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MEMORANDUM TO: Michael Kith, REHS San Joaquin Environmental Health Department FROM: Norman Hantzsche, PE, Questa Engineering Corporation DATE: July 16, 2020 SUBJECT: OWTS Design Review, 16475 Tide Road, Ripon Project Overview The project is for the development of a 4-bedroom single family residence on a 0.94-acre parcel near the intersection of French Camp Road and Tide Road in a rural residential-agricultural area north of Ripon and east of Manteca. A Nitrate Loading Study (NLS)was completed by Petralogix Engineering(May 2020 Addendum), which concluded that onsite wastewater disposal for the proposed residence would result in a long-term nitrate loading impact to groundwater beneath the site of approximately 15.3 mg-N/L,which is in excess of the County maximum criterion of 10 mg-N/L. In their NLS approval letter of May 19, 2020, the Environmental Health Department required nitrate loading mitigation, and indicated the need to utilize a supplemental treatment system compliant with performance standards in Section 10.9 of the State/Regional Water Board Policy for OWTS. Section 10.9 specifies that the system must provide an average of at least 50%removal of nitrogen(effluent compared to influent) and that, to be approved, the system must be certified by NSF (National Sanitation Foundation) or by another approved third party testing authority. A nitrate mitigation design was submitted to the Environmental Health Department by Chesney Consulting, dated June 15, 2020. The design by Chesney proposes to modify the leachfield into a soil-geosynthetic aggregate filter bed to cultivate the growth of fescue grass in order to aid in uptake and removal of excess nitrogen contained in the wastewater effluent disposed to the filter bed. I have reviewed this proposed nitrate mitigation plan and provide my comments below. Comments on Nitrate Mitigation Using Fescue Grass The Chesney plan for nitrogen mitigation using fescue grass uptake is not compliant with Section 10.9 of the State OWTS Policy and has other problems that I believe will cause the wastewater disposal field system to fail. It should not be approved as proposed. 1. Non-compliant with State Policy. The proposed mitigation design is an experimental concept only, and is presented with no documented performance history or certification by NSF or another third parry tester as required by the State OWTS Policy. Under the 1