In the 1940s, 1950s and 1960s, more than 600,000 miles of asbestos cement (AC) – also called transite – was installed to transport water in potable water mains, storm drains and sanitary sewers in the U.S. Asbestos was used because of its light weight, corrosion resistance, rigidity and ease of handling. AC pipe accounts for about 15% of the total potable drinking water main pipe throughout North America (AWWA 2004).
But now, the 50-to-70-year life expectancy of AC pipe is up. AC pipe below ground is decaying and according to a 2015 study jointly funded by the Water Research Foundation (WRF), the U.S. Environmental Protection Agency (EPA), and the Water Environment Research Foundation (WERF), results in impaired water quality, reduced hydraulic capacity and higher leakage rates.
Water main renewal has historically been performed by open cut replacement of the pipe. But, this method is taking too much time. Other methods such as cured-in-place-pipe (CIPP) lining, sprayed-in-place pipe (SIPP) lining, pipe bursting and pipe reaming have been adopted primarily from the wastewater rehabilitation market for use in water distribution systems.
However, considerable concerns have been raised about some of these technologies used on AC pipe and asbestos fibers that may become friable causing a potential health hazard to workers and the public. As the Study highlights, real-world demonstration and evaluation of two rehabilitation technologies was conducted in Florida (pipe bursting) and Nevada (CIPP). Air, soil, and water samples were collected from each site and analyzed for asbestos by a certified laboratory. The results from the analyses showed the following:
- The level of airborne asbestos was always below the eight-hour time-weighted average (TWA) permissible exposure limit (PEL) of 0.1 fiber structures per cubic centimeter (s/cc) of air set by the Occupational Health and Safety Administration and posed no threat to the workers’ health (OSHA 2014).
- Soil samples collected at each site indicated only trace amounts of asbestos in the soil surrounding the pipe. With no increase in asbestos following the completion of the renewal activities (especially in the case of pipe bursting) it was determined that neither renewal method adversely impacted the soil environment.
- The results from the water samples collected from each site showed that the renewal technologies had no negative impact on the water quality, and in one instance, reduced the asbestos detected after bursting compared to before bursting.
Recommendations From the Study
While the results above seem positive the Study concluded that “very little real-world data exists on how the AC rehabilitation technologies studied impact the environment.” The following recommendations were offered in the Study:
- Regulatory agencies should review the data presented in the Study and consider reevaluating the allowance of such methods, particularly pipe bursting, which has been the cause of much regulatory confusion. (When proper procedures were followed in the pipe bursting demonstration, the environmental impact was negligible and the requirements of NESHAP were met.)
- EPA Administrator should approve an alternative (AAA) for pipe bursting, which would allow the use of pipe bursting on AC pipe but only when proper procedures are followed,
- Baseline soil samples should be collected prior to AC pipe bursting projects, which would allow for retrospective testing and future data comparisons, and
- In cases where additional oversight is required by regulatory agencies, air sampling should be conducted.