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the pits. The most likely impact caused by migration of the leachate would be salt loading of <br />bedrock or alluvial aquifers. <br />Impacts to Bedrock Aquifers -The Fruitland Formation is the only bedrock aquifer that is in the <br />ground water flow path of the previously-described spoil leachate. There is no pre-mining <br />monitoring data from bedrock wells. Kaiser monitored the Fruitland formation dovvngradient from <br />the Barren Ridge pit in well W-9. Monitoring was conducted from 1985 through 1991. h showed no <br />impacts from leachate. Kaiser monitored the Fruitland underneath the Barren Ridge pit in well W-10. <br />Monitoring spanned 1985 through 1991. This well showed a significant increase in total dissolved <br />solids (on the order of 2,000 mg/1) when it was last monitored in 1991. This increase is consistent <br />with degradation of ground water in the Fruitland at this location from an influx of leachate from the <br />pit in the Revision 1 area. That pit is upgradient from W-10 and had been reclaimed a few years <br />earlier. If leachate caused this degradation, the impact would be considered a destruction of a small, <br />localized aquifer that is not used; this hydrologic impact does not rise to the level of material <br />damage. A plume of degraded water resulting from such degradation can be expected to nugrate not <br />much beyond the permit boundary due to the low permeability of Fruitland Formation sandstones. <br />The salinity of Fruitland Formation ground water naturally increases faz above 2,000 mg/1 of <br />dissolved solids dovvngradient from the Chimney Rock Mine as shown by gas field brines in the San <br />Juan Basin. Wells W-9 and W-10 have shown no impacts to the potentiometric surface of the <br />Fruitland Formation from mining at Chimney Rock. <br />Impacts to Alluvial Aquifers. Kaiser collected baseline water level and water quality data at the <br />upstream alluvial monitoring well W-1 in late 1980 and eazly 1981. The well is completed in alluvial <br />deposits of Stollsteimer Creek. From 1985 through 2002, Kaiser monitored alluvial water levels and <br />water quality upstream from the Chimney Rock Mine in well W-l, and downstream from the mine in <br />well W-5. Comparison of data from the two wells shows no impacts to the alluvial aquifer <br />downgradient from mining. Monitoring data from alluvial monitoring well A-1, inside the permit <br />area, indicate possible degradation of alluvial water quality from leachate dischazging from either the <br />Barren Ridge pit or the East pit. The degradation has not impaired use of alluvial water within the <br />permit azea. The degradation does not extend down-gradient from the permit azea, as shown by data <br />from well W-5. <br />Compliance with Basic Standards for Ground Water -The Colorado Water Quality Control <br />Commission's Basic Standards for Ground Water prohibit the Chimney Rock Mine from <br />degrading ground water beyond ambient quality. The Commission's Regulation 41.5(C)(6)(b)(iii) <br />of the Interim Narrative Standazd allows the use ofpost-1/31/94 water quality data as ambient <br />quality because the mine did not initiate any new or increased sources of contamination (coal <br />spoil) upgradient from ground water points of compliance after 1/31/94. Cun•ently prevailing <br />ground water quality can be considered as ambient quality; therefore, the mine complies with the <br />Basic Standards as a consequence of mine inactivity since I/31/94. Also, a leachate plume in <br />Stollsteimer Creek alluvium can be expected to extend no more than a few hundred feet <br />downstream from the mine, owing to the laterally discontinuous nature of the alluvium and <br />dilution of alluvial water by flowing stream water. If the length of such a plume is considered to <br />be the "specified area", as this term is defined in the Basic Standazds for Ground Water, then the <br />alluvial water can be tentatively classified as water of Limited Use and Quality because within <br />12 <br />