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 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 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

Table 1. Percentage of installed AC pipe per type of pipe system. Picture 1. Pipe bursting service pit with minimized impact.

hazardous chemicals, including asbestos. While NESHAP was a huge step forward in the protection of clean air, there have been significant advancements in technology since its adoption 40 years ago. The EPA issued statements in 1990 regarding AC pipe demolition to further clarify that if the AC pipe was left alone in place it would not be subject to NESHAP. If the AC pipe was removed, crushed or pipe burst, it would be subject to NESHAP standards. Many utility owners have elected to ignore or defer rehabilitation of its AC pipe rather than deal with complicated NESHAP regulations.

NESHAP concerns itself primarily with the release of asbestos fibers into the air that could be inhaled by workers because asbestos is not dangerous unless inhaled. During pipe bursting, the majority of the rehabilitation work occurs underground and the existing pipe is only exposed at service line pits of the inlet or outlet of the pipe bursting equipment and new pipe to be installed in place. The contractor responsible for pipe bursting of the AC pipe should follow the existing AWWA Guidelines “Work Practices for Asbestos Cement Pipes” that were adopted in 1995, which includes sufficiently wetting the AC pipe where exposed to ensure no asbestos fragments enter the air.

Future exposure of the general public, such as homeowners, to the segments of fragmented AC pipe are not likely as those remain within a few inches of the soil material surrounding the new pipe and homeowners are not likely to be digging as deep as the typical three feet of cover. The only agency that will have to deal with potential future exposure would be the agency that performed the pipe bursting rehabilitation and they would have ample records indicating the locations and would be prepared for such an encounter.

The use of pipe bursting to replace aging AC potable water distribution pipe was recently approved by the Drinking Water State Revolving Fund Program (DWSRF) as a qualified Green Project Reserve project at the City of Casselberry in Florida. The project was provided grant funding through the American Recovery and Reinvestment Act (ARRA) and has successfully rehabilitated over 20 miles of AC pipe using pipe bursting. Industry representatives worked very closely with the Florida Department of Environmental Protection (FDEP) and EPA representatives to determine how NESHAP applies to pipe bursting of AC pipe and how to comply with these requirements. This project meets all NESHAP criteria and has reinvigorated the process of trying to reshape NESHAP to meet current technology.

Through this project, industry members brought pipe bursting technology and the limitations imposed on it by NESHAP directly to EPA’s attention. In November 2010, industry representatives met with Washington, D.C. EPA staff to discuss the applicability of NESHAP to pipe bursting AC. Industry members presented detailed pipe bursting steps with videos of realworld application. The presentation alleviated certain misconceptions of the pipe bursting process. EPA suggested that the industry members develop an Administrator Approved Alternate document. The Administrator Approved Alternate document will outline a procedure to be followed for pipe bursting of AC pipe and is intended to allow the EPA Administrator and staff to approve alternate technology or practices without having to modify NESHAP, which is federally codified.

Industry members have assembled the AC Pipe Bursting Task Force to develop the Administrator Approved Alternate document and submit to EPA for review by fall of 2012. This task force consists of members from national associations, utility providers, engineers, contractors, technology representatives and pipe manufacturers. This task force is committed to utilizing available technology to develop a useful procedure for pipe bursting of AC pipe that is environmentally friendly, economical and mitigates the risks of handling AC pipe. The exemptions and clarifications will be inclusive so one comprehensive document, specific to buried AC pipelines, will be available for use nationwide and that any type of work on buried AC pipelines will be uniformly practiced and regulated, regardless of which state the work may be located in.

With over 630,000 miles of buried AC pipelines in the United States and Canada having reached, or quickly approaching, the end of its useful life, the Administrator Approved Alternate is the first step in making pipe bursting happen. Replacement or rehabilitation is imminent, and pipe bursting is a proven technology that is environmentally, socially and economically beneficial.

Picture 2. Fractured AC pipe resulting from pipe bursting as it will remain in the ground.

Edward Alan Ambler can be reached at (407) 262-7725 or eambler@ casselberry.org.