ABSTRACT 



The Outer Continental Shelf (OCS) Lands Act, as amended, requires the 

 Secretary of the Interior to make publicly owned oil and gas resources available 

 to help meet our Nation's energy needs. Within the Department of the Interior, 

 the Bureau of Land Management (BLM) carries out the leasing process; the Minerals 

 Management Service supervises leases once they have been sold (until early 1982 

 this function was performed by USGS). Since OCS leasing involves actions which 

 may impact the environment, the leasing process is subject to the National 

 Environmental Policy Act (NEPA) . NEPA in turn requires that BLM produce environ- 

 mental statements (ES) for each scheduled lease sale. A significant portion 

 of each ES deals with accidental spills related to production and transportation 

 of offshore oil. 



Oil spill risk analysis modeling is performed in DOI jointly by BLM and 

 USGS. Input data are provided by BLM; the modeling work itself is performed 

 and formally reported by USGS; and the model results are used by BLM. The 

 modeling work is undertaken from a cumulative perspective and includes spill 

 simulations from existing transportation routes and, where applicable, from 

 existing Federal leases. 



Model results are analyzed for use by decisionmakers on matters relating 

 to lease tract deletion and transportation alternatives and lease stipulations. 



The modeling work is predictive (for the next two to three decades) and 

 couched in probabilistic terms, to account for the numerous uncertainties 

 existing at the prelease sale stage. Thus, the model is unlike deterministic 

 or real time models. 



INTRODUCTION 

 1. Background 



The Outer Continental Shelf Lands Act of 1953 charges the Department of the 

 Interior (DOI) with carrying out a national offshore oil and gas leasing program. 

 Within the DOI, the Bureau of Land Management (BLM) is responsible for leasing 

 offshore resources and the Minerals Management Service is responsible for 

 supervising offshore leases. (Lease supervision and enforcement activities were 

 transferred from the U.S. Geological Survey (USGS) to the Minerals Management 

 Service in early 1982.) 



Since its first offshore lease sale in 1954, BLM has sold more than 4,000 

 leases for a total in bonus bids of $36 billion; lease rental and production 

 royalties have exceeded $10 billion (BLM 1981). Through 1980 a total of 5.4 

 billion barrels of crude oil has been produced (USGS 1980). 



The Outer Continental Shelf (OCS) program is carried out in compliance with 

 numerous laws. A compilation of laws governing resources and resource management 

 on the OCS is presented in DOI (1981). The National Environmental Policy Act 

 of 1969 and the OCS Lands Acts Amendments of 1978 provide for the environmental 

 modeling work reported on in this paper. 



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