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LIr Chesney Consulting <br />March 26, 2022 <br />FOR: San Joaquin County Environmental Health Department (EHD) <br />Mr. Steven Shih, REHS, Program Manager <br />1868 Hazelton Ave. <br />Stockton, CA 95205 <br />PROJECT: Mr. David Pinnell's Property <br />8888 West Pine Street <br />Thornton, CA 95686 <br />SUBJECT: Mitigation of Rapid Percolation Report Addendum (Project No. SSD-04.22A) <br />Reference is made to the project indicated above. The EHD has a question regarding the permeability of the soil <br />sampled from the depths referenced in the original Report. The soil sampled from the 48"-54" depth was <br />determined through laboratory analysis to be a silt loam. The category for this soil is Group B. Also determined <br />through laboratory analysis for this Group B soil, is a saturated hydraulic conductivity of 3.6 in/hr (median <br />range), or 16.7 minutes per inch. It is unknown as to whether this saturated hydraulic conductivity correlates on <br />a 1:1 basis with a standard percolation test. What can be stated unequivocally, is that a silt loam soil type would <br />certainly have a percolation rate slower than 5 mpi after four hours of saturated percolation testing. <br />Therefore, based upon Table 1.10.2 of the SJC Onsite Wastewater Treatment System (OWTS) Standards, the <br />minimum soil depth distance from the soil-effluent interface to the water table now becomes eight ft, instead of <br />20 ft. This was the premise of proving this silt loam soil strata exists under the stratum where the perc test was <br />originally conducted. Additionally, 576 ft to the west, underlying soil strata was determined to be an extremely <br />dense loam soil with 18% clay at the 9-10 ft depth. Unquestionably, soil from this stratum would be classified <br />as having extremely slow permeability. This project is an example as to why Section 1.10.2 of the OWTS <br />Standards should be rewritten to allow the civil engineer or geologist to make soil permeability judgments <br />without having to comply with a blanket proclamation. Every project is site-specific. <br />Although it was specified in my Report to install the septic tank six inches above final grade, the EHD wanted <br />plans illustrating that the eight ft separation distance can be achieved. These plans are attached. Additionally, <br />the EHD stipulated a 1,600 gallon septic tank to be installed, instead of a 1,200 gallon tank. <br />If there should be questions regarding this document, please contact the undersigned. <br />Respectfully submitted, <br />CHESNEY C NSULTING <br />Don Ch ney, PE <br />Registered Civil En meer #C75479 <br />Attachment: Separation Distance Plans <br />P.O. Box 3794 Turlock, CA 95381 Li 209.402.1652 DI ddchesney(&charter.net