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Joining forces to clean up the subsurface

September 2011

Unraveling the complexities of contaminants threatening the groundwater beneath the Hanford Site in Eastern Washington is not a one-man job.

Many different organizations, including multiple agencies in the U.S. Department of Energy (DOE) and several of its contractors are investing in a collaborative effort to address the unique challenge of cleaning up the deep vadose zone beneath the Hanford Site.

Most of the subsurface contamination at the Hanford Site lies in the vadose zone. Latin for "shallow," the vadose zone is the portion of the subsurface between the ground surface and the water table. The vadose zone is over 300 feet thick near the center of Hanford, where a significant amount of liquid waste disposal took place from the mid-1940s to the 1980s.

The vadose zone is important because it marks the upper boundary of the underlying aquifer. Therefore, whatever contamination passes through it will enter the aquifer. Water in this aquifer eventually discharges to the Columbia River bordering the Hanford Site.

At the Hanford Site, the vadose zone consists of a complex mixture of sediment layers that, in many places, are now contaminated with radionuclides, metals, and hazardous chemicals.

In many cases, there is little documentation about the amount and type of waste released into the ground. Additionally, our understanding of the key geochemical, biological, and hydrologic processes that affect contaminant movement is not sufficient to reliably predict the location, transport, and fate of contaminants through the subsurface. These unknowns also make it difficult to design, deploy, and monitor the performance of remediation techniques intended to stabilize or remove contaminants found in the vadose zone.

Available cleanup technologies are insufficient to remediate many of the groundwater and vadose zone contaminant issues facing Hanford and other DOE sites. And no single organization has sufficient financial or technical resources to solve these basic scientific and engineering deployment challenges.

The Deep Vadose Zone Applied Field Research Initiative

DOE is investing in a collaborative effort, called the Deep Vadose Zone Applied Field Research Initiative (DVZ-AFRI), to address the unique challenge of cleaning up the deep vadose zone. Led by Pacific Northwest National Laboratory, the Initiative brings together the resources and creativity of several DOE offices, contractors, and national laboratories to integrate their activities into a focused effort to solve deep vadose zone challenges.

The goal of the DVZ-AFRI is to ensure long-term protection of groundwater by developing effective and innovative solutions to deep vadose zone challenges. The Initiative will focus on characterization, predictive modeling, remediation, and monitoring of persistent and high-risk contaminants at the Hanford Site in Richland, Wash. Remediation solutions developed during this process will transform vadose zone cleanup and provide a scientific foundation supporting sound remedial decisions that meet cleanup goals.

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