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Quantity and Quality of Domestic Wastewater Mr. Davis indicated that two new three-bedroom homes, a two-bedroom home, and three one-bedroom homes will be constructed on the Site. A three-bedroom home is currently located on the Site. Although some of the development was discussed in the previous Soil Suitability/Nitrate Loading Study (LOGE, 2020), the full project will be re- evaluated here. Crites and Tchobanoglous (1998) list a typical flow rate of 50 to 70 gallons per person per day for an individual residence. In the past, San Joaquin County Environmental Health Department has requested that the flow rate be calculated as 140 gallons per bedroom per day to reflect maximum usage. On March 4, 2020, however, Michael Kith of the San Joaquin County Environmental Health Department dictated a new procedure 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, a three-bedroom house would contribute 200 gpd, a two-bedroom house would contribute 150 gpd, and a one-bedroom house would contribute 100 gpd. The total wastewater flow rate would be calculated as (3 x 200) + 150 + (3 x 100), or 1,050 gpd. A typical residential concentration of 35 mg/L of nitrate as N was selected for the proposed residences (Crites and Tchobanoglous, 1998). 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 incorporates 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 (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. LOGE 2119 Page 8