Perth City Link Rail

NPE was contracted with the Perth City Link Rail Alliance to provide a detailed design, construct and supply, operate and maintain a dewatering and water treatment system for the Pedestrian underpass, the 620m cut and cover tunnel and the approach ramps between the heritage listed Horseshoe Bridge and Milligan Street.

The scope involved design and installation of deep well dewatering system in order to maintain the pumping rate at a minimum rate in order to reduce disposal cost. Design, installation and maintenance of reinjection wells were completed to a certain pressure in order to mitigate any offsite settlement of existing infrastructure including the live rail tunnels. Maintaining the water table on the external part of diaphragm wall within 1m of seasonal high or low, was done to comply with the stringent Department of Environment and Conservation guidelines. At the peak of the project, the system was dewatering up to 70 l/s with a 55 l/s to onsite recharge wells and 15 l/s was pumped to the offsite settlement basin located approximately 1 km off site. The extracted water was treated for pH and removal of metals to less than 1 mg/l to meet the environmental guideline prior to reinjection back to the aquifer and disposal to stormwater system.

This project was closely monitored and effectively managed by experienced project management team comprised of Project Managers, Engineers, Environmental Scientists, Water Treatment Specialist. A 24 hour alarmed monitoring system with afterhour’scallouts was also utilised on site.