Investigators yesterday added a possible new explanation for some of the flooding that devastated New Orleans after Hurricane Katrina: contractors who may have skimped on construction materials in building the city's floodwalls and levees.
Experts probing the cause of the flooding have received at least a dozen allegations of major cheating by builders and possibly others involved in levee construction, two investigators said in testimony before a Senate panel. They said these were potentially criminal acts that may well have contributed to the collapse of the city's flood-control system on Aug. 29.
The allegations, although not proved, have prompted investigators to request a meeting next week with federal law enforcement officials to share details of the reports.
The list of alleged misdeeds includes the use of weak, poorly compacted soils in levee construction and deliberate skimping on steel pilings used to anchor floodwalls to the ground.
"What we have right now are stories of malfeasance and some field evidence that seems to correlate with those stories," said Raymond B. Seed, leader of one of three independent teams of experts investigating why the levees failed. Seed, an engineering professor at the University of California at Berkeley, said it is not yet clear how big a role such acts played in the failure of the levees.
The reports emerged from one of two Senate hearings held yesterday to examine why New Orleans's levee system failed so spectacularly, and how it might be rebuilt to prevent catastrophic flooding by the next hurricane.
New Orleans Mayor C. Ray Nagin asked President Bush and Congress to commit the nation to rebuilding his city's levee system to withstand a Category 5 hurricane, calling it necessary to win back workers and businesses. The existing 200-mile system was designed to withstand a Category 3 storm.
"We can do much better. We definitely can build to a world-class standard that we don't have today," said Nagin, citing storm barrier systems in the Netherlands, United Kingdom and Italy.
Most of the devastation caused by Katrina was inflicted not by high winds, but by massive flooding that resulted when the city's levees breached. Four major breaches and dozens of smaller ones occurred on the morning of Aug. 29, sending water surging across 80 percent of New Orleans and swamping an estimated 100,000 homes. About 1,000 people died.
The levees were designed by the U.S. Army Corps of Engineers and were built primarily by contractors hired by the Corps. The Corps has launched its own investigation of the levee failures; Paul Mlakar, a Corps scientist leading the inquiry, said though it is too early to draw firm conclusions, he promised a thorough investigation, with final results in July. The Corps is also cooperating with the independent investigations by the state of Louisiana, the American Society of Civil Engineers, and the University of California team, which is funded by the National Science Foundation.
Leaders of the three teams yesterday presented preliminary findings of their two-month probe to the Senate Homeland Security and Governmental Affairs Committee. In recent weeks, findings by the independent investigators have pointed increasingly to human error -- flaws in design, construction, or both -- as a probable culprit in the breaches of two key floodwalls along Lake Pontchartrain.
Although Army Corps officials initially suggested that the 17th Street and London Avenue canals were simply overwhelmed by Katrina's storm surge, the new findings confirmed that the two floodwalls were never overtopped by rising waters. Instead, the concrete walls toppled when their earthen foundations weakened and gave way.
"Failure of the 17th Street and London Avenue canals was due to a design that did not take into account the very weak nature of the soils," Ivor Van Heerden, an engineering professor and leader of the Louisiana team, said in prepared testimony. "The design criteria of these levees was not exceeded."
In the eastern part of New Orleans, which suffered the greatest impact, levees were overtopped by the storm surge. Still, poor design may have made floodwalls more likely to fail, Van Heerden said.
"Much of the flooding of New Orleans was due to man's follies," he said. "Not to have given the residents the security of proper levees is inexcusable."
Nagin, in his testimony before the Senate Environmental and Public Works Committee, said: "We need to rebuild this great city. . . . Now is the time for this country to make a commitment to upgrade our levy systems and associated protection with that." Existing Corps plans, he said, "will provide little comfort in a city devastated by a storm and whose flood protection is not as strong as it should be."
Committee members expressed concern at the slow pace of federal decisions. "People need absolute assurance that the level of hurricane and flood protection will be much greater than before Hurricane Katrina," Sen. David Vitter (R-La.) said.
The testimony underscored the centrality of the city's shattered, 200-mile levee system to both the Aug. 29 Hurricane Katrina disaster and to the future of New Orleans. Louisiana Gov. Kathleen Babineaux Blanco and Nagin have said a prerequisite to any rebuilding plan is restoring business confidence that the levee system will protect the city in future storms.
The Corps has pledged to rebuild levees to Category 3 levels, or 17 feet high, by the start of the next hurricane season, in June. Existing levees were built to 15 feet, but sections had settled to 12 or 13 feet, Nagin said.
The White House on Friday redirected $1.6 billion in untapped Katrina relief funds to levee reconstruction, plus $250 million to restore coastal buffers and wetlands.
But state officials have pushed a $14 billion plan to shore up the coast and marshlands, which absorb storm surges. Rebuilding levees to Category 5 levels could cost $2.5 billion, the Corps has estimated, and the state has requested as much as $20 billion to expand defenses and to include storm barrier and drainage systems.
New Orleans is facing a "critical point" as businesses decide whether to return, Nagin said. He said 80 percent of electricity and 60 percent of gas service have been restored to certain areas. About 150,000 people work in the city and about 75,000 reside overnight, compared with a pre-storm population of 480,000.