_INSPECTION - C1982057 (75) - Laserfiche WebLink

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III. COMMENTS - COMPLIANCE Below are comments on the inspection. The comments include discussion of observations made during the inspection. Comments also describe any enforcement actions taken during the inspection and the facts or evidence supporting the enforcement action. This was a partial inspection of the Seneca II-W mine site conducted by Marcia Talvitie and Sandy Brown. Roy Karo accompanied us on the inspection. The primary focus of the inspection was to evaluate areas on the reclaimed mine site where there are stability issues. The weather was clear and warm. Pond 016 Landslide The slide incorporates a sizable portion of the regraded slope crossed by Haul Road (J), located northeast of Pond 016 (Photo 1). Undisturbed ground upslope of the slide does not appear to have been affected. The lower lobe of the slide has encroached upon the inlet end of Pond 016 (Photo 2). Monitoring wells have been installed by the operator, to document groundwater levels and movement of the slide mass. Potential mitigation measures are currently being evaluated by SCC. Pond 016A Landslide A pair of overlappi ng circular failures has developed on the relatively shallow reclaimed slope of the watershed immediately upstream (ESE) of Pond 016A (Photos 3a and 3b). Groundwater was observed percolating through some of the surface cracks. In one pool, what appeared to be methane was bubbling up from the ground. Pond 016 and 016A Watershed — Channel Erosion A recent, short-duration, high-intensity storm event had caused substantial damage to drainage structures constructed upstream of Pond 016A. Portions of the channels had been lined with Turf Reinforcing Mat (TRM), with varying degrees of success. TRM placed longitudinally in the channel worked best when the channel gradients were lower (Photo 4). It appeared that this technique lost its effectiveness when the channels were steeper (Photo 5) and flow velocities were higher. Roy Karo said these channels will be reconstructed this season. The "shingle" method of TRM installation may be used, wherein shorter strips of the mat are installed perpendicular to the direction of flow, and overlapped, working up-gradient. A pair of 48" corrugated metal pipe culverts (J-2) (Photo 6) was designed to carry channel flow beneath the access road and into Pond 016A. The section of channel immediately upstream of these culverts had been heavily armored with riprap placed on geotextile fabric. The recent heavy flows had gutted the riprap installation, gouged the channel, and transported much of the riprap through the culverts and into Pond 016A (Photo 7). Neckpit The slide area below the ridge south of the A-pit has been recently covered with TRM. Willow wattles were placed below the mat to direct the runoff to the central channel area. (Photo 10).