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The Henry’s Knob Former Mine Site (the “Site”) is located near the intersection of Highway 55 and Henry’s Knob Road in Clover, York County, South Carolina and encompasses approximately 185 acres. The Henry’s Knob Site was an open pit kyanite mine that operated from 1947 to 1970. Kyanite is primarily used in producing refractory, ceramic and porcelain materials that withstand high temperatures. The Site derives its name from the relief feature known as Henry’s Knob which was transformed into an open pit mine and then allowed to fill with water and is now a seven acre acidic pond.
The Site consists of the former open pit mine, tailings ponds, spoils piles, and remnant mine operation buildings. The Site is currently being remediated through the Superfund Alternative Approach to address the contamination on the groundwater, sediment, soil and surface water present at the Site from the former mine operations. Sampling has found elevated levels of arsenic, manganese, cadmium, lead, chromium, copper, cobalt, magnesium, barium, and zinc with the primary contaminant being manganese.
The Site has been broken down into 10 Areas of Concern (AOCs) and multiple offsite residences where contamination has been found in their well (primarily manganese). These ten AOCs are:
- Area 1 – West Tailing Pond, an industrial waste lagoon on the western side of Henry’s Knob Road
- Area 2 – North Tailings Pond, infiltration beds/settling ponds on the eastern side of Henry’s Knob Road
- Area 3 – Former Mill Operation Buildings on the eastern side of Henry’s Knob Road
- Area 4 – Mine Pit Pond
- Area 5 – East Tailings Pond, also known as the Mine Tailings Area
- Area 6 – South Fork of Crowder’s Creek
- Area 7 – Dumping Area, located on the eastern side of Henry’s Knob Road
- Area 8 – Northern Waste Rock Area
- Area 9 – Southern Waste Rock Area
- Area 10 – Site Ground Water
In 2004 EPA and ABB, Inc. entered into an agreement to conduct a Remedial Investigation (RI) and Feasibility Study (FS) or RI/FS. In addition, ABB has hired AMEC as their contractor to investigate the impacts of kyanite mining and to develop and implement a cleanup plan that is protective of human health and the environment. EPA, in collaboration with the South Carolina Department of Health and Environmental Control (SCDHEC) is overseeing activities conducted by ABB and AMEC at the Site.
What Is Being Done to Clean Up the Site?
Most of the residents in the vicinity of the former mine obtain their drinking water from private wells. Once the groundwater plume was delineated ABB, EPA, and SCDHEC developed a plan to sample the private wells and if the concentrations exceeded established residential groundwater objectives well head treatment systems were to be installed. To date, 18 wellhead treatment systems have been installed. Several others have been identified and the RP is awaiting access. The primary contaminants of concern are manganese and cobalt.
What Is the Current Site Status?
Remediation work began at the site in September 2015 with the regrading and revegetation of AOC 3. AOC 3 was the former waste rock storage area and provided a difficult challenge due to its steep slope and tight working area. To date, the AOC 3 remediation work has continued to reduce erosion of the area and the vegetation continues to thrive.
During the summer and fall of 2016, ABB completed work on the AOC 1 tailings pond area. The initial work was to repair the terminal dam for the tailings pond which took several months to complete, but is now properly constructed to retain the tailings behind. The next step was to repair the drainage path through the large tailings area that comprises AOC 1 and then amend the tailings to allow the vegetative cover to grow. This work was completed in November of 2016. The grasses have already come in at a rapid rate and wildlife has returned to the area. It is expected that over time the new vegetation will help reduce infiltration of stormwater through the tailings to the groundwater.
During the winter and spring of 2016 and 2017 respectively, ABB completed work on the AOC 2 tailing pond area. The work in this area was to repair the intermediate dam between AOC 5 and AOC 2 and the terminal dam at the base of AOC 2 that holds the tailings back from entering the east tributary to the South Fork of Crowders Creek. In addition to the dam work, crews also revegetated two large areas of tailings. This work was completed in March 2017.
Crews finished work on AOC 5 in December 2017.. This is a large tailings pond that runs along the eastern side of Henry’s Knob Road and is located on the western downslope of the Knob. This area was particularly challenging due to the slope and drainage associated with it. The same sort of work will be conducted here as on the other tailings ponds. The completion of AOC 5 marked the end of the stabilization work at the Site.