SMC's Benbow Exploration Portal Project is a go
The Stillwater Mining Company has been cleared by state and federal agencies to launch its Benbow Exploration Portal project, which is expected to expand the life of the mine by decades and increase overall production.
And the company is wasting no time, with work scheduled to begin in the next two weeks.
The Custer Gallatin National Forest Service and the Montana Department of Environmental Quality last week issued a decision notice that approves the planned construction of an underground exploration decline and related surface support facilities.
A year ago this month, SMC submitted its 2-inch thick formal plan of operations for what is called the Benbow Exploration Portal and support facilities. The proposed project site is near the old Benbow Mill near Dean and primarily involves mineral exploration along the eastern edge of the JM Reef. In the long term, assuming “economic mineralized resources are found,” the portal will be used as mine ventilation, a secondary underground escape-way and on a small scale, to re-supply the Nye mine, according to SMC's proposal.
The Benbow Portal will run 24 hours a day, seven days a week and be staffed by approximately 25 people, according to the proposal. The total permit area is 920 acres on the far eastern edge of the JM Reef, which is under SMC claim package. It is estimated that only 35 acres or less will be disturbed for the project. (See inset box for more details).
Tree clearing and gravel hauling and placing is expected to being in the next few weeks. Forest users should expect truck traffic and short delays on Benbow Road No. 2414, according to Custer Gallatin National Forest Service. The project is expected to span for at least three years.
Part of the Blitz Project
The Benbow Portal is part of the present Blitz Project, which is using a custom-built underground tunnel boring machine (TBM) to cut through 23,000 feet of rock to eventually connect the East Portal at the Stillwater Mine to the Benbow Portal, allowing for lateral development of the JM Reef. To date, the TBM has advanced approximately 7,400 feet, according to the company's 2015 second quarter earnings report.
The TBM tunnel, as well as a parallel tunnel being dug roughly 600 feet about the TBM tunnel, will eventually be intersected by the Benbow Portal, providing ventilation and an emergency egress for the Blitz work area.
SMC expects the Blitz Project is expected to extend the life of the mine by decades and increase overall production.
Project Details
As outlined in the U.S. Forest Service's decision notice dated Sept. 2, the details of the Benbow Exploration Portal project are as follows:
Surface infrastructure includes a portal pad, an access road, waste rock management facilities, water wells, a water treatment plant and a water disposal system. Excess water generated from mineral exploration will be collected and treated to remove nitrogen to comply with state water quality standards.
Two potential water disposal options are authorized:
1) Injection well disposal.
2) Land Application Disposal system.
Injection well disposal is the preferred option and would consist of injecting treated water into the Environmental Protection Agency approved receiving groundwater aquifer. Land Application Disposal would be utilized in the event that the injection well disposal results in water quality violations or if the injection well does not function. Land Application Disposal would consist of storing treated water in a pond and using pivot sprinklers to evaporate and apply treated water across meadows in the Benbow area during summer. This decision also authorizes use of waste rock to surface roads and campsites, cap historic chrome mine tailings and create a new parking area for the Chrome Lake Jeep Trail trailhead.
SPA Concerns Abated
The Stillwater Protective Association and SMC last year worked together to address some SPA concerns regarding surface impacts, including “the overall function and footprint” of activities in the old Benbow area, waste water treatment, traffic management and other issues, according to an SPA press release issued at that time.
The SPA wrote that these concerns were addressed at a meeting last year with SMC and at SPA’s request, SMC agreed to develop a Benbow Mitigation Plan to supplement the legally binding Good Neighbor Agreement.