Environmental Studies For Oilspill Trajectory Modeling In The Southeastern U.S. Outer Continental Shelf Leasing Area
Authors: Lanfear Kenneth J. , Amstutz David E. 
Published: October 2008

Abstract
Environmental studies and oilspill trajectory modeling are conducted as part of the Outer Continental Shelf Oil and Gas Program administered by the U.S. Department of the Interior. The modeling work and related studies are coordinated efforts of the U.S. Geological Survey and the U.S. Bureau of Land Management.
Oilspill trajectory modeling and physical oceanographic studies of areas off the southeastern coast of the United States have been in progress since 1976, and have been used in making decisions for two separate offshore lease sales. The initial oilspill trajectory model was modified to accommodate the findings of ongoing studies. Research carried out by investigators from government, universities, and the private sector has enlarged the data base and increased the understanding of oceanographic and meteorological processes observed in this region. Hypothesized ocean surface circulation patterns, originally based upon drift bottle returns, are now based upon a series of satellite observations, and will eventually be studied with three-dimensional time-dependent models. By correlating winds observed at data buoys with observed winds on land, correction factors have been developed to more accurately apply data from land-based meteorological stations for predicting winds on the ocean surface. As a consequence of this progress in understanding ocean circulation and surface winds, the oilspill trajectory analysis model for lease Sale 56 uses a data base substantially improved over that used for the earlier Sal e 43. Data from some trajectory models has been correlated with data on World War II tanker sinkings near Cape Hatteras, North Carolina.
The knowledge gained through this continuing program illustrates the value of coordinated, long-term studies to improve decisionmaking in the marine environment.

Introduction
The U.S. Bureau of Land Management (BLM) offshore studies program sponsors environmental research and investigations of the effects associated with the sale of oil and gas leases on the U.S. Outer Continental Shelf (OCS). Initiated in 1974, the program first sponsored regional studies by scientific disciplines, and then pursued specific research pertinent to decisionmaking, addressing such issues as space use conflicts, pollutant transport, and fates and effects of pollutants. In all of the offshore regions, the problem of oilspills has generated a high level of concern. Consequently, numerous studies have been done to identify the locations and sensitivities of the biologic and economic resources that could be harmed by oilspills as well as studies of those processes, such as winds and ocean circulation, that could transport spilled oil to vulnerable resources.
The U.S. Geological Survey (USGS) oilspill trajectory analysis (OSTA) model was developed in 1976 to bring together these various studies to aid in estimating possible environmental hazards associated with developing oil resources in OCS lease areas (1)(2). The OSTA model is a large, stochastic model which analyzes the probability of oilspill occurrence, as well as the likely movement of spills in relation to the locations of recreational and biological resources that may be vulnerable.
The probability of oilspill occurrence is estimated from information on the anticipated level of oil production and the possible modes of transport.