The company ordered to shut down work at a major construction site in Dartmouth, Nova Scotia, Canada is defending its preparations to deal with silty runoff.

Steady rain over the weekend caused muddy water at the $270-million Dartmouth Crossing shopping complex development to flow into nearby streams and lakes, including the historic Shubenacadie Canal.

The provincial Environment Department stepped in and imposed a stop-work order until the problem is fixed.

Mark Van Zeumeren, a senior engineer from Environmental Design and Management, says it cost the company hundreds of thousands of dollars to build the runoff containment system at the sprawling construction site.

He also says there's less runoff now than during previous decades, when a quarry occupied the same location.

"We've had orders of magnitude improvement in terms of how much siltation is coming off the site, in terms of erosion, over from when the developer first bought the site," he said.

Van Zeumeren says the containment pools were designed to deal with 105 mm of rain in one day. Last weekend's storm dumped 150 mm of rain in three days. According to Environment Canada, that was a freak event that might not be repeated for decades.

Rick Scott, a runoff and siltation expert at Dalhousie University's Center for Water Resources Studies, says that kind of rainfall is nearly impossible to prepare for.

"With any exposed soil in 150 mm of rain, you're going to have an impact. There's no way of getting away from it," Scott said.

Van Zeumeren says he welcomes the current investigation by the Environment Department. He says his company went beyond the province's guidelines, "and in terms of damage to the environment, it's murky water, it's sediment. There's no contaminants coming off that site."

Construction crews are already working to build higher embankments and larger holding ponds. Van Zeumeren hopes the changes will allow the multimillion-dollar project to resume soon.

Source: CBC