An Evaluation of the Efficacy of Remedial Actions Implemented in the Commencement Bay Nearshore and Tideflats Superfund Site to Reduce PCB Contamination: 1984-2019 - Final Report

The Washington Department of Fish and Wildlife (WDFW) conducted a field study in 2019 in the Commencement Bay Nearshore and Tideflats (CB/NT) Superfund site to evaluate whether polychlorinated biphenyls (PCBs) in English sole (Parophrys vetulus), a bottomfish, have declined sufficiently since 1984 to achieve EPA’s target tissue cleanup objective for human health. This was determined by comparing PCBs in English sole sampled from 15 locations in Operable Unit 1 of the CB/NT Superfund site with English sole from Carr Inlet, a nearby reference location in the southern Puget Sound basin containing no known or suspected local PCB sources.

Two analytical methods for measuring PCBs and calculating their totals provided largely congruent results. Total PCBs measured using Aroclor-methods were required by the Record of Decision, however paired PCB-congener analysis methods on sample splits provided more clarity and certainty regarding the distribution of PCBs throughout the CB/NT. Congener-PCBs also allowed the opportunity to compare CB/NT English sole PCB results with other areas and species in Puget Sound. Results for both methods are compared and reported herein.

Although the overall CB/NT recovery goal was met (the average site-wide PCB concentration from all English sole in the 15 sampling locations of Operable Unit 1 was statistically indistinguishable from the Carr Inlet Reference Area (CIRA)), substantial areas of contamination in the CB/NT remained. English sole from two of the largest CB/NT waterways, Hylebos and Thea Foss, exhibited significantly greater PCB tissue concentrations than the CIRA, at concentrations among the highest PCB levels measured in English sole on a Puget Sound-wide scale (based on a comparison with English sole from WDFW’s long-term Toxics Biological Observation System, or TBiOS). Moreover, long-term TBiOS monitoring of PCB levels in English sole from the Thea Foss Waterway has shown no evidence of a declining PCB trend over the past 30 years.

The status of Blair Waterway is less clear. Although the average PCB concentration in English sole from Blair was statistically indistinguishable from the CIRA fish, sole from the head of the Blair Waterway exhibited one of the two highest PCB concentrations in the entire study, and 44% of the samples taken from the head of the Blair were above the average CIRA concentration. These observations suggest English sole continue to accumulate PCBs in the Blair Waterway, particularly from its head, at concentrations that can greatly exceed the recovery goal. More sampling in the Blair Waterway may be necessary to solidify its status.

Continued contamination of the CB/NT area, especially Hylebos and Thea Foss Waterways has also been reported in other fish species reported by WDFW’s TBiOS. Relatively high PCB concentrations in fish tissues have been observed in the Hylebos Waterway over six years from 2013 to the current study (2019) in juvenile Chinook salmon (Oncorhynchus tshawytscha), cutthroat trout (O. clarkii clarkii), and transplanted bay mussels (Mytilus trossulus). PCBs in cutthroat trout from the Hylebos exhibited the highest concentration of PCBs in any whole-body fish sampled by TBiOS over the past 30 years throughout Puget Sound, and the area surrounding the CB/NT industrial waterways has been reported as one of the most PCB-contaminated nearshore habitats for outmigrating juvenile Chinook salmon among twelve major Puget Sound rivers in recent years. Some PCB concentrations in both juvenile Chinook salmon and cutthroat trout from CB/NT locations were at levels reportedly high enough to impair their health or result in their mortality.

Continued contamination in fish from the Hylebos, Thea Foss and Blair Waterways is significant not only because of the risk to humans from consuming seafood from the CB/NT, but also because these waterways occupy a large area of productive nearshore and shoreline habitats in the CB/NT used by many important species including juvenile salmon. Considering the four waterways that have not been filled-in¹, only Sitcum Waterway, the smallest in area of the four, had English sole which unambiguously met the human health recovery objective. Chinook salmon juveniles, a species listed as threatened under the US federal Endangered Species Act, regularly migrate through and feed in these habitats during their normal seaward migration from Puget Sound rivers (most likely the Puyallup and Rivers for salmon sampled from the CB/NT site), highlighting concern for contamination in the CB/NT beyond the human health objective.

PCB concentrations in fish have declined sufficiently in Sitcum Waterway, the nearshore area fronting the mostly in-filled St. Paul, Milwaukee, and Middle Waterway, and the three areas along the western shoreline of Commencement Bay (Old Town, Ruston, and Pt. Defiance) to meet the CB/NT human health recovery objective. One fish from the Pt. Defiance location exhibited a relatively high total Aroclor concentration (67 ng/g wet wt). However, its total PCB concentration measured using the PCB congener method was less than half that, at 30 ng/g wet weight, so the PCB result from sample could reasonably be considered to have a high degree of uncertainty, and so be discounted.

Finally, in a comparison of WDFW’s 13 TBiOS English sole monitoring stations throughout Puget Sound, English sole from the CIRA were statistically indistinguishable from two TBiOS stations that could be considered to represent background PCB conditions in the primary (central and southern) basins of Puget Sound. The Port Madison, Anderson Island, and CIRA locations are all situated either in the main/central or southern basins of Puget Sound, and so are highly influenced by its human development, yet they are far removed from any known PCB hot spots such as Superfund sites. Hence, PCB concentrations in fish from these locations could reasonably be considered to represent background PCB levels for these Puget Sound basins, and they support the selection of CIRA as a suitable representative for that condition. The average TPCB concentration in English sole from these three background locations (12.8 ng/g wet weight) was slightly higher than the PCB recovery target (8 ng/g wet weight) adopted by the Puget Sound Partnership Vital Signs for Puget Sound Recovery. This disparity highlights Washington State’s aim to reduce PCBs throughout Puget Sound, to a level lower than its current background, to protect subsistence consumers.

¹ St. Paul and Milwaukee Waterways were filled in as part of the CB/NT remedial plan, whereas Middle Waterway appears to have been largely filled in from natural processes in the period from 1984 to 2019.