2014-10-10_PERMIT FILE - C1996083A (24)

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Flooded mine workings could also impact the water quality in the area. When the mines are sealed they will slowly fill with water. Although no data for permeability or transmissivity of the saturated portions of the coal bearing member of the Mesaverde Formation are available within the permit area, the experience by others (Brooks, 1983) suggests the Mesaverde Formation transmits little water. Therefore, the abandoned mine workings would not be expected to transmit water to the surrounding strata. Based on the above discussion, if the mine workings fill with water and discharge through the portals, the impact on the North Fork of the Gunnison River would be less than or equal to the mine water discharge analysis presented above. The flooded mine workings could also affect the ground water quality and quantity in the overlying Upper and Lower Perched Water Zones. However, as stated above, the Mesaverde Formation transmits little water. Therefore, the impact the flooded mine workings will have on the quantity and quality of the surrounding strata should be minor. The Rollins sandstone, as monitored in DH -34B, NM4X98 -29 and P- TC -03- 01(R) has pH in the range of 7.5 to 9.6, conductivity in the 1,200 to 7,900 umhos /cm range and total recoverable iron in the 0.2 to 62.0 mg /I range. The Rollins sandstone is a confined aquifer under piezometric head. The confining shale layers above the Rollins sandstone and piezometric head should prevent any integration of water from either the D -Seam or B -Seam into the Rollins sandstone. There are two drill holes (G -15) located near the mouth of Dove Gulch and DH 98 -57 located in the central portion of the east mine workings that provide documentation of the hydraulic isolation of the Rollins sandstone from the B -1 Seam, the lowest coal seam to be mined. The following table shows the extent of the hydraulic isolation. Hole (Interburden) Mudstone Sandy Mudstone Sandstone Coal Lost Core G -15 (89.8) 64.3 8.3 11.0 6.2 0.0 DH 98 -57 (94.9) 68.0 10.6 9.0 0.0 7.3 In the western mine plan area, west of Terror Creek, drill holeTC- 03 -03, CWI- DH-50, 51 and 62 document the hydraulic isolation between the Rollins sandstone and the lowest coal seam to be mined. DH- CWI -51, SS -2 and SS- 9 are located in the northern portion of the western mining district. The following table shows the extent of the hydraulic isolation. PR -14 2.05-122 09/14