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ASPECT CONSULTING <br />PROJECT NO. AS190583A-08  MAY 21, 2025 FINAL 47 <br /> <br />During the February and August 2014 porewater sampling events, a sample of surface <br />water (EWW-1) from the East Waterway was also collected to represent local reference <br />water quality. This sample was collected from a depth of approximately 3 feet below the <br />water surface at the barge unloading dock immediately offshore of the Upland Area. <br />The porewater samples were submitted to ALS Environmental laboratory for analysis of <br />total ammonia, dissolved sulfide, and dissolved metals (arsenic, copper, mercury, and <br />nickel) using analytical methods specified in the QAPP (Aspect, 2013c), and, in the first <br />sampling event, for salinity using Standard Method SM 2520B and total metals. Dissolved <br />lead and zinc analyses were also conducted for the second (August 2014) sampling event. <br />4.2.3 Supplemental Intertidal Porewater Sampling for Free Sulfide <br />(February 2015) <br />Following discussion with Ecology regarding the dissolved sulfide concentrations detected <br />during the February and August 2014 porewater monitoring events, a modified sampling <br />and analysis approach to specifically quantify free sulfide, the bioavailable and toxic form <br />of sulfide, was proposed in a Work Plan (Aspect and Anchor QEA, 2015a) reviewed and <br />approved by Ecology. The supplemental porewater sampling was performed in February <br />2015 using the passive, in-situ diffusive gradient in thin film (DGT) gel technology, to <br />obtain tidally averaged concentrations of free sulfide. Sampling probes were advanced <br />during lower low tide conditions at the four intertidal porewater sampling locations (PW- <br />3, PW-4, PW-5, and PW-7) that had detected dissolved sulfide concentrations during the <br />February and/or August 2014 sampling events, and were allowed to equilibrate in situ for <br />approximately 49 hours. Anchor QEA (2015) presents the method for calculation of free <br />sulfide concentrations in porewater from the laboratory-measured masses of free sulfide in <br />each sample, along with a discussion of the results and water quality benchmarks for free <br />sulfide. <br />4.2.4 Supplemental Data Collection Supporting FS (September <br />2015) <br />Following Ecology review of the RI Data Report (Aspect, 2014f), additional data <br />collection was conducted to further refine contaminant nature and extent in support of the <br />Upland Area FS, in accordance with an Addendum to the RI/FS Work Plan which can be <br />viewed on Ecology’s website (Aspect, 2015b). The supplemental data collection included <br />drilling and soil sampling from 16 new soil borings; soil sampling, installation, and <br />development of two new monitoring wells; and sampling of groundwater from the two <br />new wells and three existing ones. The supplemental data collection was completed in <br />September 2015. In addition, Site-wide water level measurements, and groundwater pH <br />measurements in selected wells, were collected in February 2016 in conjunction with the <br />IA confirmational groundwater monitoring event. <br />4.2.5 Supplemental Intertidal Seep Sampling (October 2016) <br />During an August 16, 2016, meeting to discuss preliminary Ecology comments on the <br />draft RI/FS, Ecology expressed concerns that pipes and holes/discontinuities in the Upland <br />Area shoreline bulkhead may represent uncharacterized preferred pathways for upland <br />groundwater to reach the East Waterway. In response, on August 31, 2016, representatives