Environmental resources-8 Estimated quantity of oil resources-11 Probability of oil spills occurring-12 Oil spill trajectory simulations-17 Combined analysis of oil spill occurrence and oil spill trajectory simulations-19 Discussion of results-38 Conclusions-~-55 References cited-56
Probability of oilspills occurring 11 Oil spill trajectory simulations 25 Combined analysis of oil spill occurrence and oil spill trajectory simulations 38 Discussion of results 56 Conclusions 58 References cited 60
An oil spill risk'analysis was conducted to determine the relative environmental hazards of developing oil in different regions of the Southern California (Proposed Sale 68) Outer Continental Shelf (OCS) lease area. The probability of spill occurrences, likely movement of oil slicks, and locations of resources vulnerable to spilled oil were analyzed. The times between spill occurrence and contact with various resources were also estimated. The combined results yielded estimates of the overall risks associated with development of the proposed lease area. Assuming that oil will be found in all three major subareas of the lease area, and depending upon the routes chosen to transport oil from OCS platforms to the shore, the leasing of the tracts proposed for OCS Sale 68 will result in an expected 1.1 to 1.2 oilspills (of 1,000 barrels or larger). The estimated probability that land will be contacted by one or more oilspills (of 1,000 barrels or larger) that have been at sea less than 30 days is 0.55 to 0.60, depending on the proposed transportation method chosen. If existing transportation of oil in the area is considered, these same probabilities increase to more than 0.99. Beac i Figure 1.-Map showing the Southern California OCS Lease Sale 68 study area and the proposed tracts.. . are also shown.
10,000 barrels in size. Nakassis (1982) conducted a statistical analysis of the record, 1964-1979, and concluded that the platform spill rate did not remain constant since 1964, but had decreased significantly. Using this trend analysis and updating for the 1980 data, the spill rate for platform spills of 1,000 barrels or larger is 1.0 spills per billion barrels produced; and the spill rate for platform spills of 10,000 barrels or larger is 0.44 spills per bill ion barrels produced. As with platform spills, the spill rate for pipelines is based on the record for the U.S. OCS from 1964 through 1980. Two spills of 10,000 barrels or larger are in the data base, along with 6 spills of 1,000 to 10,000 barrels in size. No trend in the pipeline spill rate is evident. The spill rate for pipeline spills of 1,000 barrels or larger is 1.6 spills per billion barrels transported, and the rate for spills of 10,000 barrels or larger is 0.67 spills per billion barrels transported. For tanker spill rates, previous OSTA models for Alaska used data for years prior to 1973. Using a new data base (The Futures Group, and World Information Systems, 1982) covering the years 1974 through 1980, Lanfear and Amstutz (1983) concluded that the tanker spill rate (expressed as spills per billion barrels transported) since 1974 was only about a third of that found prior to 1973. Thus, this oilspill analysis uses a significantly lower tanker spill rate than the earlier models. From 1974 through 1980, the data base contains records of 57 tanker spills of crude oil of 10,000 barrels or larger and another 57 spills of 1,000 to 10,000 .barrels. During this period, approximately 88 billion barrels of oil were transported. Lanfear and Amstutz (1983) were able to separate the 114 tanker spills into those occurring in port (i.e., inland of the breakwater, etc.) and those occurring at sea. While this information does not affect predictions of the overall occurrence rate, it does affect assumptions about where spills are likely to occur, and the appropriate weights were assigned along tanker routes to account for "at sea H/ Hin port" spills. The overall spill rate for tanker spills of 1,000 barrels, or larger, is 1.3 spills per billion barrels transported (0.90 at sea, and 0.40 in port), and the rate for spills of 10,000 barrels, or larger, is 0.65 spills per billion barrels (0.50 at sea, and 0.15 in port). In summary, the spill rates, expressed as number of spills per billion barrels produced or transported, used in this report are: >1,000 bbl ^10,000 bbl Platforms 1.0 0.44 Pipelines 1.6 0.67 Tankers (at sea) 0.9 0.50 Tankers (in port) 0.4 0.15 Oil spill occurrence estimates for spills greater than 1,000 barrels and greater than 10,000 barrels (Table 1) were calculated for production and transportation of oil over the 27-year expected production life of the DiapirField Leases. Similar estimates were also calculated for production and transportation of oil from existing leases and for transportation of Canadian oil. Oil spill Trajectory Simulations Oil spi...
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