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i January 16,2007 NOA Project Number: E07009A The following table reiterates the septic waste water uses associated with the site. The rates 1" presented from the references provide general guidance but do not always reflect a match in usage. 1 Careful examination,professional judgement, and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for the uses associated with this project are presented '^ next i Table 1. Typical Quantity of Effluent Fl Total People Average Quantity per Average Average Total Average M.- Category Daily Flow Daily Flow on per Day Person Daily Flaw per Facility Site Gas Station/ 6 employees 13 gal/day/employee 78 gpd Convenience 708 gpd 4 Store 1,125 customers L 56 galJda • ployee— --.630 gpd_.T M Commercial 10 employees 10 gal/day/employee 100 gpd 164 gpd Building 32 parking spaces 2 al/da /customer 64 gpd �} Note --gpd is gallons per day. For the subject property, the total daily waste water quantity is 872gpd. F 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. z 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 (N, 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 F 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 because of the fine grained nature of the soils. ` F 6 i .