2014-11-17_PERMIT FILE - C1982056 (2)

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Wolf Creek Reserve Groundwater Investigation Work Plan March 6, 2014 Being relatively distant from the outcrop area which receive recharge, little groundwater would be expected in the interburden rocks in the proposed mining area for the Wolf Creek Reserve. Similar conditions (little to no ground water encountered) have been observed in the additional surface drill holes completed to date. PROPOSED HYDROLOGIC INVESTIGATION WORK PLAN Additional investigation of groundwater conditions in the vicinity of the Wolf Creek Reserve is proposed. The purpose if the investigation is to meet regulatory the requirement for determining existing groundwater hydrologic conditions relative to the Wolf Creek Reserve and to provide sufficient information to allow prediction of Probable Hydrologic Consequences (PHC) associated with mining of the Wolf Creek Reserve. Significant information is already available from historic monitoring activities within the Permit Area. That information includes water level, flow rate and water quality data from the groundwater and surface water monitoring programs, and mine inflow data from detailed inventories of locations, rates and sources of groundwater inflow to the mine. That information will be used as a framework to guide the hydrologic investigation and evaluation related to the proposed Wolf Creek Reserve. The new information proposed to be obtained will add to the existing knowledge -base. Because of the extensive historical database related to the existing Wadge seam operations and the strong parallels or equivalency between the existing operations and the proposed Wolf Creek Reserve operations, the conditions encountered during mining of the Wolf Creek Reserve and the resulting hydrologic effects are expected to be strongly similar to those related to the Wadge operations. The possible exception is that less groundwater is likely to be encountered during mining of the Wolf Creek Reserve, given the existence of the Wadge workings throughout the area overlying proposed mining of the Wolf Creek Reserve and the lengthy history of dewatering associated with the Wadge seam operations. As noted, both previous studies (Robson and Stewart 1990) and more recent radio - isotope analysis of ground water indicate that the lower members of the Williams Fork Formation (including the Wadge and Wolf Creek Coal Seams and Wadge/Wolf Creek Interburden) function as a single hydrologic unit in this area and the fine - grained lithology limits downward ground water movement. With the additional evidence from exploration drilling showing that the interburden and coal units should contain little or no groundwater, requirements for additional hydrologic characterization for the Wolf Creek Reserve should be limited. TC proposes to install two new monitoring wells, one up- gradient and one down - gradient, in the Wolf Creek Interburden /Coal unit, monitor water levels, perform hydrogeologic testing to determine hydraulic properties, and obtain groundwater samples for water quality analyses. Monitoring of water levels and sampling for water quality analysis will be performed twice (semi - annually) to establish baseline. Bi- annual mine inflow monitoring and sampling for the Wolf Creek development and mine workings will supplement the results from this baseline monitoring program. Details of the proposed investigation are provided below. Well Installation TC proposes to install the two new monitoring wells in drill holes WC008A and WC013A, located as shown on Figure 3 and screened in the interburden /coal unit. The wells will be constructed with 4 -inch inside diameter steel casing and screen. Centralizers will be placed at the top of the screen and approximately 20 feet below the land surface. The screened interval will be from the base of the Wolf Creek Coal Seam to approximately 40 feet above the Seam. Filter pack material sized appropriately for the screen slot size will be placed around the well screen and extend approximately 10 feet above the top of the screen. A seal formed with coated bentonite pellets and approximately 10 feet in length will TETRA TECH