2015-04-23_REVISION - C1981014 (2)

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George V. Patterson, Energy Fuels Coal, Inc. Page 7 April 23, 2015 Items 1) c) ii) and iii) are resolved. The clarification of elevations at MWNW is helpful. The discussion of MW 16 in the March 2015 Weaver Analysis and in the March 16, 2015 letter are likewise informative. Item 1) c) i) has not yet been addressed to the Division's satisfaction. The Division does not agree with EFCI's assertion that the currently available data is sufficient to make a finding as to the impacts of mining on groundwater quantity. The mine inflow data reported to the Division in AHRs: • Supports the conclusion that mine inflow volumes generally decreased between 1985 and 2000. • (As previously noted), shows that the 330 Acre feet per year estimate from page 2.05.6- 41 was an overestimate of mine inflow volumes. The above facts are not in dispute. Furthermore, the Division does not seek to denigrate the effort made by EFCI to collect mine inflow data or the effort of BBA to use the available data to make projections of mine flooding. Nevertheless the value of the data, and of any projections made using it, is limited for the following reasons: • Firstly, according to the explanatory text in the AHRs, "the estimated mine inflow into accessible areas of the Southfield Mine during the reporting period... is based on the combined total of water pumped within the mine and measured at inflow and seep locations ", (1998 AHR). The March 2015 BBA letter clarified that within the mine workings some of the inflow was captured at source and pumped to a sump, then from the sump to the western part of the mine (and was metered); and some of the inflow was allowed to gravity drain to the western part of the mine (per the AHRs this volume was estimated by observations made on 2 days per year). Clearly the accuracy and precision of this approach is limited, both by the difficulty of estimating a volume by observation, and by the considerable variability of inflows from month to month (which is well illustrated by a plot of the monthly inflow data provided in AHRs covering the period between 1985 and 1995, see figure 1). • Secondly, and more significantly, the area being monitored for inflow was reduced as mining progressed. "Less area of the mine continues to be accessible for monitoring inflows since mining is primarily in the retreat process. Because of this, the measured inflows represent a progressively smaller percentage of the actual total inflows ", (1998 AHR).