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9 <br />as adjacent, undisturbed areas). However, there were no bare areas of sieniticant extent, and even in the <br />scattered locations where cheatgrass was dominant, the extent of cover appeared to be sufficient to <br />control erosion. Due to the season, forb species, including the noxious weed species were less apparent <br />than they would have been during the growing season. The following excerpt from a Division inspection <br />conducted on September 24, 1997, provides a more detailed description of the revegetated community. <br />Vegetation growth on reclaimed areas seeded in 1988 remains green and lush due to the <br />ample late summer precipitation this year. During walk-through of the revegetation, I 1 <br />cool season grasses, 3 warm season grasses, 3 shrub species, and 2 perennial forb species <br />were observed. The visual dominants are the native shrub, fourwing saltbush, and the <br />native cool season bunchgrass, bluebunch wheatgrass. The vegetation has effectively <br />stabilized the site, with essentially no erosion apparent on the reclaimed slopes. There are <br />scattered patches of the noxious species Russian knapweed, white top, and field <br />bindweed, but the operator has conducted weed control efforts in compliance with <br />Division guidelines, and the noxious species represent a very minor component of the <br />vegetation biomass. <br />In summary, based on the bond release inspection, previous site inspections, and evaluation of reports <br />included in the bond release application, it is the Division's judgement that revegetation has been <br />successful, and that compliance with the applicable success standard has been demonstrated for each of <br />the final two years of the liability period. <br />Although there was no species diversity or species composition standard required by the approved permit, <br />a relatively diverse assemblage of native shrubs and grasses supportive of the wildlife habitat post-mining <br />land use has been established on the reclaimed area. <br />Reestablishment of essential hydrologic functions on Alluvial Valley Floors <br />The Ward Creek and Williams Creek valleys within and adjacent to the permit area were determined to <br />be alluvial valley floors, based on geomorphic criteria and the existence of extensive flood imgated <br />agricultural, primarily livestock pasture, hayland, and orchards. The essential hydrologic functions <br />associated with the alluvial valley floor were identified as the integrity of the irrigation system and the <br />ability of the surface water system to supply sufficient irrigation water of suitable quality to support the <br />irrigated farming activities. The probable hydrologic consequences study included in the permit <br />document concluded that impacts to stream flow and quality of water used for irrigation on the alluvial <br />valley floor would be insignificant, and hydrologic monitoring data from stream sites and alluvial well <br />locations upstream and downstream of mining operations has supported those projections. <br />The integrity of the irrigation systems and farming operations on alluvial valley floor areas located over <br />the underground workings could potentially be affected by surface effects of subsidence, such as <br />depressions, swells, or cracks. Based on the fact that coal extraction was limited to 50-55%, surface <br />effects of subsidence were anticipated to be minor, and capable of remedy. The operator committed <br />