Sewage dump likely culprit in Yamaska River fish deaths

Dead fish are seen decomposing on a rock in the Yamaska River.

The City of Saint-Hyacinthe says it is the likely culprit in the deaths of tens of thousands of fish in the Yamaska River.

In a press release issued Monday, the city in the Monteregie made its mea culpa, admitting that work related to the expansion of its water treatment plant was the likely cause of the problem.

“This work involved a planned overflow of waste water in the Yamaska ​​River,” the press release stated, adding that due to the extremely low water levels, a high concentration of microorganisms could certainly be involved in the death of so many fish.

"There's obviously been a series of bad decisions on the part of the municipal administration," said Saint-Hyacinthe Mayor Claude Corbeil in the news release, adding that there would be an internal investigation into how it happened.

Christian Blanchette from Urgences-Environnement, who was in Saint-Hyacinthe over the weekend to determine possible causes, told CTV Montreal he is shocked.

Blanchette said the amount of sewage the city released on June 28 was equal to 8.5 million litres, which means that at the time, 10 per cent of water flow in the river was sewage.

He said both the province and the federal wildlife agency are now involved.

Sewage was released over a period of about 48 hours.

Fish were showing up dead on Thursday of last week, many in an advanced state of decomposition.