Engineer: Excavation caused Katrina collapse

NEW ORLEANS (AP) - An engineering expert has testified he believes excavation work performed by an Army Corps of Engineers contractor caused New Orleans' floodwalls to breach in two places during Hurricane Katrina.

Robert Bea, a retired University of California engineering professor, explained his position Monday during a trial of homeowners' claims against the corps and contractor Washington Group International Inc. Bea is an expert witness for the plaintiffs.

The corps and WGI have argued his analysis and conclusions are flawed. The corps contends Katrina's overwhelming surge overtopped floodwalls and caused breaches along the Inner Harbor Navigational Canal, commonly known to locals as the Industrial Canal.

Bea rejects the claim that storm surge was to blame for floods that covered the city's Lower 9th Ward and neighboring St. Bernard Parish.