7100 HARDESON RD Geotech Report 2025-03-06

Geotechnical Engineering Report Merrill Creek Operations Base Expansion • Everett, Washington lierracon December 14, 2020 • Terracon Project No. 81205012 GeoReport. At a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, "Excavations" and its appendices, and in accordance with any applicable local, and/or state regulations. Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for ' construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred. Construction Observation and Testing The earthwork efforts should be monitored under the observation of the Geotechnical Engineer. Monitoring should include documentation of adequate removal of demolition debris, removal of any loose soils encountered within the building expansion and pavement footprints, proof-rolling of the exposed subgrade, and mitigation of subgrade areas delineated by the proof-roll as requiring repair. Each lift of compacted fill should be tested, evaluated, and reworked as necessary until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content. In areas of foundation excavations, the bearing subgrade should be evaluated by the Geotechnical Engineer. In the event that unanticipated conditions are encountered, the Geotechnical Engineer should recommend mitigation options. In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer's evaluation of subsurface conditions, including assessing variations and associated design changes. Wet Weather Earthwork The near-surface soils have a relatively high fines content based on our visual observations and lab testing and should be expected to be moisture sensitive. The near-surface soils will exhibit moderate erosion potential and may be transported by running water. Silt fences and other best- management practices will be necessary to control erosion and sediment transport during construction; however, the most effective measure to address these affects is to prevent the entry of water. The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the fines content (the soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted Responsive ■ Resourceful ■ Reliable 9