. "Geotechnical Investigation, Proposed 3-Story 4-Unit Residence, 2637 Jefferson Street, Carlsbad, California," dated January 11, 2016. The purpose of this effort was to review the project revised Drainage & BMP Plan from a geotechnical engineering viewpoint and confirm its compatibility with the site indicated geotechnical conditions, and provide further information and/or clarifications to the review comments raised by the City of Carlsbad. Updated and amended recommendations consistent with the project revised plans are also provided in the following sections. I. Plan Review & Update Conclusions and Recommendation Revised plans now depict a 6 feet high maximum retaining wall along the western property margins adjacent to the existing wall on the neighboring property (see Figure 1 ). Remaining development schemes remains substantially unchanged. Based on our review, the project revised Drainage & BMP Plans proposes a feasible design from a geotechnical view point, provided the recommendations provided in the referenced reports and amended herein are considered and reflected on the final plans and implemented during the construction phase, where applicable. The following are appropriate: 1. All site development, grading and earthwork recommendations presented in the referenced reports (see References) remain valid except where amended or superseded below. The referenced reports (References I through 5) and this Geotechnical Update report should be noted on, and shall be considered a part of the project Drainage & BMP Plan, and foundation plan and details. 2. All site development works, designs and constructions including excavations, grading, earthworks, and bearing soil preparation should be completed in accordance with Chapter 18 (Soils and Foundations) and Appendix "J" (Grading) of the 2016 California Building Code (CBC), City of Carlsbad Ordinances, the Standard Specifications for Public Works Construction, and the requirements of the referenced reports and this Geotechnical Update report, wherever applicable. 3. Seismic ground motion values were reevaluated as part of this effort in accordance with Chapter 16, Section 1613 of the 2016 California Building Code (CBC) and ASCE 7-10 Standard using the web-based United States Geological Survey (USGS) ground motion calculator. Results are provided in the enclosed summary report, Appendix II. 4. The proposed new western perimeter retaining wall is planned next to the adjacent existing offsite retaining wall on the neighboring property. The following should be considered: a) The new retaining wall should be designed for an additional parking/traffic surcharge Geotechnical Update, Proposed Arellano 4-Unit Apartments 2637 Jefferson Street, Carlsbad, California March 15, 2018 Page3 loading (including trash truck loading associated with trash enclosure, if any) on top of the wall. b) An additional seismic force due to seismic increments of earth pressure should also be considered in the project retaining wall design, as necessary and where applicable. A seismic lateral inverted triangular earth pressure of20 pcf (EFP) acting at 0.6H (His the retained height) above the base of the wall should be considered. Alternatively, seismic loading based on Mononobe-Okake (M-0) coefficients may be considered for seismic force due to seismic increments of earth pressure as follows: Kh = 0.16 Ka= 0.33 Kae= 0.49 The seismic lateral earth pressure should be considered in addition to the specified static earth and surcharge loading pressures. Remaining parameters will remain the same as specified in the referenced reports (Page 18 of Reference 5). c) New wall construction will leave a thin sliver on the order of 6 inches between the face of the new wall and back of the