Loeriesfontein Wind Farm and Khobab Wind Farm, in the Hantam Municipality of the Northern Cape, are two pioneering renewable energy projects in which Concor Infrastructure played an important and innovative role. The wind farms were constructed by Concor Infrastructure in a consortium with CONCO.
Concor Infrastructure was responsible for the construction of all 122 wind turbine generator foundations, as well as the adjoining hard stands and all internal roads on both sites.
The company brought its extensive experience and expertise in civil engineering, concrete design and sustainable project management to these construction projects in a remote endemically sensitive and arid location.
In planning and implementing its work, Concor Infrastructure was able to ensure a high quality product and service – with innovative cement-saving concrete mixes for the wind turbine bases – as well as water saving strategies and environmental care, all delivered well ahead of schedule.
The environmental impact of the project was carefully considered and addressed through a number of integrated strategies. These included the conservation and recycling of scarce water resources, the bioremediation of hydrocarbons on site, relocation of protected plant species and an overall reduction in the project’s carbon footprint.
Concor Infrastructure was also able to promote local employment and skills development in the area by sourcing much of its labour from the town of Loeriesfontein. In addition to the training provided, Concor Infrastructure mentored local small businesses to become effective suppliers and subcontractors.
The company’s ongoing commitment to Zero Harm through strong health and safety practices allowed the projects to reach the 1,3 million LTIF (Lost Time Incident Free) milestone in January 2017. As at August 2017, the project was standing on 2 million LTIF for the Consortium.
Loeriesfontein Wind Farm and Khobab Wind Farm are both part of the South African Government’s Round 3 Renewable Energy Independent Power Producer Procurement Programme (REIPPP). South Africa Mainstream Renewable Power has managed the construction and will manage operations of these wind farms, following commercial operations.
Innovation
Substantial innovation in concrete mixes was applied at the Loeriesfontein and Khobab sites, contributing to various environmental considerations while enhancing performance.
The plinths at Loeriesfontein were constructed using high strength 60 MPa concrete with a design mix comprising 75% ground granulated corex slag (GGCS) in place of cement. As much as 95% waste replacement was used in the 12 200 cubic metres of 15 MPa concrete used for the blinding beneath the bases. Concor Infrastructure used 50% waste material for both the 60 MPa plinth concrete as well as the 30 MPa conical base concrete. Strengths were achieved at 28 days.
Together, these initiatives reduced the wind farm’s construction carbon footprint from approximately 300 kg of CO2 per cubic metre to 90,7 kg of CO2 per cubic metre, reducing the project’s estimated overall carbon footprint by 31%.
Performance of concrete is vital for this demanding application. Each of the 122 wind turbine bases is 19 metres in diameter, and was constructed in the same manner to accommodate a 99 metre high turbine tower on which is placed a nacelle weighing in excess of 80 tonnes.
The efficient, continuous work process allowed the construction of one foundation base – from excavation to completion – to take just 10 days.
Corporate social environment
Much of the workforce on both wind farm contracts was employed from the Loeriesfontein community 60 km to the south of the site, in support of local employment and upliftment. This is in line with Concor Infrastructure’s skills development strategy, as these workers needed specialised induction and training – and will also facilitate the sustainable development of the community.
In addition to providing direct employment and skills development, Concor Infrastructure mentored several Enterprise Development initiatives, setting these up carefully to ensure their future sustainability even after the project construction had been completed.
Transportation from Loeriesfontein to the project site could have posed a challenge and forward thinking from Concor Infrastructure saw the company assist a local resident of the town to start up his own transport business. In addition to purchasing a brand new Quantum mini bus to get the business started, the company also provided ongoing mentorship and training in the necessary skills that would be required to ensure a sustainable business model going forwards.
Other enterprise development initiatives included a waste recycling operation, a woman-owned security company and a car wash facility in the town.
Concor Infrastructure also ensured that existing local businesses were empowered and
provided mentorship to these business owners as well. The company invested significant amounts of money and time in upgrading various community facilities including the local school and sports facilities. Significantly, even though the project has largely been completed, the investment in the local community is ongoing to ensure long term sustainability.
Innovative design
To reduce the project’s carbon footprint, carefully selected and treated waste material was used as a replacement for cement in low cement geo-polymer readymix concrete. The bases at the Loeriesfontein site contained a design mix comprising 50% ground granulated corex slag (GGCS). For the blinding beneath the bases, as much as 95% waste replacement was used in the concrete. 50% waste material was used for both the 60 MPA plinth concrete and the 30 MPa conical base concrete with strengths being achieved at 28 days.
