Pipe bursting of asbestos cement pipe: making it happen Edward Alan Ambler, P.E., LEED AP Water Resources Manager City of Casselberry, Florida
any efforts have recently been made by the Environmental Protection Agency (EPA), the American Water Works Association (AWWA) and other entities to accurately portray the capital required to rehabilitate the United States’ water and wastewater infrastructure. These agencies have come to a similar conclusion: A significant investment is required now to not burden the next generation of Americans with skyrocketing costs of infrastructure rehabilitation. The recent AWWA document “Buried No Longer: Confronting America’s Water Infrastructure Challenge” states the necessary capital required to replace existing water systems and keep up with new demand will be $1 trillion over the next 25 years. Large portions of many utility distribution systems in the southern and western United States are made up of asbestos cement (AC) pipe, which was a popular pipe material from the 1930s to the early 1970s. While it is difficult to accurately measure how much remains in the
Table 1. Percentage of installed AC pipe per type of pipe system. 60 APWA Reporter
August 2012
ground and what condition it is in, there is an estimated 630,000 miles of AC pipe in the United States and Canada, and much of the existing AC pipe is nearing the end of its typical service life of 40-60 years. Pipe bursting is an industryproven technology for trenchless replacement of existing underground conduit systems, such as water, sewer, and gas. The existing pipe is replaced in situ with a new pipe of the same size or larger. Pipe bursting is typically performed using pneumatic or static pull methods where the existing pipe is fractured and displaced outward while the new pipe is pulled into place along the existing pipe alignment. The burst segments of the existing pipe are left in place in the vicinity of the new pipe. Because the replacement pipe is inserted into the exact location of the existing utility, no additional right-of-way is necessary and there is no impact to other existing utilities, as could occur through new utility installations. Job site conditions most cost effective for pipe bursting are urban settings that contain roadways, drainage systems, and other existing utilities that would prevent or inhibit conventional open-cut installation of a new pipe system. Pipe bursting requires substantially less excavation than conventional open-cut which minimizes impacts to developed neighborhoods and commercial areas with established landscaping. Pipe bursting generates significantly less
Picture 1. Pipe bursting service pit with minimized impact.
dust, nitrous oxide emissions, and erosion and sediment runoff. With proper planning, the pipe bursting contractor can often reduce outof-service time of the utility to a six-hour time frame. Pipe bursting projects typically also progress faster than traditional open-cut projects thus providing fewer nuisances to residents and customers. While record drawings or geographical information system (GIS) database drawings are the best information for designing and planning a pipe bursting project, other maps such as aerials or field drawings can also be used. The National Emissions Standards for Hazardous Air Pollutants (NESHAP) is a document promulgated by the EPA in the early 1970s that was intended to regulate handling of
