2320 CALIFORNIA ST Geotech Report 2025-07-25

Administration Building Office Expansion Everett,Washington The actual thickness will be dependent on the structural fill material used and the type and size of compaction equipment. Each lift should be conditioned to the proper moisture content and compacted to the specified density before placing subsequent lifts. Structural fill should be compacted to the following criteria: All fill placed under the proposed building addition footprint should be placed as structural fill compacted to at least 95 percent MDD. Structural fill placed against foundations should be compacted to at least 95 percent of the MDD. Structural fill in new pavement and hardscape areas, including utility trench backfill, should be compacted to at least 90 percent of the MDD estimated in accordance with ASTM D 1557, except that the upper 2 feet of fill below final subgrade should be compacted to at least 95 percent of the MDD,see Figure 4. S Structural fill placed as crushed surfacing base course below pavements should be compacted to 95 percent of the MDD. Non-structural fill, such as fill placed in landscape areas,should be compacted to at least 90 percent of the MDD. Weather Considerations. Disturbance of near surface soils should be expected, especially if earthwork is completed during periods of wet weather. During dry weather the soils will (1) be less susceptible to disturbance, (2) provide better support for construction equipment, and (3) be more likely to meet the required compaction criteria. The wet weather season generally begins in October and continues through May in western Washington; ' however, periods of wet weather may occur during any month of the year. For earthwork activities during wet weather,we recommend that the following steps be taken: The ground surface in and around the work area should be sloped so that surface water is directed away from the work area. The ground surface should be graded so that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and I , trenches. Measures should be implemented to remove surface water from the work area. Earthwork activities should not take place during periods of moderate to heavy precipitation. Slopes with exposed soils should be covered with plastic sheeting. The contractor should take necessary measures to prevent on-site soils and soils to be used as fill from becoming wet or unstable. These measures may include the use of plastic sheeting,sumps with pumps, and grading. The site soils should not be left uncompacted and exposed to moisture. Sealing the surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will help reduce the extent that these soils become wet or unstable. The contractor should cover all soil stockpiles that will be used as structural fill with plastic sheeting. Excavation The stability of open cut slopes is a function of soil type,groundwater seepage,slope inclination,slope height and nearby surface loads. The use of inadequately designed open cuts could impact the stability of adjacent ' work areas, existing utilities, and endanger personnel. The contractor performing the work has the primary responsibility for protection of workmen and adjacent improvements. In our opinion,the contractor will be in the best position to observe subsurface conditions continuously throughout the construction process and to GEOENGINEERS October 30,2009 ; Page 9 File No.0482.031-02