USGS backs off coal tar sealer claims

Following a challenge from a coalition of sealer producers, the U.S. Geological Survey has acknowledged it will revise some of results released concerning refined coal tar sealer and that errors were made in calculations relating to coal tar sealers and pavement runoff in a study the USGS conducted for the City of Austin, TX.

According to Bob DeMott an environmental consultant for Environ International, which was hired by the coalition to assist in its challenge to the USGS study, the USGS sent a letter to the coalition saying it will revise the report.

"The letter acknowledged some numerical inaccuracies and some details that were omitted from the report," DeMott said. "The letter stated the USGS would revise the report accordingly."

Forcing the USGS to reconsider some of the conclusions it drew is important, but DeMott says what's more important is the chain reaction that re-evaluation could cause.

"The USGS study was the basis for separate analyses that went into a scientific journal article that concluded coal tar-based pavement sealer was the predominant source of combustion byproducts [PAHs] in Austin. This, in turn, was used by the city of Austin in its decision to ban coal tar sealer," DeMott said.

The journal article relied on results presented in the USGS report in preparing a mathematical analysis of pavement sealer's impact on the environment.

"It would seem that the journal article analysis would have to be redone," DeMott said. "Austin might reconsider the more accurate information ultimately, but the first step is the revised USGS report."

DeMott said the coalition of sealer producers challenged the USGS study through a specific administrative process under the Federal Data Quality Act.

"This was the first successful challenge to USGS under the Act," DeMott said.

At press time the USGS had not announced when it will issue the report revision.