_INSPECTION - C1981010 (3) - Laserfiche WebLink

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October 4, 2012 C-1981-010/Trapper Mine JLE similar condition as West Flume Diversion 1. Several re-established drainages were walked during this inspection. The following is a discussion of the Division's observations for re-established drainages that were walked and a discussion of future design and maintenance plans for several of these drainages. The West Pveatt re-established drainage that runs through parcel H-C-03 is incised in several locations along the drainage. Water seems to be circumventing the slash piles that have been placed in the drainage and causing some side cutting of the drainage. Vegetation has begun to establish in the base of the channel indicating a possible equilibrium has been reached in this channel limiting the continued down cutting of this channel. DRMS will continue to monitor the drainage. If continued erosion and down cutting is observed, additional repair work may be necessaiv. The East PyTeatt drainage was walked. The upper portion of the drainage is split into three channel arms. The east upper arm is incised in several locations along the channel, similar to the West PyTeatt channel,vegetation has established in the base of the channel possibly*limiting future down cutting. Overall,this is a wide channel with many*check dams in place and slash piles in place to help stabilize the channel. The middle arm of the upper East Pveatt drainage is a wide channel with vein good vegetation established throughout the channel. Small rills have formed in this portion of the channel but they appear to be healing themselves. The west arm of the upper East PyTeatt drainage is also a wide channel with good vegetation established. All three of the upper East PyTeatt arms converge and drain into a single channel. At this point the drainage below the confluence is deeply*incised (up to 15 feet) in many*places. A portion of this channel runs through the western portion of parcel F-AB-05. This stretch of the channel has many*deep erosion cuts and side wall erosion. The Division walked this stretch of the drainage and mapped the western side of the channel with a Trimble YUMA GPS unit. One significant erosion cut was observed along this stretch of the drainage; enclosed with this report is a map of the Divisions findings with the eroded channel depicted along with several larger cuts noted on the map. This is aveiv steep portion of the channel;it drains a large portion of the reclaimed area and receives water from all three arms of the upper portion of the East PyTeatt channel. The Oak Gulch re-established drainage was repaired earlier this year. Many*new rock check dams have been placed in the channel. Several places along the drainage are still incising and many*of the recently*installed check- dams have already*failed. According to the Operator,they will be conducting additional maintenance of the channel in the future. The Middle Flume re-established drainage was walked. This is a gentle drainage with well established vegetation in the channel. Culvert AE-7 under the Life of Mine Road was clear and functional. The re-established drainage to West Flume 41 pond was walked. The upper/southern portion of the drainage has dense vegetation established in the channel and is stable. The lower/northern portion of this drainage is steep in grade and has become incised in places. The Operator will need to monitor this drainage and conduct maintenance operations to repair and stabilize this portion of the channel. Trapper's permit application discusses drainage re-establishment in section 3.5.3 and drainage stabilization in section 4.8.1.3. The permit outlines several options to stabilize the re-established channels such as roving materials, straw bales,brush, erosion mats/blankets and soil confinement sN-stems (page 4-183a). It further states that if drop structures,rip rap lining and/or channel liners which are impervious will be used,they will receive approval from the Division prior to installation(page 4-183a). It appears for portions of the re-established drainages with shallower slopes or portions further up-stream,these methods have been effective. However for Number of Partial Inspection this Fiscal Year: 2 Number of Complete Inspections this Fiscal Year: 2 Page 4 of 10