August 1, 2008

TransAlta plans new dyke wall for lagoon at Keephills power plant

CALGARY

A dyke wall holding back a pond full of ash slurry from TransAlta Corp.’s coal-fired Keephills power plant is in danger of breaching, the Calgary-based company said ealier this week.

TransAlta workers found a crack in the lagoon’s dyke wall during a routine check and contacted Alberta Environment and local authorities.

“The company’s primary concern is to maintain safety and minimize environmental impact,” TransAlta said in a statement.

The lagoon contains between 1.5 million and two million cubic metres of water, TransAlta spokesman Michael Lawrence said.

A second dyke wall is being constructed to redirect any overflowing slurry away from a nearby highway and fresh-water pond and into another lagoon on site.

About 15 per cent of the coal burned at Keephills remains after the combustion process in the form of ash, Lawrence said.

“That ash is collected, mixed with water and then pumped into this ash lagoon, or treatment system. The ash particles are removed by settling or flotation,” he said.

“Eventually that water is recovered and recycled right back into our plant.”

Lawrence said the ash lagoon is nothing like the toxic tailings ponds found at oilsands mine sites, one of which was blamed in the deaths of 500 ducks near Fort McMurray, Alta., earlier this year.

“Waterfowl do co-exist with it,” Lawrence said.

But Pembina Institute policy director Chris Severson-Baker said the residual ash left over from burning coal contains dangerous compounds.

“Probably the main thing to be concerned about would be heavy metals, which can accumulate in the food chain and can pose a risk to ground water quality,” he said.

Alberta Environment is working with TransAlta to get a handle on the situation and to mitigate any effects of a potential spill.

“We also work with them to ensure that whatever actions are taken are within their approvals and also to follow up on any necessary investigation that might happen afterwards,” ministry spokeswoman Cara Van Marck said.

There are a “handful” of landowners nearby, only one of whom is expected to be severely affected by a spill, Van Marck said.

In the meantime, access to the site was restricted.

“They have TransAlta staff on the highway just in case something happens before they finish these construction activities,” Van Marck said.

Alberta has been experiencing a very wet summer so far, and heavy rainfall in recent days could be one reason for the crack.

Canadian Press

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