West Marin Drainage Rehabilitation Mitigated Negative Declaration

The County is proposing to conduct maintenance activities to rehabilitate existing road pass-through culverts and repair eroded roadside embankments (slip-outs). The proposed project would address culvert deficiencies using a variety of maintenance treatment types specific for each location. Culvert maintenance treatment types may include: extending culvert outfall pipes to avoid flanking or undermining; grouting or lining culvert interiors; paving culvert inverts; replacing damaged sections or failed pipes in-kind; installing larger diameter pipes where culverts are undersized; repairing existing inlet drop structures placing rock riprap at culvert inlets and/or outlets; constructing concrete headwalls; and improving fish passage.