COVERED WOOD DRAWBRIDGE ON THE COLUMBIA RIVER HIGHWAY IN
CLATSOP COUNTY,OVER THE JOHN DAY RIVER EAST OF ASTORIA.
BUILT IN 1918. LIFT SPAN—40 FEET
John Day River Bridge
As a part of the improvement of the Columbia River Highway between Astoria and Svensen, a [bridge] was constructed over the John Day River about four miles east of Astoria.
The John Day River is a stream navigable to small boats, so it was necessary to provide a movable span of 40-foot clear opening. Owing to the unusually high price of steel it was decided to construct this bridge of wood. The movable span is of the single leaf bascule type operated by a windlass. Counter weights are employed to assist the movement of the span and in order to compensate for the variable pull required to lift the span at different phases of its movement, the counter weight cables operate over spiral drums in such manner that their pull is a maximum when the span is down, and is least when the span is raised, gradually changing between the two extremes. In order to guard against failure of the operator to close the gate on the side of the stream opposite the machinery, an automatic gate was constructed. It closes when the bridge starts to open and when the bridge closes it swings back out of the way automatically.
The bridge rests on concrete piers carried on piling, and besides the lift span there are two 90-foot covered wooden spans. The operating machinery is completely housed in by means of a tower.
The crossing was designed to carry 20-ton trucks and the covered spans have laminated wood floors with asphaltic wearing surface.