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Home My WebLink AboutCDP 16-26; 4390 Yuki Lane; Percolation Testing Lot 1 & 2 Yuki Lane; 2016-08-23GINEERING DESIGN GROUP Date: August 23, 2016 To: Re: Subject: COP Pacific Beach 2014, Ltd. c/o San Dieguito Development Attn: Ted Montag 1106 Second St PMB 255 Encinitas, CA 92024 p: 760.635.7633 e: tedmontag3@msn.com Percolation Testing, Lots 1&2, Yuki Lane, Carlsbad, California Percolation Testing and Infiltration Rate 15-26-4390 Yuki Lane AUG 2 6 2016 We have conducted percolation testing at the above referenced lots in the area of the proposed bioretention basins. On August 3, 2016 two, 6 inch diameter test holes, one per lot, were excavated to depths between 5-5.5 feet below existing grade in the area of the proposed bioretention area. The test holes were then presoaked. On August 4, 2016, the test holes were filled to approximately 24 inches above a 3 inch pea gravel layer and monitored at half hour intervals with refilling the holes to maintain the column of water until a stabilized percolation rate was encountered, a period of 6 hours. No groundwater was encountered. The percolation test rate was then reduced and converted to an infiltration rate. The table below provides a summary of the field observation percolation rate and the unfactored infiltration rate. Additionally, we have attached form 1-9 with geotechnical factors allotted for design factor of safety determination. The civil engineer should weigh those elements that have to do with basin design (Section B of the table) to finalize the overall design factor of safety. Lot No. Hole Soil Description Percolation Rate Depth (in/hr) 1 5.5 Total Depth-Light 16 brown to tan, silty sands 2 5 Total Depth-Light 15 brown to tan, silty sands NEW RESIDENCES Lots 1&2 Yuki Lane, Carlsbad, California ENGINEERING DESIGN GROUP GEOTECHNICAL, CIVIL, STRUCTURAL CONSULTANTS Unfactored Infiltration Rate (in/hr) 2.5 2.3 Infiltration Rate Minimum Factor of Safety= 2.25 1.1 1.0 Page No.1 Job No. 155513-1 Soil Types encountered were consistent with those described in the geotechnical reports, silty sands. Based upon the percolation test results it is our opinion that hydrologic soil group B may be used for the design of the basin in the area of the proposed biofiltration areas. All other geotechnical offsets and limitations to the bioretention areas remain applicable. If you have any questions with respect to this addendum, please do not hesitate to call our office. Respectfully Submitted, ENGINEERING DESIGN GROUP Steven Norris GE 2590 Attachments: Form 1-8 Form 1-9 Figures 1-2-Test Locations Map NEW RESIDENCES Lots 1&2 Yuki Lane, Carlsbad, California Erin Rist RCE 65122 ENGINEERING DESIGN GROUP GEOTECHNICAL, CIVIL, STRUCTURAL CONSULTANTS Page No.2 Job No. 155513-1 Appendix 1: Forms and Checklists Woul~ i1rliJtrati~rt of the full~esign volmile be feasible from a physicalperspective without 'lny uridesirable consequences' that cannot be reasonably mitigated? Yes. Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response X to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. Provide basis: The areas of proposed bioretention areas (two total, one area per lot) were tested utilizing County of San Diego standards for percolation testing, including pre-soaking of soils. Based upon the test results, at the locations tested, the infiltration rates were found to be greater than 0.5 in/hr. Lot 1-Percolation Rate= 16 in/hr; Infiltration Rate= 2.5 in/hr (no FS applied) Lot 2-Percolation Rate= 15 in/hr; Infiltration Rate= 2.3 in/hr (no FS applied) Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study I data source applicability. 2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. Provide basis: X Hazards are considered and requirements for infiltration are outlined in geotechnical reports and addendums. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study I data source applicability. 1-3 February 2016 Appendix 1: Forms and Checklists 3 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, storm water pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: X During original site grading groundwater was not encountered and shallow groundwater table was not observed onsite. Groundwater is anticipated to be greater than 15 feet. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability. 