Crossposted with www.thegreengrok.com.
How unusual is it for 4.9 million barrels of oil to be spilled into the ocean?
The newspapers tell us that the crisis is over. BP's Macondo deepwater oil well, drilled by the Deepwater Horizon rig that blew out on April 20th, is cemented in now, and a permanent fix looks to be around the corner. Thankfully, there will be no new images of oil gushing out of BP's now famous well at the bottom of the Gulf of Mexico.
While the acute phase of the spill is now over, the longer-term impacts are largely unknown.
Still, about half of the oil released by BP's well remains in the environment -- with roughly a quarter "unaccounted for" either on or just below the surface, washed up on shorelines, or buried in sand and sediments, and another quarter "dispersed (either naturally or as a result of operations) as microscopic droplets into Gulf waters." Of note, the government report points out that those microscopic droplets still pose a threat: "until it is biodegraded, naturally or chemically dispersed oil, even in dilute amounts, can be toxic to vulnerable species."
It will be years before we know what, if any, are the long-term environmental consequences. But as a media event, the spill caused by the Deepwater Horizon blowout was huge. Did the accident warrant all that special attention? Was it really a singular event in the world of oil extraction and transport, or just one of many? Let's take a look.
A Look at Five Major Accidents and the Millions of Barrels of Oil They've Spilled
Estimated number of barrels of oil spilled from ...
... the Deepwater Horizon blowout in the Gulf of Mexico off the Louisiana coast in April 2010: 4.9 million
(details here [pdf])
... the Ixtoc I blowout in the Gulf of Mexico off the Yucatan Peninsula in June 1979: 3.3 million
... a ruptured pipeline in July 2010 at the port of Dalian in northeastern China on the Yellow Sea: 10,000 - 630,000
... the Exxon Valdez grounding in Alaska's Prince Williams Sound in March 1989: 257,000
... the Montara blowout in August 2009 off the coast of Australia in the Timor Sea: 30,000 - 210,000
Oil Spilled from Tankers
Approximate number of barrels spilled from tankers globally from 1970 to 1979: 22 million
Approximate number of barrels spilled from tankers globally from 2000 to 2009: 1.5 million
Average Amount of Oil Spilled Yearly Into the Oceans
Estimated number of barrels of oil spilled on average in North American marine waters each year: 700,000
Estimated number of barrels of oil spilled on average into marine waters worldwide each year: 4.7 million
Estimated number of barrels of oil released on average into marine waters worldwide from natural seeps: 4.2 million
Number of Accidents Causing Oil Spills in the Ocean
Number of major oil spills in 2009 on the U.S. Outer Continental Shelf (tracked by the U.S. Minerals Management Service): 10
U.S. Record Holders for Largest Marine Oil Spills
Largest U.S. marine oil spill: Deepwater Horizon
Second largest U.S. marine oil spill: Exxon Valdez (read more about the lingering effects of that spill)
Bottom Line ...
There've been lots of accidents and oil spills. In fact, spills around the world, both on land and in the ocean, offer a troubling picture of this environmental threat. The latest oil spill from BP's deepwater well in the gulf is just one of many, but when it comes to sheer volume, the Deepwater Horizon holds the worldwide title for accidental, marine spills, but it's not the biggest overall U.S. spill. The nation's largest oil spill to date is the Lakeview Gusher, which emptied some nine million barrels of oil into the California
desert in 1910 near the towns of Maricopa and Taft over the course of 17
months. Let's hope none of these record holders is ever topped.
The Trustee Council, formed to oversee restoration of the Alaskan ecosystem that was injured by the Exxon Valdez accident, notes on its Web site that while the Exxon Valdez spill is "still one of the largest ever in the United States, [it] has dropped from the top 50 internationally (view a list of top oil spills worldwide). It is widely considered the number one spill worldwide in terms of damage to the environment, however. The timing of the spill, the remote and spectacular location, the thousands of miles of rugged and wild shoreline, and the abundance of wildlife in the region combined to make it an environmental disaster well beyond the scope of other spills."
The Australian government's official report [pdf] on the oil spill notes that the estimates of the amount of oil spilled came from the operator and that "for safety reasons this estimate could not be confirmed at any time during the incident, nor was it possible to provide a more accurate assessment. The uncontrolled release continued until 3 November 2009 and the response operations continued until the well was capped on 3 December 2009 (105 days)."
Note that this statistic and the one that follows (for the amount of oil spilled on average into marine waters worldwide each year) include extraction, transportation, consumption of oil based on volumes released on average during the 1990s. Using data from earlier decades when more oil was typically spilled would increase these average estimates. A conversion factor of seven was used to convert metric tons to barrels of oil.
The U.S. government defines a major spill as those larger than 50 barrels. MMS tracks spills on the Outer Continental Shelf, excluding tanker spills.
The NOAA database includes all spills or potential spills of any size in marine or inland waterways.