In 1996, the U.S. Department of Energy (DOE) opened the Environmental Restoration Disposal Facility (ERDF), which began accepting low-level radioactive soils for disposal recovered from waste sites along the banks of the Columbia River in Washington State. Prior to 2009, the site utilized a “dual cell” design. The “dual cell” design comprised of a landfill with baseliner grades that sloped outward from the center of the facility toward the south and north perimeter, producing a mirror image when divided through the center. This design allowed for the landfill to be built in 8-acre phases. A cross-section of the initial design is shown below.
As shown in the figure, the sumps on either end of the cell required monitoring, pumping and mechanical and electrical equipment at either end of the cell. Not shown in the figure is the extensive network of 4- and 6-inch diameter leachate collection pipes.
In 2009, the DOE released additional funds to Washington Closure Hanford (WCH), who manages ERDF, to accelerate the disposal of contaminated materials from the Columbia River Corridor. To complete this, the DOE needed to expand the ERDF. To meet the schedule demands, the DOE incorporated new technologies and used more efficient and cost effective construction and operation methods.
Weaver Consultants Group accomplished the goals set forth in this challenging task through the following design changes:
The single sump design allowed ERDF to decrease the construction time by nearly nine months. The single sump design also decreased the amount of mechanical, electrical, monitoring equipment, monitoring time, and operations and maintenance costs.
The network of 4- and 6-inch pipes was replaced with a single pipe running south to north in the flow line of the super cell.
To meet the more efficient criteria and to allow for a single leachate collection pipe, Weaver Consultants Group designed a synthetic drainage component in the secondary leak detection layer. Additionally, this accommodated the longer drainage flow path realized in the redesign, while also accelerating the construction process.