SCH Number 2020060620

Project Info

Title

Upper Drainages Erosion Control Improvements

Description

The project would replace or modify drainage systems that are deteriorated and/or undersized and that are plugging, overtopping, or flooding and thereby causing erosion. The main component of these drainage systems is the cross-culvert, which is a pipe or other opening that runs under the road from one side to the other. In some locations, there are other culverts that run longitudinally off the highway shoulder, either as a subsurface pipe or a surface ditch. A few locations have downdrains, which are usually black corrugated plastic pipes that lay on the surface of a slope, directing runoff downhill. Larger culverts usually include a headwall (a short concrete wall securing the opening) at the entrance and occasionally also at the exit, although runoff enters most of the systems via an inlet grate level with the surface of the road. The project would plug and fill the old pipe culverts; install new, larger pipe culverts; place rock slope protection at outlets where needed; replace substandard inlets; and add minor paving where open ground is causing excessive sediment in the drainage system. An existing retaining wall would be rebuilt and lengthened. The Skyline-to-the-Sea Trail would be repaired where erosion has created a slipout. Guardrail would be repaired where necessary.

2 documents in project