Much of the water and wastewater industry’s pipe networks are nearing the end of their service life and require replacement. This trend is occurring at the same time that many baby boomers are retiring and municipal utility providers are facing major budget constraints.
Asbestos cement (AC) pipe comprises a significant portion of the water distribution systems in many North American utilities. It has been estimated that about 12 to 15 percent of water mains in the water distribution systems of the United States and Canada are AC pipes. In some utilities, as high as 85 percent of their water mains are AC pipes (Hu, et. al, 2013.) While it is difficult to accurately measure how much AC pipe remains in the ground and in what condition, there is an estimated 630,000 miles of AC pipe in the United States and Canada (Von Aspern, 2009). The rehabilitation of AC pipe needs to be addressed immediately.
Asbestos fibers were used in combination with cement to manufacture pipes over 100 years ago in Genoa, Italy. Between 1906 and 1913, a Genoa company combined asbestos fibers with cement to produce a reinforced pipe that could handle high pressures. It was first brought to North America in 1929 when the Johns-Manville Corporation installed an AC pipe manufacturing machine. AC pipe was a common choice for potable water main construction during the 1940s, 50s and 60s. The installation of AC pipe was curtailed in North America in the early 1980s due to health concerns associated with the AC manufacturing process (Hu, et. al, 2013). The U.S. Environmental Protection Agency (EPA) issued a complete ban on all asbestos-containing products in 1979. However, the U.S. Fifth Circuit Court of Appeals overturned the ban. The court did reinforce the EPA’s responsibility to regulate asbestos (Von Aspern, et. Al, 2012).
Initial standard
The first standard (US Federal Standard SS-P-531) in North America to regulate the manufacture of AC pipe was created in 1940. The America Water Works Association (AWWA) approved their first standard for AC pipe, C400-53T, in 1953. This standard covered AC pressure pipe in underground water service and covered materials of manufacture, pipe sizes and markings. AWWA’s standard also established criteria for burst, flexural and crushing strengths. In 1964, AWWA Standard C400-64 included silica as a constituent and described a test method for determining uncombined calcium hydroxide (free lime) content. The AWWA standard specified no limit on free lime in Type I AC pipe. The amount of free lime is constrained to no more than 1.0 percent in Type II pipe (AWWA C400/ASTM C296) (Hu, et. al, 2013).
In 1975, selection of the types of AC pipes for different working environments was incorporated into the AWWA Standard C401-75 (Hu, et. al, 2013). Unlike Type I AC pipes, silica was added to the mixture of asbestos fibers and Portland cement during the manufacturing of Type II AC pipes. Due to this difference, free lime in Type I and Type II AC pipe represents 15.5 percent and 0.4 percent of the total weight, respectively. As free lime content is a critical factor that affects AC pipe corrosion, the corrosion resistance of the two types of AC pipes is different. Therefore, information about the type of pipe installed is useful for predicting long-term performance of AC pipes (Hu, et. al, 2010). Smaller diameter pipes have a higher likelihood of pipe failure because they have lower moments of inertia and larger bending stresses. Conveyed water quality, aggressive soil conditions and movement, pipe diameter and pipe age are the biggest factors that correlate with pipe failure. The average breakage rate for AC pipe varied from 5.3 to 7.6 breaks/100 miles/year (Hu, et. al, 2013).
Communities that experienced significant growth during the 1940s through the 1960s constructed their buried pipeline infrastructure when the use of AC pipe was popular. These cities have percentages of AC pipe that are much higher than the national average. Under certain conditions, AC pipe has experienced failures at rates that are similar to other pipe types during their 50-year design lives. Many public agencies have reported significantly higher failure rates for AC pipe than for other pipe materials. Overall, however, studies have shown that the failure rate for AC pipe increases dramatically with age (Von Aspern, et. al, 2012).
In 2005, the United Kingdom published a study on rehabilitation methods for replacement of AC pipe through a series of studies entitled “Managing the risks presented by pipe burst, redundant and live asbestos cement water distribution pipes.” The UK study evaluated asbestos fiber release for decommissioning, open-cut removal and pipe bursting. Actual air samples were taken during open-cut removal and pipe bursting of the AC pipe. The UK report visited two demonstration sites for pipe bursting AC pipe: the Bankshill site and the Aldearn site.
