Giacomini Wetland Restoration Project Final Report on Screening for Sediment Contamination in the Study Area

Parsons, Lorraine; Allen, Leslie

This report describes a study completed to determine the potenital impacts and risk of sediment contamination in the Giacomini Wetland Restoration Project area during the restoration project. The National Park Service (NPS) is studying the potential impacts to the environment from restoring tidal wetlands in the Giacomini Wetland Restoration Project. While a project alternative has not yet been selected, restoration activities are anticipated to cause some degree of soil disturbance and/or relocation. Through resuspension of disturbed soils in the water column, any sediment contaminants that are present could become available for uptake by biota within the Project Area or elsewhere in the Tomales Bay watershed. In addition, tidal wetland restoration may actually increase the toxicity of certain trace metals present such as mercury. Because of these concerns, the NPS decided to conduct a screening-level sediment contaminant study in the Giacomini Ranch (Project Area) and adjacent areas (Study Area). Based on our results it appears that the risk of impact to the environment from sediment contamination in the Project Area is minimal, although reporting limits for some of the analytes preclude us from conclusively stating that there is no threat.