Published: March 29, 2017 |

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Lawrence County Commissioners gave their vote of support to technical revisions to existing state mine permits for two different Homestake initiatives.

One is a technical revision to state mine permits #332 and #456, to allow for the placement of approximately 875,000 tons of excavated rock into the Open Cut from the Sanford Underground Research Facility.

The other is a technical revision to state mine permit #445 concerning the modification of monitoring plans at the Richmond Hill Mine site to: modify the routine site inspection requirement of the Richmond Hill post-closure plan; modify the leak detection, collection and recovery system leakage response action plan, primarily for the sludge pond, a former barren pond at the Richmond Hill mine site; and discontinue neutron probe monitoring as part of the performance monitoring for the mine pit impoundment.

With the commission’s approval, a letter from planning and zoning director Amber Vogt will be sent to the Department of Environmental and Natural Resources on behalf of the county in support of each technical revision.

Mark Tieszen, Homestake environmental manager, addressed the county commission in regard to the revisions. Also in attendance at the meeting were Homestake closure manager Jeff Burage and Sanford Lab environmental manager John Scheetz.

Referencing a letter to the DENR written by Burage, Tieszen explained that the rock is associated with construction of the Long Baseline Neutrino Facility for the Deep Underground Neutrino Experiment. Sanford Laboratory and the Department of Energy will construct a pipe conveyor and its discharge chute to place the rock inside the Open Cut.

The technical revision includes an 8.3-acre disturbance within the Open Cut pit and a minor re-disturbance of approximately .5 acres outside the Open Cut pit, which is the pipe conveyor/discharge chute and reclamation of the disturbed ground outside the Open Cut pit walls.

“We’ve done some studies, studying the impact of surface or ground water and those are expected to be minimal,” Tieszen said. “The impact to surface water and ground water has been modeled and expected to be minimal. The rock, from the Poorman Formation of the 4,850-foot level Ross Shaft area, has been geochemically characterized by two different consultants and shown to be relatively unreactive and unlikely to produce acid mine drainage or leach heavy metals. Placement of the rock in the Open Cut has the added safety factor in that water coming in contact with the excavated rock will be collected, treated, monitored and discharged by the Sandford Laboratory.”

Air emissions associated with the LBNF activities will also be evaluated by Sanford Laboratory.

Geotechnical issues for this technical revision were evaluated in light of the addition of the rock to the Open Cut. The evaluation indicates the placement of LBNF rock in the Open Cut is low-risk relating to any deep-seated or large-scale slope failure and provides increased stability for portions of the south pit wall.

Burage said that the rock will be crushed to three-quarters to one-half inch in the Ross crusher in order to travel through the enclosed pipe conveyor and then be deposited in the Open Cut.

Depending and contingent upon funding, the project is slated to begin in 2018, first with construction of the conveyor, which will take approximately nine months to one year; followed by the rock removal from the lab’s underground caverns, crushing, and deposit into the Open Cut.

RICHMOND HILL MINE TECHNICAL REVISIONS

Homestake officials wish to reduce the inspection frequency from monthly to quarterly for the reclaimed acreage, water treatment and support facility inspections outlined in the Richmond Hill post-closure plan.

“The change is being requested as site inspections during the winter months are difficult and do not produce meaningful results due to snow cover,” Tieszen said.

LAC Minerals is proposing further revisions to the monitoring and action plan primarily for the sludge pond, the former barren pond, to reflect the existing conditions at the site.

Homestake officials also seek discontinuation of neutron probe monitoring, due to the long-term success of reclamation and successes with the neutron probe.

“This is just one of many types of monitoring that we determined is not needed,” Tieszen said.

Commissioner Randy Deibert abstained from any action regarding the permits.

Source: (March 25, 2017) Black Hill Pioneer

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