For the Bankshill site, a total of eight ambient air-monitoring sites and four personal monitoring sites were set up. The demonstration project burst an existing 4-inch AC pipe with a replacement HDPE pipe. The highest limit measured for the background monitoring was 0.004 fibers per mL, which was well below the 0.01 respirable fibers per mL detection limit for asbestos fiber monitoring. For the Aldearn site, the highest limit measured for the background monitoring was 0.005 fibers per mL. While decommissioning provided the lowest fiber release scenario, the study noted that installation of a new water main alongside the old AC water main could potentially release fibers. Overall, the study recommended pipe bursting as a preferred alternative for AC water main rehabilitation (Conroy, et. Al, 2005).
WRF study
Technologies and methods available to rehabilitate or replace AC pipe are open-cut and removal of the existing pipe, cured-in-place pipe (CIPP) lining, sprayed-in-place pipe (SIPP) lining, pipe bursting and pipe reaming. The existing pipeline can also be decommissioned and replaced with a new water main installed in a different location. The Water Research Foundation has conducted WRF Project #4465 to study the environmental impact of AC pipe renewal technologies. During the study, demonstration studies of two rehabilitation technologies were 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 (Matthews, et. al, 2015):
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; and
The results from the water samples collected from each site showed that the renewal technologies had no negative impact on the water quality.
No negative environmental impacts were observed as a result of either pipe bursting or CIPP lining of AC pipe based on the results from the air, soil and water samples that were collected during the demonstration testing. It is recommended that regulatory agencies review these data presented and consider reevaluating the allowance of such methods, particularly pipe bursting. When proper procedures were followed, as were in the pipe bursting demonstration in Casselberry, FL, the environmental impact was negligible and the requirements of the National Emissions Standards for Hazardous Air Pollutants (NESHAP) were met (Matthews, et. al, 2015).
The Clean Air Act of 1970 dramatically increased the federal government’s role in air pollution control. The legislation authorized the development of comprehensive federal and state regulations to limit emissions. The U.S. Environmental Protection Agency (EPA) was created Dec. 2, 1970, in order to implement the various requirements included in massive environmental legislation (www.epa.gov.) NESHAP is a section of the Clean Air Act that governs hazardous air pollutants. The first three hazardous air pollutants adopted to the list of hazardous air pollutants were asbestos, beryllium and mercury. At the time of adoption, there were no methods available to test the ambient air or manufacturing process for asbestos particles. Regulation of asbestos was limited to visible particle emission (Ambler, 2014).
Since adoption of the Clean Air Act, methods have been developed to improve testing for asbestos fibers such as the National Institute for Occupational Safety and Health’ (NIOSH) 7400 and 7402 methods. These testing methods use phase contrast light microscopy and transmission electron microscopy to accurately measure the presence of asbestos fibers in air samples to a detection limit of 0.1 fibers per cubic centimeter of air or an asbestos fiber that is 5 micrometers long (NIOSH Manual of Analytical Methods, 1994). For size comparison, a human hair is approximately 90 micrometers in diameter.
An additional article will be presented in next month’s Underground Construction magazine that will focus on the largest successful asbestos cement pipe bursting project in North America and the specific steps required to explicitly meet NESHAP’s regulations for pipe bursting asbestos cement pipe.
ABOUT THE AUTHOR: Alan Ambler, P.E., LEED AP, is the Water Resources Manager for the city of Casselberry, FL. Ambler has 15 years of diversified experience in utility management and design, roadway and drainage design, utility coordination and construction management. His career efforts have brought him from Dubai to Alaska to manage infrastructure development for large scale developments such as Dubai Maritime City and the World Islands in Dubai to the city of Ketchikan’s onsite construction inspection representative for two $30 million+ cruise ship berth projects in Alaska. Ambler now manages the utility department consisting of 39 employees for the city of Casselberry, including day to day operations and planning, design and execution of the $6 million per year capital improvement plan.
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Asbestos testing will be conducted to determine the extent of the asbestos contamination.
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The asbestos pipes will be disposed of in a safe and environmentally responsible manner.
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Here are some additional tips for safely disposing of asbestos pipes:
Do not attempt to remove asbestos pipes yourself. This is a dangerous task that should only be performed by trained professionals.
Contact a licensed asbestos removal and disposal company to get a free estimate.
Make sure the company you hire is EPA and DTSC certified.
Be sure to ask about the disposal methods that will be used.
Follow the instructions of the asbestos removal and disposal company carefully.
By following these tips, you can help to ensure that your asbestos pipes are disposed of safely and responsibly.