Three weeks after a canal break swamped hundreds of homes in Fernley, authorities are still puzzled over the cause of the rupture.
Betsy Rieke, area manager for the U.S. Bureau of Reclamation, said separate teams of outside experts and government personnel are investigating possible causes.
"We may never be able to pinpoint the specific cause," Rieke told The Associated Press. "The evidence in that specific area where the break occurred has washed away."
Officials have speculated about causes, including structural weaknesses in the century-old earthen irrigation canal, rodents such as gophers and muskrats that could have punched holes in it, and unusually heavy rain.
The flood occurred during a potent storm that also dumped up to 11 feet of snow in the nearby Sierra Nevada.
Rieke said her agency will try to come up with permanent solutions to prevent future breaks after the teams issue separate reports later this winter. The Jan. 5 rupture was the sixth in the canal's history.
"We need to be sure that the canal will be safe before water is again delivered into it," Rieke said. "We don't know yet when water can flow again in the canal."
The reclamation bureau owns the 32-mile canal that takes water from the Truckee River south to Fallon-area farmers, while the Truckee-Carson Irrigation District operates and maintains it under a contract with the bureau.
President Bush has declared the high-desert town 30 miles east of Reno a national disaster area, making federal relief available to those whose homes were inundated.
More than 300 individuals and families have registered for assistance so far through the Federal Emergency Management Agency, agency officials said Friday.
Crews have begun making permanent repairs to a 50-foot section of the canal that ruptured. Plans call for the breach to be refilled with new, stronger material, including cobbled rock.
Ernie Schank, president of the irrigation district, said he has talked with members of both investigative groups and doubts a cause for the breach will be determined.
"I think they'll probably say this could have been it. That's my assumption," he said.
Unlike the team of outside experts, the group of personnel from the reclamation bureau, irrigation district, U.S. Army Corps of Engineers and city of Fernley also will issue recommendations in its report.
Possible permanent solutions include lining the canal with cement, strengthening it with cobbled rock or widening its banks. Some also have suggested limiting where development can occur in the fast-growing city of about 20,000.
"There's been things done, contrary to news reports," Schank said. "In the last two years we've been able to get developers in four areas to double the width of the bank. We ourselves have put cobbled rock in the banks in several locations."
Two lawsuits filed on behalf of flood victims allege the irrigation district did not properly maintain the canal and failed to minimize damage once the breach occurred.
Schank has said the district reacted as quickly as possible after learning about the rupture.
The group of outside experts " three engineers from private consulting firms " was formed to ensure an independent examination of the breach, Rieke said.
"Everybody is going to want to be sure it's looked at in as objective a way as possible, including us," she said.