Characterization and Mapping of Contaminated Sediments, Windermere Arm, Hamilton Harbour, Ontario, Canada
Alex J. Zeman, Environment Canada, Burlington, ON, Canada
Timothy S. Patterson, Environment Canada, Burlington, ON, Canada  

Estimation of Sediment PCB Concentrations and Masses in a Large Water Body
R. Scott Wade, Limno-Tech Inc. (LTI), Ann Arbor, MI
Joe V. DePinto, Limno-Tech Inc. (LTI), Ann Arbor, MI
Penelope E. Moskus, Limno-Tech Inc. (LTI), Ann Arbor, MI
John R. Wolfe, Limno-Tech Inc. (LTI), Ann Arbor, MI  

Stormwater Impact on Sediment Quality as Determined by Microbial Indicators
Hueiwang Jeng, Tulane University, New Orleans, LA
A.J. Englande, Tulane University, New Orleans, LA
Reda Bakeer, Tulane University, New Orleans, LA
Henry Bradford, Louisiana Department of Health and Hospital, New Orleans, LA

Electroosmotic Dewatering of Dredged Sediments
Krishna R. Reddy, University of Illinois, Chicago, IL

Assessing the Effectiveness of Sediment Remediation using Contaminant Transport Models
Hans P. Holmberg, Limno-Tech, Inc. (LTI), Hudson, WI
Joseph V. DePinto, Limno-Tech, Inc. (LTI), Ann Arbor, MI
Todd M. Redder, Limno-Tech, Inc. (LTI), Ann Arbor, MI
John R. Wolfe, Limno-Tech Inc. (LTI), Ann Arbor, MI

Determination of the Environmental Impact of Consolidation Induced Convective Transport of Radiolabeled Contaminants through Capped Sediment Using a Research Centrifuge
Horace Moo-Young, Lehigh University, Bethlehem, PA
Tommy Myers, Waterways Experiment Station, Vicksburg, MS
Barbara Tardy, Waterways Experiment Station, Vicksburg, MS
Richard Ledbetter, Waterways Experiment Station, Vicksburg, MS
Wipawi Vanadit-Ellis,  Waterways Experiment Station, Vicksburg, MS
Kassahun Sellasie, Lehigh University, Bethlehem, PA

Reverse Layering for In-Situ Burial of Nutrient-Rich or Contaminated Sediments
William B. Kerfoot, K-V Associates, Inc., Mashpee, MA
Stephen G. Seymour, Town of Barnstable, Department of Public Works, Hyannis, MA 

Characterization and Mapping of Contaminated Sediments, Windermere Arm, Hamilton Harbour, Ontario, Canada

Alex J. Zeman, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, ON L7R 4A6, Canada, Tel.: 905-336-4882, Fax: 905-336-6430
Timothy S. Patterson, National Water Research Institute, Environment Canada, 867 Lakeshore Road, Burlington, ON L7R 4A6, Canada, Tel.: 905-336-4469, Fax: 905-336-6430

Windermere Arm is a 50-ha narrow channel located in the south-eastern portion of Hamilton Harbour, which is designated by the International Joint Commission (IJC) as one of the primary Areas of Concern in the Canadian waters of the Great Lakes. Sediments within the Arm have historically been contaminated with trace metals, PAHs, and to a lesser extent, PCBs.  Sedimentological, geotechnical and geochemical investigations have been undertaken to determine the degree and the spatial extent of contamination. The methodology used in sediment characterization includes acoustic bottom-classification systems, side-scan surveys, in-situ penetration tests, gravity core sampling and vibracoring. Bottom sediment types are identified by an acoustic bottom-classification system called RoxAnn^TM , which uses the information on sediment roughness and hardness and is then calibrated against surficial sediment texture. Disturbance of sediment due to dredging, dumping and anchor-dragging is obtained from side-scan and multibeam echosounder records. Physical properties of the sediments are determined by measurements of sediment texture, moisture content and fall-cone shear strength. Contaminant concentrations (PAHs, PCBs, trace metals) are measured at standard intervals in each core. Several contouring methods will be used to produce three-dimensional maps of sediment contamination and to calculate volumes of contaminated sediments. Information on the spatial extent of sediment contamination in the Arm will be used for the selection of the most effective remedial alternative and for identifying sources of certain contaminants. The study is funded by the Great Lakes Sustainability Fund of Environment Canada.

