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Civil, <br /> Environmen tol <br /> . Et Water <br /> Resources <br /> MEMORANDUM <br /> ENGINEERING CORP. <br /> TO: Linda Turkatte,REHS <br /> Director, San Joaquin Environmental Health Department <br /> FROM: Norman Hantzsche,PE, Questa Engineering Corporatiifi�. <br /> DATE: November 13,2019 <br /> SUBJECT: OWTS Design Review for Navu Farms,Inc.,7300 West Delta Ave,Tracy <br /> PROJECT OVERVIEW <br /> The project is for the construction of an Ag Building, an Abattoir and holding pens on <br /> agricultural property at 7300 West Delta Avenue,Tracy. The project spans two adjacent <br /> properties of 36.46 and 3.93 acres,respectively. The onsite wastewater system(OWTS)will be <br /> located on the 36-acre parcel to accommodate wastewater flows from restroom use by the owner <br /> and customers. <br /> Plans and supporting documentation for the OWTS are contained in the"Nitrate Loading Study, <br /> Soil Suitability Study and Onsite Wastewater Treatment System Design"by Chesney <br /> Consulting,dated September 6,2019. Soils on the site are reported to be clay loam,with a <br /> percolation rate of 20.8 min/inch at 36-inch depth, and water table found at a depth of 5.7 feet <br /> below existing grade. The proposed OWTS consists of at-grade leaching trenches to maintain a <br /> 5-ft separation to groundwater. The anticipated wastewater flow is less than 50 gpd,based on <br /> projected annual wastewater generation of 17,555 gallons per year. <br /> COMMENTS <br /> 1. Groundwater Separation/Percolation Rate. Based on a percolation rate of 20.8 min/inch, <br /> San Joaquin County regulations require an 8-ft vertical separation to groundwater,rather than <br /> 5-ft separation as proposed. A 5-ft separation is acceptable where the soil percolation rate is <br /> >30 min/inch. Normally several percolation tests(3 to 6)are conducted to provide a <br /> representative characterization of soil conditions in the planned leachfield area. The single <br /> percolation test result of 20.8 min/inch seems fast for clay loam soils. I recommend <br /> conducting additional percolation tests to confirm the percolation rate and corresponding <br /> groundwater separation requirement.Alternatively, if the single percolation test remains as <br /> the basis of design, an alternative wastewater dispersal method, such as a mound system, <br /> would be necessary to address the reduced separation to groundwater provided. <br /> 1 <br /> Box 70356, 1220 Brickyard Cove Rd.Suite 206 Pt.Richmond,CA 94807 T.510/236.6114 F.•510/236.2423 E.QuestaOQuestaEC.com <br />