Forebay Confirmatory Sediment Sampling Results

Transcription

1 Forebay Confirmatory Sediment Sampling Results Maine Yankee Decommissioning Project Corrective Measures Study May 2004 Prepared for: Maine Yankee 321 Old Ferry Road, Bailey Point Wiscasset, ME Prepared by: Dickenson & Associates 45 Falmouth Road Falmouth, ME And CH2M Hill 25 New Chardon Street, Suite 500 Boston, MA In association with: Jacques Whitford Co., Inc. 75 Pearl Street, Suite 410 Portland, ME And Stratex, LLC 100 Middle Street Portland, ME 04101

2 Introduction The Forebay was part of the liquid waste discharge system that was located on the south end of Bailey Point adjacent to Foxbird Island (Figure 1). The structure consisted of two, 225-foot, north-south oriented dikes that connected Bailey Point to Foxbird Island to the south. The dikes formed a containment structure that received large volumes (up to 420,000 gallons per minute) of circulating and service water and liquid effluents. The water from the Forebay flowed to buried piping on Foxbird Island that carried the water to a submerged diffuser system in Montsweag Bay, south of Foxbird Island. In support of site decommissioning activities, the Forebay remediation was completed in December The remediation activities included: Removal of the upper ten feet of both dikes and Removal of approximately 977 cubic yards of sediment. Additional activities at the Forebay will include backfill and grading. Upon completion of the grading and filling activities, the west dike of the Forebay will be breeched to form an upland marsh/wetland. The Forebay sediment removal was driven by radiological constituents present in the sediment, and was not a function of RCRA-related chemical contamination. Following the removal of the Forebay sediment, three sediment samples (MY05SD201, MY05SD203, and MY05SD204) were taken from the remaining sediments on September 22, 2003 to confirm that the remaining material was consistent with RCRA closure. Two samples were located north of the weir in the area of the former seal pit (MY05SD201 and MY05SD203), and the third sample was located in the sparse sediments remaining south of the weir (MY05SD204) (Figure 1). A duplicate sample (MY05SD202) for MY05SD201 was collected to support quality control/quality assurance activities. The three samples and duplicate were analyzed for diesel range organics (DRO), target analyte list (TAL) metals, polychlorinated biphenyls (PCBs), pesticides, and semivolatile organic compounds (SVOCs). The samples were collected, analyzed and validated consistent with the Maine Yankee Quality Assurance Project Plan (QAPP) (Reference 1). Forebay Confirmatory Sediment Laboratory Results The laboratory results for the three confirmatory samples and the duplicate are included in Table 1. Low levels of DRO were detected in each of the sediment samples ranging from 8.21J mg/kg to 19 mg/kg. These low DRO detections are well below the Maine Department of Environmental Protection (MDEP) cleanup value of 100 mg/kg established for Baseline 2 sites (Reference 2). TAL metals were detected in the sediment samples and except for boron, calcium, copper, iron, lead, sodium, and zinc; the metal concentrations are consistent with background soil levels established in the Backlands portion of the Maine Yankee site (Reference 3). These metals that exceed the background concentrations are most likely related to the large amounts of seawater that were discharged to the Forebay during the operational history of the Forebay Confirmatory Sediment Sampling Results May 2004 Bailey Point CMS Report Appendix B B- 1

