Sydney Tar Ponds, Canada

Matt Greaves and Tom Baker

Sydney Tar Ponds, Nova Scotia

• Hazardous waste site on Cape Breton Island, Nova Scotia.

•Located on the eastern shore of Sydney harbour.

•Forms a tidal estuary at the mouth of Muggah Creek.

The Problem• 100 years of steel and coke production has left more than a million tonnes

of contaminated soil and sediment in Sydney .

• The contamination centres on four sites around the former steel mill:– 1. Tar Ponds.– 2. The former Coke Ovens.– 3. Coke Ovens Brook that connects the Coke Ovens to the Tar Ponds.– 4. An abandoned municipal dump.

• The Coke Ovens Brook picks up contaminants and transports them to the Tar Ponds and the harbour.

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The Tar Ponds

• The 31-hectare site contains 700,000 tonnes of contaminated sediment.

• The contaminants:– Heavy metals– Polycyclic aromatic hydrocarbons (PAHs) complex organic compounds.– 3.8 tonnes of polychlorinated biphenyls (PCBs)– 13 million litres of sewage emptied into the Tar Ponds daily

• Heavy Metals– Lead, Arsenic, Copper, Thallium, and Zinc.

• PAHs – Bind tightly to sand and mud. – Do not dissolve readily in water Little movement of Tar Ponds sludge.

• PCBs– Not readily broken down in the environment

– Stick to organic particles and bind strongly to soil.

Previous Solutions Attempted• In 1986, Canada and Nova Scotia signed a $34-million agreement.

– The plan was to dredge the Tar Ponds and pump the sediment through a mile-long pipeline to an incinerator that would generate electricity.

– Hydro sales would offset cleanup costs. – But the thick, lumpy sludge repeatedly clogged the pipeline. – By 1994, rising costs triggered a premature end to the project in 1995.

• In 1996, Nova Scotia government proposed a plan to bury the Tar Ponds under slag procured from the steel mill.

– However, the project had attracted local critics, who condemned the plan.– Federal and provincial ministers called for a public consultation process to

search for a solution.

Previous Solutions Attempted• In 1999, the highly empowered community group called Joint Action Group

(JAG) was set a mandate to seek consensus around cleanup options. – JAG held more than 950 public meetings however, no clear consensus on

cleanup technologies emerged.

• In 2004, the Governments of Canada and Nova Scotia announced a 10-year, $400 million CAD plan to clean up the Sydney Tar Ponds and Coke Ovens.

Current Solution• Prevent further environmental damage by re-routing the Coke Ovens Brook

to prevent contamination.

Current Route Re-routed Brook

Current Solution• Isolating the Coke Ovens Brook from the Tar Ponds by parallel sheet piles.

Clean Water Sheet Piles

Current Solution• Construct cofferdam to prevent contaminants flowing into the harbour.

Current Solution• Dealing with the PCBs:

– Dig up PCB material– Dry material and send off site for high temperature destruction.– Carried out at temporary incineration plant 3yrs to destroy all of it.

Current Solution• Stabilise and Solidify remaining material

– Augers drill into the sediment and mix it with Portland cement powder.– Increasing the soils structural strength.– Stabilising the contaminants to prevent leaching.

Current Solution• Containment

– Cover the Tar Ponds with an engineered capping layer.– 1. Layer/barrier of clean fill– 2. Layers of drainage material– 3. Topsoil

Future Use• No decisions have been made as to the future use however here are some

proposed uses:

Local park with various walking trails

Recreational and multipurpose sports fields.

Thank you