York Creek Restoration
The project involved the removal of Upper York Creek Dam in the City of St. Helena located in Napa County, California. The 50-foot earthen dam was built in 1907 to create a water supply reservoir and had become filled with sediment. Hired by lead engineer, EKI Environment & Water, Inc. (EKI), WRA’s design team worked closely with the City, the National Marine Fisheries Service (NMFS), and a host of other regulatory agencies to prepare a design that called for a process-based approach, where the dam was notched and a pilot channel cut through the sediment to connect the upstream and downstream reaches of York Creek. Remaining sediment is expected to wash downstream during flood events. Log structures were built in the channel below the dam to capture sediment and restore habitat for threatened central California coast steelhead (Oncorhynchus mykiss). The project restored access for steelhead to more than 3 miles of stream. The project also involved ensuring that an existing concrete overflow spillway supporting the adjacent county road be maintained, and that active landslide locations are avoided by construction activities.
WRA worked closely with the City’s engineering consultant to gain consensus with regulatory agencies and adjacent landowners during a series of monthly meetings. The project involved consultations with NMFS and the U.S. Fish and Wildlife Service to ensure that project actions would not negatively affect populations for northern spotted owl, California red-legged frog, or steelhead that are likely to occur on the site. Permitting through the U.S. Army Corps of Engineers, California Department of Fish and Wildlife, and the local Regional Water Quality Control Board was also required.
Direct field oversight and inspection was provided by WRA during the installation of the log structures to ensure the field fit with available materials met the hydraulic stability requirements and design plans. WRA also performed all required compliance surveys and biological monitoring for the project.
Due to funding requirements, WRA completed the final design in less than five months and secured regulatory permits in seven months. Construction on the project started was complete in September 2020, however, the project site and its upstream watershed was burned by the Glass Fire only three days after installation. WRA assisted with post-wildfire assessments, retrofit measures on a few of the damaged log structures and monitoring for possible secondary post-fire hazards.