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' , • <br />• <br />Memo to Berhan Keffelew -2- January 24 1996 <br />become saturated, and if the~Q was hydraulic connection between the <br />LVSCF and the overlying pregs~t solution storage matrix (through <br />flaws in the primary liner), then unacceptably high hydraulic head <br />would be applied to the composite liner system. The operator would <br />have to address dewatering of the LVSCF, both from a theoretical <br />perspective and based on empirical records from dewatering of the <br />Phase I LVSCF, before the Division could approve the proposed 2 foot <br />thick layer. <br />3. The operator has proposed an upper bound for the gradation of soil <br />liner fill as material passing a 2 inch sieve. As such, and in <br />accordance with testing that was required for the VLDPE used to <br />construct the Phase I Pad, the operator should conduct an additional <br />synthetic liner load test as follows: A test cell should be <br />prepared with an underlying granular material consisting of soil <br />liner fill with a 2 inch rock preferentially placed at the surface, <br />then a sample of both the 80-mil HDPE and 80-mil LLDPE should be <br />tested in the pressure cell with an overlying granular material <br />consisting of Drain Cover Fill. Other than the preferential <br />placement of the 2 inch rock, the test should be conducted, and <br />results reported in the same way as the tests that have already been <br />completed. <br />4. In the operator's presentation of the synthetic liner shear test <br />results for the Phase II Pad, it is implied that the use a pseudo- <br />static coefficient equal to .14g is inappropriate. Since the <br />pseudo-static coefficient required in the approved permit is .14g, <br />it is the Division's view that use of this coefficient is <br />appropriate, and will remain appropriate for this site unless the <br />operator can demonstrate, to the satisfaction of the Division, that <br />some lesser coefficient would be acceptable. <br />5. As to your request regarding an opinion on whether or not the <br />operator's proposal, in the form of a letter and attachments dated <br />January 9, 1996, constitutes a change in the approved design: It is <br />my opinion that modification of the approved thicknesses of the <br />Drain Cover Fill and LVSCF from 3 feet to 2 feet constitute a design <br />change. The other components of the operator's proposal constitute <br />assessment and substitution of alternate earthen and synthetic <br />materials based primarily on availability. The substituted <br />materials would perform the same essential functions for the Phase <br />II Pad that are in the existing permit, hence these substitutions do <br />not constitute a design change. <br />cc: Jim Dillie <br />Jim Pendleton <br />C:1WPS11CRESSON.p <br />