The City of Ottawa is preparing to reveal what caused raw sewage to spill into the Ottawa River at Petrie Island nearly two years ago.

An investigation has revealed a malfunctioning valve at a sewage treatment plant was stuck open for two weeks, allowing sewage to seep into the river.

The malfunction at the Robert O. Pickard Centre is one of the major reasons behind elevated E. coli readings that caused the beach to close for 45 days in the summer of 2006.

"I think that city staff have some work to do in making sure that it gets out to the public that it wasn't the beach's fault, it was a problem with their treatment plant," Phil McNeely, Liberal MPP for Ottawa-Orleans told CTV Ottawa.

"We've got a beautiful beach and a beautiful park," he said. "I hope to get our reputation back."

Petrie Island became a public beach five years ago. Ottawa's three east-end councillors plan to release a statement on Tuesday that outlines how the city plans to maintain the beach's water quality.