other remediation technologies should be expanded to integrate compound-specific isotope analysis and molecular biological methods with more conventional biogeochemical characterization and groundwater dating methods. The development of molecular and isotopic diagnostic tools has significantly enhanced the ability to evaluate the performance of degradation technologies and monitored natural attenuation at complex sites.
Although the Committee did not attempt a comprehensive assessment of research needs, research in the following areas would help address technical challenges associated with long-term management at complex contaminated sites (see Chapter 6 for a more complete list):
• Remediation Technology Development. Additional work is needed to advance the development of emerging and novel remediation technologies, improve their performance, and understand any potential broader environmental impacts. A few developing remediation techniques could provide more cost-effective remediation for particular combinations of contaminants and site conditions at complex sites, but they are in the early stages of development.
• Tools to Assess Vapor Intrusion. Further research and development should identify, test, and demonstrate tools and paradigms that are practicable for assessing the significance of vapor intrusion, especially for multi-building sites and preferably through short-term diagnostic tests. Development of real-time unobtrusive and low-cost air quality sensors would allow verification of those short-term results over longer times at buildings not needing immediate mitigation.
• Modeling. Additional targeted modeling research and software development that will benefit the transition of sites from active remediation to long-term management should be initiated. Particular needs include concepts and algorithms for including the processes of back-diffusion and desorption in screening and plume models, and the development of a larger suite of intermediate-complexity modeling tools to support engineering design for source remediation.
Overall research and development have been unable to keep pace with the needs of practitioners trying to conduct remediation on complex sites. Currently, a national strategy for technology development to support long-term management of complex sites is lacking. It is not clear that the pertinent federal agencies will be capable of providing the funding and other support for the fundamental research and development that is necessary