278 



1 12-8-92 



Demonstration Project Proposal for Sediment ContamJjiant Mitigation 



Principle investigators: University of Minnesota -Duluth. J. Sorensen 218-525-7423 • 



and G. Rapp, Jr., and 

 Fond du Lac Indian Reservation - L. Schwarzkopf 



The objective of this proposed project is to demonstrate and evaluate the effectiveness 

 and applicability of various methods of reducing sediment contaminant caused residue levels 

 in fish and other biota. This work will be canied out within a series of enclosed areas at one 

 or more known sediment contaminated sites in the St Louis River and Estuaiy located in high 

 value habitat areas and/or ne<ir stream inputs. 



Sediments that have accumulated behind the reservoir dams contain high amounts of 

 various contaminants as a result of past industrial practices/discharges within the SL Louis 

 River watershed. Figure 1 shows mercury concentrations as a function of depth in a sediment 

 core taken from tlic Thomson Reservoir where the 300 cm total core dcptli represents a 

 sediment accumulation since 1907. The large peak represents mercuiy impacts during the 

 1950*s and eariy 1960*s. 



Although contaminant concentrations in sediment are significant, other contaminant 

 sources must also be considered. A comparison of merctuy in water concentrations for 

 various locations along the SL Louis River Estuary and tributaries (Figure 2) reveals the 

 existence of watershed mercury sources. In addition, mercuiy concentrations in fish as a 

 function of location (Figure 3) reveals mercuiy contamination problems from known 

 sediment hot spots. 



The enclosed areas would be rectangular (20ft x 40ft), bordered with walls of snow 

 fencing covered with reinforced plastic sheeting on three sides and natural shoreline on tlie 

 fourth side. Each enclosed area would confine (or be stocked with) local bentliic eating 

 yoimg fish at the start of the field season and analyzed (along with other biota) at the start, 

 middle, and end of the field season for condition, growth, and levels of contaminants such as 

 PCBs, PAHs, mercury, and other factois when appropriate. The effectiveness of each 

 mitigative test will be determined by comparing fish condition and contaminant 

 concentrations in treated vs untreated enclosed areas (in addition to fish from adjacent areas 

 outside the enclosed areas). Each residue reduction method being tested would be nm in 

 duplicate, and therefore a block of 6 adjacent enclosed areas. (4 treatments and 2 controls) 

 will accommodate 2 simultaneous test conditions. 



The mitigation strategies selected for demonstration must be cost effective and 

 practicable to implement Among mitigation stratepes to be. demonstrated^ . are 1) sedimenV 

 Suifacc'mijgration barriers such' as coveririg'sediments with clcanor cleaned sediments from 

 the same water body, 2) addition of contaminant binding ■ substrates such as solid pellet 

 absorbants, encapsulalors, or mesh of similar properties, and 3) in-place treatment to remove 

 surface sediment fractions (e.g. organic carbon) that arc higliest in contaminants. Because 

 some tests (e.g. sediment covering) may mitigate some contaminants more effectively than 

 others, simultaneous measurements and assessments regarding PCBs, PAHs, and mercuiy 

 would also be made when applicable. 



