How Low Should You Go?

By William Atkinson

It seems to be part of Americans' standard operating procedure: After a big, damaging storm it's almost inevitable that there will be a public outcry — or at least a media outcry — calling on the local utility and municipality to put all utility distribution lines underground. It's assumed that future outages will be avoided, because no lines will be damaged and lose power as a result. It's also assumed that underground lines are safer, because children or others won't have contact with live wires above ground.

However, total undergrounding is not always a 100 percent solution. That is, there are pros and cons to both approaches.

Overhead is certainly less expensive to install and maintain than underground, and, when outages occur, they can be located and repaired relatively quickly and inexpensively.

Still, there are a lot of downsides to overhead distribution lines. Most importantly, they are susceptible to outages from falling trees and limbs, especially during storms. And, every so often, errant drivers will plow into poles. Municipalities also occasionally have to deal with negative public opinion about overhead lines, in terms of outages, safety, and even aesthetics.

According to R. John Miner, president of Collaboration Unlimited, a utility consulting firm based in Austin, Texas, overhead lines also are subject to intermittent outages that result from shorts, such as those caused by tree branches or squirrels. "In these instances, the power may only be off for a few seconds, but it can be a problem for certain commercial and industrial customers with critical expensive equipment that automatically shuts down even if power is off for only a second or two," he says.

Meanwhile, underground distribution lines offer some notable benefits. While underground outages do occur, they are rare. In addition, underground lines provide better public safety, since there are no exposed downed lines or poles falling on homes or vehicles or within easy access of children or unsuspecting adults.

"Everything that is energized and has a shock hazard is not only underground, but also insulated and enclosed, preventing human touch," says Miner.

Finally, an underground system is hidden from view. One tangible benefit is that property values tend to be higher in neighborhoods with underground lines than in comparable (age, location, housing structure) neighborhoods with overhead lines.

Distribution line placement

Certainly, in recent years, most new lines are going underground. While it is more expensive to bury the lines than it is to run them overhead, it is less expensive to do so with new grid extensions than it is to dismantle existing overhead lines and bury them. One reason is that grid extensions occur in areas that do not yet have a lot of ground-level and underground infrastructure in place, such as roads and sidewalks, gas lines, and water and sewer lines, that make trenching time-consuming and expensive.

"It is pretty much universally accepted now that new residential areas in almost all parts of the country go underground," says Miner. "One reason this is so common is that utilities don't have to add these costs to their rates. Instead, the home owners pay the additional cost of underground in the cost of their lots, which ends up being part of their mortgages."

Another reason underground is on the rise is that costs are decreasing. "While the cost of underground is higher than overhead, a lot of utilities are taking a second look, because some of the pricing on dielectric cable is coming down," says Frank Alonso, manager for transmission line engineering at Leidos Engineering in Orlando, Florida. "It used to be that the cost ratio of underground to overhead was about six times greater. However, this is starting to be reduced," he says.

Despite the benefits of undergrounding, there is no wholesale rush to do it. Besides the expense, there have been some improvements to overhead reliability in recent years.

Following directives from the Federal Energy Regulatory Commission, the government agency responsible for energy management in the U.S., more and more utilities and municipalities are focusing efforts on "hardening" their overhead lines. Examples include reinforcing poles, becoming more aggressive with vegetation management, and using technology to more quickly identify and address outages. These initiatives are costly, but not as costly as undergrounding everything that is currently overhead.

So how do you decide whether lines should be overhead or underground? "First, utilities and municipalities need to be more aware of public opinion," says Alonso. "This has been increasing a lot because of the recent strong storms."

It's not the only factor, but municipalities should at least take the public's concerns into consideration, according to Alonso. Of course, this first requires that they educate people on the pros and cons of overhead and underground.

Second, while most lines could be buried, there are some specific instances where it's not the best idea. Some lines may traverse swampy, marshy, or otherwise wet lands, where undergrounding may be virtually impossible, or at least where the reliability of underground is likely to deteriorate rather quickly.

Third, while it may not be worth the time, effort, and cost to underground all overhead lines, municipalities should work with the local utilities to identify only those that frequently prove unreliable, and then determine whether it makes sense to bury those select lines, rather than undergrounding everything.

San Marcos: looks count

The city of San Marcos, Texas (pop. 54,000), has a lot to boast about. Archeological research suggests that the area is one of the oldest continuously inhabited sites in North America, with evidence of settlements going back 10,000 years. It's also one of the fastest growing cities in the U.S. And the city's beautification initiatives, which include projects to underground utility lines, are aimed at making sure San Marcos maintains its appeal.

"We adopted an undergrounding ordinance about two years ago," says Matthew Lewis, planning and development services director. "It requires that utilities go underground in the downtown area." While a lot of communities are undergrounding utility lines for reliability and safety reasons, San Marcos adopted its ordinance primarily for aesthetic reasons, according to Lewis.

The city adopted a form-based SmartCode, prioritizing infill development. "Before we launched this, there were about 84 dwelling units downtown," he says. "Now there are about 2,700."

With the goal of luring the type of private development the city wants in the area, San Marcos is making itself more attractive. "One of the most important elements in creating 'quality of space' is how we handle our public right-of-ways," Lewis says. Before, he adds, "curb lines didn't match, there were broken sidewalks, and there were no street trees to provide shade as a way to encourage people to get out and walk."

Lewis's department helps facilitate new development, partly by coordinating with the city engineers on street design. This involved redoing thoroughfares and lane dimensions, creating new pedestrian crossings, and organizing public rights-of-way.

