Photo: The Canadian Press. All rights reserved.

Members of the Enbridge panel Barry Callele, left, and Peter Wong answer questions at the Joint Review Panel looking into the Northern Gateway Pipeline in Prince George Wednesday, Oct. 10, 2012. THE CANADIAN PRESS/Jonathan Hayward

The ability to detect leaks along the proposed Northern Gateway pipeline won't be known until the pipeline is built and pumping oil through the remote wilderness of northern British Columbia, a lawyer for the province noted at a hearing deciding the pipeline's fate.

Chris Jones grilled a panel of company experts on the design of the 1,100-kilometre pipeline that would deliver oil from the Alberta oilsands to a tanker port on the BC coast.

"So is what you're telling me that the actual sensitivity of a pipeline, perhaps this pipeline, along with other ones, can only be determined when it's actually been constructed and you're able to test that actual pipeline in operation?" Jones asked on the second day of environmental assessment hearings in Prince George.

"We have a quite an operating history.... It's not an issue of trust us, wait 'til construction," answered Barry Callele, director of pipeline control systems and leak detection for Enbridge Pipelines Inc.

Testing is and has been under way, Callele said, and test results show the estimates provided in the project proposal are conservative.

"But I guess the answer to my question is still: We don't know until it's been built. Isn't that right?" Jones asked.

"I think we know what we know today. We'll know more at every phase along the pipeline construction project and we'll know emphatically or empirically at the time that fluid withdrawal tests are done at different sections of the pipeline."

Callele said there would be five overlapping leak detection systems on the twin pipelines that would carry diluted bitumen to the tanker port in Kitimat, and condensate from Kitimat back to Bruderheim, Alta., including aerial surveillance, foot patrols, and 132 monitored pressure valves along the route.

"We will have one of the best instrumented pipeline systems not only in North America, but probably the world," Callele told the panel.

Jones pointed out that according to US data, there were 31 leaks from Enbridge pipelines in that country since 2002, and six of the 10 largest spills by volume in that time were from Enbridge pipelines.

Of those six, none were detected by Enbridge leak detection systems, Jones said.

BC Environment Minister Terry Lake issued a statement late Wednesday saying the government is "extremely concerned" about the answers heard at the hearings.

"The responses from Enbridge/Northern Gateway to cross-examination by our legal counsel are too often incomplete and lacking in commitment," Lake said. "Their answers suggest that the company is not taking the very real concerns of British Columbians seriously."

The government took issue in particular with the company's reliance on manual shut-down, instead of automatic action in the case of a leak being detected.

"One thing that is crystal clear after the last two days is that Enbridge/Northern Gateway is putting off making commitments about including these systems in the pipeline design until after they get approval to proceed," Lake said.

"We believe that the only way to protect British Columbia's interests is to ensure that these commitments are made up front, so that everyone will understand how they intend to run this project."

- With files from Tamsyn Burgmann in Vancouver