Ready for Inspection

So far, your towers have held up fine, but will they be with you over the long haul? Extra weight from ice, wind, other carriers' equipment and additional antennas will weaken any tower over a period of time. If you don't catch the wear and tear, it eventually can put a tower completely out of commission. A strict maintenance program can ensure your towers are present and accounted for in the years to come.

Your towers take constant hits from Mother Nature, especially in coastal locations or areas susceptible to tornadoes and storms. To help prevent corrosion in these areas, Robert E. Kramm, International Towers (ITI) director of engineering, discouraged carriers from using hollow tower members.

"While galvanizing techniques have proven lately that you can get galvanizing inside of hollow members and protect inside, you can't inspect them," he said. "You can't verify that corrosion is not occurring inside a tower leg or inside a hollow member."

You can take other measures to protect against corrosion. For example, Bell Atlantic Mobile (BAM) frequently re-paints towers in regions with intense sunlight, heat or wind to maintain sufficient protection, said Bill Stone, executive director, northern New Jersey networks. He added that ice puts the most significant load on a tower, so the company engineers its towers and foundations in the northern region to handle extra weight. Michele White, BAM northern New Jersey director of operations, said the company builds its towers to ANSI/TIA/EIA standard 222-F, which defines the minimum wind speeds towers should withstand in various counties. The standard further indicates that it is the responsibility of the tower purchaser to specify appropriate ice loads, but it does not state ice loading as a requirement.

"Tower purchasers looking for more specific information for a certain ar ea might be able to contact a local airport for wind speeds," she said.

Weather is not the only thing that can weaken your towers. Jim Wilbanks, Alltel senior engineer, pointed out that equipment overloading causes the most tower failures. Failures start in the legs of lattice towers, and monopoles deteriorate because of local buckling or compression failure in the steel.

ROUTINE CHECKSCellular carriers, who own some of the oldest towers in the industry, said the secret to a long-lasting tower is a strong maintenance program.

"If you properly maintain towers, they can last for decades, so the real key critical issue is maintenance," said Lisa Bowersock, AirTouch spokesperson. "If the steel is painted, not overstressed, and inspected on a routine basis, then we expect the tower to last for decades."

Wilbanks agreed. If the protective coating remains on the tower and the members are not stressed beyond the load for which they have been designed, cellular towers should hold out for 40 to 50 years, he said, just as utility towers have.

The most important element of a proper maintenance program is regular inspection. But carriers' opinions differ about how often you should inspect towers. United States Cellular, for example, inspects its towers nine months after it builds them to make sure the bolts and guyed wires are still tight. Over time, the tower strings stretch, and the tower settles, said Dave Sherr, United States Cellular director of network operations, southeast region. The carrier hires a company other than the original builder to inspect the tower.

"You don't want the fox watching the hen house," he said.

After the first examination, United States Cellular conducts a thorough inspection every three years.

In special cases, United States Cellular will inspect more often. After a harsh storm, for instance, a crew will evaluate towers that were in the path no matter how recently the tower was inspected. These cases include storms with wind speeds higher than the tower's design load can handle, Sherr said. Whenever United States Cellular lets another carrier co-locate onto a tower or adds more of its own dishes or antennas, it analyzes the tower loading and re-inspects the structure.

ITI's Kramm said that even under normal conditions, three years is not an adequate inspection schedule.

"An awful lot of damage can result in that time," he said.

He suggested that carriers conduct a full inspection every year. Monopoles and towers made from hollow pipes should have their drain holes inspected at least that often to make sure they are clear of debris. Clogged holes trap moisture inside the members, which causes corrosion from the inside.

"My impression is that carriers simply don't have a good inspection schedule," Kramm said. "They tend to let it go too long. I think someone is trying to make a penny-wise decision that in the long run may catch up with them."

However, Sherr is pleased with United States Cellular's inspection schedule.

"Every three years is often enough," he said. "Any more often than that, under normal circumstances, is a waste."

Other carriers go even longer between inspections. Bowersock said AirTouch inspects towers at least once every five years. If it must do other work on a tower, such as replacing antennas or repainting, a crew runs an inspection simultaneously.

"We inspect guyed towers on a more regular basis because they do have multiple points of entry into the ground, so they have more areas susceptible to corrosion," she said.

BAM's schedule is even less frequent, as it inspects 10% of its towers every year, according to White.

