Tarro to Shortland - Trunk Watermain

Hunter Water Corporation

Northwest of Newcastle, New South Wales, Australia

Built on the success of the Ash Island Trunkmain project, Diona secured a further contract to replace an existing pipeline from Tarro to Shortland. This project was located primarily within the Hexham Swamp and Nature Reserve. 

The original pipeline is operated by Hunter Water, delivering water from Dungog Treatment Plant to the Maitland and Cessnock systems, as well as forming a crucial link between the Newcastle and Maitland systems. Diona’s responsibility was to design and construct the new 7.4km pipeline and remove 8.1km of the original pipeline.

Effective management of environmental issues

The project involved a number of environmentally complex issues, including existing acidic and in some cases contaminated groundwater, and the site’s alignment with extensive wetlands and mangrove communities.

Diona prepared a water treatment plan to comply with environmental requirements. This involved recharged contaminated water in the landfill site, and treatment of all acidic water prior to release into the sensitive surrounding environment.

The soft, wet soils of the wetlands presented additional engineering challenges and the wetlands also supported endangered species and endangered ecological communities. It was necessary for Diona to block several fish passageways, and cross sections of green and gold bell frog habitat, which was done in accordance with NSW fishery requirements.

To restore mangrove areas within the construction zone, a small detention basin, open to tidal inundation, was created within the project area, providing conditions consistent with a normal mangrove growing environment. Mangrove plants in the path of the excavation that needed to be removed were stored in this basin, and then replaced when works were completed. This allowed for rapid reestablishment of the original plant community, using local material.