existing offside wall, which will likely fall in and/or be removed during the construction works. The existing offsite retaining wall is also provided with weep holes in the base course for back drainage and hydrostatic pressure relief. The narrow gap between the two walls may be filled-in with %-inch crushed rocks and existing weep holes incorporated into the new construction, provided the appropriate permissions are obtained from the neighboring property owner(s), if necessary. For this purpose, the weep holes in the existing offsite retaining wall should be examined and proper and continued functioning confirmed during the construction. Some cleaning and debris removals from the weep holes may be necessary and should be anticipated. It should be noted that adequate performance ofboth retaining walls and the new parking surfaces above the onsite retaining wall will be dependent on continued free and unobstructed draining of water from behind the walls through the existing weep holes in the offsite retaining wall. Consequently, in our opinion, a management program should be agreed upon with the neighboring property owner(s) to periodically ( at least two times a year) monitor and clean out the weep holes, if necessary. d) The new onsite retaining wall should be provided with a minimum 2 feet section of '4- inch crushed rocks on the backside and weep holes for drainage purposes, as shown on the Retaining Wall Detail on Figure I. Geotechnical Update, Proposed Arellano 4-Unit Apartments 2637 Jefferson Street, Carlsbad, California March 15, 2018 Page4 e) Excavations and new retaining wall construction will create stability concern for the adjacent existing offsite retaining wall to remain. Excavations and new wall construction completed in one-third sections maximum should be considered to minimize potential damages. The neighboring propertyowner(s) should be notified and appropriate permits, if applicable, obtained. Some local bracing support of the existing wall on the neighboring side and perhaps some local repairs may still become necessary and should be anticipated. In our opinion, the existing offsite retaining wall should be surveyed for vertical and horizontal alignment, and existing conditions well documented and photographed prior to excavations for the new wall construction. 5. Testing for site infiltration feasibility condition was not a part of our study. However, project site is underlain by sandy topsoil and Terrace Deposits sands (SM/SP) which typically have modest to good infiltration characteristics. Based on the geotechnical data collected during our work, underlying soil profiles may be characterized as Group B/C hydrologic classification (based on San Diego Hydrology Manual classification). II. Response to The City Review Comments The following clarifications and added information are provided in response to the City of Carlsbad "red line" review comments (see Appendix I). I. The purpose of this transmittal was to provide a Geo technical Update report considering the latest Drainage & Improvement plan (Site Plan), which now includes construction ofa new retaining wall adjacent to the existing wall along the western property line. Additional recommendations for the same are provided herein as necessary. 2. Updated seismic parameters based on the 2016 CBC are provided herein (also see Appendix II). 3. Infiltration properties of the onsite soils based on the available subsurface data and our experience with similar soils in the vicinity of the project site are provided herein. 4. PICP is an acronym for Permeable Interlocking Concrete Pavers. 