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January 3, 2025 <br />HWA Project No. 2021-159-21 <br />Geotechnical Engineering Report 49 HWA GEOSCIENCES INC. <br />Port Gardner Storage Facility <br />4.13.3 Wet Weather Earthwork <br />General recommendations relative to earthwork performed in wet weather or in wet conditions <br />are presented below. These recommendations should be incorporated into the contract <br />specifications. <br />• Earthwork should be undertaken in small sections to minimize exposure to wet weather. <br />Excavation or the removal of unsuitable soil should be followed promptly by the <br />placement and compaction of a suitable thickness of clean crushed rock or sand and <br />gravel. The size and type of construction equipment used may have to be limited to <br />minimize soil disturbance. <br />• Material used as structural fill should consist of clean granular soil, of which not more <br />than 5% by dry weight passes the U.S. Standard No. 200 sieve, based on wet sieving the <br />fraction passing the ¾-inch sieve. The fine-grained portion of the structural fill soils <br />should be non-plastic. <br />• The ground surface within the construction area should be sloped and sealed with a <br />smooth-drum vibratory roller, to promote rapid runoff of precipitation and to prevent <br />ponding of water. <br />• Excavation and placement of fill material should be observed under the full-time <br />observation of a representative of the geotechnical engineer or the engineer that accepts <br />and sign the compaction reports, to determine that the work is being accomplished in <br />accordance with the project specifications and the recommendations contained herein. <br />• Bales of straw and/or geotextile silt fences should be strategically located to control <br />erosion and the movement of soil. <br />4.14ENVIRONMENTAL CONSIDERATIONS <br />The site is the northernmost unit within the larger Kimberly-Clark cleanup site (Ecology Cleanup <br />Site ID 2569). It is known as “Unit E” in documents describing the entire cleanup site. A 2012 <br />remedial investigation of Unit E detected PAHs, metals, and TPH exceeding applicable CULs in <br />soils retrieved from eight exploratory borings distributed around the site. These contaminants <br />were not detected in groundwater at the site at concentrations exceeding CULs, with the <br />exception of copper and sulfides. A 2019 investigation focused on soils within a swale along the <br />southern property line detected concentrations of TPH and cPAHs below CULs. Arsenic, copper, <br />nickel, and zinc were detected in the 2019 soil samples at concentrations exceeding CULs. <br />A memo summarizing the above and outlining a planned cleanup action plan (CAP) for the site <br />(Floyd | Snider, 2021) describes plans to record a restrictive covenant for the property to insure