Design Optimisation of Resilient Stormwater Pump Stations

Following the Christchurch earthquake sequence of 2010 – 2011, areas of the city are now more prone to flooding due to ground settlement. The New Brighton Road and Owles Terrace catchments in eastern Christchurch now require pump stations to convey surface waters when gravity outfalls cannot operate during high tides. During the design process of the remedial works, value engineering and early contractor involvement (ECI) workshops have enabled a cost-effective and innovative design to be developed. This has provided significant savings over conventional vertical axial flow pump stations which require deep excavations and significant ground improvements. The final design includes use of horizontal axial flow pumps, lightweight wet well structures utilising pre-cast concrete units and minimal ground improvements. Additionally, hydraulic modelling identified that two smaller pump stations (of 800 l/s capacity each) provides a more cost-effective solution than one larger pump station and associated greater capital investment in the conveyance network. The design is now in construction. This paper provides valuable lessons to the industry on how to improve the design of these important and large stormwater pump stations.