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Home My WebLink AboutCDP 15-26; YUKI LANE; PERCOLATION TESTING AND INFILTRATION RATE; 2016-08-23ENGINEERING DESIGN GROUP GIO1ECHUICS. CIVIL,SIRUCUVk1 V A CHIAVCAURAA COUS1AUHATS FDRRESID(N1IVL & COMMERCTAICOIASTRUCTIOH 2121 Montiel Road, San Marcos, California 92069• (760) 839-7302• Fax: (760) 480-7477 www.designgroupca.com Date: August 23, 2016 To: Pacific Beach 2014, Ltd. F..E('EL 'IV 'TEE D do San Dieguito Development Attn: Ted Montag AUG 2 6 2016 1106 Second St PMB 255 Encinitas, CA 92024 LAND DEVELOPMENT p: 760.635.7633 ENGINE ER I NC e: tedmontag3@msn.com Re: Percolation Testing, Lots 1&2, Yuki Lane, Carlsbad, California Subject: Percolation Testing and Infiltration Rate CDP 15-26 - 4390 Yuki Lane 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 Unfactored Infiltration Depth (in/hr) Infiltration Rate Rate (in/hr) Minimum Factor of Safety = 2.25 1 5.5 Total Depth - Light 16 2.5 1.1 brown to tan, silty sands 2 5 Total Depth - Light 15 2.3 1.0 brown to tan, silty sands NEW RESIDENCES Page No. 1 Lots 1&2 Yuki Lane, Carlsbad, California Job No. 155513-1 ENGINEERING DESIGN GROUP GEOTECHNICAL, CIVIL, STRUCTURAL CONSULTANTS Soil Types encountered were consistent with those described in the geotechilical 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 thisaddendum, please do not hesitate to call our office. Respectfully Submitted, ENGINEERING DESIGN GROUP OFESSi IV GE 259 co CO LU C of C 651 22 IL Steven Norris GE 2590 Attachments: Form 1-8 Form 1-9 Figures 1-2 - Test Locations Map Erin Rist RICE 65122 NEW RESIDENCES Page No. 2 Lots 1&2 Vuki Lane, Carlsbad, California Job No. 155513-1 ENGINEERING DESIGN GROUP GEOTECHNICAL, CIVIL, STRUCTURAL CONSULTANTS Appendix I: Forms and Checklists Categorization •Infiltration1 Condition : Part 1 - Full Infiltration Feasibility Screening Criteria Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated? Criteria Screening Question Yes No 1 Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. X 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 ES 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/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. x Provide basis: 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/data source applicability. thruary 2016 Appendix I: Forms and Checklists Cnteri Screening Question Yes No a 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 X 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: 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. 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 X 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. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. If all answers to rows I - 4 are "Yes" a full infiltration design is potentially feasible. Part 1 The feasibility screening category is Full Infiltration Result * If any answer from row 1-4 s No,, in i filtration nfiltration 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 M54 Permit. Additional testing and/or studies may be required by the City to substantiate findings. 1-4 February 2016 Appendix I: Forms and Checklists Form 1-8 Page Part 2— Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria Screening Question Yes No Do soil and geologic conditions allow for infiltration in any 5 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: 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. Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope 6 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/data source applicability and why it was not feasible to mitigate low infiltration rates. 