First and likely smelliest phase of tar ponds project nears completion

Cape Breton Post
By Craig MacNeil
Fri., July 9, 2010

The Sydney Tar Ponds Agency told media Friday the south pond solidification and stabilization project had reached the 70 per cent completion mark.

"We are very happy and relieved we have just about turned the corner and finished," said Donnie Burke, project director for the STPA. "Hopefully, it brings an end to some of what we are getting in terms of odour complaints we’ve gotten to date and addressed. Personally, I think this is going to be the worst phase in terms of odours. In terms of sulphur-based odours, the majority of them would have resided in south pond."

Solidification and stabilization involves mixing cement, water and other ingredients into the contaminated material to contain and immobilize hazardous contaminants inside the cells.

Burke said 836 of the 1,200 anticipated cells in the south pond are now solidified and stabilized. Each of those cells encompasses about 200-250 cubic metres of material.

Although pleased with that number, he said 12 of 90 cells in the pond’s northeast corner did not pass performance criteria. Because all cells must pass, those 12 must be reworked over the next few weeks. "We anticipated roughly an 80-85 per cent pass rate on the first blush, so (the contractor) kind of surpassed what we anticipated and hit the 87 per cent mark."

Contractors will excavate the 12 cells that need to be reworked and crush them before remixing the material with water and cement to meet performance criteria.

Diane Ingraham, quality contracts manager for the STPA, said performance criteria includes such things as unconfined compressive strength. "The second is for permeability or hydraulic conductivity," she said. "That tells us how fast water will move through the material once it has been solidified and that is very slow."

A third criteria, known as leachate, has fluid flow through the material to see what chemicals come out the other side.

"The next phase, once a channel has been constructed, is to put an engineered cap on top of the soil the way you’d see in a landfill," said Burke. "We are hoping to see a large area this fall with top soil and hydroseed on it."

Phase 2 of remediation will then take on the north pond from the Ferry Street bridge to the narrows. "If you look at the south pond it is really in the heart of Sydney," said Ingraham, when asked about the importance of the south pond to the overall project. "It is very important for us to get it right here and then we can transfer our experience and expertise to the north pond."