SOUTH PORTLAND – Operators of southern Maine’s largest psychiatric hospital plan to relocate to a bigger facility.

The Spring Harbor Hospital announced Friday that it will move from the Running Hill Road to a parcel near the Westbrook-Portland border, where it plans to build an 85,000-square-foot hospital with 100 beds.

Spring Harbor, a short-term psychiatric hospital, is housed at the former Jackson Brook Institute and has been steadily outgrowing the 65,000-square-foot hospital since Spring Harbor’s inception in 1999.

The current hospital also has 100 beds. But the new facility will have more space for such things as recreation areas and family meeting rooms.

The wooded site next to a conservation easement has views of rolling hills and more open areas for outdoor activities.

The space crunch at the current facility extends to Spring Harbor staff as well as patient services. The staff has grown from 354 to 425 over the past two years, said Dennis P. King, chief executive officer.

“Our employees have played more games of musical offices over the last two years than I care to admit,” he said.

The two-story building initially would house inpatient services but it could eventually accommodate outpatient services, King said.

The site is close to the Maine Turnpike, easily accessible to staff and is close to the majority of patients, 70 percent of whom come from Cumberland and York counties, said Meg Baxter, the Spring Harbor board’s chairwoman.

Spring Harbor, a part of MaineHealth, which includes Maine Medical Center and other health care groups, will apply to the state for necessary approvals for building the new facility.

Approval, designwork and construction are expected to be completed by spring 2004, officials said.