Grand Coulee Dam Airport, Electric City, WA (3W7)
Correctly identified first by Jeff Davis.

Perched on the edge of Banks Lake just downstream from the massive Grand Coulee Dam complex in central Washington, Grand Coulee Dam Airport enjoys one of the most spectacular airport settings in a region rich with spectacular airports. The approach or departure down the lake, over the tranquil waters and below the canyon walls, is a real joy. There's not much happening at the airport, but the facility is in great shape, and there's even a courtesy car for a jaunt into town. All that and eye-popping scenery - who could ask for more?