Geosyntec is a national leader in sediment management, assessment, and remediation. After multiple requests from our clients and colleagues, we have developed this series of sediment-related presentations.
- A Sea Change in Sediment Site Remediation -- It Isn't Just Dredging Anymore
- Robust Delineation of Contamination for Remedial Design Planning to Minimize Project Execution Uncertainties and Project Costs (Don’t be Penny Wise and Ton Foolish)
- Environmental Modeling: Advanced Techniques for Your Litigation Projects
- Helping Mother Nature - Reducing Costs for Managing Contaminated Sediments with Monitored Natural Recovery and In Situ Treatment
- Four Simple Environmental Forensics Methods That Help Clients Target Their Equitable Share of Clean-up Costs
- Polychlorinated Biphenyls: Longstanding and Emerging Challenges
- In Situ Stabilization/Solidification (ISS) for Sediments: A Primer for Client Education
- "When Are You From?" Sediment Coring, Geochronology, and Natural Recovery Can Turn Back the Clock
- Chemical Availability in Sediment -- Are the Right Tools in Your Toolbox?
A Sea Change in Sediment Site Remediation -- It Isn't Just Dredging Anymore
Greg Gibbons, P.E. and Christopher Robb, P.E.
Sediment remediation through dredging and disposal can cost in excess of $500 per cubic yard of material removed, driving the cost for remediation of many sites into the tens or hundreds of millions. Additionally, experience has shown that in many cases, dredging alone does little to reduce risk. New and innovative options are available to successfully reduce risk at impacted sediment sites that are less costly than dredging.
This presentation will provide an overview of four technical approaches that focus on mitigating risk while leaving or treating impacted sediment in place and one administrative option (available in the Great Lakes Region); the technologies include: active capping, in situ stabilization/solidification (ISS), monitored natural recover (MNR), and enhanced monitored natural recover (EMNR). The administrative option is germane to sites along the Great Lakes. The Great Lakes Legacy Act (GLLA) created a cost-share program where non-federal entities can remediate sites collaboratively with the EPA Great Lakes National Program Office (GLNPO), with the federal government paying for up to 65% of the cost of the remediation. Additionally, working collaboratively with EPA in this program has reduced the dredging and disposal costs to an average of $200 per cubic yard total cost for the sites completed to date.
The costs of contaminated sediment projects can rapidly escalate if the site conditions or the sediment characteristics are uncertain. The extent of additional investigations is often minimized after the initial scoping investigation results are reviewed, and projects move ahead to remedial design and implementation, typically before enough facts are known. This tendency of attempting to save money upfront can place the project success in jeopardy because of increased uncertainties. While the highest chance of project failure lies in the remedial action execution phase, there is ample opportunity in the planning, investigation and design phases to reduce uncertainties with the operations and reduce risk of failure during remedial activities.
This presentation will provide examples of how additional delineation would have, or has, improved the volume estimation approaches, remedial technology selection, design and implementation of past projects. In the life-cycle of a sediment remedial project, the highest costs fall into remedial design and implementation. Understanding the extent of contamination within the sediment prism is crucial for project success. These costs can rapidly escalate if the sediment characteristics are uncertain and not understood prior to remedial activities.
Rob Annear, Ph.D., P.E.
Numerical models are increasingly being used to solve environmental problems, resolve conflicts in litigation, develop compliance solutions, and allocate liability in clean-up activities.
Models can be complex tools in litigation related projects and can be used to:
- Settle water rights disputes with hydrology models;
- Develop conceptual site models for CERLCA or RCRA sites;
- Evaluate feasibility alternatives or remedial designs for CERCLA sites using hydrodynamic, sediment transport, and chemical fate and transport models;
- Allocate liability among potentially responsible parties.
This presentation will focus on key aspects of litigation related projects and how numerical modeling can support the projects, including how to work with modelers and get the most out of them, conducting model peer reviews, and challenging numerical models and the modeling results put forth by opposing parties. Numerical models and the experts behind them can be a critical part of a legal defense team.
Tom Krug, P.E., Dave Himmelheber, Ph.D., P.E., and Matt Vanderkooy
Conventional dredging and isolation capping remedies that are often used to address sediment contamination are expensive and can cause the release of contamination during implementation. Monitored natural recovery (MNR) processes can reduce bioavailability and potential risks associated with chemicals at a fraction of the costs of more active remedies. When MNR alone is not sufficient to reduce risks to acceptable levels in required time frames, adding amendments directly to sediment or as a component of a thin-layer cap for in situ treatment can accelerate achieving risk-reduction. This process is known as Enhanced MNR or EMNR.
The use of amendments for in situ treatment as a component of EMNR is rapidly gaining acceptance amongst regulators and other stakeholders. Gaining acceptance for MNR or in situ treatment requires that the physical, biological and chemical processes that reduce the bioavailability or degrade contaminants be well understood, demonstrated and quantified.
