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SHANNON 6WILSON,INC. <br /> wood, clasts of fine organic material, or very fine organic particles. Locally, the unit <br /> is interlayered with nonglacial lacustrine (lake) deposits (Qpnl). Qpnl was <br /> encountered in the last sample obtained from boring B-2. <br /> Our generalized subsurface profile (A-A') presented in Figure 3 includes the geologic unit <br /> designations listed above as well as graphical representations of the boring logs and SPT <br /> measurements. <br /> Information about the groundwater level behind the bulkhead is not available because no <br /> monitoring wells were installed for the project. We anticipate that the groundwater level is <br /> influenced by tidal fluctuation and may be as high as elevation +1 1 feet. <br /> 4.0 ENGINEERING STUDIES AND RECOMMENDATIONS <br /> Based on the subsurface conditions encountered in the field explorations and our understanding <br /> of the project, we performed engineering studies to develop geotechnical recommendations for <br /> the design of the new bulkhead. Prior to the preparation of this report, we provided information <br /> and analysis results to MNE in e-mails and telephone conversations. We also prepared the <br /> following letters related to this project: <br /> ■ November 30, 2012: Geotechnical Review of Open Cell Bulkhead Proposal by PND <br /> Engineers <br /> ■ January 29, 2013: Revised Lateral Earth Pressures for Low Level Earthquake and <br /> Lateral Earth Pressure Comparison <br /> ■ April 16, 2013: DRAFT Risk Evaluation for Bulkhead Damage During 2,500-year <br /> Design Earthquake (submitted by MNE to the Port.for revienv) <br /> These letters were submitted to the Port and MNE. Where applicable, information provided in <br /> these letters is incorporated into this report. The recommendations in this report supersede the <br /> recommendations provided via e-mail correspondence or telephone conversations. <br /> 4.1 Seismic Design <br /> At the request of MNE and the Port, we evaluated two earthquake ground motion levels: <br /> ■ International Building Code(IBC) Design Ground Motion: We understand that <br /> the structural design of the bulkhead was originally going to be performed using IBC <br /> guidelines to allow for future development behind the bulkhead. The 2009 IBC <br /> specifies that seismic design be performed using a ground motion with a return period <br /> of 2,475 years. For this seismic design level, we anticipate that the soil between the <br /> 21-1-21761-003-R I f.docz/wp/clp 21-1-21761-003 <br /> 7 <br />