A five-mile interim expansion will reduce congestion and improve mobility on State Route 24, a freeway that links southeastern Maricopa and northern Pinal counties to the Phoenix metropolitan area.

For this project, the Arizona Dept. of Transportation opted to use available funds to design the final roadway, then scale that design back to keep construction within budget. Running from Ellsworth Road to Ironwood Drive, the expansion was initially designed with three general purpose lanes, one auxiliary lane and one HOV lane in each direction. The purposeful scale-back brought the design down to two lanes in both directions.

Additionally, the team opted to reserve the right-of-way while optimizing interim elements in their final configurations in order to help minimize future throwaway. The design team also used what will be future entrance and exit ramps as travel lanes through the intersections.

Photo Courtesy Stanley Consultants

At 95% design completion, the Western Area Power Administration reversed its initial determination that the roadway had sufficient vertical clearance for a high voltage transmission line. Rather than spend $1.6 million for utility relocation, the designer opted to lower the roadway profile for sufficient clearance, which reduced the project cost.

Although this move resulted in drainage issues, crews built a 2,500-ft storm drain connected to the adjacent drainage channel, allowing the low point to gravity drain. This process also generated 80,000 yd of dirt that could be repurposed across the job, saving another $400,000.

To reduce right-of-way costs on the Mountain Road, the team decided to flip the crossroad/mainline profile so that SR-24 travels over Mountain Road. This helped the project avoid landlocked properties, reduced right-of-way acquisitions by $10 million and decreased bridge size and earthwork, saving another $500,000.

More than 200,000 cu yd of concrete was necessary for this project, but concrete suppliers were not able to produce and deliver the requested amounts, even on smaller batch days. To solve this problem, the contractor partnered with an aggregate supplier and placed two batch plants on site. The wet plant produced 115,000 cu yd for the five miles of portland cement concrete pavement (PCCP) needed across the project, while the dry plant produced 85,000 cu yd of Class S concrete to supply channels, bridges, box culverts, curbs and sidewalks.

Photo Courtesy Arizona Dept. of Transportation

In total, the contractor moved 1.5 million cu yd of dirt, erected 70,000 sq ft of retaining walls, placed 35,000 cu yd of concrete for storm drain channels, paved six miles of 13-in.-thick PCCP, built four new bridges, 12 miles of storm drains and six box culverts.

Despite having to work through two devastating monsoon seasons—among other challenges—the project team was able to open a one-mile stretch of the freeway four months early and the remaining four miles on schedule and within budget in August 2022. When funds become available, additional lanes and overpasses can be seamlessly added to this interim roadway with minimal throwaway and inconvenience to drivers.