1400 W MARINE VIEW DR WATERFRONT PLACE APARTMENTS Geotech Report 2022-10-25

Fill Placement and Compaction Criteria Structural fill should be mechanically compacted to a firm, non-yielding condition. Structural fill should be placed in loose lifts not exceeding 1 foot in thickness. 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: • Structural fill placed in building areas (around foundations or below slab-on-grade floors) should be compacted to at least 95 percent of the MDD estimated in general accordance with ASTM D 1557. is Structural fill placed in pavement and sidewalk areas (including utility trench backfill) should be compacted to at least 95 percent of the MDD estimated in general accordance with ASTM D 1557. ■ Structural fill placed against subgrade walls should be compacted to between 90 and 92 percent. Care should be taken when compacting fill against subsurface walls to avoid over-compaction and hence overstressing the walls. We recommend that GeoEngineers be present during probing of the exposed subgrade soils in building and pavement areas, and during placement of structural fill. We will evaluate the adequacy of the subgrade soils and identify areas needing further work, perform in-place moisture-density tests in the fill to verify compliance with the compaction specifications, and advise on any modifications to the procedures that may be appropriate for the prevailing conditions. Weather Considerations During wet weather, some of the exposed soils could become muddy and unstable. If so affected, we • recommend that: ■ the ground surface in and around the work area should be sloped so that surface water is directed to a sump or discharge location. The ground surface should be graded such that areas of ponded water do not develop; • slopes with exposed soils should be covered with plastic sheeting or similar means; • 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 reduce the extent to which these soils become wet or unstable; and • construction activities should be scheduled so that the length of time that soils are left exposed to moisture is reduced to the extent practicable. Methane Considerations Based in the Port of Everett's final EIS dated May 2005, methane gas is present in the subsurface soils due to the presence and decomposition of the wood waste. Methane gas has the potential to accumulate in subsurface structures, voids and vaults at concentrations that pose a risk for explosion or oxygen depletion.Thus, development planning and design will need to address the potential presence of methane gas, and if present,accumulation in subsurface structures and voids. Recommended Additional Geotechnical Services • GeoEngineers should be retained to review the project plans and specifications when complete to confirm that our design recommendations have been implemented as intended. GEOENGINEERS May 31,2017 ; Page 15 File No.22360-003-00