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Odour on Friendship Trail temporary result of pumping station construction

13/06/14 — An unpleasant odour on the Friendship Trail is coming from groundwater that is being pumped to the surface while the sewage station on Dominion Road is being built.

Hydrogen sulfide occurs naturally in the groundwater in the area, said Graeme Guthrie, project manager for the Region’s wastewater division.

“We would normally find it in sewers but this has nothing to do with sewers,” he said.

Sulfur is found naturally in the environment and hydrogen sulfide gas is often associated with either natural gas deposits or as a product of the decomposition of plant material.

It’s commonly called sour gas, sewer gas and swamp gas and has a distinct odor of rotten eggs (which also contain sulfur) that is easily detectable by smell in very low concentrations. In high concentrations it is toxic and explosive.

Ironically, the concentration of the gas in the groundwater exceeds the Ministry of Environment’s limit for release to surface water.

The groundwater must be treated before it goes into the stream that feeds into May’s Creek and further on to Lake Erie, Guthrie said.

The groundwater is pumped into a ditch and aerated with large volumes of compressed air. The air bubbles capture the gas which is released into the atmosphere.

Since the gas easily escapes the water, if not aerated at the source, it would cause odours near homes downstream and along the lakeshore.

The groundwater itself is a problem for construction and has caused the project to be set back by a couple of months, Guthrie said.

The concrete structure that will house the machinery is being built to a depth of 10 metres underground.

“It’s a big, hollow structure,” he said. “We’re basically pumping to keep the water down until there’s sufficient weight on the building to stop it from floating.” At that point, the odour will stop.

The entire $7.2 million project, which includes the pumping station itself and a force main that goes up Albany Street to Alfred Street to DiPietro and ties in to a gravity main on Murdoch Street, is expected to be completed by the end of January.

When the station comes on stream, it will be able to pump 255 litres of sewage every second compared to 225 litres per second by the existing station.

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