Peyton Slough Restoration

Martinez, CA

Rhodia Chemical
Fall 2003

Hanford ARC was contracted by Rhodia Chemical Company through Dutra Construction to implement mitigation measures and rare species habitat restoration for the Masons lilaeopsisand erosion control for the Peyton Slough restoration project, designed by URS. The unstable nature of the work area made access and mobilization of large equipment challenging. Low ground pressure (LGP) equipment accessed the work area across the existing Peyton Slough and side channels over crane mats. Hanford ARC placed temporary protective fencing in the sensitive areas along the access route and along the Carquinez Straight. A long access path was cleared along the top of an old spoils pile from the land side of the project to the edge of the Straight. Brush obtained from the clearing was stockpiled for use in a brush fence.

The Masons lilaeopsis is found at approximately 1-foot elevation, therefore the proposed log habitat structures were constructed at very low tide. Designed for a wave break, a brush fence was constructed by driving poles into the bay mud, with brush packed between and tied down. A series of log structures were installed to replicate an overhanging bank condition, which is where the rare plant is typically found. Working in harsh conditions, a tracked excavator cut a key for the logs to be placed longshore. Hanford ARC employed an LGP tracked truck and skid-steer loader to assist the excavator with structure installation. Duckbill anchors with ¾-inch threaded rods were driven to a depth of 12 feet to anchor the structures, and Hanford later cribbed the structures with pilings due to the buoyancy of the redwood logs used.

The Masons lilaeopsis was salvaged by hand into manageable sod clumps, loaded into a tracked dump truck, and transported to the planting areas behind the log structures. The harvest and installation was run as a continuous operation to ensure that no plants were stockpiled longer than required for transport. As plants were installed, aviary wire was folded back over the plants and keyed and staked at the inland edge of the planting. The crews placed the wire daily, prior to high tide to avoid loss of plants due to floating . A laser level determined appropriate subgrade to accurately match the salvage site elevation.

In addition to the plant salvage efforts, Hanford ARC performed erosion control and revegetation at a new tide gate and slough diversion point. Hanford ARC installed approximately 4,500 square feet of Pyramat and installed 6,000 plant plugs. Hydroseeding was completed on graded areas to revegetate with native herbaceous plant species. Hanford ARC performed an 18 month maintenance program and has been retained by Rhodia for emergency erosion repairs.