Red Wing: Eastern End Main Production Area Sample Clauses

Red Wing: Eastern End Main Production Area. Soils in the vicinity of the eastern end of the main production area were excavated on October 29, 2008, consisting of an area approximately 20’ by 32’ to a depth of 5.0’ to address elevated barium and chromium concentrations at B1607 as identified in ENVIRON’s October 2006 remedial investigation. As shown on Figure 6, one base sample (PE04) and three sidewall samples (PE01 through PE03) were collected for PPMs+Ba analysis. As proposed in the IRM Work Plan, samples were collected from two intervals at each sidewall (2.0-2.5’ and 3.5-4.0’), targeting the impacted intervals at B1607. Reported concentrations of PPMs+Ba are summarized in Appendix B and are shown on Figure 6. Metals above the commercial-use SCO of 400 mg/kg were present at only one sidewall sample, PE03 at the 2.0’ – 2.5’ interval, where barium (441 mg/kg). Accordingly, an additional 12’ by 15’ area was removed from the northwest portion of the excavation to a depth of 5.0’ on October 31, 2008, as shown on Figure 6. One sidewall sample (PE03A) was collected for PPMs+Ba analysis. In addition, due to the presence of dark gray/black soils noted at the base of this portion of the excavation, an additional base sample (PE05) was collected from this area from 5.0-5.5’ and submitted for PPMs+Ba analysis. Analytical results for these additional samples confirmed that all metals concentrations were well below the corresponding commercial-use SCOs (see Figure 6). As such, no further remedial action is warranted in this area. In addition, these data indicated that the gray/black coloration of the soils in this area likely representing native soil conditions. As discussed below in Section 5.2.6.7, additional sampling of this soil type was subsequently conducted and again confirmed the absence of any metals above commercial-use SCOs.