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well W-5. Comparison of data from the two wells shows no impacts to the alluvial aquifer downgradient from mining. Monitoring data from alluvial monitoring well A-1, inside the permit area, indicate possible degradation of alluvial water quality from leachate discharging from either the Barren Ridge pit or the East pit. The degradation has not impaired use of alluvial water within the permit area. The degradation does not extend down-gradient from the permit area, as shown by data from well W-5. Compliance with Basic Standards for Ground Water -The Colorado Water Quality Control Commission's Basic Standards for Ground Water prohibit the Chimney Rock Mine from degrading ground water beyond ambient quality. The Commission's Regulation 41.5(C)(6)(b)(iii) ofthe Interim Narrative Standazd allows the use of post-1/31 /94 water quality data as ambient quality because the mine did not initiate any new or increased sources of contamination (coal spoil) upgradient from ground water points of compliance after 1 /31/94. Currently prevailing ground water quality can be considered as ambient quality; therefore, the mine complies with the Basic Standards. Protection of Ground W ater Recharge Cap acity - The area disturbed by mining at Chimney Rock comprises less than 1 % of the length of the outcrop belt on the northeastern margin of the San Juan Basin where ground water is recharged. This disturbed azea is too small to have reduced the regional ground water rechazge below the approximate premining rechazge rate. On a local scale, the disturbed azea does not significantly divert ground water flows to surface water flows (via spoil springs), and surface water infiltration has not been impaired. Therefore, the approximate premining ground water rechazge rate has been preserved locally. Impacts to Surface Water -The loading of Stollsteimer Creek alluvium with dissolved solids has never resulted in violations ofNPDES limitations or instream standards. Sustained stream flows, and the compliance with NPDES discharge limitations and instream standards, indicate Kaiser has prevented material damage to the surface water hydrologic balance outside the permit. The pastureland post-mining land use in the permit area has not been impaired by changes to the hydrologic balance caused by Kaiser, if any. The changes were the minimum that can be expected from a surface mining operation. Future surface water pollution caused by Kaiser's mining operation, if any, should not significantly exceed the current level because the future discharge rate of spoil leachate into the Stollsteimer Creek alluvium will be a small percentage of the creek's flow, thus allowing adequate dilution. Page 12 of the PHC in the permit predicts that at Stollsteimer Creek's historical low-flow of 1.78 cfs, the predicted 25 gpm of leachate discharge into the creek would increase the creek's TDS by 14 mg/1, from 557 mg/1 to 571 mg/1. The increase would be a small fraction of 14 mgll during imgation season when streamflow typically is an order of magnitude lazger than during low-flow. Impacts to Alluvial Valley Floors (AVFs) -Regrading and revegetation has remediated the impacts of the physical disruption caused to the Stollsteimer Creek AVF by Kaiser's mining operation. The revegetation success standazds set for the Stollsteimer Creek AVF were based on what is necessary for the AVF to regain its pre-mining agricultural productivity. As previously discussed in this Findings document, Kaiser has successfully achieved the revegetation standards on the AVF; therefore, the pre-mining productivity of the AVF has been restored. Sustained stream flows in Stollsteimer Creek since Kaiser's operations began indicate Kaiser has not depleted the supply of water to the AVF. Although post-mining electroconductivity values of surface and alluvial waters in 12