Page:Final Report - The Columbia River Interstate Bridge.pdf/45

 For moving the spans from the launching ways to the piers. four barges were used. on which fulsework of timbers was built up to a proper height so that with a span on the barges the shoe of the span would be a few inches above the tops of the piers. When ready for moving. water was pumped into the seows supporting the fnlsework and they were ﬂoated underneath the span between the launching ways. Blocking was then placed between the falsework on the scows and the under part of the span so as to provide proper bearing, and the water pumped out of the scows, so lifting the span 011' the ways. The span ﬂoating on the barges was then towed out to position over the piers by

steamboats and tugs and water was pumped into the scows, lowering them and bringing the span to rest on the piers, and finally entirely releasing the seows, which were then taken back for another span.

The erection of the towers and other portions of the structure were by methods not unusual in steel erection, except that for the Oregon and Columbia Slough spans the material was all ﬂoated near to position on scows and erected from them. The