Tar Ponds Q & A

By Tanya Collier Macdonald
Cape Breton Post
Mon., Feb. 5, 2007

SYDNEY - Now that the $400-million cheque is signed, some local residents are experiencing renewed interest in the tar ponds cleanup. The Cape Breton Post sat down with Frank Potter, acting chief executive officer of the Sydney Tar Ponds Agency, to get some answers to some questions expressed by the community since last Sunday's announcement. Following is a summary of that interview.

Q: How do you solidify 700,000 tonnes of toxic sludge?

A: The tar ponds will be drained leaving damp, muddy sediment. A carefully crafted cell about the size of a soccer field will be constructed to hold material excavated from portions of the site. Sediment will be mixed with cement and aggregate in a phased approach. Slag from Sysco will be added to give it some extra muscle. The current recommended cap strength is 20 psi (pounds per square inch) but that may change with further testing.

Q: Will there be emissions during the work?

A: When pilot-scale testing was conducted at the tar ponds in 2006, air samples taken from many monitors positioned throughout the site showed little emissions. What might make a difference during the cleanup is the chemical reaction between sewage, sediment and the concrete mixture. If there are emissions, water will be sprayed on the material to keep odour levels low. Most solidification and stabilization can be done in the open.

Q: How will you prepare the coke ovens site for capping?

A: Brooks will be redirected through channels and barrier walls will rise from the bedrock to intercept groundwater. The water will move along a French drain until it clears the site. Leachate from contaminated coke oven soil will be treated at a water treatment plant working to filter collected hydrocarbons.

Q: How will you determine what nixture works best?

A: In the near future, about 12 mixtures will be assessed. The right mixture will be the one that eliminates all soft spots. However, the final product won't be one solid, hard mass. If a pick was used against it, pieces would break free.

Q Why do you need a landfill?

A: We expect to find debris, like shopping carts, in the ponds. They will be cleaned, then sent to the landfill.

Q: What if residents need to be evacuated?

A: If the absolute unexpected were to happen, there is a contingency plan in place and a master health and safety plan. All emergency personnel in the area will be familiar with the project and will be notified when work is happening at the sites.

Q: Could the tar ponds ignite?

A: Most of the volatiles are gone. What's left today is difficult to ignite. However, the Cape Breton Regional Municipality's Hazmat team is also trained and equipped to handle emergencies.

Q: What if there is an earthquake?

A: There are no fault lines in the area that would give rise to an earthquake. However, if the project was hit, toxic material will be solidified so it won't seep through cracks. It's not going to be one big mass. It can tolerate a bit of movement.

Q: What if an asteroid hits?

A: The last thing that will be on everyone's mind is the tar ponds.