Presentation Description
Managing DNAPL in Sediments
This paper will present an overview and analysis of two separate installations where alternative cap designs were implemented to limit the impact of DNAPL (coal tar) on sediments in a creek and canal setting.

The first site is Chattanooga Creek, a NPL site that resulted from historic manufacturing activity that produced significant non-aqueous phase liquids (NAPLs).  The site is next to a low, marshy natural area, which includes oxbow remnants of the former creek channel, and is an area of significant natural resource value.  A low permeability, clay-based capping material called AquaBlok was selected as a barrier to minimize the potential for future migration of contaminants into the creek system (which empties directly into the Tennessee River) and to facilitate the restoration of the oxbow area as a beneficial natural feature.  a site overview, and extensive practical information on installation, handling and quality control aspects of the selected remediation solution.  The regulatory perspective will be presented as well.

The second site is a canal located adjacent to the Hudson River in New York State.  Sediments at the site have been impacted by a historic manufactured gas plant (MGP).  Remediation of the upland plant location was completed and there was a desire to provide an active cap on the adjacent canal sediments to minimize the potential of sheens that may result from residual seeps from the existing sediment.  An active treatment layer of organoclay was placed in a thin, uniform layer below a continuous, low permeability cap.  In this configuration, contaminants that pass through the thin treatment layer are re-directed in a horizontal direction along the low permeability cap to more fully utilize the treatment layer with any residual solutes transported vertically through the horizontal barrier by molecular diffusion.  Information on the approach and design implemented will be presented.