Prince Edward Island’s environment minister is defending the mitigation measures put in place to stop silt runoff from the controversial Plan B Trans-Canada Highway realignment project after sediment ponds overflowed during heavy rains on Tuesday.

The Opposition said Janice Sherry should charge Transportation Minister Rob Vessey for contaminating the West River, but she was quick to defend the mitigation measures in place.

"All of the things we have done in the process in order to prevent any sort of issues like this have been many. The dream, the wish, the hope is to put enough mitigations in place that these things don't happen," Sherry said on Thursday.

She said there was a similar runoff problem in January and an expert was brought in from Nova Scotia to recommend other measures.

"Still breached. Of course we don't want to see that happen, but we can't control the weather," said Sherry.

'Of course we don't want to see that happen, but we can't control the weather.' —Janice Sherry

But Megan Harris with the West River Watershed Project said they warned government these types of runoffs would happen.

"Rain storms that we get are more intense. But that means we really need to change our game across the board. This is just an early warning that will continue to happen if we don’t change the way we do things," she said.

Harris said the silt is a harmful substance.

Opposition leader Steven Myers said Sherry should charge Vessey with contaminating a watercourse.

"What’s she saying every time we have a heavy rain this is going to happen and we’re just going to have to deal with it? I mean that’s not an acceptable answer," he said.

"Clearly this has happened. It’s a breach, there’s silt in the water down there and the Department of Transportation should be charged by the Department of the Environment."

Sherry denies the runoff is a contaminate.

The realignment project, which will reroute the highway west of Charlottetown and widen the bridge in Bonshaw to three lanes, will cost an estimated $20 million, to be split evenly between the federal and provincial governments.