[Please excuse duplicate postings. - LS]
The Interstate Technology Regulatory Council has just released its Integrated DNAPL Site Strategy, which addresses in a systematic way the cleanup of the nation's most challenging groundwater contamination sites.
EXECUTIVE SUMMARY (initial paragraphs)
Sites contaminated by chlorinated solvents present a daunting environmental challenge. Chlorinated solvents are prevalent and persistent groundwater contaminants, found at tens of thousands of sites worldwide. They also are among the most difficult groundwater contaminants to remediate, especially at sites with dense, nonaqueous-phase liquid (DNAPL) still present in the source zone. Restoring sites contaminated by chlorinated solvents to typical regulatory criteria (low parts-per-billion concentrations) within a generation has proven exceptionally difficult, although there have been successes. Site managers must recognize that complete restoration of many of these sites will require prolonged treatment and involve several remediation technologies. To make as much progress as possible within a generation (approximately 20 years) requires a thorough understanding of the site, clear descriptions of achievable objectives, and use of more than one remedial technology. Making efficient progress requires an adaptive management strategy and may also require transitioning from one remedy to another as the optimum range of a technique is passed. Targeted monitoring should be used, and reevaluation should be done periodically. Managers must implement effective and adaptive treatments that integrate more than one remedy to address complex contamination scenarios.
The ITRC Integrated DNAPL Site Strategy (IDSS) Team intends this guidance document to assist site managers in developing an integrated DNAPL site management strategy containing five key features:
* a conceptual site model (CSM) based on reliable characterization methods and an understanding of the subsurface conditions that control contaminant transport, reactivity, and distribution
* remedial objectives and performance metrics that are clear, concise, and measureable
* treatment technologies applied in sequence or in parallel designed to optimize performance and take advantage of potential synergistic effects
* monitoring strategies based on interim and final cleanup objectives, the selected treatment technology and approach, and remedial performance goals
* reevaluating the strategy repeatedly and even modifying the approach when objectives are not being met or when alternative methods offer similar or better outcomes at lower cost
This document describes key concepts and recent developments in each of these areas to help managers develop successful integrated strategies for chlorinated-solvent sites....