"We also closed several driveway entrances into the public realm to make it more walkable, so people have less uncertainty when walking, and we pushed loading zones into alleys," says Lewis. "We also added street trees, pedestrian furniture, and street lights."

According to Lewis, the most important key to success has been widespread collaboration. In addition to engineering, "we have been working with our capital improvement department and our municipal electric utility to move utilities underground," he says. In addition, the cable and phone companies have franchise and pole attachment agreements with the city, so they have committed to burying their lines in conduit installed by the city when electrical wires are undergrounded.

Two undergrounding projects have been completed: University Boulevard and Hutchinson Street. A third phase is under way.

City ordinances do not yet require that new electric lines be buried throughout the city as it continues to grow. However, Lewis says, "At the end of our current projects, we will be doing a full development code rewrite, and we will have that conversation then."

Palo Alto: going all out

Since 1965, the City of Palo Alto (California) Utilities, a municipal utility, has established the boundaries for 47 underground utility districts. Construction already has been completed on 43 of them.

"Two are in different stages of design and implementation, and the remaining two will start in the next three to five years," says Tom Ting, electric engineering manager. "Additional districts will be determined in agreement with AT&T, which is co-owner of the utility poles with the city of Palo Alto."

Between the work included in the underground utility districts and underground facilities installed with new developments, nearly half of the city's electric facilities are underground.

Establishment of the underground utility districts is handled by the utility company, along with the design, coordination with other utilities, and installation of substructures and electric conversion work, according to Ting. While the city's planning and community environment department is not involved in much of the undergrounding portion of these projects, it does guide the location and placement of the above-ground equipment, such as switches and transformers.

The city council requires underground lines for electric and communications services for virtually all new subdivisions and other construction. However, according to Ting, the council does allow the director of utilities to authorize poles, overhead lines, and associated overhead structures for new construction "when the director determines that an installation in an underground location in any particular instance would not be feasible or practicable."

Colorado Springs: long tradition

Colorado Springs has had an aggressive undergrounding program for decades, according to Carl Schueler, AICP, planning manager of comprehensive planning in the city's land-use review division. "Our distribution lines have been undergrounded as part of our standard development process for at least the last 30 years, and the majority of our city has underground distribution lines," he says. He notes, however, that some existing overhead lines that were too expensive to bury remain in place.

Schueler sees his department's involvement in burying lines as part of a broader effort. "Our role is to look at these projects from the perspectives of community development and urban revitalization," he says. "Our department coordinates with the utilities department on a regular basis in terms of land development policy, annexation policy, and other issues."

"Still, though, when we are involved in a transportation corridor project that involves rebuilding a road, and if there are power lines running along the road, in most cases those lines will end up underground," he says.

The city is also involved in the undergrounding of some transmission lines, which is a rarity in the U.S. These higher voltage lines that carry electricity longer distances are traditionally placed overhead. "However, the technology is now available to underground these lines," says Schueler. Most of the transmission lines in Colorado Springs are still above ground, but as opportunities arise, they are going under.

As in San Marcos, collaboration is key. "We are in continuous contact and communication with people in the utilities department," Schueler says.

Washington, D.C.: a combo

Another utility that has actively been addressing the overhead-underground issue is Pepco Holdings in Washington, D.C., which has a combination of both. "Overhead systems are not very reliable in heavily treed areas, and the Washington, D.C., area has a lot of very tall and mature trees that are well above overhead lines, which pose a risk to our overhead network," says Bill Gausman, senior vice president, strategic initiatives.

Also, he says, initiatives are under way to increase the city's tree density. "As a result, we are working with the city to make sure this is done in a way that doesn't add additional impact to the overhead system."

While Pepco does have a lot of overhead lines, it also has a long history with undergrounding. "A large portion of our system has always been underground, since congressional regulations prohibited overhead lines being built in certain portions of the downtown area from the beginning of electric service," Gausman says.

There are other challenges, including the higher cost of construction in an urban environment, where concrete-encased manhole conduit systems are required, says Gausman. "It is also more time-consuming to make repairs when an outage does occur," he adds. However, he notes that with the underground designs that are being used today, service can still be restored relatively quickly because of the redundancy and transfer capabilities in the system.

After a number of big storms hit Washington and caused power outages, Mayor Vincent Gray began to look for ways to make the electric system more resilient. "This was especially important in light of the fact that there are indications that the number and severity of the storms is likely to increase," says Gausman.

In 2012, the mayor created a committee jointly chaired by the city administrator and the chairman of Pepco Holdings. The committee represented a wide range of interested parties, including a number of city agencies and citizen councils. "Upgrading the district's infrastructure and related services has been a planning and funding priority," says Allen Y. Lew, city administrator for D.C.

All of the parties came up with a plan for legislation (which later was passed) that authorized spending to underground selective lines over the next seven or eight years. In June 2014, Pepco filed a plan with the city's Public Service Commission to move forward. "If we receive approval, we should be starting construction right after the first of the year," he says.

William Atkinson is a freelance writer, specializing in infrastructure and sustainability topics.

Resources

Images: Top — Pepco workers install underground power lines in Washington, D.C. Courtesy Pepco Holdings Inc. Middle — Overhead lines in Colorado Springs, Colorado. Courtesy City of Colorado Springs. Bottom — A transformer upgrade in Palo Alto, California, which has established boundaries for 47 underground utility districts. Courtesy City of Palo Alto Utilities.