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Wallace H. Erickson <br />Division of Reclamation, Mining and Safety <br />Department of Natural Resources <br />December 16, 2013 <br />area underlying the pool could not be determined as there was no available information <br />to make that determination. (Complaint p. S) If an additional study has been conducted to <br />determine the depth and configuration of the reservoir, and its volumetric capacity, <br />please provide the study or studies. The volumetric capacity of the reservoir and quantity <br />of water contained within it would presumably be a material component of any <br />engineering analysis used in determining the relative risk factors associated with its <br />ability to have safe storage and avoid an unintended release of waters. <br />Response to Paragraph 2: <br />At the request of MGC, ground surveys of the tailing impoundment area were conducted <br />in May 2013 to develop accurate area- capacity information for existing conditions at the facility <br />in support of the Initial Formal Technical Evaluation. The surveys included topographic <br />mapping of the interior, low -lying ponded area, which appears to be the area referenced in <br />paragraph 2of the McClure Correspondence. Based upon these data, the average depth of water <br />in the ponded area is less than 2 feet. The Initial Detailed Inspection Report will include the <br />area- capacity data and associated graphs for the dam and impoundment area. <br />3) It refers to the observation of a small excavation in the upstream slope of the <br />embankment, which according to Mr. Mark Perry, Dam Safety Engineer for the Colorado <br />Division of Water Resources, must be appropriately backfilled, compacted and the <br />vegetative cover re- established in accordance with the approved designs. (Report p.3) <br />Has any action been taken by Operator to remedy this matter? Also, we are unsure of the <br />significance of the reference to the approved design. Based upon Mr. Dorey's and Ms. <br />Baldridge's testimony that the facility was never designed for long term storage of water <br />(Complaint -1990 MLRB hearing - Complaint p. 3), any repairs to an approved design <br />may not be relevant other than to repair an area in obvious need. The approved design <br />for the facility in the mining phase and its current use deal with two different concepts. <br />Response to Paragraph 3: <br />The small area referenced in Mr. Perry's report is situated at the crest of the main <br />embankment where the collection pond pump -back line is located. This area will be backfilled, <br />compacted and revegetated in spring 2014 when frost -free conditions allow for completion of <br />those activities. This small disturbed area is not posing any dam safety concerns. <br />4) It refers to the need for the Operator to treat water at the water treatment facil ity, and <br />dispose of untreated waters. Further, untreated waters, sludge, and brine have been <br />taken to the LTF. The report refers to treatment of waters appearing to be a perpetual <br />3 <br />