The pipeline carries crude bitumen from the Alberta oilsands to Vancouver.
When completed, the proposed expansion will increase pipeline capacity from 300,000 barrels per day to 890,000 barrels per day, the company says.
The plan also includes the expansion of the Westridge Marine Terminal in Vancouver to allow larger tanker ships to transport the oil to Asia.
Residents say they are concerned about the increase in oil tanker traffic, the increased size of the tank farm on Burnaby Mountain, the effects on health and safety in Burnaby and elsewhere, and the impacts on watersheds.
Their "people's procession" is following the existing and proposed oil and gas pipeline route and ends with a rally at Westridge Park at 1 p.m. PT .
A flotilla of boats, canoes and kayaks is also leaving the North Shore to join the protesters at the Westridge Marine Terminal, the pipeline's endpoint, for a second rally around 3 p.m. PT.
MAP: Proposed route of march and rally