The up-front cost of pipe and pipe-bursting equipment—roughly $250,000—is actually higher than the initial cost of a traditional open-cut project. And restrained-joint PVC can cost up to three to four times as much as conventional PVC sewer pipe. But with trenchless PVC pipe installation, costs are offset by:
- Increased speed of installation, which lowers labor costs
- Reduced expenses for disposing sewer-contaminated spoil dirt
- Reduced volume of new embedment
- Reduced flex base and street patching.
And even though each tap on the old main must be located and re-tapped when the new main is installed, there's still a huge savings in time and material. Excavations are reduced and the need for destroying and replacing sidewalks, asphalt, trees, and grass is eliminated.
Plus, trenchless methods minimize the use of support equipment, which also means less fuel consumption and wear and tear. Because other equipment is not worked as hard nor as often after you convert to pipe bursting, it will last longer.
We were so impressed by the results of these projects, that we bought the Grundoburst 800G in March. Our crews are already using the new equipment to replace clay mains—with at least 50 more miles to go.
— Harris is director of utilities for the city of Brownwood, Texas.Same culprit, different solution
An Indiana city replaces water mains under a three-lane street with minimal disturbances.
Soil was also the culprit that damaged cast-iron water mains in Indiana's second-largest city.
Installed in the 1930s in Fort Wayne's 200-home Belmont Addition neighborhood, the 11,000-foot water main suffered corrosion over the years, partially caused by the region's soil. Since the soil is mostly composed of clay, it soaks up and holds moisture, becoming a corrosive environment for unprotected pipes.
Because a busy street runs through the area, Fort Wayne City Utilities wanted to replace the damaged water main with minimal disturbances. The answer was directional drilling. City contractor S&S Directional Boring chose to replace the corroded pipe with 6-inch Certa-Lok C900/RJ restrained-joint polyvinyl chloride (PVC) pipe—which stands up better against corrosion than cast iron and is not as expensive as other materials.
“Directional drilling has proven itself to us over the years as the most cost-effective method of replacing water and sewer mains in busy or congested areas, but this is one of the first times we've used PVC pipe for a directional drilling project,” says Matthew Wirtz, Fort Wayne's assistant manager of planning and design. “Since the project was taking place in a residential area, we wanted to avoid having several hundred feet of fused pipe strung out for several days. The fact that the pipe is assembled as it goes into the boreholes was a huge advantage.”
S&S Directional Boring began drilling last September with crews ranging from eight to 12 workers and finished the job in April. After making adjustments to optimize drilling through the extra-hard clay, the crew completed the project with minimal difficulties.
“It turned out well,” Wirtz says. “We've received positive feedback from the contractor and our maintenance workers.”
Since completing the project, the utilities division has used PVC pipe in other directional drilling projects.
— Steven Gross, PE, is director of marketing with Valley Forge, Penn.-based CertainTeed Corp.'s Pipe Business.Web Extra
To view a slideshow of how the PVC pipe was installed, click here!