EPA releases SITE evaluation report on AquaBlok sediment capping technology
• Report indicates AquaBlok provides material properties superior to traditional sand capping approach in physical stability and reduced permeability or seepage through the capping material
TOLEDO, OH, Dec. 20, 2007 -- AquaBlok Ltd., a manufacturer of innovative clay-based composite materials, has announced the release of the final report authored by the U.S. EPA's National Risk Management Research Laboratory, Office of Research and Development.
A program of the U.S. Environmental Protection Agency (EPA), referred to as the Superfund Innovative Technology Evaluation (SITE) Program, evaluated the effectiveness of AquaBlok® as an innovative contaminated sediment capping technology in the Anacostia River in Washington, DC. Contaminants in the sediment of the Anacostia River include polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), heavy metals, and other chemicals to levels that generally exceed regulatory standards. Performance of an AquaBlok® cap was monitored over an approximately three year period using a range of invasive and non-invasive methods.
A comparison of AquaBlok® to a traditional sand cap was made relative to the following three basic objectives:
1. Assess the physical stability of AquaBlok® relative to a traditional sand cap,
2. Determine the ability of AquaBlok® to prevent hydraulic seepage compared to traditional sand cap material,
3. Evaluate the impact of AquaBlok® on benthic habitat and ecology relative to traditional sand cap material and conditions in the native river system.
The conclusion of the evaluation, from the abstract of the report is as follows:
"The overall results of the AquaBlok® SITE demonstration indicate that the AquaBlok® material is highly stable, and likely more stable than traditional sand capping material even under very high bottom shear stresses. The AquaBlok® material is also characteristically more impermeable, and the weight of evidence gathered suggests it is potentially more effective at controlling contaminant flux, than traditional sand capping material. AquaBlok® also appears to be characterized by impacts to benthos and benthic habitat generally similar to traditional sand capping material."
A range of unique and important measurement methods were employed during the evaluation to support the conclusions of the report. Two such measurements related to stability of the capping material against flow or sheer stresses and seepage through the cap.
To evaluate the stability of the material a novel "SedFlume" approach, specifically designed for testing of core samples of sediments, was performed by an independent source.
Since AquaBlok is considered a low-permeability capping alternative to traditional sand caps, both hydraulic conductivity (K) measurements and seepage information collected from the field were considered to be key measurements for the evaluation. While the hydraulic conductivity is a standard measure, the seepage data was collected from the river with specialized ground-water seepage meters adapted to provide continuous measurement of aqueous flux through the sediment cap at high resolution over an extended period of time.
Recovery of benthic habitat and ecology in the capped area is also of primary interest in the evaluation and application of sediment remediation management options.
The report also provides a detailed framework for estimating and evaluating the economics of AquaBlok as a Sediment remediation management approach. It is believed that this report will be invaluable to regulators and engineering firms that are charged with implementation of the EPA Sediment Management Guidelines, released in Dec. of 2005.
To access the full report, see: http://www.epa.gov/ORD/SITE/reports.html
AquaBlok Ltd. is a manufacturer of composite (clay-based) materials utilizing its patented coating and amendment approach. The company has a long history in the environmental industry and a range of products utilized in sediment remediation technologies.
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