Wind farm geology debate: Stuck between a rock and a hard place

The recent authorisation by the National Department of Environmental Affairs of the proposal to build a wind farm on the outskirts of Grahamstown has added fuel to a number of debates. One of these is whether or not the geology in the area is stable enough to support these enormous structures.
A geo-technical survey has yet to be done, before construction begins. meanwhile, the debate rages on.
The underlying geology in Grahamstown consists of quartzite, shale and clays of the Cape Supergroup. According to Dr Nick Stavrakis, who specialises in applied geology, the possible presence of clay in the underlying geology could lead to the wind turbines being unstable.
When clay is placed under pressure, especially directed pressure, “the clay liquefies... and starts to flow. There’s no support once it starts to liquefy and basically you have collapse. So wherever the stress is in that foundation, there’ll be movement,” he says.
Stavrakis is not opposed to green power; however, he believes that there are better locations for the eight proposed turbines than the Waainek Road, namely, the flat peneplain area near the substation. This area, according to Stavrakis, has a thick, hard silcrete crust and is fairly barren, making it unsuitable for agriculture.
He also says, “I believe it’s owned by the community. It’s the closest point to an Eskom substation, so you wouldn’t have power losses along the way.”
Palaeontologist, Dr Billy de Klerk, points out that clay deposits, covered by a layer of silcrete, occur mostly on the flat areas above Grahamstown. Underlying the high ground is the Witteberg group of rocks, which consists predominantly of quartzites.
“The high ground here is ideal... they [the Witteberg rocks] are as hard as hell and they’re on the high ground where you want your turbines to be in the first place. The higher your turbine, the more air flow it’s going to pick up,” says de Klerk.
“I think that Grahamstown has actually sited their turbines correctly on the high ground, and that minimises the amount of clay material below any turbine's position. The high ground is resilient, that’s why it’s high, so any of the softer weathered material has been washed away already.”
Stavrakis says, however, that the Witteberg quartzites are structurally disturbed by faults and therefore have weaknesses. He says that, in addition, interbedded with the quartzite are thick layers of soft clay-filled shale.
Even though hard rock would be more suited to the placement of wind turbines, de Klerk, who has done consulting for other wind farm proposals, believes this is not necessarily always the case.
“The foundations have to be 20 by 20 metres, and about five metres down. Then they sink cables into boreholes in various directions, which are then anchored in that concrete block,” he says.
Both Stavrakis and de Klerk point out that a comprehensive geo-technical survey of the area needs to be done before there is certainty about the suitability of the geology to support the turbines.
“It’s complex, because we don’t really know the underlying geology in great detail and apparently no geological or geo-technical study has been done,” says Stavrakis.
De Klerk says, “They haven’t completed their geo-technical survey, so they may not go and put them exactly at those points because of the considerations of what the substrate is going to be. Is it shale or is it quartzite? If it’s shale, they would think twice about the positioning. If it’s quartzite it’s competent and not a problem.”

 

A wide band of soft carbonaceous shale (the dark layer above Stavrakis' head in picture) interbedded in quartzites of Witteberg Group. This structurally-weak zone is on the approximate stratigraphic horizon as the proposed Waainek Wind Farm area and specifically the beds underlying the three turbines closest to the Umaria Umama Monastery. A layer such as this would be hugely problematic for the placement of a heavy wind turbine.
Photo by Kerry Holmes



Faulting with clearly-visible subsidence in Witteberg Group rocks in road cutting to the south of Grahamstown. The main fault traces are shown with broken white lines on the photograph. According to Stavrakis, such a position would constitute an unsuitable site for a large wind turbine.
Photo by Kodak Express

Well-known palaeontologist, Dr Billy de Klerk, feels the proposed location for the wind farm is probably suitable, as it is on resilient, high ground.
Photo by Mike Davies-Coleman

Published in Grocott's Mail on 15 April 2011.

