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Mechanical blending of contaminated soil with amendments has recently reemerged as an important treatment technology. From its original application using large‐diameter augers in the early 1990s to the current use of rotary drum blenders, soil blending is being used as an alternative to other remediation technologies like amendment injection and soil vapor and groundwater extraction. Shallow (approximately 10 m below ground surface [bgs] or less) soil blending also offers an alternative to excavation and disposal. Soil blending has been used to remediate a site with various contaminants including, but not limited to, chlorinated solvents, petroleum, and metals. The types of soils susceptible to soil blending vary from sands and gravels to silts and clays to fractured rock and combinations of all of these. The types of amendments blended include oxidants, reducing agents, biological enhancements, and stabilizing amendments. Soil blending systems deliver the power to the mixing head to adequately mix the soil and amendment to enhance remediation effectiveness. Since long‐term contamination is often a result of heterogeneously distributed residual contaminant in localized source zones that are difficult to access, the typical aim of soil blending is to homogenize the soil while effectively distributing amendment to these zones made accessible by blending. By effectively homogenizing the soil, however, soil blending will increase the void ratio and disrupt the shear strength and bearing capacity of the soil so an important component of a soil blending technology is proper recovery of these geotechnical parameters. This can be achieved by using well‐known soil improvement techniques such as amending all or a portion of the blended area with Portland cement or lime. Several case studies of soil blending treatments of different contaminants and amendments in various soil types are provided.

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Innovative site characterization and monitoring technologies are integral to the objective of reducing environmental restoration costs and long-term, post-closure monitoring. As pan of the Department of Energy's (DOE) Integrated Demonstration Program at the Savannah River Site (SRS), new technologies in the areas of drilling, characterizatio_t, monitoring, and remediation are being demonstrated and evaluated for their technical performance and cost effectiveness in comparison with baseline technologies. Present site characterization and monitoring methods are costly, time-consuming, overly invasive, and often imprecise. Better technologies are required to accurately describe the subsurface geophysical and geochemical features of a site and the nature and extent of contamination. More efficient, nonintrusive characterization and monitoring techniques are also necessary for understanding and predicting subsurface transport. DOE is focusing on site characterization, sampling, and monitoring as areas in which significant technological advances are possible. Relatively small investments in better characterization and monitoring systems will provide cost payback many times over. This report summarizes the results of field demonstrations of technologies that address the measurement of both physical and chemical parameters related to subsurface characterization and monitoring as well as in situ sampling methods. Several different platforms were targeted for the deployment of these sensors including placement directly in the subsurface, in wells, and at the surface.The following three categories of instruments have been demonstrated as part of the DOE's OTD integrated demonstrations: • instruments that monitor physical parameters by measuring surrogate parameters i.e., colloidal panicle movement (ORNL colloidal borescope) or temperature change (SNL In Situ Permeable Flow Sensor) for groundwater flow velocity; electrical resistivity (LLNL Electrical and electromagnetic tomography) or seismic velocity (SNL Seismic Tomography) for three dimensional imaging of saturation changes. • instruments that capture liquid (BNL Multilevel Mechanical and Membrane Samplers) or vapor (ORNL Arrayed Vadose Zone Sampler) subsurface samples with minimal invasiveness • instruments that analyze chemical concentration (LLNL Fiber Optic TCE Sensor for remote detection of vapor-phase TCE and chloroform in a borehole; SNL Portable Acoustic Wave Sensor for the detection of vapor-phase contaminants; PNL Halosnif for the detection of vapor-phase chlorinated organic species; ORNL Direct Sampling Ion Trap Mass Spectrometer for compound specific determination of contaminants in the vapor, liquid, or solid phases). All of the technologies were successful in completing the sampling or monitoring objectives of their field demonstrations. Many of the technologies are licensed to private industry and all are mature enough to begin technology transfer and to initiate progress toward regulatory acceptance. Not only are several of the technologies cost competiti...