5. A copy of the "Alternative PICP Construction Procedure, Proposed Arellano 4-Unit Apartments, 2637 Jefferson Street, Carlsbad, California," dated February 14, 2017 is attached to this transmittal as Appendix III for your reference. Geotechnical Update, Proposed Arellano 4-Unit Apartments 2637 Jefferson Street, Carlsbad, California March 15, 2018 Page 5 6. An increased pavement base section (of ASTM No. 57 stone base course) placed over the exposed undisturbed ("uncompacted") native Terrace Deposits, should be achieved by the excavations and removals of the entire section of existing upper fill/topsoil section under the proposed permeable pavers, which is on the order of 2 to 2.5 feet thick. The entire section of the excavated areas should be then backfilled atop the exposed underlying undisturbed ("uncompacted") native Terrace Deposits using the pavement base materials (ASTM No. 57 stone base course), which will now be on the order of 2 to 2.5 feet thick, to achieve rough finish subgrade levels. 7. A minimum safety factor of2 is recommended in the design of the project permeable pavers BMP facility for providing an adequate storage capacity. We appreciate this opportunity to be of service to you again. Should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Project No. GI-15-12-50 will help to expedite our response to your inquiries. §M"§Geotechnical Solutions, Inc. Distribution: Addressee (2, e-mail) §Jfl§ GEOTECHNICAL SOLUTIONS, INC. GRAPHIC SCALE 1 10 5 0 5 10 20\ ~~~~~~~ -~I ~1-iiiiiiiiiiiii-ll : {') z g s co ( IN FEET ) I 1 inch = 10 ft. BTM WALL/AC AREA DATA LEGAL DESCRIPTION THAT PORTION OF LOT 1 (NORTH[AST QUARTER or TH[ NORTHEAST QUARTER), SECTION 1, TOWNSHIP 12 SOUTH, RANGE 5 WEST SAN B[RNANDINO MERIDIAN, IN THE CITY OF CARLSBAD, COUNTY OF SAN DIEGO, STA TE OF CALIFORNIA, ACCORDING TO OFFICIAL PLAT THEREOF. APN: 155-170-25-00 PROJECT ADDRESS 2637 JEFFERSON STREET SAN DIEGO, CA. 921 1 0 X w I I I NOTES: i I I I BENCH MARK DESCRIPTION: PT/f139: DEPT OF TRANSPORTATION DISK LOCA T/ON: IN S S/W NEAR THE E END OF LAS FLORES DRIVE BRIDGE OVER 1-5 RECORDED:~~~~~~~~~~~~~~~~-,-~- ELEVA TION: 82.221 DA TUM: NGVD 29 LOT AREA= 11,100 SF EXISTING IMPERVIOUS AREA = 4,152 SF (EXISTING CONCRill = 2,450 SF) (EXISTING BUILDING = 1,702 SF) TOTAL PROPOSED IMPERVIOUS AREA = 4,873 SF 1) ALL DRAINAGE FROM BUILDING FOUNDATION SHALL BE AT MIN. 2% GRADE 10' AWAY FROM BUILDING FOUNDATION. 2) ALL FOUNDATIONS ADJACENT TO PERMEABLE PAYERS SHALL EXTEND BELOW THE BOTTOM OF THE PAVER BASE SECTION PER SOIL LETTER DATED 04/10/17 PERMANENT BMP'S G) PROPOSED 3" LANDSCAPE POND (50 SF) @ PROPOSED PERMEABLE PAYERS (3,738 SF) EARTHWORK QUANTITIES CUT: 100 CY FJLL: 100 CY IMPORT: 0 CY EXPORT: 0 CY REMEDIAL: CY SOURCE CONTROL REQUIREMENT AND SITE DESIGN BMPS: 1sc-11 PREVENTION OF ILLICIT DISCHARGES INTO THE MS4 ~ PROTECT OUTDOOR MATERIALS STORAGE AREAS FROM RAINFALL, RUN-ON, RUNOFF, AND WIND DISPERSAL ~ PROTECT MATERIALS STORED IN OUTDOOR WORK AREAS FROM RAINFALL, RUN-ON, RUNOFF, AND WIND DISPERSAL ~ PROTECT TRASH STORAGE AREAS FROM RAINFALL, RUN-ON, RUNOFF, AND WIND DISPERSAL ~ ADDffiONAL BMPS BASED ON POTENTIAL SOURCES OF RUNOFF POLLUTANTS ISD-11 MAINTAIN NATURAL DRAINAGE PATHWAYS AND HYDROLOGIC FEATURES IS0-31 MINIMIZE IMPERVIOUS AREA ~ IMPERVIOUS AREA DISPERSION IS0-71 LANDSCAPING WITH NATIVE OR DROUGHT TOLERANT SPECIES ----------·--------------~ --- EX. FIRE clYDRANT ()::(}------T-.- 1::, '° (./') <:: (.'.) 59.44 l SEW Nlrl (/) I I (/) 58.44 AC 4 I . , ' -----------------------1-----------g ~~i;7 MH CONCRETE SLURRY CUT-OFF WALL TO PROTECT ADJACENT SITE IMPROVEMENTS AND BUILDINGS AS NEEDED PER SOILS LffiER DATED 04/10/17 NOT SCALE SECTION A-A I I 58.16 I I s 57.