Corrective Action Decision Document/Closure Report for Corrective Action Unit 219: Septic Systems and Injection Wells, Nevada Test Site, Nevada, Rev. No.: 0

This Corrective Action Decision Document/Closure Report has been prepared for Corrective Action Unit (CAU) 219, Septic Systems and Injection Wells, in Areas 3, 16, and 23 of the Nevada Test Site, Nevada, in accordance with the ''Federal Facility Agreement and Consent Order'' (1996). Corrective Action Unit 219 is comprised of the following corrective action sites (CASs): (1) 03-11-01, Steam Pipes and Asbestos Tiles; (2) 16-04-01, Septic Tanks (3); (3) 16-04-02, Distribution Box; (4) 16-04-03, Sewer Pipes; (5) 23-20-01, DNA Motor Pool Sewage and Waste System; and (6) 23-20-02, Injection Well. The purpose of this Corrective Action Decision Document/Closure Report is to provide justification and documentation supporting the recommendation for closure of CAU 219 with no further corrective action beyond the application of a use restriction at CASs 16-04-01, 16-04-02, and 16-04-03. To achieve this, corrective action investigation (CAI) activities were performed from June 20 through October 12, 2005, as set forth in the CAU 219 Corrective Action Investigation Plan and Record of Technical Change No. 1. A best management practice was implemented at CASs 16-04-01, 16-04-02, and 16-04-03, and corrective action was performed at CAS 23-20-01 between January and April 2006. In addition, a use restriction will be applied to CASs 16-04-01, 16-04-02, and 16-04-03 to provide additional protection to Nevada Test Site personnel. The purpose of the CAI was to fulfill the following data needs as defined during the data quality objective (DQO) process: (1) Determine whether contaminants of concern (COCs) are present. (2) If COCs are present, determine their nature and extent. (3) Provide sufficient information and data to complete appropriate corrective actions. The CAU 219 dataset from the investigation results was evaluated based on the data quality indicator parameters. This evaluation demonstrated the quality and acceptability of the dataset for use in fulfilling the DQO data needs. Analytes detected during the CAI were evaluated against final action levels (FALs) established in this document. A Tier 2 evaluation was conducted, and a FAL of 185,000 micrograms per kilogram was calculated for chlordane at CASs 16-04-01, 16-04-02, and 16-04-03 based on an occasional use area exposure scenario. This evaluation of chlordane based on the Tier 2 FAL determined that no FALs were exceeded. Therefore, the DQO data needs were met, and it was determined that no corrective action (based on risk to human receptors) is necessary for the site. The following contaminants were determined to be present at concentrations exceeding their corresponding FALs: (1) The surface soil surrounding the main concrete pad at CAS 23-20-01 contained Aroclor-1254, Aroclor-1260, and chlordane above the FALs. This soil, along with the COCs, was subsequently removed at CAS 23-20-01. (2) The sludge in the concrete box of the catch basin at the large concrete pad at CAS 23-20-01 contained lead and benzo(a)pyrene above the FALs. This contamination was limited to the sludge in the concrete box of the catch basin and did not migrate to the subsurface features beneath it. The contaminated and the concrete box of the catch basin were subsequently recovered at CAS 23-20-01