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The calculated nitrate loading concentration in the recharge effluent from the Restrooms is calculated to be under the Maximum Contaminant Level limit for nitrate in drinking water. The variables used in the calculations above are conservative. For example, the use of 113 mg N/L,which was determined from actual septic tank effluent from three commercial facilities is a much higher nitrogen concentration than those concentrations published in the sources referenced in Table 4. Secondly, various researchers place the nitrogen reduction occurring in septic tanks at 10%to 20%. From the May 8, 2003 Symposium"Onsite Wastewater Treatment-Nitrogen Removal,"Dr. Stuart Oakley of Chico State University states that "approximately 20% of the total nitrogen generated is removed in the septic tank."As noted above, a conservative estimate of 10%was used for the proposed septic tank. C. SEPTIC SYSTEM OPERATIONAL PARAMETERS AND COMPONENTS s SSS§3.7.//Discussion of efficient operation, disposal field longevity, and environmental protection are ba$.ed upon the environmental parameters discussed below. An overview of the system operation is as follows for the Produce Stand Restrooms: Influent waste from the building will gravity through a four-inch ABS tightline(0.25 inch/1 ft) into the first compartment of a two-compartment 1,6W gal septic tank. The effluent will then gravity into the second compartment which must have an effluent filter as tho effluent gravity flows into the distribution, or"D-Box"to be evenly distributed between four K80 ft Fong leachlines. SEPTIC TANK Septic tanks store the accumulated sludge, scum and effluent(clear zone)volumes, which in turn affect treatment of nitrogen within the tanks. In the following calculation,the pump-out interval factor times the QAVE times the peaking factor(PF)correlate the pump-out time interval in years with the recommended tank capacity. The peaking factor value for this project is estimated to be 2.5. Septic Tank Capacity Based on Pump-out Interval of One Year: Recommended tank capacity for a potential pump-out interval of three years after complete build-out: 2.8(pump-out interval factor) (QAVE)x Peaking Factor(PF=2.5)=2.8 (144 gals/day)x 2.5 = 1,008 gals. Total septic tank capacity= 1,600 gallon tank. As calculated below, a 1,200 gallon tank would be insufficient: Detention Time: Detention Time= 1,200 gal total tank capacity x 0.70(30%volume lost to sludge/scum accumulation) 3.0 (Peaking factor)x 300 gals/day(ADF) Detention Time=0.9 days.The minimum acceptable detention time is 1.0 day. Therefore, a 1,600 gallon septic tank must be used: Detention Time= 1,600 gal total tank capacity x 0.70 (30%volume lost to sludge/scum accumulation) 3.0 (Peaking factor)x 300 gals/day(ADF) Detention Time= 1.2 days. 12 Chesney Consulting