HAVERHILL — It was a simple cleanup, but when the job was done, a mystery remained.
Several mysterious stone structures behind the tennis courts at Winnekenni Park were recently made visible, after city workers removed overgrowth that was obscuring them.
But what they are remained a mystery — until one city official figured out their secret. The structures were built generations ago to protect the bases of old trees while Route 110 was under construction.
There are other similar structures along Water Street, but those are made of brick.
Dave LaBrode, a volunteer who among other things helps coordinate the city’s annual Earth Day cleanup, got a good view of the stone formations after city workers cleared brush and overgrowth from along an embankment inside the entrance to Winnekenni Park.
LaBrode had seen one of the formations in the past when he was taking part in cleanups in that area.
“You couldn’t really see them that well until they removed the overgrowth,” LaBrode said. “One is by the tennis court. Another is about 30 feet to the left and there’s a smaller one to the right, closer to the entrance’’ to the park, he said.
City Engineer John Pettis was able to identify the structures from a photograph LaBrode had taken.
Pettis said the structures are “tree wells’’ and that they were built to protect existing trees when Route 110 was built.
“It appears the roadway was built much higher than the preexisting ground level, which is why you see that embankment on the Winnekenni side of the roadway,” Pettis said.
“I’m also told by guys in the office that while the tree wells at Kenoza Avenue (Route 110) are built with field stone, there are many similar tree wells along Water Street, between Buttonwoods Avenue and the stadium, and that those tree wells are built with brick.”