Contaminants in Chedoke Creek are the same as before 24-billion litre spill: consultant

The contaminant levels in Chedoke Creek are no worse than they were before 24 billion litres of sewage and stormwater spilled into the creek, a new report says. And dredging won't help. 

A report from SLR Consulting says it's hard to know if there was any long-term environmental damage done by a partially opened gate at a combined sewer and stormwater tank. The spill went on from 2014 to 2018, when the city discovered the problem.

Levels of toxins such as metals and nutrients are comparable to the time before the spill, said Gord Wichert of SLR. As for the contaminants there, it's impossible to know what resulted from the spill and what stems from the routine battering the creek takes from the urban area around it.

While an earlier expert report recommended dredging, SLR says that would only stir up existing contaminants. 

"You're actually doing more harm than good by dredging," said Mayor Fred Eisenberger after the report. The bigger message, he said, is we have to treat Chedoke Creek better overall.

"The damage [of the spill] is more reputational than it is environmental … I think lesson learned is we'll continue to work on our system."

The province ordered the city in November to hire a consultant to do an ecological risk assessment. SLR presented the Chedoke Creek assessment this week. A Cootes Paradise assessment is due May 1.

The city has received three provincial orders since August 2018. 

An earlier report says the gate issue released about 4,266 tonnes of contaminants into the waterway. It breaks it down like this:

• 2,375 tonnes of solids.
• 47 tonnes of phosphorus.
• 159 tonnes of ammonia.
• 312 tonnes of nitrogen.
• 1.373 tonnes of carbonaceous biochemical oxygen demand.

Wichert couldn't say where it all went, but levels of metals and nutrients were low to negligible in fish, amphibians and benthic invertebrates living in the creek. Levels of polycyclic aromatic hydrocarbons were moderate in fish and amphibians, and in some spots, high in benthic invertebrates.

Chedoke is polluted on a regular basis, whether it be from Highway 403 that runs alongside it, sewage and stormwater that flows from cross-connections farther up the Mountain, and fairly routine overflows of the city's combined sewer and stormwater system.

The city, which has done $494 million in capital improvements in recent years, should take this as a cue to step up, Eisenberger said.

Maureen Wilson, Ward 1 (west end) councillor, agrees.

"We've really got to start paying attention to the watershed," she said. "We've really got to start paying attention to those upper creek sources of contaminants."