Report on PAHs in Sediments before RTS was banned in Austin, TX

Updating and repairing links in old posts brings to mind the saga of PCTC’s last decade.  For reasons not clear to PCTC, in the early 2000s certain employees of the City of Austin convinced themselves that refined coal tar-based pavement sealant (RTS) was causing a PAH problem in sediments in Austin water bodies. The City asked the Texas Commission on Environmental Quality (TCEQ), the Texas Department of Health (TDH), the US Agency for Toxic Substance and Disease Registry (ATSDR), and the US Environmental Protection Agency (EPA) Region 6 to evaluate PAHs in city sediments – all concluded that the City did not have a problem. Apparently, the opinions of these government agencies did not further the City’s agenda (it’s difficult not to conclude that the agenda all along was to find a reason to ban RTS for reasons known only to those involved) so the City reached out to the Austin office of the US Geological Survey (USGS) to confirm their preconceived notions. USGS personnel proceeded to design and publish a study confirming the City’s assertions by cherry picking data and ignoring all but supportive citations (this is a type of confirmation bias called advocacy research). The assertion made here of cherry picked data is neither conjecture nor inference – at the time of this writing (Sept. 2015) we have the data and emails demonstrating that the USGS scientists purposely selected data to support the City’s agenda (which the USGS quickly adopted as its own – but that’s a story for another day). But back in 2005, when the City of Austin and the USGS sandbagged local businesses and the sealcoating industry by rolling out the USGS’ advocacy research at the same time as proposing and implementing a ban on RTS, little was clear.

In an effort to shed light on the situation, in 2005, PCTC retained Environ, a well-respected environmental consulting firm, to evaluate the science underlying the USGS study, the claims being made by the USGS and the City of Austin, and the City’s RTS ban (which became effective Jan. 1, 2006). In November, 2005, Environ collected sediment samples from throughout the City of Austin to help inform their evaluation of the USGS and City claims. Results of Environ’s evaluation were summarized in a comment published in the journal Environomental Science & Technology in April, 2006, and presented in detail in a report to PCTC dated October, 2006. Among its conclusions, Environ found the USGS study to be, at best, incomplete.

When the chemical fingerprints of PAHs from differing sources were compared to the measurements made from sediment samples, the patterns demonstrated that the PAH profile in sediments is distinct from that associated with coal tar-derived pavement sealer products and parking lot residues. The lack of a coal tar-derived pavement sealer signature in actual stream sediments further calls into question whether the proposed hypothesis that Austin stream inputs are dominated by coal tar-derived pavement sealer will be substantiated and points out the limitations of making predictions about stream sediment based solely on filter residue washed off parking lots. The results of this survey, from the field observations of stream conditions to changing concentrations associated with storm events and the PAH fingerprint patterns, reinforce through multiple approaches that the dynamics properties of sediment deposition, transport and mixing operating in Austin streams make it necessary for evaluations of urban impacts to be based on comprehensive studies of streams themselves.

Environ’s 2006 comment and report constitute a post publication peer review of the USGS study, which was published as Mahler et al. (2005).  Appendices to Environ’s 2006 report are posted here. PCTC asked Environ to conduct a follow up study in 2008 to evaluate whether Austin’s ban had any impact on PAHs in the City’s sediment (it did not). Results of the before and after studies were published in a peer reviewed journal in DeMott and others (2010).

Citation: Environ (2006). Polycyclic Aromatic Hydrocarbon(PAH)Characteristics for Sediments Collected from Creeks and Streams in Austin, Texas. Report prepared for the Pavement Coatings Technology Center. 63 p.
Available at, plus Appendices available at



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