What Can the 1969 Santa Barbara Oil Spill Teach Us About Trusting Estimates?

History—and science—have a lot to teach us here in Santa Barbara, California.

For many Santa Barbara, California, residents, last week’s oil spill stirred up painful memories. In 1969, this region was the site of what is still one of the largest spills in United States history, when an estimated 3.3 million gallons of oil poured from a ruptured well located five miles offshore, in nearby Summerland. The spill is often credited with catalyzing the U.S. environmental movement.

In the wake of that 1969 spill, researchers published dozens of scientific reports, tallying the oil’s effects on the environment and on the people of Santa Barbara. We’re gathering the results of those studies here, as well as what lessons we can learn for the recent spill that’s still staining Santa Barbara’s water and shoreline.

HOW BIG IS A SPILL? IT DEPENDS ON WHO’S MEASURING

The 1969 Santa Barbara disaster was an early example of the wide variation that can occur when oil companies, federal agencies, and independent researchers estimate how much oil has been spilled. Below is a table of estimates from the time, collected by University of California-Santa Barbara biologists Michael S. Foster and Robert W. Holmes in their review, “The Santa Barbara Oil Spill: An Ecological Disaster?”

(Chart: Michael S. Foster/Proceedings of the International Symposium on the Recovery of Damaged Ecosystems)

Ultimately, the Allen estimate, which comes out to 3.3 million gallons spilled overall, was considered the more reliable.

• The Effects of the 1969 Spill on Animal Life: The spill killed 9,000 birds and nine million barnacles.

Estimates of the extent of recent leaks have varied even more dramatically. Take, for example, the 2010 Deepwater Horizon spill: Initially, the U.S. Coast Guard said no oil was leaking from the exploded well. The Coast Guard later amended that prediction, to 42,000 leaked gallons per day. By 2012, the final estimate was tallied at 2.4 million gallons … per day.

Plains All American Pipeline, the company operating the pipe that burst in Santa Barbara last week, estimates that 105,000 gallons of oil spilled, with 21,000 gallons reaching the ocean. We haven’t yet seen any other sources estimate the extent of that leak.

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