U.S. logs 7 years without massive oil spill

The U.S. offshore is moving into its seventh year without a massive tanker oil spill.

Whether that achievement can be sustained remains to be seen, concludes World Information Systems (WIS), Cambridge, Mass., in a new study.

WIS calls massive spills those of about 24,000 bbl.

The last massive spill occurred June 8, 1990, in the Gulf of Mexico when the Norwegian tanker Mega Borg exploded and caught fire 57 miles southeast of Galveston, Tex. (OGJ, June 18, 1990, p. 13). In that one, 121,429 bbl of Angolan crude oil burned or spilled.

Since 1991, the volume of oil lost each year in U.S. waters during major spills-at least 238 bbl-has been low compared with 1978-90.

During January 1991-December 1995, major tanker spills off the U.S. declined to an average oil loss of 2,047 bbl/year. That's 2% of the average of 88,095 bbl/year the previous 13 years, WIS says.

WIS Pres. and Golob's Oil Pollution Bulletin Publisher Richard Golob said the current period of about 73 months without a massive tanker spill in U.S. waters is unprecedented in the 18 years covered by the WIS tanker loss report.

The report covers 98 major spills during 1978-95.

Spill history

During 1995, a combined total of 3,785 bbl of crude was lost in four major tanker spills, the study notes.

The volume lost in 1995 is below the annual average for 1978-90. The 1995 loss was the highest in the past 5 years and the only annual loss during that period to exceed 2,380 bbl.

A total of 1,167 bbl of crude oil was lost in two tanker spills in 1994, 1,642 bbl in three spills in 1993, 2,310 bbl in 1992, and 1,310 bbl in 1991. During 1978-90, crude losses in all were less than 2,380 bbl in only 1 year-1983, when a total of 2,190 bbl was lost in three spills.

Before 1991, the longest period in the WIS study without a massive spill was 53 months, between the October 1984 Puerto Rican spill off San Francisco and the March 1989 Exxon Valdez spill in Prince William Sound, Alas.

One tanker spill during that period, the September 1988 Esso Puerto Rico spill on the Mississippi River near New Orleans, was slightly less than 23,810 bbl.

Prevention measures

Massive spills are low probability events that occur at irregular intervals, WIS points out.

But, as its study notes, it remains to be seen whether the recent period without a massive tanker spill in U.S. waters represents the first phase of a sustained decline in the frequency of these events.

Several developments since 1990 may have reduced the risk of massive tanker spills.

Following the Exxon Valdez oil spill, the U.S. Congress enacted the Oil Pollution Act of 1990, which provides statutory authority for numerous federal tanker safety and pollution prevention regulations. Many states, including Alaska and Washington, also have enacted stringent vessel safety regulations to prevent spills in their waters.

In addition, oil companies, transportation companies, and other groups have undertaken voluntary spill prevention initiatives, including stricter environmental standards, improved training, and vessel routing changes. Measures include increased cooperation with the U.S. Coast Guard and other federal and state regulatory agencies.

Tank barges

Although no tanker spill in U.S. waters has exceeded 2,380 bbl during the past 5 years, a number of tank barge spills have.

The U.S. tank barge North Cape spilled more than 19,000 bbl of heating oil last winter when it ran aground off Moonstone Beach, R.I., during a storm (OGJ, Jan. 29, p. 49).

Two years before that, the U.S. tank barge Morris J. Berman ran aground on a coral reef off San Juan, P.R., and spilled about 15,000 bbl of fuel oil Jan. 7, 1994.

The U.S. tank barge B No. 155, which collided with a freighter and another barge at the mouth of Tampa Bay Aug. 10, 1993, spilled about 7,800 bbl of fuel oil.

Vessel size

The study shows that only four tankers larger than 200,000 dwt were involved in major spills. However, those four accounted for 25%, or 288,095 bbl, of the total volume of oil lost.

The largest number of spills-55-involved tankers of 30,000-99,999 dwt. Within this group, smaller tankers had the greatest number of losses, with vessels of 30,000-49,999 dwt size accounting for 25 spills.

Tankers of 50,000-69,999 dwt capacity accounted for the largest oil loss of any category, with more than 350,000 bbl combined from 11 spills.

Tankers sized 70,000-99,999 dwt were involved in 19 spills, resulting in total oil losses of about 97,000 bbl.

Registry, region, causes

The flag of registry, the study says, was known for 94 of the 98 tankers involved in major U.S. spills in 1978-95.

Thirty tankers were registered in the U.S., followed by Liberia with 24, Greece 8, Norway 7, and the U.K. 5. A total of 20 vessels registered in 15 other countries spilled oil during the period.

Gulf and Atlantic Coast regions each had 39 spills, Pacific Coast areas 18, and the Great Lakes/St. Lawrence Seaway two.

Louisiana and Texas together accounted for 35 spills, New Jersey eight, Alaska seven, and Massachusetts and Pennsylvania six each.

Oil volumes spilled in those areas totaled Gulf Coast 654,762 bbl, Pacific 376,190 bbl, Atlantic 92,857 bbl, and Great Lakes/St. Lawrence Seaway 20,976 bbl.

Grounding was the main cause of major U.S. spills during 1978-95, with 24% of the total. A total of 16 spills, or 16%, occurred during cargo loading, unloading, or transfer operations.

Other main causes were: collision 13 spills, or 13%; 12 equipment malfunction 12%; 10 ramming 10%; 7 structural failures 7%; and 6 explosion or fire 6%. The other 10 spills, or 10%, resulted from other factors or undetermined causes, the study reports.