The cost of a controversial natural gas pipeline planned to run through Virginia is expected to increase by more than $1 billion.

The Richmond Times-Dispatch reports Duke Energy is a 47 percent partner in the 600-mile (1,000-kilometer) Dominion Energy-led Atlantic Coast Pipeline. Duke CEO Lynn Good said in an earnings call Tuesday the estimated total project cost is now at least $6 billion because of delays in the permitting process.

Dominion spokesman Aaron Ruby could not confirm the new estimate but said Dominion’s financial disclosure next week would have more information.

Southern Environmental Law Center attorney Greg Buppert says the higher cost means Virginia and North Carolina utility customers will pay more.

Duke anticipates the project’s cost to increase by up to $1.5 billion before its expected 2019 completion date.