There is a mystery — and two large holes — under a Water Street sidewalk that will cost the Town of Warren $38,000 to fill.

Technically, the holes are two large old fuel tanks recently discovered under the sidewalk in front of Jack’s Bar and MM Furniture Restoration, as contractors worked to install lighting fixtures along the street as part of the town’s Water Street Streetscape program. The tanks, which town officials believe may have served a gas station decades ago, were unknown before workers hit the top of them during their work recently. Now, town officials are rushing to get them taken care so the sidewalk and, later, the road resurfacing portion of the project won't be delayed.

“They’ve probably been there over 60 years,” said Bob Rulli, the town’s project manager for the streetscape project. “There is lore that there was a gas station there but there are no records of that that we could find." One clue that they were from a service station is in an adjacent building, which has an old car bay and lift.

Since the tanks lie under the public sidewalk and take up its whole width, it is the town’s responsibility to get them cleaned up, filled or removed. Mr. Rulli said there are several options, including removing or filling them. Right now, he said, a likely scenario is filling them in with a concrete slurry mix after they’ve been investigated.

Exploratory digging at the tanks — one is about 1,200 gallons, the other 1,800 gallons — has begun, and Mr. Rulli said more digging, testing, cutting and probing underneath the tanks to check for soil contamination will be done before a final course of action is set.

“One of them had water but no evidence of a petroleum sheen or odor,” he said. “The other has fill in it. Because of their age there is a chance they may have rotted out (from the bottom).”

The $38,000 estimate to clean up and fill the tanks came from the town’s consulting engineering firm, Fuss & O’Neill, and that expense was approved by the Warren Town Council Tuesday night. Mr. Rulli said his next step is to contact the engineers and tell them the funds have been approved. The state DEM has already been alerted to the tanks and officials there have agreed to expedite their review of the cleanup/fill project.

“We need to move on this,” M. Rulli said. Town officials hope that ‘in the next two weeks we will have it completed.”