To meet the increasing water supply demands of the Lower Mainland and respond to significant population growth south of the Fraser River, Metro Vancouver undertook a significant upgrade to its water supply infrastructure. This included a new water supply tunnel across the Fraser River as well as new connecting water mains on the north and south sides of the river, all of which Golder has been working on since 2005.
When commissioned, the Port Mann Main No. 2 North will comprise a 1.5-m-diameter, 2.1-km-long water main extending from the Cape Horn Pump Station and Reservoir to the north shaft of the Port Mann Water Supply Tunnel. This upgrade will ensure the continued supply of water to residents and businesses in the region and meet the demands of projected population and economic growth for the next 75 years.
During construction of the new northern water main savings on costs and carbon dioxide emissions were realized as a result of the re-use of excavated soil as backfill. Weak and compressible organic soils along portions of the route needed to be stabilised to prevent settling. Golder’s recommended re-use of excavated spoil as backfill outside of the pipe-support zone, and through peaty sections of the route, offset the risks of large post-construction settlements in the organic soils and avoided 5,000 metres of imported fill and the associated trucking and compaction activity.
The pipeline route construction encountered sensitive bird nesting areas and the habitats of a number of rare species of invertebrates requiring rigorous environmental management planning to meet regulatory requirements and community expectations. An archaeological assessment was undertaken and a resultant management plan involved useful input from the local First Nation communities. During construction a collaborative effort between Golder and the First Nation communities ensured that excavated material was properly inspected for the presence of archaeological material.
This has been a five year project for Golder with commissioning expected in 2018.