Old, underground vaults extending under sidewalks in Minot’s central business district may largely disappear when work begins on a major downtown infrastructure project later this year.

The Minot City Council’s Public Works and Safety Committee voted Wednesday to recommend that the council abandon and seal vaults that have outlived purposes as coal chutes, freight elevators, storage or other uses. The cost of filling the vaults would become part of the infrastructure project, but property owners would pay to remove any internal utilities, such as electrical utilities, plumbing or meters.

The vaults have been encroaching on the public right of way since long before the city began requiring permits for such things. After hearing from some property owners who wish to keep their vaults, the committee agreed to consider requests for encroachment permits where vaults are shown to not present dangers.

“Mine isn’t a vault. It’s part of the property,” said Leonard Niess of Niess Impressions. “I believe my building structure is quite sound. It would cost the city a considerable amount of money to come in and remove that underground area.”

He noted the sidewalk is a foot thick over the extended basement, which is used in his business and once housed coolers when the building was built as a creamery 100 years ago.

The vault at Niess Impressions has been framed with timber and appears to be structurally sound, said Dave O’Shea, project engineer with Houston Engineering.

O’Shea gave a presentation showing the condition of some of the vaults that his firm examined. There were cases of exposed rebar under sidewalks on the ceilings of the vaults. One vault had remains of an abandoned freight elevator and some had sanitary sewer lines or electrical circuits. Conditions varied from structurally sound to one in which a wall was leaning toward the street.

The vault in the old Woolworth’s building at 2 S. Main was among those in uncertain condition, having been closed off and unused for years. Chris Lindbo, who owns the building, said he would like to keep the vault for historical reasons if it can be made safe.

Steve Carrigan, general manager at EID Passports, said when his company remodeled the former YMCA, the fire suppression mechanisms were installed in the vault because that’s where there was room. It would be expensive to relocate the system, he said.

Meyer said the city could specify in encroachment permits that responsibility for the vaults falls on the property owners. Currently, if a sidewalk fell in and someone was injured, liability is on the city.

“We feel that there is a liability to the City of Minot with the conditions we have with some of these underground vaults,” Meyer said. “While we are doing construction downtown, we want to minimize the city’s liability and try to control the project schedule by dealing with these things upfront.”

A sidewalk had collapsed over part of a vault during construction of Artspace. That vault exists in one of about a dozen locations that engineers identified on a map last fall. O’Shea said engineers have since learned of several other vaults but still may not be aware of all.

Council member Dave Lehner mentioned other concerns hiding underground, such as steam tunnels that were part of the heating system in early Minot. O’Shea conceded that even once the project design is complete and work has started, he expects there may be underground surprises during construction.

The infrastructure project involves replacing underground utilities and upgrading streets, street lighting and sidewalks. The city received an $18 million federal grant for the project. The local share will be paid through special assessments on property owners.

Abandoning and filling sub-sidewalk vaults is roughly estimated to cost $361,000. With the relocation of utilities in the vaults, total cost is estimated at $500,000 or more.