10200 25TH AVE SE Geotech Report 2018-01-02 MF Import

i � Proposed Modernization and Additions ta Subsurjace Exploratian, Geologic Hazards, Eisenhower Middle Schoo[ and Geotechnical Engineering Report Everett, Washingmn Desirn Resom,r.endations PerL-neter footing drains should b� provided for all retaining walls as discussecl under the section on Drainage Considerations. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the wall. This would-involve installation of a minimum 1-foot-wide washed gravel blanket urain, H•4ich is continuous with the perimeter footing drain and extends to within 1 foot of:he ground surface. Lateral loads can be resist:d by friction between the foundation and the ti'.1, supporting strucmral fill, or by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill, compacted ro at least 95 percent of the maximum dry density, ro achieve t'�e minimum passive resistance shown in Table 2 for footings cast against structural fill. The presented values are allowable and include a safery facror of at least 1.5. 12.0 FLOdR SUPPORT Floor slabs are to be supported directly on dense till, recompacted existing fill, or on a 2-foot- thick structural fill mat. Alternatively, where deepened footings extending through unsuitable fill into dense till are utilized for foundation support, the slab may be designed as a structural slab and supported on the deepened foundation. Floor slabs should be constructed atop a capillary break material and a vapor barrier to limit moisture intrusion through the floor slabs. Areas of slab subgrade that are disturbed (loosened) during construction should be compacted to a non-yiefding condition prior to placement of capillary break material. The capillary break should consist of a minim�m thickness of 4 inches of washed pea gravel, with a 10-mil (minimum thickness) plastic vapor barrier on top o;the capillary break. ' 13.0 DRAIN.4GE CONSIDERATIONS It is possible that ground water or seepage may be encountered at shallow depths during the wetter months of the year. Therefore, the contra�tor should be prepared to provide temporary storm water collectio � n, stora,e, and disposal mechanisms as necessary prior to site work and durirg construction. Water should not be allowed to discharge over site slopes. All retaining and footing walls should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed pea gravel. The level of the perforations in the pipe should be set at die bottom of the footing at ail locations and the drain collectors should be constructed with sufficient gr&dient ro allow gravity discharge away Jniman �.3, 1��1 �fSSOG.�TEDE,IRTHSC/E�VCES, LVC. SIT IJ-AEOJ:IxaJ-P.u�rrtrCG7J,79iKEi«'P- R=X Pdge 19 