News Release
| Release Number: | 97-103 |
| Dated: | 9/24/1997 |
| Contact: | Heidi Y. Helwig, 503-808-4510 |
Portland, Ore. -- The U.S. Army Corps of Engineers will complete an underwater investigation today at Bonneville Lock and Dam to determine the condition of the concrete in a number of the dam's spillway bays. Divers have found some damage to the concrete. The damage is limited and does not affect the safe operation of the dam itself, according to the Corps' dam safety coordinator John Sager.
During a maintenance inspection earlier this week, divers confirmed wearing of the concrete surfaces in the spillway. Several areas of excessive wearing was observed, the most significant in bay 14, located near the middle of the spillway. The area affected by erosion is about 10 feet by 6 feet by 8 feet deep and occurs in the concrete spillway slab. The work was coordinated with regional fisheries and resource agencies, including the National Marine Fisheries Service (NMFS) and the Bonneville Power Administration, and will be completed by tomorrow.
In the next two weeks, the Corps will perform hydroacoustical surveys of the area, which will provide more detailed and technical information about the extent of the damage so that technical experts can develop a repair plan. This level of information is not available through a dive inspection. This activity will require a short interruption of the adult attraction water, but the fish ladders will remain in operation at all times.
Temporary repairs to the spillway bays, if determined to be necessary, will begin later this fall during the in-water work period, which normally begins Dec. 1 and runs through Feb. 28.
Similar problems were repaired in 1954. Bonneville Dam's spillway bays have been monitored since. Hydroacoustics surveys taken in September 1996 alerted Corps experts that some areas of the spillway bays were again experiencing differing degrees of erosion. The Corps planned at that time to conduct an underwater inspection to confirm the extent of damages, but because of continued high flows, this week was the first opportunity for that inspection to occur. Also, it is believed that the unusually high flows last spring most likely exacerbated any existing erosion areas, Sager said.