The demolition of the old Contra Costa County administration building in downtown Martinez will make possible construction of a 20,000-square-foot office building on that same spot — a structure county officials say could also be three stories tall.

The possibility of the new office building was discussed during a wide-ranging Board of Supervisors retreat last week. Any formal decisions about a new county office building will be made in the future.

The old county administration building at 651 Pine St. in downtown Martinez, which opened in 1964, was officially decommissioned after the formal dedication in December of the new administration building on Escobar Street, across the street from the old building. A significant amount of satellite communication equipment is still on and in the building, said Eric Angstadt, chief assistant county administrator, and the building has not been completely vacated.

He didn’t announce a date for when demolition of the 12-story building, one of the tallest in Contra Costa County, could begin.

A new office building at that 651 Pine St. site, Angstadt said, could host space for the Sheriff’s Office, the District Attorney’s Office, the Public Defender’s Office, Contra Costa Health Services and the still-forming Office of Racial Justice and Social Equity.

At 12 stories tall, the decommissioned McBrien Administration Building dominates the Martinez skyline. It may soon be demolished and replaced with a shorter structure. (Google image)

There also is also “strong interest,” Angstadt said, to move the Contra Costa County Superior Court’s law library from the A.F. Bray courts building two blocks away into the prospective new office building.

A new two-story office building would cost an estimated $65 million, Angstadt said, with about $40 million of that cost to be “new debt.” A three-story building, he said, would cost about $75 million. The cost of demolishing the old building is included in both figures, he said.

Angstadt recommended the two-story option to the supervisors, saying he is confident there are enough prospective tenants now to fill that space the first day it is open. He is not certain three floors would be spoken for at the outset, but four supervisors said they prefer a three-story building. It would cost more, they reasoned, to add a third floor later than to build it along with the rest of the building.

“It probably wouldn’t be filled immediately, but I would think that within five years it would be,” Supervisor Karen Mitchoff said.

When asked why more office space wasn’t built into the newly christened county administration building on Escobar Street, Angstadt said that the new building was designed to conform to City of Martinez guidelines favoring shorter structures, and that the soils where the new building is are subject to liquefaction and can’t support a larger structure.

Even though 651 Pine is only a block away from the new building, Angstadt said that parcel is more able to support a larger building than is the Escobar Street parcel.