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~ . <br />~. <br /> <br />• <br />• <br />Z.os.o6(3)C6x~~~ <br />Groundwater Monitoring Plan <br />Hayden Gulch Mlne <br />T~ ~~ <br />~„.v~e ~/ <br />w~ <br />T/~'- SS. <br />BACKGROUND <br />The baseline data presented in the Permit was compiled by VTN. The data <br />indicated two water zones including water within the coal zone to be mined <br />and a sandy zone below the coal zone to be mined. The sandy zone has been <br />referred to as the "Big White" sandstone during exploration activities <br />adjacent to and west of the H-G Mine. This sandstone is similar in <br />composition to the Twentymile Sandstone (an important aquifer of regional <br />eztent), however, it overlies the Twentymile Sandstone by about 100 feet. <br />The sediments between the "Big White" and the Twentymile are predominantly <br />shale, silty shale, and siltstone. Three coal seams are generally <br />persistent within the sequence. The lowest seam mined at H-G was Seam 5. <br />Below Seam 5 is a thick sequence of shale and shaley siltstone with two <br />thin coal seams. This uniform sequence of semi-impermeable sediments <br />forma a barrier to water migration between the coal zone that was mined <br />and the Big White Sandstone below. The water quality presented by VTN <br />indicated a greater influence of gypsum type minerals producing a <br />geochemical makeup of predominately calcium sulfate type water in the coal <br />zone that was mined versus a greater influence of calcite type minerals <br />producing a geochemical makeup of predominately calcium/sodium bicarbonate <br />type water in the Big White. This is consistent with field observations <br />of beds of oyster bioherme overlying the Big White (nearly pure CaC03) <br />and siderite nodules within the top of the Big White (nearly pure FeC03). <br />Within the coal zone that was mined, the occurrence of groundwater was <br />limited due to close proximity of the recharge area to the south. The <br />baseline data presented in Table 4 of Appendix L of the Permit indicates <br />no significant difference in water quality from seam to seam in the zone ri~T;,'_ ~' - <br />that was mined. Water that was encountered was generally limited to the ~ <br />~> <br />3265h / ~ ~, <br />(]) <br />