‘Peat slides’ risk warning for €1m windfarm

THE cumulative impact of constructing a proposed €100 million windfarm in West Clare has the potential to enhance local flooding and peat slides under extreme rainfall, Galway-based hydrologists have claimed.
Hydro-G, Henry Street, Galway made the claim as part of its wide-ranging Peat Hydrology Assessment of the          proposed windfarm at Shragh, prepared on behalf of two local objectors, George and Ann Whelan in response to further information provided by the developers.
Clare Coastal Wind Power Limited has submitted a planning application to An Bord Pleanála to develop a 45-turbine windfarm with a hub height of 85m and a rotor diameter of 82m at Carrowmore South, Einagh, Monmore North, Doonbeg, Shragh, Mountrivers and Drumillihy.
The company’s consultants stated the development presents no or a low risk for impact on local hydrology.
According to company’s consultant engineers, one of the priorities in the windfarm design has been the mitigation against potential impacts to the environment and to minimise the quantity of peat to be excavated during the construction phase of the project.
A process of “mitigation by avoidance” was undertaken by the EIA team during the design of the windfarm, turbine positioning and associated infrastructure layout. Arising from the results of this study, areas where peat had not yet been extracted were recognised to be less suitable for development.
“The proposed Shragh windfarm turbine layout was designed in such a way to have minimal impacts on raised bog and according to the recommendations specified by the ecologist for the site.
“Ecological feedback has been incorporated into the windfarm design and has helped in the identification of suitable ground, minimising crossings of watercourses and avoiding wet and deep peat.
“Flow will be maintained in all existing drains. Peat excavation will be avoided where possible. All peat excavated will be reinstated in the peat reinstatement areas identified,” the company engineers stated.
In addition, planning guidelines for local authorities ‘Best Practice for Wind Energy Development in Peatlands’ published by the Department of Environment have been adhered to in the design of the development, according to the company engineers.
In its summary of mitigation measures, Jennings O’Donovan and Partners Limited Consulting Engineers, on behalf of the company, stated excavation of peat in areas of over 1m in peat depth zone should follow appropriate engineering controls.
This includes the drainage of the peat along the proposed access road in advance of excavation activity one month in advance where possible so as to reduce pore water content and instability of the peat substrate before excavation. These drains should be positioned at an oblique angle to slope contours to protect ground stability.
The engineers stated a geotechnical engineer/engineering geologist will approve the methodology of construction and supervise all excavations during the construction phase of the project. This would involve direct monitoring and management of operations, preventing unauthorised excavations and stopping approved excavations on first signs of ground stressing or release of uncontrolled water and suspended solids load.
A spokesman for Clare Coastal Wind Power said the company have no comment to make other than to reiterate that it awaits the decision of An Bord Pleanála.
Hydro-G claimed in its submission the total cumulative volume of peat that has to be removed as part of the construction process will present such a substantial change in catchment hydrology that the potential “to create peat failure zones and enhance local flooding is not defensible”.
“The EIS persistently refers to volume of material to be removed for construction of each turbine and the EIS presents water balances for hard standing run-off associated with storm events during the operation of the turbines.
“However, no information has been presented by the applicant to support the viability of the proposal in which the integrated effect of the removal of peat for all turbines, and the associated crane pads, siltation ponds, access roads, cabling trenches are evaluated in an integrated way.
“This information is missing from the EIS, NIS and the information submitted in response to the board’s request for further information,” the submission claimed.
“The effects of the removal of the volume of peat will create potential for peat failure during the construction phase, high potential for peat slides under extreme rainfall events in the operational phase and will increase extents of flooding in this floodplain with coastal connectivity.
“The data presented are too small because the cumulative effect is not presented. The cumulative effect results rule out viability of the 45-turbine proposal.
“The data presented for water-quality discharge concentration and site water management techniques, in the revised drainage proposal in the FI response, are also of an order of magnitude incorrect for the receiving water environments and don’t concur with the presented water quality data. The works proposals can’t be mitigated against to the degree, which the receiving environment requires,” the submission claimed.
The consultants point out the low-lying flat landscape setting of this flooded peat land presents as great a threat of peat failure as sloped sites.
They claim the fact the company’s consultants refer to previous reports on peat failure in the context of slope of the site “is just one of the shortfalls of the soils and hydrology assessment”.
The proposed development also presents potential to draw in saline water from three designated coastal sites in proximity, which Hydro-G claims should take into account the risk of saline intrusion to the Tullaher Lough and Bog SAC complex that is between the proposed windfarm site and the coastal zones.