4 million gallons a day!

The latest video footage of the leaking Deepwater Horizon oil spill in the Gulf of Mexico show that oil is escaping at the rate of 95,000 barrels — 4 million gallons — a day, nearly 20 times greater than the 5,000 barrel a day estimate BP and government scientists have been citing for nearly three weeks, an engineering professor told a congressional hearing Wednesday.

The figure of 5,000 barrels a day or 210,000 gallons that BP and the federal government have been using for weeks is based on satellite observations of the surface. But NASA’s best satellite-based instruments can’t see deep into the waters of the Gulf, where much of the oil from the gusher 5,000 feet below the surface seems to be floating.

Federal officials testified in hearings on Tuesday that they were putting together a crack team to get to the bottom of big the spill really is. That effort comes a month after the April 20 explosion that triggered the unprecedented oil spill in deep waters of the United States. Experts say knowing that amount is crucial for efforts to cap the broken wellhead and to monitor and clean up the oil.

Steve Wereley, an associate professor of mechanical engineering at Purdue University, earlier this month made simple calculations from a video BP released on May 12 and came up with a flow of 70,000 barrels a day, NPR reported last week. Werely on Wednesday told a House Commerce and Energy Committee subcommittee that his calculations of two leaks that show up on videos BP released on Tuesday showed 70,000 barrels from one leak and 25,000 from the other.

He said the calculation could be off by 20 percent — meaning the spill could range from between 76,000 to 104,000 barrels a day. But Wereley said he would need to see videos that were not compressed and showed the flow over a longer period so that it would be possible to get a better calculation of the mix of oil and gas from the wellhead.

Rep. Ed Markey, D-Mass., who chaired the hearing, promised to get that information from BP and make it possible for other scientists to use other methods to get a more accurate calculation of the size of the spill.

“The true extent of this spill remains a mystery,” Markey said. He said the BP had said that the flow rate was not relevant to the cleanup effort. “This faulty logic that BP is using is … raising concerns that they are h iding the full extent of the damage of this leak.

Renee Schoof @'McClatchy'