Field crew swaps out wood poles with steel structures in mountainous region.
Tennessee Valley Authority (TVA) has gone to great lengths to keep the power on in the small communities of Sherwood and Anderson, Tennessee. With just 186 customers served by a section of line that winds through a mountainous region, it's no easy feat for linemen to replace aging infrastructure.
If a pole falls down in the mountainous area, it can take days for linemen to gain access and set a pole. In fact, two years ago, it took a five-person crew seven days to lay down, frame and set just four poles on the radial-fed line.
Because the poles ran next to a railroad track, the linemen weren't able to get their heavy equipment back to the work site. As a result, they had to transport the materials by hand, which took several days. They also had to de-energize the line to change out the wood poles, which were dated back to the 1930s and 1940s. The original line was built using oxen, mules and gin poles.
That particular stretch of line was up for inspection last year, and TVA scheduled nine more poles to be replaced in October 2011. The utility scheduled an outage for three weekends in October. By de-energizing the line for five hours at a time, the linemen were able to replace the poles and ultimately improve reliability in the region.
Marking Poles for Replacement
The 46-kV line runs from Cowan to Sherwood, Tennessee, and cuts across the Carter Mountain Range. The line has a total of 217 structures, and the section that winds through the mountains has about 89 of these structures. The line starts out as structure 1, and then structure 51 is 4.5 miles off the blacktop. From structure 52 to structure 95, it is another 3.5 miles from the blacktop accessed from the other side of the mountain.
In 2011, the linemen replaced nine of the wood poles with steel poles, but over the course of several years, crews have installed about 40 steel poles. Eventually, TVA plans to replace all of the wood poles in the mountainous region with steel structures.
The right-of-way dates back to 1936, and the line was constructed in 1942. A portion of the wood poles are original, while others have been replaced with other wood poles. Some of the 70-year-old poles are in fairly good condition considering their age, but the majority of these structures are either rotted at the grounded level or hollowed out by woodpeckers.
Oftentimes, a woodpecker will peck a hole in the wood pole, and then termites or bees will nest in that hole. Some of the woodpecker holes are big enough for someone to put their fist into them. For that reason, TVA is replacing the wood poles with steel poles from Valmont Industries.
Because the steel poles are lighter weight than the wood poles, they are easier for the linemen to transport to the work site. Once they install the steel poles, the linemen can climb them using step bolts. While they aren't installing these bolts in all of the steel poles, they keep them on hand in their trucks. Then when they need to climb a structure, they insert the step bolts into the predrilled holes.
Turning Down Poles
Every year, linemen inspect all the structures on this span of line. If they don't pass the inspection, then the workers “turn them down” or mark them for replacement.
As part of this process, linemen fill out an environmental review sheet and a pole change request form, and then send them to the engineers for review. The engineering department then decides on an appropriate replacement pole. In most instances, the linemen replace the old wooden poles with steel poles with two polymer insulators and a pin insulator on top.
Once the poles have been turned down, the linemen can no longer climb them unless they have prior approval from a manager. Often, when a pole reaches a certain age and point of deterioration, it can break easily.
Accessing the Remote Region
It's not practical for TVA to use helicopters to transport linemen into the remote area, so workers have to find alternate ways of getting to the poles. Whenever possible, they drive Polaris Rangers into the region. Many times, however, the workers have to walk through tall weeds, across rocks and over mountains to reach the poles.
The linemen faced constant hazards on foot. If they were to trip and fall, they would land at the bottom of the ravine. In addition, the treacherous terrain can do damage to the work trucks. To keep each other safe, they always tried to look out for their fellow union workers.
The linemen had to face some rough terrain such as outcrop and rocks. On one structure, they had to walk up to the edge of the right-of-way and then look down 10 ft to the top of a 40-ft pole. The 75-ft right-of-way then went straight down.
As they walked over large rocks on the right-of-way, the linemen often encountered obstacles. For example, some holes between the rocks are 12 ft to 15 ft deep. In addition, rattlesnakes often live under these large rocks. One lineman discovered three of these snakes when he flipped over a rock.
