EWEB updated on hydro projects safety

EUGENE: Eugene Water & Electric Board commissioners received a dam safety update for their three hydroelectric plants this month. Part of their October 1st meeting detailed the utility’s efforts to comply with the Federal Energy Regulatory Commission’s (FERC) regulations for facilities they’ve classified as having a high or significant hazard potential.

On FERC’s list are the Carme-Smith, Leaburg, and Walterville projects. The first is currently generating electricity, while the canal powering the Leaburg project has been out of service since 2018. The one leading to Walterville’s generator was dewatered in February of this year.

Three active sinkholes discovered in the Trail Bridge Reservoir have been studied since they were detected in 2021. While it appears the sinkholes aren’t likely to undermine the structural integrity of the Camen project’s Trailbridge Dam, utility staff reported to the utility board that FERC requires a risk assessment before a proposed trap and haul facility for salmon can be constructed.

EWEB has awarded a ten-year, ten-million-dollar contract to Cornforth Consultants to provide a dam safety report in response to feedback from FERC and fisheries agencies regarding improvement projects at Carmen Smith. Some things up for review include modifying the spillway and gates for downstream fish passage, building the trap and haul facility next to the powerhouse, surface regrading upstream of the emergency spillway, and installing fish habitat structures in the reservoirs.

Following EWEB’s January 2023 recommendation to decommission the Leaburg project, several ongoing safety issues have been investigated, including sinkholes in the levee’s embankment, soil instability, and excessive seepage. Since water is no longer diverted from the McKenzie River through the canal, it has been used for stormwater runoff primarily from Cogswell and Johnson creeks. To help drainage, a turbine was removed from the Leaburg powerplant to increase outflow rates during storm events.

After EWEB drained the canal at Walterville, it has been working on a repair plan around the powerplant’s forebay. In addition, several other dam safety investigations are underway regarding the stability of the canal’s embankments and concrete structures during seismic events.

In addition, erosion in the vicinity of the siphon spillway has been repaired. Alternatives for longer-term changes in spillway operations are being developed based on a subsurface drilling plan in the forebay area and upstream areas with high-hazard canal embankments.

This fall, a public outreach information brochure will be sent to property owners adjacent to EWEB’s hydroelectric projects and to areas within the inundation zones resulting from a canal or dam breach.

No action was taken at the board’s October 1st meeting. Ward 4 and 5 commissioner John Brown said he hoped a favorable result from the sinkhole investigation at Trailbridge would allow EWEB’s trap and haul project to continue. Board vice president John Barofsky echoed that, commenting that “it sounds like half of FREC is talking to the other half.”