Lines Above and Lines Below: Planning, constructing, and maintaining utility lines.

• Author: Davenport, Sam

The decision to bury a utility line depends on many factors, such as climate and population density. Alaska's utilities decide how to provide services to a community based on its needs and characteristics.

Alaska Village Electric Cooperative (AVEC) has more power plants than all of Alaska's other electric cooperatives combined. The nonprofit serves residents in fifty-eight locations across Alaska, from Kodiak Island to Yakutat and Minto, which is the only community in the cooperative's network accessible by road. AVEC runs more than 150 diesel generators for more than 400,000 hours a year to provide services to its customers.

AVEC President and CEO Meera Kohler says that today the cooperative's electric lines are almost entirely above ground. "When our systems were first built out-mostly in the 70s--underground was thought to be the wave of the future," says Kohler. 'So our distribution systems were built underground. It became clear within a few years that wasn't a practical option for rural subarctic Alaska with locations having a substantial amount of active permafrost."

She continues: "Ground movement and shearing effectively shredded wires and It would be days, weeks, and sometimes months before faults could be found and wires fixed."

Over time, almost all of AVEC's underground distribution lines were converted to overhead. "We do have to build some underground lines-especially around airports--but that is typically not in permafrost impacted areas," Kohler says.

The Cons of Underground

Matanuska Electric Association (MEA), which serves more than 51,000 members in the Mat-Su, Eagle River, and Chugiak areas, manages more than 4,5000 miles of power lines in Southcentral. MEA published Underground vs. Overhead Transmission Lines to explain the organization's decision making process when choosing to install a line overhead or underground.

According to the briefing, opting to bury a transmission line can create various difficulties and additional costs. "Unlike distribution power lines that deliver power to homes, high-voltage power lines are extremely expensive to build underground. Underground construction of transmission lines often costs five to ten times more than overhead construction," the briefing says.

Some of those costs are associated with how the utility chooses to bury a line. Underground transmission lines, which are almost five times larger than overhead lines, can be buried directly or in conduit. Construction is cheaper...