2015-03-24_REVISION - C1981014 - Laserfiche WebLink

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ii) As previously stated, the elevation of the floor of the mine workings is 5855 feet. The mine workings were 5.5 feet in height in the vicinity of MW -NW, the referenced elevation of 5860.5 feet stated in the BBA 2013 Summary Report is the elevation of the roof of the workings where the steel casing was cut off during mining operations. iii) Regarding MW -16, although it is uncertain as to why water levels fluctuated in MW-16 during 1979 -2000, potential water sources for MW-16 are the abandoned Peacock Mine and the abandoned Pine Gulch Mine, both being in the Red Arrow seam and situate up-dip from MW -16. Both mines are located at the outcrop and are recharged by precipitation. Given that the flooded Peacock mine in particular, inflowed into the Southfield Main Entries (Peacock Inflow 2), and that the Peacock is recharged by precipitation, it is conceivable that static water pressures in the abandoned mines (draining /recharging) were influencing the water levels in MW -16. The Division's statement that MW -16 was "often reported as dry at I]Oft with depth to water indicated as 110 ft bgs" is contradictory. Various AHR's reported "mud" at 110 ft bgs which does not imply that that was the water level, i.e., the well had no water at 110 ft as reported in the respective AHR's. More importantly, the 'average' water level in MW -16 during the 1979 — 2000 time period was 104.1 ft bgs — approximately 2 ft above the screened interval of the well. Concerning MW -16 being reported as dry, the above referenced abandoned mines are located parallel to the Southfield Moose Panel and the Pine Gulch Panel #3 workings and being up-dip from MW -16, it is conceivable that the workings influenced water levels in MW -16. Further, as is referenced in the Division's February 12, 2015 Adequacy Review letter, (National Drought Mitigation Center (h :/n /droughtmonitor. unledu) the region has been in drought conditions for several years during which MW-16 has been dry. Nonetheless, according to well completion data, 4 vertical feet of the screen interval is available to accept water if it was present. d) Impacts to Groundwater Quality The PHC section of the PAP predicts the following impact to groundwater quality: • Potential increases in the levels of TDS and concentrations of specific chemical constituents Groundwater at the Southfield Mine has a neutral pH and is of a weak sodium sulfate type, with relatively high levels of Total Dissolved Solids (TDS) and iron. Background water quality data is summarized in table 13 of the PAP and is reproduced below, for quick reference (Table 2). The question of applicable water quality standards was discussed extensively in the June 2013 Memo, where it was determined that water in Southfield's flooded mine workings, as well as water in coal or low permeability rock interbedded with coal down - gradient of the flooded mine workings, does not need to meet drinking water standards, since the ambient water quality does not meet these standards. Additionally, the June 2013 Memo highlighted the fact that the Colorado Division of Water Resources recognizes that groundwater obtained from coal zones is known to be of degraded quality and advises against completing wells for domestic or agricultural purposes in these zones. To illustrate this point further, Table 2 shows the baseline groundwater quality data from the permit with the most stringent water quality standards taken from Tables 1 -4 of Regulation 41 for reference." Parameters where the baseline data exceeds the standard are shown with a red fill. It should be noted that the background data shows a great deal of variation in parameter values. The approved baseline data is apparently the aggregated result of sampling from multiple wells. It is not possible to parse the data to find up- gradient and down - gradient water quality, (presumably the determination was made that background groundwater quality in the area was generally variable and poor), neither is it possible to use the baseline data as a starting point to analyze water quality trends. 13