Launch Slideshow

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End of the Line

End of the Line

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    It's not illegal to install new asbestos-cement pipe — just impractical. Photos: TT Technologies

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    The bladed cutter head of a static pipe-bursting machine enters the host pipe at McGuire Air Force Base in New Jersey. More than 8,250 linear feet of 3- through 12-inch asbestos-cement water main was replaced with HDPE. The project was specified as trenchless pipe bursting so the pipe could be replaced without removing it from the ground. The Water Research Foundation is seeking agencies for pilot studies of less than 260 linear feet to help develop a “consolidating mud” that can serve as a lubricant and that conglomerates the soil, mud, and broken fragments into a single material; this mud could make fragments left behind more acceptable because they'd be less likely to be disturbed during subsequent excavation. Contact Jian Zhang at 800-666-0206.

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    Hot spots

For nearly a century, asbestos-containing products have been an important part of American society as thousands of products — from roofing materials and insulation to tape wraps and pipe — were chosen for their strength, low unit weight, and resistance to heat and corrosion.

Hundreds of thousands of miles of the pipe remain in service. Since much of it's nearing the end of its design life, it's the proverbial elephant in the room that must be dealt with but seems easier to ignore.

Originally marketed as a strong, lightweight, non-corrosive alternative to cast iron and steel, asbestos-cement pipe offered superior flow properties due to its smooth interior walls, exceptional corrosion resistance from the asbestos fibers matrix, and simplified construction due to the low unit weight. By the mid-1940s, four major companies were manufacturing the pipe at more than a dozen U.S. plants.

From the 1940s through the late 1970s, the pipe became the predominant choice for water transmission and distribution systems, storm drains, and sanitary sewer force mains. Vitrified clay remained the more popular choice for gravity sewers, and reinforced concrete was typically used for sewer interceptors.

The pipe's performance, however, has varied. Failure rates are higher than other materials when surrounding soils are acidic or high in sulphates, magnesium salts, or alkaline hydroxides. Performance also suffers when the water supply contains ammonia or is classified as “soft water.” In clay soils, the failure rate increases during the summer when the groundwater level reaches the pipe. Absent other factors, rates increase linearly with age.

In 1973 the National Emissions Standards for Hazardous Air Pollutants (NESHAP) was created by the EPA under the Clean Air Act in response to studies that found that asbestos was a leading contributor to asbestosis and certain forms of cancer. Through NESHAP, the EPA sought to protect the public by controlling exposure to asbestos found in more than 3,000 products.

Regulating so many diverse products proved to be daunting, so in 1979 the EPA announced its intent to ban all materials containing asbestos. A decade later, the Asbestos Ban and Phaseout Rule proposed eliminating all asbestos-containing materials in three stages between 1990 and 1997.

When a large manufacturer sued to block the ban, the 5th U.S. Circuit Court of Appeals ruled that EPA had failed to present a compelling case. It did, however, reinforce the agency's responsibility to regulate the material, and asbestos was banned from new products.

After 1973, asbestos fiber content in pipe was reduced from 15% to 20% down to less than 0.2%. By the 1980s its popularity had waned dramatically due to fears of liability and market conditions, especially the availability of PVC pipe. Manufacturers stopped producing the pipe in the United States, but it is still produced in other countries.

MASSIVE UNDERTAKING

In 2002, an American Water Works Association survey of 337 large utilities serving nearly 60 million customers found that 15.2% — more than 30,000 miles — of distribution systems were composed of asbestos-cement pipe. An informal survey using public information sources on the Internet reveals that much of it is installed in the West (see table).

Substantial portions have been in use for 40 to 60 years — its typical life expectancy. With an estimated 630,000 miles of the pipe in the United States and Canada, a tremendous amount will need attention in the near future.

But replacement won't be easy.

The key to regulation centers is on the word “friable,” which the EPA defines as any material containing more than 1% asbestos that, when dry, can be crumbled, pulverized, or reduced to powder by hand pressure. According to the agency, activities such as cutting, grinding, or crushing render the pipe friable.