It took nearly a month for an Etobicoke man to find out that it was shale sediment that was turning the water in Mimico Creek a murky, grey-green colour.

“It’s great they’re finally getting to the bottom of it,” Craig Strathy said. “But it’s absolutely crazy it has taken this long.”

Ministry of the Environment, Conservation and Parks (MECP) spokesperson Gary Wheeler confirmed the cause Tuesday.

“We have confirmed the water in Mimico Creek was discoloured by mud from nearby construction,” Wheeler said in an email. “The shale/rock sediment in the mud can change the colour of the water from grey to green.”

Wheeler added that while the ministry takes all threats to the environment “very seriously,” it has no concerns at this time.

“The ministry has no environmental concerns at this point and staff remain engaged with Toronto Water and the Ministry of Transportation to follow up on site conditions and cleanup efforts,” Wheeler said in an email.

The ministry’s role is to respond to concerns, assess any environmental impacts caused by such incidents and ensure the appropriate and responsible agencies clean up the spill or site, Wheeler said.

Toronto Water initially took over responsibility for site cleanup, Wheeler said.

However, the Ministry of Transportation is working on the cleanup and monitoring of the area after it was determined to be an MTO outfall, Wheeler confirmed. In this case, the outfall is a concrete structure that drains water from the highway into the creek.

Lawson Oates, City of Toronto director of environment and administration, said Monday the city joined the MECP response by installing a containment boom, or temporary floating barrier, to block solid debris at the outfall, as well as straw bales covered in filter material.

“We’re always concerned when we get a call about a (possible) spill in our streams, rivers or sewers in Toronto because of the impact on the natural environment, including aquatic life and ducks,” Oates said. “Lake Ontario is also the source of our drinking water. We’re always concerned about any degradation of our water system.”

Oates said two separate incidents in January contributed to the green discoloration in the creek; the first work on Jan. 3 related to Metrolinx construction, the second work on Jan. 15 related to an MTO contract.

The work “involved some shale, which has a green sheen to it,” Oates said. “Some of that material is captured and some of it is carried on (in the water).”

It remains unclear what events may have led to shale being deposited in the creek and turning it green in December.

Metrolinx spokesperson Scott Money was not able to confirm that Metrolinx was on site Jan. 3 and contributed to the shale in the water, and, in fact, stated in an email that the cause of the contamination was still unclear: “We understand that there has been no definitive determination as yet regarding the cause of the discoloration in the Mimico Creek.”

“We will continue to work with MECP and all partners, including the City of Toronto, to ensure that works are being carried out carefully and with no local effects.”

The Ministry of Transportation deferred for comment to Gary Wheeler, who was not able to confirm whether the MTO was on site on Jan. 15 before our publication deadline.

Meanwhile, heavy rains about a week ago seem to have diluted the murky, grey-green colour of the creek in that area.

As for Strathy, he first noticed Mimico Creek’s strange colour over Christmas break during regular walks in West Deane Park with his sheltie, Colby.

“One day, the creek would be crystal clear and then the next day, it would be a murky green,” Strathy said.

After Strathy noticed it a third time, he walked the creek trail from West Deane Park to identify the source of the discoloration.

Loading... Loading... Loading... Loading... Loading... Loading...

He took photos. That day, Jan. 4, he called the city’s 311 and the MECP Spills Centre.

“On the south side of Eglinton, I noticed a five-foot concrete outfall where this milky substance was coming from and then entering our natural watershed,” Strathy said.

MECP will continue to monitor the site to ensure the clean up is completed, Wheeler said.