Effectiveness Monitoring for a Creosote-Piling Removal Project: Embryos of Pacific Herring (Clupea pallasii) as Sentinels for the Presence of Polycyclic Aromatic Hydrocarbons (PAHs)

This study was originally designed to evaluate the degree to which removal of creosote-treated pilings (CTPs) would remove the risk of exposure of biota to creosote related toxic chemicals in Puget Sound. To that end, WDNR contracted with WDFW staff from 2013 to 2015 to use monitoring tools used or developed by WDFW in their toxic monitoring program under the Puget Sound Ecosystem Monitoring Program (PSEMP) to evaluate the effectiveness of the CTP removal procedure in one of the several piling fields designated for removal in 2013. The piling field selected for the study, a derelict railroad trestle in Quilcene Bay, was ideal for the study in many ways, including its small size (which reduced the need for spatially extensive sampling), and its isolation from other (non-CTP) sources of chemical contamination that might otherwise have confounded interpretation of the putative CTP chemical source.

Pacific herring were selected as the indicator species for this study because they have historically used Quilcene Bay for spawning, including on eelgrass beds at the Quilcene CTP field, and developing fish embryos are known to be particularly susceptible to many of the chemicals known to occur in the creosote used to treat wood pilings. The pre-removal part of this study identified and described the contaminant risk faced by herring embryos spawned in close proximity to derelict, approximately 100-year-old CTPs. A suite of 42 individual chemicals in a class of polycyclic aromatic hydrocarbons (PAHs), which are typically abundant in creosote, were measured in embryos developing within two meters of derelict pilings. Mortality of embryos increased with increasing PAH levels, even though the PAH levels were relatively low compared with other published studies, suggesting that even old derelict pilings can pose a risk to embryos developing near them.

The original intent of the study was to compare PAHs in herring embryos in a CTP field prior to piling removal with embryos in the former CTP field area one year after pilings had been removed. However, this intent was never fulfilled because CTPs in Quilcene Bay were never fully removed according to the project plan and Best Management Practices; many CTPs within the study area were cut off at or above the seafloor and significant piling/wood debris was left behind, resulting in new and worse PAH conditions. PAH levels in 2014 embryos (2 weeks after removal activities) and 2015 embryos (one year later) were 17x greater than 2013 embryos prior to the removal.

The area affected by PAH contamination was small relative to the total area Pacific herring typically use for spawning in Quilcene Bay, and the actual area used by Quilcene herring in any given year is unpredictable. Hence, the risk to herring from CTP contamination in any given year is difficult to estimate. The unique circumstances that occurred at this site regarding the high percentage of pilings that broke and could not be fully extracted (resulting in the terms for the CTP removal contract not being fulfilled) will require additional study and cleanup efforts to reduce potential impacts to herring embryos.