State, city tally expenses related to Interstate 93 sinkhole

Last modified: 9/12/2015 12:31:52 AM
The city and the state are ready to close the books on the repairs to last month’s sinkhole on Interstate 93.

The city will spend about $125,000 to reroute its underground drainage system, and the state will spend about $95,000 to repair the highway.

Big enough to swallow a car, the hole opened mid-day Aug. 19 in the northbound lane of the interstate between exits 13 and 14. No one was injured, and emergency repairs were completed overnight.

Officials determined the sinkhole had been caused by a 100-year-old city storm drain under the highway. When it caved in, so did the interstate.

While the state and city both own property affected by the sinkhole, neither has expressed an intention to hand the bill off to the other.

“The state has said to date, they worked on their end of the project, and we worked on our side of the project,” City Manager Tom Aspell said. “That’s where it’s been left. They understood we both have our responsibilities.”

Bill Boynton, public information officer for the state Department of Transportation, echoed that sentiment.

“As far as I know, that hasn’t really been discussed at any length,” he said.

The focus, Boynton said, is on paying the private contractors who did the emergency repairs. In coming weeks, the state will inspect the repairs and fill even more of the drain with concrete. A fresh coat of pavement will also smooth out the highway where the sinkhole once was.

For the city’s part, the failed storm drain served a large part of the drainage system for the downtown. When it was sealed, Concord officials worried that other storm drains would become overwhelmed and cause flooding at the nearby Storrs Street shopping plaza.

But Aspell said engineering and general services crews were able to reroute the drainage system to a under-used pipe earlier this month.

In the meantime, flooding did not occur.

“Fortunately, the weather has been good since the culvert failure, so pumping and flood risk have been minimal,” City Engineer Ed Roberge wrote in a report to the city council.

The city found money for that repair out of $400,000 earmarked for drainage improvements on Portsmouth Street. Aspell said Concord will apply for grant money to replace those dollars, in hopes of avoiding an effect on the tax rate.

(Megan Doyle can be reached at 369-3321, or on Twitter @megan_e_doyle.)

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