An oil spill near the Lions Gate Bridge would pollute the shoreline all along the Burrard Inlet within a matter of hours, a new report commissioned by the cities of Vancouver and Burnaby, and the Tsleil-Waltuth Nation has found.

The computer modelling by Genwest Systems Inc., from Edmonds, Wa, looked at the potential trajectory of an oil spill occurring in the inlet. The package of information was gathered together to fight Kinder Morgan's Trans Mountain pipeline expansion and the rise in tanker traffic the proposed pipeline would bring to the area.

"What we learned from that modelling,was that [within] hours— not days—hours, 50 to 90 per cent of the oil that spilled would reach the shorelines of cities, municipalities, First Nations —all across the Burrard Inlet," Vancouver's deputy mayor, Andrea Reimer told CBC News.

Genwest was asked to measure what would happen if 16 million litres of oil — just 20 per cent of a tanker's load — spilled into the water near the Lions Gate Bridge.

In their findings, they suggest that while Trans Mountain's own spill modelling does a "reasonable job" in charting the trajectory across most of the Salish Sea, "we identified at least two serious shortcomings which have significant implications for oil spill trajectory modeling in Burrard Inlet."

The most serious shortcoming Genwest says it identified was with Trans Mountain's beaching algorithm, which works on the principle that once oil reaches land, it does not re-float into the waters.

"This is strongly contradicted by experience with thousands of real spills," the report notes. "Heavily- oiled shoreline tends to be re-washed, particularly by tidal action in areas of rocky shorelines or man-made structures."

The second issue, the report claims, is the expectation by Trans Mountain that any spill at the proposed oil terminal in Burnaby, would be completely contained.

"For planning purposes a containment boom is a good idea and is bound to help," the report states. "But to assume it will be 100 per cent effective is not appropriate from an oil spill trajectory modeling perspective and is not the historical norm."

Reimer says this modelling is just one part of an evidence-based package that will be presented to the National Energy Board later this month.