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Home My WebLink AboutCDP 2020-0024; TOYOTA CARLSBAD; ADDITIONAL PERCOLATION TESTING AND LIMITED INFILTRATION EVALUATION; 2021-03-08 March 8, 2021 CTE Job No. 10-15029G Stellar Properties, LLC Attention: Ms. Judy Jones-Cone 6030 Avenida Encinas Carlsbad, California Telephone: (760) 496-2931 Via Email: jjones-cone@toyotacarlsbad.com Subject: Additional Percolation Testing and Limited Infiltration Evaluation Proposed Sales Building at Toyota Carlsbad 5434 Paseo Del Norte Carlsbad, California Reference: Construction Testing and Engineering, Inc., 2019, Geotechnical Investigation, Proposed Sales Building, Toyota Carlsbad, California, Job No. 10-15029G, dated August 2. Ms. Judy Jones-Cone: As requested, Construction Testing and Engineering, Inc. (CTE) provides additional percolation and calculated infiltration rates pertinent to the proposed stormwater BMP’s for the revised retention basin locations. This testing was performed in general accordance with the San Diego Region Model BMP (Best Management Practice) Design Manual”, Appendix C and Appendix D, dated February 2016. The work included test hole excavation, percolation testing, and preparation of this summary report. The attached Figure 1 shows the layout and approximate percolation test locations. References are included in Appendix A. 1.0 PERCOLATION TESTING The test locations and associated depths were determined by the civil engineer and from evaluation of project plans provided by the general contractor. The test holes were excavated with manually operated auger equipment to depths ranging from approximately 5.1 to 5.3 feet below the ground surface. The evaluation was performed in accordance with Appendix C of the San Diego Region Model BMP Design Manual “Geotechnical and Groundwater Investigation Requirements”, dated February 2016. 1.1 Field Exploration The two recent percolation test holes were excavated with a manually advanced six-inch diameter auger on March 5, 2021. The test holes were excavated such that the percolation testing was performed in the areas of proposed BMP’s and to characterize representative infiltration conditions at the site. Construction Testing & Engineering, Inc. Inspection I Testing I Geotechnical I Environmental & Construction Engineering I Civil Engineering I Surveying 1441 Montiel Road, Suite 115 I Escondido, CA 92026 I Ph (760) 746-4955 I Fax (760) 746-9806 I www.cte-inc.net Additional Percolation Testing and Limited Infiltration Evaluation Page 2 Proposed Sales Building at Toyota Carlsbad 5434 Paseo Del Norte Carlsbad, California March 8, 2021 CTE Job No. 10-15029G \\file01\CTE Share\Projects\10-15000 to 10-15999 Projects\10-15029G\Ltr_Infiltration Evaluation Results (3-8-21).doc 1.2 Soil Materials According to geologic mapping by Kennedy and Tan (2008), and as observed and described in the referenced soils report, the site is generally underlain by Quaternary Undocumented Fill and Old Paralic Deposits, Unit 6. The percolation tests were performed in Quaternary Old Paralic Deposits-Unit 6 (Qop6). This unit generally consisted of silty fine to medium grained sand to poorly graded fine to medium grained sand. 1.3 Percolation Test Methods The percolation tests were performed in accordance with methods approved by the San Diego BMP Design Manual approximately 18 to 21 hours after the four-hour presoak period. Percolation test results and calculated infiltration rates are presented below in Table 2.0. Field Data and percolation to infiltration calculations are included in