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'November,19,.1999 Job Number. 599303: - Page$' - `. ._ The results,of the analysis indicates that viewing the septic and.rain loads•for-the 1:75 acre site for an-average'year,the.combined rain water and treated,septic effluent concentration of . nitrates is estimated to be 8.94 mg/1-N, about 89% of the maximum contaminate level for the, ' drinking water standard of 10 mg/1- N. VIII. : CONCLUSIONS AND RECOMMENDATIONS' In.conclusion, analysis of the percolation test m . cates-the onsite soils percolate 26 min/in' at a depth .of 2 feet. The interviews with local neighbors indicated that both'leach field and leach . field with seepage pits exist-near'the site. The 40 foot exploratory boring encountered no shallow groundwater'and the depth to groundwater in the on-site well is about 42'feet. The estimated total average nitrate'concentration.of the septic field-percolate is estimated to be 8.94 niig/1-N,.about ' 890/0 of the maximum contaminate level for:the drinking water. . : 'Ina shallow.leach'field design, it is anticipated that the majority of the eMuent.will evaporate and/or be consumed by surface plants while any remainder may reach.one of many confining clay zones, the first of which was found at &depth of 22 feet. The drillers log of a aearby water well has shown that-the local-aquifer may-.contain.at.least nine layers of sand and clay to a total depth of 155'feet: -Since concentration of the percolate is estimated to be below the'drinking,water standard, that a good portion of the eluent may evaporate or be consumed by plants and the presence of the confining clay layers exist'in the area,-it is unlikely that the use of the septic s stem will p Y degrade water quality of the on-site well-or degrade.regional water-quality. To assure the best performance from the new-septic system, our recommendations for the.pioject are.as follows: 1) ' The leach lines should be placed no deeper then 42 inches,less is-preferable._The use of septic pits'should be avoided if possible. If they are required- more shallow. - pits.are preferable to fewer deep pits. 2) To:ensure maximum denitrification of the effluent, the leach hne.treriches should . be supplemented with an organic carbon source such as a organic silt.,organic c'-lay',- or lay,or ordinary gardening peat soil !Mpkin&47.An appropriate.amount.of peat soil supplement could be purchased from a gardening store, for example, and placed in - the leach line trenches to.form a biomat filter. Charcoal is not recommended for an organic carbon source.