2018-06-11_PERMIT FILE - M2008017 (11)

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Mr. Scott Response to Preliminary Review of a 112 Construction Materials Reclamation Permit Amendment Package, Derr Pit, Permit M2008-017 Page 2 EXHIBIT D - Mining Plan (Rule 6.4.4): The fourth paragraph of Exhibit D states that setbacks of less than 200' may be used for structures with existing surface use agreements/damage waiver agreements. Please specify in detail what structures/agreements are being referred to (this information may also be provided as part of Exhibit S). DRMS notes that prior damage waiver agreements have been obtained from the City of Greeley, DCP Midstream, and Loloff Construction as provided in Exhibit S. DRMS considers that the entire proposed permit area is potentially affected area at this time. No evidence has been provided that any structure owners (other than the three listed above) inside, or within 200', of the existing or proposed permit area have been provided with damage waiver agreements. This demonstration is required by DRMS prior to acceptance of a geotechnical stability exhibit such as the one provided for the first four phases of the proposed operation (See comments for Exhibit S for further information). DRMS cannot approve the permit amendment unless/until all structure owners within and within 200' of the proposed permit area are provided with damage waiver agreements. Response: The existing surface use/damage waiver agreements that have been obtained and the associated structures are listed in Exhibit S along with a listing of other damage waiver agreements that are being pursued to structure owners within 200 feet of the affected area, and the structures associated with those agreements. See the attached updated Exhibit S. EXHIBIT E - Reclamation Plan (Rule 6.4.5): If the proposed lined reservoirs lie within the flood-plain,_the operator will need to install engineered inlet/outlet structures to protect the integrity of the liner during a flood event. If pumping/water control features associated with the developed water resource will be constructed prior to release of the permit as proposed here, the permittee will be required to submit a detailed engineered design for these features either as part of this amendment or through a Technical Revision prior to construction. Cost for construction of these features will need to be included in the reclamation bond. These requirements also apply to the required engineered flood control structures, and installation of a perimeter drain/French drain to control groundwater levels around areas enclosed by the proposed slurry walls. Please acknowledge. Response: The north cell reservoir is outside the floodplain. The south cell reservoir is in the very outer fringe of the floodplain. Because the south cell reservoir is more than 2000 feet away from the river channel to the south, the site is level, and there is no above grade embankment around the reservoir, a side channel spillway is not required, and in fact could not be constructed, to convey flows into the pit. Any flood flow that enters the pit will be contained there and will not exit the pit after the flood event ends. Flood flows will not be concentrated and if they enter the reservoir will do so in a sheet flow condition. It is anticipated that minimal to no damage to the reservoir side slopes will occur. Some minor erosion may occur on the side slopes. No damage to the slurry wall liner is anticipated as it is set back from the reservoir side slopes. M 305 Denver Avenue—Suite D•Fort Lupton CO 80621 • Ph: 303-857-6222 •Fax: 303-857-6224