2018-10-16_PERMIT FILE - M2018039 (2)

Home Browse Search

Mr. Jared Ebert RE: Lamb Lakes Site M-2018-039 October 15, 2018 Dewatering also has the potential to impact the Fort Collins Irrigation Canal Ditch. As described in the Hydrogeologic Evaluation (Attachment B), impacts to the Larimer and Weld Irrigation Ditch from site dewatering is unlikely due to the presence of the Cache la Poudre River. The river is assumed to be in direct hydraulic connection with the alluvial aquifer and dewatering impacts are not expected to extend east of the river. To minimize impacts to Fort Collins Irrigation Canal Ditch irrigation water, dewatering operations shall not be performed during the irrigation season when irrigation flows could be affected by pit dewatering. The irrigation season is generally considered to be May through September, but the applicant will coordinate the construction schedule with the ditch owner. Agreements are also being discussed with the ditch owner (Arthur Ditch Company) to protect the owner from potential impacts. Although operations at the Lamb Lakes site are not anticipated to injuriously affect surrounding water rights, it is the operator's intent to operate responsibly and to mitigate damage to wells or structures that is directly attributable to mining or reclamation. A groundwater monitoring program shall be implemented to establish baseline groundwater conditions and to evaluate changes in groundwater elevation and gradient during lake dewatering and slurry wall construction. If impacts are experienced due to lake dewatering, these affects should be temporary and discontinue once dewatering operations cease and/or the slurry walls are constructed. However, if dewatering from the proposed permit area directly affects the ability of surrounding wells to pump, or canals/ditches to deliver, a full supply of water in accordance with their permitted uses, the operator 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: I. 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 operator'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 or canal/ditch water use during mine dewatering. 6. Significant groundwater mounding and shadowing is not anticipated outside the Lamb Lakes property. The Hydrogeologic Evaluation (Attachment B) describes potential affects from slurry wall construction at the site and impacts from mounding and shadowing. Due to the localized nature of mounding and shadowing and the adjacent land forms and uses, impacts from mounding and shadowing are not expected. However, a groundwater monitoring program shall be implemented to establish baseline groundwater conditions and to evaluate changes in groundwater elevation and gradient following slurry wall installation. Page 3 of 7