Government Estimates of Oil From Spill Raise New Doubts Among Researchers

In the early days of the oil spill that followed the explosion of the Deepwater Horizon drilling rig in the Gulf of Mexico, university researchers helped disprove corporate and governmental assurances about the size and spread of the oil slick. Could that be happening again?

The rig, which was owned by Transocean Ltd. and leased to BP, was destroyed in the explosion on April 20, causing oil to spew from a ruptured well a mile below the surface.

The federal government on Wednesday issued a report saying that 4.9 million barrels of oil, plus or minus 10 percent, had leaked from the well from the time of the explosion until it was capped on July 15. The report also says that most of that oil has been captured, dispersed, or evaporated, leaving only 26 percent of it remaining in a form that could cause damage to the waters or coastlines.

But the report contains few details of how the government arrived at those figures, and it’s already producing some skepticism about whether the numbers will hold up.

Robert G. Bea, a professor of civil and environmental engineering at the University of California at Berkeley, said the government’s report leaves open a lot of basic questions about what measurements it used and what calculations it applied.

“There are not sufficient details provided to be able to evaluate the accuracies of the estimates,” said Mr. Bea, who has more than 55 years of engineering experience with offshore platforms, mostly in private industry.

And the 10-percent margin of error “seems to be incredibly small” given all the variables involved, said Mr. Bea, who has asked the Deepwater Horizon Study Group at Berkeley to make a careful review of the figures. —Paul Basken