For the next month, motorists trying to cross Admiralty Inlet will have a long drive ahead of them.

The Mystic Sea is providing passenger-only ferry service for the next four weeks while the car ferry, Steilacoom II, goes into drydock for maintenance.

Service is scheduled to start Monday morning, Jan. 5, and continue until the end of the month.

Workers are busy this weekend preparing equipment that will go into Keystone Harbor to help passengers board and depart from the Mystic Sea.

A temporary barge was towed to Port Townsend Wednesday and workers installed a transfer span for walk-on passengers. After the final sailing of the Steilacoom II takes place from Keystone Sunday night, the barge will be towed across the inlet so it can be connected to the ferry dock in time for the first sailing Monday morning.

Joy Goldenberg, spokesperson for Washington State Ferries, said workers will have some minor items to complete when the first sailing from Keystone takes place at 7:10 a.m. Monday.

The barge is being installed to provide a better place for passengers to board and disembark the ferry. When passenger-only ferry service was last instituted after the Steel Electrics were pulled from service in December 2008, passengers boarded from a float dock near a boat launch in the nearby state park. That proved difficult for many passengers.

The Mystic Sea is a familiar vessel to Whidbey Island residents. Every spring the ship docks at the Coupeville Wharf to take sightseers into Saratoga Passage to view the grey whale migration. The Mystic Sea will make its way to the ferry route Sunday to conduct a final fit up with the barge and to sail across the inlet.

The 100-foot Mystic Sea, which is based in Anacortes, can carry up to 77 passengers. The Ferry System is paying Mystic Sea Charters $5,290 a day. That fee covers the boat, crew, fuel and other expenses.

Once the Mystic starts operating, there won’t be any cancellations due to tide and ebb currents, although the weather could still disrupt service.

Mystic Sea schedule

The Mystic Sea, a 100-foot, 77-passenger boat will begin offering passenger only ferry service from Keystone starting Monday, Jan. 5. The schedule for passenger ferry service is as follows:

Leave Keystone: 7:10 a.m., 9:10 a.m., 11:10 a.m., 1:10 p.m., 3:10 p.m., 4:35 p.m., 6:10 p.m., 7:45 p.m., 9:15 p.m.

Leave Port Townsend: 6:20 a.m., 8:15 a.m., 10:15 a.m., 12:15 p.m., 2:15 p.m., 3:50 p.m., 5:20 p.m., 7 p.m., 8:30 p.m.