The U.S. Department of Transportation is providing more than $2.5 million to help renovate the Casco Bay Lines ferry terminal in Portland.

The money will help pay for the second phase of a renovation program at the terminal, which provides ferry service to islands off the Maine coast. U.S. Sens. Susan Collins, a Republican, and Angus King, an independent, both applauded the funding.

The Casco Bay ferries service about 1 million people per year. Collins and King called the service a “critical link” between the islands and the mainland. They say the renovation project will curb congestion and improve efficiency.

The second phase of renovations is also designed to improve safety at the terminal.

Collins chairs the transportation, housing and urban development appropriations subcommittee.