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C. PERTEST RESULTS 1 SSSS 6 To assess the permeability of the proposed filter bed area adequatelour ercolation tes pleted at varying depths in locations ine filter bed depicted in the Site Plan found in ppen ix he test depths were 24, 36,x' and 60 'nches below existing grade, giving a com t ailed observation of subsurface pe eability 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. SS 6.3 September 30, 2005,the 60 inch boring and the exploratory borings referenced above wer ed with a truck-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. SSS§�,76On October 13, 2005, percolation testing commenced for all four test borings. No standing 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 'n/inch / 0.553 gallons/ftz/day PERCOLATION RATE/APPLICATION RATE 36 INCH DEEP PERC TEST BORING _19.2 inch / 0.671 gallons/f/day PERCOLATION RATE/APPLICATION RATE 42 INCH DEEP PERC TEST BORING 017.9 min/inch / 0.686 gallons/ft/day PERCOLATION RATE/APPLICATION RATE 60 INCH DEEP PERC TEST BORING 83.3 RiWinch / 0.235 gallons/ft/day PERCOLATION RATE/APPLICATION RATE Application Rates adapted from California State Water Resources Control Board Guidelines for the Design of Sewage Systems. Chesney Consulting