Regulatory strategy

The regulatory strategy for the NNSS was negotiated in the 1990s as a tri­party Federal Facility Agreement and Consent Order (FFACO) between the DOE, the State of Nevada acting through the NDEP, and the US Depart­ment of Defense. The FFACO identifies corrective actions for historical sites of development, testing, and production of nuclear weapons and imple­ments four stages of actions:

1 . Planning of corrective action investigations.

2. Corrective action investigations consisting of site characterization of groundwater contaminated by underground testing and development of flow and transport models to forecast areas of contaminated groundwa­ter over 1,000 years.

3. Model evaluations to test model results sufficient to develop confidence in their application to regulatory decisions required for identified cor­rective actions.

4. Closure in place with development of a long-term monitoring network and local implementation of institutional controls to ensure compliance.

These corrective action stages are referred to as the UGTA strategy and are based on three assumptions (USDOE, 2006). First, remedial actions to remove or stabilize subsurface radiological contaminants are neither tech­nologically feasible nor cost effective. Second, closure in place with moni­toring and institutional control of areas of groundwater contamination is the only practical corrective action. Third, the risk of contaminated ground­water is to workers, and the public. For risk to occur there must be access to contaminated groundwater. As noted in a previous section, there are no natural surface releases of contaminated groundwater on the NNSS. Expo­sure to contaminants requires drilling into and using groundwater from areas of present or future contaminated groundwater, actions which are restricted under current NNSS institutional control policies.

Multiple assumptions under the original FFACO agreement were used to establish the logic of the UGTA strategy. Modeling of groundwater flow and radionuclide transport is assumed to be the most effective way to identify areas of groundwater contamination over 1,000 years. An alternative approach considered during early negotiations of the FFACO agreement was simply locating monitoring wells at the perimeter of the NNSS down gradient of testing areas. The weaknesses of a monitoring-only alternative are the large number of monitoring wells required to effectively implement the strategy and uncertainty in locating monitoring wells; modeling of groundwater flow and radionuclide transport is the primary basis for developing a long-term monitoring strategy. An external peer review panel evaluated the UGTA strategy in 2001 and concluded that the corrective action steps of the UGTA strategy are logical (Institute for Regulatory Science, 2001).

The FFACO agreement assumed there would be sufficient confidence in the model results to support regulatory decisions required to complete the UGTA strategy. The regulatory metric for discriminating areas of contami­nated versus non-contaminated groundwater identified in the FFACO agreement is the radiological standards of the Safe Drinking Water Act (SDWA). This is a widely applied regulatory standard used in groundwater studies by the US Environmental Protection Agency (EPA) and for many sites of environmental remediation throughout the DOE complex. For the UGTA studies, the SDWA is applied to aquifers in a remote arid desert setting, whereas the groundwater protection standards of the SDWA are normally assessed for municipal water supplies. The FFACO agreement requires an assessment of the likelihood of exceeding the radiological standards of the SDWA over 1,000 years.

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