Dawson PPD recently invested in an underground boring machine to assist with line construction. The plan is to bore power lines underground when they cross major roads and intersections. This way, the power lines are not restricting large equipment or house move clearances.
It’s big. It’s powerful. And it virtually leaves yards undisturbed.
Dawson PPD recently invested in an underground boring machine to assist with line construction. The plan is to bore power lines underground when they cross major roads and intersections. This way, the power lines are not restricting large equipment or house move clearances.
“The cost to hire a contractor to bore underground in one year was higher than the cost for Dawson PPD to purchase its own machine and hire an employee specifically for it,” said Manager of Operations Jeremy Kaiser.
Former Tree Crew Foreman Jared Bauer was offered the position to run the boring machine. He accepted the challenge.
“I wanted to be involved in this process that offers new opportunities and flexibility for Dawson PPD’s electrical system,” Bauer said.
Bauer is currently serving as an apprentice lineman and is studying to achieve journeyman status.
“Dawson PPD’s territory covers a large variation of terrain and soil types,” Bauer said. “Horizontal directional drilling allows us to bore under obstacles or environmentally sensitive areas where trenching and excavating won’t work.”
“Drilling also addresses two disruption factors,” he continued. “Landscaping and time. It displaces less soil and doesn’t require digging down into the property the entire length of the line. This preserves the landscape.”
How it works
Dawson PPD Apprentice Lineman Jared Bauer uses hand controls to operate the boring machine.
The boring machine drills into the earth about four to six feet underground. It fills the hole with a clay and water mixture to support it and avoid collapsing when the rods are removed.
Approximately 10-foot-long rods are inserted into the ground, one at a time, until the desired length is achieved. The machine can bore up to 1,000 feet across.
A locater tool is used by a lineman to locate the rods underground while boring. He uses spray paint to mark the location on the ground every 10 feet. This helps the boring machine controller see where the front of the rod is and ensures it is on course to reach its destination. Large rocks and other underground obstacles may make the rods shift as they bore, so it is important to check the progress and redirect the boring as needed.
Once the hole is dug, the rods are removed. Duct line is then inserted into the hole, and finally the conductor is threaded through. Each power line phase is marked with a different color of duct: blue, red and black.
“By putting in duct instead of just laying conductor in the hole, we are making it easier to replace failed or aging conductor in the future,” Kaiser explained. “It protects the conductor and avoids us having to excavate to remove the wire.”
Future use
Dawson PPD Apprentice Lineman CinJin Faber checks the location of the rods using a locator tool while his peers look on.
For now, the boring machine will primarily be used when power lines must cross major roads and intersections. However, there may be more use in the future.
“The cost to build overhead power lines is still more affordable than underground,” Kaiser said. “However, that cost gap is starting to close. Dawson PPD will evaluate each construction project on a case-by-case basis and conduct a cost analysis to see which method is more affordable and in the best interest of its customers.”
Both overhead and underground power lines last about 30 years.
December 2020