100-D Area
In the 100-D Area, measures have only recently been completed to remove the high-risk waste sites
responsible for the chromium groundwater plume. Additional time is needed to evaluate the
effectiveness of these efforts, but there is no reason to believe that these actions would
be any less effective than the measures used in the 100-H Area to eliminate future releases
to the groundwater.
In addition to the pump-and-treat system used to capture the chromium plume from 100-D Area
before it reaches the Columbia River, a second more concentrated region within the plume is also
undergoing treatment using an in situ treatment to reduce the toxicity and mobility of chromium
already in the groundwater. This technique, called in situ redox manipulation, causes the
mobile chemical species chromate to be chemically reduced to a less mobile form. Chromium
concentrations in the plumes beneath 100-D Area will require continued treatment for some time
into the future, but it is anticipated that achieving the remedial action objectives for this
plume is likely after all source actions are complete by 2010.
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