Going underground: aerial lines remain more economical, but advantages pushing more...

Burying utilities is nothing new.

Water, sewer and natural gas lines have traditionally been buried for centuries and more than 40 years ago, the first electrical and telephone cable began being placed underground. By the 1970s. realtors were promoting new residential developments with "all-underground"

In the years that followed, cable television companies built outside plant, much of it underground, and cross-country long distance cables were buried; then in the 1990s, the information highway was constructed with long-haul fiber optic cable buried in underground ducts.

Today new communications and power cable is routinely placed underground and failing cable buried 20 and 30 years ago is being replaced, often by horizontal directional drilling in order to avoid or minimize disturbance to surface improvements.

Yet, a surprising amount of cable remains suspended from poles and new aerial construction is under way in many areas. In some instances, already-crowded easements complicate installing new underground conduit or cable.

How much electrical and communications cable is still being built overhead and how much goes underground? Unfortunately, industry trade associations do not gather such statistics. To compile such information would require contacting individual service providers and following up on a regular basis to update statistics,

To provide an overview of the underground/aerial picture today, Underground Construction contacted several power and telecommunications companies and asked how they determined whether to place cable in the air or underground.

All of them are committed to under ground construction. However, they all still build and maintain aerial plant, and some say they replace damaged or failing aerial cable with new aerial cable because it is less expensive than rebuilding underground. And, even though underground cable isn't susceptible to damage by severe weather, service is too frequently disrupted by construction accidents which, some power companies claim, can be more difficult to locate and repair than aerial cable.

Telecommunications

For SBC (Southwestern Bell Corporation), most new outside plant goes underground, says spokesperson Wes Warnock.

"It depends on site conditions, but our first desire is to place cable underground for protection from the elements and for longevity," he explained. "For services to homes, underground is the first choice."

When aerial cable is replaced, SBC puts new cable underground whenever possible. Failing buried cable also is replaced with new underground cable when conditions permit.

"We replace cable by the most economical means possible in each situation," Warnock adds. "However, at the present time, we are not replacing significant portions of our underground plant."

Warnock believes that increased demand for broadband services will increase levels of outside construction.

"We recently announced a fiber-to-node strategy, and demand for broadband is a part of that," he continues. "We are looking to do fiber to the home soon and, in fact, are already installing fiber to business customers and will continue to lay fiber to multi-tenant structures and single-tenant businesses."

About 85 percent of the outside plant in BellSouth's nine-state service area goes underground. "We have a lot of trees and severe weather that produces ice, high winds, tornadoes and hurricanes," says ,Jimmy Stapp, general manager of network utility operations. "There is a lot of damage Mother Nature can do, so it's best to be underground. In most subdivisions, plant is buried and services go underground. Most new high-speed data cable also is going underground."

Stapp says that BellSouth has a continuing program to replace old cable and new cable goes underground everywhere that conditions permit.

To bring broadband to homes, Stapp says BellSouth runs fiber cable to curbsides, then goes to houses with coaxial or copper cane, most of it buried.

Another factor encouraging the underground trend is rising pole rental rates. "The parity on pole rentals is significant," Stapp says. "It is costing more to put our cable on poles owned by other utilities, so in some rural areas where we would have been aerial, we are going underground."

The majority of new outside plant for Cox Communications is underground, says Dick Mueller, vice president for network planning, engineering and operations.

However, Mueller says given the option of going aerial or underground, Cox generally constructs overhead because of cost factors. Old aerial plant that must be replaced generally is put back on poles.

"If there is no aerial option," he continues, "underground cable is replaced with underground cable using the most cost-effective method possible under local ordinances."

However, Mueller says most needed plant upgrades are complete, and the amount of replacement work is decreasing, rather than going up.

For fiber to end users, Mueller says that some large commercial customers are provided fiber feeds and that practice will continue.

Underground power cable

In California, Pacific Gas & Electric (PG&E) places virtually all power lines in new developments underground.

"There is a state law that requires in any new development, all utilities be located underground," says PG&E spokesperson Paul Moreno. "There are exceptions, acreages or small additions with only a few houses, but in virtually all new developments electric, telephone and cable television services are underground. Developers pay the costs for installing the services."