R. Scott Wade, Joe V. DePinto, Penelope E. Moskus, and John R. Wolfe, Limno-Tech, Inc. (LTI), 501 Avis Drive, Ann Arbor, MI  48108, Tel: 734-332-1200, Fax: 734-332-1212 

Decision-making for contaminated sediment sites requires an accurate estimation of the horizontal and vertical extent and the magnitude of the contamination.  Accurate estimations of contamination reduce uncertainty in models that simulate the fate and transport of the contaminated sediments and provide a sound basis for choosing among potential remediation and management options.  Achieving accurate estimates can be more complex if the region of concern is a large water body, such as a bay.  Sediment samples can be widely dispersed and sediment characteristics of large areas need to be estimated from samples that can be several kilometers distant.  Results of sediment sampling in Green Bay in Wisconsin and Michigan were collected and organized.  Using a geographic information system (GIS), potential interpolation methods and options were evaluated with the intent of reducing uncertainty.  Then sediment parameters essential for an estimation of PCB mass were interpolated for the entire bay.  Approximately 15,000 kg of PCB were estimated to reside in the sediments, with a wide range of concentrations and masses among various portions of the bay.  The assumptions of this estimate are weighed against the assumptions of the authors of other, differing published estimates.

Stormwater Impact on Sediment Quality as Determined by Microbial Indicators

Hueiwang Jeng, Tulane University, 1440 Canal Street, New Orleans, LA, 70112, Tel: 504-587-7619, Fax: 504-584-1726
A.J. Englande, Tulane University, 1440 Canal Street, New Orleans, LA, 70112, Tel: 504-584-2765, Fax: 504-584-1726
Reda Bakeer, Tulane University, 6823 St. Charles Avenue, New Orleans, LA, 70118, Tel: 504-865-5778, Fax: 504-862-8941
Henry Bradford, Louisiana Department of Health and Hospital, 325 Loyola Ave, New Orleans, LA 70112 Tel: 504-568-5375

This study was conducted to examine the fate of microbial indicators from stormwater runoff associated with lake sediments and stormwater suspended particles.  Knowledge gained from this study can lead to better understanding of both the impact of stormwater runoff on the lake sediment environment and fate of microbial indicators in lake sediments. Results of the study indicate that a significant increase occurred in the microbial indicator titers for sediments at specific study sites following a given stormwater event. It was found that the sedimentation mechanism is linked to the increase in microbial titers in the lake sediments as stormwater microbial indicators were found to attach onto stormwater suspended particles. Thus, stormwater runoff contributes to microbial contamination and deterioration of sediment quality.  At the study sites, the percentages of fecal coliform, E. coli, and enterococci attached to stormwater suspended particles were found to be in the range of 9.8 to 27.5 percent, 21.8 to 30.4 percent, and 8.3 to 11.5 percent of the total indicator loading, respectively. Additional sorption may have occurred to non-settleable particles which remained in the water column. Examination of the suspended particle size distribution showed that about 85 percent of the microbial indicators were attached to the suspended particles larger than 5 mm.  Based on the collected data, the estimated sedimentation rate constants were calculated to be 0.0370 h^-1 for fecal coliform, 0.0678 h^-1 for E. coli and 0.0359 h^-1 for enterococci. The elevated titers of microbial indicators in the sediment were observed to decrease with time.  However, a slower rate reduction of microbial indicators in sediment further suggested that bottom sediment may act as a reservoir for prolonging microbial survival and adds concerns of recontamination of overlying waters due to potential sandy solids resuspension.

