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v ofess <br />ed D. Ch '/ %.% cs- sot% e 0 , <br />N0.75479 <br />.., <br />1:4) co .-• <br />Civil <br />Of Ca10-° <br />I Chesney Consulting <br />February 27, 2022 <br />FOR: San Joaquin County Environmental Health Department (EHD) <br />Mr. Jeffrey Wong, REHS <br />1868 Hazelton Ave. <br />Stockton, CA 95205 <br />PROJECT: Dan R. Costa, Inc. <br />17239 East Louise Road <br />Escalon, California 95320 <br />SR0084773 <br />SUBJECT: Soil Suitability/Nitrate Loading Study Addendum <br />Reference is made to the project indicated above. The EHD has a question regarding the factor used in the <br />Nitrate Loading Study for this project. A total nitrogen concentration in the calculated wastewater flow <br />volume used in the loading equation is a lower figure than what is typically used. Although the existing <br />office is currently on an onsite wastewater treatment system (OWTS), it could not be sampled to due <br />inaccessibility. <br />Over the past three decades, numerous OWTS have been sampled to accurately quantify nitrogen <br />concentrations for Nitrate Loading Studies. Typically, commercial treatment systems have higher total <br />nitrogen (TKN) content than do residential systems. A typical residential concentration of 45 mg/L was <br />inadvertently used in the calculations instead of a typical commercial system TKN concentration of 90 mg/L <br />(when actual chemistries are unavailable). <br />By doubling the TKN concentration to 90 mg/L, obviously doubles the potential nitrate loading to the <br />underlying groundwater. The new resultant concentration (Nr) is theoretically 1.12 mg/L, not 0.61 mg/L. <br />The new Nr is approximately one-tenth of the nitrate Maximum Contaminant Level (MCL) of 10 mg/L. <br />This low concentration is due to the fact that the project consists of 40.36 acres, thus significantly diluting <br />the calculated concentration. <br />If there should be questions regarding this document, please contact the undersigned. <br />Respectfully submitted, <br />CHESNEY CONSULTING <br />Don Che ey, PE <br />Registered Civil Engi eer #C75479 <br />P.O. Box 3794 [:11 Turlock, CA 95381 209.402.1652 L ddc.hesneyPc.harter.net