To satisfy the current and more stringent Building Code seismic design standards, the Ministry of Transportation and Infrastructure is carrying out a seismic safety retrofit of Mission Bridge No. 2317 which spans the Fraser River between Mission and Abbotsford, BC. As part of the rehabilitation, ground improvement is required around the foreshore pile supported Pier S4 and the inland S10 abutment fill.
Phase 3 of the project involved the installation of Vibro Replacement stone columns using wet top-feed methods. Stone columns were required to extend to a maximum depth of 29m at Pier S4 and to 17m at Abutment S10. Menard Canada utilized different stone column spacings and construction procedures for the two treatment areas to account for the varying soil conditions in order to achieve the Engineer’s performance specification requirements. The S4 site was located in a public parkland where Menard Canada acted as the project’s General Contractor and carried out all site preparation and restoration which included removal/reinstatement of rip-rap material at Pier S4 and slope restoration at Abutment S10 following stone column installation within the embankment slope. Menard Canada carried out an extensive bridge monitoring program to measure displacements of the bridge foundations on a daily basis which showed negligible movement. Extensive environmental monitoring was also required to protect the sensitive foreshore parkland as well as fish bearing drainage ditch system surrounding the Abutment S10. Three Vibro rigs were utilized within the small treatment areas to meet the client’s demanding schedule.