4 Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: Based upon site conditions not anticipated. X Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability. Part 1 Result * If all answers to rows 1 - 4 are ''Yes" a full infiltration design is potentially feasible. The feasibility screening category is Full Infiltration If any answer from row 1-4 is "No", infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a "full infiltration" design. Proceed to Part 2 *To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4 Permit. Additional testing and/ or studies may be required by the City to substantiate findings. 1-4 February 2016 Appendix 1: Forms and Checklists be physit:a:Uy feasible withOlit any negative 5 Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. Provide basis: Yes No Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study I data source applicability and why it was not feasible to mitigate low infiltration rates. 6 Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. Provide basis: Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study I data source applicability and why it was not feasible to mitigate low infiltration rates. 1-5 February 2016 Appendix 1: Forms and Checklists 7 Can Infiltration in any appreciable quantity be allowed without posing significant risk for groundwater related concerns (shallow water table, storm water pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates. 8 Can infiltration be allowed without violating downstream water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates. Part 2 Result* If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. The feasibility screening category is Partial Infiltration. If any answer from row 5-8 is no, then infiltration of any volume is considered to be infeasible within the drainage area. The feasibility screening category is No Infiltration. *To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4 Permit. Additional testing and/ or studies may be required by the City to substantiate findings. 1-6 February 2016 A Suitability Assessment Soil assessment methods Predominant soil texture Site soil variability Depth to groundwater / impervious layer 0.25 0.25 0.25 0.25 Suitability Assessment Safety Factor, SA = Z:p B Design Level of pretreatment/ sediment loads Redundancy/ resiliency expected 0.5 0.25 Compaction during construction 0.25 Design Safety Factor, SB = Z:p Combined Safety Factor, Stoml= SAx SB Observed Infiltration Rate, inch/hr, Kobscrved (corrected for test-specific bias) Design Infiltration Rate, in/hr, Nesign = I<Cobserved / Stotal Briefly describe infiltration test and provide reference to test forms: 1-9 Appendix 1: Forms and Checklists p:::wxv 2 0.5 1 0.25 1 0.25 1 0.25 1.25 February 26, 2016 ENGINEERING DESIGN GROUP GEOHCH-tfrCAL. Cf'n. & SllUJClUI'.Al CCH:'"..ut.J~lT5 rOA f\[S'O[f.411Al .\ r.OMVEAClAl COtfSTPUCTIOPi 2121 Montiel Road, San Marcos, California 92069 • (760) 839-7302 ·Fax: (760) 480-7477 • www.designgroupca.com ·~ ~!QZ.C: !)( -....../ •••• ftoo '- \"::::-PROPERTY LINE .::::>~EXIST. DRIVEIIAY~ PER SDRSD NO. G-14D AS SHOIIN ~ c:tl D'WG. NO. 479-4A N) EXIST. \lATER SERVICE PER DIIG. 479-4,._ _____ _ :D'WK UNDERDRII[N 'ER D-27 18.54 fl -3• PVC EXIST. TYPE A CURB OUTLET PER D'WG. 4 78-41\ Project: Yuki Lane Lot 1 Approximate Test Location & Hole Depth 5.5 ft Address: Yuke Lane, Carlsbad, California EDG Project No: 155513-1 - _Q• $(11lAC~ PROPOS£]) IIALL SEE SHEETS 4 AND :1.- • . uur -~·-·-~ .-~ ·. ·.· -~-~·. ~. · .. / ~'XJ.l' RIP-RAP PAD CTYPE a> VITH Nil 2 BACKING L f!L TER fABRIC PER MODifiED D-40. CHINIMUM DIME:NSIDNS MODIFJED>. !J.!!.. L REMOVE EXIST. CATCH BASIN-----~ GRATE PER D'WG. 479-4A AND REPLACE 'WITH CAP COVER FIGURE 1 Test Location-Lot 1 GINEERING DESIGN GROUP GEOHCH"ff'CAL, CIV'a. & SllutCTUI\Al CCW~fA.'IT:i. FOR R[S:ort"TI'l .\ f.OUIJ£q.ctAl COUSTPUtliOPi 2121 Montiel Road. San Marcos. California 92069 • (760) 839-7302 • Fax: (760) 480-7477 • www.designgroupca.com Ill> Project: Yuki Lane Lot 2 ~ s ~ ~ Address: Yuke Lane, Carlsbad, California EDG Project No: 155513-1 Pln]P(IHY L!~[ LOT 1 PIIIO•IIH' P£1( DVG. •76-"'A Pit!PLilTY LIN( ------•• a..:;t~ ~ ---- Approximate Test Location OQOPOtTV U~ L..,; ~~ "j'X5'Kl:· ~Jf>-!lf,..P PA;) !lf'P~ ~.,..1.1-1 "«.l i! IACIC'IhCil rn. T[R rABA:IC F>tR ~tllr!E:tl ';-.110 ("]NIMJ .. DI~"-SiO~~ "'C':JriCJ> LOT 3 P.-.o • 96oc P(ll 1)\J(j 478-oto\ -PQ(Jf'(IH" LlN£ -~~~-rj;~~1'f:/~l~ z t'I'Pf_ 8 qqow Pf't SO!tSD D FIGURE 2 Test Location-Lot 2 ·',