2014-03-26_PERMIT FILE - M2013064

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AWLS, LLC Fort Collins, Colorado, USA March 23, 2014 Mr. Peter Hays Division of Reclamation, Mining and Safety 1313 Sherman Street, Suite 215 Denver, Colorado 80203 RE: Response to DRMS Second Adequacy Review Comments & Stability Analysis DRMS Permit M- 2013 -064 Varra Coulson Mine — Greeley, CO Dear Mr. Hays: I have reviewed the comments provided by the Colorado Division of Reclamation, Mining and Safety (DRMS) in the February 10, 2014, letter to Varra Companies, Inc. Below are my responses to the comments which require further clarification. 20. Plate 2 of the January 13, 2014, AWES, LLC (AWES) response submittal does not depict the shadow or mounding effects claimed by DRMS. The variations in water level referenced by DRMS were from inside the barrier wall, which would be the lined pond. The water table contours outside of the barrier wall do not depict water level changes of more than two feet at any location. The water level simulated within the barrier wall was modeled at 4627 feet (4027 was a typographical error). As the proposed weir elevation is on the order of 4614, an additional model simulation was performed with a constant head boundary (water level inside the barrier wall) of 4611. Plate 1 (Attachment A) depicts the location of the barrier wall and constant head boundary inside the wall. Plate 2, depicts the model output. In order to evaluate water level changes outside of the barrier wall Plate 2 in this submittal is compared to Plate 1 of the January submittal (Attachment A). A review of Plate 2 shows that water level contours outside of the barrier wall are unaffected by the constant head changes (water level changes) inside the barrier wall. The model runs support a conclusion that water within the pond is not in hydraulic connection with the surrounding aquifer. The model simulation(s) were ran without influence of the Durham mine dewatering or the Greeley #3 Ditch recharge. A conclusion that the cessation of the Durham mine dewatering or relocation of the ditch will exacerbate barrier wall influences is not consistent with the solutions provided. The water level changes associated with the barrier wall are so minor that any hydraulic influences will mask the effects of the barrier wall. 14 oil filar ( 4 111-1_ 14 1-11 4 4 11in%. 4 4 `I ►! 1 1 /1; ► 04 944 !