Project highlights Client challenge: The Washington State Department of Transportation (WSDOT) built a public roadway near a legacy industrial property. The construction included a subgrade drainage system, connected to the stormwater sewer system that discharged into the head of the Thea Foss Waterway. In subsequent years, elevated levels of polycyclic aromatic hydrocarbons (PAHs) – chemicals found in petroleum, coal tar, creosote, and soot – were detected in the waterway, resulting in a Superfund remediation that cost the responsible parties more than $100 million. Citing the new roadway drainage system as a primary transport pathway for coal tar and PAHs from the former industrial site into the head of the waterway, some of the responsible parties and the U.S. Environmental Protection A

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