9001 AIRPORT RD SNO ISLE SKILL CTR EXPANSION 2009 Geotech Report 2018-01-02 MF Import

I I Subsurface Fxpbration, Geobgic Hauud, and Sna/sle Skills Center Addition Preliminnry Geotechnicd Engineerirtg Report Everett. Washingron Ceologic Hawrds and Mitigations I6 2 Seismicallv Induced I.andslides I There were no significant slopes on the site. Therefore, shallow and deep-seated, seismically induced landsliding is unlikely, and no mitigation efforu aze recommended. I63 Liquefaction I The encountered stratigraphy has a low potential for liquefaction due to the high strengt6 of the glacially consolidated neaz-surface lodgement till soiis, and the lack of widespread ground water. No liquefaction mitigation efforts aze tecommended. � 6.4 Ground Motion I Structural design of the buildings should follow 2006 IBC standazds using Site Class "C", as defined in Table 1613.5.2. The 2006 IBC seismic design pazameters for short period (Ss) and I i-second period (S�) specual acceleration values were determined by the latitude and longitude of the project site using the USGS National Seismic Hazazd Mapping Project website (http://earthquake.usgs.�ov/hazmaps/). The USGS website interpolated ground motions at the i project site to be 1.256g and 0.44g for building periods of 0.2 and 1.0 seconds, respectively, with a 2 percent chance of exceedence in 50 yeazs. Using the mapped specual acceleration in conjunction with the identified site class, information presented in Tables 1613.53(?) and � 1613.53(2) indicates site coefficients F� = 1.0 and F� = 1356 aze recommended for use in site seismic design and analysis. l 7.0 EROSION HAZARDS AND MITIGATION I As of October 1, 2006, the Washington State Depattment of Ecology (Ecology) Coastruction Storm Water General Permit (also known as the National Pollutant Discharge Elimination System [NPDES] permit) requires weekly Temporary Erosion and Sedimentation Control I (TESC) inspections for all sites 1 or more acres in size that dischazge storm water to surface waters of the state. The TESC inspections must be completed by a Certified Erosion and � Sediment Control Lead (CESCL) for the duration of the conswction. TESC reports do not need to be sent to Ecology, but should be logged into the project Storm Water Pollution Prevention Plan (SWPPP). If the project does not require a SWPPP, the TESC reports should i be kept in a file on-site, or by the permit holder if there is no facility on-site. Ecology also , requires weekly turbidity monitoring by a CESCL of storm water leaving a site for all sites 5 acres or greater. Ecology requires a monthly summazy report of the tutbidity monitoring results (if performed) signed by the NPDES permit holder. If the monitored turbidity equals I or exceeds 25 nephelometric turbidity units (NTU) (Ecology benchmazk standard), the project best managemznt practices (BMPs) should be modified to decrease t6e turbidity of storm water Ileaving the site. Changes and upgrades to the BMPs should be continued until the weeklY ��Q�� 2� ASSOC/ATFD F.iRTN SC/ENCES, lNC. � IEGlld-EE080213A5-Projenr1200l02i31EEiWF Page 6