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CERTIFIED MAIL <br />RETURN RECEIPT 7012 2920 0000 9187 1025 <br />May 18, 2015 <br />Mr. Tyler O'Donnell <br />Division of Reclamation Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />Re: Permit Number M-2004-031— Hazeltine Mine <br />Technical Revision Request — Temporary Mitigation Plan <br />Dear Tyler: <br />EDEIVED <br />MAY 2 12015 <br />DIVISION OF RECUWATION <br />MINING AND SAFETY <br />Ak <br />� AGGREGATE <br />INDUSTRIES <br />Aggregate Industries (Al) submits this letter together with the enclosures referenced <br />herein and a check in the amount of $216 as a proposed technical revision to the <br />Hazeltine Mine permit. This revision is submitted as the temporary mitigation plan <br />required under MLRB Board Order MV -2015-003. <br />Al proposes to install two (2) 18 -inch diameter CMP pipes at the location noted on the <br />enclosed aerial photo. The pipes will be installed 1.4 +/- feet below the existing water <br />elevation, which has been surveyed in at 5041.95 feet. The pipe inlets will be set at <br />approximately 5040.78 feet elevation. Slide drain gates that provide for adjustment of <br />water flow will be installed at the inlets. The pipes will be installed through the slurry <br />wall with a 4.2% +/- slope from the inlet to an outlet elevation of approximately 5038.2 <br />feet. Water will discharge into the mined pit and then into existing settling ponds and <br />dewatering trenches in the pit floor. Water will be pumped out of the pit through the <br />existing discharge system, which is an 88 hp pump discharge through a 12 -inch diameter <br />pipe along the pit floor, up the slope and to an existing, approved discharge point on the <br />west boundary of the site to the South Platte River. <br />Water will be gravity fed through the pipes. Ultimately, the drain gates will be set to <br />adjust the water drainage to establish pre -mining conditions on the neighboring Orr <br />property; however, since the intent of this temporary plan is to draw down water levels <br />from the adjacent Orr property as quickly as possible, the drain gates will be set to <br />Aggregate Industries <br />West Central Region, Inc. <br />1687 Cole Boulevard, Suite 300 <br />Golden, CO 80401 <br />Telephone: 303-985-1070 <br />An Equal Opportunity Employer <br />