SR0085175_SSNL - Laserfiche WebLink

Home Browse Search

Quantitv and Qualitv of Domestic Wastewater Approximately 81 mobile homes and a clubhouse are located on the Site. Mr. Wert stated that the manager of the park lives on-site, and the clubhouse is only used by residents. Mr. Wert provided a self-monitoring tables for January 2021 through January 2022. During this time period, the average influent into the septic system was generally 5,000 to 7,000 gallons per day (gpd), with a maximum of 7,356 gpd experienced in June 2021 (Appendix 7). A typical residential concentration of 35 mg/L of nitrate as N was selected for the existing residences (Crites and Tchobanoglous, 1998). It should be noted that the effluent from the existing septic system is being tested and reported quarterly to the California Regional Water Quality Control Board. Mr. Wert provided results from five quarters of effluent sampling in 2022 and 2021, as well as two quarters of effluent sampling in 2020, during which time nitrate was only detected four times total, with values ranging from 0.23 to 11 mg/L-N (Appendix 7). If these values were utilized in the nitrate loading calculation, the predicted maximum buildup of nitrates in the aquifer from the use of the septic system would be substantially lower than that calculated here. Nevertheless, the standard residential concentration of 35 mg/L-N is selected for the calculation to represent the situation if no treatment were taking place. 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 (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 denitrification factor of 35 percent was selected for the Site because of the clayey soil present at the percolation test location and indicated by the Soil Survey. Nitrate Loading Estimate A nitrate loading scenario was employed to determine the impact from the proposed project to ground water. The scenario utilizes the variables discussed previously, which LOGE 2218 Page 12