The present route of US 2 in Tumwater Canyon is the old GN right of way - it stays on the east bank of the river all the way through the canyon. The bridge you see carried the penstock from the dam about a mile upriver across the river to the powerhouse. The powerhouse was just south of the bridge on the east side of the river. The penstock was entirely on the west side until that point. The powerhouse produced power for the electrified portion of the railroad. There is still considerable evidence of the penstock and a nice walk along the route leads you to the collapsed (or blown-in) tunnel that also served the penstock, not the tracks.