Sources told KPIX 5 that that Google is building a floating marketing center for Google Glass off Treasure Island. (CBS)

SAN FRANCISCO (KPIX 5) — The U.S. Navy had its share of secrets on Treasure Island, but few were better kept than what’s taking place on a mysterious barge just off the island.

The barge, with a four-story stack of shipping containers, is out in the open for all to see. But the project’s purpose has been kept under wraps, and virtually no one wants to talk about it for the record, from the harbor office at Clipper Cove to the Treasure Island Development Authority to the U.S. Coast Guard.

“I don’t know anything about it, honestly I don’t,” a voice on the intercom at the Clipper Cove told KPIX 5. “It’s a complete mystery to me.”

There has, of course, been speculation about the barge’s purpose, much of it centering on the belief that it’s a water-based data center for Google.

KPIX 5 has learned that Google is actually building a floating marketing center, a kind of giant Apple store, if you will — but for Google Glass, the cutting-edge wearable computer the company has under development.

Although Google wouldn’t respond to requests for comment for this story, sources close to the project told KPIX 5 that Google hopes to tow the completed structure from Treasure Island across the Bay to San Francisco’s Fort Mason, where it would be anchored and open to the public.

But as mysteriously as the barge-and-container structure began appearing several months ago, work on the project suddenly stopped a few weeks ago.

The reason: Google does not have a permit for a floating anything.

“Google has spent millions on this,” said an insider close to the San Francisco Bay Conservation and Development Commission. “But they can’t park this barge on the waterfront without a permit, and they don’t have one.”

A BCDC official confirmed the agency has held discussions with Google about “hypothetical operations” on the water, but he complained the tech giant has been vague about how the barge would be used.

Larry Goldzband, BCDC executive director, said Google is free to build whatever it wants but the company needs to define the structure’s purpose if it wants a permit.

And that’s not the only hurdle Google faces in its quest for a permit. Docking the barge for an extended period of time at Fort Mason would qualify as “bay fill,” said a source with long experience in waterfront issues.

“The law is crystal clear in this case: The Bay is not to be used for something that can be built on land,” Goldzband said.

Further complicating the picture for Google, the BCDC is already facing heat over the plan to build a new waterfront arena for the Golden State Warriors. Although the arena would be built on existing Piers 30 and 32, the piers would have to be enlarged to accommodate the structure.

“Given that controversy, it’s not at all certain that BCDC approves the Google structure,” the waterfront expert said. “They may end up with egg on their face and a lot of money lost in the drink.”

GOOGLE BARGE