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°PrEnvironmental Health Department <br /> SANJOAQUIN <br /> COUNTY Linda Turkatte, REHS, Director <br /> Greatness grows here. Kasey Foley,REHS,Assistant Director <br /> PROGRAM COORDINATORS <br /> Robert McClellon,REHS <br /> Jeff Carruesco, REHS, RDI <br /> Willy Ng,REHS <br /> April 12, 2019 Muniappa Naidu, REHS <br /> Michael Kith,REHS <br /> Don Chesney <br /> Chesney Consulting <br /> P O Box 3794 <br /> Turlock, CA 95381 <br /> RE: Soil Suitability/ Nitrate Loading Study <br /> 12927 West Ripon Road, Ripon, APN 22817008 <br /> Service Request SR0080225 <br /> The San Joaquin County (SJC) Environmental Health Department (EHD) has received on February 20, 2019 <br /> the Nitrate Loading — Soil Suitability Study dated February 14, 2019 (the Study), and the Soil Suitability/ <br /> Nitrate Loading Studies Report Addendum dated March 29, 2019 (the Addendum), for the above-referenced <br /> address. EHD has the following comments: <br /> The Study was prepared to address the additional nitrate loading between the proposed second unit dwelling <br /> and the existing single family resident for a total of 6 bedrooms on the 1.46-acre lot. Using the <br /> Hantzsche/Finnemore formula, the Study reported a potential impact to groundwater from wastewater <br /> generated from the above-mentioned proposed scenario of 21.8 parts per million (ppm) of nitrate as nitrogen, <br /> which is above the Maximum Contaminant Level for nitrate as nitrogen is 10 mg/L for drinking water. <br /> The Study proposed placing 2 inches of sawdust material on the floor of the filter bed to mitigate the increased <br /> potential nitrate load to groundwater as a result of the above proposed project. In addition to the Study, Mr. <br /> Chesney also stated during two telephone conversations on March 26 and April 2, 2019, that placing the <br /> sawdust (organic matter) on the soil-effluent surface would increase the carbon-to-nitrogen (C/N) ratio and <br /> enhance the substrate for biomat building, thus enhancing the microbial activities and reduction of total <br /> nitrogen. The Addendum addressed sources of the Study's claim on the effect of C/N.ratio on microbial <br /> activities and nitrogen removal, and proposed using Soil Solution Access Tube (SSAT) to monitor the <br /> effectiveness of the sawdust enhancement proposal. <br /> Pursuant to Section 7.1 of the San Joaquin County Sewage Standards (Sewage Standards), these features <br /> would be considered an alternative treatment system, defined as "standard systems with additional <br /> enhancements above the required minimum to augment the treatment capabilities of the system...", including <br /> "additional septic tank capacity, additional length of leach lines, or the addition of organic material under the <br /> leach line." <br /> In addition to the Hantzche and Finnemore calculation, the EHD considered several other factors in evaluating <br /> the potential impact of the proposed alternative system, and to determine if supplemental treatment would be <br /> necessary to protect the beneficial uses of groundwater. In conducting this evaluation, the following additional <br /> factors were considered: <br /> 1. The lot is an existing historical parcel, nonconforming for Onsite Wastewater Treatment System <br /> (OWTS). The parcel size is 1.46 acres and does not meet the current minimum density requirement <br /> for OWTS usage and requires a variance. <br /> 1868 E. Hazelton Avenue I Stockton, California 95205 1 T 209 468-3420 1 F 209 464-0138 1 www.sjcehd.com <br />