2021-04-29_REPORT - C1981010 - Laserfiche WebLink

Home Browse Search

Each pit disrupts the potentiometric surface of confined aquifers. After reclamation,monitoring data show recovery S. Restoration of of the potentiometric surface outside of backfilled pits and ground water CDRMS partial recovery of potentiometric surface inside backfilled recharge to regulation Comment pits. Spoil springs may reduce groundwater recharge by approximate pre- 4.05.12(3) diverting groundwater flow to surface flow. However, mining rate Trapper's expected total aggregate spoil spring discharge of less than 1 cfs are too small to reduce recharge below the approximate pre-mining rate. The Probable Hydrologic Consequences(PHC) section of Trapper's mining and reclamation permit(Section 4.8.3), discusses the possibility of a high-TDS plume of coal spoil leachate forming in the Third White Sandstone downgradient from the Trapper Mine in Section 29-T6N- 90W. Such a plume would not be expected to form until several years,possibly decades,after the pit is reclaimed in the adjoining Section 32. Compared to pre-mining ground water conditions, such a plume would have elevated dissolved solids,which could possibly impair the use of ground water in the Third White Sandstone. Spoil leachate could also invade the alluvium in Flume Gulch by seeping down into the subsurface from spoil T. Prevention of springs flowing on the land surface in the gulch. adverse impacts CDRMS to ground water regulation Comment The Third White Sandstone is monitored in the area of the systems outside 4.05.11 possible plume in well GP-9, and the alluvium is monitored the permit area with the Coy well. Monitoring data from both wells indicate that a plume has not reached these wells. Well GC-2 completed in the 31d White Sandstone up-gradient of well GP-9 has shown evidence of the predicted plume with elevated TDS levels and Sulfate levels that initially increased over time but have since stabilized and appear to be decreasing. Other wells down-gradient of spoil backfill such as well P-8 completed in the Third White Sandstone and well GD-2 completed in the R aquifer are also showing signs of elevated TDS/Sulfate likely leaching from backfilled spoils. TDS Levels in well P-8 appear to have stabilized after a large increase in 1995 but are remaining above baseline levels. TDS/Sulfate levels in the alluvial wells have fluctuated significantly over the years but appear to be within natural levels according to the report. Page 4