Marysville couple finds hidden tunnel under riverside house

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

Anytime they filled it with water, the hot tub would slowly drain.

In March, the couple decided to renovate the room. They removed the hot tub and found a bigger hole than expected, one big enough for a person to go through, and that was clearly not made by accident.

"We ended up checking it out and going down there, and there's a room full of water down there," Trevor said.

Since they made the shocking discovery, Trevor and Hayley have been investigating what the space was for and who made it.

The couple bought the house on River Road in 2020. It's location along the St. Clair River was perfect for the couple, who are both trained divers.

"I started when I was 16, because my family would visit Hawaii for vacation," Hailey said. Trevor picked up the hobby from her and earned his diving certification. "Ironically, I think he now likes to dive more than I do."

The couple tested the water in the tunnel to make sure it was safe, and lowered a camera down with a light to get a look at the room. Trevor then went down to explore it, estimating it to be 30 feet long and 20 feet wide. He estimated the water to be about 15-20 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 it had hundreds of thousands of views. The video has continued to spread and grow in popularity, and now sits with 26 million views.

A wooden barricade stands at the end of the room. Trevor said his next step is to remove the barricade to explore the tunnel further.

It's slow work though, as the water is cold and hard to see in, and the wooden wall has proven surprisingly sturdy. He tried pumping the water out, but after eight hours the water level was unchanged.

Outside the Gilmartin's house the couple regularly dives into the St. Clair River, collecting bottles that once held all kinds of alcoholic beverages.

They keep a collection on display in the house; one says A. Van Hoboken & co. and appears to date back to the 1850s. Another's label states it was brewed in Port Huron.

Trevor and Hayley have heard suggestions 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 (for 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 to illegally transport alcohol into the country from Canada until the amendment was repealed in 1933.

Some of the bottles Hayley and Trevor have found while diving were near what they believe to be the exit to their underground tunnel. Grating prevents them from exploring into it, but Trevor said the tunnel must connect to the river, since the water couldn't be pumped out.

"If you go straight from where the wooden wall in the tunnel is, they line up almost perfectly," Trevor said. "I think the fact that it's just big enough for a person says something."

The Gilmartins haven't been able to confirm that particular possibility: There are no bottles or other signs of bootleggers inside the tunnel itself. And Trevor admitted, there's another possible explanation for the tunnel's existence he thinks is more likely, if more mundane.

While trying to find documents on 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 states the pumping station was constructed in the 1940s by the Dow Magnesium Plant. Ankrapp interviewed a man named Phillip Tuttle, who decided to reconstruct it as a house.

Ankrapp wrote that the building was constructed with concrete, just like the tunnel, to give it extra protection during wartime.

"Since magnesium was a vital part of the wartime production effort, many safeguards were built into the structure to make it safe from bomb blasts," the article states.

The Gilmartins wonder if there might be blueprints for the pumping station that might reveal if the tunnel was constructed as part of the tunnel station, but were unable to find any records at the St. Clair County Clerk's Office.

The couple hasn't ruled out the possibility it was used by bootleggers, however. Their neighbors told them the property had some other building before the pumping station, but they haven't found anyone who remembers it.

Ankrapp now works for the city of Dearborn Heights as its public information officer. When asked what he knew about the property's use before it was a pumping station, Ankrapp said he vaguely recalls someone telling him the property was used during prohibition, though he emphasized that it's been too long for him to be certain.

"I'm working off of 45-year-old memories, so it isn't certain, but I do remember, somebody saying it was used during prohibition," Ankrapp said.

When not looking into the tunnel's past, Trevor and Hayley are still deciding what to do about its future. They want to find someway to prevent water from pouring in. Once that's done, they've considered possibly converting the tunnel into a basement.

Trevor said he has considered everything from a shooting range — "We'd need to add a lot of ventilation for that, though," he said — to a couple of bowling lanes for private use.

"If we can pump the water out and seal it off, there could be a lot of uses," Trevor said.

The Gilmartins said anyone who may know about the tunnel's or property's history can reach them at gilmartin9719@gmail.com.

Contact Johnathan Hogan at jhogan@gannett.com. 

This article originally appeared on Port Huron Times Herald: Marysville couple finds hidden tunnel under riverside house