Take an industrial park with a 60-year-old clay pipe sewer line buried 10 feet below ground, add a road nearby that is highly traveled, and throw in a line break that has created a sinkhole big enough to hide a small car. The result? A real problem.
That was the situation facing Pete Charlton, vice president and general manager of Gastony Directional Boring, Inc., in Fort Smith, Arkansas, last July. Charlton founded the company in 1999 and has done many jobs in "pipe rehabilitation" — boring for sewer, gas, water, and electric lines primarily from Fort Smith north to the Missouri/Arkansas border. He and his eight employees were in the process of completing a project for the city of Fort Smith to replace many of that city's older sewer lines when an emergency situation popped up in neighboring Van Buren, Arkansas.
Van Buren, a city of about 20,000 on Arkansas' west-central border, is nestled at the foot of the Ozark Mountains. Van Buren features an industrial park that houses, among other companies, Simmons Foods, a poultry processing plant that releases about 200,000 gallons of wastewater each day in the industrial park's sewer main. About 60 feet of an old clay sewer line had collapsed beneath the industrial park and formed a huge hole at the intersection of Co-op Drive and 28th Street, a roadway that carries significant truck traffic every day. Another factor in this problem is that the Arkansas River is nearby and tends to flood the area.
Plans were already in the works to spend $1 million to $2 million to raise the road, but no work had yet been accomplished. City officials knew if the river spilled over into this area now, they would have a giant mess.
"We were asked by the city engineers to bring in our camera truck to provide video of the collapsed pipe in order to determine the exact location and extent of the collapse," says Charlton. "We went through from both sides of the collapse and determined that somewhere between 60 and 80 feet of the pipe was simply gone."
He speculates the missing pipe collapsed and was washed away by 200,000 gallons of scalding water that rushes through the pipes each day from the poultry plant. Heavy truck traffic and the old age of the pipe also contributed significantly to the development of the sinkhole.
In order to position the camera into the pipe, the crew used nearby manholes to get under the street and reach the collapsed area. Upon review of the videotape, the Van Buren Utilities Commission Board did not waste any time.
"This was an emergency. We got the job because we have done a lot of work rehabilitating pipe in Van Buren," Charlton notes. "There are a lot of large companies in that industrial park. If that sewer went out or the street caved in, it would have created several major problems. We submitted a price to do the work and the board and engineers then said, 'Get it done.'"
In all, about 400 feet of pipe needed to be replaced. Getting the new HDPE SDR 20-inch pipe in was the next challenge. The new 20-inch pipe came in 40-foot lengths. Charlton rented a fusing machine from ISCO, fusing the pipe above ground as it was pulled through the 400-foot bore.
Preparation was the key to getting this job done quickly and efficiently. In order to complete the project, Simmons Foods agreed to a 24-hour plant shutdown beginning on a Saturday morning. Charlton, Jeromy Dutra (his supervisor of 10 years), and the Gastony crew spent two days prior to the shutdown prepping the job site. This included excavating the entry and exit pits, setting up 6-inch bypass pumps, positioning traffic control signs, and excavating a pit along the road by the manhole. Simmons Foods and several smaller companies agreed to shut off their water supply and not discharge water once the project began. Charlton and his crew had the next 24 hours to complete the job.
Charlton decided to burst the old clay pipe using a HammerHead® impactor; a Vermeer® NAVIGATOR® D36x50 Series II horizontal directional drill, which he had purchased about six months before this job; and a 24-inch reamer to break up the clay pipe and collapsed material that was left.
"We bored through 60 to 80 feet that were simply gone — the pipe was full of dirt," Charlton says.
"The impactor was an important part of the process," he says. "That old 18-inch pipe was so thick that it had to be dealt with and removed. We used a biodegradable bore gel to slurry up the water and make sure the pipe pulled through smoothly," Charlton says.
Charlton and his crew also had to negotiate the new line through an existing manhole. Since the city didn't want the street dug, Gastony reamed out the manhole and made it big enough to pull in the 20-inch pipe. Once the pipe was in place, they grouted the area around the pipe.
"Using HDPE pipe was an important consideration for this project," Charlton says. "We often install HDPE around processing plants, because the caustic acid that comes from the plants doesn't affect the HDPE pipe at all."
The expected life of the new HDPE system in simulated tests is more than 100 years. According to Charlton, older cast iron pipes develop calcium deposits, significantly reducing pipe capacity. "Nothing clings to HDPE pipe," he says.
The city's main objective was to replace the old 18-inch clay pipe with 20-inch HDPE pipe with minimal interruption to the traffic. "They didn't want traffic stopped, and it didn't," Charlton says. The poultry plant was able to find a silver lining to the downtime, using it to update and maintain some of its manufacturing technology.
The entire project — which cost $68,000 — took just over 10 hours. Charlton says he had estimated that it could be completed in six hours. Why the time difference? "Everything worked as we expected, but it was just slower going," he says. "It went inch by inch, slow but smooth. It just took a little longer to pull in the larger pipe." Compared to past jobs, Charlton says he would rate it as "up there" among some of the toughest.
"Gastony has had jobs boring under rivers and swimming pools, but the pipe sizes on those jobs were all between 4- to 24-inch," he says.
Charlton's advice to other contractors who might be considering a similar job is simple: know the costs of running your boring machine. "There are boring contractors who do not take into consideration what all the expenses are to just to turning the boring machine on," he says. "In addition to diesel fuel, labor, trucks, insurance, and cost of materials, there are many other expenses to consider. Other expenses might include site restoration, depth of pipe, size of pipe, and the cost of excavating to tie in laterals and mains to the manholes."
In the end, the customer — the city of Van Buren and its residents — got what they wanted: the integrity of the road was maintained, traffic was not stopped at a busy intersection, and the dangerous problem was fixed. And the Gastony Directional Boring team has a job that will go down in its books as one of its toughest.
Gastony D.B.I. is one of several companies owned by Forsgren, Inc., a fourth-generation heavy civil contractor, located in Fort Smith, Arkansas. Forsgren, Inc. was started in 1936 by three brothers. Today, it has 160 employees and is run by CEO Steve Forsgren and his two brothers, Dallas and Justin.
Provided By Vermeer Manufacturing Company, Pella, Iowa