Laserfiche WebLink
4.0 <br />There is potential for dewatering of groundwater aquifers located within and above the Maxwell coal seam <br />member of the Raton Formation. Previous studies included in the mine permit document project inflow of as <br />much as 180 gpm and indicate an area of influence on groundwater up to 2.1 miles from the perimeter of the <br />mine workings. The average discharge when discharge occurred from the mine at Pond 002 was 76 gpm. The <br />maximum discharge from Pond 002 was 148 gpm. The workings are now flooding, which is resulting in <br />changes in the potentiometric surface around the mine in the future. <br />Localized dewatering was evident from the flow of groundwater (seeps, etc.) into the undergrow~d mine <br />workings, and the pumping and discharge of these mine waters into surface flows. However, no loss of springs <br />or impacts to existing adjudicated wel Is have been noticed to date. Relatively constant flaws suggest a general <br />low quantity of water within the formations, and retention of member integrity with retention of low vertical <br />transmissivity of free water. Future monitoring will be used to further identify effects of dewatering. <br />There has been no noticeable impact on groundwater hydrology from the gradual flooding ofthe Golden Eagle <br />Mine. The apparent low vertical transmissivity and integrity of the surrounding rocks might inhibit any effect <br />of free water on the recharge of the overburden. Monitoring of the underground workings began in 1997 at <br />GEM-l, GEM-2, and GEM-3. Rate of filling ofthe workings will be monitored through time and any effects <br />will be identified. Table 3.1-1 presents the average water level data for thethreewells. All data is presented in <br />Appendix A. GEM-] showed a slight rise in water level in 2003. GEM-2 had water for the first time in the <br />fourth quarter of 2000 and the level rose approximately 20 feet in 2003. GEM-3 had water for the first time in <br />first quarter of 2001 and the level rose approximately 20 feet in 2003. GEM-1 is the highest elevation of the <br />mine floor of the three GEM wells. Water measured at this site is probably spilling to the north into the <br />extensive area of longwall mining na'th of Highway 12. As measured, the current potentiometric surface of <br />water in GEM-l, GEM-2 and GEM-3 is approximately 6802. At the current rate of flooding all areas of the <br />mine should reach equilibrium by the end of 2004. <br />3.2 WATER QUALITY <br />PAW-6 documents an additional loading of dissolved solids greater than that observed at PAW-5, in that it <br />detects mine water discharges. Solids levels in the PAW-6 sample taken in 2003 show decreases from <br />previous years which indicates that effects of mine waterdisehargearediminishing. Figure 3.2-l shows water <br />quality at the two PAW stations. However, the historic records of PRS-3 indicates little effect on stream <br />quality from the local sources of alluvial groundwater. Well CCAW-1 is located down gradient of the <br />development waste storage area and shows elevated levels of dissolved solids (Figure 3.2-1). <br />Basin monitored the overburden and the coal seams adjacent to the mine. The five overburden wells were <br />completed in zones ofelevated flow during drilling, and consequently reflect differentstrata. Two overburden <br />wells located north of the workings, NM-20 and NM-22 exhibited very alkaline conditions (pH ranging from <br />9.9-1 1.85) and were sodiwn carbonate waters. They have moderate salinity with conductivities ranging from <br />400 - 504 mg/I. There are four coal wells associated with the monitoring program. Site NM-23, north of the <br />Golden Eagle workings is a slightly acidic (pH 5.74 - 6.2), very saline (TDS of 2400 mg/I) sodium/iron <br />chloride water. Previously this was an excessively alkaline (pFl 9.4 - 11.46) sodium bicarbonate water. Again, <br />there is some thought that the pump extraction process modified the chemistry of the water. This site has <br />elevated iron concentrations, and levels of manganese and chloride which exceed ground water standards. No <br />water quality samples were collected from deep wells during 2003 as a result ofthe new monitoring program. <br />Water quality of the mine workings have been monitored as the mine is allowed to fill. Water samples have <br />been collected at GEM-I since 1999 and GEM-2 since 2002. The water is a sodium bicarbonate type with <br />elevated salinity (TDS ranging from 1050 to 1540 mg/L). Figure 3.2-2 shows water quality at the two GEM <br />stations. <br />292-34 GolUai Eu~le Mine Rpt (feb.l 1.04).doc 3-3 <br />