1-5 February 2016 Appendix I: Forms and Checklists Criteria Screening Question Yes No 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. Can infiltration be allowed without violating downstream 8 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. If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. Part 2 The feasibility screening category is Partial Infiltration. Result* 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 Appendix I: Forms and Checklists Factor of E1and IDesignI71 InfiltrationRate -- - - WorksheettI Form 1-9 Factor Category Factor Description Assigned Weight (w) Factor Value (v) Product (p) I p = w x A Suitability Assessment Soil assessment methods 0.25 2 0.5 Predominant soil texture 0.25 1 0.25 Site soil variability 0.25 1 0.25 Depth to groundwater / impervious layer 0.25 1 0.25 Suitability Assessment Safety Factor, SA = Ep 1.25 B Design Level of pretreatment/ expected sediment loads 0.5 Redundancy/resiliency 0.25 Compaction during construction 0.25 Design Safety Factor, SB Combined Safety Factor, S,mi= SA x SB Observed Infiltration Rate, inch/hi, K0b8 ,.d (corrected for test-specific bias) Design Infiltration Rate, in/hr, IK<i, = Kobsced / S0i Supporting Data Briefly describe infiltration test and provide reference to test forms: 1-9 February 26, 2016 / F / - ¼ I BW 3 PVC OUTLET - j PROPERP LINE t \ \ \ \\\\ \ 5' EXSTDRIVEY— A ' / G-14D AS SHOWN 4 . \ _\_\ EXISTING \ RMEABLE D01VEVAY-. / I \ IJj ..- _- SURFACEPER DR1VEAY I - - _ANDEETAH S L / EXIST SERVICE PER, DVG. 478-4 \ / i 1 _•___\ DVK. UNDERDRAIN / 0 0 FG 1954-FL-ia PVC L PVCPIPE' V YC PERFCRATED -. -, Aj UNBERDRAINP1PE------ - - ROOF DRAIN 9a66 FL- 3 PVC - '/ (TYPICAL) — rPVCP1PE' (TYPICAL)+111 Ice D EL 'X4'-REDUCER XIk SE / / - - I / ) BIOFLTRATION BASIN f - -ill t El 5'Xlr RIP-RAP PAD (TYPE Approximate Test 1 eWITH NO. 2 BACKING & / 7 2J F1 TER FABRIC PER MODIFIED PROPOSED 6' PVC Location D-40. (MINIMUM DIMENSIONS AT 1>1 MIN. & Hole Depth 5.5 ft 'ioa DIFIED 1 FL I f—.. \I PRUEED 6 PVC / ,P€RpETAIL THIS SHEET p. AT\l\Nuv./ 21 •O .._-PO J \110 8OULE tTA — - PER bw('78~4A FL 6 PVC SIL ---/ V so -41E SD— SD SD Sq PROPERTY LINE \ 4111 2 12 r a CONK (PER 0 8- E KNOCKOUT OR DRILL HOLE / REMOVE EXIST. CATCH ,BASIN / TO CONNECT PIPE THROUGH SIDE OF CATCH BASIN. / GRATE PER DVG. '47974A AND / SEAL AND GROUT PIPE CONNECTION. \i REPLACE WITH CAPCOVER / Project: Yuki Lane Lot FIGURE 1 Address: Yuke Lane, Carlsbad, California EDG Project No: 155513-1 Test Location — Lot 1 IENGINEERING 0 DESIGN GROUP I &IILCUW1CL. CVa. 6 KIICWRM. roIl-Lsn[6Tt6L.; r.TML'(Pr,IML r.,ucTnIJr.tITN 2121 Montel Road, San Marcos, California 92069 - (760) 839-7302• Fax: (760) 480-7477 - www.designgroupca.com / / iWFIRT1 LDVE - LOT 70 PER D~S / I iL 1. — LcPQ0 / --—•. - -- /7R5'1 - -- - 'PI cR POCERIR LIRE V - - rxlsr -- RERVICE - •.• , _f Raar MAN 2.7n rs.1ca LOT TID Of PrRJ DV 41 -4A 5'XXXIA' PIP-RAP PAD (TVPE It e) I I W.NtMR DIMENSIONS ,, 1,/ rL Approximate r IE 6- PVC Test Location •nvN%MUT TO MAN ,IDR . & Hole Depth 5 ft. :PERED r ,00,, LIRE rR0IL ER WTWG - V PVC C oR BITCH C Aw -S.--- PnPERrT u, LOT 3 P/C - 9600 PER OSIG. 476-AR iJ: 1 --pRoPEo1-- LIRE i 4, RPE8R90R0 PER ROP.S0 a. aCrE. -ORSILA 93~ Ft aoroLoQErIrJ,I 96016 EL? 8EIRIL DR SlEET C PROPOSED 6 PVC AT 11 RIPE 7?4561.I PIP-R4P PRO IrOPE a Vl10 C BACKING 6 TILLER PAllEt PER P'COIFIER 0-40 49161046, CIREARI004 ROI)ITIED). Project: Yuki Lane Lot 2 Address: Yuke Lane, Carlsbad, California EDG Project No: 155513-1 FIGURE 2 Test Location — Lot 2