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Civil, <br /> Environmental <br /> . Et Wo ter <br /> Resources <br /> MEMORANDUM <br /> ENGINEERING CORP. <br /> TO: Kasey Foley, REHS <br /> Interim Director, San Joaquin Environmental Health Department <br /> FROM: Norman Hantzsche, PE, Questa Engineering Corporat/� <br /> DATE: December 10,2019 <br /> SUBJECT: OWTS Design Review for 4700 Lovely Road,Tracy <br /> PROJECT OVERVIEW <br /> The project is for the construction of an Agricultural Building that will be used for storage of <br /> agricultural equipment and implements. The building will have an interior unisex bathroom. <br /> The subject property consists of a 67-acre parcel,primarily an almond orchard, located on the <br /> west side of Bird Road, one-half mile south of Lovely Road, Tracy. An onsite wastewater <br /> system(OWTS)will be installed to accommodate wastewater flows from restroom use by <br /> employees,up to a maximum of five people. <br /> Plans and supporting documentation for the OWTS are contained in the"Nitrate Loading Study, <br /> Soil Suitability Study"by Chesney Consulting, dated October 14,2019. Soils on the site are <br /> reported to be loamy sand and sandy loam,with a percolation rate of approximately 11 min/inch <br /> at 42-inch depth, and an estimated water table depth of 18 feet below existing grade. The <br /> proposed OWTS consists of a standard septic tank and gravity leaching bed,maintaining more <br /> than the minimum required 8-ft vertical separation to groundwater. The anticipated average <br /> wastewater flow is about 30 gpd,based on projected annual wastewater generation of <br /> approximately 10,000 gallons per year. <br /> COMMENTS <br /> The Nitrate Loading Study by Chesney Consulting projects an estimated resultant groundwater <br /> nitrate—nitrogen concentration of 0.13 mg-N/L, well below the 10 mg-N/L drinking water <br /> standard. I agree with the methodology and calculations presented by Chesney with the <br /> exception of the value for rainfall recharge. The study states an assumption of 9.5 inches per <br /> year for average annual rainfall recharge (R value in the Hantzsche-Finnemore equation), based <br /> on the assumption that average recharge is equal to average annual rainfall.This is not <br /> universally true, since there will always be some amount of rainfall lost to runoff, evaporation <br /> from the soil/land surface, and/or transpiration by plants. However,in this particular case it is a <br /> suitable approximation because of the very large size of the property in relation to the very small <br /> wastewater volumes that will be generated. No further analysis or response is required. I <br /> recommend acceptance of the Nitrate Loading Study as submitted. <br /> 1 <br /> Box 70356, 1220 Brickyard Cove Rd.Suite 206 Pt.Richmond,CA 94807 T.510/236.6114 F.510/236.2423 E:Questa@QuestaEC.com <br />