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eventual release of the runoff from the impoundments' spillways. • The highest sediment yields predicted under postmining conditions were 0.045 tons (005 Gulch) and 0.232 tons (006 Culch) using the 100-year, 24-hour storm (2.6 inches). These yields translate to less than one pound of sediment per acre produced by more than two inches of rainfall in either the 005 or 006 Gulch basins. Both the 006 and proposed 005 ponds, proposed to be left as part of the postmining landscape (permanent impoundments), will contain sufficient sediment storage capacity to handle even the highest sediment yields generated from large precipitation events. Assumptions used to model the postmining Landscapes, vegetation, and soils involved characterizing conditions in these watersheds as they will exist after sufficient time has passed since final reclamation to allow Peabody to apply for bond release. Reconstructed drainage channels in each watershed will be designed to adequately convey more than the peak discharges predicted by SEDIMOT 11 without causing additional contributions of sediment, and to ensure the long-term stability of the reconstructed channels. Both the 005 and 006 ponds will be designed and constructed to be permanent impoundments, and will be engineered to adequately handle the runoff volumes (100-year, 24-hour) predicted under • the postmining scenario. SEDIMOT II predicted sediment concentrations for the inflow to the ponds that are less than the exceedence limits required by Peabody's NPDES permit for point discharges (pond outf alls). Finally, the ponds proposed as permanent impoundments will be engineered to adequately contain increased sediment yields (via designed sediment storage) predicted by SEDI MOT II assuming postmining conditions. The impacts of runoff from reclaimed areas on streamf low will be long-term (after bond release), but proposed permanent impoundments and reconstructed stream channels will result in these impacts being minimal and insignificant. Effects of Runoff from Reclaimed Areas on Quality of Streamf low. Runoff from reclaimed areas will occur either as snowmelt during the spring and early summer, or as runoff from summer thunderstorms. Average annual snowmelt has been estimated to be as high as 1.3 inches in Hubberson Gulch (see Tab 7, "S nowmelt"). The highest water yield from the partially reclaimed watershed (80 percent) above Pond 006 was predicted using SEDIMOT II to be .2 inches (100-year, 24-hour storm). These calculations indicate that snowmelt could produce as much as six times the runoff produced from frontal or surnner thunderstorms. Table 17-28 presents comparisons of same day flow measurements conducted • at Sites FC1 (lower Hubberson below the 006 Gulch) and SG6 (006 Culch). The table 74