Drilling under Avoca Lagoon: a technical triumph

Ever pondered the intricacies of subaqueous drilling to maintain vital water infrastructure? A recent project managed by Eire Constructions under Avoca Lagoon has showcased cutting-edge solutions to a complex challenge.

Ever pondered the intricacies of subaqueous drilling to maintain vital water infrastructure? A recent project managed by Eire Constructions under Avoca Lagoon has showcased cutting-edge solutions to a complex challenge.

Situated along the New South Wales Central Coast, a region celebrated for its beaches – the area boasts an intricate network of waterways, including the Hawkesbury River to the south and Lake Macquarie to the north. This abundance of waterways adds complexity to water and wastewater management. Eire Constructions, in collaboration with its specialist contractor Superior HDD, recently undertook the task of drilling a 400-meter-long pipe tunnel beneath the 290 megalitre Avoca Lagoon—a critical infrastructure endeavour for client Central Coast Council.

Project overview

Central Coast Council‘s strategic initiative involved replacing the aging water transfer trunk main beneath Avoca Lagoon, which is crucial for supplying the Copacabana Reservoir. This trunk main serves North Avoca, Avoca Beach, Copacabana, and Macmasters Beach, providing essential water services. This project was designed to mitigate environmental risks, provide capacity for the growing region and ensure a continuous water supply.

Christopher Achelles, Eire Construction’s Site Supervisor, noted the urgency of replacing the water main due to its pivotal role in regional water distribution. The existing system’s fixed joint on the north side and flexible joint under the lagoon, affected by tidal movements, led to sporadic disruptions. Eire Constructions, leveraging Superior HDD’s horizontal directional drilling (HDD) expertise, executed a complex drilling operation to a depth of approximately 23.5 meters. They successfully pushed a 560 millimetre pn20 poly pipe in 12-metre sections through a nearly 400-meter-long underbore, securing it to the casing on the north side. This new connection is designed to provide a stable, long-term solution.

Technical challenges and solutions

One of the principal challenges was the high water table in this low-lying area. Recent precipitation had elevated the water table to near lake capacity levels, increasing the risk of frac outs—the uncontrolled release of drilling fluid during HDD operations. Such incidents could have caused significant environmental contamination.

To mitigate these risks, rigorous sediment control measures were implemented to prevent mud or sediment discharge into the lagoon. Environmental safeguards were paramount, particularly due to the habitat of endangered green and golden bell frog (GGBF) species. Comprehensive pre-project planning with Central Coast Council, including the engagement of specialised contractors, ensured adherence to environmental regulations and site protection.

Stakeholder engagement:

Effective communication with the Central Coast Council and local residents was vital. Eire Construction, guided by its family-owned values, prioritised a collaborative approach. Central Coast Council implemented their community liaison plan, which involved meticulous signage, public notifications, and online updates to manage community impact and maintain transparency.

Safety measures included extensive signage and fencing around the construction site, adjacent to a large oval and children’s play area. Proactive engagement with the local community, including addressing concerns of the local rugby club and interacting with local children, helped minimise disruptions and fostered positive relations.

Project reflections:

Reflecting on the project’s success, Achelles emphasises the importance of strategic team planning and cohesive execution.

“The success of the project hinged on comprehensive planning and collaborative effort,” he said. “Our team consisted of Project Engineers Dave Fox and Andrew Bennett, and their commitment to executing the plan and making informed decisions was crucial in achieving our objectives efficiently.”

Working effectively with the Central Coast Council project team, Glenn Crocker and Justin Parker, was pivotal to the success of the Avoca Lagoon project. Their proactive engagement and deep understanding of local needs were instrumental in navigating the complex logistics and regulatory landscape.

The Avoca Lagoon project exemplifies Eire Constructions’ technical proficiency and collaborative style. The team showcased the effort necessary to address complex infrastructure challenges, setting a benchmark for future endeavours in water management and construction.

For more information about Eire Constructions, visit eirecon.com.au

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