Australian Water Management Review Vol 2 2013 | Page 54

AustrAliA’s first use of horiZontAl DireCtionAl Drilling (hDD)
InteRsect technoloGy on thRee 2125m WateR & seWeRaGe hdPe maRIne cRossInGs

In Mid 2011, Coe Drilling was awarded the Gladstone Harbour HDD Crossing contract on the Curtis Island Water and Trade Waste Infrastructure Project.
The project scope of works involves the Design, Development, Procurement and Construction of the following pipelines beneath the entrance to Gladstone Harbour and the Narrows: 1. DN 250 HDPE 100 PN 25 Water Pipeline 2125m in length. 2. DN 250 HDPE 100 PN 25 Sewerage Pipeline 2125m in length. 3. DN 500 HDPE 100 PN 25 Water Pipeline2125m in length. The construction of potable water pipelines and sewer pressure main between the Gladstone mainland and Curtis Island is to facilitate the provision of utility services to meet demand growth associated with LNG facilities in the area. The project heralds a number of innovative technical milestones for Trenchless Technology in Australia, with Coe Drilling delivering the first use of HDD Intersect Technology in Australia on all three harbour crossings. It also encompassed the first use of Gyroscopic Steering Tools on hard rock crossings involving HDD Intersects and also the deepest recorded HDPE marine crossings installed at depth of over 75m. The Location—Environmental Considerations, approvals & alternatives. The project is located within the Great Barrier Reef World Heritage Area (GBRWHA) and adjacent to the Great Barrier Reef Marine Park (GBRMP). As the world’s most extensive coral reef ecosystem, the Great Barrier Reef is unique and was declared a World Heritage Area in 1981. Early environmental impact statements published for the LNG project construction and operations proposed that the provision of water and sewage services for the Curtis Island facilities should occur via individual reverse osmosis (desalination) and sewerage treatments plants located at each LNG site. The Queensland Coordinator-General’s evaluation of the environmental impact statements (condition 21) however, stated that all parties should undertake an: “Assessment of the feasibility of co-locating water and sewage services in consultation with the Gladstone Area Water Board and Gladstone Regional Council”. As a result of this condition, a concept study to provide a feasible alternative to individual reverse osmosis (desalination) and sewerage treatment plants at each site was developed. A number of alternatives were proposed in the concept study, which included open trenching and bundling the water and sewer pipelines with the gas pipelines across the Narrows. The preferred option
48 | AustrAliAn water man age m e nt re v ie w

outlined in the Referral of Proposed action document was a HDD Crossing because HDD would avoid direct impacts to the GBRMP. Additional Risks Coe Drilling recognised that it was not only HDD technology that had to be used but also innovation with tools and new techniques to avoid indirect impacts including: • Sedimentation, run-off and dust - potential for sediment deposition to influence suitability of marine habitat for existing benthic a ????????????????????????A???????????????????????????????????????????????????????$?!????????????????L???????????????????????????????????????????????????????????????????????????????????$???????????????????????????????????????????????!????????????????????????????????????????????????????????????????? ????????????????????????????????????]?????????????????????????????????????????????????????????????????????????????????? I!5@??????????????????
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