New systems tool for groundwater cleanup.

After almost 50 years of nuclear-materials production, the 586-square-mile Hanford facility in southeastern Washington comprises more than 700 waste sites with the potential to release contaminants to the soil and groundwater. These sites vary significantly in their inventories of radioactive and chemical contaminants, as well as in the potential for contaminants to migrate through the soil to the groundwater and the Columbia River. As decision makers investigate cleanup and closure options for Hanford, it is important for them to understand which waste sites have the most significant impact and what the cumulative effects of all the waste sites are.

Researchers at the Department of Energy's Pacific Northwest National Laboratory (PNNL) have developed a comprehensive new tool that will provide federal and state regulators with some of the critical information they need to help protect people, the environment, and the Columbia River.

The System Assessment Capability, or SAC, is an integrated system of computer models and databases that predicts the movement and fate of contaminants in the vadose zone (the soil above groundwater), the groundwater, and the Columbia River. SAC also assesses the impact of contaminants on human health, animals, and the environment.

Instead of showing each waste site in isolation, as has been done in the past, SAC shows the sites in context and in relationship to each other.

A 14-member team of scientists in fields ranging from civil engineering to zoology created the two sets of computer models that are at the heart of SAC. One set simulates the movement of contaminants through the environment. The second set estimates risk and impact from those contaminants.

The environmental model is based on a comprehensive inventory of potential contaminants from Hartford operations as far back as 1944. With information about the quantity and concentration of contaminants at a site, SAC determines the behavior of a given contaminant: how the contaminant will discharge to the soil and move to the groundwater, how it will discharge into the groundwater and, finally, how it will enter the Columbia River. The scenarios are modeled from data about the geology, chemistry, and hydrology of the site. SAC also predicts the consequences of these scenarios for the environment and the impacts of various cleanup options.

Scientists have tested the validity of SAC by comparing SAC results to known plume migrations at the Hanford site over time. The system is an integrated part of DOE's Groundwater Protection Project.

Business inquiries about SAC should be directed to Kathryn Lang at [phone]. Business inquiries on other PNNL research and technologies should be made by phone to (888) 375-PNNL or by e-mail to [e-mail].