While much aerial cable remains in place, PG&E places up to 230 kV high voltage lines underground. "Improvements make today's cable much better for underground placement," says Moreno. "In the old days, some cable was wrapped in lead. Today insulation and sheaving is much better."

Moreno says the California Public Utilities Code has provisions for cities to convert aerial plant to underground.

"Based on a formula taking into account existing overhead cable and the number of meters, cities can convert to underground in selected areas when it can be shown as a benefit," he continues. "Usually it is for ascetic reasons--in downtown and scenic areas. The utility pays for the conversion, but there is a process for recovering the costs."

Moreno says PG&E makes no claim that underground service is superior to that provided by overhead cable and adds that typically problems with underground cable are more difficult to pinpoint.

Detroit Edison finds it practical and cost-effective to bury power cable in residential areas and industrial parks, but continues to place major transmission and distribution lines in the air.

"We have and continue to review the benefits of underground versus overhead construction," says Alan Yonkman, director of service center operations. "The benefits for underground residential distribution (URD) within new subdivisions and industrial parks is valid. However, for major transmission and distribution installations, the benefits are far outweighed by the cost. The differential in cost varies from 10 to 1 up to 40 to 1, depending on the type of installation. In addition, when an underground failure occurs, the time to troubleshoot and the cost of the repair is significantly higher than an equivalent overhead installation."

Cobb EMC, Marietta, GA, provides energy for five counties in the booming Atlanta metro area. The electric membership cooperative has been placing power underground for many years and is a pioneer in the use of horizontal directional drilling.

In the early '90s, Cobb EMC was one of the first power providers in the country to use directional drilling, purchasing one of the first HDD machines to be put in service in the state. In the years that followed, Cobb replaced 60 to 70 miles a year of buried services that had been in place since the 1970s. In recent years, reconductoring by directional drilling averages 25 to 35 miles per year. Currently, Cobb EMC is extending power to more than 50 new developments, including new subdivisions, apartments and additions to established subdivisions.

"All cable goes underground," says Chip Nelson, chief operating officer. "That's what consumers in this area want. it is their perception that service is better and cable is protected from wind and ice. And they simply don't want overhead wires in their neighborhoods."

Main feeder lines remain overhead

"Generally," says Nelson, "we come from the substation underground, then go to poles, then back underground. Of our 160-plus circuits, we have a few that are totally underground, and they are in dense commercial or industrial areas."

In Oklahoma, Edmond Electric, the city-owned power provider for the Oklahoma City suburb of Edmond, is completing a $1 million program to replace deteriorating aerial cable serving 465 residences in an established neighborhood with new underground cable.

The prject may lead to eventual replacement of all residential power distribution cable underground, says Charlie Burgett, P.E., Edmond Electric utility director.

Burgett says the decision to undertake the conversion to underground came following one of the area's worst ice storms in late January 2002.

"Our strategic planning team recognized this type of project would improve system reliability and address concerns about deteriorating electric facilities," he explains.

Edmond Electric managers believe kite city ultimately will recover the investment from reduced repair and maintenance COSTS, while customers enjoy improved service without all increase in rates they pay for electricity.

High voltage cable was placed in street right-of-way in front of homes; low volt, age lines are buried in backyard easements, says Dean Sherrick, Edmond Electric distribution superintendent.

Contractor directional drilling crews installed HDPE conduit in the easements, and new cable is placed inside the conduit.

"Directional drilling," says Sberrick, "limits the amount of excavation needed, greatly reducing damage to lawns and makes it unnecessary to cut through streets and driveways."

Property owners have the option to convert services to their homes from overhead to underground. Edmond Electric will bury the cable at no cost, but homeowners who opt for the switch must pay an electrician to install a new meter base to route underground service.

Sherrick says public reaction to the project has been good, and the city is pleased with the result.

Feeder circuits in Edmond remain overhead. However, Sherrick says the city has budgeted for a study to address the feasibility of putting feeder circuits underground, too.

"There are pros and cons either way," Sherrick concludes. "Overhead cable has exposure to the elements and that's a factor, and over time underground cable can have failures and there is always the threat of accidental damage. However, we have been very fortunate in that respect. We do our own one-call locates, and our personnel are very accurate, and that helps avoid accidental strikes."