Friday, July 8, 2011

How much oil leaked into the Yellowstone?

2 dollar calculator

A friend got me thinking about just how much crude oil we can reasonably estimate really did leak into the Yellowstone River during the 56 minutes it took ExonnMobil Pipeline Company to shut down the Silvertip Pipeline that burst last Friday.

ExxonMobil continues to stand by their estimate that 1,000 barrels, or about 44,000 gallons, leaked into the river late Friday night. Then again, ExxonMobil also said it only took 6 minutes to shut down the pipeline, then it was 30 minutes “at most,” and then we we finally learned through documents from the US Department of Transportation Pipeline and Hazardous Materials Safety Administration that it took 56 minutes to shut down the line.

So, as Gov. Brian Schweitzer likes to say, I pulled out my $2 calculator and did some calculations:

40,000 bbl a day/24 hours in a day=1,666.66 bbl per hour

1,666.66 bbl per hour/60 minutes per hour=27.77 bbl per minute

27.77 bbl per minute x 56 minutes= 1,555.55 bbl

Certainly there are other factors to consider. We don’t know how big the rupture was/is, and therefore what percentage of the oil flowing through the pipe was spewing out and under what pressures and volumes. We also don’t know how much oil was in the broken section pipe between the shut-off valves, or how much of that oil leaked into the river. We also don’t know if the pipeline was running at the 40,000 barrels per day volume, or if it was  running at higher or lower volumes. So it may be premature to say that ExxonMobil is underestimating the amount of oil that leaked into the Yellowstone River by more than a third.

Then again, given the lack of transparency that lead Schweitzer to pull the state out of the unified command, and the track record of other oil giants when it comes to the size of oil spills—for example, BP underestimated the Deepwater Horizon spill by up to five times; a recent Enbridge Energy pipeline leak in Canada went from four barrels to 1,500 barrels; Enbridge initially estimated that it’s pipeline leak in Michigan dumped 819,000 gallons of oil into the Kalamazoo River a year ago, that number was later upped to 1 million gallons—I think it’s probably a safe bet that we’re going to learn more oil spilled into the Yellowstone River than what we’re currently being told.

1 comment:

Anonymous said...

Good calculation - but you've only considered unidirectional flow. Oil would have been flowing into the river from both directions as this was a rupture in the middle of the pipeline and not at the terminus. Multiply by 2. Still . . . +/- 3,000bbl?

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