News Release
| Release Number: | 04-193 |
| Dated: | 10/14/2004 |
| Contact: | Mike McAleer, 503-808-4510 |
Portland, Ore.— The U. S. Army Corps of Engineers will accelerate drawdown of Fern Ridge Lake because of the increase in sediment exiting from the dam’s internal drainage system. Fern Ridge Dam, located on the Long Tom River about 12 miles west of Eugene, Ore., was completed in 1941.
During the past several weeks the Corps has noticed a significant increase in sediment exiting from a drain on the downstream face of the dam, said Mark Dasso, the Corps’ project manager. Sediment deposits increased ten fold, from 0.2 pounds to 2.2 pounds per day during September.
“We have already started the normal drawdown of the reservoir for winter flood damage reduction. As a precautionary measure and to ensure the structural integrity of the dam, we are accelerating our drawdown schedule,” Dasso said. The lake will reach its normal fall flood damage reduction level, known as minimum pool, in about 10 days, shaving about 20 days off the schedule, Dasso added.
At noon on Friday, the Corps will begin increasing water releases by 200 cubic feet per second (cfs) and will continue increasing the releases by 200 cfs each hour with the goal of reaching a release of 3,000 cfs by midnight Friday As a result, within the next 10 days, water levels behind Fern Ridge Dam will drop from about 368.5 feet to 353 feet as water levels immediately downstream from the dam rise from about 3.5 feet to 7 feet.
As the increased water travels downstream, the rise will be less noticeable. For instance, at Monroe, about 17 miles downstream from Fern Ridge Dam, water levels will rise from about 5.5 feet to 7 feet. Corps personnel stationed at the Fern Ridge office have alerted as many boaters and irrigators as possible about this change.
The concern about the drain should not affect normal operation of the dam during the flood damage reduction season but it is not known at this time whether these developments will impact filling the reservoir next season. In November, a team comprised of Corps experts from around the nation, including those well versed in seepage and erosion issues, will convene to study the problem at Fern Ridge
Until then, the Corps will continue its daily monitoring and sampling efforts. As more information becomes available on this issue, it will be posted on the Corps' web site at https://www.nwp.usace.army.mil/issues/fernridge/cms/.
The first indication of a possible problem with the dam’s internal drain system was in February 2003 when field personnel noticed depressions on the face of the dam. The Corps has closely monitored the dam since then.