News Release
| Release Number: | 99-084 |
| Dated: | 9/24/1999 |
| Contact: | Matt Rabe, 503-808-4510 |
Portland, Ore.--Engineers will perform a routine follow-on inspection of the Fall Creek Dam next week to see how concrete repairs completed last year to the dam's stilling basin are holding up.
Dam safety inspectors from the U.S. Army Corps of Engineers will visit the dam Sept. 27 and Sept. 28 to gauge the condition of the repairs that replaced some damaged concrete. Fall Creek Dam is located about 25 miles southeast of Eugene, Ore.
"We expect last year's repair work to be in good shape, but we owe it to members of the community and to ourselves to know, without a doubt, that the repair work makes the basin as good as new," said Carolyn Flaherty, Corps dam safety engineer.
Water releases from the reservoir into Fall Creek must be temporarily reduced to accomplish this inspection.
Beginning at midnight Sept. 26, the Corps will gradually reduce water releases from the reservoir from the current 720 cubic feet per second to about 220 cfs.
As a result of the reduced water releases, downstream water users will see about a 1.3 foot drop as measured just below the dam and a 0.3 foot drop as measured at Jasper gauge, the primary downstream control point for Fall Creek Dam. To minimize impacts to the shoreline, the Corps will gradually decrease flows by 200 cfs every other hour beginning at midnight.
The flow reduction is needed so engineers can install a bulkhead on the downstream side of the stilling basin just downstream of the dam, pump the water out and inspect the basin and the regulating outlet tunnels on the dam. The work will be done Sept. 27 and Sept. 28. At midnight on Sept. 28, the Corps will gradually increase the releases to 700 cfs.
The stilling basin is equipped with baffles, devices that are designed to "still" the water as it flows through the dam's regulating outlets; erosion is the most common sign of wear and tear in the stilling basin. During previous routine inspections of Fall Creek Dam, which are conducted every five years, Corps dam safety engineers noticed worse-than-usual erosion in the stilling basin. Last year, the Corps hired a contractor to remove some of the old, eroding concrete and replace it with stronger concrete. During the inspection, dam safety engineers will look specifically at this repair work.
The integrity of the repair work is important since the dam is one of 13 Corps facilities in the Willamette Valley that helps control the effects of flooding.
Earlier this month, Corps reservoir regulators began lowering the levels of the 13 lakes in the Willamette Valley, including Fall Creek. By Nov. 30, the Corps must have the lake levels lowered to their flood damage reduction levels, ready to hold fall and winter rain and runoff; the dams temporarily hold back the water during storms until it is safe to release the water into downstream creeks and rivers.
Since their construction, Corps flood damage reduction projects in Oregon have prevented more than $20 billion in flood damages.