Michael Goodman /ENR Wide brims provide shade.

The $200-million expansion of Interstate 10 from six to eight lanes in Tucson reflects growing commuter traffic with Phoenix, 120 miles to the north. The 3.5-year A+B contract, held by a joint venture of Kiewit Western Corp., Phoenix, and Sundt Construction Inc., Tempe, Ariz., represents the largest single Arizona Dept. of Transportation highway expansion contract ever let, says Roderick Lane, ADOT senior resident engineer.

Work began in 2007, when the contractor shut down the 4.5-mile stretch that handles 140,000 vehicles daily. Tucson residents preferred a three-year closure rather than the original plan to perform three separate 3-year projects, says Lane. The contractor installed a new traffic center with 72 cameras to monitor the traffic shunted to frontage roads, which were expanded from two to three lanes.

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The widened highway requires 68,000 cu ft of portland cement atop 42,000 tons of base asphalt, says Lane. Sixteen bridges, decorated with colorful panels created by a local artist, will allow for 17-ft clearances, up from 14 ft.

To avoid the worst of summer temperatures, most paving is done at night. Bridge decks are placed starting around 2 a.m., says Craig Martin, Kiewit project engineer. An on-site concrete batch plant provides chilled water for the mix.

During the day, crews wear wide-brimmed hard hats and gloves as they place some 3,000 linear ft of corrugated 24-in.-dia drains along the edge of the highway. The drains will catch rainflow and deliver it to catch basins. Ironically, “summer is the rainy season,” notes Martin. Frequently, heavy rain sweeps through in the late afternoons or early evenings. “We have to plan our summer work around the monsoons,” Martin says.

Traffic is now moving over to one newly paved and expanded half of the highway as the team reaches the halfway mark, says Lane. The team has until early 2010 to finish the job, but could win up to $920,000 for finishing early under the A+B contract, says Lane.