Hamilton discovers potentially toxic fill atop the leaky Kenilworth drinking water reservoir

The city says there is zero risk" to Mountain drinking water from polluted soil sitting atop the Kenilworth reservoir even though past inspections identified leakage" of outside water into the aging underground tank.

A city contractor found soil laced with benzo(a)pyrene while digging last summer ahead of repairs to the 56-year-old reservoir that stores drinking water for tens of thousands of Mountain residents. Further tests showed varied levels" of pollution in 15,000 tonnes of soil atop the massive tank buried above the Kenilworth access. In some cases, the amounts were six times higher than what the province allows.

Benzo(a)pyrene is created by burning coal or gas in industrial processes like steelmaking and is often found in old fill dug up in the lower city. Ontario is introducing new air pollution rules to tackle the cancer-causing carcinogen.

The city is still studying what to do with the polluted soil, which has sat atop the reservoir since it was built in 1964. But city water director Andrew Grice told councillors Wednesday there is zero risk" to the city's drinking water.

He described the reservoir as a sealed concrete vessel" and stressed that recent tests show the water in the reservoir is clean and free of benzo(a)pyrene. Those tests will continue throughout the reservoir repairs.

A city consulting report from Jacobs Engineering also noted the pollutant does not mix easily with water and is unlikely" to migrate very far. It's been sitting there for almost 60 years," said associate medical officer of health Dr. Bart Harvey during a meeting Wednesday. It doesn't pose a risk to the health of the public."

But Grice also acknowledged the city has not regularly tested the reservoir in the past for benzo(a)pyrene - although staff are now studying whether to change that policy.

And online bid documents for the reservoir repair project indicate past inspections identified leakage" of outside water into the 150-million-litre reservoir through damaged expansion joints.

As the reservoir contains potable water, the amount of external water infiltration is of concern," notes a 2018 condition assessment that spurred the current repair project.

Grice could not say if the past problem leaks spurred extra reservoir water testing in or before 2018, but he said benzo(a)pyrene has never showed up as a concern in Hamilton's drinking water.

Harvey conceded there could have been a minute risk" of past contamination through damaged expansion joints. But there is no reason to suspect at a previous time levels of benzo(a)pyrene in the water were greater than what were found in late August."

Regardless, it is worrisome to have tonnes of potentially toxic soil sitting directly on your reservoir," said Coun. John-Paul Danko, who represents the west Mountain.

Coun. Tom Jackson, representing the East Mountain, agreed, adding his strong inclination" is to remove the 15,000 tonnes of polluted fill. He put forward a motion with Coun. Sam Merulla asking for a report on options and costs as soon as possible.

Other councillors asked why they only learned about the issue in November when the extent of the pollution was clear in August. Public works head Dan McKinnon said he was still collecting relevant information in October and didn't want to come to council with half a story."

Digging up and trucking all of the soil to a hazardous waste landfill would likely cost around $6.5 million, said Grice.

Jacobs Engineering has suggested the city can legally reuse some - or maybe all - of the soil on the city reservoir site based on the severity and type of contamination. But the consultant that did the summer soil testing for the city, Sirati and Partners, recommended the soil be removed and replaced with clean fill.

The provincial Ministry of Environment, Conservation and Parks is aware of the pollution and has asked the city for a soil management plan," said spokesperson Jennifer Hall.

That plan includes safety measures to protect workers repairing the reservoir, coverings for the contaminated piles and security for the site, which is already fenced and off limits to the public.

No orders have been issued to the city, she said. But if further testing shows a risk of the pollution escaping the property, the ministry may require the city to take additional action."

It's not clear how the dirty fill ended up on top of the reservoir, but the facility was built in an era with little regulation of how polluted soil was used. Truckloads of toxic PCBs were also found earlier this year during excavation at the city's sewage plant.

Matthew Van Dongen is a Hamilton-based reporter covering transportation for The Spectator. Reach him via email: mvandongen@thespec.com