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AIMM 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 />May 21, 2015 <br />Connie Davis <br />Aggregate Industries - WCR, Inc. <br />1687 Cole Blvd., Ste. 300 <br />Golden, CO 80401 <br />Re: Hazeltine Mine, DRMS Permit No. M-2004-031 <br />Technical Revision No. 4 (TR -04) <br />Preliminary Adequacy Review <br />Dear Ms. Davis: <br />On May 21, 2015, the Division of Reclamation, Mining and Safety (Division) received Technical <br />Revision No. 4 (TR -04) for the above referenced site. The decision date for TR -04 is June 22, 2015. <br />The Division has reviewed TR -04 and has the following comments and questions: <br />1) The proposed location of the two 18 -inch CMP pipes is in close proximity to HZMW-2. The <br />Division has reviewed the groundwater monitoring data from HZMW-2. Prior to the installation of <br />the slurry wall, the groundwater elevation in HZMW-2 was approximately 5035 feet. Technical <br />Revision No. 2 (TR -02) stated that the lowest land surface elevation of the Orr property was <br />5038.50 feet. The proposed invert elevation of the two pipes is 5040.78 feet. The proposed invert <br />elevation of the two pipes is approximately 5 feet above the pre -slurry wall groundwater elevation <br />and approximately 2 feet above the lowest elevation of the Orr property. The Division believes <br />that the proposed invert elevation of the two pipes will not minimize the impacts to the prevailing <br />hydrologic balance and will not resolve the impacts to the adjacent Orr property. The Division <br />believes that the groundwater elevation must be approximately 2 feet below the land surface to <br />effectively drain the Orr property. Please revise the temporary plan to lower the water elevation to <br />2 feet below the lowest point on the Orr property, or please explain how the invert elevation <br />proposed in TR -04 will effectively control the groundwater elevation. <br />2) How will the applicant prevent the discharge from the two pipes from eroding the reclaimed pit <br />slopes? <br />3) Please commit to locating and rehabilitating wells HZMW-2, HZMW-6, HZMW-11, and HZMW- <br />12, within 45 days of the commencement of the Temporary Groundwater Mounding Mitigation <br />Plan. If any wells cannot be located or rehabilitated please commit to replacing the well(s) within <br />60 days of the commencement of the temporary plan. <br />�w of cow <br />Fe <br />I VI 0 <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. Hickentooper, Governor I Mike King, Executive Director I Virginia Brannon, Director *'� 1876 <br />