PORTLAND — Casco Bay Lines is proposing to double its terminal size as part of an ambitious slate of renovation projects likely to cost as much as $3 million.

The ferry service, which connects the city of Portland with the Casco Bay islands, is requesting proposals for approximately $800,000 in repairs and renovations to the Maine State Pier used by the ferry service.

Casco Bay Lines will soon seek bids on a companion project as well, a roughly $2.2 million expansion of its terminal, which General Manager Hank Berg said was built about 25 years ago to accommodate 500,000 yearly passengers.

The ferries now serve nearly a million passengers annually, Berg said.

“In the summer, it gets pretty crowded,” he said. “The line stretches outside; there’s not enough room for everybody to wait inside.”

The proposed renovations involve expanding the size of the terminal from 3,000 square feet to 6,000 square feet, and moving the public waiting area closer to the harbor, where new glasswork will allow passengers to look at the harbor and boat traffic while they wait for their ferries.

Prior to 1988, Casco Bay Lines operated out of even smaller accommodations on the nearby Custom House Wharf.

“At that time, the [the ferry service] was serving a smaller population; the waterfront was largely a working waterfront and the island populations were comprised of fishermen and mostly local residents,” a description of the upcoming projects says.

“As use of the terminal has increased, more and more people and freight are being serviced by the larger ferryboats,” the description continues. “Passengers sitting in the waiting room of the Ferry Terminal cannot see their gate or boat’s arrival, so they choose to wait outside, often in inclement weather.”

The renovation project also aims to address what the organization sees as a shortage of restrooms at the facility.

Funding for the projects includes a mix of federal grants, previously approved state bonds and Casco Bay Lines matching funds, Berg said. The pier renovations are likely to begin in February or March, while the terminal work is scheduled to start in late spring or early summer.

Berg said the organization hopes the newly renovated terminal will be complete by the fall.

“We’ve just outgrown the building,” he said. “It’s about 25 years old and needs some work.”

A third related project in the future, which has not yet been funded, would consist largely of site work, such as the widening of public walkways around the terminal to make them more pedestrian-friendly.