2012-02-16_REVISION - M2002020 (9)

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Hart Environmental). The reclamation plan will, therefore, not require a court approved water augmentation plan. Mining Impact Mitigation Plan Although impacts and damages are not anticipated, it is the intent of the City of Greeley to operate responsibly and to mitigate damage to wells or structures that is directly attributable to the mining of the 25 Avenue Site. Operations at the 25 Avenue Site are not anticipated to injuriously affect surrounding water rights. If impacts are experienced due to mine dewatering, these affects should be temporary and discontinue once dewatering operations cease or the slurry wall is constructed. However, if dewatering from the proposed amendment area directly affects the ability of surrounding wells to pump a full supply of water in accordance with their permitted uses, the City of Greeley will take all necessary actions to remedy the affects to the extent they were directly caused by operations at the site. Mitigation measures may include, but are not limited to: 1. Modify existing wells to operate under lower groundwater conditions. This would include re- drilling existing wells to deeper depths or lowering the pumps. All work would be done at the City of Greeley's expense with the exception of replacing equipment that was non - functional prior to mining. 2. If existing wells cannot be repaired, the applicant will drill a new well for the owner to replace the damaged well. The new well will produce water of the same quantity and quality to support the historic use. 3. Provide an alternative source of water to support the historic well water use during mine dewatering. Potential Reclamation Impacts Once the slurry wall is constructed around the mining pit (SW Ponds) potential impacts to surrounding wells from pit dewatering will cease. When the SE and NE ponds are mostly backfilled, impacts to the adjacent groundwater table from pond surface evaporative losses will be minimized. For groundwater pond surface area that remains un- backfilled, evaporative losses will be account for with a Greeley West Pit pre -1981 exposed groundwater credit of 45.5 acres (November 1, 2001, Office of the State Engineer to Hart Environmental). Therefore, final reclamation of the amendment area does not require complete backfilling of the existing NE Pond and SE Pond or augmentation. The lined reservoir will influence alluvial groundwater flow near the slurry wall, but these influences are anticipated to be very localized. Specific alluvial groundwater conditions at the 25 Avenue Site and proposed amendment area are limited. From monitoring wells on the site, alluvial groundwater appears to range from 10 to 15 feet below the ground surface. For other alluvial groundwater conditions, baseline conditions would be expected to reflect typical river and stream alluvial groundwater regimes along the Cache la Poudre River. These groundwater regimes generally exhibit a relatively high transmissivity and low gradient. Groundwater flow is regularly in the same direction as, and slightly towards, the river (see Exhibit C -4, Water Greeley 25 "' Avenue Site DRMS 112 Permit Amendment Application Page 20