Delays and design changes have driven the cost to build the Trans Mountain pipeline expansion up by about 70 per cent to $12.6 billion from the $7.4 billion estimate made three years ago, the company says. The project has cost about $2.5 billion to date, including the impact of delays and additional regulatory processes, leaving an additional $8.4 billion needed to complete construction, plus $1.7 billion of financial carrying costs, said president and CEO Ian Anderson on a conference call on Friday. He said the project owned by the federal government is now expected to be in service by December 2022.