Kitsap Transit announced plans for a two-boat service test on the Bremerton-Seattle fast ferry route starting Monday, Sept. 23.

The test will be four weeks long, according to Kitsap Transit officials. Afterward, scientists will measure beach conditions along Rich Passage to determine whether the service can operate the full summer schedule with a two-boat commute service without harming the beaches.

The test service must be completed before Oct. 26, due to seasonal changes making it difficult to discern the impact of wake wash from the fast ferries, a Kitsap Transit press release states. The vessels conducting the two-boat service will be Rich Passage 1 and Reliance. Lady Swift, a third vessel that was delivered recently, needs additional work because it did not achieve all of the contractually required specifications.

If either vessel needs to be taken out of service during the four-week testing, the current sailing schedule will take priority and the sailings added Sept. 23 will be canceled until both vessels are back in service, the release states.

During service testing, four existing sailing times will slightly shift. The 8 a.m. departure from Bremerton will shift to 8:05 a.m.; 8:35 departure from Seattle to 8:40 a.m.; 7:10 p.m. departure from Bremerton to 7:05 p.m.; and 7:45 p.m. departure from Seattle to 7:40 p.m.

To fully simulate two-boat service during the four-week period, Saturday sailings on the Bremerton-Seattle route will be extended through Oct. 19, according to Kitsap Transit officials. The Saturday sailing schedule will not change. The additional sailings will be filled on a walk-up basis only.

“If Kitsap Transit does not test the tolerance of Rich Passage’s beaches this fall, the next earliest opportunity would be next summer,” the press release states. “Kitsap Transit has decided to run the test service this fall in order to learn sooner whether a two-boat commute service is environmentally feasible.”

Starting Monday, Oct. 21, the fast-ferry schedules on the Bremerton-Seattle route will switch to its normal winter schedule with sailings on Monday through Fridays only. The Kingston-Seattle service will switch to its winter sailing schedule Monday, Sept. 30.