More sewage will go into Hamilton Harbour during 2 year upgrade of treatment plant

More partially untreated sewage will spill into Hamilton Harbourover the next two years because the city is upgrading its wastewater treatment plant.

TheWoodward Avenue Wastewater Treatment Plant was "derated" this spring, meaning its capacity to handle sewage and storm water has been reduced and will stay that way until December 2021, says Andrew Grice, head of Hamilton Water. That's when crews will finish the final phase of a $315-million upgrade designed to reduce the amount of phosphorous going into the harbour.

During the upgrade,Grice said, the city will shut down some functions of the plant.That means more sewage and storm water from the city's combined sewer system will spill into the harbour.

Grice said it's not an ideal scenario, but about 99 per cent of it will be storm water.

"I don't think it raises too many alarm bells," he said. "But anything that we're putting into our harbour that is not fully treated is not something we want to do."

Both Environment Hamilton and the Bay Area Restoration Council (BARC) say sewage bypasses harm the harbour, but the upgrades to the plan will have more long-term benefits.

"It's one small step back (in terms of secondary treatment) in order to make a giant leap forward (to achieve tertiary treatment)," saidChris McLaughlin, BARC executive director, in an email.

"The need for this reduction is a bit like replacing the lead pipes to your home, where inconveniently things get all dug up and the water is shut off for the day, but in the long run the water supply to your home is stronger and safer."

Lynda Lukasik, Environment Hamilton executive director, echoed that.

"We are absolutely concerned about any situation that requires bypasses," she said, "but we also understand that the upgrades are going to have a huge beneficial impact on the harbour watershed."

Overflow from the treatment plant will comefrom the city'scombined sewer system, which means storm water mixes with what's flushed down toilets. About half of the city is on a combined sewer system.

The sewage and storm water all goes togetherto the water treatment plant, where it goes through multiple stages of treatment. When water levels are high,the plant gets overloaded, and the combined storm and sewer water bypasses part of the treatment process.

This is common in heavy rainstorms, and has been especially common this year.

Current lake levels match the record-setting levels of 2017, and the city has set up road-side pumping stations on the Beach Boulevard strip to keep water away from roads and people's properties, a city report says. Crews have also put up temporary structures to stop water from the harbour from entering the combined sewer system.

The overflow will get some treatment before it hits the harbour. It will be filtered for large particles and grit, Grice said. It'll get primary treatment with chemicals and disinfected with chlorine.

The Ministry of Environment, Conservation and Parks has approved the derating, he said.

The latest upgrades to the tertiary treatment system involves installing discs that filter out smaller particles from the water.