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.
One of the most serious objections raised against covered wooden bridges
is the lack of light. This was overcome in this case, as in other wooden
bridges on primary roads designed by this Department, by whitewashing
the interior and the addition of open windows at panel points. These are
provided with returns, and with the asphaltic wearing surface on the
floors of such bridges prevent moisture coming in contact with the
structural timbers of the bridge.
This bridge was built by the Portland Bridge Company and the total cost
will be about $25,000.00. The payments on the bridge to November 30,
1918, amounted to $21,051.52. Mr. Leigh M. Huggins was resident engineer
in charge of construction.