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Nitrogen Loading Study Report Page 3 <br /> 24754 EAST RIVER ROAD <br /> WKA No. 11306.01 <br /> January 13, 2017 <br /> Revised: March 7, 2017 <br /> 5.3 On-Site Sources of Nitrogen <br /> On-site sources of nitrogen are assumed to be limited to the septic systems. Mass balance <br /> calculations are based on four employees for the East Septic System and three employees for <br /> the South Septic System. Water use was determined to be 15 gallons per person per day for an <br /> industrial building with no food cafeteria based on San Joaquin County's Onsite Wastewater <br /> Disposal Standards. Total nitrogen for untreated domestic wastewater typically ranges from 20 <br /> milligrams per liter mg/L to 70 mg/L (Metcalf and Eddy, 2004). <br /> 5.4 Future On-Site Sources of Nitrogen <br /> There are no anticipated future on-site sources of nitrogen to soil and groundwater. <br /> 5.5 Mass Balance of Nitrogen Loading <br /> The resultant average concentration of nitrate-nitrogen was calculated using a mass balance <br /> considering only inputs from wastewater and recharge of rainfall and losses due to <br /> denitrification, per the Hantzsche-Finnemore equation (Equation 1). <br /> nr _ tnw(l—d))) Rnb (Equation 1) <br /> Parameter Description Units <br /> nr Average concentration of nitrate-nitrogen in recharge water mg/L <br /> I Volume rate of wastewater entering soil averaged over the gross developed area in/yr <br /> nw Total nitrogen concentration of wastewater mg/L <br /> d* Fraction of nitrate-nitrogen loss due to denitrification in soil unitless <br /> R Average recharge rate of rainfall in/yr <br /> nb Background nitrate-nitrogen concentration of rainfall recharge mg/L <br /> *Assumed no nitrogen losses due to denitrification(d=0) <br /> A summary of the nitrogen mass balance for the Site is provided in Tables 1 and 2. Two cases <br /> were calculated using the high and low estimates (70 mg/L and 20 mg/L) for the amount of total <br /> nitrogen in domestic wastewater. The concentration of total nitrogen in storm water runoff was <br /> assumed to be 1.91 mg/L in both cases. A summary of the high and low estimates is shown in <br /> the tables and calculations below. <br />