Water Column Mercury at Duluth Superior Harbor Dredging and Placement Sites


The purpose of this project is to evaluate water column mercury concentrations at dredging and dredge material placement sites in Duluth-Superior Harbor. This information is critical for informing decisions about open water placement of dredge material in the harbor and the selection of locations for habitat restoration for delisting beneficial use impairments (BUIs) in the St Louis River AOC. The proposed sample set will provide a measure of mercury levels associated with dredging/placement activities and will enable a comparison of mercury levels between the dredging and placement site with areas of areas of no activity. This is important because if dredge material is used to restore habitat it must not increase mercury availability and potentially impede BUI removal for fish consumption advisories.

Study Design

Two sample events with six sample sites are proposed for a total of 12 water samples. Dredging in Duluth-Superior Harbor will begin mid-August and last until November 2013. One sample event would be scheduled when dredging/placement operations are underway, with a second sample scheduled after placement activities and prior to removal of the silt curtain. Specific sample locations will be determined when dredging operations begin, but are proposed as: 1 Upstream of dredging and placement activity 1 Dredging site 1 Placement/discharge area 1 Downstream of dredging and placement activity 1 Field blank 1 Field duplicate

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Reports and Documents
Low level mercury sampling during open water dredge material placement operations in Duluth-Superior harbor