~~ T\~~~ is G I '" , ' I - I, a !" NOT SCALE NORTH PACIFIC OCEIN LEGEND DESCRIPTION VICINITY MAP BU:MA VISTA MY EXISTING ITEMS DWG.NO. PROPERTY LINE---------------------------------------- CENTER LINE ---------------------------------------- EXISTING GAS LINL_ ------------------------------------ EXISTING FENCE (lYPE AS NOTED)_ ___________________________ _ EXISTING CONTOUR LINE -------------------------------- EXISTING SEWER LINE------------------------------------ EXISTING WATER LINL ______ ----------------------------. EXISTING ELECTRIC OVERHEAD LINL---------------------------- EXISTING CURB & GVTTER--------------------------------- • -UISTING SIDEWALK ________ -----------------------------· EXISTING PAVEMENl ___ ------------_____ ----________ ----· EXISTING FLOW DIRECTION--------------------------------- EXISTING SEWER MANHOLE-------------------------------- - FLOWUNE ELEVATION ___________ ---____ _:_ ____ ---_ -_____ ---_ TOP OF CURB ELEVATION _________________________________ _ FlNISHED GRADE ELEVATION--------------------------------- FlNISHED SURFACE ELEVATION-------------------------------- FlNISHED FLOOR ELEVATION_ _______ ------------------------- TOP OF WALL ELEVATION _________________________________ _ TOP OF FOOT ELEVATION _________________________________ _ NATURAL GRADE ELEVATIOtL ____________________ ------------ .G\;TTER ___________________________________________ _ LEGEND PROPOSED ITEMS DESCRIPTION PROPOSED FLOW DIRECTION ___ ------------------------------ PROPOSED CONTOUR LINE.--------------------------------- PROPOSED CONCRETE _____ ------------------------2,319 SF __ PROPOSED PERMEABLE PAVERS ________________________ 3,738 SF __ PROPOSED BUILDING STRUCTURE ----------------------2,554 SF __ PROPOSED LANSDCAPL ____________________________ 2,489 SF __ ··--- ROPOSED · CONCRETE WPlK'I/AY SECTION 8-B PROPOSED GARAGE SYMBOL --GAS --GAS -- ---58- --s ---s --W VI --EOHI---EOH-- ---------- C -c-r:. T"'" ~ ... -. ·=:]· .. ··:· .... ·.·.,··; ... ,· .. : .··.:'·. ' .. ~ ·-· ._ .. -· . __ ._~ .... CI>R•·S7.:~:2T<SJ QMH FL TC FG FS FF TW TF NG G SYMBOL -----57------ I. . ; : . ' •. · .. ,•' ... ·"' .. ~· . ' . ' .' ·d. • • ' •• ' • ,.. . . . . l .-.. ' .. : ··: ;,·. ' · .. ;, I . . . . . . . . . . . . . . ·1 . . . .. . . .. . -. -. . . . -·········----- NOT SCALE L!JI CITY OF CARLSBAD IW DRAINAGE & BMP PLAN FOR: MDF-01 VICTOR RODRIGUEZ-FERNANDEZ 1283 E MAIN STREET, SUITE 109 (4-UNITS APARTMENT COMPLEX) JEFFERSON STREET EL CAJON, CA 92021 (760) 357-2434 DATE: 05-23-17 VICTOR RODRIGUEZ-FERNANDEZ, R.C.E. 35373 I DWN BY: VMRP CHKD BY: VR-F PROJECT 1\0. CDP 2016-0006 I C-2 I ----------------------·-·---~~~-- APPENDIX I ............ ,, .. 0 1 \ _ _ 11,~ \ \JI;, I>~ ~ 0,, let~\-S:>l~r,~ wWt-ck ., , C'ifl\<Yd, ~ ~ H o\-l'lew f.e.+. w.JI MJ~ ~ aJJls. \141 f\fN \r0tJ~ GQ"f\;~H'i ~ li"e.. P,ov:Jie. ~Ccmn\e."'JJ..,Ofl.s ~S C,.~ ~oo\-\ VI/It};, '1"!"· 6Jl6 GE<>TECHNICAL soLunoNs. 1Nc. 0<2C.e ~· Al !:>O Consulting Geotechnical Engineers & Geologists L1,., ! , I b ,o j '7 (.~ 5931-Sea Lion Place, Suite t 09 ~.'.:)~1(.. ~N\eke/S I Carlsbad, California 92010 760-602-7815 r,. \ \ _ 1 (\ \ \ I , I I fl smsgeosol.inc@gmail.com ~e.5£:, I f'\~ mth Dr'\ prOp!'t' e..!:. (9~ ~, ~vloA~ s.o; \s., ProJect Nt,;>GJ-15-12-:slf April I 0, 2017 Ohms Collaborative Mr. Hector Aramburo 536 Sears Avenue San Diego, California 92114 L., ' -' ,,·-" ....:.. '-...;;,, ,..=..:..:, \,, .. ..;;; REVISED PICP CONSTRUCTION PROCEDURE ALTERATIVE, PROPOSED ARELLANO 4-UNIT APARTMENTS 2637 JEFFERSON STREET CARLSBAD We understand undisturbed ("uncompacted") subgrade soils will be necessary under th . ~!CI! ~; ne., pavement section to promote infiltration for onsite storm water retention, and avoiding a · ty Development Project (PDP). We further understand that the project design requires to eliminate the perforated underdrain pipe, having the stonnwater infiltrate into the undisturbed ("uncompacted") subgrade, due to inability to gravity