2015-02-12_REVISION - C1981014 - Laserfiche WebLink

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George V. Patterson, Energy Fuels Coal, Inc. Page 10 February 12, 2015 • Groundwater in the Vermejo Formation is separated from atmospheric pressure by relatively impermeable material; as such it exists under confined conditions. • The potentiometric surface in the Southfield Mine area is not uniform (as a result of the complex lenticular geology and the presence of many abandoned and flooded underground mine workings). • The regional groundwater flow regime is governed by geologic structure, with movement generally down -dip towards the axis of the Chandler syncline, and parallel to the synclinal axis toward the Arkansas River to the north. In the area of the Southfield Mine the general flow regime is to the north -west. • Local groundwater flow patterns are highly spatially variable, and are subject to the influence of: geologic structure; depressions in the potentiometric surface caused by underground mine workings; and variations in the hydraulic gradient resulting from recharge /discharge associated with perched groundwater reservoirs. • Groundwater recharge in the Vermejo formation occurs both in the narrow outcrop west of the Chandler synclinal axis and in the much broader outcrop further east. • Discharge from the Vermejo formation is to the surface water system of the Arkansas River, to the north. Groundwater contributions from the Vermejo Formation to Arkansas River flows are negligible. In the context of this conceptual model, the utility of water levels measured in a relatively small number of monitoring wells sited around the mine workings is extremely limited. The water level within properly constructed wells completed in a confined aquifer does not correspond to the elevation that water exists at in the ground; rather the level in the well is dictated by the elevation the water exists at (the elevation head) and the hydrostatic pressure caused by the weight of material above it (the pressure head). The resultant water level measured in the well is the total hydraulic head, or "head ". If a well (say MW65) is completed in a confined aquifer with the perforated interval at a depth of 968 -988' below the ground surface and the water level in the well is measured at a depth of 250' it does not mean that another well drilled adjacent to the first will encounter water at 250'. Head values measured at monitoring wells completed in confined aquifers are points on an imaginary potentiometric surface (the term "piezometric surface" is no longer used but does occur in the permit text). This explains why the title "Ground Water Elevations" on the 1987 BBA figure and the "Expected Water Level Recovery" label on the 2014 BBA figure are misleading and why the water level in the vicinity of the mine cannot be expected to ever rise above the elevation of the first low - permeability layer above the roof of the mine. Currently water levels in MW23 are a little less than 10 feet higher than the screened interval in the Red Arrow coal seam. Water levels in MW65are approximately 700 feet above the screened interval in the upper and middle Jack O' Lantern seams. These two monitoring wells indicate that groundwater on either side of the mine has a head above the elevation of the mine workings. It is assumed that the workings have not completely filled with water yet; and in any case the workings are either relatively open or filled with unconsolidated rubble with a large pore volume,