The City of Peterborough, Ont., says surface water testing in Little Lake last week came back negative for petroleum hydrocarbons following cleanup efforts of the latest oil sheen earlier this month.
The sheen at the outlet of Jackson Creek which flows into the lake was first reported on March 16, prompting extensive cleanup and containment by city public works, private contractors and the Ministry of the Environment, Conservation and Parks.
The city says cleanup and monitoring efforts continue but that no further contamination has been found flowing into the creek.
“Based on the conditions in Jackson Creek, it appears that no additional fuel is being added to the oil sheen on Jackson Creek — that the source of the contamination has stopped,” the city said Monday afternoon.
That source, however, has still yet to be determined. Provincial officials last week said the sheen was “possibly” historic contamination from the city’s transit yard on nearby Townsend Street.
The city notes there is known historical contamination in the area including its own property.
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“Based on the limited nature of the contamination, that does not appear to be continuing. One possibility is that the oil sheen is residual or remaining from the contamination last summer and fall that was caught upstream over the winter,” the city said.
August 2022 cleanup
The city faced a similar oily sheen scenario in August 2022. Following cleanup, the city conducted a geophysical survey of its property that discovered a “previously unidentified buried tank.”
The city said the tank was removed as part of the precautionary remediation efforts. Last fall and winter, a permeable reactive barrier was installed on city property to “capture and remediate any potential contamination.”
The city and Peterborough Public Health noted the city’s water supply is safe since it is drawn upstream and treated.
The health unit also advises anyone downstream of Little Lake to report any oil sheens or fuel odour.