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August 8, 1983 <br /> Project 116-4.1 <br /> - 6 - <br /> Regarding Section B Liner <br /> The permeability test is conducted in accordance with the U.S. Army <br /> Corps of Engineers procedure submitted in the Appendix of our <br /> original proposal. As conducted in the Terratech lab, it utilizies <br /> the procedure outlined under No. 6 Permeability Test With Pressure <br /> Chamber. The procedure outlined in No. 7 Permeability Test With Back <br /> Pressure, is utilized to insure that the sample is completely <br /> saturated. The permeability test with back pressure is performed <br /> utilizing equipment that permits increasing the chamber pressure and <br /> pore pressure simultaneously maintaining their difference constant. <br /> When testing with leachate an estimated 3 pore volumes of leachate is <br /> passed through the sample to further ensure total saturation and <br /> exposure to the leachate being used. Three separate readings are <br /> obtained and averaged to reach the permeability value reported. <br /> These 3 data points when obtained are not accepted if they have a <br /> total variance in excess of 10$. We use a total fluid pressure of <br /> 100 psi and a confining pressure on the sample of 95 psi. The sample <br /> is brought to this pressure in small increments with the 5 psi <br /> difference being maintained at every step increase up to the total <br /> pressure applied. <br /> Paragraph #4 <br /> We have reviewed the concern regarding potential blowout of the <br /> liners due to water pressure with special concern to the side wall <br /> liners. <br /> In all the drilling and excavation conducted on the Forward Inc. <br /> disposal site since 1971 there has never been perched groundwater <br /> conditions encountered above 50 feet below existing ground surface. <br /> Excavations, bore holes, backhoe pits, and trenches have always been <br /> dry throughout the entire disposal interval of the trenches in the <br /> group 1 disposal area. In order for liner blowout to occur, the soil <br /> conditions behind the liner require saturation and substantial pore <br /> water pressure development. Since we have never encountered fluids <br /> in the interval, the potential for blowout of side wall liner is <br /> considered to be nonexistent. We have reviewed this with our soil <br /> engineers and have anticipated every conceivable situation which may <br /> occur at the site and the potential for blowout does not appear to be <br /> possible. <br /> GBetac Associates `j <br />