2015-04-23_REVISION - C1981014 (2)

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George V. Patterson, Energy Fuels Coal, Inc. Page 4 April 23, 2015 mine personnel. This recorded inflow data is quite sufficient to make a reasonable projection for the approximate time required for refilling of the mine. Bishop- Brogden and Associates (BBA) has prepared a detailed response to the Division's technical evaluation of the Southfield mine refilling which can be found in APPENDIX "B" attached to this submittal DRMS: In the 2013 Summary Report BBA attempted to model the refilling of the mine using: (i) an estimate of the volume of the mine cavity, and (ii) estimated volumetric rates of mine inflow; with three different scenarios of hydrogeologic connectivity within the workings. The report concluded that the time for the water level in the mine to reach 5860.5' would be 106 -200 years. There is significant uncertainty associated with the values of all of the input parameters for this calculation, for example: • There is confusion about the lowest elevation that could be measured at MWNW. • There is uncertainty about the extent to which the mine cavity has collapsed, which has implications for the volume of the remaining cavity. The 5,700 Acre feet value quoted from page 2.05.6 -32 is a maximum value for the volume of the cavity, taking no account of subsidence or natural caving. • The mine inflow volumes (summarized in table 1) are quoted to a level of precision that gives a misleading impression of the accuracy of the value. Since it remains unclear how the estimates were made there can be very little confidence in these values. • As acknowledged by BBA, the integrity of the seals within the mine workings is unknown. EFCL- • The elevation of the floor of the mine workings is 5855 feet. The mine workings were 5.5 feet in height in the vicinity ofMW -NW, the referenced elevation of 5860.5 feet is the elevation of the roof of the workings where the steel casing was cut off during mining operations; • Subsidence and caving varies with the varying strata types. By approved design, portions of the mine were not pillared (pillars left in place). These areas are depicted on the Southfield Final Closure Map on file with the DRMS, • Mine inflows were monitored and recorded throughout the life of mining operations (Annual Hydrology Reports). Approximately 85% of the inflows were pumped and metered and the data recorded by the Southfield mine engineer and qualified mine personnel; • Integrity of the mine seals is unknown; therefore BBA offered three models of potential conditions that could exist in the mine. DRMS: The ideal location for a well to monitor the rate at which the mine is refilling and the quality of water in the cavity would be at a lower elevation of the mine cavity, perhaps in the West Submain or 2 West Submain, (drill holes SR14 and SR61 would be well located). However the North Dewatering Well was converted to X1W W with TR35