Reservoir at Boundary Dam in Washington to be lowered for dam maintenance

Seattle City Light is preparing for a major maintenance project at Boundary Dam on the Pend Oreille River in northeast Washington that will require lowering the reservoir behind the dam in September, Seattle City Light reported.

This yearlong project involves the removal and rehabilitation of a 312-ton gate used to maintain the seven sluice gates located at the base of the dam. The maintenance gate is located on the outside of the dam at its base. It is used to seal the dam in order to remove a sluice gate for maintenance or work inside one of the sluices. Sluice gates can be opened or closed to control the amount of water in the reservoir.

It has been 27 years since the maintenance gate was last removed for its own maintenance, Seattle City Light reported.

Throughout the project, periodic disruptions or access restrictions will occur in the Forebay Recreation Area, including closures for the campground, picnic area and boat launch.

In preparation for removing the gate, a large concrete pad will be built at the Forebay Recreation Area in mid-August 2010, which will mean that a portion of the area will be closed to the public. Some activities in support of building the concrete pad are already under way and construction will continue through August.

Beginning Sept. 1, the reservoir will slowly be drawn down 40 feet to an elevation of 1,950 feet. This drawdown may last up to 11 days.

During the drawdown, the maintenance gate will be detached from the dam and floated to the nearby recreation area where it will be removed from the water. It will be placed on the concrete pad and housed for a year in the temporary building for the retrofit. Once the retrofit is completed in the fall of 2011, the reservoir will be drawn down again to return the gate to its permanent place on the dam.

With the reservoir drawdown, the namesake falls at Metaline Falls will reappear, along with portions of the reservoir not seen since 1982.

The low water condition will prevent access at all boat launch facilities on the Boundary reservoir, including the Boundary Forebay, Metaline Park and Campbell Park immediately below Box Canyon Dam from Sept. 9 through 16. The Boundary Dam campground and boat launch will be closed from Sept. 11 through 19 to accommodate the removal of the gate.

In other news, Seattle City Light recently received a $40,000 grant from the Salmon Recovery Funding Board to support salmon and steelhead habitat restoration along the lower Tolt River near Carnation, Wash., the utility reported.

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