1329 MADRONA AVE Geotech Report 2022-10-25

• Subsurface Exploration,Geologic Hazard,and Janowicz Property Geotechnica!Engineering Report Everett,Washington Preliminary Design Recommendations o Passive equivalent fluid equal to 150 pcf triangular pressure distribution should be applied to two pile diameters within the medium dense to dense landslide deposits to a depth of about 28 feet. Includes a factor of safety equal to 1.5. • Passive equivalent fluid equal to 300 pcf triangular pressure distribution should be applied to two pile diameters within the hard silt soils below the landslide deposit. Includes a factor of safety equal to 1.5. • A load reduction of 50 percent may be applied to the pile lagging due to soil arching. if used as temporary shoring we do not anticipate that the soldier piles will support significant vertical loads aside from those generated by inclined tiebacks. For design purposes,the vertical load capacity of soldier piles should be determined based on an allowable skin friction of 400 pounds per square foot(psf) and an allowable end bearing of 10 kips per square foot (ksf). The minimum depth of embedment should be determined by the structural engineer to satisfy vertical load bearing and lateral moment equilibrium. However, ail piles should be embedded at least 10 feet into the hard silt soils below the base of the retained zone to prevent"kickout." All soldier piles should be backfilled with concrete or lean mix after drilling and installation. The backfill above the excavation base elevation could consist of lean mix concrete or controlled density fill (CDF) to facilitate installation of lagging. Prompt and careful installation and backfilling of lagging will reduce potential loss of ground. Requirements for lagging should be made the responsibility of the shoring subcontractor to prevent soil failure, sloughing, and loss of ground, and to provide a safe working condition. We recommend any voids between the lagging and the soil should.be backfilled. However, the backfill should not allow potential hydrostatic buildup behind the wall. Drainage behind the upper wall must be maintained. To help reduce the likelihood of soil migration from behind the lagging,we recommend the use of a%-sack cement sand slurry for filling the voids behind the lagging. It is likely that the soldier pile holes will encounter groundwater within the retained soils unless dewatering is performed. The contractor should be experienced with the installation of soldier piles and tieback anchors. If caving conditions or significant seepage is encountered, the contractor should be prepared to case the holes. If the pile borings encounter obstructions that • cannot be removed or drilled through, they may need to be moved. Relocated piles may require additional pile(s) to compensate for the relocation. Any relocation of piles should be first approved by the structural engineer. Soldier pile wall construction should begin with installation of all of the soldier piles. When ail piles have been installed and the concrete is cured, removal of the existing wall can begin. Treated timber lagging should be installed as the wall removal or additional excavation progresses. When wall removal/excavation reaches the elevation of planned tiebacks, we recommend that the excavation not be advanced more than 2 feet below a planned tieback until the tieback is installed, tested, and locked off at the design load. Permanent wall May 10,2018 ASSOCIATED EARTH SCIENCES,INC. NSAd-170649E002-2-Pro)ects12O17O649tKE}WP Page 15