Cobalt Mining Legacy

Arsenic and Old Pits – an Environmental Legacy

Decades of mining activity have forever scarred the landscape around Cobalt. This activity has left a significant environmental legacy. There are two aspects to this legacy – mine hazards, and pollution.

Mine Hazards

At the Canadian National Vimy Memorial Site in France, it is important to stay on the trails. Venture off the trails, and danger may lurk. Unexploded bombs and shells lie just beneath the surface, still powerful enough to maim and kill decades after the battle. So too in Cobalt, dangers may lurk. Because the silver veins were often right at the surface, the landscape is dotted with pits and trenches. Step into one and you could break an ankle, or fall to your death. Many of these mine hazards are now fenced off. Others are not.

A further hazard, more hidden, is mine subsidence – the collapse of underground mine workings, leading to problems on the surface. Subsidence is a particular concern in Cobalt because the veins were very close to the surface – few of the mines went down more than 300 feet. The problem is made more complicated in Cobalt by the fact that the town was built around the mines, and there are many miles of mine tunnels under the town, some very close the surface.

One morning in 1987, a small hole appeared in Highway 11B in town. By the end of the day, there was a large hole in the road, and the road was closed. The road caved in as a result of the collapse of the underground mine workings, leaving a 60 foot gap in the road. People jokingly referred to it as the world’s biggest pothole, but it was a graphic demonstration of the risks of mine subsidence in Cobalt. The Ontario government spent several millions of dollars in the 1980's and 1990's, testing to identify areas at risk for subsidence, and then doing remedial work to reduce those risks.

Barren Hills, Mine Waste and Water Pollution

Visitors to Cobalt may note with some surprise the almost barren hill on the east side of Cobalt Lake, sometimes referred to as “Nip Hill” since this was the property of the Nipissing Mining Company. The area around Cobalt is also littered with the leftovers of decades of mining – waste rock and tailings. And the lakes and streams around Cobalt are laden with arsenic and other contaminants.

In many ways Cobalt stands as a testament to just how much mining has changes in the last century. The prospecting and mining methods used in Cobalt would be completely unacceptable today.

Silver was found in narrow veins in the rock, and there were hundreds of these veins, many very close to the surface or right at the surface. The preferred method of finding these veins was to cut all the trees and systematically dig trenches down to the bedrock. The Nipissing Mining Company, which held one of the largest areas of claims in Cobalt, took this method one step further. Lake water was pumped up the side of Nip Hill, and then sprayed under high pressure, removing all of the soil. Nip Hill was laid completely bare. Today, almost 100 years later, much of the hill remains barren, and while it is a great place for geology students to explore, trees are struggling to retake the hill, and make it green again.

The soil from Nip Hill ended up in the nearby lakes – Cobalt Lake and Peterson Lake. By 1910, Cobalt Lake was dirty and murky, full of debris from the prospecting, as well as mine tailings from the nearby mills. Even the Cobalt Song, written in 1910, refers to Cobalt Lake as “a dirty old place”.

Waste products from the mining and milling of the ore, waste rock and tailings, were disposed of with no regard for the environment. Waste rock was frequently disposed of in dumps that extended outwards from mine headframes. Similarly, tailings were normally disposed of in the closest convenient depression in the land, sometimes even right beside the mill. Since some tailings were built on lakes, including Cobalt Lake, many tailings were also disposed of in the lakes.

The waste rock and tailings contained minerals composed in part of arsenic. The waste rock and tailings were also high in nickel and cobalt. This is because the silver ore in Cobalt was a mixture of silver with a number of different minerals known as arsenides and sulfarsenides – minerals in which a metal are bound to arsenic. Little of the arsenic was ever recovered, and most ended up in the waste rock and tailings.

Arsenic continues to leach from these mining wastes, and most of the lakes and streams around Cobalt are laden with arsenic – some of the highest concentrations of arsenic in water anywhere in Canada. And despite recent remediation projects, Cobalt remains one the largest sources in Canada of releases of arsenic. Estimates of the amount of arsenic discharged each year into Lake Temiskaming range from 10,000 to 18,000 kilograms – more than all operating mines in Canada, combined!

Sins of the Past

At the time that most of the mines operated in Cobalt there were no environmental controls - no measures of any kind to protect the environment or the health of the people who lived in Cobalt. Yet it would not be true to say that this was done out of ignorance of the effects the mining had on the environment.

In the early days of mining in Cobalt, the mine managers recognized the importance of ensuring a clean water supply for the town. They successfully lobbied the province to establish legislation to protect Sasaginaga Lake, just west of town, from any development. The mine managers were well aware that mining on the shores of the lake could forever pollute the closest source of clean drinking water.

In 1914, Cobalt Lake was drained to allow mining of veins under the lake. At the time, there was much local concern about the risk of disease, but a local doctor refuted this saying that “the waters were a gift of nature, but since they were now so polluted there was no real drawback to draining the lake.”

Thus, there is evidence to suggest that there was some awareness of the harm that mining was doing to the environment.

It is easy for us now, 100 years later, to point an accusing finger, judging our ancestors for their negligence, and blaming them for the mess in Cobalt. But there would be nothing to be gained from blaming the prospectors and miners of Cobalt for the mess they made. There is, however, much to be learned from the mistakes made in Cobalt, and the vast improvements in environmental protection measures in mining in the past decades indicate that much has been learned.

Even if the will had existed to make efforts to reduce or prevent pollution, the knowledge of how to do that in any but the most rudimentary of ways simply did not exist. Indeed, just as the unique ores of Cobalt presented challenges to metallurgists trying to process the ore and recover the silver, so today the unique make-up of those ores present a challenge to those trying to clean up Cobalt and reduce or eliminate continued pollution of the water around Cobalt.

Information on this Website

This website contains considerable information on the environmental legacy of mining in Cobalt. This includes an overview of the environmental concerns in Cobalt, as well as more detailed information. Several reports on environmental work in the area are available for download on this site, and the abstracts of others are provided, giving those using this website access to as much information as possible about environmental concerns and research in Cobalt.

The objective of providing this information is to raise awareness of the environmental issues in Cobalt. At the community level, this may help those in Cobalt and surrounding areas to better understand the extent of pollution in the area, and to better understand the impacts and risks created by that pollution. For those interested in doing research in the Cobalt area, or working on remediation projects in the Cobalt area, this site can serve as a starting point – a clearing house of available information, highlighting the work that has been done to date, and some of the challenges that remain.


Those interested in learning more about the environmental legacy of Cobalt can go to following pages: