5 more former N.S. mine sites to be assessed for contamination

The Nova Scotia government is taking its first steps toward cleaning up five more sites in the province that were contaminated by historical mining — Gold Brook Lake, Seal Harbour, Lake Enon, Mooseland mine and the former steel plant on Ocean Street in Sydney Mines.

Nova Scotia Lands, the provincial Crown corporation responsible for remediation of Crown properties, posted notices last month seeking companies to study the five sites and come up with remediation options for each.

The work will involve pinpointing the sources of contamination, what contaminants are present, in what quantities and exactly where — in soil, groundwater, surface water and sediment — and what the human health and ecological risks are.

The plans are part of a much larger, multimillion-dollar project to remediate dozens of sites across Nova Scotia that were contaminated by mining activities dating back to the 19th century.

The province has identified 68 sites it plans to assess and remediate, if remediation is necessary. The two sites believed to be most contaminated, Montague Gold Mines and Goldenville, have already been assessed and will cost an estimated $60 million to remediate, though that estimate is expected to rise.

Nova Scotia experienced a gold rush in the late 1800s, and since mining and processing weren't subjected to environmental regulations at the time, contaminants such as arsenic and mercury were simply dumped on land or in waterways. That contamination persists to this day.

Gold Brook Lake and Seal Harbour

Gold Brook Lake and Seal Harbour, both about 85 kilometres west of Canso, were home to gold mining and milling operations beginning in the late 1800s.

The high concentrations of arsenic and mercury are located on Crown land as well as some adjacent, privately owned land.

In the Upper Seal Harbour area, mine tailings were deposited directly into Gold Brook, and can be seen on the floodplain at least four kilometres downstream of where the mill was located, according to the tender. Arsenic and mercury have been found in sediments in the brook and are most likely also present in the sediments of Seal Harbour Lake.

In the Lower Seal Harbour area, mining took place between 1905 and 1942, and tailings from the stamp mills and a cyanide plant used to treat the ore were discharged into a tributary to West Brook, which flows into Seal Harbour. Tailings are visible for the two kilometres from that mine site to the ocean at Seal Harbour.

Seal Harbour and nearby Isaacs Harbour have been closed to most bivalve shellfish fisheries since 2005 due to high levels of arsenic found in clam tissue.

Lake Enon

The Lake Enon site, about 50 kilometres southwest of Sydney, is also known as the Kaiser Celestite mine because the mineral celestite was mined and refined there from the late 1960s until 1976. After that, the mill was used by various companies to process lead ore, barite ore and magnetite.

The buildings and equipment were removed in the mid-1990s, but the tailings area remains.

The current chemistry of the tailings is not known, but a 1995 report identified "potential for issues relating to PCBs," and elevated lead levels have been found at the site.

Mooseland mine

The former Mooseland gold mine is about 24 kilometres north of Tangier, and operated from 1861 to 1934, though further exploration has since taken place. 

Tailings, which were dumped into Sluice Brook or directly into the Tangier River, contain arsenic and mercury.

About 3.5 hectares are believed to be potentially contaminated with 8,217 tonnes of tailings.

Ocean Street

Mining took place in and around this site along Ocean Street in Sydney Mines from the mid- to late 1800s until the mid-1900s, and the site has been home to coke ovens, coal-washing plants and the Scotia Steel plant, which operated from 1904 to 1920. 

The site now contains "significant remnants of slag piles, crumbling building foundations, coaly waste rock, and an approximate area of 15,126 m² coaly mine tailings," according to the tender.

A 2009 study found the possibility of environmental contamination in soil, groundwater and surface water from heavy metals, PCBs, and other substances, and soil testing has found elevated levels of uranium, lead, barium and cadmium.

The tender notes that the Ocean Street site is situated among residential developments in Sydney Mines, and portions of the property are used extensively for recreational activities such as walking and off-road vehicle use.

Initial reports containing site histories and identification of potential contaminants are expected by the end of March, while the proposed remediation methods and cost estimates are expected by October.