Lower Redwood Creek Restoration

Golden Gate National Recreation Area
Muir Beach , CA

National Parks Conservancy
Fall 2003

The National Parks Conservancy and National Park Service (NPS) selected Hanford ARC to construct this salmon and steelhead habitat restoration project located in the Golden Gate National Recreation Area, upstream from Muir Beach, CA. Redwood Creek is habitat for both coho salmon and steelhead trout.

The project spans 1,900 feet of lower Redwood Creek, which historically had been cut off from its flood plain by levees, and cleared of large woody debris. Few pools remained in this reach, and the sinuosity was extremely low, resulting in poor habitat for spawning and over-summering anadromous fish species. In addition, a 90-foot segment of channel was severely eroded, contributing large amounts of sediment to the channel annually.

Phil Williams Associates designed the restoration project to include installation of a series of log weirs, log toe revetments, an engineered log jam, and levee removal and floodplain restoration. During construction, PWA worked with NPS to layout log structures and verify accuracy of installation.

A total of 8 log weirs were constructed using eucalyptus logs up to four-foot diameter and 35 feet long, with six to eight foot diameter root wads, provided by the Park Service. The log weirs were installed and anchored with pinning logs, which eliminated the need for cable and anchors. Five weirs were installed independently and three were installed in one complex structure, which included vertical pinning members (see photo left). The purpose of these structures is to encourage a meander in the channel, create scour pools, and provide cover for fish.

In addition to the log weirs, an engineered log jam was constructed along the 90-foot section of severely eroded bank. In this segment, the banks were laid back at a 3:1 slope, and a structure consisting of 13 logs up to three feet in diameter by 30 feet long were installed both parallel and perpendicular to the bank. Vertical pinning members were driven 7 – 15 feet into the channel substrate.

The stream was dewatered in three segments for the log installation. The dewatering operations required extreme sensitivity due to the fact that the stream is habitat to federally listed species. Several layers of screening were installed at the pump intake, and the National Park Service performed extensive fish removal.

Following surface flow dewatering, a high flow deep in the channel substrate required continuous or regular dewatering of the channel during excavation. Turbid water generated during construction was removed from the stream and discharged into the adjacent farm field.

Floodplain restoration involved removal of the levees along the channel, as well as excavation of a riparian terrace. Approximately 3,000 – 4,000 yards of soil were removed from the length of the project reach and spread in a nearby field. Sediment control measures included a wire-backed silt fence, lined at the base with straw wattles and staked with metal posts, along sections of the creek where grading left no vegetative buffer.

Hanford ARC performed careful and detailed excavation to reach narrow grade tolerances and avoid impacts to the channel from grading.

Hanford ARC performed all grading, excavation, dewatering, and log installation under the supervision of the NPS. During construction, the RWQCB, National Marine Fisheries Service, and California Department of Fish and Game conducted site visits. The NPS followed Hanford ARC with volunteer planting on the new floodplain and brush mattress installation above the engineered log jam.