Boston city officials reveal cause of mysterious sinkhole in Dorchester

The large sinkhole discovered this weekend in Ronan Park in Dorchester. –Erin Clark / The Boston Globe

Workers secure a fence around the sinkhole. —Erin Clark / The Boston Globe

By Erin Clark/The Boston Globe Staff
December 10, 2020

BOSTON, MA – The mysterious sinkhole discovered in Dorchester’s Ronan Park over the weekend isn’t another malevolent force of nature spawned by the year 2020.

Rather, it’s a product of the 19th century.

During a press conference Thursday morning, city officials revealed that the more than 16-foot-deep hole was caused by an abandoned well from the days when Dorchester was mostly rural and had yet to be connected to the Boston water system. Potentially, it might even date back to when the Boston neighborhood was its own town.

“We kind of accept the history of Boston as being everywhere, but also not part of our daily lives,” Joe Bagley, the city archaeologist, told reporters. “When something like this turns up, it’s kind of shining a light on a story that may have been either lost or underrepresented in the history of this neighborhood.”

Bagley said they used property records to deduct that the well was constructed by members of the Pierce family, who owned the land before it was purchased by the city in 1912 and turned into a park.

Originally native land of the Massachusetts tribe, the particular property where the well was located was purchased in 1818 by John F. Pierce, a cabinet and piano maker. Pierce built two houses on the property, including a mansion and a home located by the well. However, the estate was broken up on Sept. 22, 1871, and Mary L. Pierce, a widow and apparent relative (Bagley said they’re still trying to determine her relation), acquired the land.

According to Bagley, a deed from the time stated that Mary Pierce needed temporary access to a well until she dug her own. Officials aren’t exactly sure whether the well that caused the sinkhole is the one John Pierce built in 1818 or the one Mary Pierce dug between Sept. 22, 1871, and May 1, 1872.

“The well would have likely been abandoned sometime in the 1870s to 1890s when this area received running water from Boston water and sewer,” Bagley said. “At that point, Mary passed away and the property transferred to another person by the name of Hannah Bliss, who then sold the property to the City of Boston to turn it into Ronan Park.”

Officially, the city is referring to the hole as the “Mary L. Pierce Well.”

Buried about 10 feet deep, the stone-lined well measures about two-and-a-half feet wide and six-and-a-half feet deep — though it may have gone deeper, according to Bagley.

Bagley suspects that the well’s covering caved in “at some point in the not too distant past,” leading to the loosened soil from the weekend storm slipping down into the hole and partially filling it.

“So we don’t know how deep the well was originally,” he said.

Ryan Woods, the commissioner of the Boston Parks and Recreation Department, said the city received a 311 call Sunday reporting the newly opened hole.

Officials fenced off the hole so no people or animals would fall inside, before turning it over to Bagley’s department.

Bagley said Thursday that his team lowered an iPhone taped to flashlights on a rope into the hole to record video of the inside of the well.

“We call it Bob Ballard on a budget,” Bagley said, noting that they have used the iPhone technique in the past.

The only things they found at the bottom of the hole were some leaves and a plastic bottle.

“Fortunately, nobody’s down there,” Bagley said.

Woods says they’re planning to fill the hole and reseed the grass by the end of the month, though its online presence will live on — both on the city website and social media.

According to Bagley, the “hundreds if not thousands” of old wells around Boston were typically filled up and capped before they were decommissioned in order to prevent sinkholes — but not always. During the Big Dig, “numerous” wells were found, Bagley said. He also said that his department plans to compare the Ronan Park well to another 34-foot-deep well that was found in 2016 near the Massachusetts State House on Beacon Hill.

“Boston’s a very old city, so it’s got a lot of mysteries still underground, which makes my job really interesting and fun,” Bagley said.

However, he added that, for safety reasons, “it’s nice to have things be a little bit more predictable than this.”