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RULE 2 PERMITS <br /> Permit Area <br /> No significant effect on surface water quality in or adjacent to the permit area will occur as a result <br /> of mining operations. Water quality in and adjacent to the mining area is highly variable with <br /> primary constituents of concern reflecting seasonal and precipitation related trends. <br /> TSS values show extreme fluctuations at Taylor, Wilson and Goodspring Creeks. Sediment yield <br /> rates for the mine area using the Universal Soil Loss Equation and a rainfall factor of 30.0 averaged <br /> 3.17 tons/acre/year for the mine permit area. This average was broken down into the component <br /> parts of undisturbed land and land being mined or in a stage of reclamation. The total acreage <br /> contributing to these estimates is 4118 acres of which a maximum of 1000 acres will be disturbed <br /> at any one time. The estimated yield of 3.5 tons/acre/year for the disturbed land is much less than <br /> the 5.0 tons/acre/year maximum acceptable topsoil loss from agriculturally productive land <br /> calculated by the U. S. Department of Agriculture Soil Conservation Service (SCS). The design <br /> limit was based on continued productivity of topsoils for crop production. <br /> TSS will be controlled in runoff from the permit area by detention ponds which have been designed <br /> to retain runoff from the 10-year, 24-hour event. <br /> Water is periodically released from the sediment ponds when TSS and other parameters meet the <br /> discharge standards for the Colowyo NPDES Permit. <br /> TDS concentrations are expected to remain within the ranges of values known to exist presently. <br /> The data presented and discussed earlier shows tremendous fluctuations. TDS is inversely related <br /> to flow. That is, as the flow decreases the TDS values increase as a result of a larger proportion of <br /> groundwater seepage into the drainages as the seasons progress. Runoff-related TDS values are <br /> much less due to the dilution of the minerals influencing this constituent. <br /> Specific conductivity is a measure of TDS and also shows the same variability. Parker and Turk <br /> (1981)and Bishop and others(1982)have examined and discussed the potential impacts of mining <br /> on the hydrology of the Yampa River Basin, and have related TDS and specific conductivity to <br /> predictive models of impacts. Both studies show that the Colowyo Mine will have no significant <br /> impact on the water quality for the short and long term. Other constituents will not be significantly <br /> affected as a result of mining. Iron and manganese mean values did not exceed specific health <br /> related criterion or show signs of acid mine drainage. <br /> Based on the data collected over the life of the mine to date and on the projections made by <br /> Skogerboe and others (1979), Parker and Turk (1981) and Bishop and others (1982), it is evident <br /> that the Colowyo Mine will not have a significant long term impact on the surface water quality in <br /> the permit area. The establishment of surface water monitoring locations by Colowyo on <br /> Goodspring Creek, both above and below the mining operation, was designed to identify mining <br /> impacts on surface water. To date,there has been no significant differences between the locations. <br /> As shown in the 1986 Annual Report,there were increases in all parameters during 1984 and 1985, <br /> but the same trends were documented for all surface water monitoring locations. Surface water <br /> monitoring locations are shown on Map 10B. <br /> Rule 2 Permits 2.04-36 Revision Date: 12/20/19 <br /> Revision No.: TR-135 <br />