Regional Water Quality Control Board, Region 1 (North Coast), Santa Rosa
Ridgewood Grade South Emergency Project
NOE - Notice of Exemption
California Department of Transportation
Following a period of heavy rains in early 2019, damage to a culvert on Route
101 at Postmile 36.41 in Mendocino County resulted in loss of an embankment and a portion of the shoulder in the southbound side of Route 101. Additionally, it was identified that a culvert drainage system was also damaged and undermining the highway at PM 37.48. Given the condition of the culvert and roadway, an unacceptable hazard to life and a significant loss of property exists and requires immediate corrective action to prevent or mitigate the loss or impairment of life, health, property, and essential public services. The existing, failing double barrel culverts at PM 36.41 consists of two 42-inch diameter by 112-foot long High-Density Polyethylene Pipes (HDPE). The plastic pipe culverts will be replaced with an 81-
inch wide by 59-inch high, 120-foot long steel arch pipe with steel armor. Additionally, the failing roadside drainage and warped wingwall at PM 36.41 will be replaced in kind. Work will be completed during the dry season. The channels are currently dry, so a clear water diversion will not be required. Caltrans will also replace the drainage system at PM 37.48, in-kind, using the jack and bore method. Caltrans will install appropriate, standard erosion control Best Management Practices. Work will also include roadway repair /restoration, traffic control, and revegetation in disturbed areas.