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Traylor Shea Precast Page 11 of 14 Our Project Number: E071WB i November 29, 2007 v For Phase I of the project, the total daily waste water quantity is 371 gallons per day (gpd). The flow rates selected for the uses associated with Phase II of this project are presented next. Table 7. Typical Quantity of Effluent Phase U). Category Total People Average Quantity per Average Daily Flow per Parcel per Day Person Employees 46 13 gal/day/employee (46 employees * 13 gpd * 7) 427 gpd Note: gpd is gallons per day. _ For Phase II of the project, the total daily waste water quantity is 427 gallons per day. The average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. It is estimated that the average concentration for total nitrogen in waste water for the project is approximately 85 mg/L-N over the long term. I1.3.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (NZ) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 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 and fast percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. A typical denitrification factor of 25 percent was selected for the Site because of the fine grained nature of the soils. II.3.5 Nitrate Loading Scenario A nitrate loading scenario was performed to determine the impact from the proposed project. The scenario utilizes the variables discussed previously which represent the estimated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculations for the site, as presented in Plates 10 and 11. Table 8. S frimary of Nitrate Mass Balance Equation. Result Average Effluent Leachfield Deep Phase of Concentration Percolation (Nc)* Acres(A) Daily Flow Denitrification Project (mg/1-N) (Q)(gpd) (Nw) (d) of Rainfall (m9/�-N) (R)(in) ('i 5 Phase I 7.9 8.58 371 85 25% 4.67 Phase II 8.9 8.58 427 85 25% 1 4.67 * Maximum contaminant level (MCL)for nitrate in drinking water is 10 mg/L-N. V 902 Industrial Way•Lodi,CA 95240•209.367.3701 •Fax 209.369.4228 ©2007 Neil O.Anderson&Associates,Inc