Bursting Under Buildings

Deteriorating sewer mainsDeteriorating sewer mains are a common problem that cities across the United States face every day, but deteriorating sewer mains that run under multi-million manufacturing facilities are a different story. Careful planning and execution are a must, and choosing the right trenchless approach is of the utmost importance.
Recently that scenario unfolded in Carrollton, Ga., home of one of the largest wire and cable manufacturers in North America, Southwire Co.

According to Carrollton assistant city manager Tim Grizzard, the original building where the Southwire’s manufacturing facilities sit today was built right on top of a storm sewer main and a sanitary sewer main sometime in the 1960s. The City of Carrollton was aware of the potential issue this could raise and has had the sanitary sewer main on its radar for years leading up to its replacement.

“I’ve been with the city going on 10 years now and when I started, our public works director took me out near the Southwire plant and showed me a section of sewer main,” Grizzard said. “It was the same main that traveled under the Southwire facility, but it was a little downstream. He said, ‘This is going to be a problem someday.’”  

That time came in February 2013 when the section of line downstream of the Southwire plant failed. The City replaced a total of approximately 1,400 ft that included sections of concrete, corrugated metal pipe and some ductile repairs.

For that project, the City contracted with 3 Rivers Utility Rehab LLC, in nearby Roopville, Ga. After replacing that section in late February 2013, the City approached Southwire with its concerns about the line running under the building wire plant. Plant officials also expressed their concern, and the two entities decided the line should be replaced at the earliest convenience.

Deteriorating sewer mainsSouthwire Background

Southwire Co. is North America’s leading manufacturer of wire and cable used in the distribution transmission of electricity. According to the company’s website, its roots extend to 1937, when Roy Richards started a company to erect power poles. Over the years, Richards grew Southwire into a leading player in the wire and cable industry.

Today, Southwire delivers power to millions of people around the world. Its utility cable and building wire carry electricity to wherever it is needed. One in three new homes built in the United States contains wire made by Southwire. Southwire leads the industry with innovative products that simplify installation, saving customers time and money. Southwire produces wire and cable solutions for any commercial, residential, industrial or utility applications.

Southwire’s corporate structure centers around four distinct manufacturing segments — Energy, Electrical, OEM (Original Equipment Manufacturing) and SCR (Southwire Continuous Rod). Each focuses on a specific group of products and customers.

Building a Case for Bursting

According to Grizzard, the City exhausted several other options before deciding that bursting under the plant was the best option for successfully replacing the sewer main. Grizzard looked at re-laying the pipe, as well as HDD options and sliplining. But ultimately because of the pipe’s location and the location of buildings, creeks, lakes and other obstacles, none of the other alternatives proved economically feasible or were simply quick fixes for a problem that needed a definitive solution. Static pipe bursting was selected.

Utility contractor 3 Rivers Utility Rehab is well versed in the pipe bursting method. Since 2000, 3 Rivers has rehabbed more than 10,000 lf of old clay sewer lines for the city of Carrollton and was the first choice to replace the deteriorating sewer main underneath the Southwire facility.

TT Technologies pipe bursting specialist Eddie Ward provided technical support on the project. “Ryan Lawler and his crews at 3 Rivers are really solid when it comes to pipe bursting, and this project was no picnic. We had a line that traveled under a very busy manufacturing plant,” he said. “There wasn’t a lot of room for error and having 3 Rivers perform the work was a huge advantage that contributed directly to the success of the project.”

Deteriorating sewer mainsThe sanitary sewer line that needed to be replaced is a main artery line that serves the eastern portion of the city including several neighborhoods and the county jail, and then travels to the City’s 7 mgd conventional wastewater treatment facility.

“The line was probably installed in the 1950s, although we’re not one hundred percent sure. It was a 12-in. unreinforced concrete sewer main. A very large building was built on top of the line sometime in the 1960s,” Grizzard said. “It wasn’t a very wise decision, but it was the kind of thing that happened back then. So what eventually became Southwire’s building wire plant sits on top of the line. There are also two manholes inside the plant.

“We knew we wanted to do some kind of rehab on the line when the opportunity arose. That happened around the holidays. In addition to the sanitary sewer that ran under the building, Southwire also had two storm drains under the facility that needed replacing as well. When they brought in 3 Rivers Utility Rehab to handle bursting and replacing the storm drains, we saw this as the chance we needed to get the sanitary sewer, which is under the city’s jurisdiction, taken care of as well.”

Project Review

The City had the line profiled carefully in order to ensure no surprises during bursting. In addition to the challenge of bursting under the building wire facility, Southwire had an underground equipment tunnel that the line ran under as well. The fear was that when the tunnel was poured, the line was wrapped in concrete, as well. The surveyor checked the alignment of the sewer pipe carefully and marked the section that traveled under the tunnel so that the crew could core it and determine the pipe’s status in relation to the tunnel. It was determined that the line was not wrapped in concrete and bursting could begin.

The 3 Rivers Utility Rehab crews established launch and exit pits, outside, on either side of the 1,100-ft run. The project was completed in a single pull. A Grundoburst 1900G system from trenchless equipment manufacturer TT Technologies, Aurora, Ill., was used for this significant burst. For the burst, an innovative bentonite system was incorporated in order to provide adequate lubrication throughout the pull. After the Grundoburst was positioned in the pulling pit, crews rodded the existing sanitary main with Quicklock bursting rods to the launch pit. There, the bursting head, expander and fused HDPE product pipe were connected to the rods and bursting was ready to begin. The entire 1,100-ft run was completed in approximately 3 ½ hours.
The crews replaced the deteriorating 12-in. unreinforced concrete sewer main with 16-in. HDPE DR17 IPS. Grizzard said with the installation of the new pipe, difference was immediate and impressive. “We saw at least a 40 gallon per minute reduction in the amount of flow in the pipe because of the elimination of the infiltration,” he said. “When the pits were dug and crews began bypass pumping, the flow was 40 gallons per minute of groundwater, must likely coming from the nearby lake.”

The resulting savings from eliminating the infiltration problem are significant. According to Grizzard, 40 gallons per minute of ground water infiltration is the equivalent of $600,000 in plant capacity.

“We are very pleased with the work that Ryan and the crew at 3 Rivers Utility Rehab did. They did a great job for us and we couldn’t be happier,” Grizzard said.”

Jim Schill is a technical writer, based in Mankato, Minn.
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