Design of a Permeable Treatment Wall to Passively Remove Radioactive Strontium (Sr-90)
from Groundwater beneath a former Commercial Nuclear Fuel Reprocessing
Facility in West Valley, New York
By Richard Frappa, PG(1)
AMEC Geomatrix (AMEC) has designed a “first in the world” continuous in situ permeable treatment wall (PTW) intended to remove radioactive strontium-90 (Sr-90) from groundwater at a former commercial nuclear fuel reprocessing and vitrification test site in western New York that is in the early stages of site decommissioning. AMEC engineers and geologists in Oakland, California and Buffalo, New York have collaborated with researchers at the State University of New York at Buffalo (UB) to design an approximately 850-foot (260 meter) long by 3-foot (1meter) thick zone of granular zeolite (composed of approximately 85 to 90% of the mineral clinoptilolite obtained directly from a mine in southern Idaho) that will remove Sr-90 in situ from groundwater through ion-exchange reactions; the anticipated life of the system is at least 15 years. The innovative design calls for the use of a one-pass trencher to simultaneously remove unconsolidated aquifer material composed of glaciofluvial-derived silt, sand, and gravel and replace the excavated zone with zeolite along the entire alignment while keying the PTW 3 feet (1 meter) into the underlying low-permeability till; the system will be installed from ground surface to depths of about 20 feet (6 meters) to 30 feet (9 meters) below grade. The design of the full-scale PTW, which involved multiple years of engineering work, site characterization, numerical modeling, and evaluation of laboratory treatability studies at UB, also includes substantial engineering of the site’s surface-water management system as well as road realignment work to allow the PTW construction to take place.
AMEC staff have been working for the site – known as the West Valley Demonstration Project –for approximately 15 years evaluating remedial alternatives, performing detailed hydrogeologic characterization, and evaluating the pilot PTW system installed in 1999. The success of the PTW project is seen as key to advancing both the USDOE remediation program, as well as the State of New York’s approach to environmental remediation. The project has support from the American Resource Recovery Act of 2009 (US Federal Stimulus Funding program).
Rick Frappa is a Principal Hydrogeologist and Vice President at AMEC Geomatrix, Inc. An alumnus of the UB Geology Department (1985 BA; 1987 MA), he has worked as an environmental consultant for the past 23 years. He focuses his practice area toward characterization and remediation of sites having complex hydrogeology.
