2020-03-24_PERMIT FILE - C1981019A (5)

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RULE 2 PERMITS at Mouth 20,600 20,564 -36 -99.83 Yampa River at Maybell 1,120,000 1,119,964 -36 100.00 Runoff in the permit area, which is diverted or detained, will continue to reach the historic drainages. A portion of the water rights held by Colowyo on Goodspring Creek may be consumed in accordance with the augmentation plan discussed in Exhibit 7. This possible consumption will possibly affect the agricultural practices on a minor portion of the Goodspring Creek Valley Floor. However, since the Colowyo Coal Company owns the property to be withdrawn from irrigation, and these lands are not an integral part of any ranching or farming operation, the effect will be minimal. Runoff detained in the detention ponds will be released from time to time in accordance with the NPDES permit. These ponds will only interrupt flow resulting from precipitation falling directly on the mine and associated areas. As discussed in the Hydrologic Balance section above, this flow is a fraction of the total flow in all of the drainages and, therefore, is not significant. Potential Impacts From Mining-Water Quality Groundwater General Area The quality of the groundwater which exists in the general area will not be affected by the Colowyo Mine. Impacts on the quality would only occur as a result of extreme changes in the (1) recharge rate, which is presently minimal; (2) lithology; or(3) chemistry of the geological formations. This is highly unlikely as the Colowyo Coal Company intends to only mine the area within the permit boundaries. Permit Area No significant changes will occur in the quality of the groundwater in or adjacent to the mine as a result of mining. The chemical characteristics of the overburden and leachate, presented earlier, will not seriously affect the quality of the limited groundwater present. Minimal amounts of water within backfilled spoil areas are expected to show temporary increases in TDS owing to rapid dissolution of relatively soluble minerals such as gypsum, calcite, thenardite and various clay minerals. The increase in surface area of freshly exposed, broken backfill material is readily leached. Resulting temporary increases in Ca, Mg, Na, SO4 and CO3 will subsequently increase TDS and conductivity over time until the readily available minerals are leached out. Compared to the undetectable effects of the mining operation, the effects on groundwater were much greater due to natural conditions of high precipitation, infiltration and runoff during 1984 and to a lesser extent 1985. Concentrations for the major ions mentioned above increased during 1984 and 1985, however, there was a decrease at all sites for 1986 which indicates the natural system was responsible for the temporary increase in concentration. Documentation for this observation is found in the 1984, 1985 and 1986 Annual Reports. Note that two additional groundwater monitoring wells have been completed to obtain background information for the Rule 2 Permits 2.04-34 Revision Date: 12/20/19 Revision No.: TR-135