Ribbon NAPL Sampler
Dense Non-Aqueous Phase Liquid (DNAPL) contamination is a high priority problem at many sites. The remediation of DNAPL-contaminated sites is especially critical because DNAPLs in the subsurface represent a long-term source for groundwater contamination. Characterization is essential to the design of effective and efficient remediation solutions. DNAPLs are very difficult to characterize because they are denser than water and migrate due to gravity rather than moving with groundwater flow, as do most contaminants. Standard characterization strategies based on the collection of groundwater samples are not effective at delineating the nature and extent of DNAPL contamination.
The Ribbon NAPL Sampler is a sampling device that provides detailed delineation of DNAPL in a borehole. A dye-impregnated ribbon is installed in a borehole with an inflatable liner. The system is inflated against the walls of the borehole, and the ribbon absorbs the DNAPL that is in contact with the membrane. The dye in the ribbon reacts with the DNAPL, causing a color change. The ribbon is then be retrieved by a tether attached to the bottom. The membrane can be installed with a cone penetrometer truck or with traditional drilling methods.
Limitations and Concerns
The technology should be used to guide and optimize selection of sample locations for chemical analysis.
The use of the Ribbon NAPL Sampler is restricted to sites where the contaminated zone is relatively shallow (less than 150 feet) and is accessible using standard investigatory techniques.
This technology is appropriate only for the in-situ detection of separate phase material because it will not detect high dissolved phase concentrations. It is most appropriate in a situation where detailed information on the depth and distribution of DNAPL is required to support conceptual model development or remedial design.
Technology Development Status
The Ribbon NAPL Sampler is commercially available using conventional drilling techniques. Advances might allow installation to deeper depths and or in other geologic media, such as fractured rock.
Other Resources and Demonstrations
The Ribbon NAPL Sampler has been used successfully for site characterization at the Savannah River Site (SRS), South Carolina; the Cape Canaveral Air Station, Florida; the Paducah Gaseous Diffusion Plant, Kentucky; and the McCormick and Baxter Creosoting Co. Superfund Site, California. The evaluations at SRS focused on the vadose zone. The evaluations at the other sites were used in groundwater.
See http://www.clu-in.org/download/char/542r04017.pdf for a full description of DNAPL characterization Technologies.