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could disrupt an impermeable membrane's integrity. In response to Division comments, included in earlier adequacy reviews, the applicant has amended the permit application revision to include the following commitment: "Grand Valley will initiate studies to determine the effects of settlement upon the impermeable liner. Data will be submitted to DMG one yeaz prior to construction of the refuse area indicating the magnitude of settlement and possible shear zone so that the foundation and membrane can be designed to eliminate the possibility of refuse leachate coming into contact with the ground water." The applicant proposes a placement of between one and two feet plus four inch processing waste immediately above the impermeable membrane. The purpose for the placement of this course waste material is to provide a "wick" underdrain to collect any effluent that tnight infiltrate the surface of the pile. In order to qualify for this use, the proposed wa_<~te material will have to be demonstrated to be durable. The waste could not be tested prior to its becoming available. In response to eazlier Division comments, the applicant has amended the permit application to include the following commitment: "When coazse refuse to be used to construct the permeable drain is first generated, testing will be conducted to indicate its durability. Results of these tests will be submitted to DMG upon receipt. If the requirements at DMG aze not met, an alternate source of durable material will be provided." (Page 2026A, Amended Permit Revision Application.) The applicant: assumes material strength values for the processing waste material in completing a stability analysis of the proposed pile's co~gutation. The assumed material strength values aze obtained from MESA and Bureau of Mines Reseazch Reports, and represent commonly referenced material values for coal processing waste. The applicant: commits, within the amended permit revision application revision, to testing the processing waste material when it becomes available, as follows: "When refuse is generated, analysis will provide accurate values of physical properties to be expected. Since these more accurate values will be obtained while the refuse azea is small and has no stability problems, designs can be evaluated to assess the appropriateness of parameters used in stability analysis. If significant changes to the design of the refuse area aze warranted, DMG will be notifi<:d." (Page 2-28, Amended Permit Revision Application) The Division.. however, must require submittal of these test results, in any case. The Division will judge whether amendment of the stability analysis and the plan are then warranted. For this reason, the Division finds it necessary to impose the following stipulation upon the revision's approval: at