The municipality of Halifax was releasing 180 ML of untreated wastewater into one of the world’s largest deepwater, ice-free harbours each day. To remedy this situation, three sewage treatment plants were completed over a seven-year period. We provided specialized geotechnical engineering services throughout the design phase for each plant. During construction, our personnel were on-site to observe the excavation, foundation construction, installation of rock anchors, and placement of fill materials and concrete.
For the Halifax plant, we contributed to the design of the rock anchor system that supported the rock faces during excavation of a 30-metre deep wet well in variable quality bedrock and resists the large hydrostatic forces behind the walls and beneath the floor slab. A kilometre-long consolidation tunnel collects wastewater from several pipelines and delivers it to the plant. We completed the geotechnical investigation and provided design parameters and site specific stabilization measures for the tunnel exit point. For the Dartmouth plant, we inspected the dynamic compaction operations used to compact the loose fill material, which ranged in thickness from 2 to 10 metres.