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Table 5. Weighted Average Concentration Calculation, Parcel 1 <br />Use Average Daily Estimated Waste Weighted Average <br />Flow Water Quality Product <br />Residence 150 gpd 35 mg/L-N 5,250.0 gpd-mg/L-N <br />Shop Restroom 0.7 gpd 85 mg/L-N 59.5 gpd-mg/L-N <br />Totals 150.7 gpd 5,309.5 gpd-mg/L-N <br />Weighted Average 5,309.5 gpd-mg/L-N / 150.7 gpd = 35.2 mg/L-N <br />Concentration: <br />Parcel 2 <br />There is currently no development on Parcel 2. Based on the assumption of the nitrate <br />loading method that only septic systems should be considered for the calculation, the <br />wastewater flow from Parcel 2 will be zero. For the purpose of the nitrate loading <br />analysis, however, a hypothetical four-bedroom home and three-bedroom second unit <br />dwelling will be considered for that parcel. This calculation is included so that, should <br />the owner at some point in the future decide to build on the land, nitrate loading will <br />have been addressed. <br />Based on the San Joaquin County Environmental Health Department method described <br />above, the hypothetical four-bedroom home would contribute 250 gpd, and the three- <br />bedroom home would contribute 200 gpd, for a total estimated average daily flow of 450 <br />gpd. <br />The estimated flow values discussed here should not be used for the design and sizing <br />of the septic system. The design and sizing of the septic system should utilize the San <br />Joaquin County Environmental Health Department On -Site Wastewater Treatment <br />Systems Standards, which incorporates peak and surge flow factors. The estimates <br />used in the On -Site Wastewater Treatment Systems Standards may be greater than <br />those discussed here. <br />Denitrification Reductions <br />Denitrification is a process that occurs in the septic system drain field whereby certain <br />bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (NZ) to the <br />atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain <br />field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay <br />content, moist soil conditions, high pH, and organic material denitrify by about 35 <br />LOGE 2150 Page 13 <br />