Sailing on the San Tan

By K. Robert Wendel

An army of workers and machines is sweeping across southeast Maricopa County, turning fields and desert into a concrete ribbon stretching for miles.

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The new, six-lane San Tan Freeway is the final segment of a highway system started nearly 20 years ago after voters in the county approved a half-cent sales tax for road construction. Since work started in 1986, more than 160 mi. of new freeway have been constructed in Maricopa County.

Crews from the Phoenix offices of FNF Construction, Pulice Construction and Edward Kraemer and Sons are constructing interchanges and overpasses along a 26-mi. stretch running from the Interstate 10/San Tan Interchange >> in Chandler to Elliot Road in Gilbert, near Williams Gateway Airport.

Those firms, along with the Phoenix office of D.H. Blattner Construction, recently completed sections of 6.5 mi. of roadway running from the I-10/State Route 202 interchange east to S.R. 101, where Edward Kraemer and Sons constructed a $48 million interchange for the 202 and 101.

The Arizona Department of Transportation is conducting a feasibility study to extend the San Tan Freeway behind South Mountain and through Ahwatukee, possibly linking up with I-10 somewhere near 51st Avenue. Studies are underway.

On the east side of the project, FNF Construction recently completed the Super Red Tan Interchange that links the San Tan and Red Mountain freeways with U.S. Highway 60 in Mesa near Power Road. Pulice Construction recently completed the $39.4 million, 1.9 mi. section from the Super Red Tan interchange from Baseline to Elliot roads.

When Pulice Construction and FNF Construction complete the final San Tan legs in December 2006, the Arizona Department of Transportation will have let more than $350 million in construction contracts on the 26-mi. stretch.

In the process, more than 1.2 million cu. yds of concrete were used and 17 million cu. yds of earth was moved.

The entire 26-mi. section from the I-10 interchange on the west to the Super Red Tan interchange on the east is being constructed with 13-in. Portland cement concrete paving.

The paving sits on a base course ranging from 4 in. to 8 in. and is capped with rubberized asphalt, which cuts road and vehicle noise significantly. The road sections alternate between above grade on an embankment, at grade and below grade. In areas where there were houses, designers put the roadbed 20 ft. to 30 ft. below grade.

"The main reason we went with a depressed road in a lot of sections was for noise abatement and aesthetics," said Brian Bombardier, an engineer with the Phoenix office of Michael Baker Engineering. "The sections on grade are all in farm areas, so we saw no reason to go below grade. As soon as you depress a road, you add all sorts of costs like drainage and pump stations that are expensive."

Part of the project included the construction of retention basins.

"There were two huge basins we needed for the freeway, and the town of Gilbert had the forethought to turn them into parks," said A.D.O.T. transportation manager Jim Romero. "We are really seeing the benefits in this part of the Valley, in terms of the connectivity with the rest of the system.

Crews also constructed miles of retaining and sound walls, along with stormwater systems.

The San Tan Freeway has spurred millions of square feet of new development, along with jobs and residential communities. Already, plans are calling for a new Westcor Mall and auto mall near Williams Field Road.

Hospitals are also being constructed along the alignment.

The bridge structures along the entire 26- mi. section were all constructed using soffit fills. Crews created a pile of dirt, then poured a waste slab, then constructed the concrete tub girder bridges on top of the waste slab. When the bridge was completed, crews excavated the dirt from underneath the bridge, allowing the waste slab to fall away.

"We used soffit fill bridges because they are safer and faster, which translates into cheaper," said Pulice Construction project manager Mark Soyster. "You don't have to contend with the false work, so that saves a lot of time."

In Gilbert, the San Tan's alignment meant the realignment of railroad tracks and roads, including Pecos, Ray and Greenfield roads. The town's road sections also feature extensive theming, with artists creating images from Gilbert's agricultural and railway history.

Many bridges are themed with wheat and railroad designs that are cast-in-place on overpasses, wing walls and abutments.

Pulice Construction built an overpass realigning Ray and Greenfield roads to accommodate a new interchange. Crews rerouted a railway and constructed new steel rail bridges and two new overpasses.

"It's preferable to use steel for the railroad bridges," said A.D.O.T. engineer Sam Hanna. "The bridges can be very narrow, so you don't need the big cross sections you would get from a concrete bridge."

Because of the tight right-of-way, contractors didn't have the room to lay the below-grade freeway's slopes far enough back, so contractors turned to a method that is increasingly becoming an option for heavy highway contractors.

"We had to use soil nails because those slopes were cut pretty steep," said John Gleason, a project manager with INCA Engineers Inc. of Phoenix. "I think soil- nail walls have become part of the contractor's arsenal of means and methods. They aren't typically used out West, but they are becoming more common because of the cost savings, and there is certainly a constructability benefit."

Crews working farther west had difficulties with utilities. The area along Price Road is home to large semiconductor plants and had a few extra twists.

"We had to relocate a large nitrogen line that companies like Intel use, and we had to be extremely careful," said project manager John Walker of Edward Kraemer and Sons. "Anytime you hear about potential damages of $7 million a day if the gas line is put out of action, it perks your ears up."