_INSPECTION - C1994082 (46) - Laserfiche WebLink

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Yoast Mine Phase I bond release, pg. 3 permittee consider adding a series of winged diversions and cut into the side of the YPM-1-1 channel. Lower YPM-1-1 exhibited good vegetation and we measured a representative slope in the channel at 3%. However, a wide, flat part of the channel that runs somewhat outside the channel boundary was identified as an area to monitor. YPM-1-1 drains into stock pond ST-1. The embankment of ST-1 appears to be stable but it needs to be topsoiled and seeded. Ms. Brown and Ms. Talvitie walked the YPM-3-2, YPM-4, YPM-17, and YPM-24 channels. The YPM-3-2 channel was lined with boulders and a steeper portion of the channel, located downstream of the fenced shrub plot, had been modified somewhat by higher-energy flows. The flowline follows an irregular path, weaving from one side of the channel to the other and in some locations rocks have been moved sufficiently to expose the geotextile fabric beneath. This channel should continue to be monitored, to ensure that the flow does not leave the protected reach and cause erosion on the adjacent reclaimed slope. A natural spring had caused some "eruption"in the native clayey soils at the head of the YPM-4 drainage. The channel itself is paved with small boulders and appears to be stable throughout its course to Pond 13. The bottom of the YPM-17 channel was very well vegetated, and large rocks (12"to 30" in diameter) line the sides of the channel. YPM-24 is a long stretch of native channel below YPM-8 which eroded and was repaired with TRM liner and is underlain with V=Weirs constructed of willow bundles. Some of the weirs were installed pointed upstream, and others were pointed downstream. The permittee is experimenting to see which method of weir construction works best in this application. We walked the entire length of the YPM-5-1 channel that is located above pond 12. This channel was also lined with cinder/volcanic rip-rap and is fairly well vegetated. We measured a representative slope in the lower portion of the channel at 8%. Settling cracks on the slope west of the channel and upstream of Pond 12A was identified as an area to monitor and will be followed up on by Mr. Mathews. We then measured a representative slope in the mid-section of the channel below the YPM-5-lA junction at 19%. A portion of the channel is creating its own boundary outside of the design area and the Mr. Mathews recommended additional armoring work. We also noticed the creation of additional rills and a gully down to the spoil upstream of the channel. As a result, Mr. Mathews recommended that additional grading and seeding be constructed below the area and that water bar construction occur at the top of the area. We measured a 21% slope at a steep segment above the YPM-5-1A junction and noticed that some low density scoria rip-rap had scoured along a 40-foot segment. Consequently,this section will need to be monitored to ensure that flow does not escape the channel outside of the riprap zone. We also measured an 18% slope in the steepest segment of YPM-5-IA, and a representative slope in the upper reach of YPM-5-1 at 9%. We measured a representative slope in the upper reach of the YPM-3-1 channel at 2 1% and a slope of 7%in YPM-3-IA. We then measured a representative slope in the lower reach of YPM- 3-1 at 18% and Mr. Mathews noted that a gully that runs to YPM-3-1 will be graded out and lined with TRM in accordance with prior discussions between DRMS and the permittee. Mr. Mathews also recommended some hand work and installation of rock checks to mitigate some rills that have developed on the slope between shrub plots, and that the fencing around the woody-stemmed plant reference area be repaired and monitored.