Spring rains too much for sewage plant, as city surpassed treated solids standard

The city spilled so much treated solids into Hamilton Harbour during May's rainstorms that it broke a regulation it's complied with for more than 11 years.

And if Hamilton saw another intense rainstorm,there's a risk of it happening again, as the heavy spring rains have left abig part of the system's safeguards out of commission.

For 11 and a half years, the city has met Ministry of Environment standards to only expel 10,225 kilograms of "total suspended solids" into Hamilton Harbour. In May, when Hamilton had bouts of major flooding, 10,540 kilograms flowed into the harbour.

The infraction was small, and weather conditions caused it, said Andrew Grice, director of Hamilton Water. But workers were still disappointed.

"They were very, very proud of that 138 month compliance record," he said.

May dumped so much rain that Lake Ontario levels are the highest in 99 years, and parts of Hamilton are still underwater. That includes three combined sewer overflow tanks, which hold sewer and wastewater in waiting when the treatment plant is at capacity. The tanks are unusable until that water subsides, meaning there is little margin for safety if there is another significant storm.

"We're just waiting," Grice said. "This is the first time we've had lake levels that high. We're very curious, and we're watching them very closely."

Here's how the overflow happened:

In a rainstorm, underground pipes sendstormwater and effluentto the Woodward treatment plant.

There, the material is treated through numerous tanks. If the plant reaches capacity, and is at risk of sending untreated effluentinto the harbour,stormwater is held back atup to sewer overflow tanks around Hamilton. When the volume goes down at the plant, the combined stormwater and effluentin the tanks is released to make sure it gets treatment before discharge into the bay.

The city always expels some treated waste into the harbour. In this case, it expelled more than the province allows.

The ministry is working with the city to make sure it takes appropriate action, said spokesperson Gary Wheeler in an email.

Meanwhile, there's the issue of the combined sewer overflow tanks. With the tanks underwater, the system is at reduced capacity. And all the city can do is wait for the water to subside.

That makes Hamilton vulnerable should substantial rain fall in the meantime, Grice said.

"We can handle a long, slow storm that goes throughout the day," he said. "Where we run into trouble is like we did in May."

Lake Ontario levels are at 75.8 metres, the city says, compared to 75.09 metres in May 2016.

Overall, storm damage has cost the city between $4.5 million and $6.8 million so far, said a staff reportlast week.

Some of those costs are as follows:

• Parts of the Waterfront Trail from Bayfront Park to Princess Point remain closed, and some of the shoreline has eroded. Expected cost: more than $1 million.
• The city closed parts of the Escarpment Rail Trail, although it's since reopened them. Four areas are still marked for safety reasons though. Cost: unknown.
• Parts of Beach Boulevard and Hamilton's beach trail are still flooded, and the city is pumping water off roadways to reduce basement flooding. It's also doing remedial grading work and a drainage study of the area. Cost: about $700,000.
• The city restored a shoulder and culvert along York Road. Cost: $350,000.
• High water levels dislodged trees, exposed roots and eroded Confederation Beach Park. Cost: as much as $600,000.
• Crews demolished a viewing platform at Fifty Road Parkette after high water levels damaged it. Cost: up to $600,000.
• High water levels hindered a project to stabilize the bank of Chedoke Creek. Cost: $700,000.

samantha.craggs@cbc.ca | @SamCraggsCBC