Corrective Action Decision Document/Closure Report for Corrective Action Unit 106: Area 5, 11 Frenchman Flat Atmospheric Sites, Nevada National Security Site, Nevada, Revision 0

Abstract

Corrective Action Unit 106 comprises four corrective action sites (CASs): (1) 05-20-02, Evaporation Pond; (2) 05-23-05, Atmospheric Test Site - Able; (3) 05-45-04, 306 GZ Rad Contaminated Area; (4) 05-45-05, 307 GZ Rad Contaminated Area. The purpose of this CADD/CR is to provide justification and documentation supporting the recommendation that no further corrective action is needed for CAU 106 based on the implementation of corrective actions. The corrective action of clean closure was implemented at CASs 05-45-04 and 05-45-05, while no corrective action was necessary at CASs 05-20-02 and 05-23-05. Corrective action investigation (CAI) activities were performed from October 20, 2010, through June 1, 2011, as set forth in the Corrective Action Investigation Plan for Corrective Action Unit 106: Areas 5, 11 Frenchman Flat Atmospheric Sites. The approach for the CAI was divided into two facets: investigation of the primary release of radionuclides, and investigation of other releases (mechanical displacement and chemical releases). The purpose of the CAI was to fulfill data needs as defined during the data quality objective (DQO) process. The CAU 106 dataset of investigation results was evaluated based on a data quality assessment. This assessment demonstrated the dataset is complete and acceptable for use in fulfilling more » the DQO data needs. Investigation results were evaluated against final action levels (FALs) established in this document. A radiological dose FAL of 25 millirem per year was established based on the Industrial Area exposure scenario (2,250 hours of annual exposure). The only radiological dose exceeding the FAL was at CAS 05-45-05 and was associated with potential source material (PSM). It is also assumed that additional PSM in the form of depleted uranium (DU) and DU-contaminated debris at CASs 05-45-04 and 05-45-05 exceed the FAL. Therefore, corrective actions were undertaken at these CASs that consisted of removing PSM and collecting verification samples. Results of verification samples show that remaining soil does not contain contamination exceeding the FALs. Therefore, the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO) provides the following recommendations: (1) No further corrective actions are necessary for CAU 106. (2) A Notice of Completion to NNSA/NSO is requested from the Nevada Division of Environmental Protection for closure of CAU 106. (3) Corrective Action Unit 106 should be moved from Appendix III to Appendix IV of the FFACO. « less