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The following reductions in the nitrate-nitrogen loading from above are anticipated, according to the scientific literature: Septic tanks (3-2000 gallons as designed) removes 50%N x 159 lbs= 80 lbs Biomat formation removes 10%x 80 lbs= 72 lbs Denitrification in clay soil strata removes 25%x 72 lbs = 54 lbs TOTAL ESTIMATED NITROGEN LOAD = 54 lbs N/yr. Quantification of the theoretical nitrogen contribution to the groundwater under the leachfield serving the Temple, correlated with the analytical test results is calculated as follows: Dilution water available (avg water use), QAVE= 2,500 gal/Sunday = 1,350 L/day avg groundwater flow(Q,,) = Groundwater flow perpendicular to 100 linear ft of leachfield area =k(hydraulic conductivity of sat. zone)x(i) x 2.5 ft (top mixing layer)X 100 ft= Q,,,,,,= [2 X 10-3 ft/min (estimated) x (60 min/hr x 24 hrs/day)] 0.01 (% grade)x 2.5 ft (mixing layer) x 100 ft= 7.2 ft3/day or 54 gals/day (205 L/day) CALCULATED NITROGEN CONCENTRATION TO GROUNDWATER UNDER THE CURRENT LEACHFIELD SERVING THE TEMPLE=49 kg N/yr= 134 grams N/day 134 grams N/day- (QAvE+ Qg,N)= 134 g/(1,350 L/day +205 L/day)= 0.09 x 1000= 86 mg/L NO3-N -4.5 (conversion factor) = 19 ppm NO3/day. The analytical test results indicated an increase of. 61 ppm NO3 - 53 ppm NO3 = 8 ppm NO3/day IV. SEPTIC SYSTEM DESIGN 1 IMPACT MITIGATION From the data and information presented, it is evident that a mound system must be installed for this project to properly manage septic effluent. The San Joaquin County Environmental Health Department has stipulated the mound system design for this project adhere to parameters as promulgated in the County ordinances and the U.S.E.P.A. Design Manual for Onsite Wastewater Treatment and Disposal Systems. A mound system is a soil absorption system which is elevated above the natural grade and consists of a suitable fill material. The purpose of this type of design is to overcome limitations or restrictions encountered by conventional systems. The two primary restrictions with this project are the highly impermeable clay soil strata and the comparatively high water table. The mound system consists of the following: a suitable fill material, an absorption bed area, a distribution network, a cap and top soil. The effluent will be pumped from the last septic tank into the absorption area through a network of pipes placed in the upper portion of the aggregate material. Effluent passes through the aggregate and infiltrates the permeable fill material. Treatment occurs through the fill material and the effluent eventually flows into the native soil. The cap should be composed of a finer material such as a clay cover to shed rainfall and retain moisture for vegetative cover. 5 Vary Ag 7gsearch