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monitoring show that impacts to the ground water aquifers are preclud i~ng its use, Peabody <br />• will provide alternate water sources of comparable quantity and quality. <br />Also discussed in Attachment 16-1 of Tab 16 are the 11 surface water rights that could be <br />potentially affected by pit inflow drawdowns. An augmentation plan, which utilizes the <br />114 acre foot consumptive use right Peabody has with the Highline Canal, has been <br />developed to mitigate the potential 26 acre foot impact to surface water right users from <br />pit inflow drawdowns. The reader is referred to Attachment 16-1 to Tab 16 for a more <br />detailed description of the quantities of water to be augmented, the associated <br />calculations and the plan. The impacts to surface water users will be minimal and of <br />little significance, as an augmentation plan has been developed that will insure that <br />those quantities lost will be replaced. <br />Removal of Wells and Ponds by Mining. No surface or ground water rights have been <br />identified within the Nucla permit revision boundary for the Nucla East mining area (refer <br />to Figure 2 of Attachment 16-1 to Tab 16). Thus there will be no direct impact from the <br />proposed mining plan on any local water-righted facilities. <br /> Impact of Replaced Spoil Material on Cround Water Flow and Recharge Capacity. The pits <br /> will remain open only until the coal has been removed. Following the short-term impacts <br /> (water level declines) on the ground water system as a result of pumpage of ground water <br /> inflow to the pits, a potential long-term impact to the local ground water flow is the <br />period of time necessary for resaturation of the spoil material and reestablishment of a <br />flow gradient. <br />A wide range in permeabilities for spoil material can occur, depending on how it is <br />placed. Rahn (1976) reported that spoil material replaced using a dragline in one <br />instance and a scraper in another, yielded hydraulic conductivities of 35.3 ft/day and 0.4 <br />ft/day, respectively. Van Voa st and Hedges (1975) concluded that greater porosities and <br />hydraulic conductivities will result from volume changes (approximately one-fourth <br />greater) between spoil material in its original compacted, stratified state, and in its <br />rearranged state following replacement, regardless of the method of placement used. <br />Spoil material at the Nucla and Nucla East mining areas Hill be replaced using several <br />• techniques. Some spoil movement at either mining area will be accomplished using cast <br />blasting. The remaining mining at the Nucla mining area will be conducted with scrapers <br />17-27 Revised 04/11/88 <br />