1004 BROADWAY EVCC STUDENT HOUSING - REPORTS & FINAL DOCUMENTS 2017-01-13

Gcotechnical Report - ___ . ised Proposed Apartments: 1002, 1006, and ] 008 Broadway Strcet, Evcrett, Washinbton May 12, 2015 3.4 GROUNDWATER Groundwater seepage was not encountered in our borings or hand augers. The till underlying the site generally has low permeability and perched groundwater may develop in lenses of more permeable soil within the till forination. If encountered, we anticipate groundwater seepage rates will be light. There will be fluctuations in seepage depending on the season, amount of rainfall, surface water runoff, and otller factors. Generally, the water level is higher and seepage rates are greater in the wetter, winter months (typically October through May). 4.0 GEOTECHNICAL RECOMMENDATIONS 4.1 SEISMIC DESIGN PARAMETERS The 2012 International Building Code (IBC) seismic design section provides a basis for seismic design of structures. Table 1 below provides seismic design parameters for the site that are in conformance with the 2012 IBC, which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. Table 1— Seismic Design Par�meters Spectral Spectral Design Spectral Site Control Periods Site Acceleration Acceleration Coefficients Response [sec.] Class at 0.2 sec. [g] at 1.0 sec. [g] Parameters SS S� F� F� S�s S�, T� TS C 1.264 0.481 1.000 1.319 0.843 0.423 0.100 0.502 The spectral response accelerations were obtained from the USGS Earthquake Hazar•ds Program Interpolated 1Probabilist%c Csround Motion website (2008 data) for khe project latittide and longitude. Liquefaction Potential: Liquefaction is a process that can occur when soils lose shear strength for short periods of time during a seismic event. Ground shaking of sufficient strength and duration results in the loss of grain-to-grain contact and an increase in porc. water pressin�e, causing the soil to behave as a fluid. Soils with a potential for 1�-048 1008 Broadway, Rcviscd Pa�Te 5 Pat1GE0, lnC.