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July 5,2005 NOA Project Number: E05027A Table 1. Typical Quantity of Effluent for Property. Category Total People per Average Quantity per Average Daily Flow Day Person Per Parcel Residence5 70 gal/day/resident 5 residents* 70 gpd/resident =350 gpd r Note —Gpd is gallons per day. For the site, the estimated total daily waste water quantity is 350 gallons per day. V The average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/L-N (Crites and Tchobanoglous, 1998). For the purposes of the nitrate to g estimate, the long-term average concentration for total nitrogen in waste water is estimated t e 45 mg/UN. 4.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NOS and release nitrogen gas (No 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 denitrification factor of 35 percent was selected for the Site due to the slowly percolating and fine •' grained soils. V 4.5 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 L uses associated with this project. The following table presents a summary of the nitrate loading calculation for the site and the maximum waste water allowable for the site based on the assumptions of deep percolation of rain, denitrification and nitrate concentration of the effluent. III VW I. 5 L "*44