2015-08-18_PERMIT FILE - C1982056A (4)

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2.04.7 Hydrology Description (1) Ground Water Information (a) The application shall contain a description of the ground water hydrology for the proposed permit and adjacent area, including, at a minimum: (i) The depth below the surface and the horizontal extent of the potentiometric surface of each aquifer above, within and, if potentially impacted, below the lowest coal seam to be mined; (ii) The lithology and thickness of the aquifers; (iii) The seasonal quantity and quality of the water within each aquifer; (iv) Ownership, uses and location information for all existing wells, springs and other developed water resources; and (v) The quality of the subsurface water. Water quality sampling and laboratory analyses will be conducted in accordance with 2.03.3(4) and shall include: (A) Total dissolved solids or specific conductance corrected to 25 C; (B) pH; (C) Total iron; and (D) Total manganese. RESPONSE The responses presented below reflect the information presented in the original application and subsequent submittals for the Southwest Mining District, Eastern Mining District, Northern Mining District, Western Mining District, and Wolf Creek Reserve. The information for the subsequent submittals is contained under the title for that district. It should be noted that the ground water basin in which the mine is located is the same for all of the districts; therefore, the discussions presented in the original application are pertinent to the expanded areas. The discussions have been updated to reflect the passage of time since the original application was submitted. The Foidel Creek Mine is located at the southern end of the Eckman Park sub -basin on the southwest flank of the locally significant Twentymile Park structure of the Twentymile Park Basins results in the enclosed ground water basin which is rimmed by outcrops of the major lithologic units described in Section 2.04.6, Geology Description. The limits of the potential mining - related impacts on the ground water system are shown on Map 4, Proposed Hydrologic Area Boundaries. Ground water in the Twentymile Park Basin exists primarily under confined conditions within the bedrock units and under unconfined conditions within the alluvial materials underlying the major surface drainages of the area and backfilled areas of adjacent surface mined areas. Ground water occurrence and movement within the bedrock aquifer system is controlled by geologic structure and lithology, and to a limited extent, by mine - related disturbance. Recharge to the major aquifer units occurs in the area of outcrop primarily in the southern and western margins of the Twentymile Park Basin, where unconfined conditions may exist locally. Ground water movement tends to follow the structural dip of the lithologic units toward the basin axis. This results in confined aquifer conditions down - gradient from the outcrop area due to the presence of relatively low permeability shale and interbedded siltstone /shale units within the lithologic sequence. Significant artesian pressures in the central part of the basin also exist as a result of the structural control of ground water movement. The major bedrock aquifer units with the Twentymile Park Basin are the regionally extensive Twentymile and Trout Creek sandstones. The Wadge Overburden and Wadge /Wolf Creek Interburden sequences contain ground water, but are not utilized as a water supply except by TC for dust - control. As described in following sections, the Wadge and Wolf Creek coal seams do not function as aquifers in the Twentymile Park Basin. The relative position of these units within the stratigraphic sequence is shown in Figure 2, General Stratigraphic Column. Twentymile Sandstone The Twentymile Sandstone aquifer is laterally continuous over most of the area and is effectively confined above and below by low permeability shale and interbedded siltstone /shale units. The unit is a massive, white, well- cemented, TR13 -83 2.04 -19 11/03/14