Driveway Sealant Threat to Watersheds

Industries hear city’s findings on pollution More data on parking lot sealants is needed, company representatives say.

Special Series: ‘Toxic Waters: An Austin treasure at risk’

By Stephen Scheibal


Tuesday, July 19, 2005

Austin officials who think they’ve found a new pollution problem presented it Monday to people who may prove part of the solution: representatives of companies making or applying chemical sealants that protect parking lots.

The city and the U.S. Geological Survey released a study last month tying parking lot sealants to a rise in pollution from polycyclic aromatic hydrocarbons, or PAHs, in urban waterways. PAHs in sufficient concentrations and exposure levels can threaten the health of humans or aquatic life, though officials say the contamination levels they’ve found probably will not make people sick.

Monday’s meeting, held in a small ballroom in the Lions Municipal Golf Course clubhouse, allowed the city to present the findings of the study and to collect reactions, and advice, from the industries that are closest to the chemicals.

Through the extremely technical discussions of statistical studies and chemical concentrations, the audience of about a dozen industry representatives warned that the study might not account for variations in products or parking lots, not to mention a range of PAH sources from motor oil to the wood smoke that flavors barbecue.

“There’s always more to the story,” said Bob DeMott, an environmental consultant studying the sealant findings for an industry group called the Pavement Coating Technology Center. “The beginning finding is only a beginning. The story is always more complicated in the end.”

Last month’s report blamed parking lot sealants for as much as 95 percent of the PAH pollution in urban watersheds.

City officials have said they might seek to ban some sealant products to protect the environment.

Austin officials have worried about pollution from parking lot sealants for years. When the American-Statesman published stories in 2003 about pollution in and around Barton Springs Pool, the city pointed to the sealants as a likely source.

High levels of PAHs also have been found in parts of Waller Creek through the University of Texas campus, the ponds in the Central Market area north of UT, and Walnut Creek in North Austin.

City officials were most concerned about sealants made from coal tar. The substance comes from a toxic byproduct of coke, a fuel that’s used in the production of steel. PAHs are primary components of coal tar sealants.

Such products are usually easy to find at home improvement stores, though the city has worked with sellers and contractors to stem their use.

But authors of last month’s report stopped short of narrowing the blame for PAH pollution, saying it isn’t clear that other types of sealants, including asphalt-based ones the city has recommended, are substantially better for the environment.

Peter Van Metre, who represented the U.S. Geological Survey at the meeting, closed his presentation by noting substantial increases of PAH levels in Town Lake as well as urban waters in Chicago and Virginia.

“This could be an important source that has not been looked into,” Van Metre said.

DeMott, in turn, rattled off a menu of information that he still wants to see about the study’s methods and findings.

“Right now,” he said, “there are a lot of details that are only available in city offices.”; 445-3819