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77-626 <br />Robert Ii. Mason, Inc. -3- February 6, 1978 <br />Percolation <br />Test No. <br />Surface Soil At <br />Elevation* Test Depth <br />Absorptivity <br />Rate (mpi) <br />2S <br />102.6 <br />CL-Sandy Clay <br />**** <br />26 <br />101.0 <br />CL-Sandy Clay <br />**** <br />27 <br />9S.2 <br />SC -Clayey Sand <br />60 <br />28 <br />92.2 <br />SC -Clayey Sand <br />60 <br />29 <br />92.0 <br />SC -Clayey Sand <br />S4 <br />30 <br />92.2 <br />CL-Sandy Llay <br />480 <br />*Surface elevations were inferred from those elevations <br />which appeared on the January 19th Boundry Survey. <br />**No drop in water level observed. <br />***Percolation test readings not conducted when water and <br />ice were observed in test holes following 24-hour soaking <br />period. <br />****Percolation test holes were exploratory in nature and <br />were backfilled when sandy clay soil was encountered to <br />termination depth in the percolation test holes. <br />ANALYSIS: <br />As indicated above, S of the 30 percolation tests conducted <br />on the lot met the specified minimum standard required for a <br />drainfield system. The variability in percolation rates may <br />likely be attributed to 2 factors. There is, of course, the <br />normal variability in soil permeability inherent in all <br />natural glacial deposits. The more dense and/or cohesive <br />the sandy clay and clayey sand tills encountered at test <br />elevation, then the less permeable it will likely be. <br />It is likely that failing test rates have been caused by the <br />presence of ground frost and frozen soil conditions. Although <br />the observable frost depth in the percolation test areas <br />appeared to be approximately IV, temperature measurements <br />conducted during the second series of percolation tests <br />indicated that the soil temperature at the 36-inch depth was <br />340 F. If the water does not freeze when entering the soil, <br />it would be considerably more viscous, which would reduce <br />its passage through the soil pores <br />RECOMMENDATIONS: <br />We understand that a 3-bedroom house is to he constructed. <br />For a 3-bedroom house, the City ordinance requires 2 septic <br />tanks. Tile first must have a capacity of at least 1000 <br />gallons and the second at least 7S0 gallons. As may be <br />seen from the above tabulation, the initial tests (tests I <br />through 26, excluding P-18) averaged above the Gasumi <br />umun- <br />ENGINEERING TESTING <br />