BALTIMORE (Map, News) - Beneath the rolling hills of the Rosewood Center campus in Owings Mills, there’s oil.

So jokes Robert Day, the director of the state-run facility that houses 156 developmentally disabled residents that is slated for closure by 2010. It’s his response to neighbors and some reluctant family members of Rosewood residents who allege the state wants to shutter the center to capitalize on its development potential.

Some lawmakers agree the 210-acre campus — the largest tract of undeveloped land in Baltimore County — could be a lucrative sell for the cash-strapped state. But several have introduced legislation requiring the state to transfer the property, dotted by about 36 buildings, 10 of which are abandoned, to the state’s park system.

“This area is suffering from a huge deficit of open space,” said Del. Dana Stein, a Baltimore County Democrat who is sponsoring the legislation. “The main point is to make sure it’s not sold for development.”

At a House hearing on the proposal last week, representatives from Gov. Martin O’Malley’s administration opposed the bill, calling it premature. The proposal circumvents a long-established process for surplus state-owned land, said Shaun Fenlon, the state’s director of land acquisition and planning.

“We want to continue to respect that process,” Fenlon said.

About 75 acres of the campus are already under contract for sale. The property could be sold for about $4 million, according to state analysts.

A proposal in the state Senate calls for a committee to study the issue. Advocates for the developmentally disabled support that measure, emphasizing the proceeds from the land sale would benefit a fund for community-based services for that community.

The wait list for such services has grown to 17,000 residents, they said.

“No new funding would mean the wait list would continue to grow,” said Ken Capone, who has cerebral palsy and works for an advocacy group. “This is unacceptable.”