A report further discussed the Truckee Canal, which flooded in Fernley in January 2008.
The Bureau of Reclamation’s Truckee Canal Safe Flow Determination Panel Report was released and received mixed reviews from the Truckee-Carson Irrigation District.
The report, comprised by a panel of experts, was created to determine risk levels for various water flows through the Truckee Canal after the Jan. 5, 2008, Fernley breach. The panel was convened March 27-29 to evaluate and provide guidance. The panelists toured the Truckee Canal on March 28.
TCID Project Manager Rusty Jardine said most recommendations were not surprising, but one assessment, though, is not in concert with those of TCID.
“Our assessment of risk associated with operation of the canal certainly doesn’t conform with Reclamation’s (BOR) view of risk,” he said. “It’s like they are saying in order to completely eliminate risk in operation, then you get it down to 150 cfs (cubic-feet per second) flow or something like that (as an example).”
The three panelists, Robert Davis, Manager, DEC Oversight and Value Program Office, and William Engemoen, Geotechnical Engineer/Risk Advisory Team, both of Denver, and Christopher Keith, mechanical engineer, of Boise, Idaho, relayed numerous recommendations to TCID, which operates the canal.
“We have safely operated the canal for all these many years now at this existing flow regime, and we think we can do that indefinitely,” Jardine said. “I think we were successful in eliminating a whole bunch of places that could, at some point in the future, have constituted what Reclamation refers to as potential failure modes.”
The panel’s report stated the “failure resulted in the flooding of several hundred homes and the temporary discontinuation of operations of the Canal.
“Upon inspection, numerous rodent burrows along much of the canal embankment, as well as a large number of trees and other woody vegetation growing near or on the canal, were found. A forensic evaluation found that the most likely cause for the failure was that the high water flows of Jan. 4 and 5 (2008) had surged into the animal burrows and opened seepage paths through the embankment, which led to a collapse.”
The canal was designed to hold 900 cfs, but flows were reduced to 150 cfs after the breach and were increased to 350 cfs for several years after a federal court ruling. According to the report, the canal has failed nine times in its history.
The panel also acknowledged “considerable effort invested by BOR’s Lahontan Basin Area Office, TCID and their representatives that has brought the Truckee Canal to its current state. Some measures taken since the 2008 canal breach have made progress in reducing or mitigating the risk of another canal failure (breach). Others have served to hold the risk of failure from neither increasing nor decreasing.”
The report, though, said some practices may lead to an increase in risk of some internal erosion failures, such as over excavating the invert of the canal during sediment removal operations, possibly removing beneficial natural lining.
“Barring the construction and implementation of a comprehensive corrective action alternative improving the physical conditions of the canal, the operation of the canal under current conditions continues to present a risk of failure,” the report said. “Even assuming that ongoing actions of improving monitoring and physical conditions along the canal continue, the panel would caution that a failure may still be possible at the current restricted level of flow and stage restrictions.”
Recommendations from the report include the following:
An evaluation of acceptable long-term operational restriction for the Truckee Canal. This includes continued discussions with LBAO and the city of Fernley.
Conduct a more extensive analysis of cross sections along the Fernley Reach to determine which stretches pose a higher risk.
Target future corrective actions at those areas that pose the greatest risk.
Continue ongoing maintenance and improvement.
Re-establish stage flow targets to better match an unchecked flow of 350 cfs with the canal in a well-maintained condition.
Minimize the routine check up of water surface elevations.
Increase efforts to control vegetation in the canal.
Eliminate or scale back the amount of excavation within the canal prism.
Minimize icing in the canal.
Annually re-evaluate the decision to continue operation at 350.
Since the breach, TCID has provided continuous maintenance on the canal. The report said given TCID’s operating budget and potential costs for “total corrective action,” it may take years for a permanent fix to the canal.
“In the Panel’s view, a continued prolonging of the 350 (cfs) restriction for an indefinite period of time will not benefit the TCID, Reclamation, or the public at risk in terms of lessening the likelihood of another failure,” the report said. “Given the original 2008 DEC (Design, Estimating and Construction) Report’s support for corrective actions and the view that the 350 (cfs) restriction would only be in place for one to five years, as well as the results of the risk assessments performed by the TSC (Technical Service Center) indicating concern about flows over 150 (cfs), there is documentation in place that suggests that additional restrictive measures to reduce the risk of canal breach would be advisable.
“Furthermore, the Panel fully supports the DEC Team’s contention that permanent structural modifications to the embankments are needed even if the canal is not returned to its full capacity and/or operation.”