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HANTZSCHEIFINNEMORE EQUATION CONSIDERING THE EQUATION IN TERMS OF "INDIVIDUAL RESIDENTIAL SOURCE PER ACRE" AWx Nw(I -d) +R Nr= (AW+R) Where: Nr= Resultant average concentration of nitrate-nitrogen in recharge water from domestic sources A =Number of dwelling units per acre on septic tanks (unit/acre) = 1.15 ac. (average Lot land area) W =Annual wastewater loading per dwelling unit per acre= 3.2 in. (in inches,based on 270 gpd/residence) Nw=Total nitrogen concentration of wastewater in N mg/L(66 mg N/L/day- See Pg. 9) d = Fraction(%)of nitrate-nitrogen loss due to denitrification in the soil and biomat formation-assumed to be 25%min. r = Annual deep percolation of precipitation = 15.5 inches Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences (ppm NO,-N). Assumed to be 0.1 mg/L Values and Assumptions: W =270 gpd/residence x 365 d/yr=98,550 gals/res./yr _ 1.15 ac x 27,154 gals/ac-in=3.2 in./res./yr Nw = 66 mg/L - 10%reduction of N in the septic tank=59 mg/L N d = 10% from biomat formation and 25% from clay soil under leachlines and observed nitrogen decrease. 1.15 ac(3.2 me N/L) (59 me/L) (1 -0.35)+ (15.5 in/yr) (0.1 mg/) Nr = (1.15) (3.2) + 15.5 in Nr = 7.4 ppm as NO3 N or 33.1 ppm as NO, IV. CONCLUSIONS AND RECOMMENDATIONS SSS§ 6.7, 6.8 The percolation test results for this project reveal dramatically varying surface and subsurface soil conditions. In accordance with EHD rules and regulations, the septic system disposal area for each individual Lot must be installed within 100 feet of the percolation test location. These perc test locations were in most cases exclusively dependent upon locating permeable stratum within a particular Lot. This was particularly evident with Lot 4. Five - 25 ft deep borings were completed on this Lot in an attempt to find permeable soil. As evidenced, only the surface soils in the"front'of the Lot were determined to possess acceptable permeability. Consequently, the septic system for this Lot may have a very limited lifespan. Limited lifespans may also apply to other Lots as well, with the possibility being that permeability(acceptable percolation)was serendipitously determined in localized areas, which are not representative of a portion of the subject Lot(front or back), or the Lot as a whole. Page -11- Chesney Consulting