FERNLEY — Burrowing rodents caused a century-old irrigation canal to fail and flood Fernley in January, scientific experts concluded in a report for the U.S. Bureau of Reclamation.
Muskrats, beavers, gophers and other rodents dug holes as deep as 25 feet into the earthen canal embankment over the years, the experts found.
The report was made public Thursday night at a community meeting that drew about 200 people to the high school gymnasium.
Water burst through a 50-foot breach in the weakened structure at 4 a.m. on Jan. 5 and flooded hundreds of homes in the rural Northern Nevada town. As many as 600 homes were damaged by floodwater, which reached 8 feet deep in some places, and the area was declared a federal and state disaster area.
“They believe it was the rodent critters that caused the break of the canal,” said Jeffrey McCracken, public affairs director of the bureau’s Mid-Pacific Region in Sacramento, Calif.
The bureau owns the 32-mile canal that takes water from the Truckee River south to Fallon-area farmers.
“Obviously, rodents are a problem here. That is what the evaluation team felt was the cause,” he said in an interview before the meeting.
Nearly 2 inches of rain fell the day before in the area that averages only about 5 inches of precipitation a year. But the water flow at the time of the breach was at or near the allowable level of 750 cubic square feet per second, the report states.
“This was determined not to be a flooding issue,” McCracken said. “The flows were within the capacity of the canal.”
Investigators considered and ruled out other possible causes for the canal failure, including erosion, seismic activity, embankment instability and sabotage.
An accompanying evaluation determined that as soon as additional flow measuring gauges are installed, it would be safe to resume diverting a small amount of water from the Truckee River into the canal.
The experts determined about half of the maximum water flows can return to the canal, but only if corrective and safety steps are taken.
Returning the canal to its full operation will require “significant repair and/or modification” of the canal, bureau officials said. Federal funding would be needed for the project that probably would carry a price tag of tens of millions if not hundreds of millions of dollars, they said.
Ernie Schank, president of the Truckee-Carson Irrigation District, which operates and maintains the canal under a contract with the bureau, said the findings were expected. He said the district has been working to install new gauges and should be ready for some water to begin flowing today.
A lawyer representing owners of about 80 flooded homes who have filed a class-action lawsuit against the irrigation district in Lyon County District Court in Yerington have asked a federal court to order more testing before reopening the canal.
Fernley, about 25 miles east of Reno, was once a rural agricultural town that is now a growing bedroom community of about 20,000 residents.
In addition to filling an unspecified number of rodent holes, the team recommended numerous actions to ensure the safety of the canal, including improving canal facilities and developing emergency response plans.
“Considering the canal has been in operation for 102 years, one would expect that when you evaluate and review it as extensively as we’ve done that they were going to find this and they are going to have to fix these things,” McCracken said.
Two lawsuits filed on behalf of Fernley flood victims alleged the district did not properly maintain the canal and failed to minimize damage once the breach occurred. Several citizens repeated those claims at the public meeting Thursday night and a lawyer representing some residents said the bureau itself had raised concerns about rodent holes and vegetation compromising the canal’s structure in a 2005 annual review.
“It was known this was going to occur,” said Robert Maddox, the lawyer who criticized the bureau for refusing to allow some outside experts to drill into the embankments to test the stability.
Bureau officials defended the inspection program.
“We think the inspections were done as required,” McCracken said, adding that the bureau is responsible for signing off on inspections.
“There’s nothing punitive in here,” he said about the report.
The investigative team included government and private geophysicists, hydrologists, engineers and geologists.
They determined that if the new measuring gauges are put in place, it would be safe to resume flows of 150 cubic square feet per second, about one-fifth the maximum level. (One cfs is equal to about 7.5 gallons per second).
They outlined various requirements to boost the flow to 250 cfs, including a better plan to monitor flows, a plan to improve existing facilities and the development of an emergency plan to respond to any breaks.
Another boost to 350 cfs would be allowed if, among other things, the irrigation district implements a “rodent plan” that identifies and fills any rodent burrow more than 2 feet deep throughout the 11-mile stretch of the canal through the Fernley area.
“That is as far as you can go until you get a lot of money from Congress to fix the entire canal,” McCracken said.
During a normal water year, the irrigation district delivers 215,000 acre feet of water primarily for agricultural use to about 2,500 users.
McCracken said that if water flows go as planned, water users should see no major impact for at least a year.