Appendix B. 2.0 CALCULATED INFILTRATION RATE As per the San Diego Region BMP design documents (2016) infiltration rates are to be evaluated using the Porchet Method. San Diego BMP design documents utilize the Porchet Method through guidance of the County of Riverside (2011). The intent of calculating the infiltration rate is to take into account bias inherent in percolation test borehole sidewall infiltration that would not occur at a basin bottom where such sidewalls are not present. The infiltration rate (It) is derived by the equation: It = ΔH πr2 60 = ΔH 60 r Δt(πr2 +2πrHavg) Δt(r+2Havg) Where: It = tested infiltration rate, inches/hour ΔH = change in head over the time interval, inches Δt = time interval, minutes * r = effective radius of test hole Havg = average head over the time interval, inches Given the measured percolation rates, the calculated infiltration rates are presented with and without a Factor of Safety applied in Table 2.0 below. The civil engineer of record completed Form I-9 of the San Diego Region Best Management Practice Design Manual, Appendix D and determined that a factor of safety of 2.81 is appropriate for the site. Additional Percolation Testing and Limited Infiltration Evaluation Page 3 Proposed Sales Building at Toyota Carlsbad 5434 Paseo Del Norte Carlsbad, California March 8, 2021 CTE Job No. 10-15029G \\file01\CTE Share\Projects\10-15000 to 10-15999 Projects\10-15029G\Ltr_Infiltration Evaluation Results (3-8-21).doc TABLE 2.0 RESULTS OF PERCOLATION TESTING WITH FACTOR OF SAFETY APPLIED Test Location Test Depth Soil Type* Percolation Rate (inches per hour) Infiltration Rate (inches per hour) Infiltration Rate with FOS of 2.81 Applied (inches per hour) (inches) Case (USCS Classification) P-5 63 III Qop 4.750 0.857 0.429 P-6 61 III Qop 1.500 0.247 0.123 NOTES: Water level was measured from a fixed point at the top of the hole. Weather was clear during the percolation testing. Qop = Quaternary Old Paralic Deposits The test holes were six inches in diameter. 3.0 CONCLUSIONS The percolation test results were obtained in general accordance with regional standards. However, it should be noted that percolation test results can significantly vary laterally and vertically due to slight changes in soil type, degree of weathering, secondary mineralization, and other physical and chemical variabilities. As such, the test results are considered to be an estimate of percolation and converted infiltration rates for design purposes. No guarantee is made based on the percolation testing related to the actual functionality or longevity of associated infiltration basins or other BMP devices designed from the presented infiltration rates. 4.0 LIMITATIONS This letter is subject to the same limitations as previous CTE geotechnical documents issued for the subject project. CTE’s conclusions and recommendations are based on an analysis of the observed conditions. If conditions different from those described in this report are encountered during construction, this office should be notified and additional recommendations, if required, will be provided. Additional Percolation Testing and Limited Infiltration Evaluation Page 4 Proposed Sales Building at Toyota Carlsbad 5434 Paseo Del Norte Carlsbad, California March 8, 2021 CTE Job No. 10-15029G \\file01\CTE Share\Projects\10-15000 to 10-15999 Projects\10-15029G\Ltr_Infiltration Evaluation Results (3-8-21).doc The opportunity to be of service on this project is appreciated. If you have any questions regarding this report, please do not hesitate to contact