STATE TRANSPORTATION officials said the elevated section of the Massachusetts Turnpike between Boston University and the Charles River is deteriorating at an exponential rate.

Michael O’Dowd, the Department of Transportation’s director of the I-90 Allston project, said a hands-on, six-week inspection of the roadway in February determined it is in serious trouble. To illustrate the situation, he showed a picture of a cross-girder beam in 2013 and a picture of the same beam earlier this year. In the first picture, the beam is covered in rust; in the second picture, there are gaping holes in the beam itself.

“There are several instances of this,” O’Dowd told the I-90 Allston task force Thursday evening. “The rate of deterioration is exponential.”

State officials announced last week that they intend to hire a contractor by the end of 2022 to do $75 million of work on the roadway to make sure it lasts another 10 to 15 years. Over the last several years, the state has spent about $1 million a year maintaining the roadway. The stretch of Turnpike handled 140,000 vehicles a day prior to the pandemic, O’Dowd said.

O’Dowd said the initial work will be beneath the roadway itself, repairing steel and putting in additional supports to hold the structure up. Following that, the roadway surface will need to be repaired, which O’Dowd said will require lane closures for two years at nights and on weekends.

Gulliver said the work had to be done to make sure the roadway doesn’t give out before it can be replaced as part of the largest I-90 Allston project. The state is currently projecting that the I-90 Allston project would cost more than $1 billion and take as long as 10 years to complete.

Fred Salvucci, a former transportation secretary, said the new supports for the elevated portion of the Turnpike should be placed at locations that will not hinder the eventual construction of a new roadway at ground level.

He also suggested state officials may want to reduce the number of lanes on the Turnpike now to reduce weight and stress on the structure.