2023-05-25_PERMIT FILE - M2022048 (18)

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+ Exhibit G Water Information (cont) inches in diameter would be capable of regulatingns the groundwater to historic elevations . E. G . Everist, Vne' s . experienee en ether mines in the Seut-hl Platte River valley indieates that greundwater levels e fluetuate as mueh as ? . G+ feet depending en the seasen . The data eelleeted eenfifes that the West Farm Reserveirs site is within a few inehes ems-that—numb In a nefsal this mitigation trigger plan, the trigger limits willwou-14 be set at as a twoh�ee (20) 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 downward possibly due to outside impacts such as, drought, storm events or decreased irrigation . A 2foot increase over 3 month running averages will keep the minimum depth to below the 24 inches cover level required by the SEO exposed around water requirements . Realistieally, in this ease the trigger number sheuld be based en a 3 feet ehange determined by a line that appreximates an-up-a aetivitres . 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 proximity 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. The mining eperatien will have minimal effeet en the Seuth evapefatien and water uses asseeiate4 with mining. The depl-ne*�Ve* te the Seuth Platte will he mitigated thou a temperary Substitu Water Supply Plan (as required and appreved by the 9ivi Water Reseurees) te prevent injury te the vested sen±er water lined reserveirs that will net he hydraulieally eenneete Seuth Platte River er any alluvial aquifer. The reservei will he sealed pfief te mining, thereby eliminatiog-ON site 4ewatering. This will alse eliminate , r minimize the pessibility ef any adverse impaets te the single nearby alluvial 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 31