Wednesday, October 5, 2011

Deepwater Horizon Accident

A major news of 2010 was the accident at the Deepwater Horizon oil well in the Gulf of Mexico.  A disastrous fire engulfed the oil platform when a surge of gas issued from the well. Eleven workers died in the accident, oil gushed out from the broken pipe at the floor of the sea. Video of the oil pouring out provided dramatic images that were flashed all over the media. The actual quantity of the spill was difficult to ascertain initially, and estimates ranged from 10,000 to 100,000 barrels per day. After the fact, it was determined that the maximum rate of spill was about 62,000 barrels a day and over the three-month period of the spill, 4.9 million barrels of oil had poured out. Over 600 miles of the coastline had been affected.  Fishery and tourism are major industries of the region, and suffered enormous losses. It is uncertain as to how long before those operations would regain a sense of normalcy.
Deepwater Horizon is only one of several major events in which large amounts of oil were discharged into seas and oceans. Since 1978 four major events have occurred:
·      The breaking up of Amoco Cadiz off the coast of Brittany, France in March 1978 spilling about 1.7 million barrels of oil.
·      Ixtoc 1 oil well disaster in the Bay of Campeche releasing approximately 3.4 million barrels of oil over nine months beginning June 3, 1979.
·      The running aground of Exxon Valdez in Prince William Sound on March 24, 1989 resulting in a spill of 0.23 million barrels.
·      Sabotage by retreating Iraqi forces in January 1991 resulting in a spill of over 7.1 million barrels.
 Each of these incidents is different in significant ways—the amount of oil discharged, whether it was released at the surface or under sea, local ecology and environmental conditions such as water currents and temperature. Yet, tragic as these events have been for the people and animals directly affected, they also provide a strong testament to the resilience of the environment as recovery of the environment around them has taken three to five years.
The second of these, Ixtoc 1, initiated in on June 3, 1979 is eerily similar to the ongoing Deepwater Horizon disaster as it too entailed a blowout of an exploratory well situated in the Gulf of Mexico releasing oil under sea and not far from a prosperous fishing community. Many of the unsuccessful techniques employed for mitigating the disaster then were also used at Deepwater Horizon with equally unsuccessful outcomes. The blowout preventer failed in both instances. Dispersants, skimmers and booms were used then, as today, to reduce the impact of the oil spill. Ixtoc 1 disaster was finally contained when a relief well was drilled.  It took about nine months to complete and provide a controlled flow of oil. The relief wells at Deepwater are expected to take shorter times because of improvements in remote underground manipulations and drilling technologies; we are now able to drill deeper, faster, and more accurately.
While most of the oil released from Ixtoc 1 went toward the ocean to be dispersed in different ways, some oil flowed along the coastline severely damaging the environment along the Mexican shoreline and affecting the coastal fisheries. Special efforts were exerted to capture and relocate a small group of unique sea turtles – they survived and have since been restored to their former grounds where they are in good shape. Surveys conducted in 1981 showed that the shore vegetation had revived. Within three to four years fisheries had regained most of their productivity, although residues of oil can be found even today deep below the surface.
The first and third incidents, Amoco Cadiz and Exxon Valdez, were shipping accidents resulting in rapid discharges of large volumes oil on the surface. The latter spilled a relatively smaller volume of oil, but it did so in a very sensitive area that was the location of commercial and sports salmon fisheries as well as the habitat of many varieties of wildlife. The spill covered about 1,300 miles of coastline and 11,000 square miles of sea with varying amounts of oil. Various cleanup techniques were applied in both, none of which were particularly successful. Perhaps 10% of the oil was recovered, the rest was carried out to sea, and/or deposited on the channel floor.
In both these spills, high pressure water cleaning was used. It proved effective when applied to gravel and rock surfaces but less so if the vegetation was fouled. Natural remediation in the affected marine environments seemed to work best if left alone and the fouled area returned to life as early as three to five years following the spill with attendant resumption of the previously normal commercial and recreational activities. History suggests that if proper procedures are taken there will be quick recovery of the usual activities along the currently affected coasts of Louisiana, Mississippi, Georgia, and Florida coasts.
The fourth was a deliberate act of sabotage committed by Iraqi forces as they retreated from Kuwait on January 23, 1991.  Oil was released from storage tanks and tankers.  The amount released the sea was estimated to range from two to six million barrels. Apparently, no effort was made to stop the flow or cleanup the residues. Three years later a survey found little ecological damage but later ones reported significant residual ecological damage. 
For perspective, we note that about 1 million barrels gallons of oil naturally seeps in the Gulf of Mexico every year. The US Gulf region, as also the southern California coast, has been contaminated by tar since prehistoric times. Modern dwellers on the coast are accustomed to using kerosene or similar solvents to remove tar from their seagoing equipment and their bodies after their sea oriented play or work.
Based on the collective experience from these earlier disasters, we can expect that the Gulf of Mexico to also recover in a few years. The Food and Drug Administration has recently conducted tests on seafood from the Gulf of Mexico for contaminants but has found few problems. Recent reports of economic recovery in the region have also been encouraging, although the jury is still out on the long-term prospects.

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