I hope all the people who keep telling me how safe nuclear power is read this assessment. The fact is, humans make errors. Machines make errors, too. The question is, how big a risk can we afford to take?

Investigators have focused on the minute-to-minute decisions and breakdowns to understand what led to the explosion of the Deepwater Horizon, killing 11 people and setting off the largest oil spill in United States history and an environmental disaster. But the lack of coordination was not limited to the day of the explosion.

New government and BP documents, interviews with experts and testimony by witnesses provide the clearest indication to date that a hodgepodge of oversight agencies granted exceptions to rules, allowed risks to accumulate and made a disaster more likely on the rig, particularly with a mix of different companies operating on the Deepwater whose interests were not always in sync.

And in the aftermath, arguments about who is in charge of the cleanup — often a signal that no one is in charge — have led to delays, distractions and disagreements over how to cap the well and defend the coastline. As a result, with oil continuing to gush a mile below the surface in the Gulf of Mexico, the laws of physics are largely in control, creating the daunting challenge of trying to plug a hole at depths where equipment is straining under more than a ton of pressure per square inch.

Tad W. Patzek, chairman of the Petroleum and Geosystems Engineering Department at the University of Texas, Austin, has analyzed reports of what led to the explosion. “It’s a very complex operation in which the human element has not been aligned with the complexity of the system,” he said in an interview last week.