Council highlights windfarm concerns

The developers of a proposed six-turbine windfarm near Kilmaley have confirmed that 26,704m3 of soil will be extracted to facilitate the development.
Clare County Council requested Seahound Wind Energy Developments Limited to address a number of concerns and issues concerning the construction of six wind turbines with a maximum hub height of 90m, maximum blade diameter of 93m, one permanent meteorological mast, access road and internal side tracks, electricity sub-station, underground cabling and all associated site works.
In its further information request the council expressed concern about conflicting statements concerning the total volume of excavated material and noted this is as high as 46,350m3 in Section 10.311 of the Environmental Impact Statement (EIS) and 26,704m3 in another section.
The planning authority noted some slight discrepancies between the stated peat depths and slopes having regard to the peat probe tests, gouge core tests and trial pits.
It expressed concerns about the potential of land slippage around the location of turbine six and in ­particular the possibility of land slippage during construction.
It also had some concerns about the potential for accidents associated with peat-filled borrow pits, where construction staff and or members of the visiting public could be at risk of ­falling into the filled borrow pits, where the stored peat ­material may not be condense.
According to planning documents submitted by Renewable Power Generation, Rathcoole, County Dublin on behalf of Seahound, the total volume of excavated material for the proposed development is 26,704m3, which is predominantly made up of peat and described the conflicting amounts as a “clerical error”.
Renewable Power Generation noted mineral soil is expected to provide a suitable bearing stratum for both roads and hardstandings and as such, would not be excavated.
Commenting on any apparent slight discrepancies in peat depths, the consultants noted it is important to take note of the variable nature of peat and the underlying strata.
Acknowledging another “clerical error”, it stated the description of the soil near turbine five should state it is located in mature forestry at low slope in a moderate peat depth of 1.9m.
The consultants pointed out there are no recorded failures in blanket bog slopes at less than three degrees.
“However, from a buildability perspective, construction presents several issues. Access to the area would require a floated road but in general turbine manufacturers require that hard standings are excavated to bearing strata.
“Transitioning from floating to excavated areas is problematic from differential settlement and drainage point of view. This area presents negligible peat stability risk but the construction issue needs to be foreseen and planned appropriately for.
“The combination of conservative risk parameters results in its identification of turbine four is a medium risk area but when one looks at its context on the ground, particularly with the presence of the existing road providing stability and minimising the construction required, it can clearly be illustrated that risk can be entirely mitigated by design,” they stated.
In its further information request, the council also expressed concern about the cumultive impact of this windfarm and others ­neighbouring ones in West Clare on the hen harrier population and on the bat population.
The consultants ­acknowledged 10 windfarms scattered over a very large area 15km from east to west and 12km from north to south of the site would provide a combined total of 92 turbines.
This compares to 71 turbines at Derrybrien in the Slieve Aughty Mountains, where the consultants claimed “no adverse impacts have been detected from a monitoring programme between 2004 and 2009 on the 10 to 11 pairs of hen harriers nesting within 5km of the site.
“There is no direct evidence from Ireland or the United Kingdom that windfarms have caused detrimental effects on any hen harrier population.
“On the basis of 86 turbines from nine other developments scattered within an estimated 160km2 of potential hen harrier habitat, it is considered that the six additional turbines in the proposed Letteragh development would not add significantly to any possible cumulative impact on the local hen harrier population,” they stated.
They noted the existing bat survey should be taken as a pre-construction survey as it identified the species and their activity within the development area.
They added a post-construction monitoring study would be beneficial to ascertain any bat mortality during the operation phase.
This monitoring should include detector surveys of bat activity near turbines, combined with a suitably ­designed corpse search ­regime at all turbine locations.