Addressing immediate concerns

Controlling Arsenic Loadings to the Moira River

When the ministry took control of the site, the most pressing concern was the arsenic leaching into the Moira River and the potential threat it posed to the environment and to communities downstream. The goal was to address the immediate sources of contamination and to reduce runoff to the Moira River. The ministry focused its initial efforts on upgrading the existing wastewater plant. Plans were developed for the creation of a new arsenic treatment plant, and by 1983 the collection, storage and treatment facility was in operation. Additional pumping stations were installed in 1984 and 1985 to collect groundwater from other contaminated areas. Containment and leachate collection facilities established by the ministry are now operated on contract by the Ontario Clean Water Agency.

Demolishing Contaminated Buildings

The ministry also tackled other major sources of arsenic on the site. A number of contaminated industrial buildings, used for collecting and processing arsenic in the smelting days were demolished. The areas where these structures stood were regraded and seeded.

Covering 'Red Mud' Tailings

Eight hectares of red mud tailings, the arsenic contaminated byproduct from the smelting process, were covered to a depth of 0.5 metres with approximately 76,000 tonnes of crushed limestone in order to eliminate wind and surface water erosion, elevate the pH of the tailings and stabilize the containment dams.

Monitoring Surface and Groundwater Quality

An extensive sampling network is in place to monitor surface and groundwater quality at the Deloro site. A series of collection stations on the Moira River and Young's Creek provide information on surface water, while monitoring wells on the property are used to assess groundwater contamination. Depending on the location of the sampling station, samples are taken hourly, daily, weekly, monthly or quarterly. Water is also carefully monitored as it enters and leaves the treatment plant.

Ongoing monitoring shows that arsenic concentrations in the Moira River have been substantially reduced since the ministry took control of the site. In 1979, the annual average of arsenic escaping into the river was 52.1 kilograms a day. Since the arsenic treatment plant was put in operation in 1983, the arsenic going into the river has been reduced by more than 80 per cent, to an average amount of less than 10 kilograms a day.

Creating the strategy for cleanup