2015-05-26_REVISION - C1981041 - Laserfiche WebLink

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Brock Bowles Page 4 May 26, 2015 4.24 Operations In Alluvial Vallev Floors A review was conducted of permit section 2.06.8, the Division's AVF sections of the RN6 Findings document, the operations hydrologic monitoring plan and pertinent sections of the 2010 to 2014 Annual Hydrology Reports. 4.24.1, Scope — No comment 4.24.2 Essential Hydrologic Function- Regarding Rapid Creek AVF, it does not appear surface disturbance has occurred within the AVF. This AVF is outside of the permit area. The source of the water for this AVF is the surface water stream system of Rapid Creek and Cottonwood Creek. No disturbed runoff or mine water is approved to be discharge to Rapid Creek. Rapid Creek appears to have been undermined. The RN6 findings document indicates that subsidence effects are not expected in this area. Given this it does not appear mining should impact the essential hydrologic function of the Rapid Creek AVF. Regarding the Colorado River, The SL8 application indicates that all sediment ponds have been reclaimed at the mine. SCC submitted demonstrations that each pond can be removed prior to conducting reclamation and are included in Appendices 14-2 and 14-3 in the permit. Given this, surface water discharge from the site should not impact the essential hydrologic function of the AVF. Also, the Division has previously found that surface waters which could be and were used to irrigate the non - exempted alluvial valley floor would be diverted from the Highline Canal. Water in the Highline Canal is diverted from the Colorado River approximately one mile upstream of the mine disturbance. The Highline Canal was not projected to be affected by subsidence or by mine discharges. Therefore, the quantity and quality of surface water which supplies the AVF would not be affected by the proposed operations according to the RN6 Findings. Also according to the RN6 findings, Agricultural activities on the lower areas of the lower terraces and floodplain of the Colorado River may be marginally subirrigated by alluvial groundwater. The RN6 findings document states, "The proposed operation would not affect the quantity of flow in the Colorado River stream/alluvial aquifer system. Disposal of coal refuse material in an adjacent area, and the discharge of mine water from underground workings could affect water quality. The Division has assessed the possible effects of these activities and has not identified any significant change in water quality." These findings appear to still apply based on my review. 4.24.3 Protection of Farming and Water Supplies- Rules 4.24.3(1), (2) and (3) do not apply to those lands which were identified in a reclamation plan approved by the State prior to August 3, 1977, according to subpart (4) of this rule. Please see Section 2.06.8 above for details. The majority of the mining disturbance at the site falls within this exception area. The AVF impacted by the UTL was Phase III bond released with SL7. No issues were identified.