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Home My WebLink AboutPD 2023-0008; 3229 HIGHLAND; UPDATED INFILTRATION TESTING FOR 3229 HIGHLAND; 2024-01-12~= -=225aS?APPLIED CONSULTANTS geotechnfca/ & forensic engineering JC Collins and Jeannine Woo 2633 Lincoln Blvd, Unit 941 Santa Monica, CA 90405 January 12, 2024 1941-A Friendship Drive El Cajon, CA 92020 TEL (619) 258-9000 www.applied-consultants.com Subject: Updated Infiltration Testing Report for the Subject Property Located at 3229 Highland Drive, Carlsbad, CA, 92008 Dear Mr. Collins & Mrs. Woo, In accordance with your request, we have prepared this Infiltration Testing Report for the property located at the aforementioned address. The purpose of this report was to provide a feasibility analysis for infiltration with respect to geotechnical and groundwater conditions. We performed design phase infiltration testing as part of our study. It is our professional opinion that a design infiltration rate of 0.38 inches per hour may be used for the design ofBMP infiltration devices of this project. The grading plans for the subject property dated December 26, 2023 prepared by John L. Majocha P .E. propose gravel pavement and permeable pavers for driveways and hardscape. The proposed permeable surfaces are mapped adjacent to proposed foundations. Infiltration at these areas can cause reductions in soil strength. In order to prevent reductions in soils strength, the proposed foundations adjacent to permeable pavers and gravel pavement shall be extended or cut-off-walls bottoms shall be constructed such that the foundations or cut-off-walls extend two feet below the bottom of the base rock storage section. Additionally, the proposed permeable pavement is mapped over an existing sewer lateral. In order to prevent damage to sewer utilities from stormwater infiltration, sewer pipes located within ten feet of infiltration areas shall be encased with concrete or steel. We appreciate this opportunity to be of service. Should you have any questions, please call our office at (619) 258-9000. Sincerely, Jorge L. Val. Gonzalez, PE 92051 Project Engineer 3229 Highland Drive -Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page I of 7 1.0 SITE EVALUATION The location of the property is at latitude 33° 9'48"N and longitude 117°20'1 0"W. The subject property is located in a residential neighborhood of Carlsbad, California (Figure 1 ). For the purpose of this report the front of the subject property which faces Highland Dr is assumed to be east. The subject property is bounded on the north by Pine Ave; to the east by Highland Drive; and to west and south by other existing residential dwellings. Review of the current topographic map for the site indicates that the subject property is at approximately 171 feet with respect to the North American Vertical Datum of 1988 (NA VD 88) The subject property is a rectangular shaped parcel of approximately 0.48 acres that moderately slopes (10-15%) from east to west. The lot is currently occupied by an existing one-story wood framed single family residence, a single-story companion unit and a detached garage. The proposed development is the construction of a new two-story residence with a partial daylight basement, a detached single-story ADU and a below grade swimming pool. Based upon the local topography, historical aerials and our subsurface investigation, we feel that the majority of the subject property is underlain by native soils. As part of our study, we reviewed the State of California, State Water Resources Control Board Geotracker system. There are no active cleanup sites or contaminated sites within a 400 feet radius of the subject property. There are no "Brown fields" adjacent to the subject property. According to the County of San Diego Hydrology Manual -Soil Hydrologic Group. The County of San Diego Hydrology Manual categorizes the soils at the subject property as Hydrologic Group B . The Hydrologic Group B is characterized as "Soils have