TA6 Applications of Ecotoxicology to Real World Problems
Room 18A/B, Level 4
8:00 AM - 12:00 PM, Tuesday, 11 November 2003
Chair: Williams, Bill ,
(213) Assessment of current and future ecological risk associated with a buried hydrocarbon plume.
Saban, L1, McGroddy, S1, 1 Windward Environmental, Seattle, WA, USA
ABSTRACT- An ecological risk assessment (ERA) was conducted for a plume of weathered hydrocarbons located in Avila Beach, San Luis Obispo, CA. The plume is buried 4-8 ft beneath the sediment/seawater interface and is located in the deeper intertidal and shallow subtidal sediments. The beach is a dynamic physical environment that is susceptible to disruption due to storm events. Therefore, in addition to the assessment of current risk associated with the presence of the buried hydrocarbon plume, an assessment of potential future risk was conducted by integrating models of the important chemical, biological and physical processes in this dynamic beach environment. The current scenario evaluates the potential for risk with the majority of the plume buried 4-8 ft below the sediment/water interface. The future scenario evaluates the potential for risk under two circumstances. The first is a storm or series of storms that partially erodes away the clean sand that covers the majority of the hydrocarbon plume. The second is a storm that completely mobilizes the hydrocarbon plume. To assess current exposure scenarios, site-specific exposure data were collected and evaluated. To assess risk associated with future storm events, physical transport models were developed to predict the erosion of the beach under a range of storm conditions and laboratory resuspension experiments were conducted in order to estimate the potential water column loading associated with the resuspension of the plume material. The results of these analyses indicate that there appears to be relatively isolated areas of potential impact to aquatic organisms due to exposure to the hydrocarbon plume under current conditions. The first storm scenario with partial erosion of the beach resulted in potential short-term risk in limited areas where the plume came within a foot of the sediment surface. The second storm scenario with complete mobilization of the plume appeared to present little risk associated with the release of chemical contaminants associated with the plume. However, the physical devastation of the habitat associated with a storm of this magnitude would result in significant ecological impacts.
Key words: sediment, ecorisk, hydrocarbons, net environmental benefit