Feeding Growth

By K. Robert Wendel

A half-mile concrete tunnel, significant electrical upgrades and new cooling towers are the major facets of a $16 million infrastructure upgrade at the University of Arizona in Tucson.

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Because the university is rapidly expanding its medical research campus with the addition of three major buildings, and with more on the drawing board, it was necessary to extend major utilities into the area. Sundt Construction's Heavy Civil Division, which is based in Phoenix, is the construction manager at-risk on the contract.

The new U of A buildings includes Drachman Hall (an academic building), the MRB Building (medical research), and the IBSB Building (research laboratories.)

Craig Raymond, Sundt's project engineer, said a significant portion of the project involves relocating existing utility lines in the area and installing 2,300 lin. ft. >> of precast concrete tunnel, which will house the "wet" utilities - principally water from the campus central refrigeration building that will be used for heating and cooling.

"The tunnel will house high- pressure steam, condensate transfer, pumps and condensate return and compressed air lines," Raymond said.

The tunnel is trucked to the site in 20-foot.-long sections, each of which is 5 ft. deep, 6 ft. wide and weighs 20,000 lbs.

After the tunnel is secured in place, the electrical subcontractor installs the "dry" utilities - electricity and communications cables - in ducts laid in a trench beside the tunnel.

Raymond said one of the bigger challenges Sundt faced was having to keep the streets open during installation of the tunnel. Sundt pushed 84-in.-diameter steel casing pipe under five intersections at about 25 ft. deep.

"Each of the pushes was about 60 ft. long," he said. "Under good soil conditions, which we had, we averaged between 5 and 6 ft. a day."

"The other difficulty facing us was that there were so many utilities in the ground around these streets that it would have been difficult to do an open cut on them," Raymond said. "Most of those lines have been in place since the 1930s and 40s."

Away from the intersections, the tunnel system could be lowered into open cuts that averaged 8 to 10 ft. to the bottom of the tunnel. Vaults (17 of them) were installed approximately every 200 ft. to provide access for future pipe upgrades.

Henry Johnstone, mechanical engineer for GLHN A/E Inc. of Tucson, the project architects and engineers, said the electrical and communication cables were run in duct banks - concrete- encased banks housing individual conduits.

"They generally followed the same route as the tunnel," he said. "We also had to construct a new set of 15 kv high- voltage switch gears for the ducts."

On the mechanical side of the contract, Sundt constructed a new 4,000- ton cooling tower consisting of two 2,000- ton cells located in the Health Sciences Center central plant.

The final phase of the infrastructure work involves an extensive landscape and hardscape package to cover up the areas disturbed by construction and tie together the new buildings that are under way or planned.

Sundt has been able to maintain its schedule and has kept the project under budget, Johnstone said.

"There's a lot of chance for disruption and other problems on a job like this, but this one has gone seamlessly," he added.