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fFRNw= 65 mg N/L <br /> = A denitrification factor of 75%will be used given the substantial 99%decrease in NO3-N concentrations from <br /> the 10 ft to 25 ft depths. <br /> = 8.82" <br /> Nb= Assumed to be 0.1 ppm NO3-N <br /> 0.89 in/yr x(65 mg N/L) 0 -0.75)+(8.82 in/yr x 0.1 mom) <br /> Nr = (0.89 in/yr+ 8.82 in/yr) <br /> Nr = 1.6 ppm as nitrate-nitrogen(NO3-N); 7.1 ppm as nitrate. <br /> IV. O.W.T.S. OPERATIONAL PARAMETERS AND COMPONENTS <br /> A. PROPOSED SYSTEM OPERATION <br /> The wastewater generated from the Phase I and Phase 11 build-out of this project will be initially <br /> processed by two, 1,500 gallon, traffic-rated septic tanks. These tanks are to be installed at the south <br /> end of the proposed Office Building and Shop Building, as illustrated in Site Schematic in Appendix <br /> H. The two tanks are to be traffic-rated since there is a possibility of vehicular traffic at the south <br /> end of these buildings. Due to elevational differences, effluent from the east tank will be pumped <br /> into the front compartment of the second or west tank, which accepts waste from the offices. It is <br /> imperative that the influent line from the Office Restrooms be installed as high in elevation as <br /> possible. Effluent from the west tank gravity flows to a D-Box at the south end of the primary filter <br /> bed, then gravity flows into two perforated laterals. Two, 36" dia. seepage pits are to be installed <br /> directly north of the filter bed. <br /> B. SEPTIC TANK <br /> Septic tanks store accumulated sludge, scum and effluent(clear zone) volumes, which in turn <br /> affect treatment of nitrogen within the tanks. The following equation is used to determine <br /> Detention Time based on the second (west)tank that will accept all the wastes: <br /> Detention Time= 1,500 gal tank capacity x 0.70(30%volume lost to sludge/scum accumulation)=5.6 day <br /> 1.5 (Peaking Factor)x 392 gpd(ADF) <br /> Detention Time= 1.8 days. The minimum acceptable detention time is 1.0 day. Therefore,the proposed <br /> second 1,500 gallon septic tank that will accept all the wastes will be sufficient volume. <br /> C. FILTER BED SIZING CALCULATIONS <br /> The total number of on-site people, which will include employees, customers, visitors, etc. is <br /> quantified in the CDD Administrative Use Permit (Appendix B). Sizing criteria is based on EHD <br /> document 42-01-004 which itemizes a Water Use Computation Factor for Commercial <br /> Establishments. <br /> Page -6- <br /> Chesney Engineering, Inc. <br />