Marysville couple discovers hidden tunnel under riverside house

MARYSVILLE — Trevor and Hayley Gilmartin always suspected there was something under their home’s indoor hot tub.

Every time they filled it with water, the spa slowly emptied.

In March, the couple decided to renovate the room. They removed the hot tub and found a larger hole than expected, big enough for a person to fit through, and it clearly wasn’t done by accident.

“We finally checked it out and went over there, and there’s a room full of water over there,” Trevor said.

Since making this shocking discovery, Trevor and Hayley have been investigating what the space was for and who created it.

The couple purchased the home on River Road in 2020. Its location along the St. Clair River was perfect for the couple, both qualified divers.

“I started when I was 16, because my family was visiting Hawaii for vacation,” Hailey said. Trevor returned to his hobby and earned his diving certificate. “Ironically, I think he now enjoys diving more than I do.”

The couple tested the water in the tunnel to make sure it was safe and lowered a camera with a light to take a look at the room. Trevor then went down to explore it, estimating that it was 30 feet long and 20 feet wide. He estimated the water was about 15 to 20 feet deep.

The couple’s discovery went viral after they posted a video of Trevor exploring the tunnel to TikTok in April. Hayley said she woke up the next day to find hundreds of thousands of views. The video continued to spread and gain popularity, and now has 26 million views.

A wooden barricade stands at the back of the room. Trevor said his next step would be to remove the barricade to explore the tunnel further.

It’s slow work though, as the water is cold and hard to see, and the wooden wall has proven surprisingly strong. He tried to pump the water, but after eight hours the water level remained unchanged.

Outside the Gilmartin home, the couple regularly dives into the St. Clair River, collecting bottles that once contained all manner of alcoholic beverages.

They keep a collection on display in the house; we say A. Van Hoboken & co. and appears to date back to the 1850s. Another’s label indicates it was brewed in Port Huron.

Trevor and Hayley have heard suggestions that the tunnel may have been used by Prohibition-era bootleggers to smuggle alcohol into Michigan.

“It’s the most exciting answer we can think of (what the tunnel was used for),” Hayley said.

After the United States passed the 18th Amendment banning the sale of alcohol nationwide in 1919, the St. Clair River became one of the most popular crossings for illegally transporting alcohol into the country from Canada until the amendment was repealed in 1933.

Some of the bottles Hayley and Trevor found while diving were near what they believe to be the exit to their underground tunnel. The grates prevent them from exploring the interior, but Trevor said the tunnel must be connected to the river, as the water cannot be pumped out.

“If you start directly from where the wooden wall of the tunnel is, they line up almost perfectly,” Trevor said. “I think the fact that it’s just big enough for one person says a lot.”

The Gilmartins have not been able to confirm this particular possibility: there are no bottles or other signs of contraband inside the tunnel itself. And Trevor admitted that there is another possible explanation for the tunnel’s existence that he thinks is more likely, albeit more mundane.

While trying to find records of the history of their property, the Gilmartins found an article written by Bob Ankrapp in 1979 for the now defunct St. Clair County Independent Press stating that before their property was a house, it was a pumping station.

The 45-year-old article says the pumping station was built in the 1940s by the Dow magnesium plant. Ankrapp interviewed a man named Phillip Tuttle, who decided to rebuild it into a house.

Ankrapp wrote that the building was constructed of concrete, as was the tunnel, to give it additional protection in times of war.

“As magnesium was an essential part of the wartime production effort, numerous shields were built into the structure to protect it from bomb explosions,” the article states.

The Gilmartins wonder if there might be plans of the pump station that could reveal whether the tunnel was built as part of the tunnel station, but were unable to find any records in the County Clerk’s office. St. Clair.

The couple, however, do not rule out the possibility that it was used by smugglers. Their neighbors told them the property had another building before the pump station, but they couldn’t find anyone who remembered it.

Ankrapp now works for the city of Dearborn Heights as a public information officer. When asked what he knew about the use of the property before it became a pumping station, Ankrapp said he vaguely remembered someone telling him the property had been used during Prohibition, although he pointed out that it had been too long ago for him to be certain.

“I’m working on 45-year-old memorabilia, so it’s not certain, but I remember someone saying it was used during Prohibition,” Ankrapp said.

When they’re not delving into the tunnel’s past, Trevor and Hayley are still deciding what to do about its future. They want to find a way to stop the water from seeping out. Once that was done, they considered turning the tunnel into a basement.

Trevor said he’s considered everything from a shooting range — “We’d need to add a lot of ventilation for that, though,” he said — to a few bowling alleys for private use.

“If we can pump the water out and seal it, it could have many uses,” Trevor said.

The Gilmartins said anyone who may know the history of the tunnel or the property can reach them at [email protected].

Contact Johnathan Hogan at [email protected].