Whangarei District Council decided to extend the district's sewer reticulation network around Whāngārei Harbour, to improve water quality in the popular recreational spot.
Starting in the year 2000, the physical works extended along the northern shoreline of the harbour from Waikaraka to Urquharts Bay near the harbour entrance – where the septic tank systems often failed to treat sewage to an acceptable standard.
In late 2008, United Civil completed the third stage of this sewerage reticulation scheme, a $14.4m development that won a New Zealand Contractors Federation Construction Excellence Award in 2009.
Completed over a period of two years, the scope of this project included construction of:
- 15 pumping stations and associated emergency storage facilities, electrical control and telemetry systems
- 23,000 metres of pressure pipeline using polyethylene pipe of diameters up to 280mm
- 13,500 metres of gravity pipelines
- 230 manholes
- individual connection to 476 properties
- miscellaneous associated works including landscaping, retaining structures and pipe bridges.
Key features included:
- extensive use of alternative construction methods (particularly directional drilling), to install pipeline with minimal disruption to landowners
- constructing wet wells and emergency storage facilities (up to eight metres below water level) immediately adjacent to an environmental sensitive coastal marine area
- constructing pipelines in areas of high archaeological importance and cultural significance
- works were located in a coastal urban environment, where conditions were not conducive to easily installing pipelines and pump stations – in particular, the hard underlying basalt rock often made the excavation of trenches a difficult and time consuming exercise.
United Civil also undertook construction work on the first and second stages of the overall scheme.