**REPORT TITLE**: Final Technical Report - Outer Continental Shelf Oil
Spill Probability Assessment.

Vol. 1, Data Collection Report; Vol. 2, Data Analysis Report.

**STUDY TITLE**: Oil Spill Probability Projection.

CONTRACT NUMBER(S): BLM: CT0-69; MMS: 14-12-0001-29055.

SPONSORING OCS REGION: Washington.

APPLICABLE PLANNING AREA(S): All.

FISCAL YEAR(S) OF PROJECT FUNDING: 1980.

COMPLETION DATE OF REPORT: July 1982.

COST(S): FY 1980: \$193,348; CUMULATIVE PROJECT COST: \$193,348.

PROJECT MANAGER(S): Not available.

AFFILIATION: The Futures Group.

ADDRESS: 76 Eastern Boulevard, Glastonbury, Connecticut 06033.

PRINCIPAL INVESTIGATOR(S)\*: K. Bjorhus, R. Golob, R. King, D. McShea,
B. Murphy, W. Olender, G. Owen, J. Wright, R. Yamartino.

KEY WORDS: North Atlantic; Mid-Atlantic; South Atlantic; Straits of
Florida; Eastern Gulf; Central Gulf; Western Gulf; Southern California;
Central California; Northern California; Washington-Oregon; Gulf of
Alaska; Kodiak; Cook Inlet; Shumagin; Aleutian Arc; North Aleutian
Basin; St. George Basin; St. Matthew Hall; Bowers Basin; Aleutian Basin;
Navarin Basin; Norton Basin; Hope Basin; Chukchi Sea; Beaufort Sea;
socioeconomics; oil spill; platforms; pipeline; marine traffic; data;
data deficiencies; development; North Sea; Headquarters.

ACCESS NUMBER: 29055

**BACKGROUND**: The accidental release of oil or natural gas may occur
at several stages, including extraction, processing, and transport. In
order to project or predict the occurrence of accidents which result in
sizable releases of oil or gas, a review of accident history is
necessary. This report is a compilation, review, and analysis of data
pertaining to individual oil spill incidents, as provided by private
companies, research organizations, and government agencies around the
world.

**OBJECTIVES**: (1) To collect world-wide accident and exposure data for
tankers, platforms, pipelines, single point moorings, and marine
terminals for as long a period as possible; (2) To use these data to
examine the relationships between accident and exposure data; and (3) To
identify exposure variables that could be used to predict future number
and volumes of spills.

**DESCRIPTION**: In order to obtain world-wide accident and exposure
data for tankers, platforms, pipelines, single point moorings, and
marine terminals, several sources of information were used. Requests
were submitted to oil and gas (and associated) companies, port
facilities, research organizations, and various governments located
around the world. Volume 1 (Data Collection Report) was formatted in
order to discuss study objectives, the nature of data collected, the
varying methods used to collect data, individual data sources,
identifiable limitations in data collection, the data editing process,
and recommendations for future data collection procedures. Volume 2
(Data Analysis Report) described the analyses performed with the
compiled data base and concludes with several preliminary conclusions.

**SIGNIFICANT CONCLUSIONS**: Limitations in data collection were
experienced. Several data sources were recognized as voluntary rather
than mandatory, where data had been collected in the absence of
regulatory or administrative reporting requirements. In the absence of
certain conditions (e.g., mild penalties for spilling oil and government
confidentiality), the information collected which was based on voluntary
reporting was suspect. Information sources were not uniformly
distributed throughout the world. In particular, there was a paucity of
information noted from Communist countries, based on requests submitted.
More cooperation was received from companies or governments with
established or developed environmental concerns. However, to the extent
that spill data are indicative of environmental concern or pollution
prevention effectiveness, individual companies or governments had an
interest in including fewer spills in their data bases. Using similar
reasoning, it was noted the these entities also had a reduced interest
in ensuring a complete and accurate data base. Inconsistent and
arbitrary reporting of spill causes was noted as being a major source of
unreliable data.

**STUDY RESULTS**: For Gulf of Mexico platforms, exposure indices based
on a combination of current production levels and cumulative rig-years
of experience provided the best spill frequency and volume distributions
estimators. The period 1969-74 accounts for a vastly disproportionate
spill number relative to other years and suggests that exposure
variables involving rates of change in activity might be more
successful.

For ports (i.e., marine terminals), spill data from Millford Haven for
the period 1961-80 were examined. Only 4% of the volume spilled was
attributable to the port and individual spills were small. Spill numbers
over the period studied showed significant declines despite large
increases in ship calls and volumes handled. This suggests that adaptive
exposure indices which allow for risk reduction with added experience
may be better predictors of spill risk than estimators based solely on
present port activity level.

Single buoy mooring (SBM) data through 1971 (more recent data were
unavailable) provided by Shell Oil Company were analyzed. Ship calls was
preferred to volume handled as an exposure rate variable. Both loading
and unloading SBMs have a spill rate per ship call that is comparable to
fixed berth facilities, but spill rate per ship call is about three
times larger at unloading SBMs. Approximately one-third of all loading
SBM spills are larger than 9,000 gallons while less than 1% of unloading
SBM spills are this large.

An examination of Gulf of Mexico submarine pipeline data for the time
period 1969-80 indicated that pipeline length was a superior exposure
variable relative to volume throughput. Oil pipeline spill rates are an
order of magnitude larger than gas pipeline rates. This may reflect
pipeline age or the fact that gas lines are generally larger.

Tanker spills greater than 1,000 bbl in port and at sea for the years
1974-80 were studied in conjunction with four exposure variables: port
calls, volumes shipped, port call miles, and ton-miles. The hypothesis
that the exposure variable is not statistically related to spill
frequencies could not be rejected for all four variables. Therefore, a
strict statistical relationship between exposure variables and spill
frequencies cannot be proven. Spill rates for tons and ton-miles have
declined significantly since 1974.

A Poisson distribution may be used to predict future at sea spills if
world volumes or weights of crude oil delivered remains in a range
experienced in recent years. A limited North Sea port call analysis
indicated a spill rate twice comparable size as Gulf of Mexico rates.
However, this analysis used port call data only for the three years
(i.e., 1977 through 1980) during which there were a total of four spills
in the North Sea and seven spills in the Gulf of Mexico. Therefore, no
conclusions have been reached regarding expected high spill rates in the
North Sea or implications for subarctic Alaska. A preliminary volume
analysis concluded that exponential distribution was not a suitable
representation of data. Further work should be done to explore a number
of other options. Future work on tankers should focus on possible causes
of decline in spill rates with a view toward constructing a more complex
model that can adequately explain reasons for decline and will possess
predictive qualities.

**STUDY PRODUCT(S)**: The Futures Group and World Information Systems.
1982. Final Technical Report - Outer Continental Shelf Oil Spill
Probability Assessment. Vol. 1, Data Collection Report. A final report
for the U.S. Department of the Interior, Bureau of Land Management,
Washington, D.C.. Contract No. 14-12-0001-29055. iv + 69 pp.

Murphy, B., W. Olender, R. Yamartino, R. King, and J. Wright. 1982.
Final Technical Report - Outer Continental Shelf Oil Spill Probability
Assessment. Vol. 2, Data Analysis Report. A final report by The Futures
Group and Environmental Research & Technology, Inc. for the U.S.
Department of the Interior, Bureau of Land Management, Washington, D.C..
Contract No.

14-12-0001-29055. ix + 129 pp. + app.

\*P.I.\'s affiliation may be different than that listed for Project
Manager(s).