After nearly 10 years as a work in progress, the final phase of construction on the Lagoon Pond drawbridge in Tisbury is slated to begin this fall. Final permitting was issued in August, and preconstruction meetings by contractor Middlesex Corporation began on Sept. 12, said Melinda Loberg, chair of the Lagoon Pond Bridge committee.

“It’s been a long journey, I would say,” said Tisbury Department of Public Works director Fred LaPiana. “It’s nice to see it come to fruition.”

The project is financed by the state Department of Transportation. The Massachusetts Department of Public Works began surveying the bridge area in 1989 because the structure, then 54 years old, had outlived its lifespan. The bridge was first built in 1935. Most bridges have a lifespan of about 50 years. A plan for a temporary drawbridge was unveiled in 2003 and work began in the fall of 2007.

The final phase of the project involves constructing a permanent drawbridge across Lagoon Pond and taking down the temporary bridge that was completed in 2010. A park area, landscaped with native plants, will be built on the Tisbury side of the bridge by the Lagoon, and the bike path extended to the Tisbury town landing. A small fishing platform facing the Lagoon will be built onto the bridge itself. On both sides of the channel, there will be an area for pedestrians to walk beneath and around the bridge. Sidewalks on the bridge will be compliant with the American Disabilities Act.

The bridge will also be built at a height sufficient to account for sea level rise, Mrs. Loberg said.

The new bridge will be built “immediately adjacent” to the temporary structure, MassDOT public affairs representative Michael Verseckes wrote in an email. It will be on the envelope of the original 1935 structure, which is currently blocked via chainlink fencing from the Oak Bluffs side of the lagoon.

The temporary bridge uses a system of pulleys to raise and lower the sections, but the new structure is a bascule-style bridge, employing a pivoting weight to pull the bridge open and closed.

Mr. Verseckes said the temporary bridge will continue to be used until the new bridge is fully complete.

According to the contract, all work, including removal of the temporary structure, must be completed by summer of 2016.

As part of the final phase, the home adjacent to the bridge on the lagoon side of the channel, which has been owned by the Holloman family since 1962, was taken by the state via easement over the summer.

The first noticeable phase of the construction project will be the teardown and removal of the house, Mrs. Loberg said. Construction in the off-season is limited due to spawning of winter flounder in the lagoon, which occurs from March to April.

Construction costs for the final phase will be $44.94 million, Mr. Verseckes said. Initial estimates were about $20 million. By the time the temporary bridge was completed, they had risen to $34 million.

The temporary bridge that now spans the channel cost $9.2 million to build, after an initial estimate of $3.5 million for that phase of the project. The bridge was issued a temporary permit by the Coast Guard for seven years, and was a source of controversy initially, as some felt the temporary phase should be skipped and the new bridge constructed immediately.

Because the old bridge was in such poor condition, however, the state “couldn’t guarantee that it would last long enough to design, permit and build the new bridge,” Mrs. Loberg said. An independent engineer, commissioned and paid for by the towns of Oak Bluffs and Tisbury in 2005, “was equivocal enough” on the state of the old bridge that the temporary bridge plan moved forward.

Mr. LaPiana said that to his knowledge, the bridge project was “certainly the largest and the most complex” state undertaking on the Island.

Martha’s Vineyard Commission executive director Mark London said one success of the project was the creation of the Lagoon Pond Bridge committee itself. “Basically, it allowed the Island to speak with one voice when dealing with MassDOT,” he said. Typically, when the DOT worked, they would talk to municipal officials and hold public meetings, but meet “largely on their own,” he said. The steering committee, which met twice per month in its early days, “looked at the options and made a lot of suggestions that very much improved the design of the project,” he said. The creation of the park and the extension of the bike paths were some of those suggestions.

“We really wanted it to be more like a park and less like a roadway,” Mrs. Loberg said.

“I have to say, of the final product, the Island got a great deal from the state,” Mrs. Loberg said.

Tisbury selectman and bridge committee member Tristan Israel said he was “glad they were finally getting down to it,” but expressed concern about potential challenges due to having two large construction projects going on at the same time in town next year. A proposed expansion and renovation of the Stop & Shop building is currently under review at the commission.

The possibility of simultaneous projects is “pretty staggering,” he said.