Sherr said preventive maintenance is just as important as full inspections. Twice a month, United States Cellular employees visit sites to check the anchor heads, tower foundations, grounding, CAD welds and more. Although they don't climb towers during these visits, they will check out the towers with binoculars to decide if anything looks out of place.

"As often as they get out to the sites, they should notice if anything is abnormal," he said.

TEAR DOWN OR BUILD UP?During any tower inspection, you are bound to find something wrong. You often have to replace deteriorating sealing and weatherproofing around connectors or tighten jumpers that have come loose because of frequent wind. You can fix these problems easily. Other times, however, you must call in reinforcements.

Kramm said you should reinforce your tower when you are adding new equipment and when an inspection reports damage to tower members. If you will not be adding equipment, you can usually order new parts from the original manufacturer to replace damaged members, he said.

When you do have to add equipment, Kramm recommended shortening guyed wires or adding extra main-leg, cross and secondary members to reinforce the tower. Some people have suggested filling hollow legs with grout or attempting to stabilize the tower while replacing an entire leg, but he warned that these processes are difficult and dangerous.

Sherr pointed out that you can install additional guyed wires and guyed anchors to add strength. Often carriers will leave holes on the sites for future guyed anchors and wires. You also can buy sleeves that fit around tower legs to stiffen them.

In other situations, carriers must modify a tower's foundation, either because it can't handle an additional load or because the soil underneath is weakening. Alltel's Wilbanks said he normally widens the area where the foundation bears against the soil to reinforce the foundation.

Howard Richard, Alltel staff manager of property management, said if tower modifications reach a point where the company will have to spend an exorbitant amount of money to strengthen the tower or foundation, it will replace the structure instead.

"It is not as though when we build a tower we expect it to last for eternity," he said. "Sometimes, timing is outweighed by the cost factor."

To facilitate an immediate changeover and maintain service, Alltel sometimes builds towers next to existing towers in phases, then transfers equipment over.

Other carriers have had to tear down parts of towers. In one situation, United States Cellular had to remove the top section of a tower because the anchor pulled out from the side of a mountain that held it in place.

"The weight at the top was too much, so we pulled off a top section of the tower to keep it from falling down," he said. "By taking the top off, we reduced stress on that guyed point. If we continued to try to load that top over time, it would have created a problem."

United States Cellular has never had to tear down an entire tower because of structural problems, but there have been times when it wanted to co-locate on existing towers that could not support additional loads. In these cases, the company offered to pay for a stronger new tower next to the existing tower, Sherr said. Likewise, BAM has never had a tower failure. However, White said if the company inherits a tower through a merger or acquisition, it often will replace the structure.

Kramm said the best way to measure the cost of rebuilding against reinforcing is to give a list of repairs to the original manufacturer, then compare the cost of replacing parts to the price of building a new tower. You also should consider that when adding new equipment, the foundation might not be able to support the increased load.

"You must ask yourself if it is less expensive to build a new structure versus trying to reinforce the old one," he said.

The advent of co-location over the last five years has prompted carriers to strengthen their towers for future sharing. In some cases, the tower may not have been engineered well enough to handle additional cables and antennas, Stone said.

"We have, on numerous occasions, gone out and made major modifications to our existing towers in an effort to strengthen them so that we can allow for co-locations," he said.

Kramm said other cellular carriers are facing the same situation. They built older towers under an old design standard before anyone thought about co-location. Today, almost any tower in a decent location has been considered for co-location.

"It is very important to have a registered engineer take a look at a tower before you have any antennas added," he said.

Often OverlookedEven the most stringent tower inspection won't catch everything. Cellular carriers with almost 20 years of tower-maintenance experience have seen some of the most obvious things overlooked.

"It is very important that you inspect guyed wires on a regular basis. The biggest maintenance item has been guyed wires," said Michele White, Bell Atlantic Mobile (BAM) northern New Jersey director of operations.

Dave Sherr, United States Cellular director of network operations, southeast region, said checking every single bolt is next to impossible.

"There are just so many that the chance of them finding every single one that is loose is not going to happen," he said. "Over time you are likely to catch 70% of them, but there are probably a few that you can turn with your fingers up there."

Bill Stone, BAM northern New Jersey director of networks, said if he could offer start-ups one piece of advice, it would be to use lattice towers as a first choice, followed by monopoles.

"The lattice tower is probably the most flexible structure that is available. It can be strengthened the most easily, heightened the most easily," he said. "In general it might not be the cheapest, but it is the most flexible over the long haul."