2400 33RD ST GEOTECHNICAL INVESTIGATION 2018-01-02 MF Import

SC 130 Mi bar -Pita r[.19oan7ts, a1c We recommend that we be on site to observe the appropriate lift thickness and adequacy of the subgrade preparation. A sufficient number of in -place density tests should be performed as the fill is being placed to determine if the required compaction is being achieved. 5.1.4 Wet Weather Work The native clay soil is highly moisture sensitive and will be difficult to traverse with construction equipment during periods of wet weather or wet conditions. Furthermore, the near -surface fill soils may be difficult to compact if their moisture content significantly exceeds the optimum. General recommendations regarding wet weather work are presented below. • Earthwork should be performed in small areas to minimize exposure to wet weather. Excavation or the removal of contaminated or unsuitable soil should be followed promptly by placement and compaction or clean structural fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. Under some circumstances, it may be necessary to excavate soil with a backhoe to minimize subgrade disturbance caused by equipment traffic. • Material used as structural fill should consist of clean, granular soil with less than 5 percent passing the U.S. Standard No. 200 sieve, based on wet sieving the fraction passing the '/4-inch sieve. The fine-grained portion of the stmctural fill soil should be non -plastic. • The ground surface within the construction area should be graded to promote runoff of surface water and to prevent the ponding of water. • The ground surface within the construction are should be sealed by a smooth drum vibratory roller, or the equivalent, and under no circumstances should soil be left uncompacted and exposed to moisture. • Excavation and placement of structural fill material should be under the full time observation of a representative of MPA, to determine that the work is being accomplished within the project specifications and the recommendations contained herein. • Bales of straw and/or geotextile silt fences should be strategically located to control erosion and the movement of soil. 5.2 Seismic Design Criteria 5.2.1 General The project site lies within Seismic Zone 3 as defined in the International Conference of Building Officials 1997 Uniform Building Code (UBC). Zone 3 includes the Puget Sound region and represents an area of relatively high seismic risk. For comparison, much of California and Southern Alaska are in Seismic Zone 4, which is one of the highest seismic risk zones. Consequently, moderate levels of earthquake shaking may be anticipated during the design life of the Station. Assuming the building is supported on the glacially consolidated deposits (advance outwash or till) that were observed approximately 20 feet below the surface in our explorations, UBC Soil Type Sc may be use,i for the site. Using, the American Geoleclukal, Tunlxl and E nwonmental Fngux= 3080 1256 Ave NE Phone (425) 8693778 M levve, WA 98005 Page 8 Fax (425) 961-0677