Santa Rosa signed off Tuesday on long-sought deal paving the way for Caltrans to transfer a strip of land to the city and county for what proponents hope will become a future urban greenway.

The unanimous vote by the City Council, which followed a similar nod by the Sonoma County Board of Supervisors last month, was cheered by dozens of supporters wearing green shirts reading “Imagine a greenway to Spring Lake and beyond.”

The members of the Southeast Greenway Campaign have worked for years to convince Caltrans officials to turn over 52 acres of former Highway 12 right-of-way to groups that can preserve the land for public open space, bike paths and other uses.

“There’s been long-standing interest in pursuing this once-in-a-lifetime opportunity for our community,” said Linda Proulx, co-chair of the campaign.

The agreement states that Caltrans will offer the city and Sonoma County Water Agency the right of first refusal to purchase the property. The city has agreed to take ownership of the largest portion, from Farmers Lane to Summerfield Avenue, while the county has said it will take the portion running east uphill to Spring Lake. Caltrans has already agreed it does not need the land it acquired decades ago for a now-defunct plan to extend Highway 12 over Spring Lake, bypassing the busy Farmers Lane area.

Convincing the state agency not to just declare the property surplus and sell it to the highest bidder was considered a crucial step. Vice Mayor Chris Coursey doubted it would ever happen.

“When I first heard this proposal, I thought, ‘Caltrans is never going to give up that land,’ ” Coursey said.

Much work remains to be done. The property still needs to be appraised, a price agreed upon, money raised, and a plan for the land approved.

Other entities that expect to be involved in the effort include Sonoma County Regional Parks, which sees the possibility of a new entrance to Spring Lake; the nonprofit LandPaths; and the nonprofit Sonoma Land Trust.

Wendy Eliot, conservation director for the land trust, called it “highly unusual” for Caltrans to give local groups the right of first refusal on a property.

“Not many communities get the chance to craft the fate of piece of property like this,” she said.

Councilman Tom Schwedhelm said he strongly supported the effort, and like other council members praised the hard work and dedication of the volunteers who have pushed it forward patiently for years. But he also cautioned them not to expect a speedy process going forward.

“There are some other big issues we are dealing with,” Schwedhelm said.

You can reach Staff Writer Kevin McCallum at 521-5207 or kevin.mccallum@pressdemocrat.com. On Twitter @srcitybeat.