2020-10-22_PERMIT FILE - C1981012A ‎(4)‎

• Permit No: C1981012A
• IBM Index Class Name: Permit File
• Doc Date: 10/22/2020
• Section_Exhibit Name: Section 2.05 Operation and Reclamation Plan
• Media Type: D
• Archive: Yes

103
These standards and discharge analyses are contained in Exhibit 22, NPDES
permit and in the Annual Hydrology Reports.
Long term Hydrologic Impacts. Following the completion of mining, the
underground working will flood and the potentiometric surface in the coal
seams will rebound to near the pre -mining level. Physically the overburden and
coal will have increased inter connection and transmissivity for a distance of up
to 195 feet above the highest mined seam and will act as an integrated
hydrologic unit because of increased fracturing. The 1980 WWL Report
estimated that the potentiometric surface would recover to the original level of
water in the coal (page 56) Hole LA 221 had a water level in 1976 located
304 feet above the top of the Maxwell seam of coal (1994 supplement to
Exhibit 8 Table 3A). The elevation of the Allen seam of coal in the
approximate center of the New Elk Mine is 7,150. If the 1976 water level
information is representative of the original potentiometric surface then the
anticipated equilibrium level of water in the coal seam at New Elk Mine would
be about 7,450 feet elevation. Given the approximate nature of the water level
estimation and the proximity of the predicted elevation to the elevation to the
East Portal (7,460 feet) NECC will install a 6 PVC pipe to discharge
groundwater from the portal in the event that surface discharge occurs.
The water quality of the water filling the mine will reflect a mixture of five years
of pumping of thickener into the mine with inflow from the coal seam and other
sources. This will not materially change the beneficial uses that can be acquired
from the Allen and Apache seams as they are not acceptable for use as a domestic
water source or a flood irrigation source due to salinity levels. In addition, the
coal seam aquifers exceed MLRD suspect levels for stock watering for iron
manganese and fluoride.
Water quality along the Middle Fork of the Purgatoire will experience a
diminished water quality following the discharge of water from the flooded
workings. Salinity, sulfate, and SAR levels will increase, but projections of
water quality during low flow show that beneficial uses will not be
compromised. Ammonia concentrations in the river have historically exceeded
chronic aquatic life receiving stream standards. The discharge of water from the
flooded workings is projected to improve the water slightly, but not enough to
meet the standards. Table 26C (Figure 22 at end of this Section)
delineates loading of parameters which potentially could impair use.
Monitoring of impacts during mining and previous studies of probable
hydrologic consequences (WWL, 1980 and Greystone, 1994) indicate that
underground inflows and mine dewatering have little or no communication with
surface water. This conclusion is consistent with the subsidence analysis and
conceptual model for the New Elk Mine. The maximum extent of subsidence
fracturing with increased vertical transmissivity is projected to extend 195 feet
above the top of the highest mined coal. The minimum thickness of
overburden between the Apache seam and drainage bottoms is 450 feet. A zone
Section 2.05 RN -6 Revised 02/07/2017