Abstract

 Sedimentation has severely impacted backwater lakes along the Illinois River. The State of Illinois and the US Army Corps of Engineers are currently involved in a joint effort to address ecosystem degradation within the Illinois River Basin, and excessive sedimentation of backwater lakes and side channels is a primary cause of that degradation. A necessary part of the overall restoration effort will be to adequately characterize both the quality and quantity of sediments in backwater lakes prior to implementing any restoration efforts such as the restoration of deep water habitats by dredging.
  This presentation will provide an overview of past, present, and future efforts related to assessing sediment quality and quantity in backwater lakes along the Illinois River. Focus will be on Peoria Lake sediments, which have been the most thoroughly characterized to date. This characterization has included detailed bathymetric surveys, sediment dating (137Cs), chemical and mineralogical characterization of sediments to 3 meters depth. The study also included analysis of recent sediments (to 30 cm depth) for acid volatile sulfides and simultaneously extracted metals, as well as associated pore waters for dissolved ammonia and trace metals. Finally, the agronomic potential of Peoria Lake sediments has been investigated as a potential beneficial reuse strategy.
  Some significant findings of these studies are: 1) long-term sedimentation rates are high, and can reach 3cm/yr; 2) total concentrations of several trace metals (e.g., Cd, Ni) and PAH compounds often exceed consensus-based probable effect levels; 3) dissolved ammonia is potentially toxic to sensitive indigenous species; 4) weathered sediments can make productive agricultural soils.