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ASPECT CONSULTING <br />PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 45 <br /> <br />Monitoring was conducted on a quarterly basis for one year (May, August, and November <br />2014, and February 2015). <br />The data from the first four quarterly rounds of groundwater monitoring are presented in <br />the Interim Action Confirmational Groundwater Monitoring Report (Aspect, 2015d), <br />which recommended ongoing monitoring in some, but not all, of the wells. Both the Work <br />Plan and the Report can be viewed on Ecology’s website using the weblink provided in <br />Section 1. <br />The eight rounds of IA confirmational groundwater monitoring data (May 2014 through <br />August 2016) are incorporated into this RI/FS. Additional groundwater monitoring <br />requirements for the IA areas will be incorporated into the future long-term groundwater <br />monitoring plan for the Site. Additional results from subsequent groundwater monitoring <br />would be summarized and presented to Ecology in annual report(s) in accordance with the <br />future long-term groundwater monitoring plan for the Site. <br />4.2 Additions to RI/FS Work Plan <br />While the RI data collection program was underway, additional data collection was <br />completed in accordance with several Ecology-approved addenda to the RI/FS Work Plan <br />(Aspect, 2014b, 2014c, 2015b, 2016a, 2017a, 2017c; Aspect and Anchor QEA, 2015a). <br />These addenda can be viewed on Ecology’s website using the weblink provided in Section <br />1. Those additional data collection activities are described in the following subsections. <br />4.2.1 Vapor Intrusion Assessment for Distribution Warehouse <br />(March and November 2014) <br />Petroleum-contaminated soil is present beneath the distribution warehouse located in the <br />southeast corner of the Upland Area. Sampling was conducted in March and November <br />2014 to evaluate the potential for intrusion of petroleum hydrocarbon vapors (vapor <br />intrusion [VI]) from subgrade soil into the warehouse. In both sampling events, three pairs <br />of collocated sub-slab air samples 16 and indoor air samples were collected and analyzed in <br />accordance with the Ecology-approved sampling plan (Aspect, 2014b). The sampling <br />locations were chosen based on prior sub-slab soil sampling results indicating areas of <br />lighter-range petroleum hydrocarbon releases. In the initial (March 2014) sampling event, <br />indoor air samples were collected prior to sub-slab vapor point installation to avoid <br />potential introduction of sub-slab vapors into the building, which could bias the indoor air <br />sample results. Those sub-slab vapor point installations were then used in the follow-up <br />(November 2014) sampling event as well. Outdoor air samples were also collected at <br />locations upwind of the warehouse at the time of each sampling event to document the <br />ambient background air quality. <br />Samples were submitted to ALS Environmental for laboratory analysis using a combined <br />Massachusetts Department of Environmental Protection (MassDEP) Air-Phase Petroleum <br />Hydrocarbons (APH) method for petroleum fractions, and EPA Method TO-15 for VOCs <br />as described in the MassDEP APH method standard. Sub-slab vapor samples were also <br /> <br />16 Samples collected from the void space beneath the distribution warehouse floor slab.