Coal mining on Cape Breton Island began over 300 years ago and has played an integral role in the economic growth of the area, employing generations of Cape Bretoners. As a result of these mining operations, there is now an extensive network of abandoned tunnels stretching from Point Aconi to Donkin, extending deep under the ocean floor off the Cape Breton coastline.
When mining operations cease, collieries flood with ground water. As the water comes in contact with the coal face, it is exposed to sulphides (mainly pyrite) contained in the remaining coal. A chemical reaction takes place where the pyrite is dissolved, releasing metals (e.g. iron, manganese, and aluminum), causing acidity that depresses the pH of the mine water. When mine water reaches the surface, a subsequent chemical reaction occurs causing the metals to become visible and the mine water to take on a copper hue.
There are twenty-six (26) recorded mine water outfalls in the Sydney Coal field, with sixteen (16) being located on Corporation property. The primary focus of the ECBC Mine Water Management Program is on the three major mine pools within the Sydney Coal field that provide the most risk of causing a deleterious discharge of mine water into the environment. The secondary focus of the program is on the relatively minor discharges that are occurring on remediated sites that are having minor effects on the environment.
The three major mine pools in the Sydney Coal field are:
The 1B Mine Pool
The 1B Mine Pool is located beneath the communities of Glace Bay, Reserve Mines and Dominion. It consists of ten abandoned and interconnected coal mines that contain more than 20 billion gallons of mine water including: The No.1A, No.1B, No.2, No.5, No.9, No.10, No.20, No.26, Lingan, and Phalen Collieries.
The flooding of the 1B Mine Pool began in 1985 with the closure of No.26 Colliery and the shutdown of the pumps in the 1B Shaft in Glace Bay. The flooding of the mines of the 1B Mine Pool concluded in April 2003, when an equilibrium position of 18 ft below sea level was reached. The 1B Mine Pool makes between 450 and 7000 US gpm depending on the time of the year and the precipitation events. The mine water elevation is controlled by a fully automated passive treatment system located at Neville Street in Reserve Mines (see attached picture). At this location, approximately 1.1 billion US gallons of net alkaline, near surface infiltration water is intercepted by drilled wells, pumped to the surface and successfully treated on an annual basis, with final discharge to Cadegan Brook.
The Sydney Mines Mine Pool (SMMP)
The Sydney Mines Mine Pool is located beneath the communities of Sydney Mines and Florence. It consists of three abandoned and interconnected coal mines that contain more than 10 billion gallons of mine water including: the Queen, Florence, and Princess Collieries.
The flooding of the SMMP began in 1976 with the closure of Princess Colliery. The current mine water elevation for this mine pool is 256 ft below sea level, it is flooding at a combined rate of 200 US gpm, and acidic metal rich mine water outfalls are predicted to occur (with no intervention) by February 2013.
The New Waterford Mine Pool (NWMP)
The New Waterford Mine Pool is located beneath the communities of New Waterford and New Victoria. It consists of six abandoned and interconnected coal mines that contain more than 12 billion gallons of mine water including: The No.12, No.14, No.16, No.17, and No.18 Collieries (Harbour and Phalen).
The flooding of the NWMP began in 1962 with the closure of No.16 Colliery. The current mine water elevation for this mine pool is 128 ft below sea level, it is flooding at a combined rate of 250 US gpm, and acidic metal rich mine water outfalls are predicted to occur (with no intervention) by July, 2012.
New Victoria Mine Water Treatment Plant
ECBC is constructing a mine water treatment plant in New Victoria, NS to treat mine water from nine mines in both the Sydney Mines and New Waterford mine pools before it reaches the surface. Active mine water treatment includes using a mechanical plant and lime to remove the metals and achieve acceptable pH levels. Further passive treatment involves flowing treated water through a settling pond and a constructed wetland before discharging the remediated water into the ocean.
The $12.5 million New Victoria Mine Water Treatment Plant project is expected to be fully operational by July 2012. The plant will have the capacity to treat 1,000 gallons of mine water per minute.