Just two hours before the Deepwater Horizon exploded, a major test revealed a “very large abnormality” in the well, but workers simply ignored it and kept working, BP revealed in a report to Congress yesterday. Previously, BP had said the test was inconclusive, the Wall Street Journal notes, but now the company says ignoring it may have been the “fundamental mistake” that led to the explosion.
It certainly wasn't the only one, however. Workers ignored several other equipment readings as well, the New York Times reports, and took the risky step of replacing the heavy mud in the pipe with seawater. The cement meant to seal the well in an emergency also appears to have been contaminated. The report also notes the involvement of TransOcean and Halliburton on the rig, but BP's CEO added, “it is simply too early—and not up to us—to say who is at fault.”