Shannon Miedema

The city's environmental performance officer, Shannon Miedema, says the diesel leak at a Metro Transit garage is a "really weird fluke." (CBC)

Cleaning up a 200,000-litre diesel fuel leak at the Metro Transit garage in Burnside is expected to cost $1 million, but whether insurance is going to pay for it remains unknown.

The cleanup involves removing and replacing a 220-metre water main that's sitting in a pool of diesel, and excavating the old site of the underground storage tanks.

Excavating the storage tanks will begin on Monday, as will further tests to determine the extent of the leak. It's expected work to remove the water main will begin the week of June 30. 

The origin of the leak stems from the decision to connect piping from underground tanks to above-ground tanks.

"When the... underground tanks were pulled out in January 2013, not all of the old system was capped off, tied off, removed," says Shannon Miedema, the city's environmental performance officer.

In December 2013 or January 2014, a valve sealing off the old system failed. The leak went unnoticed and fuel followed the routing of the water line, showing up in a culvert a kilometre away at a car dealership on Windmill Road.

The leak was detected April 9 and was traced back to the Metro Transit garage on May 21.

To date, more than $200,000 has been spent on the cleanup, while $180,000 of diesel fuel was lost in the leak.

The lost diesel represented 2.5 per cent of the fuel used during the suspected leak period.

Miedema said Metro Transit officials have told her the leak went unnoticed because the fuel sensors on the above-ground storage tanks were not tripped and fuel consumption during a busy and cold winter season was high.

"Through a series of unfortunate errors or oversights... and the fact those systems were tied together, we have this problem," said Miedema.

"It's a really weird fluke."