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What Lies Beneath

PNNL team helps DOE meet key subsurface cleanup milestone at Hanford

October 2015
 What Lies Beneath
Controlling geochemical processes, as illustrated in this schematic, are expected to play a key role in radioiodine transport through the Hanford subsurface. The UP-1 technical evaluation plan outlines potential pathways for remediating iodine-129 contamination in the subsurface as part of the Hanford cleanup mission.
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In a key step toward remediating soil and groundwater contamination from Cold War efforts at the Hanford Site in Richland, Wash., PNNL researchers recently completed a draft technology evaluation plan for iodine-129 at the Hanford Site's 200-UP-1 Operable Unit (OU). Draft A of the plan will be submitted to the Department of Energy and Environmental Protection Agency in early November for review, meeting an important DOE Richland Operations Office milestone 10 months ahead of schedule.

Iodine-129 is a key contaminant of concern at Hanford because of its long half-life, high mobility in groundwater, and long-term risk to human health and the environment. The plan outlines an approach for DOE and EPA to take in evaluating technologies for remediating iodine-129 contamination in the subsurface. In preparing the plan, researchers:

  • updated critical biogeochemical information that was not available for previous studies
  • reviewed regulatory guidance for iodine-129
  • identified processes that control iodine-129 fate and transport in the environment
  • developed an updated conceptual model for iodine-129 in the 200-UP-1 OU
  • evaluated the exposure risk from iodine-129
  • reviewed remediation options for both vadose zone and saturated zone iodine.

In completing the draft plan, Hope Lee, PNNL's principal investigator for this effort, worked closely with the site’s cleanup contractor, CH2M Hill Plateau Remediation Company (CHPRC). She expects that PNNL will conduct the follow on remedial investigation over the next ~5 years and work with CHPRC to support the feasibility study. PNNL also plans to develop a conceptual model of iodine behavior—a critical first step in understanding iodine in the subsurface to better predict its risk and long-term impact to groundwater.

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