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Tlbs - ation removes 10%X 11 lbs= 1.1 lbs Fon in silt soil strata removes 20%X 9.9 lbs =2 lbs bs=8 lbs N/yr total nitrogen load. 71 Determination of the theoretical nitrogen contribution to the groundwater: Assume 80%reduction in N (from above)= 39 grams N/day - 80%= 8 grams N oxidized to nitrate-nitrogen/day. Dilution water available (avg water use), QAyg= 100 gal/day+ avg groundwater flow(Qgw,) Groundwater flow perpendicular to 100 linear ft of leachfield area= k(hydraulic conductivity of sat. zone)x(i - % grade)x 2.5 ft (top mixing layer)X 100 ft= Qgw=2 X 10-' ft/min(estimated) x (60 min/hr x 24 hrs/day) 0.02 x 2.5 ft x 100 ft= 14 ft'/day or 108 gals/day (409 L/day) CALCULATED NITROGEN CONCENTRATION TO GROUNDWATER UNDER LEACMULD=8 grams/QAvE+Qg,,, = 8 g NO3-N/day (379 L/day+409 L/day)= 0.010 x 1000= 10mg/L NO3-N C. SEPTIC SYSTEM DESIGN/IMPACT MITIGATION The design of a future septic system for the facility is based upon the factors of operation, longevity, and environmental protection. Plumbing fixtures must consist of low volume fixtures as specified in the Uniform Plumbing Code (UPC). SEPTIC TANKS The design and performance of the septic tank for the project is dependent upon the effluent disposal surface area, discharge rate and exit velocity. These parameters affect the sludge and scum volumes, and therefore,the nitrogen capacity of the tanks. Tanks with a greater surface area and shallower depth are preferred for surge storage capacity. Waste inflow volume creates a smaller rise in water depth and a slower discharge rate and exit velocity. These surges of flow through the tank are dampened as surface area increases. By using the projected average daily flow volume of 100 gallons,the effective tank capacity is as follows: The pump-out interval should be 3 yrs. After three years, a determination can be made as to sludge and scum formation and wastewater flows to possibly extend this pump-out interval. Required septic tank capacity: 2.4(QAvE)x Peaking Factor(PF) =2.4(100)x 1.5 PF = minimum 360 gal tank capacity needed. Therefore, a tank capacity of 1,600 gallons is recommended. Future septic tank design considerations are discussed under Impact Mitigation. LEACHFIELDS LBaseTankapacity (BTC)+Average Daily Flow(ADF)x Soil Factor(SF)_ TC + 100 gal ADF x .200 SF = 340 lineal feet of leachline 5 Naffey Ag Research