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Predicted Discharge of Mine Water into Bedrock Aquifer <br />The regional aquifers, Tow Creek and Trout Creek sandstones, will not be affected by the Apex <br />No. 2 Mine; the Tow Creek is a few hundred feet below the mine workings, and the T~entyrtti]e <br />is several hundred feet higher in the stratigraphic section. 7~.~r~ <br />?a <br />Only a sandstone bed in the basal Williams Fork aquifer could be affected by the Apex No. 2 <br />Mine. The basal Williams Fork aquifer was defined by Robson and Stewart (1990, USGS Water- <br />Resources Investigations Report 90-4020, page 54). Domestic wells yielding less than 10 gpm <br />have been developed in this aquifer near the Apex Mine, but no wells have been completed in the <br />specific sandstone bed that could potentially be affected by the Apex No. 2 Mine (see attached <br />annotated copy of Regional Geology and Cross Section from permit). <br />The sandstone bed potentially affected by Apex is approximately 40 feet thick and is about 90 <br />feet above the lower Pinnacle coals (see attached geophysical log and cross-section). The <br />sandstone bed probably is low porosity based on the absence of a density anomaly on the density <br />log. Drilling depth from the ground surface to this sandstone bed would be at least 450 feet at the <br />northeast end of the Apex No. 2's workings. At that location, the workings extend across a fault, <br />a few feet into the sandstone bed. The fault has juxataposed the sandstone bed against the <br />Pinnacle coal at that location. <br />Water that seeps into the workings can be expected to accumulate in the northeast end of the <br />workings at the fault. This is the lowest point in the workings. As the water accumulates there, <br />it would discharge into the sandstone, forming a plume that extends out into the sandstone bed. <br />The plume would most likely extend downdip (northwestward) from the discharge point. The <br />plume would probably be trapped against the downthrown (northeast) side of the fault by the <br />regional downdip flow of adjacent ground water in the sandstone bed. <br />The plume's impact on the aquifer would be of no concern more than about 1000 feet north of <br />the discharge point because a drilling depth of more than 600 feet would be uneconomic for what <br />would probably be a low yielding well. This depth limit and the expected lateral extent of the <br />plume (as shown on the attached map) indicate the plume would impact the aquifer in an <br />approximate 8-acre area in SW 1/4NW 1/4 Section 22- T4N-R86W (see attached lower Pinnacle <br />seam map). <br />Downdip from that location, water from the plume would flow downdip, generally northward, <br />through the swcturally low azea that extends generally northward between the Tow Creek <br />anticline (on the west) and the Twentymile Mile Pazk syncline (on the east) [see attached <br />Regional Ground Water Flow Map]. Along this flow path, ground water flow is probably slow <br />due to a narrow point in the flow path in Section 13-TSN-R87W. This slowing of ground water <br />flow would regulate the discharge of mine water into the sandstone at the Apex No. 2 Mine such <br />that the dischazge would be less than the inherent maximum transmitting capacity of the <br />sandstone. Without the slowing of ground water flow, the ground water flow velocity in the <br />sandstone could be expected to be on the order of one inch per day. With the slowing of ground <br />water flow, the velocity could reasonably be expected to be a small fraction of one inch per day. <br />Page 3 <br />