Crossing Paths
By Neal Singer

Two not-yet-built medical buildings have forced a $6 million relocation of utility lines on the rapidly developing north campus of the University of New Mexico in Albuquerque.

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Existing lines, which service the university's law school to the north, pass through the foundations of the proposed buildings.

Larry Schuster, a UNM utility engineer, said there's currently a parking lot where the buildings are slated to rise, but its asphalt overlays utility lines in place since the 1970s.

"Our goal is to establish utility corridors that won't be violated by construction in the future,." said Bob Notary, the university's project manager.

Phase one of this six-month sub-project - part of an award-winning $60 million utility renovation program reported by Southwest Contractor in April, 2003 - was substantially completed in December. Phase two, which involves further utility extension, should be completed in June. The work clears the way for the new medical research and heath science education buildings.

Under direction of Albuquerque general contractor RMCI Inc., 24-in. supply and return mains for chilled water were rerouted, as were steam, sanitary sewer, irrigation, domestic potable water, multimedia, and electrical lines.

"The job is difficult from a time standpoint," said RMCI project manager Doug Harned.

For one thing, the parking lot is sometimes congested because it serves functioning medical school buildings. For another, rarely used utility lines, in place for decades, are sometimes hard to locate.

Complicating matters further, the new sanitary sewer line was initially slated to be installed via an open trench, but "that would have been extremely disruptive to the job site," Harned said.

Instead, RMCI contracted with Minnesota-based Akkerman Inc. to lower a laser-guided boring machine into an 8-ft.- diameter, 20-ft.- deep manhole.

The machine's targeting system is >> incorporated in its pilot head for better accuracy.

"We had enough faith to put in the destination manhole," Harned said. "We set the borer for line and grade and hit the manhole within an inch at 300 ft."

The pilot casing that followed the borer acted as a guide for the vitrified pipe that followed. The process is called pilot tube microtunneling. The process saves time and money over cut and fill operations.

The change from open trench work to protected underground burrowing required RMCI to file a change order.

"It cost more but saved money in interruptions missed and street closings," said UNM's Notary, who agreed to the change. "It was well worth the extra cost."

To protect future contractors, the medium-voltage electrical lines (12,470 volts) were placed in 5-in.-diameter PVC conduits. These, along with 4-in.-diameter communications conduits, were ensconced in 20-conduit duct banks that were then filled with a cement slurry, said James Garcia, president and general manager of Albuquerque-based U.S. Electrical Corp.

"Future diggers will hit concrete before conduit," Notary said.

Garcia said it's difficult to dig up a long-standing facility because many utility lines are shown on maps, but some are not. "We're finding utilities no one knew were there," he added.

Lines with electrical current can be located with tools that in effect dowse for magnetic fields generated by the current. Unused 'dead' lines can be difficult to detect.

Forgotten or unnoted lines for water and irrigation also can be troublesome.

"Anytime we break a line, it holds us up," Garcia said. In general, line removal is accomplished by a potholing process that turns dirt to mud through use of a high-pressure wand. A hose then sucks up the mud to reveal the pipe.

Phase one of the project used 600 lin. ft. of ductile iron pipe thinly lined with cement for the chilled water line. Also used were 750 ft. of guided bore line, 400 ft. of 24-in.-diameter storm drain, 424 ft. of 12-in.- diameter water line, and 340 ft. of 8-in. steel steam pipe, all in a work area 50 ft. wide by 600 ft. long.

|The entire renovation project was funded by university bonds, said Mary Bosovutch, director of UNM's physical plant. Increased efficiencies in utility operations are expected to eventually return all costs.

Bids for constructing the two health sciences buildings, as well as a new school of architecture and additional athletic facilities, should go out after the first quarter of the year.