In 1990 the Water Board listed the Napa River for excess sedimentation. A draft TMDL for sedimentation was released in 1995, which identified roads as a significant source of sediment. Roads have been identified as a major sediment source in Carneros and Sulphur Creeks, tributaries to the Napa River. The proposed project is aimed at erosion control and sediment reduction to streams through the treatment of high and high-moderate treatment priority sites and hydrologically connected road reaches. Treatments include stream crossing culvert installations, fillslope stabilization and a variety of road surface treatments. By applying the proposed treatments, approximately 21,944 yds3 of sediment would be prevented from being delivered to streams. Direct benefits include: turbidity reduction, sediment delivery reduction, improved salmonid habitat, improved water quality, and progress toward meeting sediment reduction goals defined by the draft TMDL.
Roads have been identified as a major sediment source in Carneros and Sulphur Creeks. The proposed project is aimed at erosion control and sediment reduction to streams through the treatment of high and high-moderate treatment priority sites and hydrologically connected road reaches. Treatments include stream crossing culvert installations, fillslope stabilization and a variety of road surface treatments. Proposed erosion control treatments follow agency accepted guidelines in the California's Salmonid Stream Habitat Restoration Manual (CDFG, 2003). Pacific Watershed Associates (PWA), the subcontractor involved in the original road assessment and the proposed project design, has designed and implemented road treatments on thousands of miles of road using these guidelines. In addition, PWA has conducted many demonstration workshops for watershed groups and public agencies. PWA workshops provide information about proper road design and common road-related erosion problems.
Erosion control and erosion prevention treatments include: 1) Stream crossing upgrading stream crossing upgrading for the 100 year storm critical dip installation to prevent stream diversion culvert trash rack installation to prevent culvert plugging culvert downspouts to prevent fillslope erosion 2) Fillslope stabilization landslide excavation fillslope armoring to protect fillslopes from erosion 3) Road surface/fine sediment treatments to improve road surface and ditch drainage rolling dip and ditch relief culvert installation rock road surface outsloping road berm removal ditch maintenance The proposed project includes 2 demonstration workshops designed to provide landowners with the knowledge to identify road-related erosion problems, proper road design and how to be involved with future demonstration projects. All road treatments are to be implemented and workshops conducted between April and October 2007 or 2008, depending on when funds are secured. The project benefits to water quality and benfecial uses result from the reduction of sediment delivery to streams. Specific benefits from the reduction of sediment to streams include: Turbidity reduction Sediment delivery reduction Improved salmonid habitat Improved water quality Improved domestic water supply Addresses TMDL sediment reduction targets Temperature reduction
