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Those ponds that collect flow from smaller, ephemeral basins (Ponds 002, 003, 004 and 005) <br />have not discharged to date. If they were to discharge a measurable quantity of water, <br />some downstream channel incision would be expected in the immediate vicinity of the dam. <br />the impacts of the sediment ponds on the channel characteristics will last through bond <br />release, and will be of minimal significance. Following the removal of the sediment ponds <br />at bond release, there will be certain short term impacts to the channel reaches, <br />particularly below the location of the removed structures. Sediment loads will <br />temporarily increase as the active channel widens in response to the increased runoff <br />potential. Channel bank vegetation that has encroached over time in the immediate <br />downstream reach, and prompt reclamation (topsoil reestablishment and revegetation) of the <br />removed pond structure will provide some stability during this short term active channel <br />readjustment period. The frequency of the larger runoff events (due to snowmelt and <br />summer thunderstorms) will dictate how rapidly the channels reestablish stable conditions. <br />An alluvial valley floor (AVF) analysis of both Tuttle and Calamity Draws was performed <br />and the results of the analyses are presented in Tab 16. The analyses determined that <br />• Tuttle and Calamity Draws were not AVF's. Significant observations made in the analysis <br />were that the areas of potential subirrigation were very limited in extent, and that no <br />historic or present usage of water from the main channels in either draws for flood <br />irrigation purposes has been identified. The incised nature of the main channels in both <br />draws largely precludes any practical attempts at flood irrigation using only gravity <br />feed. Usage of water fran the main channels in either Tuttle or Calamity Draws would only <br />be feasible if pumps were employed. <br />Potential impacts (water quantity) of the sediment ponds on downstream users along both <br />draws will involve possible reductions in flow due to impounded water. Tab 16 presents a <br />discussion on water rights in the vicinity of both mining areas (Nucla Mine and Nucla <br />East), wfiich includes those surface water rights located along both draws below the seven <br />sediment structures. Peabody currently has rights to a sufficient quantity of water (27 <br />shares in the Highline Ditch) to supply all uses associated with the mining activities <br />conducted in both areas (see Tab 16), plus an additional quantity of water that can be <br />used to mitigate any impact to downstream users. A plan has been developed for augmenting <br />any water right (ground or surface) that may prove to be impacted by mining, and this plan <br />• has been included as Attachment 16-1 of Tab 16. Because of the quant i~ty of water righted <br />to Peabody, and the developed augmentation plan to be implemented should water rights be <br />17-77 Revised 04/11/88 <br />