It's been a year and a half since oil suddenly gushed from the Deepwater Horizon drilling rig into the Gulf of Mexico.
In the early days, rig operator BP estimated about 1,000 barrels a day might be escaping into the gulf. The true number? More like 50,000 to 60,000 barrels — or more than 2 million gallons — every day for nearly three months.
How did we learn it was so high?
U.S. Sen. Bill Nelson, D-Fla., told colleagues this month that it wasn't until he and Sen. Barbara Boxer, D-Calif., were able to "wrangle the actual streaming video" from BP and put it on his website that scientists were able to calculate the flow.
The senior senator from Florida, responsible for lifting the veil on a disaster unfolding 5,000 feet underwater?
We reached out to scientists, reviewed news and video from the time, checked official reports on the spill and spoke with the senator's office.
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On April 20, 2010, an explosion ripped through the drilling rig, killing 11 crew members. As flames raged above water 49 miles off the coast of Louisiana, something equally violent was happening beneath the surface.
It wasn't yet clear what.
But within a day, a nonprofit group called SkyTruth, led by a geologist who had worked for the energy industry, began collecting and analyzing satellite images. The group got help from Florida State oceanographer Ian MacDonald.
On April 24, BP said a broken riser pipe was leaking 1,000 barrels a day. A few days later, the National Oceanic and Atmospheric Administration boosted the estimate to 5,000 barrels. That was the first official "flow rate estimate." It would be used for weeks.
In late April and early May, SkyTruth said satellite images and Coast Guard maps of the slick showed the flow might be more than four times that.
But none of those estimates could fully account for what was happening below the surface, where chemical dispersants created tiny droplets that spread in underwater plumes.
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On May 12, BP released a 30-second video of oil and gas spilling from the end of a broken pipe — and scientists scrambled to update their estimates, which now ranged from 20,000 to 100,000 barrels a day. By mid May, media reports spread additional doubt about the 5,000-barrel estimate. Rep. Edward Markey, the Massachusetts Democrat who chaired the Energy and Environment Subcommittee, sent BP a letter questioning the size of the spill.
A few days later, Sens. Nelson and Boxer sent their demand for underwater video. They soon got seven hard drives of high-resolution digital imagery, thousands of hours, said Nelson spokesman Dan McLaughlin. Low-resolution streaming video — what you may have seen online — wouldn't give scientists the detail they needed, so the senators' offices also uploaded high-resolution files to large-file transfer sites on the Web and, in some cases, even copied the hard drives and sent them to researchers, such as Timothy Crone at Columbia University.
In June, the senators repeated their call for video evidence, this time for all video records.
In the Oct. 29, 2010, issue of Science magazine, a report co-authored by Crone said the oil's flow was at least 10 times higher than first reported. It credited high-resolution video data "provided by the office of Senator Bill Nelson and by the Senate Committee on the Environment and Public Works."
"Sen. Nelson was one of the strongest proponents of open data access, and his work along with the work of others on that committee were critical for the work of independent scientists to go forward," Crone told PolitiFact Florida.
Paul Ruscher, a Florida State professor who along with MacDonald urged that BP release more information, said much of what scientists suggested was initially ignored.
"It was a staffer from Sen. Nelson's office who was contacted at some point, and whom I then contacted, to try to encourage both Senate and House energy committee members to get involved," he said.
Ruscher said Nelson and other politicians, including Sen. John Kerry, D-Mass., and Markey, should get full credit for pushing NOAA, the Coast Guard and BP to release video.
Final official estimates came from the Flow Rate Technical Group, which used several methods to estimate the amount of oil that streamed from Deepwater Horizon. Among its evidence: high-resolution video.
Nelson told his Senate colleagues, "It was not until Sen. Boxer … and I were able to wrangle the actual streaming video (of the Deepwater Horizon oil spill) from 5,000 feet below the surface and put it up on my website that the scientists could then calculate how much oil was coming out."
A casual listener might think scientists were unable to make early calculations that challenged BP's word without video from Nelson's website — and that's not quite the case. Meanwhile, other lawmakers also pushed for greater openness. But letters, press releases and interviews show Nelson did play a key role in the release of critical data, and for that we'll rate his statement Mostly True.