The general manager of the Greater Moncton Wastewater Commission says a huge illegal dumping of a heavy oil product is proving costly for the city.

On May 29, a substance later identified as likely a diesel product was detected in city sewers.

Bernie LeBlanc says the clean up of the massive spill has taken more than a month and has cost the city more than $54,000 to complete.

"We can't tell how much was spilled, but what we can tell is how much we had to dispose of," he says.

"The combination of petroleum and other waste water came to a total of over 90,000 litres we had to dispose of. As well we had to accumulate and capture the solid portion, about 13 metric tonnes of solid as well, so it was quite a significant amount of contaminated product we had to dispose of."

Manhole cover lifted off

The commission is urging anyone who becomes aware of illegal dumping into the sewer system to contact the GMWC or the Department of Environment. (CBC)

LeBlanc says the spill happened in eastern Moncton, but whoever did it is not likely to be caught.

"Our challenge is in terms of where it came from," he says. "We can try to trace back through our collection network or piping system, but we went as far back as we could and noticed that it came from the eastern area of Moncton."

Not being able to trace the exact source also makes it difficult to determine if the spill was accidental or on purpose.

"Without GMWC personnel's quick action in addressing the situation and retaining the contaminant within its system, there would have been a release directly to the Petitcodiac River, thus a significant pollution and environmental risk," he says.

Leblanc is urging anyone who becomes aware of illegal dumping into the sewer system to contact the Greater Moncton Wastewater Commission or the Department of Environment.