Whangarei Heads Sewerage Scheme (WHSS)
In 2000, the Whangarei District Council embarked on a programme of physical works to extend the districts sewer reticulation network along the northern shoreline of the Whangarei Harbour, from Waikaraka on the outskirts of Onerahi, to Urquharts Bay near the ocean entrance to the harbour.
A primary aim of the scheme was to improve water quality in the lower reaches of the harbour where the septic tank systems in use were often failing to treat sewage to an acceptable standard. This would be done by collecting domestic wastewater and pumping to the WDC treatment facility in Kioreroa Road.
In late 2008, United Civil Construction completed the 3rd stage of this sewerage reticulation scheme, a $14.4 million dollar development, and what was the largest-ever ratepayer funded contract let by the WDC. Completed over a period of two (2) years, the scope of this project included the construction of the following;
- 15 pumping stations and associated emergency storage facilities, electrical control and telemetry systems.
- 23,000m of rising main (pressure pipeline), using polyethylene pipe of diameters up to 280mm.
- 13,500m of gravity pipelines.
- 230 manholes.
- Individual connection to 476 properties.
- Miscellaneous associated works including landscaping, retaining structures and pipe bridges.
The works were located in a coastal urban environment and often in areas where the topography and underlying soil conditions were not conducive to the easy installation of pipelines and pump stations. In particular, the hard underlying basalt rock often made the excavation of trenches a difficult and time consuming exercise.
In addition to its size and abbreviated contract period, key features of the project included;
- The extensive use of alternative construction methods, and in particular directional drilling, to install pipeline so as to minimise disruption to landowners.
- The construction of wet wells and emergency storage facilities (up to 8m below water level) immediately adjacent to an environmental sensitive coastal marine area.
- The construction of pipelines in areas of high archaeological importance and cultural significance.
In addition of this 3rd stage, United Civil was also the company that undertook construction of the previously completed 1st and 2nd stages of the overall scheme!
Now, nearly a decade after the commencement of this work programme, United Civil can reflect with satisfaction on our involvement in not only a job well done, but in particular, a project that provides significant public health benefits to our community and all others who experience the beauty and amenity of the Whangarei Harbour.
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