When the linemen encounter rattlesnakes, they are instructed to stay away from them. The linemen also protect themselves by wearing long-sleeved shirts, flame-retardant clothing, hard hats, safety toe boots, gloves and eye protection.
Building an Access Road
In the future, however, linemen may not have to contend with a precarious route to work. TVA is currently working on improving the access to the remote region for its maintenance crews.
The utility understands how hard it is for linemen to access the area, and the company has hired Three Rivers Construction to build an access road through the mountains. When possible, this contractor is trying to build this road close to the poles. That way, the crews eventually will be able to drive a crane, bulldozer and other heavy machinery into the area to set poles quickly and efficiently.
In the future, as more poles are marked for replacement, TVA plans to continue to extend the road. That way, the linemen will have a road that will allow them to access all of the structures on the line.
For the fall 2011 project, the contractor worked for about four-and-a-half months to create an access road to the nine structures needing replacement. One reason why it took so long for the contractor to carve out a road was the terrain. The span of line traverses a mountain, and underneath this mountain is a Civil War-era railroad tunnel. The Northern troops used this tunnel during the war to transport materials to their men.
To this day, this railroad tunnel is thought to be the longest hand-dug tunnel in the nation at 2,228 ft. The workers originally carved out this tunnel by hand, and they made ventilation holes that were 300 ft deep.
This tunnel goes underneath an entire mountainside, and in places, the poles are located about 60 ft to 70 ft from it. For that reason, the workers have to take care when moving rocks so they won't roll onto the tracks. The line runs on the east side of the railroad track, and to reach the poles, they had to go beside the track and over the tunnel. To make it easier to access the work site, the crew used part of the old railroad bed to access structures in the remote region.
Setting Poles in Rock
The linemen transported the poles into the region with a pole trailer and a crane. They also brought in a Boatswain chair and a bulldozer with an 80-ft boom to set the poles in solid rock. This machine from Linetrac has an auxiliary arm, a crane boom and an auger attachment to allow users to dig and set the poles. The crews used the machine twice in Sherwood four years ago, and it was of great use on this project.
Because they were working on the mountainside, the linemen had to find a way to do everything by hand and drill into the rocky terrain. Rather than digging a hole in solid rock, the linemen often set the new pole back into the same hole or had a new hole core drilled. They couldn't blast holes in the limestone because there is a 6-inch fiber-optic line on the right-of-way. It runs adjacent with the power line. As a result, the linemen had to bust the rock by hand with rock bits, sledgehammers and pencil point bars.
The linemen took the wire off of the old poles, pulled the poles out of the ground, dug as deep as they could, and then installed poles that were 5 ft taller.
The standard procedure is to raise the wire for more ground clearance. For example, the linemen are replacing 40-ft to 50-ft poles with 45-ft to 55-ft poles, though some poles will stay the same height.
In some cases, TVA had to move some structures to a new location. In these situations, the linemen worked closely with the engineers to identify the new location and height of the new structures.
TVA has been working on the line for years, and it could take a significant amount of time before it is all steel. At this point, the linemen are changing out the poles as they are turned down. Then the poles get changed out according to the budget.
By improving access to the structures, the utility is making it easier for linemen to inspect, maintain and install new poles in the mountainous region. One by one, the original wood poles are being marked for replacement, and the linemen are setting new steel poles, which will last for years to come.
Roy Arms (firstname.lastname@example.org) is a line foreman and has been with Tennessee Valley Authority for 16 years. His crew is responsible for maintenance, and operates cranes, retires lines, runs wire pullers and builds pads. They also change poles, run bulldozers, inspect power lines and check the condition of their tools and grounds.
Scott Ogles (email@example.com) is a journeyman lineman and has been with Tennessee Valley Authority since 1998. He began his career in line work in 1990 as an IBEW groundman and served in the IBEW apprenticeship, during which time he worked all over the Southeast and spent 18 months in California.
Linetrac Inc. www.linetracinc.com
Polaris Industries www.polarisindustries.com
Tennessee Valley Authority www.tva.gov
Three Rivers Construction www.trccompany.com
Valmont Industries Inc. www.valmont.com