The Highlands Source Project: new approaches for new challenges

Severe drought and an extended period of water restrictions have seen the innovative response of the Highlands Source Project, a major initiative to secure the city of Goulburn’s water supply.

The Highlands Source Project (HSP) began when a New South Wales Premier’s taskforce recommended the project as an emergency water supply solution. The $50 million project attracted funding from both the state and federal governments of 80 per cent of the project cost, with the remainder supplied by the Goulburn Mulwaree Council.

Between 2006 and 2009, the Goulburn Mulwaree Council carried out an integrated water cycle management study which looked at a range of options to secure Goulburn’s water supply. The HSP was determined as the best overall solution to address this issue.

Project parameters

The HSP involves the design and construction of an 80 km pipeline and pump station between the Wingecarribee Reservoir in the Southern Highlands of NSW, and the City of Goulburn. It impacted 145 properties and numerous public roads and river crossings, and traverses a variety of terrain types and land uses.

The 80 km pipeline is composed of approximately 49 km of 375 mm diameter glass-reinforced plastic (GRP) pipe and approximately 31 km of 300 mm diameter GRP pipe. The pipe was supplied by Promains Pty Ltd and was manufactured by Fibrelogic (375 mm diameter) and Superlit (300 mm diameter). The pipe was supplied in a mixture of PN16 and PN25 pressure grades to suit the hydraulic requirements of the design.

The project was designed by engineering consultants GHD Pty Ltd and managed by Hunter Water Australia Pty Ltd on behalf of the Goulburn Mulwaree Council .

The pipeline construction contract was awarded to Leed Engineering and Construction in December 2010, who mobilised to site in January 2011 and commenced pipelaying activities on 1 March 2011.

An innovative approach

The HSP was designed and constructed within a tight timeframe. The project start date was initially delayed due to some community concern about the scale of the project and doubts about the significance of Goulburn’s water security issue. This made for a tight delivery timetable, which resulted in an innovative approach to project delivery.

Goulburn Mulwaree Council awarded a contract to GHD for the design of the project in November 2009. In a period of only 12 months, GHD carried out field investigations; prepared a comprehensive environmental assessment and sought and received the necessary project approvals; assisted council in negotiating land access agreements with 145 landholders; carried out community consultation activities; and, prepared the design and contract documentation for the pipeline and pumping station.

The delivery timeframe was only achieved by running multiple activities in parallel, requiring close collaboration between staff from Goulburn Mulwaree Council, GHD and Hunter Water Australia. This collaborative approach was carried through to the construction phase, with the council’s selected contractors actively assisting the project management team in resolving land access and environmental constraints, particularly during the construction phase.

Another innovation involved Leed Engineering’s use of excavator-mounted, hydraulically-powered screening buckets to condition the in-situ trench material for re-use as pipe bedding.

“Where favourable granular ground conditions were encountered, this technique resulted in increased productivity, reduced truck movements on public roads and a 50 per cent reduction in the use of imported quarry products,” said Project Manager Christian Leah.

Overcoming challenges

The pipeline was constructed across agricultural land in private ownership, with a diverse range of uses.

“Responding to landholder concerns was key to the project’s success,” said Mr Leah. “The approach developed for the HSP could be applied to other linear projects.”

Each landholder had unique views about land management, so a major challenge for the project team was responding to landholder concerns about the impact of the works and the rehabilitation of
the land.

“The team adopted an approach to route selection based on technical merit to reassure landholders that there was a technical justification for the location of the pipeline on their property. “Close collaboration with the contractor also helped to ensure that impacts on landholders during construction were minimal,” Mr Leah added.

The project team adopted a science-based approach to rehabilitation by carrying out pre-construction agronomy assessments on each property and defining the proposed approach to rehabilitation in consultation with each landholder.

Environmental challenges related mainly to the impacts of vegetation removal and construction work within waterways.

“The project team worked hard during design and construction to minimise the amount of vegetation removed, which resulted in only 11 hectares of vegetation being removed along the entire alignment,” said Mr Leah.

“It was rewarding to see the care of the contractors in minimising vegetation removal and to see mature trees left untouched within the construction zone.”

A risk-based approach was used in relation to waterway crossings to ensure that all waterways could be reinstated to their pre-construction condition. Soil Conservation Service of NSW was engaged to provide specialist advice on the rehabilitation of waterways.

The Cultural Heritage Community was also strongly supportive of the project’s aims throughout design and construction, and worked closely with the project team in carrying out field investigations and salvaging artefacts.

A final challenge was posed by the pipeline’s position adjacent to existing service corridors containing the Moomba to Sydney gas pipeline operated by APA Group, a Sydney-Melbourne trunk fibre optic cable owned by AAPT, while overhead there were 33 kilovolt-ampere power transmission lines operated by Transgrid.

These service constraints required the support of the asset owners and contractor to safely construct the HSP pipeline. Measures put in place included segregation fencing of the gas pipeline assets for over 50 km and agreed offsets from potholed locations of fibre optic assets.

The HSP pipeline completed construction in September 2011.

Mr Leah reflected on this achievement: “The HSP was always challenging, sometimes difficult, but ultimately rewarding. Everyone involved is rightly proud of their contribution to delivering an important public work on budget and to a tight timeframe.”

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