The primary objective of this project was to develop and demonstrate the installation and measure the performance of a close-coupled barrier for the containment of subsurface waste or contaminant migration. A close-coupled barrier is produced by first installing a conventional , low-cost, cement-grout containment barrier followed by a thin lining of a polymer grout. The resultant barrier is a cement-polymer composite that has economic benefits derived from the cement and performance benefits from the durable and resistant polymer layer. The technology has matured from a regulatory investigation of the issues concerning the use of polymers to laboratory compatibility and performance measurements of various polymer systems to a pilotscale, single column injection at Sandia to full-scale demonstration. The feasibility of the closecoupled barrier concept was proven in a full-scale "cold" demonstration at Hanford, Washington and then moved to the final stage with a full-scale demonstration at an actual remediation site at Brookhaven National Laboratory (BNL). At the Hanford demonstration the composite barrier was emplaced around and beneath a 20,000 liter tank. The secondary cement layer was constructed using conventional jet grouting techniques. Drilling was completed at a 45" angle to the ground, forming a cone-shaped barrier. The primary barrier was placed by panel jet-grouting with a dualwall drill stem using a two part polymer grout. The polymer chosen was a high molecular weight acrylic. At the BNL demonstration a V-trough barrier was installed using a conventional cement grout for the secondary layer and an acrylic-gel polymer for the primary layer. Construction techniques were identical to the Hanford installation. This report summarizes the technology development from pilot-to full-scale demonstrations and presents some of the performance and quality achievements attained. Use of dual-wall drill pipe to inject two-fluid, thermosetting-polymer grouts was proven to be safe and reliable. Jet grouting was proven to be capable of installing a continuous barrier without affecting the waste form. The demonstration also provided on a proof-of-concept level the ability to emplace a barrier integrity verification system at the site. Excavation, visual inspection and a falling-head permeability test provided positive evidence that the barrier was indeed fault free. All of the project objectives were met for the BNL pit G-11 close-coupled barrier. A closecoupled barrier was successfully installed that achieved all of the performance requirements with no technical complications. Both the close-coupled barrier concept and the use of dual-fluid injection of thermosetting polymers are now considered ready for commercial application.
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government, any agency thereof or any of their contractors or subcontractors. The views and opinions expressed herein do not necessarily state or reflect those of the United States Government, any agency thereof or any of their contractors.
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