Corrective Action Decision Document/Closure Report for Corrective Action Unit 374: Area 20 Schooner Unit Crater, Nevada National Security Site, Nevada with ROTC 1 and 2, Revision 0

Abstract

Corrective Action Unit 374 comprises five corrective action sites (CASs): • 18-22-05, Drum • 18-22-06, Drums (20) • 18-22-08, Drum • 18-23-01, Danny Boy Contamination Area • 20-45-03, U-20u Crater (Schooner) The purpose of this Corrective Action Decision Document/Closure Report is to provide justification and documentation supporting the recommendation that no further corrective action is needed for CAU 374 based on the implementation of corrective actions. The corrective action of closure in place with administrative controls was implemented at CASs 18-23-01 and 20-45-03, and a corrective action of removing potential source material (PSM) was conducted at CAS 20-45-03. The other CASs require no further action; however, best management practices of removing PSM and drums at CAS 18-22-06, and removing drums at CAS 18-22-08 were performed. Corrective action investigation (CAI) activities were performed from May 4 through October 6, 2010, as set forth in the Corrective Action Investigation Plan for Corrective Action Unit 374: Area 20 Schooner Unit Crater, Nevada Test Site, Nevada. The approach for the CAI was divided into two facets: investigating the primary release of radionuclides and investigating other releases (migration in washes and chemical releases). The purpose of the CAI was to fulfill data needs as defined during the data quality objective (DQO) process. The CAU 374 dataset of investigation results was evaluated based on the data quality indicator parameters. This evaluation demonstrated the dataset is acceptable for use in fulfilling the DQO data needs. Analytes detected during the CAI were evaluated against final action levels (FALs) established in this document. Radiological doses exceeding the FAL of 25 millirem per year were found to be present in the surface soil that was sampled. It is assumed that radionuclide levels present in subsurface media within the craters and ejecta fields (default contamination boundaries) at the Danny Boy and Schooner sites exceed the FAL. It is also assumed that PSM in the form of lead-acid batteries at Schooner exceeds the FAL. Therefore, corrective actions were undertaken that consist of removing PSM, where present, and implementing a use restriction and posting warning signs at the Danny Boy and Schooner sites. These use restrictions were recorded in the FFACO database; the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO) Facility Information Management System; and the NNSA/NSO CAU/CAS files. Therefore, NNSA/NSO provides the following recommendations: • No further corrective actions are necessary for CAU 374. • A Notice of Completion to NNSA/NSO is requested from the Nevada Division of Environmental Protection for closure of CAU 374. • Corrective Action Unit 374 should be moved from Appendix III to Appendix IV of the FFACO.