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Background: Polynuclear Aromatic Hydrocarbon (PAH) contamination was identified within two (2) areas at the Sunrise Shopping Center facility: within the area of a former heating oil UST behind the 2414B 10th Avenue tenant space (location of monitoring well MW-4) and within the southern extent of the site (location of MW-3). The PAH contamination continues to be monitored during quarterly groundwater monitoring.
Quarterly Monitoring Well Sampling: Two (2) quarterly groundwater sampling events were conducted during the second semi-annual 2022 reporting period. The third quarter sampling was performed on August 2, 2022, with results provided in the Quarterly Groundwater Sampling Report dated September 26, 2022, and the fourth quarter groundwater sampling was performed on October 3, 2022, and the results were provided in the Quarterly Groundwater Sampling Report dated November 7, 2022. Quarterly sampling will continue until a Case Closure Letter is issued for the Site. A Case Closure Report is presently being prepared.
The quarterly sampling results indicate that the PAH constituents of concern include Benzo(a)pyrene, Benzo(b)fluoranthene, and Chrysene. The site-wide presence of fill material (including coal and cinders remaining from the historical use of the property) likely contributes to the observed PAH groundwater concentrations. The most recent (October 2022) sampling data indicate concentrations in MW-3 remain above the Enforcement Standards, and are nearly identical to October 2019 concentrations. The PAH sampling of MW-601 and MW-602 (east and west MW-3) in February 2022 indicated PAH concentrations above the Preventative Action Limits (PALs), but below the Enforcement Standards, indicating that the higher PAH groundwater impacts are limited to the area of contaminated fill material surrounding MW-3. Considering the known PAH soil impacts throughout the southern portion of the Site, low-level PAH concentrations in the groundwater at MW-601 and MW-602 were expected.
The PAH concentrations in MW-4 have remained generally stable and slightly above the Enforcement Standards. The most recent results (October 2022) are comparable to the mostly stable concentrations observed between July 2020 and May 2021. The higher concentrations observed between August 2021 and August 2022 have decreased since the removal of free-product petroleum from MW-4.
No active remediation is currently being conducted, nor is any proposed. The Case Closure Report will be proposing exclusion from the requirement to reduce concentrations based upon an incomplete exposure pathway. Drinking water is provided by the municipality via Lake Michigan and there are no potable groundwater wells on-site.
PFAS Sampling: In addition to conducting quarterly groundwater sampling activities, a final round of groundwater sampling for per- and polyfluoroalkyl substances (PFAS) was performed in August 2022 from all 10 monitoring wells installed on-site. The groundwater sampling procedures and results were discussed in the Emerging Contaminant Evaluation Report Second Addendum dated October 12, 2022. The report indicated PFAS concentrations were highest at the most upgradient monitoring well (MW-603) and decreased to below the applicable standards on-site in the downgradient direction, indicating an upgradient, off-site source of PFAS. WDNR approved the completion of PFAS sampling in an email dated November 7, 2022.
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