WATER SUPPLY/Midwest city bursts pipes to make repairs
Facing growing delivery demands and aging infrastructure, Belton, Mo., replaced a portion of its water system, including main and service lines. The job, which took four months to complete, incorporated trenchless technology, saving the city time and money over open-cut alternatives, and minimizing disruption to the community.
With a population of 23,000, Belton has grown by 5,000 residents over the last 10 years. New home starts and attendant development were straining the water system, which was originally installed in the late 1940s and early 1950s.
In 1995, the city began replacing some of its undersized pipes. “We installed and re-routed a 16-inch main line to replace an outdated 6-inch main,” says Cliff Fain, public works supervisor for Belton. “After bringing that main into service, we began experiencing problems with the rest of the system.”
The pressure delivered by the new 16-inch line was more than the original pipes could handle. The number of line breaks increased, as did seepage. Additionally, corrosion and sediment restricted flow in the original cast-iron pipes by as much as 45 percent.
By summer 2000, the city planned to replace some of the system’s damaged and undersized sections, but, because of the project scope, officials determined that open-cut methods would be too disruptive for residents. Having used pipe bursting in some of the city’s sewer projects, Fain decided to give it a try with the water system.
The project contract was awarded in July, and locally based Wiedenmann & Godfrey Construction began replacing 4,500 feet of 4-inch water main with 8-inch HDPE pipe. Using a pneumatic pipe bursting tool (the Grundocrack Hercules from TT Technologies, Aurora, Ill.), the company was able to fracture the host pipe and, simultaneously, pull in the new pipe.
The project proceeded in 600- to 700-foot segments until November. In addition to replacing the main, crews used trenchless methods to replace service lines, which were connected to the main using electro-fusion saddles. The contractor tested and chlorinated each new section of pipe before putting it into service.
By using pipe bursting, Belton was able to save money that otherwise would have been spent on open-cut design and planning, Fain says. (The city budgeted $718,000 for open cutting, and the actual cost of pipe bursting was $457,000.) “Because pipe bursting follows the path of the existing line, we didn’t need to hire an engineering firm and draw out an elaborate design,” Fain explains. “We generated the design in house and saved a lot of time and money.”
The savings allowed Belton to expand the scope of its replacement master plan. “The next section we are planning to replace is approximately 32,000 feet of 4-inch and 6-inch cast iron pipe,” Fain says. “I anticipate that as much as two-thirds of that will be replaced by pipe bursting.”