This presentation will discuss the types of sites where MNR and EMNR may be applicable, the scientific basis for risk reduction that can be achieved with MNR and the use of sediment amendments and the steps involved in developing arguments to support the use of these lower cost, environmentally beneficial approaches. EMNR has the potential to provide equal or better environmental benefits to dredging and isolation caps at significantly lower cost.
Dogus Meric, Ph.D., and Jennifer Wilkie, Ph.D., P.E.
Each sediment site has a unique history of contamination, discharges, pollutants, and potentially responsible party (PRP) dynamics. As the clean-up costs at currently active sediment mega sites reach into the billions, equitable allocation of these costs among the PRPs has important implications regarding the magnitude of each party's financial liability. Experience has shown that working hand-in-hand with our clients and their legal counsel, and providing advanced forensic lines of evidence to support the legal strategy, often results in early settlements and more equitable clean-up costs.
This presentation will provide an overview of applications, benefits, and limitations of four well-established and scientifically defensible forensic methods that can reveal trends and information previously "hidden" in the existing data, such as fingerprint analysis, advanced statistical analysis, geochronology, and hindcast simulations. Recent case studies will be presented where our use of these forensic methods have reduced our clients’ financial liabilities.
Amanda Hughes, Ph.D.
Polychlorinated biphenyls (PCB) are an anthropogenic group of 209 uniquely structured molecules. Because each molecule is unique, it behaves differently in the environment and the human body. Together these molecules, termed congeners, pose a range of mild to severe human health and ecological risks. The presence of PCB congeners tends to drive clean-ups at many Superfund sites and legal arguments among potentially responsible parties.
In this presentation, the practical challenges that slow or impede PCB clean-ups will be discussed. Such challenges include regulatory and analytical issues, as well as Toxic Substances Control Act (TSCA) regulatory policies that permit continued inadvertent creation and subsequent release of PCBs to the environment. Finally, these issues will be considered in the context of site-specific PCB forensic analyses.
Christopher Robb, P.E.
In Situ stabilization/solidification (ISS) is an innovative and cost-effective alternative for sediment remediation beyond traditional dredging, disposal, and capping. ISS involves solidifying or physically stabilizing an environmental medium (e.g., adding cement to sediment) to encapsulate and immobile contaminants. ISS is an accepted remediation technology for upland sites and is now being adapted as a technique for sediment remediation.
This presentation will discuss what you as a client advocate need to know to intelligently present sediment ISS as an innovative sediment remedial alternative. Topics include an overview of ISS for remediation of contaminated sediments; when, where, and why ISS may be more effective at some sites than dredging, disposal, capping, or monitored natural attenuation; costs associated with ISS; risk management with ISS; and how ISS can be used to supplement traditional remedies.
Peter de Haven, P.E., and Jedidah Sirk, P.E.
Investigations at contaminated sediment sites often generate large quantities of data over lateral and depth extents, thus fulfilling the requirement of delineating contaminant nature and extent and informing the conceptual site model. However, many investigations require additional information related to a fourth dimension – time – typically provided in the form of sediment deposition rates, ages of key historical events, or temporal records of contaminant presence. Defensible, time-related data are an essential line of evidence used in multiple phases of investigation and remediation from site characterization to allocation of responsibility. These uses can include assessing sediment transport processes, supporting assessments of natural recovery, aiding in the calibration and validation of fate and transport models, and providing a timeline of contamination events. Many investigations utilize high-resolution sediment sampling and geochronological analysis to generate these needed data.
This webinar will discuss means and methods of investigations that aid in characterization of sediment deposition history and natural recovery, including the value of careful planning and development of data collection approaches and field equipment, the evaluation of laboratory analytical approaches, and data interpretation methods.
Jason Conder, Ph.D.
Aquatic sediment is a complex environmental matrix composed of a diverse mixture of solids such as minerals, organic matter, and the liquid (sediment porewater) that is present between sediment particles. Both sediment composition and aquatic environmental factors greatly affect the fate of sediment-associated chemicals, which is the conceptual focus of contaminated sediment assessment and management. For example, sediment composition and site-specific conditions often greatly limit the portion of sediment-associated chemicals that are available for uptake by an organism or which are able to dissolve into surface water. Understanding these available portions is not possible by simple chemical extractions that report the “total” concentration of a chemical in sediment, and it has been shown that total concentration analyses greatly overestimate environmental risks and lead to unnecessary or overly-protective sediment management actions.
This presentation will highlight traditional and state-of-the-science approaches for measuring chemical availability in sediment. In addition to presenting the technical details, the approaches will be compared in terms of accuracy and effectiveness, acceptance among regulators and stakeholders, and applicability in risk-based decision-making at contaminated sediment sites.