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Redesigning Marsh Creek Dam to allow Chinook salmon passage, flood protection, and mercury sedimentation

  • Author(s): McNulty, M. Eliza
  • Wickland, Matthew
  • et al.
Abstract

Marsh Creek has undergone several modifications for flood control purposes since the early 1960’s. These projects included a grade-control drop structure and a flood-control dam, both of which impede fish passage along the creek. In addition, mercury pollution due to mine tailings at the upstream end of the creek has caused elevated mercury levels in stream biota and reservoir sediments. Although Chinook salmon have been observed in the lower reaches of Marsh Creek, the upper reaches are currently inaccessible, but would provide ideal salmon spawning habitat. Currently several proposals and plans exist to remove the drop structure and restore lower Marsh Creek, allowing salmon to migrate an additional seven miles upstream, as far upstream as the Marsh Creek Reservoir. In addition, the Contra Costa County Flood Control District hopes to redesign the reservoir to increase floodwater storage. This project presents a redesign of the Marsh Creek Reservoir, which allows fish access to the upper Marsh Creek spawning habitat, creates the flood storage capacity necessary to protect communities in the lower watershed, and attempts to minimize the impact of mercury pollution in the lower watershed. Given the increased public interest and support for restoration efforts along Marsh Creek, combined with the need for increased storage capacity of Marsh Creek Reservoir, a plan integrating fish passage, flood control, and mercury removal is essential.

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