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- COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />MEMORANDUM <br />To: Peter Hays <br />From: Tim Cazier, P.E. 'R <br />Date: September 11, 2014 <br />Re: Greeley 35th Ave Pit — Permit No. M -1977 -036 / AM -02 <br />Attachments A & C — Groundwater /ModFlow Results, Preliminary <br />Adequacy Review <br />The Division of Reclamation, Mining and Safety engineering staff (Division) have reviewed <br />Attachments A & C — Groundwater Monitoring and Mitigation Plan, and MODFlow Results, <br />respectively included in the Amendment 2 (AM -2) application received on July 3, 2014 for the <br />Greeley 35th Ave Pit, and prepared by GEI Consultants. <br />The review consisted of comparing the application content with specific requirements of Rule <br />6.4.7 of the Minerals Rules and Regulations of the Colorado Mined Land Reclamation Board for <br />the Extraction of Construction Materials. Any inadequacies are identified below along with <br />suggested actions to correct them. <br />General Comments <br />1. The Division could not find any discussion of the methods, parameters and assumptions <br />used in the MODFlow analyses. Please provide a discussion supporting the selected <br />methods (e.g., modeling reservoirs as high conductivity cells), assumptions (e.g., all <br />boundary conditions, steady state vs. dynamic model), and parameters (e.g., hydraulic <br />conductivity, annual recharge, etc.). <br />2. This area is subject to significant potential mining related impacts on the groundwater <br />elevation and therefore quantity. The results on Figure 3, Potentiometric Surface Present <br />Conditions predict two to four foot elevation differences across open water (primarily to <br />the north and east of the West Cell, but to some extent on the south side as well). Given <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us <br />John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />c�t0 <br />y4, -'s•Yc��'r�d 90 <br />1 876 <br />