3 site. Although these metals exceed the background distribution established for the Maine Yankee site, all metals except arsenic have concentrations less than MDEP Remedial Action Guidelines (RAGs) established for residential soils (Table 1 and Reference 4). The arsenic concentrations in three sediment samples ranged from 7.2 mg/kg to 11.1 mg/kg, relative to the MDEP RAG vales of 10 mg/kg. While the arsenic concentration in MY05SD203 (11.1 mg/kg) slightly exceeds the RAG value, the range of observed arsenic levels in the sediments is within the background range established for arsenic (0.16mg/kg to 16.4 mg/kg) (Reference 3). The arsenic concentrations are believed to represent background levels. PCBs were detected in two of the three sediment samples at low concentrations ranging from 28.1 µg/kg to 55.0 µg/kg (Table 1). The detected PCB (Aroclor 1254) concentrations are orders of magnitude below the MDEP RAG value (2,000 µg/kg) for PCBs and are lower than Aroclor 1254 concentrations observed in shallow soils present in the Industrial portion of the site. Quantitative risk characterization for the PCB concentrations in the shallow Industrial area soils were shown to have no risk associated with them (Reference 3). The combination of the low concentrations relative to the MDEP RAG values and risk calculations performed of the industrial area soils demonstrates that PCBs in the remaining sediments do not present a risk to human health. Low concentrations of the pesticides beta-bhc (31.8J µg/kg ) and gamma-chlordane (19.0J µg/kg) were detected in MY05SD203 and MY05SD201, respectively. The low part per billion concentrations of the two pesticides are not believed to present a risk to human health. Low concentrations of several SVOCs were also detected in the sediment samples. Bis (2- ethylhexyl)phthalate (92J µg/kg to 170 µg/kg) and 11 polynuclear aromatic hydrocarbons (PAHs) were detected in the sediment samples (Table 1). The low concentrations of bis (2- ethylhexyl)phthalate were reported in duplicate sample for MY05SD201 and in MY05SD203. The range of observed bis (2-ethylhexyl)phthalate is orders of magnitude lower than the MDEP RAG value (1,220,000 µg/kg) and does not present a risk to human health. The detected PAHs include four non-carcinogenic compounds (phenanthrene, chrysene, flouranthene, and pyrene) and seven carcinogenic PAHs (benzo(a)anthracene, benzo(b)flouranthene, benzo(k)flouranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene, and benzo(g,h,i)perylene. RAG values are not established for the noncarcinogenic PAHs, but the RAG concentration for the sum of carcinogenic PAHs is set at 2,000 µg/kg (Reference 4). The sum of the carcinogenic PAHs for the three samples and the duplicate are below the RAG value established for residential soils (Reference 4, Table 1), and are not believed to present a risk to human health. As part of the Maine Yankee site closure activities, the Forebay will be filled with approximately 10 feet of clean fill and a upland marsh/wetland will be established in spring Any potential risk for this area will be further minimized in the future, as the remaining material in the Forebay will be beneath 10 feet of soil and not readily available for exposure. Forebay Confirmatory Sediment Sampling Results May 2004 Bailey Point CMS Report Appendix B B- 2

4 Conclusions Three sediment samples and a duplicate sample were taken from the remaining sediments following sediment removal activities in the Forebay. The TAL metal concentrations were either consistent with background soil concentrations or below MDEP RAG values established for residential soils. The low DRO detections were also below petroleum concentrations developed for Baseline 2 sites. The low detected concentrations of PCBs, pesticides, and SVOCs are below MDEP RAG values developed for residential soils or are low enough to be consistent with no significant risk. Potential risk in the Forebay is further minimized due to the plans for filling the Forebay with approximately 10 feet of clean fill and establishing an upla1nd marsh/wetland. The remaining material in the Forebay will remain 10 feet below the ground surface significantly reducing the risk potential in the Forebay area. References 1. Maine Yankee Quality Assurance Project Plan Revision 1 (June 2001) 2. Procedural Guidelines for Establishing Action Levels and Remediation Goals for the Remediation of Oil Contaminated Soil and Groundwater in Maine (March 2000) 3. Bailey Point RCRA RFI Report (March, 2004) 4. Maine Department of Environmental Protection Remedial Action Guidelines (May 1997) Figures 1. Forebay Confirmatory Sediment Sample Locations Tables 1. Laboratory Analytical Results Forebay Confirmatory Samples Forebay Confirmatory Sediment Sampling Results May 2004 Bailey Point CMS Report Appendix B B- 3

5 Figures Results of Forebay Confirmatory Sediment Samples May 2004

6 Tables Results of Forebay Confirmatory Sediment Samples May 2004

7 Appendices Results of Forebay Confirmatory Sediment Samples May 2004

8 Appendix A Data Validation Report Forebay Confirmatory Samples Results of Forebay Confirmatory Sediment Samples May 2004