Wind farm fans mixed response

Last week, a proposal by Franco-South African wind energy company, InnoWind, to build a local wind farm, was accepted by the National Department of Environmental Affairs. This decision has elicited a variety of responses from the Grahamstown community. Environmentalists are thrilled, but the locals living close to the chosen location are concerned that not all of the necessary studies have been carried out. Reporter, Gabi Falanga, found out about the good, the bad and the ugly surrounding the wind farm.

THE GOOD

The uninterrupted view of the Grahamstown Highlands from a bench at the Monastery. The three turbines which were not approved by the National Department of Environmental Affairs, would have been on this hill. These three turbines were not approved because of the visual and noise impact they would have had on the monastery.
Photo by Dianne Jordan

Dr Garth Cambray was instrumental in developing the wind farm proposal. Here he stands at a trigonometrical beacon, near the spot where one of the turbines will be built.
Photo by Leigh Raymond

No environmentally unfriendly emissions. One step further to being South Africa’s first green city. A community education trust. Countless academic opportunities. These are a few of the benefits that a wind farm will bring to Grahamstown.
The development of a wind farm will mean that Makana has an alternative source of energy available. The energy created by the turbines will be sold to Eskom and used by Grahamstown, while any excess will flow onto the electricity grid, where it can be used in other areas. Unfortunately however, this does not mean that electricity tariffs will be reduced. Electricity rates are regulated by the national regulator and locals will be billed as per usual by Eskom and the municipality. What it does mean, according to Dr Garth Cambray, who was instrumental in developing the wind farm proposal, is that it will significantly decrease the chance of load shedding for our town.
A project company will be formed to control the wind farm, in which InnoWind, will own the main share. Up to a quarter of the shares will be owned by the Makana Winds of Change Community Trust, however the exact figure is yet to be confirmed. Nikki Kohly, Rhodes University’s health, safety and environmental officer says the primary focus of the Trust will be education funding through scholarships and bursaries. Cambray is excited that some of the profits will contribute to Grahamstown’s local economy and education. “This means that when we turn a light on once the wind farm is going, we turn a light on at the end of the tunnel to a sustainable, dignified future for a young mind,” he says.
The wind farm’s proximity to Rhodes University will create new academic opportunities. Kohly says the wind farm may be one of the first commercial wind farms to operate in South
Africa and will “provide exciting research opportunities relating to wind farms, in areas such as environmental science, economics and social science”.
On top of this, the wind farm’s impact on the local ecosystem has been rated as medium to low impact and emission free. It is also a renewable form of energy and safer than alternatives, such as nuclear power.

THE BAD AND THE UGLY

Caroline, Liam (6), Russel and Nicholas (4) Field sit in front of the hill where five of the wind turbines are to be erected. The wind turbines will be less than a kilometre away from their house and they are concerned about the impact that noise and flicker will have on their children's health. The wind turbines will also be visually intrusive, potentially chasing away their foreign clients.
Photo by Dianne Jordan

“This is my dream home. We have a great lifestyle here and it’s possibly going to be ruined,” says Caroline Field. The Field family live on Coldsprings farm, where they breed buffalo and sable. Their house faces the hill where five of the wind turbines will be erected, should the project go ahead. These turbines, which will be placed on a neighbour’s farm, is just beyond their boundary fence and less than one kilometre from their house. Although the Fields aren’t against the implementation of green power, they are worried about the health, lifestyle and economic effects that the close proximity of the wind turbines will have on them.
“Our biggest concern is for our kids, because they say the infrasound isn’t very good for you. I don’t think they’ve researched the health aspects,” says Caroline Field as she watches Liam (6) and Nicholas (4) jumping on the trampoline. However, the Environmental Impact Report, compiled by Coastal and Environmental Services (CES) states that “the impact of low frequency noise and infra sound will be negligible” and that “there is no evidence to suggest that adverse health effects will occur as the sound power levels generated in the low frequency range are not high enough to cause physiological effects”.

