1988-06-20_GENERAL DOCUMENTS - C1981017

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