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~" r~-~~ <br />/' <br />CORDILLERAN <br />826 21 '/ Road <br />Grand Junction, CO 81505 <br />T: 970.263.7800 <br />F: 970.263.7456 <br />9. Please indicate what precipitation event the drainage control features were designed for. <br />Please indicate what measures will be implemented at the down gradient end of the <br />upland diversion ditch to dissipate flows and ensure no off-site erosion occurs from this <br />concentrated discharge point. Please show energy dissipaters and erosion control <br />structures on the permit maps. <br />The runoff diversion ditch was sized to convey runoff from a 100-year, 24-hour, 2.8"storm <br />event. The uphill run on diversion ditch will be extended downhill past the extent of the mine to <br />convey diverted flows down the natural hillside. These ditches will be lined with rock or turf <br />reinforcement mat (TRM) for erosional stability. Small rock-lined energy dissipation basins, each <br />measuring approximately 10' x 10' x 3' deep, will be installed at the base of the hillside. Please <br />refer to the enclosed maps for locations of these features. <br />Exhibit D -Reclamation Plan <br />11. Please revise the slope configuration to 2H:iV which is the maximum considered to be <br />traversed by livestock (See Rule 3.1.10(3)). If a final slope grade of 2H:1V is committed <br />to, the submitted geotechnical stability report is acceptable. <br />The final slope grade will be 2H:1 V The appropriate revisions have been made to the Permit <br />Application. <br />12. Please see No. 11, above. <br />16. If the flat portion of the mined out area is to be used as an equipment staging area for <br />the landowner, it is not necessary to include revegetation plans, as this proposed post- <br />mining land use is reasonably assured, given the current and foreseeable future oil and <br />gas production activity in that area. In the event the flat is not used as a drilling pad, the <br />staging area reclamation requirements are acceptable. <br />The flat portion of the mined out area will be used as a graveled staging area for the landowner, <br />or possibly as a gas well drilling pad. The appropriate reclamation requirements will be adhered <br />to for either use. <br />18. Please revise the reclamation cost estimate to account for any revisions made in <br />response to the comments above and clarify the slope grading includes cut and fill of the <br />benches to create the final slope. <br />The reclamation cost estimate has been revised to include revegetation of the 3.0 acres of <br />slopes. The remaining flat portion of the property will be used as a graveled staging area, or <br />possibly as a gas well drilling pad. The slope grading has been clarified to include cut and fill of <br />the benches to create the final 2H:1 V slope. <br />Cordilleran Compliance Services, Inc. <br />Grand Junction, CO • Denver, CO • Casper, VVY • Laramie, WY • Lander, VVY <br />Environmental Consulting Engineers and Scientists <br />