he 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.

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 without installing conduit, but the line has a shorter operational life and is difficult to replace if damaged. Using conduit is more expensive, but gives the line a longer life and makes for easier replacement; however, even then utilities often install additional cable or redundant conduit, increasing construction costs but minimizing the need to go back and do additional construction.

“Insulated cables, underground surveying and excavation, splicing vaults, and concrete-encased conduits to protect lines from dig-ins contribute to higher costs,” the report says. And even with those additional precautions, “the lifespan of underground lines is thirty to thirty-five years, about half that of overhead lines.”

MEA’s briefing notes that generally underground options are too costly and result in increased rates. “Underground line maintenance is more expensive… Since the lines are underground, additional digging and disruption occurs, especially since the lifetime of an underground line is only about half that of an overhead line,” the report says.

“Underground lines also complicate access for neighboring property owners for the lifetime of the line. In addition, construction and maintenance require breaking ground and will likely impact other utility infrastructure like pipes or fiber lines.”

For other utilities, community regulations play a role in determining how lines are installed. In Anchorage some lines have been underground for decades, and the trend is for overhead cables to be moved underground.

Municipal Light & Power (ML&P) provides electric services for some of Anchorage’s oldest neighborhoods, and its 20-square-mile service area covers a variance of buildings, from commercial to industry loads to university and medical customers.

Each construction season, ML&P replaces overhead distribution lines with underground lines—a requirement based on the Municipality of Anchorage’s Title 21 ordinance. According to ML&P, the ordinance “requires utilities to annually spend 2 percent of their average city retail revenues to fund these projects.”

ML&P published the ML&P 5-Year Plan 2020-2024: For the Removal of Non-conforming Overhead Lines in Accordance with MOA Title 21.07.050, which provides some insight into the program, project selection, and proposed project timeline.

The utility has been putting in new distribution lines underground since the ‘60s and burying existing overhead lines since the early ‘80s, according to the plan. Some lines, like high-voltage transmission lines, can never be buried, and soil conditions may make line burial impossible, but the majority of ML&P’s lines are now underground.

“Above 68 percent of ML&P’s overhead distribution lines are already buried, more than in most cities. But the process will take decades,” its website says.

In the 2019/2020 season, ML&P completed the 3rd Avenue: Barrow Street to LaTouche Street project, which buried overhead power lines along 3rd Avenue from Barrow Street to LaTouche Street, converted the line to a higher kilovolt system, and was jointly constructed with the Municipality to allow for the installation of new lighting along 3rd Avenue.

Work is ongoing on the Mountain View Lions Park project, which will underground power lines along McCarrey Street and Mountain View Drive, as “overhead lines are currently located in the park and overhead structures disrupt audience seating arrangements of baseball games on the north field,” the report states.

According to published projections, four undergrounding projects are slated for completion in 2020.

In the Interior, Copper Valley Electric Association (CVEA) provides electricity to approximately 8,000 Alaskans. CVEA’s CEO Travis Million says the utility’s service territory is quite large—spanning 160 miles north and south and 100 miles east and west, about the size of West Virginia. CVEA has a number of power plants: the Cogeneration plant, the Glennallen diesel plant, the Valdez diesel plant, the Solomon Gulch hydroelectric facility, and the Allison Creek hydroelectric facility.

Million says that through energy created at Solomon Gulch and Allison Creek, CVEA was 74 percent hydroelectric for the entire year. “We serve the Copper Basin, which includes Glennallen and the surrounding communities, and then we’ve got a 106-mile-long transmission line that interconnects down to the community of Valdez, and we serve all of Valdez as well,” Million says.

Unlike other Alaska electric companies, CVEA is electrically isolated, meaning its grid isn’t connected to any others. “We generate all of our own electricity, we push it across our transmission lines, and then we distribute it to our members,” Million says.

Million says that Glennallen and Valdez have different approaches to distribution lines.

“I would say about 90 percent of our distribution lines—which is the lines that you see when you’re driving on the road that connect the businesses and houses—about 90 percent of our lines in the Copper Basin are overhead,” Million says.

In Valdez, Million says it’s almost the opposite: about 90 percent of lines in town are underground. “Density is one of the drivers,” Million says. “If you’re in a more city-type environment, typically, you’ll want to go underground.”

Million says one of the main reasons why the majority of lines in the Glennallen region are above-ground is due to permafrost. “Permafrost can wreak major, major havoc on underground lines,” Million says. “The ground is completely frozen six months out of the year, so it makes it real tough to dig up a line if you had to repair it or anything. So that’s why we typically try to keep our lines above ground in the Glennallen area.”

Permafrost in the Interior is challenging, but Million says the snow in Valdez can also challenge his team. “We’re dealing with anywhere from 10 feet to 30 feet of snow, depending on if you’re in the city or up in Thompson Pass,” Million says. “Even trying to find a piece of equipment under that much snow—it’s difficult.”

Of course electric companies aren’t the only ones working underground. Northern Utility Services is an underground utility contractor that provides water line repair and replacement, trenchless water and sewer installation, and low-impact excavation services, among others.

While Northern Utility Services operates in rural areas of the state, General Manager Darrin Bartz says it’s less than 5 percent of their projects, with the majority being on the road system. One of the obstacles of operating in more populated areas is working around other utilities.

“Natural gas, power, comm lines—they’re all over out there… the infrastructure, depending on the folks that are doing it, has changed,” Bartz says. “Sometimes it’s not always updated. A water line or a comm line that should be in this area sometimes shows up not in that area. Of course, that’s a challenge.”

Bartz says that there are plenty of challenges working in a landscape like Alaska. “Sometimes we’re dealing with some allocation across rural Alaska permafrost where lines can’t be buried, or we dig in rock, we dig in peat and soil, as we call it,” Bartz says. “The material that we dig in is probably the most challenging… like running sand—with every scoop you take out you’ve got two more scoops coming down the hole at you.”