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3rd Interim Action Construction Report <br />Kimberly-Clark Upland Site <br /> 0121049.080.084 <br />July 30, 2024 2-8 landauinc.com <br />2.6.1.1 Potentially Contaminated Soil <br />Potentially contaminated soil observed during intrusive activities generally consisted of gray to black <br />sands and silts with petroleum odor and sheen and varying amounts of gravel and cobbles, bricks, and <br />dimensional lumber. Free-phase petroleum (light non-aqueous phase liquids or “LNAPL”) was not <br />observed. Given the defined vertical and horizontal limits of excavation necessary for utility installation, <br />the areal extent of any observed contaminated soil was not clear; nor did field observations indicate a <br />new source of contamination. In general, soils with petroleum odor and sheen were observed as shallow <br />as approximately 3 ft bgs and as deep as 10 ft bgs in excavations throughout the Site. In addition to <br />specific locations discussed below, photographs of potentially contaminated soil are included in <br />Appendix D. <br />Some areas with more significant contamination included the following: <br />• During excavation at the light pole LP06 location, heavy sheen was observed in soil and <br />groundwater encountered beneath the recent sand fill. In-place vertical and horizontal concrete <br />structures were encountered at this location. A photograph of the material encountered is <br />included in Appendix D, and the location of LP06 is clearly illustrated on sheet G1.4 (labeled as <br />NT-HML-06; Appendix A). <br />• Gray silt and sand with creosote odor and several creosote-treated piles were observed at and <br />below approximately 6 ft bgs in the excavation for the stormwater lift station vault located just <br />east of reconstructed Outfall M. A photograph of this material and the creosote-treated timbers <br />is included in Appendix D. <br />2.6.1.2 Geotechnically Unsuitable Soil <br />Geotechnically unsuitable soils consisted of sands and silts with above-optimum moisture contents and <br />varying amounts of rock and other debris. General photographs showing geotechnically unsuitable soil <br />are included in Appendix D; additional notable materials observed are described below. <br />• Significant concrete debris and rock was observed on March 3, 2022 between approximately 1 ft <br />bgs to 7 ft bgs in a light pole foundation excavation located just inside the south gate to the Site. <br />Brick and some dimensional wood debris was also observed in this material. The Port discussed <br />observations with Ecology and concluded this material was general debris and not CM. A <br />photograph of the excavated debris is included in Appendix D. <br />2.6.1.3 Concrete and Historical Foundations <br />Significant volumes of in-place concrete structures were observed at the Site. Observed concrete <br />structures included vertical walls, horizontal floors, and vertical metal and concrete pilings. In-place <br />concrete structures were removed using a hydraulic breaker to facilitate excavation necessary for utility <br />installation. Areas where concrete structures were left in place are illustrated on as-built sheet 3.21 <br />(Appendix A), and in these areas, single- or double-layer geogrid was installed for geotechnical stability <br />and long-term integrity of the low-permeability cap. Photographs of example concrete structures <br />encountered during intrusive activities are included in Appendix D. Clean concrete, broken into pieces <br />and free of any soil and rebar, was trucked to offsite recycling facilities.