July 6, 2009 - District of Mission

50Many seismic design methods, including the analysis of the stability of slopes during andshortly after an earthquake (seismic slope analysis4 ), are based on ground motions. Insome areas of British Columbia, the above change in design ground motions resulted inan approximate doubling of the peak around acceleration (PGA) used in seismic slopeanalysis.Using current practice, the effect of this change was to increase the number of slopesthat could be considered unstable during an earthquake, and therefore potentially notsuitable for residential .deveiopment. This caused concern to Land Owners,Development Consultants, losal governments, and the provincial government (Kuan20071As a temporary measure, the provincial government, by special regulation 'LocalGovernment Act, Section ,692(d), Provincial Regulation M268, Geotechnical SlopeStability - (Seismic) Regulation (December 20067, permitted the use of the NBCC 199Eand BCBC 1998 ground motions (ID% in 50-year pound motions) for seismic slopea.naiysis. As a result, APEGBC, with support from the provincial government,established a Task Force on Seismic Slope Stability (TFSSS) to study this issue and tomake appropriate recommendations.The TFSSS reviewed current practice and recent developments in seismic slopeanaysis These 20D revised Guidelines introduce two new methods of seismic slope,analysis of soil slopes based on the concept of tolerable earthquake-induced slopedisplacements alma a slip surface_ The 2008 revisions include the addition of a newChapter 4 and four Appendices (Appendix E, Appendix F, Appendix G and Appendix H)..Other minor revisions have also been made.1.1 PURPOSE OF THE GUIDELINESThis document (1) provides guidelines of professional practice for a ProfessionalEngineer and Professionai Geossientist wnc carries out a landslide analysis for aproposed residential development, and (2) provides guidance to the professional as tohow to relate the results of the analysis to a level of landslide safety for residentialdeve.looinent when required by provincial legislation. Appendix D to these Guidelinesprovides a Landslide Assessment Assurance Statement that must be submitted, alongwith a is stilde assessment report, to an Approving Authority.Land Owners and Devei-apment Consultants: Land Use Planners, Approving Officers .and Building inspectors: kriunicipalities Reg.'onal Districts, and the islands True; theprovincial gdemment; and the general public frequently rely on such iandsiideassessments. These Guidelines may also assist those parties.These Guidelines address typical project organLzation and respcns:blhies of the venousstakeholders; professional practices that should typically be provided: qualityassuranceiquaiit-y control, and professions registration and education, training andexperience.Seismis slope analysis ine-tudes both, seismic slope sability analysis and seismic slope dispiacementanalysis.Municipalities. Regi'onal District- and the islands Trust are coitectively referred to as lose coveminents.APEGEC *March 213:26.7:e0 se September 23E18Cjiiidetne,s Ledsisted Lanciai:ds oft sseavnent.io, Precasev Fez fiarekkopment Eritisi) Cation:WEPAGE 20 OF 73