100 Area Completion Strategy and Commitments

The basic strategy in the Tri-Party Agreement cleanup plan for the River Corridor is to pursue source control measures on an area-by-area basis. The sequence and the timing for completion of source control actions for the individual reactor areas are as follows:

• B/C Area - December 2006
• F Area - December 2008
• H Area - December 2010
• D Area - December 2011
• K Area - December 2012
• N Area - December 2012

Upon completion of these source control actions, DOE is required to submit closeout verification packages for each waste site, pipeline, or unplanned release. Those packages are then consolidated into reports that document these actions achieved the required degree of cleanup. The only requirement is that these reports be submitted in a " timely manner" on an area basis to support the development of a final record of decision for the entire 100 Area. In addition to source control actions, baseline risk assessments will also be developed on an individual reactor basis to support the final 100 Area Proposed Plan and Record of Decision. The commitments to develop a baseline risk assessment for the 100-B/C Area is contained within the River Corridor tentative agreement and will serve as a template for the other reactor areas.

The schedule for the pilot study of the 100 B/C Area risk assessment is to complete the data quality objectives process in 2002, perform data collection in 2003 and 2004, and submit the 100-B/C Area Risk Assessment Pilot Study Report in July 2005. Based on this schedule, the table below provides consistent schedules for each of the other areas.

With many of the most significant sources of groundwater contamination already subject to ongoing remedial action, it is anticipated that groundwater plumes for chromium and other mobile contaminants should begin to attenuate. For the 100-B/C Area and the 100-F Area, where no interim actions were taken, chromium concentrations should meet remedial action objectives through monitored natural attenuation, which will protect the Columbia River ecosystem, achieve drinking water standards, and return the area to potential future use status well before 2012.

During the year following completion of the source control actions in each of the areas, groundwater monitoring and well decommissioning activities are scheduled. The goal of these efforts is to upgrade the monitoring networks to meet the requirements for long-term stewardship and issue an approved operations and maintenance plan for each groundwater operable unit. Similar efforts will be needed to develop a long-term environmental monitoring plan to assess the continuing impact of residuals left after source actions are complete.

The last commitment in the River Corridor tentative agreement is to "Submit a schedule and establish commitments to complete the Remedial Investigation/Feasibility Studies and Proposed Plans in support of the Final Record of Decision for the 100 Area." The 100 Areas study should not represent a major new characterization initiative, but a compilation of data gathered during source control actions, reactor risk assessments, ongoing groundwater monitoring, spring sampling, and Columbia River monitoring as well as the annual groundwater remedial action reports. These data should provide the information required to make the final decision for the 100 Areas.

Other commitments also may influence the scope and the timing of future work. For example, the next CERCLA five-year review could alter the scope and timing of work. The next review may generate additional work if it is determined that remedies are not meeting their remedial action objectives; or, if the remedies are meeting these requirements, it may mean that remedial actions may move to a monitored natural attenuation remedy. The next CERCLA five-year review should be prepared in 2005/2006, and DOE and the Hanford Site contractor will prepare it for submittal to EPA.

Efforts to evaluate alternatives to pump-and-treat systems like those described for N Springs may also provide opportunities to refocus groundwater protection priorities. In these instances, care must be taken to ensure appropriate documentation exists to support a change in the response action. Without appropriate documentation, changes to these actions may create noncompliant conditions when compared to remedial action objectives during the next CERCLA review.

For questions or comments, please send a message to Carl Connell.