In the latest step toward the rebirth of San Francisco’s Presidio from an aging former Army base to a bright light of America’s national park system, crews are set to break ground Thursday on a project to build a new 14-acre public park on top of two freeway tunnels near the Golden Gate Bridge. When finished in 2021, the unusual project, called Tunnel Tops, will link Crissy Field, on San Francisco’s waterfront, to the Presidio’s Main Post, parade grounds and visitor’s center. That connection was severed more than 80 years ago when the road to and from the Golden Gate...