An oilspill risk analysis for the western Gulf of Alaska (Kodiak Island) Outer Continental Shelf lease area

Slack, James Richard; Smith, Richard Allmon; Wyant, Timothy

doi:10.3133/ofr77212

Cited by 3 publications

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“…A further advantage of land segments is that they allow consideration of risks to targets which may not have been included in the model runs. For example, Rectangles are proposed lease tracts (Slack, et al, 1977).…”

Section: Land Segmentsmentioning

confidence: 99%

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

Smith¹,

Slack²,

Wyant³

et al. 1982

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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.

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Section: Land Segmentsmentioning

confidence: 99%

“…Map showing a sample target in the Western Gulf of Alaska. Hatched areas indicate foreign fishing areas.Rectangles are proposed lease tracts(Slack, et al, 1977).…”

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confidence: 99%

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

Smith¹,

Slack²,

Wyant³

et al. 1982

Professional Paper

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“…Many wildlife populations undergo migrations during the year, and seasonal reproductive activities are often more susceptible to damage from spilled oil than other parts of the life cycle, The economic impact of spilled oil on such targets as beaches may also differ seasonally. Slack, Smith, and Wyant, 1977) Salmon purse seining and set net areas Pink and chum salmon intertidal spawning areas Dungeness crab spawning, rearing, and catch areas Tanner crab fishing areas Tanner crab mating and hatching areas Tanner crab vital rearing The model accounts for seasonal vulnerability by associating with each target a vector specifying "home" or "away" for each month. When a simulated trajectory crosses a cell which the target matrix indicates may be occupied by a target, program SPILL checks to see if the target is home before registering a hit.…”

Section: Seasonal Vulnerabilitymentioning

confidence: 99%

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

Smith¹,

Slack²,

Wyant³

et al. 1980

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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, stick 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 km 2 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. .4 summary of results is presented herein. A '

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