I Accidentally Explored a Radioactive Island in The San Francisco Bay

An Urban Explorer's Irradiated Playground

By: Ty Merkel + Save to a List

This story begins like most adventures I go on—with the Google search “creepy abandoned places in San Francisco”.

The sensible reader might ask…Um Why? My honest answer is that I’m a fool who will most likely find herself in a real life slasher film murder situation just because I like to take artsy photos of tatty chairs in abandoned buildings. 

But back to my Google findings. Treasure Island popped up at the top of my search. 

Wikipedia describes it as an artificial island which was constructed in 1936–1937 for the Golden Gate International Exhibition, via dumping 287,000 short tons of stone into the water off the shore of a tiny natural island named Yerba Buena. Which was a place I vaguely remember passing by on that proverbial family road trip, at the time my 7-year-old mind believing it to be San Francisco’s premier pirate retirement community, with buried treasures hidden every few feet.

According to shoddy YouTube videos the island was supposed to be an urban explorer’s wonderland: an aggregate of abandoned military barracks, school houses, and overgrown parks with rusty metal slides. So I was sold, jittery with excitement and wondering why I hadn’t discovered this treasure trove earlier.

The next morning my boyfriend and I jumped into my soccer mom van and crossed over the Bay Bridge. We took the exit for Treasure Island. 

First order of business was to drive around and scope out our adventure options. Soon we stumbled upon what looked like a storage container boneyard, all neatly stacked in a gravel lot, with a multitude of weeds grasping at the corners of the metal containers. We scampered up a few and snapped some photos. We still hadn’t seen another person. 

From there we wandered around the perimeter of Cosson Hall, a weird pair of buildings that served as military barracks until they were decommissioned in the 1990’s. The twin buildings were shaped exactly like asterisks, and dutifully covered in graffiti. We pulled on a few doors but got spooked when we spotted security in a jet black pickup truck. They were carrying some electrical gear into an adjacent tightly boarded up building.

We migrated and parked our car in the marina, near an overlook of San Francisco’s skyline. Before we realized what we were doing, we found ourselves following a wispy dirt trail that ran parallel to the road. It weaved under freeway overpasses, through cement tunnels, and across rickety wood planks laid over chasms where the cliff had fallen into the ocean. The hazardous trail deposited us right below the Bay Bridge, with the cars roaring overhead. Needless to say, we were trespassing hardcore.

We climbed through scrubby bushes and up sheer rock to reach the highway up top, then ascended even further, following along a rusty chain-link enclosure. Eventually, we found a hole in the fence and thoughtlessly popped through. 

Then came the surreal bit. On top of the hill there was a small suburban settlement. Wide streets lined on both sides with homes and apartments, the majority of them with large windows looking out over downtown San Francisco and the Bay Bridge—million-dollar views, needless to say, but they were all abandoned.

And as if this ghost-neighborhood wasn’t already twilight zone-y enough, each house was in pristine condition, lacking the telltale symptoms of abandonment—piles of broken glass, artless graffiti, and discarded furniture. Only a few townhouses had caution tape draped over doorways and “DO NOT TRESPASS” signs tacked to the front doors. We peered in windows to see plain white walls and polished oak floors.

All that is well and creepy, but for anyone who knows about rent prices in San Francisco, this is the true horror of this story: 

These stunning apartments, which are no more decrepit than your average a 3,000-dollar studio apartment in The Haight, are being left empty. At the time, it simply didn’t make any sense—especially to someone like me. I was living in an old apartment in the crowded city. The view out my window was just another apartment’s wall, and I was sharing a set of seven Ikea spoons and one good spaghetti pot with 13 roommates (no joke). Why was all this good space being unused? Think of how many spaghetti pots these people could have stored!

After searching the whole hilltop, this was the closest an apartment came to ruination…

Which seemed like the result of a stray fallen tree.

From there we walked down the middle of the street and back to our car, unbothered and unseen. 

When we returned home, I turned back to the internet for answers, equipped with my meager eye witness discoveries. 

What I found was that back in the 1950’s the military had improperly disposed of some radioactive material here, like they were going to play a death themed Easter egg hunt. 

Looks like there really is buried treasure on this ironically-named island.

But as we know, the military loves keeping secrets at the expense of civilian health, so this fun community project was kept under wraps. The most irradiated sites were gradually, quietly abandoned, and there were attempts to sell the property off to unwitting buyers and developers.

For years the government has been conducting radiation cleanups, periodically re-declaring the island safe. But the cleanup is long from over, and whoever hid all of Treasure Island’s treasures must have been extremely drunk while they did so, because people keep on finding more underneath playgrounds, front yards, and sidewalks…you know, all those normal places you traverse every day and probably don’t want to find Radium 223 at. 

Government officials still insist Treasure Island is clean enough for current residents, but many scientists, including Dr. Don Wadsworth (a navy subcontractor whose posh name alone oozes authority) assert just the opposite.

Wadsworth said he and colleagues found chunks of radium emitting so much radiation that if you accidentally stood by one for an hour, your porous body would absorb five times the radiation a nuclear worker absorbs in a whole year.

Then there was this California Public Health worker who found a sizable radioactive lump in a public park on the island. According to an internal memo she released later (it’s probably the most justly passive-aggressive memo in history, by the way), holding the clod she found for one hour could cause radiation burns and hair loss.

Worst Monday ever right?

On the North end of the island plenty of people are trying to live in normalcy in Navy housing that was turned into city-subsidized rentals. Except they literally can’t grow anything in their soil and their radioactive homes might be giving them cancer. To that, the government has officially said, bummer!!

Yes, most of these stories broke a few years ago. But the problem is that good ol’ gentrification is pushing more people out of the San Francisco, and possibly onto this island-sized heap of pre-cancer and cheap housing. So this story is anything but over. Stay tuned—I'm going back to discover more about Treasure Island.

Until next time, here’s a shot of my face so you can find me if I mysteriously go missing or the government replaces me with a robot. 

We want to acknowledge and thank the past, present, and future generations of all Native Nations and Indigenous Peoples whose ancestral lands we travel, explore, and play on. Always practice Leave No Trace ethics on your adventures and follow local regulations. Please explore responsibly!

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