_INSPECTION - C1994082 (46) - Laserfiche WebLink

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Yoast Mine Phase I bond release, pg. 4 YPM-14 involves a steep section above the YPM-3-1 channel and pond 13, and we measured a representative slope of 45% for this area. Some minor side-scour has occurred and maintenance is recommended. We also inspected a newly re-graded area that included a 50—foot haul road cut. The area has been topsoiled and meets AOC concerns. The area blends into the existing topography and is ready for seeding. We next inspected a nearby drainage (later identified as the YPM-6-1 channel)that has had TRM installed and has been rip-rapped. We closed the day with the following synopsis of our findings: most of the pro's are in pretty good shape, although some repairs are needed due to scouring; some gullies need additional re-grading to form a tributary channel with TRM and/or installing rock checks in accordance with the permittee's approved rill and gully plan. Mr. Mathews noted that before DBMS issues a proposed bond release decision, he wants to be able to say that the rills and gullies have been substantially addressed this season. This concluded the inspection for August 15tn We began the inspection July 16tn by walking the entire YPM-1-2 channel. The upper portion of the channel is lined with granite rip-rap and volcanic rock. We measured a representative slope of 10%in the upper portion of the channel. A gully has been converted into an ephemeral drainage in accordance with the permittee's approved rill and gully plan. We measured a representative slope of 7% in the lower portion of the channel. Rip-rap is no longer needed and a TRM has been used in its place as allowed by the approved plan. The channel is well constructed and looks good. We also inspected upper YPM-18,which is a tributary that feeds into YPM- 1-2, and measured a representative slope of 28%. The tributary has been lined with TRM, looks good, and creates the YPM-1-3 channel. YPM-1-3 is lined with TRM and generally looks good, although some scouring has occurred under the TRM. This requires some maintenance work and is an area to monitor. We measured a representative slope of 10% in the upper portion of the channel. YPM-19 is a tributary that feeds into YPM-1-3 and creates YPM-6-1. YPM-19 is also lined with TRM and we measured a representative slope of 26% in the upper portion of the channel. The drainage basin (drift area) at the head of the YPM-19 watershed is heavily rilled and has poor vegetation establishment. As a result, Mr. Mathews recommended additional inter-seeding with a drill on the contour, and possibly more ripping in the "bowl area." The old backfilled"sinkhole" feature on the slope west of YPM-6-1 was also identified as an area to monitor. This area was originally 30 feet deep and has settled following repair. We continued at the YPM-6-1 channel which had previously been blown out. It is lined with TRM but has been undercut in places and there has been some side-scouring. As a result, TRM maintenance is required to prevent further scour beneath the liner. We measured a representative slope of 12% in the upper portion of the channel. A spring has emerged under the channel approximately 80 yards below the YPM-19 tributary that requires additional armoring to confine the flow. We also noticed that undercutting occurs above the spring's emergence, and the channel looks much better below the emergence. We measured a representative slope of 18% in the lower portion of YPM-6-1 which has been repaired with rip-rap. The lower portion of the channel may eventually need to be reconfigured and reworked to prevent side-scouring. YPM-6- 1 continues through a stand of trees and dense vegetation and ends at a possible location for stock pond ST-2.