Nacap constructed a DN200 (8 in.) diameter API-5L Grade X70 slurry pipeline, with wall thickness varying between 4.8 mm and 8.2 mm and a DN400 (16 in.) diameter API-5L Grade X42 return water pipeline, with wall thickness varying between 6.4 mm and 9.53 mm, each 62 km in length. The pipelines were constructed side by side in a single 1,100 mm wide trench. Also within the same trench was one optic fibre cable running the full length of the pipeline (62 km) and a second optic fibre running for 48.5 km. The optic fibre cables were laid during backfill operations above the smaller slurry pipeline, while large quantities of zinc earthing ribbon were installed on the bottom of the trench. In addition, two pipeline crossovers were fabricated, hydrostatically tested, painted and installed at the two highest points on the pipeline route.
The project was executed with a single source negotiated, partnering commercial structure, which enabled the OneSteel, Thiess and Nacap teams to work in a climate of co-operation. This ensured that the project objectives were mutually agreed at commencement and more importantly, delivered during implementation.
OneSteel was able to provide a total line pipe solution to the project, which included transport logistics as well as the coated line pipe supply. On an aggressive pipe delivery schedule, OneSteel from their Kembla Grange pipe mill supplied approximately 6,000 tonnes of line pipe in perfect condition and on time to the Whyalla railhead. Line pipe was then hauled a short distance to the pipeline RoW by Nacap.
Construction was undertaken by one mainline crew constructing the first 55 km and a further specialist “˜poorboy’ crew constructing the final 7 km section, which ran parallel to the Whyalla to Iron Knob railway line on the approach to the Township of Whyalla. Typically, each pipeline was completed by one crew working on both pipelines, however the welding crew was establish and manned accordingly to operate as two crews.
The production rates of each mainline crew was well balanced to ensure that the crews worked efficiently, that minimum productivity rates were achieved consistently, and that one crew did not catch up to another.
The “˜poorboy’ crew consisted of personnel that were highly skilled in various areas of pipeline construction. The crew was entirely self sufficient (except for the installation of the fibre optic cable) and faced many challenges, including a restricted RoW due to the presence of the railway line and low voltage power lines. The “˜poorboy’ crew overcame the many issues associated with city works, including unknown and congested foreign services, dust suppression, noise control, limited working hours and working within the heavily regulated OneSteel property.
Within the 62 km long RoW, there were seven bores, which consisted of four road/highway crossings, two rail crossings and one combined road and rail crossing. At one bore location, the main optic fibre (IP-1) linking Melbourne to Perth was crossed twice. Substantial effort was made up front to liaise with the asset owner and ensure that adequate protection was implemented during all phases of work in the area.
Nacap subcontracted the installation of the two optic fibre cables to specialist subcontractor NDC Limited, a wholly owned Telstra subsidiary. NDC’s crew worked closely with Nacap’s padding and backfill crew to ensure adherence to the cable installation specification (i.e. adequate separation and depth of cover, and paying special attention that no small rocks were included in the backfill, potentially compromising the fibre optic cables). NDC also performed the 15 cable joints required to complete the two cables. Subsequent integrity testing revealed that successful installation was achieved, with no damage or noise in the line.
Project traceability was driven and managed with Nacap’s Construction Management System (CMS), utilising palm pilots that had been re-programmed specifically to separately cater for the construction of and separately identify the dual pipelines. Data was collected and processed on a daily basis, allowing real-time statistical analysis and trouble shooting. All welds were subject to 100 per cent x-ray examination and the resultant repair rate was less than 2 per cent overall.
Project quality control was completed by a team of in-house inspectors, trained on all facets of pipeline construction operations, from pipe load out, through to rehabilitation. In addition, the works were subject to regular formal quality audits by the Client.
Nacap combined the as-built survey data collection with CMS. Two as-built survey crews collected the relevant field data through an Omni-star system mated with the CMS palm pilots. As-built data was then transferred into a staging program and uploaded into a graphical format, for review by the CMS Administrator and the Client.
Special attention was required in terms of safety, the environment and the need to minimise disruption to all landholders/stakeholders during completion of the project works. The outcomes of this were:
* Over 100,000 man hours were completed on the project without any MTI or LTI incidents.
* Several centreline re-alignments were required around the sensitive Western Myall Trees (Whyalla is one of the most southern locations these trees grow; the trees also have cultural significance), all of which were accomplished successfully.
* No landowner/stakeholder complaints were received during the project and several successful meetings were held to both educate and communicate with the local community regarding the pipeline construction process.
In addition, project personnel successfully managed working in areas of restricted RoW (the RoW was restricted to 18-20 metres wide over a distance of 18 km, coupled with the dual pipelines and optic fibres, this was a substantial restriction), construction parallel to high voltage power lines for a length of 25 km and employed effective construction methodologies when working beside the operational railway line (16 km).
Overall, Project Magnet was completed under budget and one and half months ahead of the contract schedule, but most importantly without any MTIs or LTIs, proving a success for all parties concerned.