Electroosmotic Dewatering of Dredged Sediments

Krishna R. Reddy, Ph.D., P.E., University of Illinois, Department of Civil and Materials Engineering, 842 West Taylor Street, Chicago, IL 60607, Tel: 312-996-4755, Fax: 312-996-2426, Email: kreddy@uic.edu

Dredged sediments generally possess very high moisture content and very low hydraulic conductivity.  As a result, disposal of these sediments in confined disposal facilities (CDFs) is implemented in stages.  A layer of sediment is placed and enough time is then allowed for the dewatering and consolidation of sediments to occur.  Innovative methods are sought to accelerate dewatering that allow rapid disposal of sediments in CDFs. Common dewatering techniques such as the use of pumps, drains or chemical additives are often ineffective and/or expensive for the low permeability sediments.  Electroosmotic dewatering has great potential to accelerate dewatering in sediments.  This study investigated the feasibility of using electroosmosis to dewater dredged sediment obtained from Ispat-Inland site.  Bench-scale experiments were conducted using the sediment under the application of a low electric potential as well as under gravity drainage alone.  The results showed that an order of magnitude increase in dewatering and consolidation of the sediment occurred under the application of electric potential as compared to the gravity drainage alone.  Various factors that require attention during the field implementation of electroosmotic dewatering, such as power consumption, electrode types, outflow quality and management, and quality of dewatered sediment solids, are discussed.

Assessing the Effectiveness of Sediment Remediation using Contaminant Transport Models

Hans P. Holmberg, Limno-Tech, Inc. (LTI), 2237 Sacia Lane, Hudson, WI 54016, Tel: 715-386-1320, Fax: 715-386-1510
Joseph V. DePinto, Todd M. Redder, and John R. Wolfe, Limno-Tech, Inc. (LTI), 501 Avis Drive, Ann Arbor, MI 48108, Tel: 734-332-1200, Fax: 734-332-1212

Contaminant fate and transport models are critical components of the decision-making process for large-scale contaminated sediment sites. Models synthesize data on system characteristics with data on system forcing functions to simulate future conditions as a function of key stressors and external perturbations. Fate and transport models can simulate exposure concentrations in the bioavailable zone, including the water column and surface sediment concentrations that drive human health and ecological risks. Exposure concentrations simulated by fate and transport models serve as inputs to bioaccumulation models and human-health risk assessment models. This suite of models provides a quantitative basis to compare sediment management options and evaluate the risk reduction they can achieve over time. Management options include active remediation such as capping and dredging, and also natural attenuation. The reality of long implementation schedules, contaminant releases during dredging, and residual concentrations require consideration in the evaluation of remediation effectiveness relative to natural attenuation. This paper presents modeling methods for simulating active remediation and approaches for assessing the relative effectiveness of remediation given uncertainty in model parameterization. Case study examples from large-scale contaminated sediment sites will be presented that demonstrate the necessity of selecting a basis for comparison of remedial alternatives that is consistent with risk-based remediation goals and realistic implementation conditions. Results of modeling evaluations of the Fox River in Wisconsin will be presented. These results show that an assessment of remediation effectiveness is very sensitive to the representation of remediation schedule, releases during dredging, and residual surface sediment concentrations in the model application. Depending on the assumptions used for releases and residuals, model results show that active remediation by dredging may even increase risks in the short and long-term relative to natural attenuation.

