Brownfield Remediation Activities
When Redfern Resources Ltd. took ownership of the Tulsequah Chief mine, the Company committed to cleaning up the historic source of pollution from “potentially acid generating” rock (PAG rock). Implementing clean up works at the Tulsequah Chief is a multifaceted process with many challenges. Redfern, however, is steadfastly restoring the environmental conditions of the Tulsequah Chief.
At the present time, some of the challenges associated with immediate clean up of the historic PAG include:
Terrain
The Tulsequah Chief mine site is located on the side of a mountain with the Tulsequah River at the toe of the site. There is almost no flat ground or space at the mine site.
Access
At the present time, there is limited access on site; no airstrip and only a short (4km) road exists to allow for access. Permit Applications have been submitted and the first phase, MX 1, initial road construction has been authorized. Access is not yet sufficient to provide full access to the Tulsequah Chief minesite. Without surface access to the mine site transportation of cleanup equipment and necessary water treatment is not possible.
It is also important to note that without year-round access to the site, it is not possible to operate any permanent type of treatment system and accomodate the associated personnel required to operate it.
Source
When water in the presence of air, flows over mineralized rock containing sulphide minerals, the water can become acidic and be contaminated with metals. Water can presently migrate through the old mine workings, contacting the mineralized rock, and this water then flows out the mine portals. There is also mineralized waste rock in a series of rock dump located on surface at the mine site. There is very little that can be done right now to stop the flow of water through the old mine. The best method to stop this problem is to fill all the old underground workings and flood them. This is a major undertaking that requires mine redevelopment.
Old Mine Remediation Process
Redfern has a very comprehensive and detailed plan for the old mine cleanup which was approved of by the BC Environmental Assessment Office in 1998 and reapproved in 2002. The approved plan calls for a progressive cleanup and reclamation of the old mine at the start of and during the operations of the new Tulsequah Chief mine, which is located primarily below the old mine.
Upon commencement of mining operations, the old mine’s underground workings will be filled with cement stabilized backfill (crushed rock) which will significantly reduce, if not eliminate, the flow of water through the old mine. This will effectively stop the flow of contaminated water that is currently leaving the old underground mine.
Present Day Remediation Initiatives
Redfern has made application to the Province of British Columbia and the Department of Fisheries and Oceans to begin the process of cleaning up the historic PAG rock. Once approved, our process is as follows:
- Construction of a new lined and covered, historic PAG waste rock containment site. This waste rock cell will safely and securely store the old PAG waste rock during the life of the new mine.
- Relocation of the historic waste rock from its current location, into the new containment cell.
- An interim water treatment plant will be brought to site. This treatment plant will not only treat any contaminated water from the new containment cell, but also start treating contaminated water leaking from the old mine prior to the completion of the underground backfill operation.
Operational Remediation Process
Towards the end of the new mine’s projected life (about 8 years), there will be enough space underground so all historic sources of contamination can be moved back underground, which is below the water table. When the historic PAG rock is placed back underground and the new mine is closed, the PAG rock will be flooded naturally. Once flooded, oxygen is unable to interact with the PAG rock, therefore, eliminating any acidic waters and associated contaminants. This is the most acceptable and environmentally secure way of ensuring that there will be no further contamination associated with this old rock.
What Remediation Work Has Redfern Done?
Over the last several years, Redfern has invested considerable effort to reduce the flow of historic contamination leaving the site. As noted earlier, the difficult site conditions and lack of access has limited what can be done. However, Redfern has made noticeable progress in reducing water contamination associated with the old mine. These include:
Work to plug holes and reduce inflows of water to the old mine.
Water has been re-routed underground so less water flows over the PAG rock, which in-turn reduces the amount of contamination generated. These measures have resulted in a 30% reduction in the total amount of contamination leaving the site.
In 2005, a passive water treatment system was installed underground in the historic workings of the Tulsequah Chief mine, consisting of 4 in-line cells using limestone and organic materials. The system has been monitored since 2005 and has demonstrated considerable success in reducing the concentration and loading of metals. In fact, metal loadings in the water treated have been reduced by more than 90%.
In 2006, refinement of this treatment system was implemented with the addition of pre-treatment pH adjustment to improve performance.
While the system has shown improvements, permanent cessation and remediation of the old workings will ultimately be achieved through backfilling the old mine workings with neutral material as described above.
Big Bull Mine Remediation
At the abandoned Big Bull mine located on the Taku River, a number of measures have been initiated to reduce contamination associated with this old mine. Drainage from the old Big Bull mine has been captured and redirected, essentially eliminating direct discharge of contaminated water from the mine to the Taku River. Water will also be diverted from flowing into the old Big Bull mine, which will substantially reduce the generation of contaminated water.
Will the New Tulsequah Chief Mine Cause Environmental Problems?
Today, mine developments are carefully planned, assessed and are strictly regulated by several provincial and federal agencies.
The new Tulsequah Chief mine has undergone numerous environmental assessments and has incorporated a myriad of state-of-the-art environmental controls and management plans to prevent pollution, to ensure that all regulations have been met and or exceeded.
Modern mining operations are financially bonded to ensure reclamation activity occurs whether at the planned shut down date or sooner. |
