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' Performa Inc. • • May 7,2003 Page 14 ' Three nitrate loading scenarios were performed using the stated variables except for Nw. The first scenario considers an Nw of 26 mg/L-N reflecting no pretreatment(Plate 4). The second scenario considers the use of a treatment system operating at an efficiency of 50% for total ' nitrogen reduction(Nw-- 13 mg/L-N) (Plate 5). The third nitrate loading scenario considers the use of a treatment system operating at an efficiency of 75% for total nitrogen reduction(Nw--6.5 mg/L-N). (Plate 6). Please refer to Table 6 for a summary of the results. Please note the variable ' Nc represents the average, long-term nitrate concentration of percolating water for the site from rain water and treated domestic waste water. Hantzsche and Finnemore (1992) indicate that the nitrate concentration of the aquifer may"build up" to the Nc level in the long term. Table 6. i i ' Summary of Nitrate Mass Balance Analysis. Scenario Result Acres Average Effluent Leachfield Deep (Nc)• (A) Daily now Concen- Denitrifi- Percolation of ' (Q) tration cation(d) Rainfall(R) (Table 4) (Nw) (Plate 3) Standard Septic 13.1 mg/L-N 14 7,083 gpd 26 mg/L-N 10% 5.01 in System(Plate 4) Treatment System 7.5 mg/L-N 14 7,083 gpd 13 mg/L-N 5% 5.01 in (50%removal of Total Nitrogen)(Plate 5) ** Treatment System 4.0 mg/L-N 14 7,083 gpd 6.5 mg/L-N 5% 5.01 in (75%removal of Total Nitrogen) late 6 ** * Maximum contaminate level(MCL)for Nitrate in drinking water is 10 mg/LN. ' ** Please note that 50%removal of nitrogen(26 mg/L-N x 50%= 13 mg/L-N)is typical however nitrogen removal may be up to 75+%if conditions are optimal according to OSI. 7.0 DISCUSSION AND RECOMMENDATIONS The soil suitability and nitrate loading study has determined that the site has "ranid" percolation rate to a depth of 13 feet followed by less rapid soils to the maximum depth of exploration of 25 eel. Ground water was measured at a depth of 20 feet 4 inches on March 24, 2003 and 20 feet on May 1,2003. A water sample from the shallow aquifer within the boring was tested for DBCP and nitrates on March 24, 2003 and general minerals and total nitrogen on May 1, 2003. ' The water samples indicated that nitrate was found in widely different concentrations between this time period. OE 4501 p't�A