Russell Field isn’t convinced that the project will be a success once it is operational. He is concerned that the project will not be able to meet its financial obligations and that Eskom does not yet know how to integrate the wind power into the main electricity grid. “I think it’s going to become scrap metal on the skyline,” he says.
The Field’s main source of income is from foreign clients who visit their lodge. “They will never come here with these things,” says Caroline Field about the visual impact that the turbines will have on their farm.
The Fields will be appealing the decision. One of the grounds of their appeal will be that a geo-technical analysis of the area has not yet been done. Local geologist, Dr Nick Stavrakis, explains that the underlying geology in the proposed location is not stable enough to support the immense weight of the turbines. Principal environmental consultant at CES, Marc Hardy, says that detailed geotechnical surveys will be conducted before construction begins to ensure that the underlying geology is suitable to support the turbines.


Dr Nick Stavrakis specialises in applied geology. He feels that not enough is known about the underlying geology at the location chosen for the wind farm. Stavrakis says the ground in this area consists mainly of clay (shown in yellow on the map) and is not stable, especially when under direct pressure. Stavrakis feels the Grahamstown Peneplain area (shown in brown and white on the map) near the substation would be a better location, because that ground consists of a very thick, strong layer of silcrete rock.
Photo by Gabi Falanga

Wind power blows in

The proposal to develop a wind farm on the outskirts of Grahamstown was authorised by the National Department of Environmental Affairs this week.
The wind farm will consist of eight turbines on the Waainek road. Four alternative proposals were submitted to the department, requesting that 11 wind turbines be erected, but only eight were approved because of the potential visual and noise impact on the nearby Mariya uMama Wethemba Monastery.
The news was greeted enthusiastically by local environmentalists. Nikki Kohly, Rhodes University’s Safety, Health and Environmental officer was very optimistic when she heard the news: “I’m really pleased because I think it is crucial that we start looking at sustainable energy options.”
Nicole Viljoen, from the student organisation South East African Climate Consortium Student Forum, said they supported innovations which were environmentally and socially beneficial.
"A wind farm, if efficiently managed, is just such an innovation, and as such we greet it with nothing but support and excitement for what it may hold for the future health of the Grahamstown area’s environmental and social circumstances.”
Despite the excitement surrounding the project, protest is expected. Coastal and Environmental Services did the environmental impact assessments for InnoWind. Principal Environmental Consultant, Marc Hardy, suspects that the main appeals will concern the visual impact that the turbines will have and consequently the effect that this will have on tourism and property value.
Perceived noise impact would probably also be cause for appeal, although Hardy said that based on their studies, he was confident noise would not have an impact on existing settlements.
Hardy will notify registered interested and affected parties of the appeal process.
Wind farms provide a sustainable alternative to electricity and are regarded as "clean" energy because they do not produce any emissions and do not rely on depletable fuels.
The energy generated by the turbines will displace the power usually used off the Eskom grid, allowing other people to make use of the electricity from the grid instead.
Because only eight turbines were approved, they will not be able to generate enough energy to completely meet Grahamstown’s peak winter requirements of about 35 Megawatts. The turbines will generate around 24 Megawatts of energy.
Dr Garth Cambray, managing director of Makana Meadery, was instrumental in forming the original plan to build a wind farm. He is thrilled that part of his vision for renewable energy for Grahamstown will finally be realised.
“It’s an exciting step for the town, because it’ll make us one of the first green cities,” he says.
Construction of the turbines, which will stand at 140 metres from base to the blade tips, will start only once applicant, InnoWind, has secured a generating license and a power purchase agreement from the national regulator.
Kevin Minkoff, project manager of InnoWind, is confident that construction will start next year and that the full wind farm should be finished and operational by the end of 2012.
Part of the profits derived from the wind farm will be ploughed back into the community in the form of an education trust.

Published on front page of Grocott's Mail on 18 March 2011.