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V. SOIL SUITABILITY STUDY The results of this study indicate the subject site is acceptable for the proper operation of an on-site septic system. A Percolation test result of 1.7 min/in was obtained at the 42 inch depth (See Appendix). The perc test was conducted in accordance with U.S.E.P.A. Manual of Septic Tank Practice. A review of Application Permits on file at the San Joaquin County Environmental Health Department reveals no applications for repairs or additions in the one-half mile study area. The soil strata under the proposed leachfield consists of a medium poorly graded sand with silt (SP-SM). The soil profile consists of this material classification down to static groundwater depth of approximately 11 feet. Therefore, a five-foot minimum separation distance between the bottom _ of the leachfield trench and highest anticipated depth to groundwater should be maintained at the proposed leachfield location. The fine fraction of the soil (silts and clays) may promote clogging mat formation which may lead to leachline failure. However, the soil porosity should be sufficient to promote aerobic conditions for digestion of clogging mat bacteria, thus extending the life of the leachfield. A 100% replacement area has been incorporated into the leachfield design: SEPTIC TANK CAPACITY DESIGN FOR RESTROOM WASTEWATER FLOWS ONLY: Base tank Capacity (BTC) = 1,600 gals Average Daily Flow(ADF)= 10 employees (max)x 25 gals/person/day =250 gals/day 1,600 gal BTC +250 gal ADF = 1,850 gal CTC (Calculated Tank Capacity) 1,850 X .200 Soil Factor= 370 lineal feet of leachline, two feet wide X 2 (100% replacement) = 740 feet lineal feet of leachline or 8,000 square feet leachfield area. _ VI. NITRATE LOADING FROM MANURE, WASTEWATER AND SEPTIC CONTRIBUTIONS. The data which exists in the scientific literature concerning nitrogen impact from facultatively treated effluent applies to specific locations, loading rates and wastewater strength. The following information details the nitrogen fraction of wastewater: In a facultative wastewater pond, organic nitrogen is converted to ammonia and ammonium nitrogen by microbial action. If the pH of the pond water is alkaline, the equilibrium shifts to ammonia production. If the pH is acidic, _ ammonium is prevalent. The ammonium is nitrified to nitrite and then to nitrate. Facultative ponds are normally alkaline, thus maintaining nitrogen primarily in the ammonia form. As the effluent is sprinklered onto the available cropland, the majority of the ammonia will volatilize, leaving only the remaining organic fraction to nitrify. The nitrification of the organic fraction is difficult to quantify due to unknown wastewater treatment efficiency. It is proposed to calculate nitrate loading for solid manure waste, with the remaining percentage of nitrogen being supplied by the effluent. If effluent analysis indicates potential nitrate- nitrogen excess for crop requirement, manure will be transported off-site or other adjustments made to the nitrate-nitrogen loading. 7 Vaffey Ag Pssearck