New estimates of the amount of oil spilled by Exxon Mobil in Mayflower, Arkansas have grown far beyond the initial figures of 84,000 gallons. Susan White at Inside Climate News tries to get a sense of the actual size of the spill:

Engelmann said Friday that “3,500 to 5,000 is not our number” and suggested that InsideClimate News ask PHMSA where those figures came from. A PHMSA spokeswoman confirmed that the higher figures came from ExxonMobil Pipeline Company (EMPCO).

Reports posted online by the U.S. Environmental Protection Agency estimate the spill even higher—at 4,000 to 7,000 barrels—as much as 40 percent more.

Austin Vela, the EPA spokesman at the spill site, said the agency stands by its 4,000 to 7,000 barrel estimate. When asked why those higher numbers aren’t being included in the daily press releases issued by the joint command of the cleanup operation, Vela did not respond. The joint command includes five EPA employees as well as ExxonMobil officials.

Few, if any, media reports have cited the higher official EPA figure.

Aside from just a normal curiosity about how big of a mess there is to clean up, pinning down the number of barrels spilled has important financial implications:

Estimating the size of a spill in the first days after an accident can be contentious, because the volume of the spill affects the fines and penalties companies may eventually pay for violating the Clean Water Act. Fines can be as high as $1,100 for every barrel spilled. If gross negligence or willful misconduct is proven, violators can be forced to pay as much as $4,300 per barrel.

And the true size of the spill could be even larger:

Exxon says it shut down the pipeline within 16 minutes of detecting a pressure drop last Friday afternoon. The line continued to leak for 12 hours as it lost pressure, according to the PHMSA corrective action order. Two valves 18 miles apart were shut to isolate the leaking section of pipe.

If full, the 20-inch pipe would contain about 36,000 barrels of oil, or more than 1.5 million gallons.

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