MMS ENVIRONMENTAL STUDIES PROGRAM: ONGOING STUDIES
MMS OCS Region: Alaska
Title: Oil Spill Occurrence Estimators for the Beaufort/Chukchi Sea OCS: Statistical and Fault Tree Approaches (AK-00-02A)
Total Cost: $198,000 Period of Performance: FY 2000-2002
Conducting Organization: Ted Eschenbach, P. E. and Bercha International Inc.
MMS Contact:

Chief, Alaska Environmental Studies Section
Description:
Background
The U.S. Outer Continental Shelf (OCS) historical platform and pipeline crude oil spills are mostly from the Gulf of Mexico and Pacific OCS. This spill record does not include pipeline spills inshore of the OCS, in State waters or on land. The MMS Alaska OCS Region intends to calculate spill occurrence based on Regional considerations, such as Alaska North Slope and Arctic Canada rather than on the Gulf of Mexico and Pacific OCS experience, and to include all major pipeline spills, both onshore and offshore, in an environmental impact assessment. The first step in this process was a study (OCS Study MMS 2000-007) in FY 1999-2000 to collate available information on crude and diesel spills of at least 100 bbl from the oil industry in the Alaska North Slope and Arctic Canada, verify spill information for spills of at least 500 bbl, and to estimate provisional occurrence rates for use in the nearshore Beaufort Sea OCS. Based on this prior study, MMS was able to extrapolate pipeline and facility occurrence rates for spills of at least 500 bbl from onshore oil spill experience to shallow coastal waters in the nearshore Beaufort Sea. The MMS found too few spills of at least 1,000 bbl to directly calculate occurrence rates for this size category.
The MMS Technology and Assessment (TAR) Program is approaching pipeline spill risk from an engineering view with ongoing studies for nearshore Arctic pipelines and Gulf of Mexico. Nonproprietary products from these studies will be made available to this study as they become available.
Objectives
The objectives of this study are to:
  1. Apply statistical procedures to develop occurrence rates for oil spills of at least 1,000 bbl from historical crude and diesel spills compiled for the Alaska North Slope and the Trans-Alaska Pipeline from Prudhoe to Valdez, excluding the marine terminal.
  2. Evaluate the applicability of results from objective (1) to offshore lease tracts where water depths make gravel islands unlikely or infeasible.
  3. Describe alternative approaches to estimating oil spill occurrence for Beaufort Sea and Chukchi Sea lease sales and development projects from spills of at least 1,000 bbl.
  4. Develop appropriate occurrence estimators, choosing the best method from objective (3).
  5. Provide professional support to MMS in regard to statistical issues of occurrence rates and estimator(s) related to this study and its results.
Methods
  1. The spill data from the preliminary study and environmental exposure issues for the <200-m deep portion of Beaufort Sea Planning Area will be reviewed. The relevance of the spill data to areas in waters deeper than 20 m will be evaluated.
  2. There are alternate approaches that can used to estimate spill rates in the absence of sufficient historical data. Alternative oil-spill frequency estimators suitable for predictive use in Beaufort and Chukchi Sea OCS will be evaluated, both in exploration and development phases. Draft oil spill rates based on the most appropriate estimators will be provided. The study will also quantify robustness of the statistics (Confidence Limits on spill frequency estimates), and quantify precision/variance of estimates of spill probabilities.
  3. Forty hours of on-call statistical/professional support to MMS staff regarding use of the results of (2) will be provided.
Importance to MMS
The Oil-Spill-Risk Analysis (OSRA) is a cornerstone to regional EIS’s, environmental assessments, and oil-spill-contingency planning. Oil-spill issues constitute a significant portion of public comments submitted on sale or development EIS’s in the Alaska OCS Region.
Current Status:
The two groups are analyzing Gulf of Mexico oil spill, pipeline, and platform data and developing oil development scenarios for Beaufort and Chukchi Sea. The draft Bercha report is currently being reviewed by MMS, and data from the report are being used to develop oil spill occurrence rates for the Beaufort Sea sales on the proposed 5-year leasing plan.
Final Report Due: May 2002 (Bercha), June 2002 (Eschenbach)
Publications: Bercha, F. G. 2001. Alternative Oil Spill Indicators for the Beaufort Sea and Chukchi Sea OCS - Fault Tree Approach. In Alaska OCS Region Eighth Information Transfer Meeting Proceedings, Preparer MBC Applied Environmental Sciences Anchorage: USDOI, MMS, Alaska OCS Region.

Eschenbach, T. 2001. Initial Work on a Statistical Approach to Oil Spill Occurrence Estimates for the Beaufort/Chukchi Sea OCS. In Alaska OCS Region Eighth Information Transfer Meeting Proceedings, Preparer MBC Applied Environmental Sciences. Anchorage: USDOI, MMS, Alaska OCS Region.
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Revised date: March 2002
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