The project goal was to remediate and restore a heavily impacted “Toxic Hot Spot” wetland slough. The impacted property had been in continuous industrial use since the 1900’s as a copper ore smelter and then a pyrite roaster which contaminated a slough vital for ensuring drainage capacity and maintaining tidal influence in the surrounding marshes. The innovative, “first of its kind” solution involved realignment by means of dredging a new winding slough, and capping of the previously contaminated area. The new sinuous design provided foraging habitat for birds and fish while isolating the contaminated sediments preventing them from flowing into the Bay.
Major Challenges
Native Suisun Song Sparrows and Salt Marsh Common Yellow Throat nesting locations existed within the construction site. Mason’s Lilaeopsis, a rare plant, also existed in the site and was successfully relocated out of the construction zone. Performing work in active tidal wetlands areas required placing fill at low tides whenever possible to reduce impacts.
Project Scope
Marine Demolition.
Dredge realignment slough along a winding course parallel to existing contaminated slough.
Construct a one mile soil containment cap to isolate contaminated sediments.
Construct 5 acres of new wetlands including new habitat atop soil cap and enhance 200 acres of existing wetlands.
Construct associated Tide Gates, Brush Fence and Erosion Control.
Construct Bulkhead and Shoreline Protection.
Demonstrate strict adherance to Dredge Spoils Management, Environmental Protection, and Water Quality Management “best business practices”.