North Segment (Centre City Parkway to SR-78): Flatiron upgraded a 2.6-mile portion of Interstate 15 at Unit 1 to contain four new HOV lanes. The project includes the widening of nine bridges, five earth retaining walls, five masonry block sound walls, storm drain and water system improvements, 110,000 cubic meters of exported material and 22,600 cubic meters of concrete pavement.

Middle Segment (SR-56 to Centre City Parkway): At Unit 2, Flatiron constructed 20 retaining walls, five new bridges and five direct access ramps. Unit 3 consists of a 2.5-mile stretch of managed lane construction and a bridge reconstruction over Lake Hodges. This project included eight post-tensioned box girder bridges, 9,000 cubic meters of retaining wall concrete, 32,000 cubic meters of PCC pavement, and 251,000 cubic meters of roadway excavation.

Flatiron constructed 1.5 miles of I-15 lanes from Poway Road to Carmel Mountain Road to complete Unit 4. Flatiron installed moveable barriers along a 1.5-mile stretch of managed lanes and used 13 different types of retaining walls at Unit 5, which ran from Via Rancho Parkway to Center City Parkway.

South Segment (SR-163 to SR-56): Unit 1 is a 4.5-mile segment of lanes stretching from Miramar to Escondido, where Flatiron is widening I-15 to accommodate managed lanes. At Unit 3, Flatiron widened two miles of interstate from Mira Mesa Boulevard to Route 56 and reconstructed the bridges over Poway and Mercy Roads. Flatiron produced all of the aggregate and structure backfill needed for the Poway bridge reconstruction directly on site.

Flatiron was the prime contractor for all contracts except for Units 2 and 3 along the Middle Segment, for which Flatiron was the managing joint venture partner.