Ixtoc 1, the offshore well in the Gulf of Mexico that spilled more than 3 million gallons of oil into the gulf over the last nine months, has been capped. But the spill -- the largest on record -- has raised questions that are likely to linger for years. What caused the blowout of the Mexican well on June 3, 1979 , and could a similar disaster happen in United States waters? What is the long-range environmental impact of the spill?
There is relief in Texas that the well is capped. Mexican oil blackened beaches here last summer and sent the tourist trade into a nose dive. Until recently there was concern the oil would drift north again this summer.
John Robinson, manager of hazardous materials response for the National Oceanic and Atmospheric Administration (NOAA), was part of the US team assembled during the spill to protect the US environment and to document the impact of the spill on the coastal ecology. He has come away from the experience apprehensive that a similar disaster could be repeated in US waters.
"It has caused us to be more concerned about offshore oil development in general," he says. As a result, NOAA is working to improve its contigency plan for responding to an oil spill in the environmentally sensitive Georges Bank area off the New England coast which was opened up for oil exploration in a federal lease sale last December.
NOAA is making a thorough assessment of the coastal ecology of several New England states so that in the event of a spill federal officials will know which areas are most vulnerable. Mr. Robinson also intends to develop a better federal oil spill response plan for the California coast.
Officials of American oil firms concede the Mexican spill has given offshore development a "black eye," but they insist that in all probability such an accident could not happen in US waters.
Several oil company executives, asking not to be named, said the blowout was caused by an improper drilling practice. The Mexicans, it is generally agreed among knowledgeable US sources, removed the drill pipe after circulation had been lost in the well (fluids injected into the well were not circulating back up the drill shaft as they should have).
These sources say removing the drill pipe was part of a plan to correct the loss of circulation but pulling out the drill pipe under these circumstances removed what control the workers had over the well. It was "a mistake that I just cannot imagine being repeated," insists one top oil executive.
There has been no official explanation from Pemex, the Mexican national oil company, as to the cause of the blowout, but the issue will likely be addressed in several pending lawsuits in Texas seeking compensation for damages from the spill.
Pemex capped Ixtoc 1 by drilling two relief wells through which water was pumped to offset the natural pressure of the spilling oil. Cement was then injected to seal the Ixtoc well.
Although nine months and cost more than $131 million, according to Pemex, most knowledgeable US observers agree the job was done as rapidly as possible and with the best technology available.
The extent of environmental damage to the Texas coast from Ixtoc 1 remains an open question. Indeed, NOAA officials have asked Congress for more money to study the impact of the spill in order to determine the long- term effect of oil on the environment -- a subject on which surprisingly little is known, according to Mr. Robinson.
What little evidence has been gathered indicates:
* There has been a major disruption of the bird population on the south Texas coast. The loss of birds is not due to death from direct oiling. Rather, the birds seem simply to have moved elsewhere, perhaps because of the impact of the oil on their habitat and food sources. Bird numbers have been reduced 20 to 50 percent, Mr. Robinson estimates.
* Sea life along the beaches declined "suddenly" under the impact of oil and has been "very slow" in recovering.
* There remain large tar mats offshore where oil has accumulated on the ocean floor. Mr. Robinson says there are 37 of these "reef- like structures" and the hydrocarbon level in the vicinity is high.The long-range impact of these concentrations of tar is unknown.