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County, Colorado (USGS Water -Resources Investigations Report 92-4187). The alkalinity (pH near <br />7), appears to have prevented significant mobilization of metals in the spoil/ash backfill. <br />F, L and Z pits have mined the Q and R coal seams therefore the QR aquifer becomes the major aquifer <br />of interest for this bond release as the bond release block comprises parcels from pits F and Z. Wells <br />GC -3, GP -5, GF -6, GLEV-1 are utilized to monitor the QR aquifer. Well GC -3 exhibited a gradual <br />decline in water levels as mining moved into the area of response. Upgradient mining is currently <br />occurring above this well. Water levels in GP -5 and GF -11 generally trend up. F pit mining has not <br />significantly affected water levels in GP -5. The GLEV-1 well is located on the eastern edge of active <br />mining. TDS concentration in the QR aquifer are monitored downgradient at well GF -6 and have shown <br />little influence from upgradient mining other than a very slight overall increasing trend, well within <br />natural variations. TDS concentration in wells GP -5 and GLEV-1 appear steady with a slightly lower <br />concentration in GLEV-1. <br />No impacts to adjudicated wells are anticipated in areas down gradient of the land proposed for <br />release. <br />Surface Water Impacts <br />Within the area of the proposed SL20 bond release, surface water flows through four different <br />watersheds. This includes discharges through four active NPDES outfalls. The four active discharge <br />points are all covered under NPDES Permit 000032115 and are located in the following gulches: Far <br />East Buzzard (NPDES 14), East Pyeatt (NPDES 11), West Flume (NPDES 19), and Oak (NPDES 17), <br />Gulches. All runoff is tributary to the Yampa River. <br />Surface water consistently discharges only through Johnson, No Name, East Pyeatt, and Oak Gulches. <br />The remaining discharge points seldom if ever record surface water runoff. Throughout the sampling <br />history of these discharge points, no violations of C00032115 standards have occurred. Seasonal <br />excursion of TSS and total iron occasionally occur during spring snowmelt or as a result of an intense <br />precipitation event. Seasonal excursion as per TMI's discharge permit do not constitute a violation of <br />the primary effluent limitations as they fall under the alternate limitations. Division reviews indicate <br />that there have been no significant water quality problems at these discharge points. <br />No known spoil springs appear to be present on any of the reclaimed lands proposed for bond release <br />in SL20. Spoil springs that were present at the down gradient contact of spoils and non -mined areas <br />in Johnson and No Name Gulches were Phase III released in SL4. <br />Compliance with Basic Standards for Ground Water <br />The absence of leachate plume development in the bedrock units indicates that for bedrock units in <br />and adjacent to the bond release area, the mine operator is in compliance with the Colorado Water <br />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 Limited Use <br />and Quality because the alluvial water is of such small volume in the thin, laterally discontinuous <br />deposits present that it is not currently used and is unlikely to be used in the future. The Basic Standards <br />for Ground Water have no water quality standards for the Limited Use and Quality classification. <br />Division reviews indicate that there have been no significant ground water quality problems in the <br />Permit Number C1981010 <br />SL20 Page 13 of 17 <br />