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for calculating residential flow, developed in consultation with Norman Hantzsche (author of the 1992 paper discussed previously). He indicated that wastewater flow from a single-family residence should be calculated as 100 gallons per day (gpd) for the first bedroom and 50 gpd for each additional bedroom; additional residences should be calculated in the same manner (personal communication, March 4, 2020). Using this method, the existing three-bedroom home will contribute an estimated average daily flow of 200 gpd. The potential future three-bedroom second unit dwelling will also contribute 200 gpd, for a total estimated daily flow of 400 gpd for the parcel. A typical residential concentration of 35 mg/L of nitrate as N was selected for the proposed residence (Crites and Tchobanoglous, 1998). 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 (N2) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field 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 standard denitrification factor of 25 percent was selected for the Site because of the mixed silt and sand soil type present at the percolation test location. Nitrate Loading Estimate A nitrate loading scenario was employed to determine the impact from the existing home and potential future second unit dwelling to ground water. The scenario utilizes the variables discussed previously, which represent the estimated conditions and uses associated with this project. The following table presents a summary of the assumptions for the nitrate loading calculation for the Site, as presented in Plate 13. LOGE 2124 Page 12