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calculation shown, the estimated rate of recharge from percolating waters for the Staten Island station is determined to be 12.60 inches (Plate 16). A statistical error of 49 percent is associated with this value. The two stations are then averaged, for a regional deep percolation value of 8.16 inches. The nitrate concentration of the recharge waters was estimated to be 1 mg/L-N (Hantzsche and Finnemore). Quantity and Quality of Domestic Wastewater Mr. Williams indicated that he plans to construct two new four-bedroom houses on the Site. _`----- Crites and Tchobanoglous (1998) list a typical flow rate of 50 to 70 gallons per person per day for an individual residence. The San Joaquin County Environmental Health Department has indicated that maximum flow and double occupancy within each bedroom should be considered for the nitrate loading assessment; as a result, a value of 140 gallons per bedroom per day has been selected (personal __communication, January 6, 2017). The maximum daily flow for'the Site was estimated to be 1,120 gallons per day (gpd), based on eight bedrooms at 140 gallons per bedroom. A typical residential concentration of 35 mg/L of nitrate as N was selected for the/�, proposed residence (Crites and TFhobanoglous,,998). The estimated flow values discussed here should not be used for the design and sizing of the septic system. The design and sizing of the septic system should utilize the San Joaquin County Environmental Health Department On-Site Wastewater Treatment Systems Standards which incorporate peak and surge flow factors. The estimates used in the On-Site Wastewater Treatment Systems Standards may be greater than those discussed here. Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (Nz) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field will may undergo a reduction between 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content tend to denitrify at a lower rate of about 10 percent. A denitrification factor of 35 percent was selected for the Site because of the clayey soil present at the percolation test locations. LOGE 1919 Page 10