Cedar Cliff Dam

Phase I work began at Cedar Cliff Lake in 2019; based on current conditions, work including increasing the existing spillway width will run into 2024.

By Dave Russell

 

Duke Energy has pushed the date for the completion of the Cedar Cliff Dam refurbishing project out about two years.

The construction to refurbish the dam that forms Cedar Cliff Lake in the Canada community began in 2019 and now is expected to be completed in 2024.

“Based on current conditions, the project construction and lake drawdown will extend into 2022,” Duke spokeswoman Kim Crawford said in an interview in May.

“Based on current projections, the lake drawdown and associated construction work should be completed by the fall of 2024,” Duke Government and Community Relations Manager Lisa Leatherman said in an August missive to area property owners.

“We communicated an updated completion date in late August to lake property owners,” Crawford said last Thursday.

Duke mailed a postcard to property owners the week of Aug. 20, and the Federal Energy Regulatory Commission posted a legal ad regarding the extensions of the lake drawdown in The Sylva Herald on Sept. 2.

“Our original estimate for the drawdown period was optimistic regarding the duration of the auxiliary spillway components of the project and was not based on contractor estimates,” Crawford said. “There was simply not enough information at that time, and the contractor for the primary construction phase was not yet on board.

“Additionally, delays due to COVID-19, necessary precursor site work, dam safety vibration limitations when blasting, and unanticipated restrictions on production required to meet turbidity limits resulted in individual and cumulative impacts to the original construction schedule. We regret the inconvenience to lake property owners and lake users while we complete this important dam safety work.”

FERC required Duke to make modifications to ensure the safety of the dam during extreme high-water conditions, Crawford said.

The spillway upgrade project includes deepening and widening the existing auxiliary spillway channel and replacing the two fuseplugs with a fusegate system, according to the engineering report.

A fuseplug is a collapsible dam installed on spillways in dams to increase a dam’s capacity.

Fusegates provide a controlled release of water during large floods. In large flood conditions they topple forward, allowing a controlled flow of water.

The existing spillway width will increase from 95 feet to 145 feet, and the channel bottom will be lowered by 15 feet on average.

That phase was completed and Phase II, the primary phase of construction, began in January of this year.

The work will include widening the auxiliary spillway, primarily by blasting, installing a new fusegate system, and refurbishing the crest of the dam including adding a concrete wall, Crawford said 

Here is the text of the postcard Duke sent property owners around Cedar Cliff Lake:

“As your neighbor, we want to keep you informed about activities underway at Cedar Cliff Dam. The most recent work involves safety modifications in accordance with Federal Energy Regulatory Commission requirements.

“Site development work began in late fall 2019 when Cedar Cliff Lake was lowered approximately 40 feet below full pond. This involved refurbishing the primary spillway (hoist, gate and bridge), establishing laydown areas, improving access roads, constructing a retaining wall above the spillway and drilling vertical rock anchors along the left abutment of the dam to reinforce it prior to blasting.

“Earlier this year, the main construction work began, including widening the auxiliary spillway  (primarily by blasting), barging and placement of rock material in the lake, installing a new fuse gate system and installing a new concrete wall along the crest of the dam.

“Based on current projections, the lake drawdown and associated construction work should be completed by the fall of 2024. Several factors have impacted the initial two-year lake drawdown estimate, including delays receiving regulatory approvals, production delays due to COVID-19 and the need to implement additional measures to ensure compliance with environmental permit requirements.

“We recognize construction activities have been inconvenient to lake residents and appreciate your patience as this important work continues. If you have questions, please feel free to contact me at lisa.leatherman@duke-energy.com.”