Power lines were not what Intell Staley, LLC (Kansas City, Missouri, U.S.) pictured for Staley Farms, a golf community in suburban Kansas City. Unfortunately, a 69-kV overhead line owned by local utility Aquila stood directly in the middle of the proposed golf course, within the trajectory of a well-hit drive and, potentially, in the path of the development's success.

Rerouting the overhead lines wouldn't eliminate the eyesore, only relocate it, so Staley decided to invest in underground cable and contacted Burns & McDonnell, an engineering, architectural, construction and environmental service firm in Kansas City.

Burns & McDonnell designed an underground line that could be routed alongside an existing roadway to provide future access for utility maintenance vehicles. However, what looked like ordinary vacant ground turned out to be a minefield of permitting and construction difficulties. The right-of-way ran through the Multnomah Plantation Site, listed on the National Register of Historic Places. Early excavation revealed the presence of cultural resources: trails, a limestone dam and three pre-Civil War gravesites.

Additionally, there were two stream crossings along the route. And, the landscape design called for a stand of mature trees near the proposed trenching area to remain intact. Burns & McDonnell/New River Electrical, LLC and Intell Staley, LLC put their combined resources to work to make the problems — and the overhead lines — disappear.

First, Burns & McDonnell permitting specialists helped negotiate a memorandum of agreement between Staley Farms, the Missouri Department of Historical Preservation, and the Corps of Engineers detailing procedures to be followed concerning natural and cultural resources at the site. The agreement helped defuse a potential public relations crisis, and with permits in hand, the project team moved on to installation challenges.

The underground circuit is approximately 5700-ft (1737-m) long, with a single splice. The splice was installed in a 20- by 8- by 6-ft (6- by 2.4- by 1.8-m) precast concrete manhole. Planned open-trench installation of the entire cable could have damaged cultural resources and the line of trees edging the green.

For this segment, Burns & McDonnell designed a 340- by 3-ft (104- by 1-m) steel casing to be jack-and-bored through solid limestone for the conduit. Once the conduit system is installed in the steel casing, it is grout filled to dissipate the heat from the cable. The open-trench conduit system design used four 6-inch (15-cm) diameter PVC conduits and one 2-inch (5-cm) diameter PVC conduit encased in concrete. To accommodate future electrical demands, Aquila required the line to be designed for 161-kV upgrade.

The team took advantage of cross-linked polyethylene-insulated shielded power cable (XLPE) for the installation. The cable was awarded to Forte Power Systems and the design included a 1500 kcmil copper conductor, XLPE insulation, welded and corrugated copper sheath, external polyethylene jacket and weighed 9.4 lb (4.3 kg) per foot.

Computerized cable-pulling techniques also helped installers avoid damaging the cable as it was pulled. A device called a dynamometer continually monitored stress on the line to ensure that the cable's pulling strength was not exceeded. The maximum pulling tension for the cable was 12,000 lb (5443 kg) and the highest recorded tension of the installed cable was 3900 lb (1769 kg).

The new line was energized in October 2002. Staley Farms has the all power it needs, now and for the future, and the lines that deliver it are out of sight.

In February 2003, the project won an Engineering Excellence Award from the Consulting Engineers Council of Missouri.
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