discharge subsurface water onto any nearby stonn drainage system or the neighboring properties. Consequently, the purpose of this effort was to provide a feasible revised construction alternative for the proposed PICP paving section for accommodating the project design requirements. ~ Reference is made to the following pertinent reports prepared by this office: '( (f)i a I. "Alternative PICP Construction Procedure, Proposed Arellano 4-Unit Apartments, 2637 t/ .,,rejv, Jefferson Street, Carlsbad, California," dated February 14, 2017. , v~ltl' 2. "Geotechnical Plan Review Update, Proposed Arellano 4-unit Apartments, 2637 Jefferson Street, Carlsbad, California," dated October 24, 2016. 3. "Geotechnical Investigation, Proposed 3-story 4-Unit Residence, 2637 Jefferson Street, Carlsbad, California," dated January 11, 2016. The proposed new design revisions to the PICP system, is generally considered feasible from a gcotechnical viewpoint. However, the following recommendations are appropriate and should be considered in the final designs and implemented during the construction phase, where appropriate Ohms Collaborative Revised PICP Construction Procedure Alternative April 10, 2017 Page2 and as applicable: I. Suitable undisturbed ("uncompacted") subgrade soils may b considered for the PICP pavement section. Based on our site study (see referen s), suilable undisturbed ("uncompacted") subgrade soils (native Terrace Deposits) occur t depths ranging from 2 to 2.5 feet below the existing ground surfaces (BOS). For this µipose, pavement section ground preparations should consist of removals of upper fill/top oil section to expose the underlying undisturbed ("uncompacted") native Terrace Deposits. An increased pavement base section (ASTM No. 57 stone base course) should then be placed over the exposed undisturbed ("uncompacted") native Terrace Deposi~ The increased pavement base section will also provide a lager storage capacity for the planned BMP facility. Remainder of the PICP pavement structural section will stay unchanged. \ \, J. 2. The perforated underdrain pipe may also be eliminated, provided an adequate storage capacity 1e,(,I)#"~ (with a proper safety factor) is considered in the design of the project BMP facility. Additionally, all foundations bearing and subgradesoils underneath theplannednewbuilding should be compacted to minimum 95% compaction levels. 3 All southern building foundations adjacent to the PICP should be extended a minimum of24 inches below the bottom of the paver base section (ASTM No. 57 stone base course), or at least 42 inches below pad finish rough grade, whichever is more. A concrete slurry cut-off wall (deepened edge restraint) extending a minimum of24 inches below the bottom of the pavement section base course should also be consider to protect adjacent site improvements and structures, where necessary and as appropriate, as previously specified (see references). LIMITATIONS The future performance of the PICP pavement BMP facility, as currently planned at the project site is difficult to predict with certainty due to numerous unpredictable factors, such as amount of seasonal and annual rainfall, infiltration rates, irrigation and maintenance of drainage systems. In order to reduce potential impacts on the adjacent building foundations, structures, improvements, or problems associated with the planned BMP facility, the folJowingrecommendations are presented: • Provide periodic maintenance of the PICP pavement BMP facility, as necessary, and monitor nearby structures and improvements. Should any saturated ground or related conditions occur, the project civil engineer and geotechnical consultant should be immediately notified. Mitigation recommendations may become necessary, and