moderate infiltration rate when thoroughly wetted; chiefly soils that are moderately deep to deep, moderately well drained to well drained, and moderately coarse textured. Rate of water transmission is moderate." Groundwater was not encountered during our investigation. Based on our field investigation and review of available published groundwater data and historical information from the monitoring well of project T0608170198 (Geotracker) located 0.3 miles west of the subject property and published from geotechnical exploration performed for project T10000011547 (Geotracker) located 0.4 miles north of the subject property, groundwater is not anticipated to be within 10 feet of the lowest elevation of the site. The properties surrounding the subject property are highly developed with piped water and sewer systems. Based upon the density of the development, there are no water supply wells, septic systems, or underground storage tanks, or permitted gray water systems within 100 feet of the proposed infiltration areas. 3229 Highland Drive - Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page 2 of7 Geographic Location ~~APPLIED CONSULTANTS geotechnical & forensic engmeer,ng 3229 Highland Drive, Carlsbad, CA,92008 GeoTracker Map (1,000 feet radi us) 3229 Highland Drive -Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page 3 of7 i N Fig. 1 Geographic Location Soil Groups CJ GroupA 1111 GroupB CJ Groupe CJ GroupD CJ Undetermined CJ Data Unavailable geolechnical & forensic engineering 3229 Highland Drive, Carlsbad, CA,92008 Soil Hydrology Groups Map County of San Diego 3229 Highland Drive -Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page 4 of7 i N Fig. 2 2.0 SUBSURFACE EXPLORATION 2.1 Initial Field Investigation On May 26, 2022, a representative of this firm visited the site to perform physical reconnaissance and field work at the subject property for purposes of our preliminary geotechnical investigation. Soil samples were taken from the proposed site to be evaluated. We hand augered four borings as part of our reconnaissance. The borings were taken within the subject property to a maximum depth of four feet below grade. Locally the materials encountered are generally: -From grade to fourteen inches below grade a fine to medium grained, loose, reddish brown silty sand (SM) was encountered. -From fourteen inches below grade to forty-eight inches below grade a fine to medium graded, reddish light brown silty sand (SM) was encountered. No ground water was encountered during our site reconnaissance. 3.0 INFILTRATION TESTING On June 22, 2023, a representative of our firm performed infiltration testing with "Borehole Percolation Tests" at the subject property. Four borings were excavated within the area proposed infiltration areas. Location of proposed infiltration areas and elevations are referenced by the grading & drainage plan for the subject property dated December 26, 2023 prepared by John L. Majocha P .E. 3.1 Methodology We performed design phase infiltration testing as part of our study. Four borings were excavated to a maximum depth of two feet at various elevations to perform "Borehole Percolation Tests" for determination of infiltration rates in conformance with the City of Carlsbad BMP Manual. Prior to percolation testing, all borings were filled with water to top of hole for a minimum of four hours. After four hours, the water column was allowed to drop overnight. Our test was performed within 15-30 hours after the initial four-hour presoak. The holes were refilled to approximately top of hole and the rate of fall was measured and recorded for a minimum of six hours, refilling every 30 minutes until consistent result were obtained. Regarding lateral infiltration, the Porchet Correction was applied for the final hour of percolation rates to obtain infiltration rates. 