Dam operators began lowering the water level in Foster
Reservoir Wednesday, July 16, the Portland District, U.S. Army Corps of Engineers announced.
The drainage is expected to last 11 days and will take the lake level to winter pool. It was prompted by an inspection that indicated two of the dam’s four spillway gates are not working properly, Corps officials said.
“While the water is down, dam safety engineers will investigate and maintain the four spillway gates that control the reservoir’s level to ensure they will perform their intended purpose,” a statement from the Corps said. The routine inspection of two of the four gates gave engineers reason to doubt that the gates would work correctly during a moderate storm event with a full reservoir, the Corps statement said.
Engineers expect the lowering to take 11 days, at which time the reservoir
will be held at elevation 613 feet until the remaining two gates are
inspected, and all four gates are lubricated and deemed to be structurally
and functionally capable of controlling water at the dam. The South Santiam
River downstream of the dam should see minimal impact; flows are expected to
be at about 1,400 cubic feet per second.
“Let me be very clear here, the dam is safe and not at risk of failure,” said
Don Chambers, chief of the agency’s Engineering and Construction Division and
dam safety officer. “We do have some concerns about the ability to safely
operate these gates, so we are taking this step to ensure we meet our primary
mandate – protection of public safety.”
On Friday, engineers will inspect the spillway gates to begin the process of
determining if and under what conditions the gates can be operated. Following
that, engineers will lay out their plan for fixing any deficiencies.
Maintenance crews will lubricate all the working parts as part of this
process.
The spillway gates control the release of water from behind the dam. The
gates are used at various times of the year, but are critical to the safe
release of water during and after a storm event.
Foster Reservoir is a popular summer-time recreation spot, attracting nearly
300,000 visitors between June and August, and the Corps expects there to be
impacts on those wanting to take advantage of the amenities on and around the
facility. However, the Sunnyside boat ramp extends to the reservoir, even at
the lower elevation.