cbec is providing peer review as part of a revision of an EIS/R associated with a proposed development project at Grady Ranch, part of Skywalker Properties, Marin County, CA.

The EIS/R is being undertaken by the Marin County Flood Control & Water Conservation District. cbec staff has performed field geomorphic reconnaissance of Miller Creek and has conducted peer review of design strategies associated with restoration of this heavily degraded creek.

The design of the proposed restoration of Miller Creek and its tributaries on the Grady Ranch property includes backfilling and raising the bed elevation of the degraded streambed. This action should theoretically allow for additional groundwater storage within the alluvial aquifer above the existing base level of the stream and improve the overall continuity of the aquifer. The proposed restoration would involve the placement of approximately 53,000 cubic yards of fill material in the bed of Miller Creek and its tributaries in an effort to eliminate fish passage barriers, reactivate floodplain area, and increase aquifer storage. These project goals are essential to restoring the ecological function of the creek corridor while minimizing channel erosion and sediment delivery to the lower Miller Creek watershed. Boulder placement producing step pool sequences is proposed to stabilize the fill material and to provide an increase in channel roughness, which would help to attenuate both flow and sediment.

cbec provided various design recommendations to minimize potential impacts to the structural integrity of the creek, and potential flood risk reduction measures.