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File No. CO-9021-S01 <br /> July 22, 1991 <br /> Summary of Percolation Tests <br /> One percolation test was performed on each parcel. The percolation tests were performed near <br /> the existing leach fields on each parcel. The approximate locations of the percolation tests are <br /> shown on the attached Tentative Map. <br /> The percolation tests were performed by drilling a 12-inch diameter hole to a depth of 36 <br /> inches at both locations. The sides of the holes were scored and loose soils were removed from <br /> the bottom of the hole by hand. The bottom of the holes were filled with a 2-inch layer of gravel <br /> and a perforated 4-inch diameter PVC pipe installed. The annular space between the pipe and <br /> hole sides was backfilled with gravel for some distance above the base of the hole to sturdy the <br /> PVC pipe. A minimum of 12-inches of water above the gravel base was added and allowed to soak <br /> for 24 hours. The percolation tests were then performed. <br /> The actual data sheets associated with each percolation test is included in Appendix A of this <br /> report. The percolation test results obtained are summarized below: <br /> Test Percolation Rates'(min/in) <br /> Hole Parcel Average Last Comments <br /> 1 1 2.9 3.3 Silt with sand and clay <br /> 2 2 33.7 60.0 Silt with sand and clay <br /> Average values are for the total test duration. Last values are the rates for the last timed <br /> interval (either 10 minutes or 30 minutes). <br /> The percolation test results used for design of septic leach fields are based on the "last" column <br /> tabulated above. The highest percolation rate allowed for leach line fields (without alternate <br /> septic system design by a registered engineer) is 60 min/in. Thus, both locations meet or <br /> exceed this requirement. The percolation test results thus explain and confirm the known <br /> satisfactory performance of both existing septic systems. <br /> Conclusions <br /> Based on a review of past records of septic system permits and the results of percolation tests, <br /> it is our opinion that the septic systems will continue to give good performance. Since the <br /> groundwater table exists at a depth greater than 80 feet at the site, the septic systems should <br /> not adversely affect the quality of groundwater in this area. <br /> 2 <br />