cannot be ruled out. Provide landscaping consisting of drought resistant plants and monitor the amount of irrigation water. lnigation should be limited to the amount ofwaternecessaryto suslain plant Ohms Collaborative Revised PICP Construction Procedure Alternative April 10, 2017 Page3 life. A landscape architect should be consulted, in this regard. The perfonnance and impact of the newly required privatePICPpavement BMP drainage infiltration facilities can only be evaluated through time. Additional recommendations or future repairs and modifications to the system may be necessary, in the event adverse or consequential conditions manifest themselves. This will require proper disclosure to any owners and all interested/affected parties. However, in no respect do we guarantee or warrant the perfonnance of the private PICP pavement BMP drainage infiltration facilities. We appreciate this opportunity to be of service to you. again. Should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Project No. GI-5-12-20 will help to expedite our response to your inquiries. SJ18 Geotecbnical Solutions, Inc. ehdi S. Shariat GE#2885 Distribution: Addressee (2, e-mail) 6116 GEOTECIINIC:AL SOLUTIONS. INC, APPENDIX II Design Maps Summary Report IIIJSm Design Maps Summary Report User-Specified Input Report Title Ohms Collaborative, 2637 Jefferson St., Carlsbad Mon March 12, 20 18 18:24: 15 Ul C Building Code Reference Document ASCE 7-10 Standard (which utilizes lJSGS hazard data available 1n 2008) Site Coordinates 33.1664°N, 11 7 .3487°W Site Soil Classification Site Class D -"Stiff Soll" Risk Category I/II/III Vista Q ., ,> Carlsbal sin Marcos USGS-Provided Output Ss = 1.148 g S1 = 0.440 g SHs = 1.195 g SH1 = 0.687 g Sos= 0.797g S oi= 0.458 g E scondid,o' For information on how the 55 and 51 values above have been calculated from probabilistic (risk-targeted) and deterministic ground motions in the direction of maximum horizontal response, please return to the application and select the "2009 NEHRP" building code reference document . .. ~: :, :n For PG.A,., T,, CRs, and c., values, please yiew the deta iled report. https://earthquake.usgs.gov/cn 1/designmaps/us/summary .php?template=minimal&latitude... 3/12/2018 Design Maps Detailed Report •usos Design Maps Detailed Report ASCE 7-10 Standard (33.1664°N, 117.3487°W) Site Class D -"Stiff Soil", Risk Category I/II/III Section 11.4.1 -Mapped Acceleration Parameters Note: Ground motion values provided below are for the direction of maximum horizontal spectral response acceleration. They have been converted from corresponding geometric mean ground motions computed by the USGS by applying factors of 1.1 (to obtain 5,) and 1.3 (to obtain S,). Maps In the 2010 ASCE-7 Standard are provided for Site Class B. Adjustments for other Site Classes are made, as needed, in Section 11.4.3. From Figure 22-1 ''' S, = 1.148 g From Figure 22-2 ''' s, = 0.440 g Section 11.4.2 -Site Class The authority having jurisdiction (not the USGS), site-specific geotechnical data, and/or the default has classified the site as Site Class D, based on the site soil properties in accordance with Chapter 20. Table 20.3-1 Site Classification Site Class v, Nor Nm A. Hard Rock >5,000 ft/S N/A B. Rock 2,500 to 5,000 ft/S N/A s. N/A N/A Page 1 of6 ---. ····--------·-----~·----- C. Very dense soil and soft rock D. Stiff Soll E. Soft clay soil F. Soils requiring site response analysis In accordance with Section 21.1 1,200 to 2,500 ft/s >50 >2,000 psf 600 to 1,200 ft/s 15 to 50 1,000 to 2,000 psf <600 ft/s <15 <1,000 psf Any profile with more than 10 ft of soil having the characteristics: • Plasticity index PI > 20, • Moisture content w ~ 40%, and • Undrained shear strengths. < 500 psf See Section 20.3.1 For SI: lft/s = 0.3048 m/s llb/ft2 = 0.0479 kN/m 2 https ://earthquake. usgs.gov /en l /designmaps/us/report. oho?template=minimal&latitude=3 3... 