_INSPECTION - C1982057 (67) - Laserfiche WebLink

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• Most of the culverts and outlet sediment control structures along Road "J" are in need of maintenance, due to erosion and siltation from the recent heavy rains. • The southern-most corner segment of former Road "K", which was reclaimed and seeded last fall appears to be stable, and seeded grasses have recently germinated. Hydrologic Balance Sediment Ponds 005, 006, 016, 016A, and 017 were inspected, and appeared to be functioning properly, with disturbed area runoff properly directed into the ponds. Sediment Ponds 009 and 015, in the Sage Creek watershed were not inspected. Stock ponds in the 005, 006, and 007 watersheds were observed; all held water close to pond capacity and embankments appeared stable. Stock Ponds T-26 and T-27 in the upper 016 watershed could not be accessed. Previously documented mine area springs and seeps were actively flowing; no previously un-documented springs were noted. The following observations regarding ponds and springs were recorded: • The sediment ponds observed were all discharging clear flow. • A significant quantity of sediment, including riprap washed down from eroded permanent channels had been deposited in Pond 016A. • Movement along the toe of the"Pond 16 Slide", which previously damaged Road "J"adjacent to the pond, has impacted the riprap channel between Ponds 016 and 016A. Ground movement, and possibly also heavy flow during the recent runoff event has resulted in constriction of the channel and displacement and mounding of the riprap. Channel repair will be warranted in association with the slide remediation plan to be developed this year. • The riprapped inlet to Stock Pond T-20 was eroded along a 25 segment, and repairs are warranted. Backfilling and Grading Slides and Damage There are three areas of significant slope instability that warrant advisement from geotechnical consultants with regard to development of remediaton plans, to be submitted this year. These locations are the-"Pond 016"and adjacent"Shrub Plot" slides, which have been detailed in recent inspection reports, and a slide that was repaired several years ago on a slope south of the upper segment of 006 Gulch. These slides are delineated on the 2009 R&G map, and the operator has contracted the services of a geotechnical consultant to develop remediation plans. Geotechnical investigations for these slides were initiated last summer, to continue through this spring, with remediation plans to be developed and completed following completion of the investigation. The slides in the lower 016 watershed are described in previous inspection reports and in the Hydrologic Balance section of this report(new movement evident along the toe of the"Pond 016" slide this year). The repaired slide in the upper 006 Gulch watershed has reinitiated movement this spring, exhibiting a new scarp up to 80 yards in length and two feet high along the upper slope, with a parallel toe bulge below. Detailed remedialtion plans for these slide locations will need to be submitted by July 30, 2009. There are a number of additional cracks and minor scarps on steep reclaimed spoil and highwall slopes that have developed or re-opened this spring, and will require repair. Most of these various locations are properly delineated on the 2009 R&G map. One settling crack not indicated on the map was observed (from a distance)along the former highwall in the upper 017 watershed. Hillslope Erosion A significant number of hillslope erosional features were observed during this and the previous inspection, most of which are properly marked for repair on the 2009 R&G Map. The following hillslope rills and gullies were not marked on the map, but will require stabilization: • Numerous rills paralleling the TRM channel north of the aspen test plots; hand cut water bars may be appropriate to direct flow into the channel. A hillslope gully 12"-14" deep enters this channel from the south, approximately 150' upstream from upper end of TRM segment. 4