Determination of the Environmental Impact of Consolidation Induced Convective Transport of Radiolabeled Contaminants Through Capped Sediment Using a Research Centrifuge

Horace Moo-Young, Lehigh University, Bethlehem, PA 18015, Tel: 610-758-6851, Fax: 610-758-6405, Email: Hkm3@lehigh.edu
Tommy Myers, Waterways Experiment Station, Vicksburg, MS 39180, CEERD-EP-E, Tel: 601-634-3939, Fax: 601-634-3833, Email: MYERST@wes.army.mil
Barbara Tardy, Waterways Experiment Station, Vicksburg, MS 39180, CEERD-EP-E , Tel: 601-634-3574, Fax: 601-634-3833, Email: tardyb@wes.army.mil
Richard Ledbetter, Waterways Experiment Station, Vicksburg, MS 39180, Tel: 610-634-2688
Wipawi Vanadit-Ellis,  Waterways Experiment Station, Vicksburg, MS 39180, Tel: 610-634-2688, Email: ellisw@wes.army.mil
Kassahun Sellasie, Lehigh University, Bethlehem, PA 18015, Tel: 610-758-4412, Email: kasq@lehigh.edu

The presence of contaminated sediment poses a barrier to essential waterway maintenance and construction in many ports and harbors, which support 95% of U.S. foreign trade.  Cost effective solutions to remediate contaminated sediments in waterways need to be applied.  Capping is the least expensive remediation alternative available for marine sediments that is unsuitable for open water disposal.  Dredged material capping and in situ capping alternatives, however, are not widely used because regulatory agencies are concerned about the potential for contaminant migration through the caps.  Numerous studies have been conducted on the effects of diffusion through caps, however, there is a lack of experimental data documenting the effects of consolidation induced transport of contaminants through caps. 

This study examines consolidation induced convective contaminant transport in capped sediment utilizing a research centrifuge.  Centrifuge modeling simulates the increase the gravitational acceleration (g) of a prototype which is N times larger than the model, where N is gravitational acceleration factor.  For contaminant migration, the time of travel in the model is inversely proportional to the square of the acceleration factor in the prototype.  In this study, consolidation induced convective transport was modeled for 7 hours at 100-g, which modeled a contaminant migration time of 8 years for a prototype that was 100 times larger than the centrifuge model.  In this study, hydrodynamic dispersion was a function of the seepage velocity.  Thus, advection and dispersion dominated the migration of contaminants.  The centrifuge modeling results were compared to an analytical solution for advection and dispersion. 

Reverse Layering for In-Situ Burial of Nutrient-Rich or Contaminated Sediments

William B. Kerfoot, K-V Associates, Inc., 766 Falmouth Rd., Unit B, Mashpee, MA  02649, Tel:  508-539-3002, Fax:  508-539-3566, Email:  wbkerfoot@aol.com
Stephen G. Seymour, Town of Barnstable, Department of Public Works, 367 Main Street, Hyannis, MA  02601, Tel:  508-862-4086, Fax: 508-862-4711

The novel process of “reverse layering” involves mining sand deposits beneath nutrient-rich or contaminated lake bottom sediments, allowing the bottom to subside and then placing the clean sands on top to bury the sediments in-situ.  The process offers an alternative to current dig, haul, and disposal practices when hazardous materials risk factors are judged to be acceptable.  The Red Lily Pond Restoration Project, being conducted under a state S319 Watershed Nonpoint Source Pollution Grant to the Town of Barnstable, Cape Cod, Massachusetts, uses “reverse layering” to mine clean, medium glacial sands from beneath the lake bottom, transport the sand on top of anaerobic nutrient-rich organic sediments, creating a barrier which suppresses plant re-growth.  To initially deepen the lake, a certain volume of the clean glacial sands (6,000 cy) was diverted to a parking lot for resurfacing.  A specially-constructed barge with A-frame supports at both ends allows intermittent removal of deeper sand and application through sand “sprinklers” to complete burial.  Over 12 inches (.3m) of clean sand is being applied to bury the obnoxious sediments.  Special minicoring procedures were developed to check evenness of sand distribution.  The process requires Army Corps, State Wetlands, Chapter 91, and local conservation commission approval.  The demonstration project involves the lower basin of a 13-acre pond, containing 2-5 meters’ thick sediments, which is underlain by 200 ft. of glacial sands.

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