Our Projects

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 around 1900 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 allow remaining sediment to wash downstream during flood events. Log structures were designed for the channel below the dam to capture sediment and restore habitat for threatened central California coast steelhead (Oncorhynchus mykiss). The project’s goal was restored access for steelhead to more than 1.5 miles of stream above the dam.

WRA worked closely with the City’s engineering consultant to gain consensus on the design and permitting approaches during a series of monthly meetings with regulatory agencies and adjacent landowners. 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. WRA assisted with bid-phase services including pre-bid meetings and bid addenda.

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 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. WRA is currently conducting post-construction monitoring.

Related Media

• Read WRA’s Field Notes blog article: “Steelhead Migration Restored in a Napa River Tributary with Removal of a Century-old Dam“
• View WRA’s interactive ArcGIS storymap
• Watch the City of St. Helena’s project video produced by Oakland-based Youth Beat
• Read the St. Helena Star’s article about the ribbon cutting event