In a significant victory for historical preservationists, Santa Clara County’s Historical Heritage Commission voted 5-1 Thursday night to recommend that the Mt. Umunhum radar tower be placed on the county’s inventory of historic resources.

The decision means that the Board of Supervisors will now have to consider a strong recommendation for saving the tower when it takes up the issue, expected later this year. Adding the tower to the historic inventory makes it harder to raze.

The commission’s vote came after a two-hour hearing in which the heavy majority of speakers beseeched the board to save the tower, a valley icon that anchored the Almaden Air Force Station during its operation between 1958 and 1980.

The decision is a setback for the radar tower’s owners, the Midpeninsula Regional Open Space District, which has put forward options that include tearing down all but one of the tower’s five stories and converting the footprint into a visitors’ center.

The commission’s vote is advisory only. The Board of Supervisors will have the final say on whether to protect the tower. But Board President Dave Cortese has spoken out strongly in favor of saving the structure, which is widely visible from the valley floor.

“The tower is still in danger. It needs protecting,” said Sam Drake, the president of the Mt. Umunhum Conservancy, a private group that is raising money to preserve the tower. Drake’s group has an agreement with Midpen to bring ten groups of visitors to the site.

At the heart of the debate Thursday night was the question of whether the concrete tower retains enough “historical integrity” to be preserved. A consultant hired by Midpen, Turnbull & Page, concluded that the tower lacked integrity because its radar “sail,” a large structure which turned atop the building, is no longer present.

But a consultant hired by the Umunhum Conservancy disagreed, as did a consultant hired to review the reports for the county. That third consultant, JRP Historical Consulting of Davis, concluded that the tower’s placement atop a mountain, in its original unadorned concrete form, gave it the historical integrity to be preserved.

— Mercury News