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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 first semi-annual 2022 reporting period. The fourth quarter sampling was performed on January 24, 2022, with results provided in the Quarterly Groundwater Sampling Report dated March 1, 2022, and the second quarter groundwater sampling was performed on April 11, 2022, and the results were provided in the Quarterly Groundwater Sampling Report dated May 31, 2022. Quarterly sampling will continue until a Case Close Out Letter is issued for the Site.
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 (April 2022) sampling data indicate concentrations in MW-3 remain above the Enforcement Standards, generally consistent with the concentrations observed in October 2019. 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 vary generally between concentrations slightly above the PAL to slightly above the Enforcement Standards. During the first quarter 2022 sampling event, a layer of floating free-product petroleum was identified in MW-4 (not previously observed, but a likely contributor to the fluctuating concentrations). Manual recovery efforts were promptly initiated to remove this source material. The manual recovery efforts appear to have already resulted in a decrease in groundwater impact, with PAH concentrations decreasing dramatically from January 2022 and with no PAL exceedances in April 2022, which is the first time since July 2019.
No active remediation is currently being conducted, nor is any proposed. There is no exposure to this residual contamination because drinking water is provided by the municipality via Lake Michigan and the groundwater ingestion route of exposure is incomplete. There are no potable groundwater wells on-site.
PFAS Sampling: In addition to conducting quarterly groundwater sampling activities, four (4) new monitoring wells (MW-600 to MW-603) were installed in January 2022 and groundwater sampling for per- and polyfluoroalkyl substances (PFAS) was performed in February 2022. (PFAS sampling of previously existing monitoring wells had been previously completed in 2021.) The well installation and groundwater sampling procedures and results were discussed in the Emerging Contaminant Evaluation Report Addendum dated March 28, 2022. The report showed that only the most upgradient monitoring well (MW-603) was reported with any PFAS constituents above the applicable standards, indicative of an upgradient, off-site source of the PFAS contamination observed on-site. In a response email of April 7, 2022, WDNR requested another complete round of PFAS sampling to further evaluate concentrations and trends.
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