Upstream passage of migratory fish through culverts long has been a critical fisheries problem in Washington. Many small streams which can be crossed with a culvert rather than a more expensive bridge, account for a significant portion of the state's salmon producing potential. Some species of salmon, particularly silver and chum, seek the smaller streams and tributaries for spawning. Thus, each stream is important for its contribution to the gross production. In past years many of these small streams have been blocked to salmon migration and culverts are one of the principal blocks. Poorly placed or designed culverts present a problem, the correction of which is vital to the maintenance of present spawning areas and the rehabilitation of areas no longer accessible because of past culvert failure.