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Mr.Jim Hoagland <br /> January 19,2004 <br /> Page 13 <br /> 7.1 Quantity of Quality of Domestic Wastewater From Proposed Project <br /> ` The average total nitrogen concentration of the domestic waste water is normally considered to <br /> be 20-85 mg/L-N(Crites and Tchobanoglous, 1998).For the purpose of the nitrate loading <br /> ` estimate, the long-term average concentration for total nitrogen in waste water is estimated to be <br /> -35 mg/L-N.. ai --A t o qlL, <br /> 7.2 Quantity and Quality of Deep Percolating Rain Water <br /> An estimate of the quantity and quality of rainfall was required for the analysis. The estimate of <br /> ., deep percolation of rain is based on the average monthly precipitation of rain fall and <br /> evapotranspiration for Lodi, California. The estimate first determines whether the average <br /> monthly precipitation exceeds average monthly potential ET. If so, then the difference is <br /> potential deep percolation. This method does not consider runoff. See Plate 8 for the data and <br /> calculation. <br /> �- Average potential evapotranspiration was obtained from the California Irrigation Management <br /> Information System (CIMIS). Stockton is located within evapotranspiration zone number 12. <br /> The average rain fall for the Lodi area was obtained from the USDA(1992) Soil Survey for San <br /> Joaquin County. <br /> Based on this estimate,the average deep percolation of rain for the Stockton area is estimated to <br /> ` be 5.01 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N whose <br /> maximum contaminate limit for drinking water is 10 mg/L-N(Hantzsche and Finnemore, 1992). <br /> 7.3 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain <br /> bacteria utilize the oxygen in the nitrate (NOO and release nitrogen gas (NO to the atmosphere. <br /> Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 <br /> percent. Soils with higher clay content,moist soil conditions, high pH, and organic material <br /> denitrify by about 35 percent and soils with high sand content and fast percolation rates are <br /> estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br /> A denitrification factor of 25 percent was used for the site which accounts for the dark colored, <br /> fine-grained surface soil. <br /> 50, <br /> Z <br /> O � <br /> 4 P <br /> SS-�% <br />