3229 Highland Drive -Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page 5 of7 3.2 Infiltration Test Results On June 22, 2023, Percolation Hand Boring #1 through #4 were tested. Field data for each boring is attached to the report figures. The following table presents the final percolation results converted to infiltration rates: PERCOLATION RATE CONVERSION TO INFILTRATION -PORCHET METHOD (IN/HR) PHB-1 PHB-2 PHB-3 PHB-4 Dt (in) Depth of hole 24.00 24.00 24.00 24.00 Do (in) Initial depth to water 4.00 4.00 4.00 4.00 Df (in) Final depth to water 10.75 11.25 12.50 8.50 Ho (in) 20.00 20.00 20.00 20.00 Hf (in) 13.25 12.75 11.50 15.50 Delta H (in) 6.75 7.25 8.50 4.50 Have (in) 16.63 16.38 15.75 17.75 radius (in) 6.00 6.00 6.00 6.00 Time interval (min) 30.00 30.00 30.00 30.00 Percolation rate (in/hr) 13.50 14.50 17.00 9.00 Infiltration Rate (in/hr) 2.06 2.25 2.72 1.30 The design infiltration rate is = corrected infiltration/ F.S. (Table D.2-3) = 1.3 in/hr/ 3.38 = 0.38 in/hr 4.0 INFILTRATION STUDY CONCLUSIONS We performed design phase infiltration testing as part of our study. It is our professional opinion that a design infiltration rate of 0.38 inches per hour may be used for the design ofBMP infiltration devices of this project. The grading plans for the subject property dated December 26, 2023 prepared by John L. Majocha P.E. propose gravel pavement and permeable pavers for driveways and hardscape. The proposed permeable surfaces are mapped adjacent to proposed foundations. Infiltration at these areas can cause reductions in soil strength. In order to prevent reductions in soils strength, the proposed foundations adjacent to permeable pavers and gravel pavement shall be extended or cut-off-walls bottoms shall be constructed such that the foundations or cut-off-walls extend two feet below the bottom of the base rock storage section. Additionally, the proposed permeable pavement is mapped over an existing sewer lateral. In order to prevent damage to sewer utilities from stormwater infiltration, any sewer pipes located within ten feet of infiltration areas shall be encased with concrete or steel. 3229 Highland Drive -Updated Infiltration Testing Report JLVG/JED 1/12/2024 Page 6 of7 FIGURES AND FIELD DATA 3229 Highland Drive -Updated Infiltration Testing Report JL VG/JED 1/12/2024 Page 7 of7 .APPLIED CONSULTANTS ~t a! 9«)laf1Y ~ f1119lnHrlng PtH& AIIE>IU& LEGEND: ~HB-1 INFILTRATION TEST BORING LOCATION FIGURE 1: INFILTRATION TESTING MAP (GRADING PLAN BASE) 3229 HIGHLAND DRIVE, CARLSBAD, CA 92008 [?;;:.:~;;~~~ oo(::x ~:i~~~~o-~ [!]J· >-Q{ ()(Jr'!f,,,, /"J. fi':i~itSU<RS @JCCWCR!lr P,of)/[llf fi]LG-.Cffl'l' C~9 P(f?' ~(. ,t...!/l' CV.~ I.MJ ;]Pr.vt,H'.( P,Ht"'!' f ".iklllQI.£ C-»STIHC M L]j.RlU"l.f" f»~ ,-.C ~ B: :'UI'.)\.£ {X,Sr,Hf; 1 fil~\.£{Jt!S&i(;}f b.3lM_,.,\.£CXJSr.HC ~/iOIO',f' {Jt1Sr:N(; /)r-,, :~J;Clr.'.)',[' AS/'Htl,J. f (J.<I' ~Rtll'::i~r 02:",N';,, REFERENCE: This map was prepared from a Grading Plan by John Majocha P.E. and from the field investigation performed by APPLIED CONSULTANTS. Date: 7/14/23 Drawn by: JLVG PERCOLATION TESTING FIELD DATA Proiect Name and Test Location: 3229 Hiohland Drive, Carlsbad, CA, 92008 Test pit#: 1 Hole diameter (in): 6 Test By: JV Hole depth (in): 24 Liauid Used: Water USCS Class: SM Date of Test: 6/22/2023 Deoth to Water Table: > 10 feet Liquid Level Maintained by usinq: Manually Additional Comments: Time Time Dt (min) Readings interval (hr:min) & Total Depth to Percolation Rate (in/hr) Remarks Water (in.) ~H (in) 1-Start 9:00 0:30 4.000 14.000 28.000 End 9:30 0:30 18.000 2-Start 9:30 0:30 4.000 12.000 24.000 End 10:00 1:00 16.000 3-Start 10:00 0:30 4.000 9.000 18.000 End 10:30 1:30 13.000 4-Start 10:30 0:30 4.000 9.000 18.000 End 11 :00 2:00 13.000 5-Start 11:00 0:30 4.000 9.000 18.000 End 11:30 2:30 13.000 6-Start 11:30 0:30 4.000 8.500 17.000 End 12:00 3:00 12.500 7-Start 12:00 0:30 4.000 8.500 17.000 End 12:30 3:30 12.500 8-Start 12:30 0:30 4.000 6.750 13.500 End 13:00 4:00 10.750 9-Start 13:00 0:30 4.000 6.750 13.500 End 13:30 4:30 10.750 10-Start 13:30 0:30 4.000 6.750 13.500 End 14:00 5:00 10.750 11-Start 14:00 0:30 4.000 6.750 13.500 End 14:30 