
An oilspill risk analysis was conducted for the midAtlantic (proposed sale 76) Outer Continental Shelf (OCS) lease area. The analysis considered: the probability of spill occurrences based on historical trends; likely movement of oil slicks based on a climatological model; and locations of environmental resources which could be vulnerable to spilled oil. The times between spill occurrence and contact with resources were estimated to aid analysts in estimating slick characteristics. Critical assumptions made for this particular analysis were (1) that oil exists in the lease area, and (2) that 0.879 billion barrels of oil will be found and produced from tracts sold in sale 76. On the basis of this resource estimate,...


The oilspill trajectory movement algorithm consists of a vector sum of the surface drift component due to wind and the surface current component. In the U.S. Geological Survey oilspill trajectory analysis model, the surface drift component is assumed to be 3.5% of the wind speed and is rotated 20 degrees clockwise to account for Coriolis effects in the Northern Hemisphere. Field and laboratory data suggest, however, that the deflection angle of the surface drift current can be highly variable. An empirical formula, based on field observations and theoretical arguments relating wind speed to deflection angle, was used to calculate a new deflection angle at each time step in the model. Comparisons of oilspill contact...

If an oilspill contacts a colony of glaucouswinged gulls Larus hyperboreus, reducing the population by 50%, the population is expected to recover to its prespill level in c.20 yr. For common murres Uria aalge, this same situation yields a recovery time of c.70 yr. Assuming that oil is found in the study area, and based on the expected number of oilspills to occur and contact these colonies during the lease lifetime, and assuming that each oilspill contact causes a fractional population loss of 0.95, the probability of reducing the population to some fraction of its initial level was calculated. For gulls, only a 10% change of population reduction to less than onehalf the prespill level was calculated for the...

An oilspill risk analysis was conducted for the South Atlantic (proposed sale 78) Outer Continental Shelf (OCS) lease area. The analysis considered the probability of spill occurrences based on historical trends; likely movement of oil slicks based on a climatological model ; and locations of environmental resources which could be vulnerable to spilled oil. The times between spill occurrence and contact with resources were estimated to aid analysts in estimating slick characteristics. Critical assumptions made for this particular analysis were: (1) that oil exists in the lease area, (2) that either 0.228 billion (mean case) or 1.14 billion (high case) barrels of oil will be found and produced from tracts sold in...

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