Construction World March 2016

PROJECT PROFILE

NOUPOORT WIND FARM progressing well

Murray & Roberts Infrastructure, a division of Murray & Roberts Construction, reports that the construction of the 35 wind turbine bases at the Noupoort Wind Farm as well as the ancillary civil works has been completed. his 35 wind turbine farm is located in the Umsobomvu District some 10 km east of Noupoort on the top of the mountain range of the same name. Once completed this wind farm, which will be operated by Mainstream, will feed 80 MW capacity back into the national grid via a 132 kV overhead power line. The contract is being undertaken by Murray & Roberts Infrastructure in a consor- tium with CONCO. Murray & Roberts Infra- structure’s scope of work includes all wind turbine generator foundations and adjoin- ing hard stands, 32 km of gravel access roads, the maintenance of a section of the existing N9 and the maintenance of 10 km of the Oorlogspoort District road. The company is also responsible for 33 km of cable trenching for the electrical cable reticu- lation which connects the wind turbines to the on-site substation. CONCO is responsible for the electrical component of the balance of plant works including the engineering, procurement and construction of the medium voltage collector system, substation and overhead line connection. The 2.3 MW wind turbines will be supplied and installed by Siemens Wind Power. The wind farm, which is spread over a 4 000 hectare area, will accommodate 35 wind turbine generators and is divided into four circuits namely A, B, C and D with eight turbines on circuit B and nine turbines on the remaining three. Stephan Venter, project manager for Murray & Roberts Infrastructure, says the

location has had extreme inclement weather including unseasonable rainfall as well as snowfall on the mountain top. This had an impact on the contract which started in February 2015 but Venter says that through sound management and attention to logistical and engineering best practice the company stayed on programme for this 16 month contract. Foundation construction Construction of the 35 wind turbine gener- ator foundations started in February 2015 with the foundations being excavated to suitable founding conditions, cleaned and then blinding placed. Blinding is 10 MPa to level the ground in the excavation. Once the blinding is cured sufficiently, the hold- ing-down bolts are installed to the specified levels, and this is followed by rebar installa- tion and foundation shuttering. Each turbine base has a diameter of 19 metres comprising 45,8 ton of reinforced steel and 369 m 3 of 30 MPa concrete. The plinth requires 23 m 3 of 60 MPa concrete and once cast, backfilling is done. A total of 1 600 t of reinforcing steel will be used. “The process was the same for all the foundations and these were completed in two stages; firstly the conical sections followed three days later by the plinth sections,” Venter explains. All elements were cast in-situ, utilising Murray & Roberts Infrastructure’s on-site concrete batch plant Trenching for cable ducts Each of the bases has 30 cable ducts going through it and this facilitates the connection of the turbine to the pad mount transformer (PT); from the PT it goes directly to the substation. This required 33 km of trenching for the cable reticulation and this was done using a Tesmec rock wheel machine and chain trencher. The trench width is between 350 mm and 1 metre wide depending on the reticulation connection. CONCO is responsible for the cable instal- lation placing another layer of bedding over the cables with Murray & Roberts Infrastruc- ture backfilling up to ground level. Following compaction, the top soil is replaced, the area fertilised and seeded with an indigenous grass mix. Hard stands Each wind turbine generator has a hard stand adjacent to its final position. The hard stand facilitates the erection of the wind turbines, each of which has a tower that is 100 metres high.

Erection of the bolt pack after blinding has been poured at Platform 24 at Noupoort Wind Farm.

Bolt pack erection after pouring blinding on one of the wind turbine bases at Noupoort Wind Farm.

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Steel reinforcement in progress on a base at Noupoort Wind Farm.

CONSTRUCTION WORLD MARCH 2016