Works on site ceased while calculations to allow the pipeline to be installed deeper were confirmed. Historical geotechnical borehole logs and seismic data inferred that the rock profile was horizontally planed, but during the pilot hole construction an ancient paleo channel was encountered, resulting in potential fluid loss given the extended length of the bore. Casing installation was successfully completed to 129m from the rig, utilising a variety of methods and casing sizes.Īs works were in close proximity to residents and sensitive receivers, both working hours and noisy activity were tailored to help reduce impact and minimise disruption, providing respite where the drilling and construction processes would allow.Ĭommencement of the pilot bore, the guided portion of the HDD works, started as planned and proceeded well until approximately 550 metres out from the drill rig. Additional geotechnical boreholes undertaken during the design phase had shown loose soils, gravel and cobble present and informed a casing length of up to 130m – a length never previously undertaken by UEA. In order to help manage the unstable and problematic overlying ground conditions, steel conductor casing was seated fully into rock from the entry side to prevent both the intrusion of overlying soils and the escape of drilling fluids to the sensitive marine environment. The critical path of the project (1,410m in length) had always been the major HDD crossing of the Shoalhaven River and we expected to encounter a mixed bag of ground conditions including sand, silt, clay, gravel, cobble and hard metamorphic rock. Responsible for the end to end construction of the nearly three kilometre pipeline, UEA established site compounds – one with an engineered sound wall – and commenced construction to condense the already ambitious works program. As our team was involved from the beginning, we developed a comprehensive understanding of the project which created an ease and level of trust between the client, principal and contractor so works could progress without delay.
The letting of Milestone 6 to UEA was a fulfilling achievement given the level of works put into the pipeline design from initial concept and through all design phases. This collaborative process was undertaken over an extended period of time, allowing input from the overall client, contractors, operators and impacted stakeholders. Milestone 5 required the development of the overall Bomaderry to Nowra pipeline taking the plans through to a 100% Issue For Construction design based on further geotechnical data, consultation with stakeholders, review of suitable pipeline materials, performance criteria and construction methods. Although not a mandatory part of the overall scheme, the Bomaderry to Nowra transfer pipeline had several significant hurdles to overcome before being approved for construction.
Contracted by UGL for Shoalhaven Water, UEA’s involvement in the project commenced with early contractor involvement, through to tender submission, optioneering and then into the overall construction phase. UEA’s engagement on the project was specifically around two distinct deliverables: Milestone 5, the performance of the Pipeline Design Development Services, and Milestone 6, including the construction and commissioning of the proposed pipeline connecting the Bomaderry WWTP to the Nowra WWTP. UEA’s work under contract included a 2.9km transfer main to allow reclaimed water to be transferred between Bomaderry and Nowra WWTPs for final disinfection and to transfer the combined reclaimed water flows from both WWTPs to the existing REMS distribution system. REMS Stage 1B involved major upgrades to Bomaderry and Nowra WWTPs to increase both the capacity and level of treatment at each site to achieve high quality reclaimed water suitable for either beneficial reuse or discharge to receiving waters.
The collected reclaimed water is transferred to participating irrigation areas via a transfer and distribution system and is the largest reclaimed water scheme operated by a council in Australia. REMS Stage 1A was developed by Shoalhaven Water over a number of years and significant infrastructure is in place to collect reclaimed water.
Shoalhaven Water’s “Reclaimed Water Management Scheme” (REMS) provides for the collection and storage of treated effluent (reclaimed water) and its application to agricultural land and sports grounds, with the majority of land lying on the floodplain between Nowra and the coast.
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