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established vegetative regime which supports these land uses is a perennial pastureland. This approved vegetative type differs considerably from the pre-mining vegetation communities which were oak brush herbaceous and sagebrush herbaceous. Reclamation and seeding of the disturbed areas contributing runoff and sediment to impoundments 001 and 002 occurred in late September and early October 1987. The seed mixture used is the seed mixture specified in TR-51 and listed in Table 2.05.10 of the H-G Coal Company Technical Permit Revision Application - TR-62. Monitoring of revegetation success has been conducted periodically since 1987. Vegetative productivity data collected from reclaimed areas in 1990 indicated successful establishment of revegetation according to the criteria for evaluating Phase II bond release. Field revegetative success monitoring conducted by HGCC in 1993, as reported to the Division in the Hayden Gulch Mine - /993 Anm~al Report, indicated an improvement in revegetation over the 1990 vegetation sampling and overall excellent revegetative success. The 1993 data demonstrated that: • The average percent cover for those areas reclaimed in 1987 was 62% with a litter cover of 35%, which corresponds to a range cover condition rating of 97%. • The 62% average cover for those areas reclaimed in 1987 was greater than the weighted mean for the reference areas (59.7%). • The existing vegetative cover is primarily perennial grasses (herbaceous), with some sagebrush/mountain brush species, and the vegetative community can be classified as dryland pasture or rangeland. 3.0 SEDIMENTOLOGY DEMONSTRATION The methodology HGCC utilized in this demonstration incorporated a comparison of the pond invert elevation. A significant increase in the invert elevation would be an indication of sediment accumulation in the pond. HGCC conducted a sediment survey of ponds 001 and 002 during May, 1996. The current pond invert elevation for each pond was compared against the as-built pond survey, conducted August, 1992, invert elevation. Figure 2, Ponds 001 and 002 Stage Storage (1992) and Figure 3, Ponds 001 and 002 1996 Sediment Survey and Stage Storage, displays the surveyed configuration and invert elevations for each pond for 1992 and 1996, respectively. The survey datum was utilized to generate stage storage-area curves and available storage capacity volumes for each pond for both years. Table 1, Pond Invert Elevation Comparison, summarizes the pond's invert elevations from the August, 1992 and May, 1996 surveys. File c:\87Tyhax24emovel.dem fi/2B/96 2