GENERAL32460 - Laserfiche WebLink

Home Browse Search

A plume of degraded water resulting from such degradation can be expected to not migrate much beyond the permit boundary due to the low permeability of Fruitland Forration sandstones. The salinity of Fruitland Formation ground water naturally increases downgradient from the Chimney Rock Mine as shown by gas field brines in the San Juan Basin. Wells W-9 and W-10 have shown no impacts to the potentiometric surface of the Fruitland Formation from mining at Chimney Rock. Impacts to Alluvial Aquifers. Kaiser collected baseline water level and water quality data at the upstream alluvial monitoring well W-1 in late 1980 and early 1981. The well is completed in alluvial deposits of Stollsteimer Creek. From 1985 through 2002, Kaiser monitored alluvial water levels and water quality upstream from the Chimney Rock Mine in well W-1, and downstream from the mine in well W-5. Compazison 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 azea, indicate possible degradation of alluvial water quality from leachate dischazging from either the Barren Ridge pit or the East pit. The degradation has not impaired use of alluvial water within the permit azea. The degradation does not extend down-gradient from the permit azea, as shown by data from well W-5. Compliance with Basic Standards for Ground Water -The Colorado Water Quality Control Commission's Basic Standazds 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 Standard 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 Water Recharge Capacity -The azea disturbed by mining at Chimney Rock comprises less than 1 % of the length of the outcrop belt on the northeastern mazgin of the San Juan Basin where ground water is rechazged. 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 area 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 standazds. 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 azea 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 dischazge 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 9