Cobalt Mining Legacy
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Early photos of the Cobalt area show extensive waste rock piles. For example, there were very large waste rock piles at the south end of Cobalt Lake from the Cobalt Lake and MacKinley-Darragh mines. Waste rock piles from the Coniagas and Tretheway mines dominated the town skyline when viewed from the east side of the lake.
Over the years, most of these waste rock piles have been removed, and today, visitors will see little evidence of the waste rock piles that once dominated the area. There are a number of activities which have contributed to this, as described below.
Removal of Waste Rock for Reprocessing
Since the early days of milling in Cobalt, when the waste rock from the early hand sorting operations was re-processed in the mills that were built in the area, waste rock from previous operations became a resource. As milling methods improved, and it become possible to recover silver from lower grade ores, waste rock was recovered from waste rock piles and reprocessed to recover the silver. In addition, significant amounts of waste rock were reprocessed to recover cobalt, as that metal became more valuable during World War II and in the post-war period. Thus, the rock from many of the waste rock piles seen in those early photos has been crushed, ground and processed, and been added to the extensive tailings deposits in the area.
Use of Waste Rock as Fill:
Waste rock has been used as construction fill in the area. It is not known how extensive this practice was, or how widely dispersed waste rock from Cobalt became as a result of this practice. But it is clear in many areas around town that some areas have been filled in extensively, such as the area between “The Square” and the train station. There no documentation to prove that this area was filled with waste rock, but it is difficult to imagine that the readily available waste rock would have been passed over in favour of rock from some other source in filling in this and other areas around town.
It is known that after a major fire in the summer of 1977 that destroyed many homes and businesses in the north end of town, debris and waste rock from around town were dumped into Cobalt Lake, creating the foundation for the Lion’s Club park that now bisects the lake.
As environmental monitoring and research continues in the Cobalt area, some attention should be paid to waste rock used as fill. First, it would be valuable to know more about how extensive this practice was, and how many areas in town and elsewhere have been filled with waste rock. Second, it would be important to know if this waste rock material is a source of releases of arsenic and other metals. If it is, then potential risks associated with these releases should be assessed, and the actions needed, if any, to remediate these sources of environmental releases should be identified and implemented.
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