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Ground Water Impacts <br />The operator has monitored the quality and levels of ground water in mine backfill aquifers <br />(GD-3, GF-5, GF-7 and GF-11). These four wells were all included within the SL-4 Phase III <br />bond release area. However, because they are used as ash monitoring wells they are still <br />sampled and are representative of backfilled aquifer conditions occurring in reclaimed blocks <br />proposed for the SL-10 bond release application. Historical data from the backfill wells <br />indicate leachate forms in the spoil/ash backfill. This leachate is high in dissolved solids <br />(TDS), mainly sulfates, and is alkaline. TDS concentrations appear to peak around 4,000 <br />mg/1. This concentration may continue for several hundred years, as predicted for the Seneca <br />II Mine in Routt County, Colorado (USGS Water-Resources Investigations Report 92-4187). <br />The alkalinity (pH near 7) appears to have prevented significant mobilization of metals in the <br />spoil/ash backfill. The elevations of water levels in the bedrock wells are higher than the <br />highest elevations to which leachate levels can be expected to rise in spoil/ash backfill; <br />therefore, significant invasion of the bedrock units by leachate is unlikely. Spoil/ash leachate <br />has not been detected in the downgradient bedrock monitoring wells, although ground water <br />flow velocities in the bedrock units may be too slow for leachate to have reached the farthest <br />downgradient wells. <br />Surface Water Impacts <br />Within the area of the proposed SL-10 bond release, surface water flows through six different <br />watersheds. This includes discharges through six active NPDES outfalls. The six active <br />discharge points are all covered under NPDES Permit CO-0032115 and include Johnson Gulch, <br />No Name Gulch, East Pyeatt Gulch, West Pyeatt Gulch, Grouse Gulch, and Sage Gulch. Surface <br />water consistently discharges only through Johnson, No Name and East Pyeatt Gulches. The <br />remaining discharge points seldom if ever record surface water runoff. Throughout the sampling <br />history of these discharge points, no violations of CO-0032115 standards have occurred. <br />Spoil springs that were present in the bottoms of drainages at the down-gradient contact of spoils <br />and non-mined areas in Johnson and No Name Gulches were released from Phase III bond <br />liability with the approval of SL-04. No spoil springs are present on any of the reclaimed lands <br />proposed for bond release in SL-10. <br />Compliance with Basic Standards for Ground Water <br />The absence of leachate plume development in the bedrock units indicates that for bedrock <br />units in and adjacent to the bond release area, the mine operator is in compliance with the <br />Colorado Water Quality Control Commission's Basic Standards for Ground Water (Rule 41). <br />Any ground water in alluvial deposits in the bond release area meets the classification of <br />Limited Use and Quality because the alluvial water is of such small volume in these thin, <br />laterally discontinuous deposits that it is not currently used and is unlikely to be used in the <br />future. The Basic Standards for Ground Water have no water quality standards for the <br />Trapper Mine Page 10 November 17, 2007 <br />Phase III Bond Release