1315 MADRONA AVE 2016-01-01 MF Import

Geotechn�cal Engineering F�pert 1313 Madrona Avenue Everett, Washi�igton �vtarch 11, 2013 RN File No. 2793-OOtA Page 5 Seismic Hazard: It is our opm�on bzsed on our subsurface explorations Ihat the Soil Profde m accordance with the 2009 and 2012 International Bwlding Code (IBC) is Site Class C wrth Seismic Design Category D. We us�d the US Geological Survey program "U.S. Seismic Design Ivlaps V1'eb Applic2tion." The design maps summary reports for the 20G9 and 2012 IBC are included m Ihis report as Appendix A. Additionat seismic considerations include liquefaction poteniial and ampllfication of ground motions by soft soil deposits. The liquefaction potantial is highest for loose sand with a high groundwater table The underlying dense glacial drift and adeance outwash soils are considered to have a very low potenual for liquefaction and ampli(ication of ground motion. Site Preparation and Grading The (�rst step of srte preparation should be to strip the vegetation, topsoil, or loose soils to expose medwm dense or fumer natrve soils in pavement and bwlding areas. The excavated matenal should be removed from the site, or stockpiled for later use as landscaping (ill The resulting subarade shou:d be compact�d to a iirm, non-y�elding condition. Areas observed to pump or yield should be repaired prior to placing hard surfaces. The on-site glacial drift likely to be exposed during consiruction is considered highly moisture sensitive, and the surface will disturb easily when wet �Ne expect these soils would be difficult, if not impossible, to compact to structural (ill specifications in wet weather. We recommend that earthwork be conducted during the drier months. Additional expenses of �vet weather or winter construction could include extra excavation and use of imported fill or roch spalis. During wet weather, alternative site preparation methods may be ne�essary. These methods may include utihzing a smooth-bucket trackhoe to complete site stripping and diverting construction Iraffic around prepared subgrades. Disturbance to the prepared suhgrade may �e mmimrzed 6y placing a blanket of reck spails or imported sand and gravel in traf(ic and roadway areas Curoii drains or ditches can also be helpful in reducing gradiny costs during the wet season. These methods can be evaluated at the t�me of consUuction. Structural Fill General: All fdl placed beneath buildmgs, pavements or other setdement sensitive features should be placed as structural (ill. Siruclural (ill, by dehni�ion, is placed in accordance wi�h prescribed methods and standards, and �s observed by an experienced geotechnical professional or soils technician. Field observauon procedures would include the per(onnance of a representauve number of implace densiry tests to document the atta�nment ci the desired degree of relative compacuon. Materials: Imported structural fill should consist of a good quality, free•draining granular soil, free of organics and otiier deletenous material, and be well graded to a maximum size o( about 3 inches. Imported, all-weather structural fill should contain no more than 5 perceni fines (soil finer than a Standard U.S. No. 200 sieve�, based on that iracUon passing ihe U.S 3/4-inch sieve. The use of on-site soil as structural fill will be dependent on moi,ture content control. Some drymg of the native soils may be necessary in order to achieve compaction. During warm, sunny days this could be accomplished by spreading the matenal in thin Irfts and compaciing. Rabinson Noble, Inc