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Mr.Sandi De Jong <br /> September 25,2003 <br /> Page 13 <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 (CMS). Lodi is located within evapotranspiration zone number 12. The <br /> 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 Lodi area is estimated to be <br /> 6.84 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N whose maximum <br /> 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(NO3) and release nitrogen gas(N) 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 30 percent was used for the site which accounts for the slow <br /> percolation rate of the shallow cemented soil zone. In addition, utilizing a 4,000 gallon septic <br /> tank capacity(two 2,000 gallon tanks)would promote additional denitrification of the effluent. <br /> 7.4 Nitrate Loading Scenarios <br /> One nitrate loading scenario was performed to determine the impact from the proposed facility. <br /> The following table presents a summary of the nitrate loading results and variables used. <br /> pE RSQy <br /> WW Q ti <br /> �ssoc� <br />