DG Brings AC Pipe Bursting to Vermont
07.09.14
The American Water Works Association (AWWA) published a bulletin in 2010 titled Buried No Longer – Confronting America’s Water Infrastructure Challenge. The bulletin identifies the staggering investments necessary to replace the aging infrastructure in this country. Pipe replacement includes the cost of the pipe material but in most cases, the costs for excavation, backfill, and restoration of surfaces is much greater than the cost of the pipe itself. However, new pipe replacement methods referred to as “trenchless technology” have been developed in the past decade to reduce the costs for replacing existing water mains. Several methods of trenchless technology were developed to minimize (but not eliminate) the excavation necessary to replace these century old water mains. For instance, old corroded cast iron pipes of sufficient diameter can be cleaned and lined with small excavation access points required every 100 to 200 feet. Old pipes having more than sufficient diameter can be cleaned and slip-lined by pulling a new plastic liner through the old pipe with a minimum of excavation required. New pipes can be installed using directional drilling methods under buildings, rivers, and roadways using only an access point on each end and without significant disturbance along the pipe installation route. Finally, pipes with insufficient diameter can actually be burst apart as a new larger pipe is pulled through the old pipe. This method can facilitate increases in pipe diameter by about 25%.
Pipe bursting is a well-proven technology for replacing aging, deteriorating or undersized pipes in the water, sewer and storm drain industries. This technology limits the amount of excavation required on a project. By minimizing the amount of excavation and surface disturbance, the project duration can be reduced and the impact to the surrounding areas, businesses and residents is decreased. Many projects benefit from a significant cost savings when utilizing pipe bursting versus open trench replacement. Using pipe bursting, the old pipe provides the path for the new pipe and as such provides a final benefit from the investment made decades ago. Pipe bursting also limits environmental impacts as there is less excavation and equipment use, which lowers the project’s carbon footprint.
Pipe bursting is performed around the world for replacing a multitude of pipe materials. The pipe materials include those that you would expect such as clay tile, concrete, PVC, HDPE. In addition, pipe bursting methods can be used to replace cast iron, ductile iron and even steel pipe. However, replacing one type of pipe that is most conducive for replacement using pipe bursting methods has been problematic in the United States from a regulatory basis. This pipe material is commonly referred to as asbestos cement, transite or AC pipe. The regulatory hurdle in the US is due to the EPA’s current concern that any AC pipe that has undergone the mechanical process of pipe bursting should be subject to NESHAP (National Emission Standard for Hazardous Air Pollutants). In short, this would require an AC pipe bursting project site to comply with the NESHAP requirements for active and inactive waste disposal sites.
Fortunately, AC pipe bursting projects that have been performed in the United States have shown that compliance with NESHAP is possible. There have also been several studies on air quality for conventional open trench replacement of AC pipe versus pipe bursting. These studies have shown that the concentration of asbestos fibers in the air is lower during pipe bursting than for open trench replacement. In fact, the concentrations are lower than the limits set by OSHA.
There are a handful of states that have approved the use of pipe bursting for replacement of AC pipes. Many states have not considered the technology yet and a few states have prohibited the technology. There are many people in the utility industries working nationwide with individual states as well as the EPA to provide education on the benefits of this technology in regard to asbestos cement pipe replacement. With continued efforts on all levels, pipe bursting may become a cost effective alternative to open trench replacement of asbestos cement pipe.
Dufresne Group is working with both regional and national experts to develop methods to assure this cost effective technology can be used in Vermont to replace the miles of AC pipe that is reaching the end of its useful life.
