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k In addition to the backhoe trench pump-in tests, one shallow perc test was conducted on Parcel 1 and Parcel 2. Due to the indigenous soil structure described above for the shallow soils, it was decided to conduct the perc tests at a high elevation of 24 inches below existing grade, instead of the typical 42 inches below grade. The tests were done at this depth to determine if percolation would occur with shallow leachlines. Due to the highly organic nature of the surface soils, it would be much more conducive for increasing the denitrification potential if the leachlines were installed high in elevation, than having the soil/effluent interface at 42 inches below grade. The perc test results reveal non-existent percolation at the 24-inch depth, which may be attributable to the high soil moisture content. In all likelihood, the tests would have also failed at the 42-inch depth, also due to high soil moisture content. Since the leachline trenches should be hydraulically protected, there will be a greater chance for effluent percolation at the shallow 24- inch depth. Due to the greater denitrification potential, it is recommended to install the leachline high in elevation, if possible and with concurrence from the Environmental Health Department. The water drop fort last hal�ur of the four-hour test period was 1.2 inches for Parcel 1 and 1.1 inches for Parce 2, w�ich trap is ales to a perc rate of 25 minutes/inch (min/in) and 27.3 j min/in, respectively. This can be considered a comparatively slow perc rate since X30 min/in is considered failure for seepage pit tests. The trench dimensions are illustrated on the FIELD PERC REPORTS, with the pump-in test calculations demonstrating an acceptance rate (AR) in gals/sq ft/day as follows: i ❑ Length of trench= 15.5 ft ❑ Width of trench= 2.5 ft ❑ Depth of trench= 12.5 ft ❑ Depth of water over the floor of trench z 4 ft ❑ Depth below bottom of trench at periphery of plume = 4 ft(estimated) ❑ Total water volume pumped into each pit =900 gals. Total water absorbed during test ;- 1550 gals C3Extent of water plume area: water surface = 2.5 ft x 6 ft plume area is estimated 4 be: 10.5 ft width x 14 ft length= 147 sq ft ❑ Acceptance Rate (AR) =total flow absorbed - (area)(time) ❑ AR= 150 gals� (147 sq ft)(4 hrs - 24 hrs/day) = 6.1 gals/sq ft/day This calculated acceptance rate for the seepage pits can be recognized as favorable conidering there are 196 square feet for a seepage pit with 20 feet of the tested soil type and 36 in&es in j diameter: 196 sq ft x 6.1 gals/sq ft/day = 1,196 gallons can be theoretically absorbed l y each j seepage pit, each day. i -0�- x u 3 Vafley Ag Research