This Hot Topic offers a remedy selection framework to help project managers evaluate remedial technologies and develop remedial alternatives (often composed of multiple technologies) based on site-specific data. General categories of contaminated sediment remedial technologies include monitored natural recovery (MNR) and enhanced monitored natural recovery (EMNR); in situ treatment; capping (conventional and amended); and removal (dredging and excavation).
Remediation of contaminated sediments commonly targets the complimentary goals of protecting human health and the environment and restoring impaired environmental resources to beneficial use. Although the selection and implementation of sediment remedies can be straightforward for simple sites, many contaminated sediment sites are challenging from a technical and risk-management perspective.
The remedy evaluation framework presented here assists in selecting remedial technologies and evaluating remedial alternatives that are applicable to contaminated sediment sites based on site-specific conditions.
Monitored natural recovery (MNR) is defined as a remediation practice that relies on natural processes to protect the environment and receptors from unacceptable exposures to contaminants. Enhanced MNR (EMNR) applies material or amendments to enhance these natural recovery processes.
In situ sediment treatment involves applying or mixing of an amendment into sediments. In situ treatment technologies can achieve risk reduction in environmentally sensitive environments such as wetlands and submerged aquatic vegetation habitats, where sediment removal or containment by capping might be harmful.
Capping is the process of placing a clean layer of sand, sediments or other material over contaminated sediments in order to mitigate risk posed by those sediments. The cap may also include geotextiles to aid in layer separation or geotechnical stability, amendments to enhance protectiveness, or additional layers to armor and maintain its integrity or enhance its habitat characteristics.
Dredging or excavation remedies remove contaminated sediment from freshwater or marine water bodies in order to reduce risks to human health and the environment. Removal is particularly effective for source control (mass removal of hot spots) but potentially less effective for overall risk reduction because of resuspension and residual contamination.
Monitoring data collected before, during, and after remediation provide an objective basis for evaluating remedy performance and effectiveness. Monitoring data are used for gauging progress towards meeting the RAOs and determining whether further remediation or a change to the current remedy is required.
ITRC Sediment Team