PARENT SESSION
MP7 - Integration of Risk Assessment & Economics in Risk Management
Chair: Toll, John1, 1 Parametrix, Inc., Kirkland, WA
Co-chair: DeForest, David2, 2 Parametrix, Inc., Bothell, WA
2:10 PM to 5:30 PM - Monday, 18 November 2002
Room Ballroom A
(305) Probabilistic Bio-economic Modeling of Oil Spill Impacts in San Francisco Bay.
French McCay, Deborah*,1, Jennings, Jill1, Whittier, Nicole1, 1 Applied Science Associates, Narragansett, RI, USA
ABSTRACT- The objective of this study was to estimate potential bio-economic impacts (biological impacts and natural resource damage (NRD) costs) of oil spills resulting from groundings on rock pinnacles in the vessel traffic lanes of San Francisco Bay, as part of a cost-benefit analysis for potentially removing the rocks to reduce spill and ecological risks. Oil fates and effects were modeled for three spill sizes (20th, 50th, and 95th percentile volumes based on probability distributions of spill volume) from tankers and larger freight vessels and four oil types (gasoline, diesel, heavy fuel oil, and crude oil). The scenarios were run in stochastic mode, randomly sampling potential weather and current conditions, to determine the probability distribution of fates, impacts, and NRD costs. The results show that the diesel and crude oil spills would cause higher impacts in the water column than the heavy fuel and gasoline, because of the much higher volatility and lower toxicity of gasoline and because the heavy fuel oil spill volumes were smaller. However, the majority of the impacts and resulting NRD costs were for birds, with the water column losses relatively low because of the high dilution potential in the bay. The results are to be used by the Army Corps of Engineers San Francisco District in a cost-benefit analysis evaluating the trade-off of oil spill risk versus removal of the rocks. This work is significant as it demonstrates a statistically quantifiable method for estimating potential impacts that may be used in ecological risk assessment and cost-benefit analyses. The statistically-defined spill volumes and consequences provide an objective measure of the magnitude, range and variability of impacts to wildlife, aquatic organisms and shorelines for potential spills of four oil/fuel types shipped in the bay, each having distinct environmental fates and effects.
Key words: probabilistic risk assessment, ecological risk assessment, oil spills, fate and effects modeling