Summary of Polycyclic Aromatic Hydrocarbon Concentrations in Sediment Samples Figures 7-1.1, 7-2.1, and 7-3.1 show the maximum concentrations of total LMW and HMW PAHs (Priority+2 List and Long List; see Section 5) measured at each sediment location for the drainage ways, Dawson Cove, and Lake Conway, respectively. PAHs were detected in all site background sediment samples, and in all sediment sample locations in the drainage ways, Dawson Cove, and Lake Conway. PAH concentrations in sediment samples collected from the drainage ways, Dawson Cove, and Lake Conway are discussed in Sections 7.3.1, 7.3.2, and 7.3.3. Summary of Polycyclic Aromatic Hydrocarbon Concentrations in Drainage Ways The statistics for the individual and total PAHs are presented for the drainage ways in Table 7-5. None of the individual PAHs were above their respective ESVs. The FOD for the total LMW and HMW PAHs compared to their respective ESVs is summarized in the table below. Analyte Drainage Way Site Background N > ESV N > Site Bkg N > ESV Priority+2 List Total HMW PAHs 1 0 3 Total LMW PAHs 0 0 2 Long List Total HMW PAHs 2 0 3 Total LMW PAHs 3 2 2 Toxic Unit One-Carbon Model TU* 0 0 0 Notes: N > ESV = Number of samples (excludes duplicates) above the respective sediment ESVs Site background refers to background sediment locations in the drainage ways. * Summary for surface sediment samples only. The TU calculations for drainage way sediment samples are provided in Appendix J. In 33 of 35 samples in the drainage ways, the total HMW and LMW PAHs (both Priority+2 and Long Lists) are below the sediment ESVs. The TUs for the surface sediment samples were all 1.0 or less. In two samples (and one duplicate) in the drainage ways, PAH summations were detected above the ESVs; these samples are discussed below:
Sheen Area Location ID PAHs Crude Oil* TPH Crude Oil* Type Sheen Structure Color Dawson Cove Inlet Channel INLT-001 Possible Possible Brittle Streamer Metallic INLT-002 Yes Yes Non-Brittle Streamer with oil spots Metallic Dawson Cove Open Water COVE-003 Yes Yes Non-Brittle Streamer with oil spots Metallic/ Rainbow Notes: *Crude oil from the Pegasus Pipeline Dawson Cove B-On Water B-On Water sheens were consistent in observed locations, but the number of sheens observed declined with time. Two sheen samples collected within the B-On Water monitoring area did not resemble crude oil from the Pegasus Pipeline and may be associated with urban runoff and/or biogenic activity (see table below). About 50 percent of the observed sheens were non-brittle, and oil spots (0.1 to 1 inch in diameter) were observed with 15 sheen locations in the channel between the heavy vegetation in this monitoring area, indicating that some sheens may contain crude oil. Sheens observed in the downstream B-On Water area did not appear to contain crude oil. Sheen Area Location ID PAHs Crude Oil* TPH Crude Oil* Sheen Type Sheen Structure Color B-On Water COVE-001 No No Non-Brittle Streamer Metallic COVE-002 No No Brittle Patch Metallic Notes: *Crude oil from the Pegasus Pipeline Throughout the sheen monitoring period, only one brittle sheen location was observed at the Dawson Cove Outlet on November 5, 2013. Brittle sheens are often of natural biogenic origin indicating that the sheens may be associated with microbial activity. 11.3 Summary of Findings Based on the sheen monitoring activities and screening data evaluation, the limited areas with crude-oil-related sheens appear to be primarily located in the Dawson Cove Inlet Channel and the Open Water Area. Ongoing monitoring for sheens in the Dawson Cove is recommended, although at a reduced frequency. Additional investigation