Clark - NE Allworth Rd Culvert

The NE Allworth Road Culvert project entails replacing the undersized, heavily corroded, and failing two-culvert system, with a new single structure spanning Rock Creek in rural northeast Clark County near the City of Battle Ground. This culvert system is identified by Washington Department of Fish and Wildlife as a fish passage barrier along Rock Creek, a salmonid bearing creek. The existing, deteriorating culverts are corrugated metal pipe (CMP) with diameters of 60 inches and 36 inches, respectively. Both culvert bottoms are heavily corroded and need replacement. The roadway embankment is showing signs of severe scour and ground movement on the roadway surface, where two transverse depressions are visible to the naked eye and easily felt by vehicular traffic. Proposed improvements include: (1) replacing the current deteriorating CMP’s with a new structure spanning the creek meeting the 100-year flood hydrologic conditions and fish passage requirements, (2) rebuilding/restoring the roadway surface, (3) install new guardrail which meets current standards. Further hydraulic engineering/study is needed to determine which of two options (bridge replacement or box culvert) will best fit the project needs. This prospectus reflects the more conservative bridge replacement option.