2011-09-26_PERMIT FILE - C1981012 ‎(24)‎

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 9/26/2011
• Section_Exhibit Name: EXHIBIT 08 HYDROLOGY AND GEOLOGY INFORMATION
• Media Type: D
• Archive: No

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SUMMARY AND CONCLUSIONS
Data, analyses, and conclusions of a hydrologic investigation in the
vicinity of CFBI Steel Corporation's Allen and Maxwell Mines are presented
in this report. These mines are underground coal mines located in Las Animas
County on the Purgatoire River approximately 30 miles west of Trinidad,
i
Colorado. The study included characterization of the hydraulic properties
of the coal seam, overburden, and alluvium by field and laboratory tests.
A combination of drill holes and backhoe pits were used to investigate the
distribution of alluvium and terrace materials in the vicinity of the Maxwell
Mine. Estimates of eventual inflows to the Maxwell Mine were made and these
' were coupled with water quality data on mine and stream discharges to calcu-
late the expected effect of mining on the quality of waters in the Purgatoire
River. A water balance was used to estimate the deep percolation from the
active refuse pile at the Allen Mine. The chemical characteristics of the
subsurface discharge from the refuse pile were determined and the influence
of the waste material on the quality of stream waters was estimated.
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Data from this investigation, studies by others, and from the Allen
Mine indicate a very low water-bearing capacity of strata in the Raton forma-
tion.
The ground-water inflows to the Maxwell Mine are expected to be on the
order of 180 gpm at full mine development. The source of this discharge
is the coal seam and vertical flow through the overburden in response to
the drawdown caused by the mine. This estimate of inflow is consistent •.vith
the inflow now being observed in both the Maxwell and Allen Mines. Using a
conservatively estimated value for mean low flow in the Purgatoire River,
discharge of this inflow will cause an estimated increase of dissolved solids
in the stream equal to 47 mg/1. The increase in the average dissolved
solids concentration in the mean annual flow at the Maxwell Mine location
will be about 13 mg/1. Estimated chanoes in trace element concentrations
arP very small. Similar conclusions were reached relative to the effect of
current mine discharge from the Allen, the estimated increase in dissolved
solids being 32 mg/1. It is estimated that the combined contribution of the
• . current Maxwell and Allen discharges and the active refuse pile at the Allen
to the total salt pickup between Stonewall and Madrid is about 2 percent.