Mighty River Power’s new geothermal power station at Kawerau is the largest geothermal project undertaken in New Zealand for 20 years. It is also the first of a possible seven major geothermal projects planned by generation companies Mighty River Power (MRP) and Contact Energy over the next five years.
In July 2006, MRP signed an Engineering, Procurement and Construct (EPC) contract with the Sumitomo Corporation of Japan to construct the plant. The EPC made Sumitomo responsible for the works inside the boundary fence. Sumitomo in turn subcontracted the majority of the design, supply and installation of the generating equipment to the Japanese company Fuji Electric Systems.
Jensen Steel Fabricators fast-track erection
In November 2006, Sumitomo awarded a subcontract for the Design and Construct of the Civil, Structural, Architectural and Building Services elements of the project to Hawkins Construction. In addition to the subcontract, a ‘Project Agreement’ was signed by Sumitomo, Fuji and Hawkins, which governed the working relationship between the three parties. The Project Agreement also reflected the need for close collaboration in order to ensure that the plant was safely completed ahead of schedule and to the required quality standard. Indeed, all three companies were to be tested by the tight time constraints.
Hawkins engaged Beca as Principal Consultants for the design and supervision of the civil, architectural and structural work. Beca engaged Jensen Steel Fabricators Ltd, based on its reputation and track record with the ep3 project at Huntly power station, to fabricate and erect the steel frames of the main buildings at Kawerau. These included the main power plant and crane rails, the workshop and main cable and pipe racks, and parts of the gas extraction system, about 700 tonnes of structural steel in total.
The Project Director for Hawkins Construction was Bernard Hill. “It was a layered process in which the design was progressive. The layout of the plant was determined by Fuji; the challenge was to put structures around the fundamental processes of geothermal power generation. These include steam separation, gas extraction, cooling and re-injection. What was really impressive was the intensity and speed of interaction between the structural engineers, Beca, who produced the engineering drawings, and the constructor, Jensen Steel Fabricators Ltd, who produced the shop drawings and got the steelwork into production. They built an open communications channel that just seemed to accelerate as the project advanced.”
Putting structures around the process of a geothermal power station
Beca’s Senior Structural Engineer on the project was Peter F Davies. “We used the software package Revit to produce 3D models of the various structures. This helped all who were involved to understand the often complex structures of the buildings.” Peter frequently called the drawing office at Jensen Steel to alert Drafting Manager Zane Bowler to changes that were coming up. “This was very helpful,” says Zane, “because it saved frustration and time. Peter would tell us to hold fire in one area and go full steam ahead in another, enabling us to maintain high productivity with little or no corrections. There was none of the awkwardness you sometimes get when documentation is only partially complete. This was complete professional trust.”
Beca’s Project Leader at Kawerau, Hamish Brooker, comments on the turbine hall: “This was a K-braced lateral load system up to the turbine floor, above which we designed braced portal frames. The floor system was composite steel decking. Doing it in steel made for very fast construction. In fact, Fuji said it was the fastest the company had ever seen such a structure being built. Being a very aggressive environment meant that the steelwork required substantial protective coating; at 325 dft microns (dry film thickness), it was heavy.”
Piping hot
The target finishing date was the start of October. Mighty River Power announced that the principal construction contractor, Sumitomo, officially handed over the Kawerau Geothermal Power Station to the state-owned enterprise’s operations team on 2 September 2008. Not only was this a full month ahead of the deadline, but also the station’s generating capacity, which had been expected to be 90MW, was actually 100MW. The $300-million station’s output will meet about a third of eastern Bay of Plenty’s residential and industrial power demand.
“This level of overachievement is the result of great teamwork,” says Greg Jensen, managing director of Jensen Steel Fabricators Ltd. “And the same team is already at work on Mighty River Power’s next geothermal development, a $450-million 132 MW station at Rotokawa.”
