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July 24, 2020 Irerracon <br /> Ms. Marina Nunez <br /> Kitchell CEM Inc. RECEIVED <br /> 5151 Pacific Avenue <br /> Stockton, California 95207 <br /> JUL 312020 <br /> Phone: (209) 954-5741 ENVIRONMENTAL HEALTH <br /> DEPARTMENT <br /> Email: mnunez(cDkitchell.com <br /> Re: Soil Suitability / Nitrate Loading Study Addendum <br /> Manteca Farm Improvements, APN: 197-040-06 <br /> 5298 E. Brunswick Road <br /> Manteca, San Joaquin County, California <br /> Terracon Project No. NA197073 <br /> Dear Ms. Nunez, <br /> Per your request, we have prepared an addendum to our Soil Suitability Study and Nitrate Loading <br /> Study (SSNLS) dated October 19, 2019 (Terracon Project No. NA197073). In February 2020,the <br /> EHD approved an adjustment to the evapotranspiration (ET) rate and net rainfall recharge based <br /> on the University of California (UC) plant factors (PF) for established landscape plants. We <br /> understand the San Joaquin County Environmental Health Department(EHD)submitted our 2019 <br /> SSNLS report to a 3rd party reviewer and the purpose of the addendum letter is to update our <br /> nitrate loading calculation based on the revised net rainfall recharge data. Terracon was provided <br /> with a copy of the Delta College Manteca Farm Water Balance Recharge Analysis and <br /> Wastewater Nitrogen Loading Analysis — Calculations for Delta College Manteca Farm. Upon a <br /> review of the Delta College Manteca Farm Water Balance Recharge Analysis Terracon concurs <br /> with the overall method. However, we used evapotranspiration and precipitation data collected <br /> from CI MIS and calculated net rainfall recharge at 9.39 inches per year(Refer to Terracon's Water <br /> Balance Analysis in the Attachments). <br /> Terracon's October 2019 SSNLS reported the site consisted of a 14.0 acre parcel. The estimated <br /> deep percolation of rain calculated to be 2.70 inches. The average total concentration of <br /> wastewater was considered to be 85 mg/L-N with a leachfield denitrification factor of 10%. The <br /> combined nitrate loading balance for the existing and proposed land use was calculated at 23.3 <br /> milligrams per liter nitrogen (mg/L-N) above the EPA maximum contaminant level (MCL) of 10 <br /> mg/L-N. The site is currently improved with two septic systems (Septic System No. 1 and No. 2). <br /> A third septic system (No. 3) is proposed to be installed for the new agricultural building. As septic <br /> system No. 2 will be removed it is not included in the revised nitrate loading balance. At the <br /> instruction of the EHD, Terracon combined the average daily flow rates for septic system No. 1 <br /> and No. 3 together rather than calculating a separate nitrate loading balance for each system <br /> Terracon Consultants Inc. 902 Industrial Way Lodi, CA 95240-3106 <br /> P 209-367-3701 F 209-333-8303 terracon.com <br />