Blue Wing. Soil excavation activities beneath the former Blue Wing slab took place from January 15 to February 19, 2009, where as proposed in the IRM a total area of approximately 30’ by 110’ was removed to a depth of 8’ to address metals and SVOC exceedances found in soils from borings SB-10 – SB-13 and SB-14A during the Supplemental RI sampling event in June 2008, as shown on Plate 6. A total of fifteen post-excavation samples were originally collected, including nine sidewall soil samples at three intervals each, 0.5’ – 1.0’, 2.0’ – 2.5’, and 4.0’ – 4.5’, and six basal samples from 8.0’ – 8.5’ in the center of the excavation. Note that no sidewall samples could be collected from the eastern, western and southwestern portions of the excavated area, as the excavation abutted the outer edges of the former Blue Wing footers (extending to a depth of 5 feet) in these areas. Analytical results for samples associated with the Blue Wing excavation are presented in Appendix B and summarized on Plate 6. Reported metals and SVOC concentrations for all samples were below the commercial-use SCO, with the exception of metals at two sidewall samples at multiple intervals: BW04 with exceedances for barium (456 and 772 mg/kg) and nickel (392 mg/kg) and BW07, with two exceedances for nickel (315 and 448 mg/kg). One base sample, BW06 (349 mg/kg), also exceeded the commercial-use SCO for nickel of 310 mg/kg. As such, an additional 1 foot of soil (to a total depth of 9’) was removed in the base of the excavation at this location, and a second base sample (BW06-SS02) was collected and analyzed for PPMs+Ba. After further excavation at the BW04 sample location, three additional sidewall samples were collected, BW04A, BW04B, and BW04C. However, after reported exceedances of nickel were found in six of the nine intervals sampled at these sampling locations, Sun Chemical concluded the excavation would be extended north to the outer-edge footer of the former Blue Wing Building. As such, an additional approximately 22’ by 40’ area (as shown on Plate 6) was excavated to a depth of 9’ and staged for disposal. Analytical results for samples associated with additional delineation activities in the Blue Wing excavation are also summarized on Plate 6. The nickel concentration for the second base sample, BW06-SS02, was 238 mg/kg, well below the commercial-use SCO. As such, these additional remedial actions fully addressed metals contamination beneath the former Blue Wing such that no further action i...
