2014-09-29_INSPECTION - C1980004

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September 16, 2014 C- 1980 - 004 /McClane Canyon Mine ZTT area. A sump like containment area confines water and then flows through the culverts below the portal bench before discharging into the clean water stream bed that parallels the haul road. With the storm event, both of these culverts were completely submerged in sediment, subsequently clogging the entire culvert system below the portal bench. As per Rule 4.05.3, Temporary diversions shall be constructed to pass safely the peak runoff from a precipitation event with a 2 -year, recurrence interval, for a watershed less than one square mile. Both contributing drainages to Culverts A and D are smaller than one square mile and the measured rainfall exceeds the 2 -year event for that area. The temporary diversions Culverts A and D met all criteria required by the Division and Rules for the size of the precipitation event and as a result, no violation is necessary. These culverts must be cleaned out and reestablished for compliance. Upland diversion Culvert B was also plugged with sediment and debris as a result of the storm. The clean -up crew was in the process of cleaning out Culvert B at the time of the inspection. No issues were observed. Upland diversion Culvert E was not clogged. No issues were observed There is one sediment pond on site. The pond is approximately 90% full of sediment from the storm event at the time of the inspection. The majority of sediment appeared to have come down from the upper basins above the mine site that flowed through the site as a result of the upper culverts clogging. The primary spillway was buried beneath the sediment and mine representatives stated that it was plugged with sediment and debris. The primary spillway needs to be reestablished and cleared of sediment for compliance. The Division has been in contact with McClane Canyon Mine's primary permitting contact, Jim Stover, and has discussed options for sediment storage while cleaning out the sediment pond. Currently the Division has received a revision submission to address sediment storage and the Division is in the process of reviewing this revision. As a short term option, the mine plans to use the already approved sediment drying area above the sediment pond. All culverts and associated sumps were filled with sediment. As per Rule 4.03.1(4)(e), haul road culverts require a maximum design criteria to safely pass a 20 -year 24 -hour precipitation event. The precipitation event exceeded the 25 -year 24 -hour and as a result, no violations are warranted. Culverts and related sediment control structures need to be reestablished for compliance. Ditches throughout the site have been filled with sediment. Due to the mine's site restrictions within the canyon and berm reestablishment (see Roads — Rule 4.03), all disturbed runoff is still conveyed successfully to the mine's sediment pond. These ditches need to be cleaned of sediment as maintenance prioritization allows. Located west of the mine office are two silt fences. Both silt fences were in place but clogged with sediment. These silt fences need to dug out and all sediment build -up to be removed. Additional silt fences are found within haul road beans to allow road runoff sediment to be collected before leaving the site. These silt fences also need to be fixed and cleared of sediment build -up. Silt fences associated with the topsoil pile and material stockpile were destroyed as a result of the storm. These silt fences need to be restored in the necessary areas. Silt covers the majority of the area west of the sediment pond and material stockpile due to the flooding. The majority of the silt is found just below the stockpile and thins out the closer you get to the East Salt Creek. This Number of Partial Inspection this Fiscal Year: 0 Number of Complete Inspections this Fiscal Year: 1 Page 3 of 9