2023-05-25_PERMIT FILE - M2022048 (10)

Home Browse Search

Exhibit G Water Information (cont) as 2 . 5 feet on the west end of this strip to approximately 1 foot at the eastern corner of the slurry wall on the east . It also indicates that if needed, a simple perforated pipe, 12 inches in diameter would be capable of regulating the groundwater to his- toric elevations . In this mitigation trigger plan, the trigger limits will be set at as a two (2) foot plus or minus change over a 3-month running average. Because the average groundwater levels are already close to 4 feet from the surface in the southeast corner of Phases 1, limiting the maximum rise before mitigation to 4 . 0 feet is too restrictive. The data collected to date shows the historic high to low swing is much as 1 . 44 feet up or down- ward possibly due to outside impacts such as, drought, storm events or decreased irrigation. A 2 foot increase over 3 month running averages will keep the minimum depth to below the 24 inches cover level required by the SEO exposed ground water requirements . As for the shadowing effect of the slurry walls, we do not expect this to be a problem where the slurry walls are in close proxim- ity to a flowing water body like the irrigation return flow ditch that bisects the mine site north to south and the South Platte River along the east and north sides. The Groundwater Model confirms that any shadowing or mounding along the river will only affect the property owned by L.G. Everist and will not cross over the river. If during the course of mining or reclamation complaints from the well owner or adjacent property owners are received by the permittee, the permittee will commence an evaluation and investigation, including providing replacement water to the well owner if necessary, within 48 hours . The method used to mitigate groundwater mounding may include a ground water drain along the Abbett property to maintain ground water elevation to the average level measured prior to installation of the slurry wall liner. This drain may be in the form of a ditch or a buried perforated pipe as described in the GWM. DRMS shall be notified within two business days of the complaint and the proposed initial steps for the evaluation of the complaint . A written report will be submit- ted to DRMS within 30 days detailing the information collected during the investigation of the complaint, and proposed mitiga- tion activity, if required. Post Reclamation Any slight groundwater mounding and shadowing associated with the slurry wall sealed portions of the pit are not antici- pated to produce any adverse impacts to adjacent properties . Potential groundwater mounding around the mine will be mitigated by the South Platte River, road corridor and the single irriga- L.G. EVERIST, INC. -WEST FARM RESERVOIRS May 2023 31