The oilspill risk analysis model of the U. S. Geological Survey

Abstract

The U.S. Geological Survey has developed an oilspill risk analysis model to aid in estimating the environmental hazards of developing oil resources in Outer Continental Shelf (OCS) lease areas. The large, computerized model analyzes the probability of spill occurrence, as well as the likely paths or trajectories of spills in relation to the locations of recreational and biological resources which may be vulnerable. The analytical methodology can easily incorporate estimates of weathering rates, slick dispersion, and possible mitigating effects of cleanup.The probability of spill occurrence is estimated from information on the anticipated level of oil production and method and route of transport. Spill movement is modeled in Monte Carlo fashion with a sample of 500 spills per season, each transported by monthly surface-current vectors and wind velocities sampled from 3-hour windtransition matrices. Transition matrices are based on historic wind records grouped in 41 wind velocity classes, and are constructed seasonally for up to six wind stations. Locations and monthly vulnerabilities of up to 31 categories of environmental resources are digitized within an 800,000 km2 study area. Model output includes tables of conditional impact probabilities (that is, the probability of hitting a resource, given that a spill has occurred), as well as probability distributions for oilspills occurring and contacting environmental resources within preselected vulnerability time horizons.The model provides the U.S. Department of the Interior with a method for realistically assessing oilspill risks associated with OCS development. To date, it has been used in oilspill risk assessments for eight OCS lease sales with the results reported in Federal environmental impact statements. A summary of results is presented herein. A "real time" version was also used to forecast the movement of oil from the 1976-77 Argo Merchant oilspill. Additional model runs are planned for future OCS lease sales in frontier areas. Other possible applications include analysis of OCS development alternatives and site selection for oilspill cleanup equipment.

Assessing oil spill risk in the Chinese Bohai Sea: A case study for both ship and platform related oil spills

“…An attempt of modeling has been suggested to estimate the spill potential specificities (Vethamony et al, 2007;Lamine and Xiong, 2013;El-Fadel et al, 2012). Among them, an initial development for the oil spill risk analysis model was in 1975 by the DOI (the Department of the Interior) of the federal government of the United State of America (USA) to assess possible oil spill impact from offshore oil operations (Smith et al, 1982). This model summarized the statistical results from a number of spills' trajectory simulations, which provided a table of probability of hitting environmental resources by hypothetical oil spills.…”

Estimating Potential Effects of Hypothetical Oil Spills on Polar Bears

“…Radio-telemetry data collected during September and October were converted into estimates of density within the area surrounding each simulation site. We used methods developed by NOAA (National Oceanic and Atmospheric Administration, National Ocean Service, Office of Response and Restoration 2005) and the U. S. Minerals Management Service (Smith et al 1982) to generate paths of hypothetical oil spills. The general strategy used in this study was to: 1) calculate the probabilistic distribution of polar bears in our study area, 2) map the "footprints" of a series of oil-spill scenarios originating from each location, and 3) use GIS layering to overlap the simulated oil-spill footprints with polar bear distributions to estimate the numbers of bears that would be exposed to oil in each scenario.…”

“…There previously has not been a way to determine how many bears, or other animals dispersed over the seascape, might be exposed to oil contamination. Models describing the movement and deterioration of oil in the environment have been developed and extensively tested (Smith et al 1982, National Academy of Sciences 1985, Galt et al 1996, French 2001. The life and health threats to animals exposed to oil also are well described, and much has been written about the toxicological effects of oil on birds and mammals (National Academy of Sciences 1985, Geraci andSt.…”

Proceedings of the Geologic and Hydrologic Hazards Training Program

“…The USGS has produced a model (Smith, et al, 1982) which assesses the risks to coastal resources of offshore drilling and petroleum transport.…”

“…The problem is then to maximize the total volume of production, V, where (Smith, et al, 1982). (b) Two sets of oil drilling tracts chosen to minimize environmental damage based on two sets of unit costs for resources (Smith, et al, 1979).…”