Chunhua Liu, Gradient Corporation, Jenny A. Jay, Tufts University, Timothy E. Ford, Harvard School of Public Health

Previous studies conducted in our laboratories have shown that submarine groundwater discharge (SGD) can significantly increase metal fluxes from capped contaminated sediment to the overlying water. Five columns were set up in the laboratory to evaluate the effects of groundwater pH, sediment depth, and groundwater flow rate on metal transport from capped contaminated sediment under conditions of SGD. Acidified groundwater discharge was shown to enhance the mobility of all tested metals except Mo. Although much of the released metal was adsorbed by the capping material, increased metal fluxes to the overlying water were observed for Ni, Cu, Zn, and Pb. Additional sediment depth enhanced fluxes for all tested metals except Cd and Pb. Increased SGD rates did not significantly change the steady-state volume-normalized fluxes for all the metals except for Cr and Mo. However, all metal releases were higher due to the greater flow at increased SGD rates.

Steven A. Rock, US EPA, Jorge McPherson, SAIC, Richard A. Price, US ACE, WES, Robert Graziano, Arcadis

The Jones Island Confined Disposal Facility (CDF) located in Milwaukee Harbor Wisconsin, receives dredged materials from normal maintenance of Milwaukee’s waterways, and has done so for many years. Like many CDFs across the country, Jones Island faces the dilemma of steady inputs and no feasible alternative for expansion. The Army Corps of Engineers (AEC) in partnership with the Milwaukee Harbor Authority, is exploring a large range of beneficial reuse options for the dredged material, from building and road fill, to landscape material.

Aged dredged material at Jones Island is heterogeneous in composition because it comes from waterway sources over a wide area over many years. Some dredged materials contain EPA listed wastes from industrial discharge, spills, and urban run-off in widely varying concentrations. Natural attenuation processes occur at differing rates due to random placement in the CDF and various oxygen, moisture levels and weathering impacts.

The first step taken on this project toward determining appropriate end use of the stored material was a detailed characterization across the CDF with samples taken at three depths and analyzed for PAHs, PCBs, and metals. Diesel range organics (DRO) analysis was also run to determine if the less expensive DRO test could be substituted for PAH and/or PCB testing. The resultant map showed areas of high and low concentrations, and pinpointed areas of opportunity for remediation. The DRO results were analogous to the PAH results, allowing more frequent and extensive testing for the same cost.

Treatability studies conducted at the AEC Waterways Experiment Station using crops and grasses determined that plants would survive in the material and degrade the contaminants. Corn and clover had the highest degradation effect over the short test period.

Field plots were established on the CDF by excavating, mixing, and depositing soil in test cells. The test plots closely follow the Remediation Technology Development Forum (RTDF) protocol for plot size, sampling, and statistical design. At Jones Island there are four treatment plots: a rotation of corn and clover, willow, local grasses, and an unplanted control.

Lisa Saban, CH2M HILL

Ecological risk-based approaches are integral to making management decisions regarding sediment remedial strategies. This talk will focus on three key techniques for those involved in issues related to contaminated sediments: risk assessment/risk management, cost-benefit analyses of remedial options, and net environmental benefit analyses. These three inter-related tools, when used as part of an overarching site strategy, will be most effective in reducing unnecessary expenditures and providing for the greatest environmental protection. Ecological risk assessment techniques are key to framing the problem, defining the resources potentially at risk, and subsequently quantifying the risks. Integral in the risk assessment process are the risk management decisions. Historically, risk management decisions were made after the final quantification of the assessment of risk. More recently, EPA and ASTM have advocated for a more holistic approach-incorporating risk management into the risk assessment process. This lends itself to a more robust management tool, and avoids unnecessary costs associated with repetitive risk calculations. Once the risks are identified and management implications are known, a cost-benefit tool can be applied to determine the most effective, yet protective, remedial option. Restoration-based methods have been used successfully to offset some of the cost-prohibitive remedial options. This results in a net environmental benefit, that is, while some contamination may remain in place, the restoration activities result in a net gain in the ecological resource at risk (such as benthic community composition or wetland habitat). The trade-off between remediation and restoration activities can be quantified and applied to sites with complex issues that may benefit from a more holistic approach. This presentation will discuss each of these techniques and provide examples of success stories (and not so successful stories) of the application of these tools to various projects. Projects include a PCB issue in an intertidal habitat, PAHs, metals, and pesticides in a canal system, and a hydrocarbon subsurface sediment plum issue.

Jack Q. Word and David M. Moore, MEC Analytical Systems, Inc

There are three general types of sediment features that result in toxicity to sediment dwelling test organisms. These include 1) persistent, non-contaminant features of sediment (e.g., physical grain size, total organic carbon content and in some cases water content of sediment), 2) persistent chemical contaminants (e.g. DDT, PCB, Heavy metals) and 3) non-persistent chemical contaminants (e.g., ammonia, salinity of interstitial water and temperature). Each of these major types of mortality producers appears to operate differently under conditions of sediment disturbance and stability. We have developed a series of test protocols that can be used to separate these general features of sediment toxicity. They consist of a standard toxicity test established within 24h of initial mixing and test setup, stocking of test sediment that has been allowed to remain undisturbed for a period of 3 weeks and stocking of the sediment that is redisturbed after the period of stability. Under these test scenarios there are three responses. The persistent non-contaminant features of sediment maintain the same level of response under all three forms of disturbance. The persistent chemical contaminants in sediment have an elevated toxicity under the initial and final disturbance events while under the undisturbed conditions the toxicity of the sediment is much less. Finally, when the toxicity of the sediment is due to non-persistent contaminants the responses are elevated toxicity at the beginning of the test, reduced toxicity under the undisturbed conditions and continued reduced toxicity under the redisturbed conditions. The biological, chemical and physical features that control toxicity under these three conditions will be discussed. We will also discuss the application of these types of tests for identifying the causes of toxicity in sediment tests.