John C. Marlin

Sediments and sediment-derived soils in Illinois: pedological and agronomic assessment.

Dredging sediments from water bodies in Illinois is done topreserve reservoir capacity, maintain navigation and recreationchannels, and restore habitats, but the fate of the sediments is an issue. In anticipation of a major sediment dredging operationin Lake Peoria in the Illinois River, a retrospective study ofsediment placement operations was performed. Sedimentspreviously dredged from reservoirs and placed in retaining pondswere sampled along with adjacent upland soils which served asreferences. Sediments from the Illinois River above Peoria weresampled from islands, river bottom, and adjacent floodplain. Dredged sediment retention ponds initially support wetlandvegetation. After dewatering, the physical properties of sediments tend to become similar to upland soils and theretention basins are then able to support conventionalagriculture. Sediment organic matter content was similar to localreference surface soils, and soil pH of the sediments wasneutral or above. Sediment textures are dominated by silts and clays, with the Lake Peoria samples being most clayey. Calcium was the dominant cation in all the samples, and micronutrientsmeasured were in adequate supply for plant growth. However,because the Illinois River watershed includes industrial inputs,river sediments contained elevated levels of some metals, butthey were generally below levels of regulatory concern. Resultsindicated that properly handled dredge sediments could make highquality agricultural soils. In addition, sediment placement onpoor soils could improve their productivity.

Dredged Illinois River sediments: Plant growth and metal uptake

Sedimentation of the Illinois River in central Illinois has greatly diminished the utility and ecological value of the Peoria Lakes reach of the river. Consequently, a large dredging project has been proposed to improve its wildlife habitat and recreation potential, but disposal of the dredged sediment presents a challenge. Land placement is an attractive option. Previous work in Illinois has demonstrated that sediments are potentially capable of supporting agronomic crops due to their high natural fertility and water holding capacity. However, Illinois River sediments have elevated levels of heavy metals, which may be important if they are used as garden or agricultural soil. A greenhouse experiment was conducted to determine if these sediments could serve as a plant growth medium. A secondary objective was to determine if plants grown on sediments accumulated significant heavy metal concentrations. Our results indicated that lettuce (Lactuca sativa L.), barley (Hordeum vulgare L.), radish (Raphanus sativus L.), tomato (Lycopersicon lycopersicum L.), and snap bean (Phaseolus vulagaris L. var. humillis) grown in sediment and a reference topsoil did not show significant or consistent differences in germination or yields. In addition, there was not a consistent statistically significant difference in metal content among tomatoes grown in sediments, topsoil, or grown locally in gardens. In the other plants grown on sediments, while Cd and Cu in all cases and As in lettuce and snap bean were elevated, levels were below those considered excessive. Results indicate that properly managed, these relatively uncontaminated calcareous sediments can make productive soils and that metal uptake of plants grown in these sediments is generally not a concern.

Sediment quality and quantity issues related to the restoration of backwater lakes along the Illinois River waterway

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. Necessary parts of the overall restoration effort are to adequately characterize both the quality and quantity of backwater lake sediments prior to implementing any restoration efforts, and to identify potential beneficial reuses of dredged sediments. This paper summarizes some of our efforts in these areas with an emphasis on Peoria Lake which has received the most attention to date. Sediment characterization has included detailed bathymetric surveys, sediment dating with 137 Cs, chemical and mineralogical characterization of sediments to three meters depth, analysis of recent sediments (to 30 cm depth) for acid-volatile sulfide and simultaneously extracted metals, and analysis of ammonia and toxic metals in sediment pore waters. Dredged sediments have also been used in various trial projects to demonstrate potential handling and beneficial reuse strategies. Some significant findings of these studies are: 1) Long-term sedimentation rates are high, and average 1–3 cm y −1 ; 2) total concentrations of several trace metals (e.g., Pb, Cd, Ni) and PAH compounds sometimes exceed consensus-based probable effect levels for sensitive sediment-dwelling organisms; 3) pore water dissolved ammonia concentrations in Peoria Lake are potentially toxic to sensitive sediment-dwelling species; and 4) weathered sediments can make productive agricultural soils.

ILLINOIS RIVER DREDGED SEDIMENT: CHARACTERIZATION AND UTILITY FOR BROWNFIELD RECLAMATION 1

Brownfield reclamation in some ways is similar to surface mine reclamation. The similarities are that in both cases there is a large area of once productive ground that was severely impacted as part of a no-longer active resource extraction or augmentation industry. The differences include possible toxic soils or substrate and generally a lack of nearby quality soil for the brownfields given their typically urban settings. In contrast, reclamation is now part of a surface mining permit, soils are stockpiled to be replaced after mining, or topsoil substitutes are located and approved to serve as a final cover at a mine site. Brownfields, however, are usually located in urban areas where topsoils are difficult to obtain and transport. We conducted a large field demonstration project involving a brownfield in Chicago that was reclaimed with dredged spoils from the Illinois River. Disposal of dredged spoil often presents a problem in and of itself, and utilization as a topsoil substitute presents several advantages. In the case of the Peoria River sediments, the chemical and physical attributes are generally favorable as a topsoil substitute. These sediments tend to be fine textured, Silty Clay Loams and Silty Clays with about 3-5% organic matter content. Metal content is typically elevated above reference soils, but is generally not a problem. This paper presents our experience with this reclamation approach.

Evaluation of Potential Removal and Beneficial Use of Illinois River Sediment

The Illinois Department of Natural Resources is investigating techniques for removing sediment and using it beneficially. Numerous sediment cores, including ten extending two meters, were analyzed for a variety of metals and chemicals as well as agricultural nutrients. Plant germination and growth tests comparing fresh and weathered sediment to Illinois topsoil were conducted in a greenhouse. A hydrodynamic model of a portion of the river was developed to assist in predicting the effects of sediment removal and placement. A number of options to remove sediment at near insitu moisture content are under consideration including high solids pumps, excavators, clamshells and conveyors. This would minimize turbidity, resuspension and dewatering while maximizing options for sediment transport and placement. Researchers are looking at sites where dredged material was placed in the past to determine the qualities of soil formed by fine-grained sediment similar to that in the Illinois River. It is hoped that sediment will prove useful as a landscaping soil, soil amendment, brownfield cover and for strip mine reclamation. Additionally sediment may be used to create islands and floodplain habitat that is similar in elevation and geometry to that which existed prior to the major hydrologic changes that occurred beginning in 1900.