2012-02-16_REVISION - M2002020 (9)

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Resource Map). The alluvial groundwater elevation and flow direction in these systems are typically influenced by fluctuations in river flow, direct precipitation and infiltration, agricultural irrigation, and withdrawals from water wells. Mounding and shadowing refer to a slightly higher or lower normal groundwater elevation, respectively, and can be caused by obstructions to the natural alluvial groundwater flow regime. Once the slurry wall is complete, and based on the assumed groundwater flow regime, mounding is anticipated west and southwest, or upgradient, of the slurry wall and shadowing is expected east and northeast, or downgradient of the reservoir. These groundwater elevation effects are most pronounced immediately adjacent to the slurry wall, with groundwater returning to normal elevations over relatively short distances away from the slurry wall. Upgradient (west and south) of the 25 Avenue Site, properties are primarily owned by additional mining operations and semi -rural residences and commercial businesses. The residence and commercial businesses are at least 200 feet from the proposed slurry wall. Shadowing impacts downgradient of the 25 Avenue Site slurry wall are not likely since the Cache la Poudre River is immediately north of the site and additional mining operations or reclaimed mining properties are to the east. Groundwater mounding and shadowing effects are not expected to occur beyond, nor impact, these adjacent properties and features. Therefore, impacts and damages to adjacent properties from installation of the slurry wall are not anticipated. Reclamation 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 and reclamation of the 25 Avenue Site. Although not anticipated, if installation of the slurry wall creates injury to surrounding wells, the applicant will take all necessary actions to remedy the injury. If water levels are dropping in adjacent wells, due to shadowing from installation of the slurry wall at the 25 Avenue Site, such that well owners historic water production may be injured, 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. Additionally, if it is determined that installation of the slurry wall creates mounding or shadowing impacts to surrounding structures or water resources, the applicant will take Greeley 25` Avenue Site DRMS 112 Permit Amendment Application Page 21