Blog Entry

Elliot Lake Uranium Mines

Jamie Kneen

National Program Co-Lead

By the early 1980s, the development of high-grade uranium deposits in Australia and Saskatchewan played a major role in driving down the price of uranium -- along with the collapse of the Canadian industry's illegal price-fixing cartel. The mines at Elliot Lake, Ontario, with their massive but low-grade ore reserves, were unable to compete in the world marketplace and secure new contracts. The mines operated until their contracts ran out, shutting down operations in the early 1990's.

Stanleigh remained in operation until July 1996. The mining companies and regulatory agencies recognised that there were problems associated with the closure of large uranium mining/milling facilities because the waste management areas were not originally designed with currently acceptable standards in mind. Although these concerns have been addressed, the communities in the Serpent River Watershed are faced with the reality that 170 million tonnes of tailings from the uranium mines "present a perpetual environmental hazard." The management of the tailings will always be a challenge. The half-life of the radioactive hazards in those tailings is hundreds of thousands of years.

Rio Algom

In 1953 Algoma became the world's largest uranium find. Twelve mines were quickly developed during the nuclear weapons build-up of the 1950s and 1960s and 25,000 people moved into the region. For 40 years the economy of Elliot Lake, the Township of the North Shore and the Serpent River First Nation was driven by the mining industry.

By 1960, Rio Algom had 8 mines in the Elliot Lake area. They eventually created more than 100 million tonnes of waste.

  • The Lacnor Mine operated from 1957 to 1960, producing 2.7 million tonnes of ore.
  • The Nordic Mine operated from 1957 to 1968 and produced 12 million tonnes of waste.
  • The Panel Mine and Mill produced uranium from 1958 to 1961, and then again from 1979 to 1990. It also produced 16 million tonnes of waste.
  • The Pronto Mine and Mill processed 2.1 million tonnes of uranium ore between 1955 and 1960, when the mill was converted to process copper. Copper processing continued until 1970. The Pronto Mill produced 4 million tonnes of waste.
  • The Quirke Mine and Mill operated from 1956 to 1961, and then from 1968 to 1990. It produced 46 million tonnes of tailings and waste rock.
  • The Spanish-American mill operated from 1958 to 1959 and dumped 400,000 tonnes of waste in Oliver Lake.
  • The Milliken and Stanleigh mines and mills produced 20 million tonnes of waste and tailings. The Milliken mill operated from 1958 to 1964, and the Stanleigh mill operated from 1957 to 1960, and again from 1983 to 1996.


Denison Mines Limited operated in Elliot Lake from 1957 to March 1992, producing about 70 million tonnes of waste at the Stanrock, Can-Met, and Denison mines. See The Gulliver Denison Mines Ltd. Dossier for ownership history and details. In addition to its Elliot Lake properties, Denison has interests in several uranium properties in northern Saskatchewan. Denison has since restructured to sever its active and defunct uranium mining operations and their attendant liabilities (Denison Mines) from its new and profitable energy business (Denison Energy).

By 1976 all 55 miles of the Serpent River system were badly contaminated with acid generating, highly radioactive wastes. An official Ontario report noted that there were no living fish in the entire river located downstream from the mining wastes.

In 1978 alone, more than 30 tailing dam failures were reported.

For more information, read this article by Nuclear Awareness News, part of the Nuclear Awareness Project:

Uranium Tailings in Elliot Lake


The majority of uranium tailings in Canada -- about 200 million tonnes -- are located in Elliot Lake. However, neither the federal or provincial governments can confirm exact locations and quantities. There are about 60 million tonnes of tailings at Rio Algom's Quirke and Panel mines, and about 70 million tonnes at Denison's Stanrock and Denison mines. In addition, Rio's Stanleigh mine is still operating in Elliot Lake until 1996 and has produced over 15 million tonnes of tailings. Former Rio Algom mines in the Elliot Lake area include Nordic, Lacnor, Spanish American and Pronto. There are also a number of areas where tailings have spilled accidentally over the years. The Agnew Lake site near Espanola, while not in the Elliot Lake basin, also has an impact on the regional environment.