3/12/2018 Design Maps Detailed Report Page 2 of6 Section 11.4.3 -Site Coefficients and Risk-Targeted Maximum Considered Earthquake (MCE.) Spectral Response Acceleration Parameters Table 11.4-1: Site Coefficient F, Site Class Mapped MCE , Spectral Response Acceleration Parameter at Short Period s, :$ 0.25 5, = 0.50 S, = 0.75 s, = 1.00 S, ~ 1.25 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1. 7 1.2 0.9 0.9 F See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of 5, For Site Class= D and S, = 1.148 g, F, = 1.041 Table 11.4-2: Site Coefficient F, Site Class Mapped MCE, Spectral Response Acceleration Parameter at 1-s Period s, :$ 0.10 S, = 0.20 S, = 0.30 s, = 0.40 S, ~ 0.50 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1. 7 1.6 1.5 1.4 1.3 D 2.4 2.0 1.8 1.6 1.5 E 3.5 3.2 2.8 2.4 2.4 F See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S, For Site Class = D and s, = 0.440 g, F, = 1.560 https://earthauake. usgs,gov I en 1 /desigrunaps/us/report. php?tem p!ate=minimal&latitude=3 3... 3/12/2018 Design Maps Detailed Report Equation ( 11.4-1 ): SMs = F,Ss = 1.C.41 X 1.148 = 1.195 g Equation (11.4-2): SM, = F.S, = 1.560 ~ 0.440 = 0.687 g Section 11.4.4 -Design Spectral Acceleration Parameters Equation (11,4-3): Sos=% SMs = % X 1.195 = 0.797 g Equation (11.4-4): So, = % SM, = % X 0.687 = 0.458 g Section 11.4.5 -Design Response Spectrum From Figure 22-12 c" T, = 8 seconds Figure 11.4-1: Design Response Spectrum Sc,, -0.797 ' So, ... 0.458 -~-- - - --- - - -~ ----------' ' ' ' ' ' ' ls""0.575 T <T0 : S, = S,. ( 0.4 + 0.6T IT,) T,STST1 :S,=S,. T1 <TST,:S,=S0,/T T>T,:S,=S.,T,/T' Page 3 of6 https ://earthquake. usgs.g ov I en 1 /designmaps/us/report. php?template=minimal&latitude=3 3... 3/12/2018 Design Maps Detailed Report Page 4of6 Section 11.4.6 -Risk-Targeted Maximum Considered Earthquake (MCE.) Response Spectrum The MCE, Response Spectrum is determin, d by multiplying the design response spectrum above by 1.5. 5,.-1.195 s..,. -0.687 _1,.. -----------1 - - - - - - - ---' ' ".',, ... Q,115 T~ .... Q.575 1.0:J:J PttuX1. T {!!K) https :// earthquake. usgs.gov I en l /designmaps/us/report. php?template=minimal&latitude=3 3... 3/12/2018 Design Maps Detailed Report Page 5 of6 Section 11.8.3 -Additional Geotechnical Investigation Report Requirements for Seismic Design Categories D through F From figure 22-7''' PGA = 0.454 Equation (11.8-1): PGAM = FPG,PGA = 1.046 x 0.454 = 0.475 g Table 11.8-1: Site Coefficient F .... Site Mapped MCE Geometric Mean Peak Ground Acceleration, PGA Class PGA S PGA = PGA = PGA = PGA 2': 0.10 0.20 0.30 0.40 0.50 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of PGA For Site Class = D and PGA = 0,454 g, F,.. = 1.046 Section 21.2.1.1 -Method 1 (from Chapter 21 -Site-Specific Ground Motion Procedures for Seismic Design) From Figure 22-17 ''' c .. = 0.944 From Figure 22-18 ''1 c,, = 0.995 https://earthquake.usgs.gov/cnl/designmaps/us/report.php?template=minimal&latitude=33... 3/12/2018 Design Maps Detailed Report Section 11.6 -Seismic Design Category Table 11.6-1 Seismic Design Category Based on Short Period Response Acceleration Parameter RISK CATEGORY VALUE Of Sos I or II III IV S05 < 0.167g A A A 0.167g :S s., < 0.33g B B C 0.33g :S s., < O.SOg C C D O.SOg :S S., D D D For Risk Category= I ands,.= 0.797 g, Seismic Design Category= D Table 11.6-2 Seismic Design Category Based on 1-5 Period Response Acceleration Parameter RISK CATEGORY VALUE OF 50, I or II III IV s., < 0.067g A A A 0.067g :S s., < 0.133g B B C 0.133g :S s •• < 0.20g C C D 0.20g :S s., D D D For Risk Category = I and s., = 0.458 g, Seismic Design Category = D Note: When S, is greater than or equal to 0. 