It is now clear: Hurricane Katrina is the most tragic and costly environmental disaster in the recent history of the United States.
As the hundreds of thousands of people begin returning to affected areas, they will wade into places wrought with environmental dangers.
Inside the flooded areas Louisiana were 60 chemical plants, oil refineries and petroleum facilities. Flooding caused six major oil spills between the mouth of the Mississippi River and New Orleans and several smaller spills in other places. Fifty thousand barrels have been recovered, but Environmental Protection Agency (EPA) officials estimate another 160,000 barrels were not recovered. Each barrel contains about 42 gallons of oil.
Oil from the 350,000 flooded vehicles in the area will take several years to decompose. The sewage system was also overrun during the hurricane. The EPA announced on Sept. 16 high levels of E-coli, a toxin-producing bacterium, in sediment around the city.
Pollution is not the only environmental factor preventing the safe rehabilitation of New Orleans. Geology Professor Jack Ridge doubts the city can sustain further sediment weathering. "Subsidence is one of the greatest threats to New Orleans," he said. Built on the Mississippi Delta, New Orleans rests on soil infiltrated with mud from the river. As the city develops and more structures are built, the accumulation of weight squeezes water out of the muddy ground. New Orleans is sinking further below sea level.
"When New Orleans was first settled, people were living above sea level," Ridge said. "But subsidence and flooding became a serious danger, so levees were built for protection. Unfortunately, subsidence is fastest under the levees because the levee itself and the sand underneath it weigh down the mud below."
If the New Orleans area was not developed, natural mechanisms would prevent it from sinking: The Mississippi River would frequently flood muddy areas so that the soil would not become dehydrated.
The levees currently surrounding New Orleans are designed to protect the city from category one or two hurricanes. Katrina was a category four hurricane and the levees failed when Lake Pontchartrain flooded.
"People knew that this was going to be a situation," Ridge said. The United States Geological Survey issued a report in 2001 detailing the various factors that put New Orleans at a very high risk for a type of large-scale natural disaster. The report identifies subsidence and climate-change induced sea level rise as the major threats to the city. Other risk factors include heavy precipitation and the deterioration of coastal wetlands that would naturally prevent flooding.
"There is a knee-jerk reaction to rebuild," Ridge said. "But nobody has really thought of a plan for that. At what point can you not conceivably build levees any higher?"
Ridge compared the quality of land in New Orleans to the quality of land in Venice, Italy. "Venice is another city that has undergone subsidence," he said. "Those canals used to be streets."
Galveston, Texas, experienced a 1990 flood comparable in strength to Katrina. But Galveston is not prone to subsidence. In response to the flood, Texas raised Galveston by 10 to 15 feet, constructing the extra ground with sand. This would not be a reasonable solution for New Orleans, Ridge said: The subsidence in the New Orleans area would prevent building up ground.
"It is important to restore local wetlands," Ridge said. "That is the one thing that can be done in the way of prevention."
The Army Corps of Engineers predicts it will take until mid-October to pump all of the excess water out of the flooded areas of New Orleans. According to Philip Clapp, head of the Washington-based National Environmental Trust, clean-up costs will exceed the $62 billion allocated from Congress.
"A clean-up like this has never been attempted before," Ridge said. "New Orleans is now basically like a giant Superfund site."
Superfund sites - that is, areas designated by the EPA to receive immediate as well as long-term waste management and remediation - are traditionally about a football field long. Three Superfund-size sites were flooded in New Orleans.
In a recent Los Angeles Times article, Hugh Kaufman, a senior policy analyst at the EPA, said it was "reckless and irresponsible" for the EPA to imply that it would be safe for people to move back into New Orleans. He compared the current situation in New Orleans to the EPA's hasty and ultimately inaccurate assessment of the air quality in downtown Manhattan following Sept. 11, 2001.
