Characterization and FATE of PAH-contaminated sediments at the Wyckoff/Eagle Harbor Superfund Site.

Eagle Harbor, a shallow marine embayment of Bainbridge Island, WA approximately 10 miles west of Seattle, WA), was formerly the site of the Wyckoff wood-treatment facility. The facility used large quantities of creosote in its wood-treating processes from the early 1900s to 1988. Historical creosote seepage into the harbor resulted in substantial accumulation of polycyclic aromatic hydrocarbon (PAH) contamination in the harbor sediments over time. This investigation focused on the distribution and fate of the PAH-contaminated harbor sediments. Analyses of 10 sediment cores using total petroleum hydrocarbon (TPH) fingerprinting, the distribution of 50 PAH analytes, and sediment age dating revealed the contributions of three distinct sources of PAHs to sediment contamination in the harbor during various periods over the past 100 years; namely, creosote, urban runoff, and natural background. Surface sediments (upper 20-30 cm) in the cores closestto the Wyckoff wood-treatment facility and southeast of an existing cap were dominated by urban runoff and weathered creosote; the deeper sediments (> 30 cm) were heavily contaminated with relatively unweathered creosote and some pure-phase creosote. Cores located the furthest from the area of contamination, in the center of the harbor, were dominated by urban runoff, showed no signs of creosote contamination, and had much lower PAH and TPH concentrations than those adjacent to the facility. In the four cores in the center of the Harbor, farthest from the former Wyckoff facility, PAH concentrations increased significantly (p < 0.01) with proximity to the northern shore of the harbor, which is more heavily developed than the southern shore and is where all automobile traffic enters and exits the island through the Bainbridge Island ferry terminal. Deeper portions of these cores were contaminated primarily with natural background PAHs, likely representing preurbanization sediments. Sedimentation rates ranged from 0.54 to 1.10 gm/ cm2 in the four cores located in the middle of the harbor, and for the single nearshore core that could be used to calculate sedimentation rates. Recognition that urban runoff has been a fairly consistent and ongoing source of PAHs to the harbor's sediments for the past 50-70 years may influence future sediment management decisions for this site with respect to long-term monitoring of surface sediments to assess cap performance. The results provided information on the ability of Eagle Harbor sediments to recover under natural conditions, identified the occurrence of creosote-derived PAH weathering in off-cap surface sediments, and distinguished between these distinct PAH sources in the harbor (creosote, urban runoff, and natural background).