BP’s cap on the ruptured gulf coast oil well is a two-edged sword.  On the one hand, there is a good chance it will hold and the problem will be solved.   On the other hand,  the cap makes it harder to verify whether this solution has failed.

The cap means that pressure is diverted elsewhere underground.  Right now there is a camera in place pointing at the capped part of the well.  When the cap was not in place this camera made it common knowledge whether oil was flowing into the gulf and it made quite clear how much.  With the cap however, “seepage” in other locations can only be measured by noisy tests that can easily be disputed by both parties.

For example, BP will cite:

Some seepage from the ocean floor is normal in the Gulf of Mexico, according to University of Houston professor Don Van Nieuwenhuise.

“A lot of oil that’s formed naturally, by the Earth, ends up escaping or leaking to the surface in the form of natural seeps and yes, there are a lot of these all around the world,” he said.

and the government will argue:

“If the well remains fully shut in until the relief well is completed, we may never have a fully accurate determination of the flow rate from this well. If so, BP — which has consistently underestimated the flow rate — might evade billions of dollars of fines,” Markey, D-Massachusetts, said in a letter to Allen released Sunday.

The deadweight loss of negotiation and litigation means that even if the risk to the gulf is substantially reduced by having the cap in place, it may still be better to uncap the well and seek solutions (such as extraction of the flowing oil) that can be monitored directly by the camera that is already there.