This Corrective Action Decision Document (CADD)/Closure Report (CR) has been prepared for Corrective Action Unit 556, Dry Wells and Surface Release Points, located at the Nevada Test Site, Nevada, in accordance with the Federal Facility Agreement and Consent Order (FFACO, 1996; as amended February 2008). Corrective Action Unit (CAU) 556 is comprised of four corrective action sites (CASs): 06-20-04, National Cementers Dry Well 06-99-09, Birdwell Test Hole 25-60-03, E-MAD Stormwater Discharge and Piping 25-64-01, Vehicle Washdown and Drainage Pit The purpose of this CADD/CR is to provide justification and documentation supporting the recommendation for closure of CAU 556 with no further corrective action. To achieve this, corrective action investigation (CAI) activities began on February 7 and were completed on June 19, 2008, as set forth in the Corrective Action Investigation Plan for Corrective Action Unit 556: Dry Wells and Surface Release Points, Nevada Test Site, Nevada (NNSA/NSO, 2007). The purpose of the CAI was to fulfill the following data needs as defined during the data quality objective (DQO) process: Determine whether contaminants of concern (COCs) are present. If COCs are present, determine their nature and extent. Provide sufficient information and data to complete appropriate corrective actions. The CAU 556 data were evaluated based on the data quality assessment process, which demonstrated the quality and acceptability of the data for use in fulfilling the DQO data needs. Analytes detected during the CAI were evaluated against appropriate final action levels (FALs) to identify the COCs for each CAS. The results of the CAI identified COCs at one of the four CASs in CAU 556 that required the completion of a corrective action. Assessment of the data generated from investigation activities conducted at CAU 556 revealed the following: Corrective Action Sites 06-20-04, 06-99-09, and 25-64-01 do not contain contamination at concentrations exceeding the FALs.
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