* Like scores of bases across the country, Treasure Island Naval Base has become obsolete in the post-cold war era and will close by 1997. As the armed services retreat from here and other bases, Hollywood crews are marching in, turning mothballed hangars into vast sound stages for multimillion-dollar productions.
The two cavernous hangars at Treasure Island once housed a 1939 international exposition and sheltered Pan Am's huge Clipper airplanes.
These days, construction crews inside Hangar 2 are constructing an entire 8,000-square-foot apartment and a police station for the San Francisco murder mystery ``Copycat'' (starring Sigourney Weaver and Holly Hunter).
Over in nearby Building 180, nails are being pounded for the oversized sets of the Disney film ``James and the Giant Peach'' (a stop-motion animation film akin to ``The Nightmare Before Christmas'').
At Sand Point Naval Base in Seattle, producers for the upcoming Fox network show ``Medicine Ball'' have constructed a complete hospital set (including emergency room and operating theater) inside a building once shared by Marine reserves and the Coast Guard. Two years ago, ``Sleepless in Seattle'' re-created the Empire State Building's top two floors inside another Sand Point hangar.
The futuristic thriller ``Species,'' starring Ben Kingsley, called for a high-tech facility in the middle of the desert. So the production crew will spend a few days filming at the Tooele Army Depot outside Salt Lake City.
The Defense Department in years past granted filmmakers very limited access to its facilities. Only the most rah-rah scripts (``Top Gun'') were approved, and the government would pull the plug on any effort (television's ``Supercarrier,'' for instance) that dared not to be obsequious. Movies and TV shows that were not about the military were shown the door.
As more and more bases either close or are downsized, the Department of Defense in the last few weeks has changed its policy. Military-related stories must still pass muster with department brass (whether they are filmed on active or closing bases), but nonmilitary films now are welcomed to closing or downsized bases.