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rrIV. CONCLUSIONS AND RECOMMENDATIONS SS §5.4. The surface soils underlying the proposed filter bed disposal area to approximately five feet in dcon sts of a comparatively high clay content soil with a surprising degree of permeability, as e7d by the percolation test results. From the backhoe test pits, a clayey gravelly/cobble soil was encountered at eight feet in depth. The soil chemistry test results reveal that denitrification and nitrate mobility has apparently occurred in lowering the nitrate-nitrogen concentrations within the soil profile. It is theorized that the soil environment may be anaerobic during the winter months with the high moisture content creating anaerobic conditions conducive for promoting denitrification,thus reducing nitrate-nitrogen concentrations. NLS 4.2,sSS 6.7 The designed Chambered filter bed will be installed high in elevation to take advantage of the ' genu y soils (29%clay content-on average)that possess favorable qualities to inhibit nitrification. For nitrification that does occur,the anaerobic microsites at deeper elevations within the clay soils possess a theoretically high potential for denitrification, as discussed above. This denitrification potential in combination with landscape plants/grasses in the filter bed area should also reduce nitrate impact by evapotranspiring a percentage (albeit small and indeterminable)of the effluent through the louvers during favorable weather times of the year(i.e.,April through September). SSS§6.76. . The actual infiltrative surface(IS)under each Infiltrator Chamber is 4.00 ft x 2.83 ft= 11.32 ft'-. 11.32x 250 Standard Infiltrator Chambers=2,830 ft . If the Average Daily Flow is taken to be 1,775 gals/day,the Application Rate= 1,775 gpd—2,830 ft'=0.627 gals/ft'/day. The average Application Rate determined from all four test depths indicates a rate of 0.727 gals/ft2/day, and an average Application Rate at the anticipated soil-effluent interface of 24 inches below existing grade was found to be 0.544 gals/ft'/day(See Page 7). Therefore, considering infiltration and percolation of effluent into the soil,the test results reveal acceptable infiltrative and percolative capacity which corresponds with the calculated ADF of 1,775 gpd. In addition, if each pump of the duplex system pumps approximately 240 gallons/dose(See Page 14),this volume of effluent is equivalent to applying: 2,830 ft' x(1 acre/43,560 ft')=0.0650 acres 0.0650 acres x 27,154 gallons/ac-in= 1,765 gallons/in of effluent under the Chambers. 240 gals/dose= 1,765 gals/inch=0.136 inches of effluent distributed under the Chambers per dose. Nl §4 1 The nitrate loading potential ca ulated on Pa /'cates the percolating effluent will the retica�lly have a resultant nitrate-n' gen c centratio 17.7 m,which is below the drinking water MaxnYium Contaminant Level (MCL)of 10 m . These alculati ns rely on numerous factors which are extremely variable and unknown at thN time.Ae influencin ctors, and the effluent quality itself can only by quantified after several months o se of the facility by taking an actual effluent sample for analysis. From the Filter Bed calculations, a 2,876 sq. ft. filter bed area was required. However,area exists for a 3,330 sq. ft filter bed area which"evens"the number and layout of the Chambers specified. This increase in disposal area adds an additional four feet of area at 33 ft wide,and an additional 10 Quick 4T"' Standard Infiltrator Chambers. NLS§. It is theorized that abundant upgradient nitrogen fertilizer applications have occurred over the past decades, that coupled with large amounts of irrigation water,have created conditions that"flushed"the nitrate through the upper soil profile and into the underlying gavel strata. Page -15- Chesney Consulting