75g, the Seismic Design Category is E for buildings in Risk Categories I, II, and Ill, and F for those in Risk Category IV, irrespective of the above. Seismic Design Category = "the more severe design category in accordance with Table 11.6-1 or 11.6-2" = D Note: See Section 11.6 for alternative approaches to calculating Seismic Design Category. References 1. Figure 22-1: Page 6 of6 https ://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7 _Figure_22-1. pdf 2. Figure 22-2: https ://earthquake.usgs.gov /hazards/designmaps/downloads/pdfs/201 O_ASCE-7 _Figure_22-2. pdf 3. Figure 22-12: https://earthquake. usgs.gov/hazards/designmaps/downloads/pdfs/20 lO_ASCE-7 _Figure_22-l 2. pdf 4. Figure 22-7: https ://earthquake. usgs.gov /hazards/designmaps/downloads/pdfs/2010 _ASCE-7 _Figure_22-7. pdf 5. Figure 22-17: https ://earthquake. usgs.gov /hazards/designmaps/downloads/pdfs/20 lO_ASCE-7 _Figu re_22-17. pdf 6. Figure 22-18: https ://earthquake. usgs.gov /hazards/designmaps/downloads/pdfs/201 O_ASCE-7 _Figure_22-18. pdf https ://earthquake. us gs.gov /en 1 /desigrunaps/us/report. php ?temp late=minimal&latitude=3 3. .. 3/12/2018 APPENDIX III Project No. GI-15-12-50 February 14, 2017 Ohms Collaborative Mr. Hector Aramburo 536 Sears Avenue San Diego, California 92114 8118 GEOTECHNICAL SOLUTIONS, INC. Consulting Geotechnical Engineers & Geologists 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 760-602-7815 smsgeosol.inc@gmail.com ALTERATIVE PICP CONSTRUCTION PROCEDURE, PROPOSED ARELLANO 4- UNIT APARTMENTS, 2637 JEFFERSON STREET, CARLSBAD, CALIFORNIA We understand the project stormwater BMP designs considers to retain all storm waters onsite as a mitigation measure to avoid a Priority Development Project (PDP). For this purpose, the impervious liner on the bottom and sides of the PICP system (see Figure 2 of October 24, 2016 report) needs to be eliminated and the paving constructed with 12 inches clear distance from the building foundations. The proposed revisions to the PICP system, is generally considered feasible from a geotechnical viewpoint, provided the following are also considered in the final designs and implemented during the construction phase, where appropriate and as applicable: 1. The impervious liner on the bottom and sides of the PICP system may be eliminated and the paving constructed with 12 inches clear distance from the building foundations. All remaining recommendations, including the underdrain and minimum 95% compacted subgrade requirements, will stay the same (see Figure 2 of October 24, 2016 report). The finish subgrade below the pavement section should slope at a minimum of2% away from the building foundations towards the underdrain trench. 2. All building foundations adjacent to the PJCP should be extended a minimum of 18 inches below the bottom of the paver sections, or at least 42 inches below pad finish rough grade, whichever is more. Alternatively, a minimum 8 inches wide concrete slurry cut-off wall (deepened edge restraint) extending a minimum of 24 inches below the bottom of the foundations may be considered. The cut-off wall (deepened edge restraint) should be constructed prior to building foundation trenching. 3. Nearby site structures and improvements should also be protected with similar cut-off walls Ohms Collaborative Alternative PICP Construction Procedure February14,2017 Page2 ( deepened edge restraints) as needed. We appreciate this opportunity to be of service to you. again. Should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Project No. GI-5-12-20 will help to expedite our response to your inquiries. SIIS Geotechnical Solutions, Inc. Distribution: Addressee (I, e-mail) S'H§' GEOTECHNICAL SOLUTIONS, l~C.