DOE’s cleanup plans for the River Corridor are based on the Comprehensive Environmental Response, Compensation and Liability Act of 1981 (CERCLA). In 1991, DOE, the U.S. Environmental Protection Agency (EPA), and the Washington State Department of Ecology agreed that interim remedial actions in the 100 and 300 Areas would fulfill a “bias for action” approach to CERCLA and could be implemented relying on streamlined qualitative risk assessments rather than a quantitative baseline risk assessment. Waste site cleanup under interim action Records of Decision (RODs) was initiated during the mid-1990s and is planned for completion by WCH by 2015. The current focus of WCH is on completing the remedial actions in order for the Tri-Parties to proceed to final CERCLA closeout of the 100 and 300 Area Operable Units.
A critical step in developing final remedial action decisions (final RODs) and proceeding toward final CERCLA closeout is completion of a quantitative baseline risk assessment, which is now being performed by WCH as the River Corridor Baseline Risk Assessment (RCBRA).
The RCBRA uses a multi-step process in accordance with guidance established by the EPA. The process begins by compiling and summarizing the existing data, then using the data quality objectives (DQO) process to identify data gaps and unresolved issues through workshops, soliciting and incorporating input from regulatory agencies, the Natural Resource Trustee Council, Tribes, and stakeholders. Based on these discussions, sampling and analysis plans are developed to collect the data needed to fill gaps and address the issues. After all of the necessary data are collected, the risks to human health and the environment are assessed and characterized.
To begin the process, a pilot risk assessment study of residual contaminants was initiated in 2002 at the 100-B/C Area (located in the 100 Areas). The pilot risk assessment helped to refine the approach for application to the remainder of the River Corridor. After completion in 2005, the pilot was immediately followed by sampling of upland and shoreline environments within the 100 and 300 Area reactor/operational areas. At this point, the task was identified as the “100 Area and 300 Area Component” of the RCBRA. The RCBRA study scope was amended during the first year of field sampling to include the shoreline regions between the operational areas, referred to as the “Inter-Areas.” The assessment scope was further amended in 2007 to include assessment of potential risks resulting from groundwater contamination.
These combined elements of the risk assessment task (100/300 Area Component, Inter-Areas, and groundwater) are now collectively referred to as the RCBRA Source and Groundwater Component. Field collection for the RCBRA Source and Groundwater Component concluded in 2007 and included soil, river sediment, water and biota samples.
When complete, this baseline risk assessment will provide a complete analysis of residual human health and ecological risk in the river corridor. Results from the RCBRA will be used in the remedial investigation and feasibility study (RI/FS) activities. Similar to the RCBRA, the RI/FS work integrates the River Corridor source and groundwater operable units by the following decision areas: 100-B/C, 100-D/H, 100 K, 100-N, and 100-IU-2/100-IU-6/100-F, and the 300 Area.
The purpose of the RI/FS step is to gather information to characterize the nature and extent of contamination, quantify risks posed by remaining contamination, and support selection of the final remedies (final records of decision) to complete cleanup. The need for additional field characterization in the River Corridor to supplement existing information was established through a “systematic planning” process. Systematic planning is a tool used to define a conceptual site model, identify specific information needs regarding the nature and extent of contamination, and to identify a strategy for completing the CERCLA process.
In cases where systematic planning identifies a need for analytical data, the process incorporates the identification of data quality objectives, which in turn support development of field sampling plans for each decision area. A field sampling design and a work plan document will be generated for each decision area.
Ultimately, the combined existing and new characterization information will support final risk-based decisions regarding (1) the need for further remedial actions, and (2) the selection of appropriate remedial actions where needed within each of the decision areas included in the River Corridor to protect human health and the environment. Recommendations for these final cleanup decisions will be presented by the Tri-Parties to the public for consideration in a proposed plan for each decision area.
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