Field testing to begin on containing tar ponds

By Erin Pottie
Cape Breton Post
Sat., Sept. 6, 2008

Sydney - Areas of the highly contaminated tar ponds will one day be too hard for a shovel to break, according to experts set to begin field testing of the prominent remediation project.

Six recipes with varying amounts of fly ash, cement and slag will be mixed into a section of the north tar ponds next week, with the south pond testing to be completed in November. Officials with the Sydney Tar Ponds Agency hope to find two acceptable recipes as they prepare to contain the hazardous material next summer.

Donald Shosky of Earth Tech AECOM provided a technical briefing to local media at the tar ponds agency office, Friday. He said the solidifying mixture has to have a certain strength and hardness and it can only allow water to percolate through it at a very low rate. The appropriate level of hardness would allow an excavator to break the surface, yet allow the material to be driven over and built upon.

Bench scale testing, or lab testing, of recipes has already been completed. Work on-site now involves the construction of six sheet pile cells or work zones to allow contractors to mix hardening recipes with contaminated sediment.

Shawn Duncan, environmental regulatory manager with Earth Tech, said the tests will undergo a provincial approval process this fall and winter.

Previous lab results show appropriate performance levels of hardening, strength and containment of hazardous materials, including PCBs, according to experts. However, it was decided further testing would be carried out to further validate those findings. "It's just a scientific process that you go through. You have some recipes that some people thought would pass that didn't pass that were a bit of a surprise," said Shosky.

In August, concerned citizen Marlene Kane filed a freedom of information request after failing to receive a copy of earlier tests listed in the Tar Ponds Bench Scale Treatability report.

The report was expected to be released in January, but Kane said she finally received a copy Friday. She is also still seeking some of the scientific data missing from a cooling pond report, originally released upon completion of the project in April. The cooling pond has been capped using a different recipe than the ones being tested in the tar ponds, with slag at 50 per cent and cement at 12-15 per cent. The remainder was sediment.

The tar ponds and coke ovens cleanup project dates back to the 1980s. It is easily the most prominent remediation project in Canada after nearly 100 years of steel and coke production left behind more than a million tonnes of contaminated soil and sediment located within four sites around the former steel mill.

In order to carry out the solidification and stabilization process of the two ponds, surface water controls will be used to redirect surface water flows and outfalls away from the area when the actual project is taking place.

Surface water controls will be in the form of temporary pumping stations and in the construction of permanent channels through the tar ponds. The new channels will be permanent and used to bring water from Coke Ovens Brook and Wash Brook from their current entry points in the south tar pond to Sydney harbour, as well as existing flow from existing sewer outfalls.