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C. PERCOLATION TEST RESULTS SSS 6 To assess the permeability of the �5ans posed filter bed area adequatel four ercolation tes ompleted at varying depths in to ' in the filter bed depicted in t e Site Plan found in ppen x e test depths were 24 Sand 60 Xnches below existing grade, giving a coin etailed observation of subsurface permeability within the future filter bed. These depths represent the following: Between 24 and 36 inches below grade is approximately where the soil-effluent interface will be situated. The 42-inch depth represents typical leachline depth. Although leachlines are not specified design criteria for this project, measured permeability at this depth is useful information. This permeability information also applies to the 60-inch depth where a higher clay content, and much stiffer clay soil was encountered, which influenced percolation and therefore, permeability. SS6.3 September 30, 2005, the 60 inch boring and the exploratory borings referenced above wer ed with atruck-mounted drill rig. The 24, 36 and 42 inch perc test borings were drilled with a hand auger. The sidewalls of each boring were scored with a pry-bar and the loose material removed. This is a critical procedure in clay soils whereby the soils that line the boring may become"smeared" during the drilling process. By scoring the sidewalls, this`opens"these potentially smeared surfaces. On October 12, 2005, two inches of fine gravel was placed at the bottom and three-inch perforated PVC pipe was inserted in each boring. The test boring was pre-saturated with 12 inches of water, at 0900 hrs, a oximately 24 hours before the start of testing. r SSS 6. On October 13, 2005, percolation testing commenced for all four test borings. No stan ' g water was observed after the 24-hour soak period. Consequently, EHD Perc Test Procedure#2 was conducted in which testing was done over a four-hour period to induce maximum soil saturation. Test results reveal comparatively favorable permeability for the 24, 36 and 42 inch test borings considering the clay content, but a failing rate for the 60 inch deep test boring. A summary of the perc test results with corresponding application rate in gallons of effluent accepted per square foot,per day are found below. TABLE 2 PERCOLATION TEST RESULTS WITH CORRESPONDING APPLICATION RATES (gallons/ft'/day) 24 INCH DEEP PERC TEST BORING 31.3 min/inch / 0.553 gallons/ft2/day PERCOLATION RATE/APPLICATION RATE 36 INCH DEEP PERC TEST BORING ( 19.2 min/inch / 0.671 gallons/ft=/day PERCOLATION RATE/APPLICATION RATE - - 42 INCH DEEP PERC TEST BORING 17.9 min/inch / 0.686 gallons/ft2/day PERCOLATION RATE/APPLICATION RATE 60 INCH DEEP PERC TEST BORING 83.3 pnin/inch / 0.235 gallons/ft/day PERCOLATION RATE/APPLICATION RATE Application Rates adapted from California State Water Resources Control Board Guidelines far the Design al-Sewage System 5 J) Chesney Consulting