Laserfiche WebLink
Probable Effects on Ground Water Quality: <br />Bedrock Ground Water <br />The Lewis shale has low conductivity values and is generally considered to be an <br />aquitard that retards transmission of surface water to the Twentymile sandstone, the <br />underlying regional aquifer. This low conductivity results in low well yields that <br />preclude the use of waters from the Lewis Shale for other than stock watering (See <br />Seneca II-W Permit Application, Tab 7). Water samples from the two existing <br />alluvial wells at the Loadout, which are completed in part in the underlying Lewis <br />Shale, often exceed water quality standards for stock watering. Operations at the <br />Loadout should not impact this ground water. <br />Alluvial Water <br />Alluvial waters are of poor quality and may be unsuitable for use in irrigation. <br />Leachate from coal stockpiled at the Loadout could potentially infiltrate the alluvium <br />and add dissolved chemical loads to the Dry Creek alluvial aquifer; however, impacts <br />to Dry Creek alluvial water quality should be minimal due to the size of the operation <br />and the composition of the coal. Alluvial ground water monitoring was conducted <br />using wells installed prior to 1993 by the previous operator, HG Coal Company. <br />HGDALI was finished in the alluvium upgradient of the Loadout. HGDAL2 was <br />located downgradient of the Loadout. In October of 1993, a new downgradient well, <br />HGDAL3 was constructed. HGDAL3, was constructed downgradient from the rail <br />loop to assure that potential groundwater impacts from the Loadout could be assessed. <br />CDRMS had expressed concerns that HGDALI and HGDAL2 may have been <br />finished in the Lewis Shale underlying the Dry Creek alluvium. In November 2005, <br />HGTI installed a new monitoring well, HGDAL4, upgradient from the Loadout, that <br />was finished in the Dry Creek alluvium. HGTI continues to monitor HGDAL3 and <br />HGDAL4 in accordance with the approved monitoring plan found in Tab 13 of the <br />permit. HGTI sealed HGDALI and HGDAL2 in September 2007 in accordance with <br />Rule 4.07.3(3). <br />Probable Effects on Ground Water Quantity: <br />The Lewis shale is an aquitard and should not be significantly affected by any <br />additional waters that might be contributed to the site as a result of operations at the <br />Loadout. Water used at the site is drawn from Yampa River alluvium. It is <br />conceivable that waters seeping from sediment ponds and from the operation's leach <br />field may contribute additional water to Dry Creek's alluvium but it is not expected to <br />be significant. <br />Pursuant to Rule 2.07.6(2)(c), the assessment of the probable consequences of the <br />proposed mining operation and the assessment of the probable cumulative impact of <br />all anticipated mining in the area on the hydrologic balance, as described in Rule <br />2.05.6(3), have been made. The proposed operation has been found to be designed to <br />prevent material damage to the hydrologic balance outside the permit area. <br />20