Corrective Action Decision Document/Closure Report for Corrective Action Unit 561: Waste Disposal Areas, Nevada National Security Site, Nevada, Revision 0

Abstract

CAU 561 comprises 10 CASs: (1) 01-19-01, Waste Dump; (2) 02-08-02, Waste Dump and Burn Area; (3) 03-19-02, Debris Pile; (4) 05-62-01, Radioactive Gravel Pile; (5) 12-23-09, Radioactive Waste Dump; (6) 22-19-06, Buried Waste Disposal Site; (7) 23-21-04, Waste Disposal Trenches ; (8) 25-08-02, Waste Dump; (9) 25-23-21, Radioactive Waste Dump; and (10) 25-25-19, Hydrocarbon Stains and Trench. The purpose of this CADD/CR is to provide justification and documentation supporting the recommendation for closure of CAU 561 with no further corrective action. The purpose of the CAI was to fulfill the following data needs as defined during the DQO process: (1) Determine whether COCs are present; (2) If COCs are present, determine their nature and extent; and (3) Provide sufficient information and data to complete appropriate corrective actions. The following contaminants were determined to be present at concentrations exceeding their corresponding FALs: (1) No contamination exceeding FALs was identified at CASs 01-19-01, 03-19-02, 05-62-01, 12-23-09, and 22-19-06. (2) The surface and subsurface soil within the burn area at CAS 02-08-02 contains arsenic and lead above the FALs of 23 milligrams per kilogram (mg/kg) and 800 mg/kg, respectively. The surface and subsurface soil within the burn area also contains melted lead slag (potential source material [PSM]). The soil within the waste piles contains polyaromatic hydrocarbons (PAHs) above the FALs. The contamination within the burn area is spread throughout the area, as it was not feasible to remove all the PSM (melted lead), while at the waste piles, the contamination is confined to the piles. (3) The surface and subsurface soils within Trenches 3 and 5 at CAS 23-21-04 contain arsenic and polychlorinated biphenyls (PCBs) above the FALs of 23 mg/kg and 0.74 mg/kg, respectively. The soil was removed from both trenches, and the soil that remains at this CAS does not contain contamination exceeding the FALs. Lead bricks and counterweights were also removed, and the soil below these items does not contain contamination that exceeds the FAL for lead. (4) The concrete-like material at CAS 25-08-02 contains arsenic above the FAL of 23 mg/kg. This concrete-like material was removed, and the soil that remains at this CAS does not contain contamination exceeding the FALs. Lead-acid batteries were also removed, and the soil below the batteries does not contain contamination that exceeds the FAL for lead. (5) The surface soils within the main waste dump at the posted southern radioactive material area (RMA) at CAS 25-23-21 contain cesium (Cs)-137 and PCBs above the FALs of 72.9 picocuries per gram (pCi/g) and 0.74 mg/kg, respectively. The soil was removed from the RMA, and the soil that remains at this CAS does not contain contamination exceeding the FALs. (6) The surface and subsurface soils at CAS 25-25-19 do not contain contamination exceeding the FALs. In addition, lead bricks were removed, and the soil below these items does not contain contamination that exceeds the FAL for lead. The following best management practices were implemented: (1) Housekeeping debris at CASs 02-08-02, 23-21-04, 25-08-02, 25-23-21, and 25-25-19 was removed and disposed of; (2) The open trenches at CAS 23-21-04 were backfilled; (3) The waste piles at CAS 25-08-02 were removed and the area leveled to ground surface; and (4) The remaining waste piles at the main waste dump at CAS 25-23-21 were leveled to ground surface. Therefore, NNSA/NSO provides the following recommendations: (1) No further action for CASs 01-19-01, 03-19-02, 05-62-01, 12-23-09, and 22-19-06; (2) Closure in place with an FFACO use restriction (UR) at CAS 02-08-02 for the remaining PAH-, arsenic-, and lead-contaminated soil, and the melted lead PSM. The UR form and map have been filed in the NNSA/NSO Facility Information Management System, the FFACO database, and the NNSA/NSO CAU/CAS files; (3) No further corrective action at CAS 23-21-04, as the lead bricks and counterweights (PSM) have been removed, and the COCs of arsenic and PCBs in soil have been removed; (4) No further corrective action at CAS 25-08-02, as the COC of arsenic in soil has been removed, and the lead-acid batteries have been removed; (5) No further corrective action at CAS 25-23-21, as the COCs of Cs-137 and PCBs in soil have been removed, and the cast-iron pipes have been removed and disposed of; (6) No further corrective action at CAS 25-25-19, as the lead bricks (PSM) been removed; (7) A Notice of Completion to the NNSA/NSO is requested from the Nevada Division of Environmental Protection for closure of CAU 561; and (8) Corrective Action Unit 561 should be moved from Appendix III to Appendix IV of the FFACO.