Downer PipeTech were engaged to rehabilitate a pipeline designated as Pipe 3 of the Ipswich trunk watermain augmentation project within the Springfield water supply network. The project involved the sliplining and replacement of a 1.9km section of the existing DN450 glass reinforced pipe (GRP) trunk watermain located along Springfield Parkway at Springfield, from Bridgewater Road to Springfield Lakes Boulevard. The GRP trunk watermain had experienced 5 major failures in the Ipswich network within the past few years. This highlighted the high rate of historical failures experienced on GRP mains constructed in Ipswich throughout the 1990’s. An investigation of these recent failures had also identified anecdotal evidence that the construction techniques used at this time were not appropriate for construction of GRP pipes. The existing DN450 GRP trunk watermain that runs along Springfield Parkway is a strategic asset responsible for conveying flows from the Springfield Reservoir to the Springfield Lakes water supply zone.
A risk rating of ‘HIGH’ had been assigned to the Springfield watermain asset and as a result was considered critical. Key risk categories included customer service (during failure and repair), public health and WH&S (in the event of failure). The scope of work included the design and construction of the new trunk watermain along with the inclusion of a reticulation main, modifications to several valve pits and the reinstatement of all connections and associated fittings. The existing DN450 GRP main was sliplined with DN355 high density polyethylene (HDPE) pipes that had been butt welded to form pipe strings to accommodate each slipline installation. The longest section of main installed was completed in a single 750m pull. Minor components of the works included exhuming the existing DN450 GRP main with new DN450 ductile iron cement lined (DICL) pipework.