Now that BP has temporarily plugged the oil spill and remains confident that a successful permanent plug is within reach, federal scientists estimate 4.9 million barrels of oil have gushed into the Gulf since April 22. The calculation makes BP’s Deepwater Horizon oil spill the largest in history, far surpassing Mexico’s 1979 Ixtoc spill, which released 3.3 million barrels into the Gulf.
Government analysts believe the spill began more powerfully than it ended, releasing about 62,000 barrels of oil per day and gradually weakening as the weeks passed to about 53,000 barrels a day. A diminishing reservoir of hydrocarbons feeding the oil flow led to the lower pressure, scientists say.
BP originally estimated the spill’s size to be 1,000 barrels per day. That number was eventually bumped up to a still grossly inadequate 5,000 barrels.
The scientists say that the current estimates are accurate to within 10 percent. They also say that BP captured roughly 800,000 barrels of the crude in its containment efforts prior to the capping stack that successfully plugged the oil on July 15, which leaves over 4 million barrels, more than 168 million gallons.
When BP effectively refused to spend resources on measuring the oil spill, the Obama administration established a group of scientists dedicated to monitoring and studying the oil’s flow rate. In late May, the Energy Department group reported that between 12,000 and 19,000 barrels a day were gushing into the Gulf, but even that estimate was widely met with skepticism throughout the scientific community.
Not until BP capped the well did it have a truly accurate way of measuring the oil flow using pressure readings within the well. The government team continues to monitor the well and said that the estimate could be refined over time.
The spill estimate will be used to determine how much in civil penalties BP will pay the federal government. The penalties are based on a per-barrel rate that varies depending on whether the spill involved gross negligence.
The National Oceanic and Atmospheric Administration Director said that “The sheer volume of oil that’s out there has to mean there are some pretty significant impacts. What we have yet to determine is the full impact the oil will have not just on the shoreline, not just on wildlife, but beneath the surface.”