The long-overdue replacement and expansion of a hangar at Katama Airfield in Edgartown has been rejected by the state Division of Conservation Services, leaving town officials searching for another avenue to complete the project.

At the annual town meeting on April 13, Edgartown voters approved an article to revise a conservation restriction held by the Nature Conservancy in order to renovate and expand the existing hangar from a 50-by-53 foot structure to a 60-by-100-foot structure. The plan calls for adding some 60 acres of land to the area protected under the conservation restriction and converting another 7,200 square feet of airfield space to wild, protected land.

But the favorable vote by the town was only a first step; amending a conservation restriction requires state approval, and last month the state said no to the plan.

“We conclude that the expansion of the airport facilities is specifically prohibited and therefore not permissible,” wrote Robert O’Conner, director of the Division of Conservation Services, in a letter to the town dated May 24.

The five-sentence response from the state comes in response to a four-and-a-half-page letter that the town conservation commission sent in February of this year, detailing the history of the World War II-era hangar, and the rationale behind the project which aims to restore the historic hangar and also continue the goals of a far-reaching conservation program. Situated in the middle of a globally rare sandplain grassland, the airfield and its surrounding area are home to a number of rare plants and animals. In 1985, using a state self-help grant, the town bought the airfield as part of a larger purchase that included some 120 acres of the Katama Plains. The purchase, which began in 1984 and was expanded in 1985, was the largest conservation purchase of its kind at the time on the Vineyard and the first conservation partnership between the state, town and private land trusts, including the Nature Conservancy.

Meanwhile, the airfield remains in active use, and the 1945 hangar, which dates to World War II when the airfield was used as a flying school for the military, is badly in need of repairs. In the spring of 2008 Edgartown voters approved the renovation of the hangar. In April of this year they approved the conservation restriction amendment, pending state approval. Money for the project has been earmarked from the town Community Preservation Act fund.

The project “is of a small-scale in keeping with the goal of maintaining a pre-1960s grass strip airfield,” town conservation agent Jane Varkonda wrote in the February letter to the state. “We sincerely believe that the expansion of the hangar . . . will result in no adverse impacts on rare species habitat. Instead, more habitat will be permanently protected, the airfield operation will be more viable for the future . . .” Among other things the plan calls for adding the 56-acre Nickerson parcel to the conservation restriction. Taken by eminent domain in the mid-1980s, the Nickerson land was the subject of litigation at the time the original conservation restriction was written.

The letter also takes note of prior precedent, when in 1989 the state allowed one airfield runway to be expanded while another was abandoned. The town operates the airfield at an annual deficit. “Transient air traffic has been declining for years and is expected to drop ten per cent annually,” Mrs. Varkonda wrote. Nevertheless, she wrote that the hangar “was outmoded at the time of its construction and is woefully inadequate today. Not only is the hangar undersized, but it is now decrepit and beyond repair.”

At a meeting of the Edgartown selectmen on Monday afternoon this week, the board vowed to press ahead with the project, and said the town would have to develop a new plan for getting state approval. “If it doesn’t work out, we’re just going to go for an act of legislature,” said town administrator Pamela Dolby. “We’ll have to just keep working at it until we find a way to do it,” agreed selectmen Arthur Smadbeck.

Mrs. Varkonda said this week that the ruling from the state caught everyone by surprise.

“We’re not quite clear why they don’t believe that the change in use is permissible,” she said. She said she hopes to obtain more information from state agents during a conference call the conservation commission has scheduled with the Division of Conservation Services for the first week in July.

At the local level, the next step will be to take the hangar renovation plan to the Martha’s Vineyard Commission, at a public hearing scheduled for July 15.

Without state approval, the town cannot move forward with its plans to expand and renovate the hangar. But Mrs. Varkonda said if they are able to obtain the necessary authorization, the town still hopes to have the project completed by the spring of 2011.