CASE CLOSURE STRATEGIES
Regardless of the contaminant, the ultimate goal of environmental cleanup activities is site restoration of contaminated soil and water, case closure, and productive reuse of the impacted property. Sadly, many of contaminated sites take decades and millions of dollars to close. Over the past four decades since the establishment of significant environmental protection legislation and regulations protecting soil and water resources, major changes in the understanding of exposure pathways, health risks and toxicology have made low risk closure possible for countless properties. More recently, development of innovative engineering remediation techniques have allowed for lower costs and more efficient site cleanup than ever before. At the same time, improved analytical science has allowed for lower and lower laboratory reporting levels, now in the parts per trillion. Even with these significant technical improvements, case closure is sadly quite elusive for many property owners where sites overseen by agencies ranging from the U.S. Environmental Protection Agency, the state water boards to even local fire departments or environmental health departments, take decades to assess, remediate and close, regardless of contaminant.
Within the past two decades, the focus of corrective actions has shifted away from trying to remove the maximum amount of contamination possible, regardless of cost, to determining how much contamination could be safely left in place while protecting human health and ecological resources. Throughout the nation, there are many variations to the historical, legal and policy background to regulatory requirements. New models and recommended best practices for assessment and remediation, sustainable development and brownfields reuse are also being developed.
Closure concepts related to risked based corrective action are commonplace. More recently, technical impracticability is favored as some remedial methods have technical limitations in certain circumstances or will not provide a significant benefit. These deviations from earlier closure models are derived from the hard reality of decades of remediation experience that the restoration of heavily contaminated industrial properties to pristine environments is not possible, even with abundant funding. In an age of limited funding by either public or private sector, one has to assess which resources one is trying to protect and the cost of replacing those resources.
Realistic case closure strategies rely on developing a logical and sustainable method of protecting the health of the public, wildlife and the environment while maintaining needed water resources for future generations. The case closure strategies usually are developed using an aggressive treatment of the source zone in soil and groundwater (See Brewer and Jacobs work on Remediation Management Zones) and less emphasis on the residual zone. In some cases, drinking water will never be used due to the high total dissolved solids or high naturally occurring salinity in the shallow water. Calculating the environmental footprint of soil remediation projects, it is apparent that in some cases, more air pollution will be generated and fuel consumed by excavating the impacted soil and transporting the soil to the landfill than leaving the soil in place and treating the contaminants with in situ remedial methods.
On project timing issues, case closure strategies are best evaluated in the beginning of the life of the project, after the site conceptual model has been developed and discussed with the regulators, owners and stake holders. This requires significant groundwater, soil and sometimes soil vapor data of the contaminant, as well as a good understanding of the fate and transportation of the target chemicals. From this information, contaminant closure goals can be developed, and a master plan for closure can be established.
Case Closure Example — Revisiting a Closed Site: Expedited Treatability Testing and High Pressure
Injection of Activated Sodium Persulfate to Move Site toward Closure, Again
For more information on case closure strategies, please contact Jim Jacobs at 415-381-5195 or jimjacobs@ebsinfo.com