5:30 10.750 12-Start 14:30 0:30 4.000 6.750 13.500 End 15:00 6:00 10.750 PERCOLATION TESTING FIELD DATA Project Name and Test Location: 3229 HiQhland Drive, Carlsbad, CA, 92008 Test pit#: 2 Hole diameter (in): 6 Test Bv: JV Hole deoth (in): 24 Liquid Used: Water USCS Class: SM Date of Test: 6/22/2023 Depth to Water Table: > 10 feet Liauid Level Maintained by usina: Manually Additional Comments: Time Time Dt (min) Readings interval (hr:min) & Total Depth to Percolation Rate (in/hr) Remarks Water (in.) LiH (in) 1-Start 9:00 0:30 4.000 14.500 29.000 End 9:30 0:30 18.500 2-Start 9:30 0:30 4.000 12.000 24.000 End 10:00 1:00 16.000 3-Start 10:00 0:30 4.000 11.500 23.000 End 10:30 1:30 15.500 4-Start 10:30 0:30 4.000 9.000 18.000 End 11:00 2:00 13.000 5-Start 11:00 0:30 4.000 9.000 18.000 End 11:30 2:30 13.000 6-Start 11:30 0:30 4.000 8.500 17.000 End 12:00 3:00 12.500 7-Start 12:00 0:30 4.000 8.500 17.000 End 12:30 3:30 12.500 8-Start 12:30 0:30 4.000 7.250 14.500 End 13:00 4:00 11.250 9-Start 13:00 0:30 4.000 7.250 14.500 End 13:30 4:30 11.250 10-Start 13:30 0:30 4.000 7.250 14.500 End 14:00 5:00 11.250 11-Start 14:00 0:30 4.000 7.250 14.500 End 14:30 5:30 11.250 12-Start 14:30 0:30 4.000 7.250 14.500 End 15:00 6:00 11.250 PERCOLATION TESTING FIELD DATA Proiect Name and Test Location: 3229 Hiqhland Drive, Carlsbad, CA, 92008 Test pit#: 3 Hole diameter (in): 6 Test By: JV Hole depth (in): 24 Liquid Used: Water uses Class: SM Date of Test: 6/22/2023 Deoth to Water Table: > 10 feet Liquid Level Maintained by usinq: Manually Additional Comments: Time Time Dt (min) Readings interval (hr:min) & Total Depth to Percolation Rate (in/hr) Remarks Water (in.) ~H (in) 1-Start 9:00 0:30 4.000 11.000 22.000 End 9:30 0:30 15.000 2-Start 9:30 0:30 4.000 11.000 22.000 End 10:00 1:00 15.000 3-Start 10:00 0:30 4.000 10.500 21.000 End 10:30 1:30 14.500 4-Start 10:30 0:30 4.000 10.500 21.000 End 11:00 2:00 14.500 5-Start 11:00 0:30 4.000 10.500 21.000 End 11:30 2:30 14.500 6-Start 11:30 0:30 4.000 10.000 20.000 End 12:00 3:00 14.000 7-Start 12:00 0:30 4.000 10.000 20.000 End 12:30 3:30 14.000 8-Start 12:30 0:30 4.000 9.000 18.000 End 13:00 4:00 13.000 9-Start 13:00 0:30 4.000 8.500 17.000 End 13:30 4:30 12.500 10-Start 13:30 0:30 4.000 8.500 17.000 End 14:00 5:00 12.500 11-Start 14:00 0:30 4.000 8.500 17.000 End 14:30 5:30 12.500 12-Start 14:30 0:30 4.000 8.500 17.000 End 15:00 6:00 12.500 PERCOLATION TESTING FIELD DATA Project Name and Test Location: 3229 Highland Drive, Carlsbad, CA, 92008 Test pit#: 4 Hole diameter (in): 6 Test By: JV Hole depth (in): 24 Liquid Used: Water uses Class: SM Date of Test: 6/22/2023 De_pth to Water Table: > 10 feet Liquid Level Maintained by using: Manually Additional Comments: Time Time Dt (min) Readings interval (hr:min) & Total Depth to Percolation Rate (in/hr) Remarks Water (in.) 6H (in) 1-Start 9:00 0:30 4.000 8.500 17.000 End 9:30 0:30 12.500 2-Start 9:30 0:30 4.000 8.000 16.000 End 10:00 1:00 12.000 3-Start 10:00 0:30 4.000 6.000 12.000 End 10:30 1:30 10.000 4-Start 10:30 0:30 4.000 5.000 10.000 End 11 :00 2:00 9.000 5-Start 11:00 0:30 4.000 4.500 9.000 End 11:30 2:30 8.500 6-Start 11:30 0:30 4.000 4.500 9.000 End 12:00 3:00 8.500 7-Start 12:00 0:30 4.000 4.500 9.000 End 12:30 3:30 8.500 8-Start 12:30 0:30 4.000 4.500 9.000 End 13:00 4:00 8.500 9-Start 13:00 0:30 4.000 4.500 9.000 End 13:30 4:30 8.500 10-Start 13:30 0:30 4.000 4.500 9.000 End 14:00 5:00 8.500 11-Start 14:00 0:30 4.000 4.500 9.000 End 14:30 5:30 8.500 12-Start 14:30 0:30 4.000 4.500 9.000 End 15:00 6:00 8.500 Appendix D: Geotechnical Engineer Analysis endix D Geo echnica E Ana ysis ~nee D.1 Analysis of Infiltration Restrictions This section is only applicable if the analysis of infiltration restrictions is performed by a licensed engineer practicing in geotechnical engineering. The SWQMP Preparer and Geotechnical Engineer must work collaboratively to identify any infiltration restrictions identified in Table D.1-1 below. Upon completion of this section, the