A document produced by the U.S. Coast guard is titled, “Pollution Incidents In and Around US Water, A Spill Release Compendium, 1969-2000“.
Their document states between 1971 and 2000, the U.S. Coast Guard identified more than 250,000 oil spills in U.S. waters. The total amount of oil spilled by these incidents was 6.18 million barrels, or 259,560,000 gallons (a barrel is 42 gallons according to the same document).
One of the fascinating statements from the report: “The number of spills increased in the last decade due to better reporting of spills less than 100 gallons.” The truth though, is the number of spills did not increase so much as the number of spills reported increased. In other words, because of the improvements in reporting, more spills were documented. However, this fact also implies there were probably even more spills occurring in the previous period, but they simply were not documented, because the better reporting process was not in place to catch them.
So the reference in the report to more than 250,000 spills is likely to be inaccurate, and larger due to underreporting. For example, in 1990-2000 the number of spills documented with the improved reporting was 88,197. In the previous decade (1981-1990) the number was 67,260 spills. So does that mean there were potentially another 20,000 spills from 1981 to 1990, if the rate of oil spills was relatively constant? From 1971 to 1980 there were 94,714 spills during a decade without the improved reporting, which means it is likely there were actually another 10 to 20 percent. So is the true total number closer to 290,000 oil spills in U.S. waters from 1971-2000?
Tankers and barges spilled 45% of the total number of barrels which entered U.S. waters. Pipelines spilled 16% of the total, and 92% of pipeline spills occurred onshore, not offshore.
The report also states only 2% of the total oil spilled came from offshore pipelines and facilities in the Outer Continental Shelf. Two percent of 259,560,000 gallons (total oil spilled) is 5,191,200 gallons of oil spilled in U.S. waters from the Outer Continental Shelf. (The OCS is those areas off the coastlines of the U.S regions, like the Gulf of Mexico, Pacific and Atlantic coasts, etc.)