Corrective Action Strategy
Corrective Action Strategy & Descriptions of the Four Categories of Corrective Action Units
Appendix VI to the Federal Facility Agreement and Consent Order describes the strategy that was/is used to plan, implement, and complete environmental corrective action activities, overseen by the NDEP, at facilities where nuclear-related operations were conducted in Nevada.
The corrective action strategy was/is based on four steps:
(1) identifying corrective action sites (CASs),
(2) grouping the corrective action sites into corrective action units (CAUs),
(3) prioritizing the corrective action units for funding and work, and
(4) implementing the corrective action investigations and/or corrective actions, as applicable.
Corrective action sites are broadly organized into four categories based on the source of contamination: (1) Industrial Sites, (2) Underground Test Area (UGTA) Sites, (3) Soils Sites, and (4) Off-Sites. The corrective action sites located on the NNSS and TTR where activities were conducted that supported nuclear testing activities are grouped under Industrial Sites. The CASs associated with underground nuclear tests that have resulted or might result in local or regional impacts to groundwater resources are grouped as the UGTA CAUs. The CASs where tests resulted in extensive surface and/or shallow subsurface contamination are grouped as Soils Sites CAUs. Both surface and subsurface CASs/CAUs are associated with the underground nuclear testing at the Off-Sites, CNTA and PSA.
Industrial Sites— These sites included, but were not necessarily limited to, landfills, mud pits, leachfields with or without radiological contamination, or discarded or abandoned materials such as drums, batteries, and lead materials. Approximately 2,000 Industrial Sites have been identified under the FFACO process. To date, two (2) Industrial Sites CAUs remain to be closed. All other Industrial Sites CAUs sites have either been clean closed or closed in place with use restrictions dependent on future land use.
Underground Test Area (UGTA) Sites — The UGTA strategy is illustrated on Figure 3-2 in Section 3.0 of Appendix VI of the FFACO. Three assumptions for the UGTA strategy are described in the Nevada Test Site Environmental Management End State Vision, (see pdf document on pg. 52). The first assumption is that groundwater technologies for removal or stabilization of subsurface radiological contamination are not cost effective. Second, because of these high remediation costs, closure in place with monitoring and institutional controls is the only likely corrective action. Finally, the important potential risks from radiological contamination of groundwater are to workers, the public, and the environment; and exposure to these risks requires access to groundwater.
The technical basis for achieving the UGTA strategy is through an evaluation of each UGTA CAU using a combination of approaches, including the following:
- Data collection consisting of, but not limited to, drilling exploration, hydrologic testing, and field and laboratory studies designed to characterize the hydrogeological setting.
- Modeling of the hydrogeological setting, the radiological source term, and flow and contaminant transport to forecast areas of current and future contamination for 1,000 years.
- Iterative model evaluations and monitoring of groundwater near and downgradient of areas of past underground testing.
- Identification and documentation of land-use policies (institutional controls) designed to restrict future public access to groundwater contaminated by underground testing.
This four-component approach is used to accomplish the primary objective of the UGTA strategy, which is defining perimeter boundaries for each CAU over the next 1,000 years. The perimeter boundaries will enclose areas potentially exceeding the radiological standards of the Safe Drinking Water Act (SDWA) (CFR, 2010). Confidence in model results will be developed through model evaluation and monitoring studies, and the uncertainty in model forecasts will be managed through institutional control of areas of potential groundwater contamination.
The NNSA/NSO and NDEP continue to evaluate technological advances in groundwater remediation during the life cycle of the UGTA Activity, and significant changes in technology and/or the cost of remediation alternatives could lead to a reevaluation of the assumptions of the UGTA strategy.
Soils Sites — Soils Sites CASs consist of surface and shallow subsurface soil contamination resulting from various types of nuclear experiments or testing; these sites are situated throughout the NNSS, NTTR, and TTR. Testing types include atmospheric tests (including airburst, air drop, balloon, rocket, surface, and tower tests), shaft tests, safety experiments and storage transportation tests, cratering and plowshare tests, and hydronuclear tests. The closure process for contaminated surface soils will likely vary for sites depending on whether they are on or off the NNSS.
For example, DOE has committed to characterize and remediate radioactive contaminated surface soil plumes that straddle or lie outside NNSS boundaries such as sites on the TTR or the NTTR. These sites would be remediated and then made available for alternative "controlled" uses. Cleanup levels would generally respond to future military missions and DOE related research and development activities. State officials recognize that "clean closure" of these sites would be cost prohibitive and generally impractical given both current and expected land uses.
For the majority of contaminated soils located within NNSS boundaries, DOE and NDEP agree that it is not economically realistic to clean close the majority of these sites, especially while the NNSS remains under DOE control and will not be released to the public. The surface contamination has been demonstrated to be very immobile and closure work on the various sites has demonstrated that there has been little if any migration of surface contamination over the years. Both parties understand that if that situation were to change, every closed site would be re-evaluated in light of the new conditions.
Off-Sites — DOE removed all surface contamination and the NDEP approved a Closure Report in February 1998 stating no post-closure monitoring is required and no land use restrictions apply for the surface CAU at the PSA site. Identified surface CASs at CNTA were closed using a variety of methods, including removal, capping, fencing and/or institutional controls. Surface cleanup at CNTA was completed in 2001. The DOE continues to monitor the long-term performance of the surface cleanup at the CNTA bi-annually and submits a bi-annual Report to the NDEP. Surface contamination at these two Off-Site underground nuclear test areas was limited to non-radioactive constituents such as heavy metals, fuel oils, etc.
The DOE and NDEP continue to characterize the nature and extent of the subsurface at and both the PSA and CNTA sites. Use Restrictions exist at both the sites to prevent excavation, drilling and removal of material from the subsurface. More information on the Nevada Off-Sites may be found on the DOE/LM website.