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ANG is awarding a contract to complete supplemental RI for this site. Contract will be awarded NLT 30 Sep 2023.
Background:
Data from groundwater samples collected from three temporary wells in 2014 and 18 temporary
wells in 2016 and analyzed for VOCs and PAHs were reviewed to identify locations for installation of four permanent wells and sampling and analysis for VOCs and PAHs in October and November 2016. The wells (CG018a-MW201 through -MW204) are screened to depths between 11 and 15 ft bgs and monitor shallow groundwater at the perimeter of the soil boring locations and the site boundary (Exhibit 1-4). Although VOCs were detected at isolated locations at concentrations
exceeding ESs, multiple lines of evidence review, including fingerprinting analysis, indicated the impacts observed in groundwater were likely related to the 1968 Westshore pipeline release rather than a new release. Wells CG018a-MW201 through -204 were installed at
what were thought to be boundary well locations. In addition to re-sampling these wells to confirm previous findings for the SRI, three monitoring wells will be installed within potential source areas (grassy locations where spilled material would drain) to evaluate soil and groundwater for VOCs and PAHs. Wells will be installed to between 10 and 15 ft bgs at the approximate locations shown on Exhibit 1-4. Data will be used to demonstrate presence/absence of contaminants in the source area at concentrations exceeding ESs. The existing boundary wells will provide data relative to
the detections of select VOCs at concentrations exceeding the ES as well as contaminant migration, if present, from the source area. Sampling over two seasonal events will establish contaminant trends.
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