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Silver Dyke Tailings Impoundment

Site Contact:
Todd DeGarmo


Site Location:
Neihart, MT 59465

The Silver Dyke Mine is located in Operable Unit 3 (OU3) of the Carpenter Snow Creek Mining District Site. The mine operated from 1921 to 1929 and included a mine and mill and three tailings impoundments. In 1925, the original tailings impoundment (Silver Dyke Tailings Impoundment) located in No Name Creek collapsed, releasing a large volume of tailings into Carpenter Creek. The upper and lower tailings piles (UTP and LTP) were built along Carpenter Creek in 1926 to allow operations to continue. In 1929, mining operations ceased, and the tailings impoundments were left to degrade. A significant volume of tailings has since eroded from the UTP and LTP and continues to erode during spring runoff and episodic rain events. The periodic flush of mine tailings affects streamside soil past the confluence of Carpenter Creek with Belt Creek to the Town of Monarch, approximately 12 miles downstream. The Silver Dike adit located on the opposite side of the hill from the Silver Dyke Tailings Impoundment discharges poor quality water to Sih-mem Creek which discharges into Carpenter Creek, where it degrades water quality so severely that fish are not present in the affected stream reach of Carpenter Creek in OU3. The population density and taxa richness of macroinvertebrates in Sih Mem is non-existent due to the high metal concentrations in the adit discharge and is severely impaired in Carpenter Creek downgradient of the Sih-Mem Creek confluence.

In 2014, a removal action was initiated to address the unsecured tailings that remained in the No Name Creek drainage. The goal of this action was to prevent continued releases from the estimated 35,000 cubic yards of tailings at the Silver Dyke tailings impoundment within the No Name Creek drainage area. The action included the following elements: (a) Removing the tailings from the hillside slopes and staging for disposal; (b) Constructing an onsite repository; (c) Placing the tailings in an onsite repository; and (d) Reclaiming/restoring removal area slopes. The removal action occurred between September and October 2014.

Since the removal action was completed, the upper removal area has experienced significant erosion damage from summer storms and spring runoff. Rill erosion is quite evident and is cutting into previous reclaimed areas. A large gully has cut through the center of the erosion blanket, threatening to discharge sediment into No Name Creek. Rill erosion is also evident in the western removal area, particularly just below the tree line area. This time-critical removal action (TCRA) is to address the surface soil contaminated with elevated concentrations of lead and repair the significant erosion damage at the Silver Dyke Tailings.Impoundment.