Fate of the oil from the DWH tragedy

Captains

According to the Federal Interagency Flow Rate Technical Team, somewhere between 94 million and 184 million gallons of Louisiana crude oil has spilled into the Gulf of Mexico since the MODU Deepwater Horizon sank in April. NOAA and EPA are the two key agencies assisting the USCG to determine the fate of all that oil. Additionally, since each of the response tactics (containing, skimming, burning, dispersing, washing, bio-remediating) is potentially damaging to the environment, NOAA and EPA also advise the USCG FOSC on which tactics are best.

Although the quantity has been huge (9 to 16 Exxon Valdez size spills), the oil volatility and viscosity, offshore location and mile deep source of the Deepwater Horizon spill have mitigated some of its impact to shorelines and wildlife. According to NOAA and EPA, half the oil is naturally dispersing - first in the water column, then into the air.

(Theoretically, if 150 million gallons of oil dispersed in a cubic mile, or 150 trillion gallons sea water, there would be about 1 part oil per million parts water. In the Gulf of Mexico, oil-eating microbes would quickly consume it.)

31.5 million gallons from the Macondo well have been captured at the well head by the riser insertion tube and top cap to the Discovery Enterprise, and the choke line to the Q-4000. About 11 million gallons have been burned in fire-booms on the surface and about 32 million gallons of emulsified oil have been collected with skimmers. NOAA estimates the rest is spread out over about 18,000 square miles and EPA studies suggest it has a half life of 12 to 70 days.

RADM W

NOAA Models Long-term Oil Threat to Gulf Coast Shoreline

“This NOAA model shows where oil may be likely to travel, thereby giving coastal states and communities information about potential threats of shoreline impacts. This kind of information should assist in the preparation of adequate preparedness measures,” said Jane Lubchenco, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator.

When did EPA start monitoring air quality in the Gulf states? EPA responders were on the ground with portable monitoring devices starting on April 28th. EPA’s twin engine aircraft, ASPECT, was deployed on April 29th to collect air sampling data and provide aerial photographs of the migrating oil slick. EPA began oil spill specific air monitoring from our TAGA buses on April 30th.

We began water sampling on April 30th and results from water sampling are typically available four days after sample collection. We began coastal sediment sampling on April 30th, and we expect to get results from these samples in the next few days. EPA is closely coordinating with the air monitoring efforts ongoing in the states of Louisiana, Mississippi, Alabama and Florida.

What do we know about the biodegradation rate of non-dispersed oil?
Extensive laboratory and field research has been done on the biodegradation of crude oil. The South Louisiana crude in the Gulf spill is considered a “light” crude oil and is known to degrade at a faster rate than heavier weight oils from other locations such as Alaska. Some studies suggest that the half-life for Louisiana crude is 12-70 days in seawater. There are a number of factors that affect the biodegradation rates of oil, such as water temperature, oxygen content, and presence of micro-organisms.