Jefferson County Public Works employees are busily armoring and reinforcing the levees along the Snake River in anticipation of a big runoff.
At a May 8 meeting, Commissioner Scott Hancock and Public Works Administrator Dave Walrath discussed recent meetings with the Idaho Department of Emergency Management and the U.S. Army Corps of Engineers, and said that they have identified several weak points.
The number one priority, Walrath explained, was near the Farmer’s Friend and Enterprise canals, where the river could erode away the levee, sending tremendous amounts of water down the canals. The county was working on armoring that levee May 8 and May 9.
“The real threat with this is if it were to bust though that, it would be flowing into the canal uncontrolled,” Walrath said.
Hancock said that would spell trouble for the Ririe area and cost millions in damages.
Chairman Brian Farnsworth said that the Enterprise and the Farmer’s Friend canals were considering locking the county off of their bridges during the construction of the Great Feeder Canal headgate last year.
He questioned whether they should be responsible for helping pay to armor the levee at their canals.
Hancock said that state Emergency Management North East Field Manager Mike Clements said the county could use emergency mitigation money to pay for it.
Farnsworth said that the canal companies should see that the county is there to help them.
“I want the canal companies to understand that we’re not the enemy, like they treated us last year,” he said.
The second priority is near the Butte Market Lake Canal in Roberts, which saw a failure in 1997. The county has stockpiled riprap rock in anticipation of quick repairs.
“It’s a battle when the river’s like this,” Walrath said.
Farnsworth said that in 1997 he saw dump trucks dropping boulders into an eddy where the river met the Butte Market Lake.
Unfortunately the Henry’s Fork and the South Fork will hit their peak runoff at about the same time, near Memorial Day, which poses a risk to the Roberts area. Walrath said that he believed the water rate could be slowed through accumulating storage at Palisades to avoid a big risk to the levees.
Even though the Palisades Reservoir was drained to 8 percent, the Snake River may peak at around 26,000 cubic feet per second (cfs) near Heise. As of May 9, it was running at 20,000 cfs.
The U.S. Bureau of Reclamation has been carefully monitoring and managing Palisades and Jackson Reservoirs for flood control. Farnsworth asked if they could begin filling Palisades now to slow the current and lessen damage.
Walrath said that when they begin to slow the flow of water, the reservoir would fill up quickly, within 20 days.
Hancock added that there is still enough water in the high elevation snowpacks to fill Palisades three times.
Farnsworth asked if the Army Corps was doing anything to help. Hancock said they were doing nothing yet, though they were happy to sign permits for the county to reinforce the levees.
Walrath said that the Army Corps won’t do anything until the river reaches 23,000 cfs, which is their “action level.” The state is petitioning to lower the amount to unlock federal aid.
Hancock said that this is particularly important for areas further downstream, like Blackfoot, where damage and flooding occurs at less that 20,000 cfs.
He said that the county’s “Ace in the hole” to prevent flooding and levee failures, might be the Great Feeder Canal Company. The large canal can divert up to 9,000 cfs.