the undersigned. Respectfully submitted, CONSTRUCTION TESTING & ENGINEERING, INC. Dan T. Math, GE #2665 Aaron J. Beeby, CEG #2603 Principal Engineer Senior Geologist Attachments: Figure 1 Percolation Test Location Map Appendix A References Appendix B Percolation to Infiltration Calculations and Field Data P-1 P-2 P-4 Qop Tsa P-3 P-6 P-5 LEGEND Quaternary Old Paralic Deposits overQop Tsa P-6 Approximate Percolation Test Location Tertiary Santiago Formation CJ'I ~ "C ,.....:.. N I 00 I I"") ........, Q) I,_ ::J CJ'I ii: / c., 0) N 0 I{) ...... I 0 ;;, "' +-' u .5!; 0 I,_ a.. 0) 0) 0) I{) ...... I 0 0 +-' 0 0 0 I{) ...... I 0 ;;, 211-060-17 5444 PASEO DEL NORTE -·--·- ---.- " I ( I f1:ll"--t~~~:I_/ SD - / I I I I I I I I I I I I I I! 8 l tr-/ 1:o- , I P~OPOSED BUll!DING I SD /SD 1-;~1 ) / I / / / I / 137.3' i I I I I _"]-(OS -\ ) \ _r I \I I I I I I 6 ( I/ :1 I I 1::· " I:: S67' 28' 48"W 494.59' 50' 0 25' 50' I r "' +-' a.. -~•-----:~~;::--------------.---PE_R_c_o_T_ •1TI_O_N_TE_ST_L_o_c•-1TI_o_N_"l .. -.n----.1'11111""'1111""'111111'!'-...J C~E'P 2\\\ Construction Testing & Engineering, Inc. ~ a mAC / I ~ L 7\ Tr' PROPOSED TOYOTA CARISBAD SALES BUILDING en "---~)'·}-;• 1441 Montiel Rd Ste 115, Escondido, CA 92026 Ph (760) 746-4955 5434 PASEO DEL NORTE ~ CARLSBAD, CALIFORNIA APPENDIX A REFERENCES 1. Construction Testing and Engineering, Inc., 2019, Geotechnical Investigation, Proposed Sales Building, Toyota Carlsbad, California, Job No. 10-15029G, dated August 2. 2. __________, 2020, Update to Geotechnical Investigation, Proposed Sales Building at Toyota Carlsbad, 5434 Paseo Del Norte, Carlsbad, California, Job No. 10-15029G, dated January 30. APPENDIX B PERCOLATION TO INFILTRATION CALCULATIONS AND FIELD DATA P‐5 Total Depth: 63 inches Time Test Interval Time Test Refill Water Level Initial/Start Water Level End/Final Incremental Water Level Change Percolation Rate Percolation Rate (minutes) Depth /Inches Depth /Inches Depth /Inches (inches) inches/minutes inches/hour 8:30:00 Initial None 0.00 initial ‐ 9:00:00 30 55 0.00 59.00 59.00 1.97 118.00 9:30:00 30 55 55.00 57.50 2.50 0.08 5.00 10:00:00 30 55 55.00 57.50 2.50 0.08 5.00 10:30:00 30 54.5 55.00 57.38 2.38 0.08 4.75 11:00:00 30 55 54.50 57.00 2.50 0.08 5.00 11:30:00 30 54.5 55.00 57.38 2.38 0.08 4.75 12:00:00 30 55 54.50 56.88 2.38 0.08 4.75 12:30:00 30 NO 55.00 57.38 2.38 0.08 4.75 P‐6 Total Depth: 61 inches Time Test Interval Time Test Refill Water Level Initial/Start Water Level End/Final Incremental Water Level Change Percolation Rate Percolation Rate (minutes) Depth /Inches Depth /Inches Depth /Inches (inches) inches/minutes inches/hour 8:32:00 Initial None 0.00 initial ‐ 9:02:00 30 NO 0.00 54.13 54.125 1.804 108.250 9:32:00 30 53 54.13 54.25 0.125 0.004 0.250 10:02:00 30 NO 53.00 54.00 1.000 0.033 2.000 10:32:00 30 NO 54.00 53.75 ‐0.250 ‐0.008 ‐0.500 11:02:00 30 53 53.75 54.63 0.875 0.029 1.750 11:32:00 30 NO 53.00 53.75 0.750 0.025 1.500 12:02:00 30 53 53.75 54.63 0.875 0.029 1.750 12:32:00 30 NO 53.00 53.75 0.750 0.025 1.500 PERCOLATION TEST DATA Inches Inches ∆t =30 ∆t =30 Df =57.38 Df =53.75 r = 3 r = 3 D0 =55.00 D0 =53.00 DT =63 DT =61 Ho = 8in Ho = 8in Hf =5.625 in Hf =7.25 in ∆H = ∆D = 2.375 in ∆H = ∆D = 0.75 in Havg =6.8125 in Havg =7.625 in It =0.857 in/hr It =0.247 in/hr Test Hole Radius, Test Hole Radius, Initial Depth to Water, Initial Depth to Water, Total Depth of Test Hole, Total Depth of Test Hole, Percolation Rate Conversion P‐5 Percolation Rate Conversion P‐6 Time Interval,Time Interval, Final Depth of Water, Final Depth of Water, - -