These design innovations had a profound impact on the project’s carbon footprint. While the carbon footprint of a standard 30 MPa concrete equates of approximately 300 kg to 350 kg per cubic metre, the reduced use of cement by these special mixes has helped dramatically reduce the wind farm’s carbon footprint to 90,7 kg of carbon dioxide per cubic metre.
In addition to the innovative concrete mix designs, the project embarked upon the construction of a specialised wash bay solution at the on-site batch plant. This incorporated a specially constructed bunded slab which allowed for both water and concrete recycling.
The wash bay comprised a series of settlement ponds, each having an overflow reporting to the next pond once it reached a certain level. Concrete sludge settling in the pond was removed manually and left on a specially constructed bunded slab to dry. Dried material was removed to the quarry site where it was crushed and blended with aggregate for reuse in the turbine bases.
Consideration for the environment
A range of environmental issues was considered and addressed including protecting and translocating threatened and endangered plant species, using water in a drought stressed arid environment, reclaiming contaminated soil through bioremediation and limiting the project’s carbon footprint.
The plant recovery programme commenced early in the project with identification and safe removal of several unique protected plants such as Hoodia Gordonni (commonly known as Xhowa) which has been part of some of the local community’s diet for many centuries. Another protected species was the Skilpadtoontjie (Aloinopsis Luckhoffi), which is endemic to the area. Main plant populations not in the direction construction footprint were map tagged and made no go areas.
The main strategy to conserve water was to reuse as much as possible, reducing the need to source additional water supply. Concor Infrastructure installed a modular water treatment plant on site, with a screening system to remove the heaviest solids and bacteriological rollers treated the remainder. No chemicals were used in this process.
This allowed grey and black water to be treated on site and used for construction purposes. Most of the recycled water was used on the earthwork layers for the wind turbine bases. On average, the treatment plant cleaned 30 000 litres per day and the treated water was stored in two reservoirs for reuse.
Dust suppression was critical to prevent a safety hazard, however the control system could not be water intensive due to the arid geography and the drought conditions. The deployment of the environmentally friendly E-Cat dust suppression system on this main 60 km long access road provided the necessary intervention, further reducing the project’s initial water footprint plan.
A specially constructed bioremediation facility was used on site to break down hydrocarbons to water and gas, eliminating the hazards associated with contaminated soil. This went well beyond the requirements of the Environmental Management Programme.
Health & Safety
Extremely careful planning and a focus on ongoing skills development and training, both in safety and competency, allowed the contractor to not only adhere to its construction programme, but also to ensure optimum safety on site.
The project reached the milestone of one million Lost Time Incident Free (LTIF) hours in September 2016, and 1,3 million LTIF hours in January 2017. These accolades underpinned the level of commitment to safe work. Careful construction work planning, as well as control of materials and subcontractors, also played an important role. Significantly, the LTIF as at August 2017 stands at 2 million LTIF for the Consortium.
Quality and cost
The quality of the project’s core product – concrete – was proven and maintained throughout. In addition to the research and development invested in innovative (see section on Construction Innovation Technology) and environmentally friendly (see section on Environment) concrete mixes, Concor Infrastructure’s testing is up to three to four times more thorough than conventional concrete inspections. They also exceed those undertaken on concrete performance on wind construction projects, and involve studying the micro-crystal formations of the concrete using Environmental Scanning Electronic Microscopes (ESEM).
ESEM provides a clear understanding of the crystal formations between the geo-polymer and hydration technology used in the mixes. This is essential considering that these elements need to interweave correctly to ensure durability and strength of the concrete.
As with all projects, time was of the essence and the construction of each foundation base – conducted on a continuous basis – took just 10 days from excavation to completion.
When the foundations were all completed in December 2016, it was two months ahead of schedule.
In terms of cost effectiveness, Concor Infrastructure’s work over the years also proves that the use geo-polymers –instead of commercially sourced activators – can be cost effective.
How risk was managed
Consistent workability and high performance of large volumes of concrete was required to avoid the risk of any delays or operational complications. Concor Infrastructure’s expertise in the complex inter-reactions that take place in geo-polymer concrete allowed a repetitive production rate, consistent workability of construction materials, and minimum standard deviation strength of the concrete.
Critical testing of the performance of the wind farms’ concrete bases – which are under high fatigue – also enhanced risk management. Over-and-above the standard strength tests undertaken at 28 days, cube tests were done at 56 and 90 days to provide a longer term understanding of the strength and durability characteristics of the concrete.
Concor Infrastructure’s concrete mixes achieve natural chemical inter-reactions, and have found synergies at ambient temperatures and much lower, such as those at Loeriesfontein Wind Farm and Khobab Wind Farm.
Concor Infrastructure, previously known as Murray & Roberts Infrastructure, is part of Concor Construction which was recently acquired by a consortium led by Southern Palace Group.
