Updated cPAH Toxicity Values Reduce Cleanup Footprints & Costs at Portland Harbor Superfund Site

January 3, 2020


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Exponent Staff

On December 9, 2019, the U.S. Environmental Protection Agency (EPA) finalized revisions to the Portland Harbor Superfund Site cleanup plan, reducing the footprint requiring active cleanup for carcinogenic polycyclic aromatic hydrocarbons (cPAHs) and lowering overall cleanup costs. These revisions stem primarily from EPA's updated toxicity values for the cPAH benzo[a]pyrene (B[a]P), which were published in January 2017 and which may have important implications for other Superfund sites where cPAHs are driving cleanup costs.

Revisions to the Portland Harbor cleanup plan based on EPA's updated B[a]P toxicity values reduce the total nearshore active cleanup area by 17 acres, the capping area by 8 acres, the dredging volume by nearly 44,000 cubic yards, and the length of riverbanks to be remediated by 713 ft. While modest relative to the whole site, which stretches 10 miles and covers 2,200 acres, these reductions result in an estimated savings of $35.4 million on a project with cleanup costs estimated at over $1 billion.

How Exponent Can Help

Exponent scientists and engineers assist in the assessment and management of PAH-contaminated sediments, site investigation and remediation, ecological and environmental risk assessments, oil spill assessments, product stewardship, and environmental forensics for assessing the sources of PAHs in environmental media. Our expertise in environmental forensics, including chemical fate and transport, chemical fingerprinting, and historical release reconstruction, allows us to identify PAH sources, including background, and to estimate the extent and timing of releases and determine responsibilities for sites contaminated with PAHs. In particular, Exponent scientists are in the forefront of understanding the interactions of PAHs with sediments and soil and the oral and dermal bioavailability of PAHs to human and ecological receptors. In addition, Exponent has developed risk assessment approaches to account for differences in soil and sediment PAH bioavailability, including using passive samplers to measure the bioavailable fraction of PAHs.