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Occurrence, Potential For, and Cost of Abatement of Surface or Groundwater Pollution <br />No occurrence of surface water pollution from precipitation runoff has been identified. A <br />demonstration was made in July 1992 that untreated surface runoff from the reclaimed mine site <br />does not contribute additional suspended solids above natural conditions. Materials available for <br />seedbed prepazation were determined to be nontoxic and valuable as plant rooting media. <br />Therefore, there is little probability of leaching of toxic topsoil. No record was found of <br />dischazge from the remaining two sedimentation ponds {P-9 and the Coal Mine Refuse site) in <br />Colorado Department of Public Health and Environment dischazge monitoring reports (1989 to <br />present), monthly inspection by the Division (1991 to present), or Annual Hydrologic Reports <br />(1989 to present). There was no evidence of surface erosion at the time of the Phase III Bond <br />Release Inspection by the Division. <br />Mine drainage from Portals 1 and 3 is not included in this bond release application. <br />There are two shallow groundwater-monitoring wells in the vicinity of the Mine Waste Refuse <br />Pile (refuse pile). Well D-lA is located duectly downgradient of the refuse pile and well D-2A is <br />located west of well D-lA, outside the probable plume of any groundwater contamination from <br />the refuse pile. Conductivity of water samples from well D-lA rose from 3000 umhos/cm (when <br />installed) to 4000 umhos/cm in 1989, and has stabilized in the vicinity of 4000 umhos/cm to the <br />present. The conductivity of water samples from well D-2A appeazs to be dropping from a initial <br />2,500 to I,000 umhos/cm in yeaz 2000. The impact to groundwater between Well D-lA and <br />North Thompson Creek,- and to the Creek itself, is unknown. There has been no monitoring for, <br />and there is no information available on, the rate of groundwater flow below the waste pile into <br />North Thompson Creek. However, semi-annual measurements of stream conductivity have been <br />taken, in May and September, on North Thompson Creek, above and below the mine. The <br />average conductivity measured in September (low-flow condition) over the past five yeazs above <br />the mine is 177 umhos/cm, and below the mine is 258 umhos/cm. Any flow of Mine Waste <br />Refuse Pile groundwater is, however, only one of several dischazges that may influence <br />downstream pazameters. There aze discharges to the Creek between the two locations of <br />measurements. One discharge is from the pre-law North Thompson Creek Porta12 mine. Another <br />is the dischazge from the Developed Water Resources azea (the source being discharges from <br />Portals I and 3). Another is from (perhaps) natural sources (there is a sulfur smell from a seep <br />between the Mine 1 and Mine 3 portals, and between Portal 1 and the point of downstream <br />monitoring). <br />There is no reason to suspect that ground cover will diminish on reclaimed azeas as the <br />vegetative communities continue to recover. Therefore, there is low potential for pollution of <br />surface waters from erosion of reclaimed azeas. <br />SL-O5, C-81-025, March 24, 2003 <br />Page 21 of 26 Pages <br />