Repairs to New Orleans' levees may not be enough to protect people moving back to the devastated city if another hurricane comes before the tropical storm season ends this month, engineers said Wednesday.

Dozens of breaches continue to mar the city's levee system, including a large seep at the Industrial Canal last week, according to engineering experts who have examined the floodwalls.

Repairs have gotten better in recent days, the experts told a Senate panel investigating floodwall failures after Hurricane Katrina (search). But the initial rebuilding process was done with little or no engineering guidance and perhaps substandard materials, they said.

"Short term, without a storm, they are probably adequately safe," said Dr. Peter Nicholson, a University of Hawaii engineering professor, representing the American Society of Civil Engineers (search). "Certainly with a large storm, as we are not yet out of hurricane season, and certainly for next hurricane season, there is significant risk."

At the Industrial Canal levee, which abuts New Orleans' obliterated Ninth Ward, repairs to breaches "were not adequate for a high-water incidence — for instance, another hurricane storm surge with the storm season that isn't yet behind us, or even a very high tide," said Raymond B. Seed. Seed, a University of California at Berkeley engineering professor, participated in a National Science Foundation study investigating the levee failures.

The large seep at that levee, which occurred Oct. 24, "was not entirely unexpected," Seed told the panel.

However, he said, deeper walls "that will be far more stable than they were before" have been dug in at least some areas since the NSF first examined the levees.

"I don't think there is a long-term risk to the city of New Orleans," Seed said.

The findings highlighted what Sen. Susan Collins (search), R-Maine, who chaired the panel, called troubling concerns about whether the repairs have been insufficient.

"These rebuilt levees may be at risk of failing in another storm, a disturbing finding that raises questions about the safety of the city's returning residents," Collins said. She heads the Senate Homeland Security committee, which was holding a hearing on why New Orleans' floodwalls failed after Katrina hit on Aug. 29.

Sen. Joe Lieberman (search) of Connecticut, top Democrat on the panel, said reconstruction efforts were done, "we all understand, in haste and in very urgent circumstances." But he echoed Seed's questions about whether the levees could now "protect the city of New Orleans from high tides, let alone another hurricane."

Two representatives for the Army Corps of Engineers (search), which is in charge of the levee reconstruction, did not immediately return calls for comment Wednesday. But Dr. Paul F. Mlakar, a senior scientist at the Army Research and Development Center (search), warned lawmakers against making any conclusions about Katrina's failures before the Corps completes a review.

"The results of our study will provide a better indication of the extent to which the remaining system can be expected to reduce the risk of future storm damage," Mlakar said.

Seed described what he called "variable levels of cooperation" from the Corps, depending on personal contact, geographic location and even what day of the week. He said the NSF's team of engineers and the Corps spent a week's worth of back-and-forth communication "in which the responses, in our view, were insufficient and sometimes misdirected."

"It became clear to us that they were struggling to get the right kind of people put in charge of the projects to get the concerns addressed," Seed said.

The Corps has since corrected that gap amid what Seed called tremendous logistical difficulties. "The Corps of Engineers is working very hard at all this," he said. "They're also stretched very thin."

The Senate hearing also examined the NSF's report showing that the levees may not have been designed to protect a major city. Moreover, engineers who designed the levees did not fully consider the porousness of the Louisiana soil or make other calculations that would have pointed to the need for stronger floodwalls, the study shows.