Waste from uranium mining takes the form of both waste rock and tailings. In the mill, uranium ore is crushed and chemically treated to remove uranium. The grade of ore in Elliot Lake is typically 0.1% U3O8 (uranium concentrate, known as yellowcake). Thus every ton of ore mined in Elliot Lake yielded a ton of tailings, as well as about two tonnes of process liquid. The leach residue still contains most of the radioactive decay products of uranium. The solids are known as tailings. About two thirds of the tailings are similar to course sand, although the finer remainder (known as slimes) contain a higher concentration of radionuclides. The tailings are normally transferred in slurry and historically were simply dumped into nearby depressions or lakes, depending on nature to do its best to cope with the environmental devastation.

The uranium ore of Elliot Lake contains the sulphide mineral pyrite, which can oxidize into sulphuric acid. Acidic drainage is a major environmental problem with uranium tailings in Elliot Lake. Acidity also mobilizes some metals such as radium, copper, zinc, nickel and lead.

In addition to the problem of acidic drainage, uranium wastes have the problem of radiological contamination. Thorium-230 is the uranium decay product with the longest lifetime -- it has a "half life" of 76,000 years, thorium-230 turns into radium-226, one of the radionuclides of most concern in uranium tailings. Radium is chemically similar to calcium, and thus if ingested, concentrates in the bones, teeth and breast milk of mammals (including humans), where it increases the risk of cancer. Radium in turn produces radon gas (radon-222), which is known to cause lung cancer when inhaled. Because thorium-230 is so long-lived, radium and radon are being constantly produced and released from tailings over an extremely long period of time. The amount of any radioactive element decreases by a factor 1,000 in ten half-lives. Thus, in 760,000 years, one gram of thorium-230 will be reduced to a milligram. For human purposes, radiological contamination from uranium tailings is a problem forever.

It was only following public attention in the 1960s that regulatory attention began to be paid to uranium tailings in the 1970s, looking at long-term radiological and acidification impacts. The theoretical objective is to reduce the flow of water through the tailings, and to eliminate the flow of contaminants from the tailings piles. In the 1970s, rudimentary treatment processes were implemented that can be best described as a form of modified dumping. This remains the current practice. After the settling of solid materials, wastewater flows into holding ponds, where barium chloride is added to precipitate out radium-226, which is left in a sludge on the bottom of the holding ponds. The tailings are also neutralized to reduce acid in surrounding waters. Although there are gates on some roads to tailings sites in Elliot Lake, sites are readily accessible, being neither fenced nor guarded.

There are a number of possible remedial actions for uranium tailings, including waste rock or earth cover; water cover; pyrite removal; removal of harmful radioactive substances; and the use of various types of impervious covers or liners. Tailings treatment for new mines is entirely different from historic sites, where tailings were generally dumped in the nearest lake or ground depression. Various options may involve the moving of existing tailings sites. In the current environmental assessment, both Denison and Rio Algom want to cover most of their tailings with a few feet of water, as a means of preventing acid formation and reducing radiological emissions. The water cover option also happens to be the cheapest option. However, in the long run, the method is dependent on engineered structures such as dams to maintain water levels. It is highly unlikely that these structures will be able to survive for the thousands of years during which the tailings will remain dangerous.

Spill Charge Against Rio Algom

In August 1993, two million litres of contaminated water spilled from a tailings site at Rio Algom's Stanleigh mine in Elliot Lake. The spill took place as a result of a power failure. Rio Algom has been charged by the Atomic Energy Control Board with one count of failure to provide appropriate training for its employees, and one count of failure to prevent the spill under "reasonably foreseeable circumstances". The radiologically and chemically contaminated water spilled into McCabe Lake.

Nuclear Awareness News is the newsletter of Nuclear Awareness Project, a non-profit environmental group based in Uxbridge, Ontario, Canada. We can be reached at Box 104, Uxbridge, Ontario, L9P 1M6, Canada, Tel/fax = +1-905-852-0571, e-mail = nucaware(at) The editor of Nuclear Awareness News is Dave Martin. These articles may be reprinted with acknowledgement.