Major construction to overhaul the intersection of Preston Road and Plano Parkway is projected to commence this fall and last for over a year, city Director of Engineering Caleb Thornhill said. Plano City Council on Monday approved an agreement with the Texas Department of Transportation, revising a longstanding plan to rework the intersection. City officials expect the project to cost $5.6 million, 90 percent of which will come from federal and state sources, according to the agreement. Plano Parkway's eastbound and westbound lanes are currently split by a large grass median. Crews will construct new eastbound lanes adjacent to the existing westbound lanes. Though the construction will relocate the eastbound lanes the westbound portions of Plano Parkway, and much of the construction will take place on this median, traffic will likely be impeded. The construction is expected to slow traffic in the area, but much of the construction will take place between the two portions of the road, Thornhill said. The project will also add dual left-turn lanes and a right turn lane in both east and west-bound lanes of Plano Parkway. The overhaul of the intersection will also include the reconstruction of Alliance Boulevard to the south. City officials want to consolidate the double intersection into one because they believe it will reduce backlogs at the traffic lights, Thornhill said. The city had an agreement in 2004 with the state transportation department for a similar project at the intersection totaling $2.8 million. The new agreement expanded the original budget and updated “terms that are no longer valid from the original agreement,” according to a memo from city staff. Now that the agreement is updated, the next step for the city is reviewing bids and awarding a contract before construction crews begin their work later this year.