Geotechnical Engineer must characterize each DMA as Restricted or Unrestricted for infiltration and provide adequate support/discussion in the geotechnical report. A DMA is considered restricted when one or more restrictions exist which cannot be reasonably resolved through site design changes. Table D.1-1: Considerations for Geotechnical Analysis oflnfiltration Restrictions Restriction Element BMP is within 100' of Contaminated Soils BMP is within 100' of Industrial Activities Lacking Source Control BMP is within 100' of Well/Groundwater Basin BMP is within SO' of Septic Tanks/Leach Fields BMP is within 1 O' of Groundwater Table BMP is within Hydric Soils BMP is within Highly Liquefiable Soils and has Connectivity to Structures BMP is within 1.5 Times the Height of Adjacent Steep Slopes (2':25%) County Staff has Assigned ''Restricted" Infiltration Category BMP is within Predominantly Type D Soil BMP is within 1 0' of Property Line BMP is within Fill Depths of 2':S' (Existing or Proposed) BMP is within 1 0' of Underground Utilities BMP is within 250' of Ephemeral Stream Other (Provide detailed geotechnical support) Based on examination of the best available information, Is Element Applicable? (Yes/No) IIIIDDIIIII I have not identified any restrictions above. Unrestricted Based on examination of the best available information, D I have identified one or more restrictions above. Restricted Table D.1-1 is divided into Mandatory Considerations and Optional Considerations. Mandatory D-1 Jan.2024 Appendix D: Geotechnical Engineer Analysis Considerations include elements that may pose a significant risk to human health and safety and must always be evaluated. Optional Considerations include elements that are not necessarily associated with human health and safety, so analysis is not mandated through this guidance document. All elements presented in this table are subject to the discretion of the Geotechnical Engineer if adequate supporting information is provided. Applicants must evaluate infiltration restrictions through use of the best available data. A list of resources available for evaluation is provided in Section B.2 D.2 er inati 0 sign lnfiltra ion a es This section is only applicable if the determination of design infiltration rates is performed by a licensed engineer practicing in geotechnical engineering. The guidance in this section identifies methods for identifying observed infiltration rates, corrected infiltration rates, safety factors, and design infiltration rates for use in structural BMP design. Upon completion of this section, the Geotechnical Engineer must recommend a design infiltration rate for each DMA and provide adequate support/ discussion in the geotechnical report. Table D.2-1: Elements for Determination of Design Infiltration Rates Item Value Unit - Initial Infiltration Rate qr) Identify per Section D.2.1 in/hr Corrected Infiltration Rate \ ;7:J Identify per Section D.2.2 in/hr Safety Factor Identify per Section D.2.3 ~✓i6 unitless Design Infiltration Rate 0,~i in/hr Corrected Infiltration Rate -;.. Safety Factor D-2 Jan.2023 Consideration Suitability Assessment (A) Design (B) Appendix D: Geotechnical Engineer Analysis Table D.2-3: Determination of Safety Factor Assigned Factor Product (p) Weight (w) Value (v) p=wxv Infiltration Testing Method 0.25 o.s Soil Texture Class 0.25 Refer to o.s Soil Variability 0.25 Table D.2-4 G ,1-S Depth to Groundwater/Obstruction 0.25 O ,J .. C: Suitability Assessment Safety Factor, SA = I:p \ .c; Pretreatment 0.50 \.o Resiliency 0.25 Refer to 0 :~ TableD.2-4 Compaction 0.25 o.~ Design Safety Factor, Sa = I:p L2~ Safety Factor, S = SA x Sa ~,~5 (Must be always greater than or equal to 2) The geotechnical engineer should reference Table D.2-4 below in order to determine appropriate factor values for use in the table above. The values in the table below are subjective in nature and the geotechnical engineer may use professional discretion in how the points are assigned. D-12 Jan.2023