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,-1 -~ <br />The application specifies that no disturbance is to take place on the south face of the ridge, except <br />in the section where Delta County specified the ridgeline could be lowered by 50 vertical feet. All <br />excavation will take place by pulling material down and to the north. In this scenario, neither <br />allowing, nor preventing mining on the ridge will have any significant effect on erosion of the south <br />slope. DMG believes the areas outside the affected land are not subject to damage from erosion <br />of the south slope caused by this operation. <br />4. Is the geotechnical stability exhibit adequate to address potential off-site impacts to the <br />cliff face and to the underground workings as required by Rule 6.5? <br />Rationale Issue #11 and #12 include comments regarding the destabilization and resulting <br />damage possible due to vibration from equipment acting on nearby underground mine <br />workings and nearby slopes and cliff faces. <br />To address these concerns the applicant submitted a geotechnical evaluation report prepared by <br />Revey Associates, Inc., including modeling scenarios and seismographic vibration studies <br />conducted for the equipment and method of mining proposed. DMG considered citizen comments <br />and conducted an evaluation of the Revey report and follow-up supporting information, submitted <br />by Revey in response to citizen comments received about their initial report. DMG agrees with the <br />conclusions of the Revey report indicating that the potential for this proposed mining operation to <br />exacerbate instability of underground coal mine workings or to exacerbate the natural spalling of <br />rock from the adjacent slopes and cliffs resulting in damage to structures on adjacent lands is <br />essentially non-existent. <br />,i~c~~dd~r d!<rn <br />5. Has the Applicant described how potential impacts to the prevailing hydrologic balance <br />of the Carbon Irrigation Ditch will be minimized as required by Rule 3.1.6? <br />Rationale Issue #21 questions if there is reasonable possibility that Carbon Irrigation Ditch <br />could be contaminated by the mining operation. <br />The applicant has committed to store no hazardous materials on site, but to fuel and service on- <br />site equipment on a daily basis as needed. The application contains a commitment to obtain a <br />Stormwater Discharge Permit and includes specifications for a sediment control system and a <br />drainage control system designed to minimize off site transport of sediment and minimize the <br />amount of upland drainage that contacts the affected area. DMG believes these measures <br />minimize the potential for disturbance to the prevailing hydrologic balance of the affected land and <br />surrounding area (including Carbon Ditch) and to the quality and quantity of water in surface and <br />groundwater systems both during and after the mining operation and during reclamation as <br />required by Rule 3.1.6. <br />DIVISION RECOMMENDATION <br />DMG believes the applicant has demonstrated compliance with the requirements of C.R.S, 34- <br />32.5-115(4), and recommends that the Board approve the Benson Brothers Red Shale Pit <br />application. <br />