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AMERICAN <br />GYPSUM <br />Travis Marshall, Environmental Protection Specialist <br />CO Department of Natural Resources <br />Division of Reclamation, Mining and Safety (DRMS) <br />Minerals Program, Grand Junction Field Office <br />101 S. 3rd St., Suite 301, Grand Junction, CO 81501 <br />April 14, 2017 <br />RE: Request for Technical Revision to Mine Reclamation Plan <br />Travis, <br />The State of Colorado is requesting that American Gypsum design and install sediment <br />controls in accordance with good engineering practices for basin M001. This request <br />from the Colorado Department of Public Health and Environment, (CDPHE) is part of an <br />expedited settlement agreement resulting from a May 2016 inspection. <br />The current sediment control structures for basin M001 near the mine entrance were not <br />selected, designed, installed, implemented, and maintained in accordance with good <br />engineering hydrologic and pollution control practices as required by Part (I.G) of the <br />Colorado General Stormwater Permit. Completion of this project will provide <br />compliance with Part I.G. <br />The State of Colorado classifies stormwater that comes into contact with the ore <br />stockpile, or stormwater that comingles with stockpile runoff, as process water. The <br />Eagle Gypsum mine is not permitted to discharge process water. Process water must be <br />contained and allowed to percolate into the aquifer and/or evaporate as opposed to being <br />discharged into Trail Gulch. For this reason a stormwater containment structure must be <br />designed, built, and maintained. <br />Additionally, the existing haul road crossing over Trail Gulch was not properly designed <br />to allow for the handling of the volume of water generated by a 1 in 25 year storm event <br />in the Trail Gulch watershed which is the required state minimum. In addition to being <br />undersized, the culvert under the mine haul road is also collapsing and must be replaced. <br />This project will design and build two new stormwater sediment control structures at the <br />entrance to the mine and one stormwater containment structure for stockpile stormwater. <br />This project will also remove and replace the existing roadway that crosses the Trail <br />Gulch drainage in order to accommodate the two properly designed sediment control <br />structures and one stormwater containment structure. These changes will effectively <br />manage stormwater, snowmelt, potential process water, and sediment at the most publicly <br />visible discharge points on American Gypsum mine property. <br />American Gypsum Company • 740 Highway 6 - P.O. Box 980 • Gypsum, Colorado 81637 • p.970-524-8103 • f.970-524-8140 <br />