Napa River Rare Plant Salvage

Napa County, CA

US Army Corps of Engineers
Fall 2003 to Fall 2004

Hanford ARC acted as the prime contractor on this project which involved salvage and restoration of the State listed rare plant, Mason’s lilaeopsis (Lilaeopsis masonii). The plant grows along the mid to low tidal zone of the lower Napa River. Several populations were located in areas to be graded as part of the Napa River Flood Protection Project.

The Corps provided locations of the existing populations, and a schematic diagram for the construction of a series of log structures designed to provide appropriate habitat for the delicate plant. Prior to the excavation and grading operations of Contract 1B, the plant was salvaged and stored by Bitterroot Restoration for approximately one year. After completion of the Contract 1B grading, Hanford ARC installed the log structures and replanted the Mason’s lilaeopsis.

Hanford ARC provided field design services to determine the precise locations of the log structures both horizontally and vertically. We surveyed existing populations across the river to determine an appropriate elevation range to establish the plants on the newly graded riverbank. A total of four sites were replanted, with two log structures and two sites which were graded only.

The log structures were created based on guidelines provided (such as length of structure) and the specific conditions at the each restoration site as determined in the field. Large oak logs, up to four-foot diameter and 30-feet long, salvaged from the clearing operation in Contract 1B, were used in the structures.

In constructing the structures, the top edge of the outer log was set to the low end of the appropriate elevation range. Anchor logs, designed to weigh the outer logs down, were trenched into the bank, and large duckbill anchors were set and cabled to the structure. Open weave erosion control fabric was incorporated behind the logs as fill was being placed, and wrapped back over the areas once planting was complete.