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Wes/ E(k Mine <br />of this permit document, because they contain important findings regarding groundwater from <br />• the Jumbo Mountain Decision Document, the West Elk Mine permit document, including <br />revisions and renewals, other mines in the North Fork Valley, and the CHIA. <br />Surface and groundwater occurrence have been studied extensively by MCC since 1976. Map <br />34 shows the existing hydrologic monitoring network. The groundwater network for the <br />permit areas consists of groundwater monitoring wells which are used to monitor and collect <br />water level and water quality data. <br />The nature of the groundwater resources at the mine is described in Section 2.04.7 and is not <br />repeated herein. However, from the standpoint of determining probable hydrologic <br />consequences, it is necessary to distinguish among the different kinds of groundwater at the <br />site. These include alluvial groundwater, colluvial groundwater and bedrock groundwater. <br />Each is described as follows: <br />Alluvial groundwater is found within the unconsolidated sediments adjacent to and <br />underlying stream channels large enough to have deposited such materials. Within the <br />permit area, there is little identifiable alluvium with the exception of Sylvester Gulch, <br />the North Fork and the Dry Fork of Minnesota Creek. Impacts to alluvial groundwater <br />are expected to be minimal because of its limited existence within the longwall angle of <br />draw. <br />• colluvial groundwater is found within the loose, unconsolidated soil material and/or <br />rock fragments deposited by rainwash, sheetwash or continuous downslope creep. <br />Many of the seeps and springs within the permit area are a surface expression of the <br />groundwater contained within the colluvium. colluvial groundwater generally tends to <br />be locally discontinuous, is dependent upon local snowmelt and precipitation events for <br />recharge, and is usually within materials which have relatively little storage capacity. <br />As such, interception of colluvial groundwater will generally produce flows which <br />diminish over time as the water from storage is drained faster than the available <br />recharge. Impacts to colluvial groundwater is normally considered to be deminimus <br />since such groundwater is dependent upon factors which make this source of water <br />unreliable for sustained use. <br />Bedrock groundwater is found within the consolidated rock with sufficient storage and <br />permeability to retain and transmit subsurface water. The majority of the perennial <br />seeps and springs within the permit area are probably supplied by bedrock <br />groundwater. However, the discontinuous nature of the more permeable units and their <br />relatively small storage capacity within the Mesaverde Formation at the West Elk Mine, <br />along with the seasonal variability of these spring flows, supports the conclusion that <br />groundwater resources in the area are limited at best. Impacts to bedrock groundwater <br />are generally considered to be of little consequence because of its unreliability as a <br />sustained supply source. Presently, the only sustained inflows to the mine are from <br />• <br />2.~5-210 RevisedJ~m. 1995 PR06, Revised Nov. 1998 TR80: Revised Jan 1998 PR08 <br />