Post Project Appraisal of Riparian, Wetland, and Aquatic Habitat Restoration at Best Slough, Beale Air Force Base, Marysville, CA

Best Slough flows through Beale Air Force Base and used to come into contact with groundwater contaminated by trichloroethene (TCE) at Site 17 during low flow periods when it was a gaining stream. An interim remedial action was developed for Site 17 to halt further migration of the contaminated groundwater plume by surrounding it with a slurry wall and establishing a phytoremediation system on top of the site within the slurry wall. The portion of Best Slough in contact with the contaminated groundwater plume was realigned upgradient of the plume with more natural channel morphology and riparian vegetation as well as sufficient hydraulic capacity and channel stability to protect the remedial features on the site. Channel banks were designed with terraced slopes to provide additional acreage for riparian vegetation habitat. Side-channel islands were included in the channel design to provide isolated riparian habitat for waterfowl as well as for aquatic reptiles and amphibians. A complex of deep-water channels was incorporated into the design to provide rearing habitat and thermal refuge for warmwater fish. And all channel features were incorporated, where possible, into the overall erosion control and bank stability design for the channel. Project construction was completed in 2000, and periodic site visits have documented development of aquatic and riparian habitat features and performance of the channel realignment and restoration elements of the project with respect to their design objectives. We summarize observations of channel, riparian, and vegetation performance over the past eight years and present lessons learned from this complex, multi-objective river restoration project.