The Story County Board of Supervisors on Tuesday reviewed a predesign agreement with the Iowa Department for Transportation (IDOT) that proposes construction to U.S. Highway 30 that will see a new interchange at 580th Avenue.


The board took no action on the matter, but if approved, the agreement commits the county to the construction layout, as well as maintenance responsibilities for the affected frontage roads.


“The DOT would like us to take action on this as soon as possible,” said Darren Moon, county engineer, “I want to make sure by approving this we aren’t tying ourselves into anything extra in the future.”


Earmarked for 2023, the proposed changes include the construction of a new interchange on U.S. 30 at 580th Avenue, a closure of connection and entrances from Interstate 35 to west of 590th Avenue, and reconstruction of county side roads.


A 24-foot wide paved roadway would be rebuilt on 580th Avenue, to realign it south of the highway, and the old roadbed north of U.S. 30 will be torn up and used as a frontage road with multiple entrance points.


Additionally, 241st street will be built and extended roughly 4,000 feet south of the highway and the 58-the street ramp.


The DOT will be responsible for maintenance of the bridges and highway roadways and ramps, and the county would assume maintenance responsibility of the new frontage roads. Moon said the maintenance might include an additional truck route for maintenance efforts.


The effort is part of a $225 million project by the DOT to adjoin U.S. Highway 218 and Highway 30 to form a new interchange, that starts in Tama County and ends at a proposed Mt. Vernon and Lisbon bypass in Linn County.


DOT officials said that traffic will be maintained during construction.


Moon said a preconstruction agreement will appear on a future agenda, and the cost of the improvements, payment scheduled and project responsibilities will be defined in the agreement.


“Nowhere (in the predesign agreement) does it get into the cost part of this, that’s the next agreement,” Moon said.”I just want to make sure by approving this, we’re not tying ourselves into any future costs.”


Additionally, the board also reviewed its five-year road construction project plan, which budgets roughly $7 million for secondary road improvements in 2021.


Moon said a lingering questions that remains is bonding for the projects, and that a $3 million bond would cover five of the seven projects.


What would remain unbonded, according to Moon, is a proposed paving projects on 13th Street in Nevada and 530th Avenue.