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Mike Long - 4 - ~ May 18, 1988 <br />Lou Hamm and I debated his memo of last fall at some length. He completed a <br />reanalysis of the pile's stability. He used all of the assumptions made by <br />Ken Meyers, the original consultant, except for the phreatic surface <br />assumption. Lou revised that assumption to reflect the seep line issuing <br />approximately 10 feet above the first terrace bench. He considered this seep <br />line to be representative of the phreatic (saturated) surface within the hndy <br />of the pile. The three piezometers located nn the first terrace bench <br />determined the water table to stand approximately 20 feet below the surface of <br />the bench, approximately 30 feet below the seepage line. Therefore, Lou's <br />assumption, which greatly lowers the apparent slope stability safety factor of <br />the pile, is grossly conservative. In fact, the pile has developed several <br />perched water table surfaces. This could have resulted from excessive <br />compaction of long-term exposed surfaces, concentration of high-clay roof rock, <br />etc. These perched water table conditions could be modeled, but considerahl,y <br />more information would be required to define the configuration of the perched <br />layers and the material properties within them. Collection of this data could <br />be an expensive undertaking. Lou agreed with all of these observations. <br />After our discussion with you on Friday, May 13th, Bnh and I presented the <br />following proposed resolution of the Powderhorn situation to Bernie, Lou and <br />Don on Monday, May 16th. The Division will perform a review of the <br />outstanding Roadside/Cameo mining permit, in accordance with Rule 2.08.3. The <br />Division's review will observe that the hydrologic conditions at the waste <br />pile appear to have deviated from the assumptions made in completing the <br />original stability analysis for that waste pile. The Division will require <br />the operator to demonstrate that the original design for the waste pile <br />remains in compliance with our regulations. Further, our finding will order <br />the operator to refrain from depositing additional waste nn the structure, <br />until that demonstration has been completed to the Division's satisfaction. <br />The finding will also observe that the Division is concerned that the existing <br />drainage system installed at the pile may not be in compliance with the <br />regulatory requirements and the Division will require the operator to <br />demonstrate its compliance with our appropriate regulations. Our finding will <br />also clarify that the permanent reclaimed configuration of the waste pile <br />varies from the operational configuration and will he in compliance with Rule <br />4.10. It will also state that if the operator were to propose final <br />reclamation of the waste pile in any configuration other than the approved <br />final configuration, the operator would have to submit and obtain approval of <br />an appropriate revision. <br />Lou Hamm and Dnn Frickle stated that they believe this would satisfy their <br />technical concerns. Bernie Freeman was less receptive, stating that he would <br />have to confer with his superiors. He did ask whether the bottom two benches <br />would be regraded as a result of this resolution, I responded "No," and <br />restated the history presented above, I observed that the Division considered <br />this issue to be an enforcement issue and that we would maintain compliance <br />through appropriate inspection and enforcement activity. <br />