Nant Mithil
Official Objection Deadline: Mid Feb 2026
Nant Mithil Energy Park (CAS-01907-D7Q6Z1) is a major proposed onshore wind development within Radnor Forest, covering around 1,773 ha of upland landscape. The scheme comprises 30 industrial-scale wind turbines up to 220 m to blade tip, alongside extensive enabling works including turbine foundations, crane pads, over 23 km of new and upgraded access tracks, borrow pits, a construction compound, a substation platform, underground cabling, and other associated infrastructure. If built, it would convert a large area of tranquil upland into an engineered industrial site, with permanent changes to landform, habitats, views, and night-time conditions.
Radnor Forest is valued for its open horizons, dark skies, and wide-ranging views. The turbines are proposed on prominent ridgelines and summits including Great Rhos, Shepherd’s Tump, Graig Hill, Fron Goch, Crinfynydd, and Oldhall Bank. The project documents accept that many viewpoints would suffer significant and irreversible visual harm, including popular recreational routes such as Glyndwr’s Way, the Radnor Ring, the Heart of Wales Line Trail, Caergynan Bank open access land, and a range of upland footpaths and bridleways. For residents in surrounding communities, the change is not limited to occasional glimpses. The proposal would introduce large, moving structures into daily skylines, altering the character of the landscape on a regional scale.
Night-time impacts are also a key concern. The scheme includes aviation lighting requirements, with 14 turbines needing visible aviation lights and all 30 requiring infrared lighting. In an area where darkness and tranquillity are part of its appeal for residents and visitors, introducing repeated points of aviation lighting risks degrading the night-time environment and changing how the landscape is experienced after dusk.
The development site is hydrologically sensitive. It lies at the headwaters of the River Ithon, and all disturbed runoff and sediment pathways ultimately connect downstream into the River Wye Special Area of Conservation (SAC). The area also sits beside the Radnor Forest Site of Special Scientific Interest and the Mynydd Ffoesidoes Reserve managed by the Radnorshire Wildlife Trust. These designations reflect the ecological importance of the habitat network present, including upland heath, modified bog, riparian woodland, fragments of ancient woodland, semi-natural broadleaved woodland, and the wider corridors that protected species depend upon.
The project documentation identifies a diverse range of wildlife receptors, including 11 bat species, and mammals such as otters, badgers, pine martens, polecats, hedgehogs, and brown hares. Construction impacts from forestry removal, track building, excavation, and turbine placement on ridgelines can fragment habitats and disrupt commuting routes and foraging areas, while turbines introduce collision risk within rotor-swept airspace. Watercourses such as Mithil Brook and Black Brook form part of the River Ithon system, supporting aquatic habitats and species including Atlantic salmon, bullhead, brown trout, and white-clawed crayfish. In upland terrain, heavy groundworks and engineered tracks increase the likelihood of erosion and sediment mobilisation, with consequences that can propagate downstream.
A distinctive issue raised in objections is the omission of any radiological assessment for caesium-137 (Cs-137) in soils and peat. Upland Wales received known Chernobyl deposition, and Cs-137 can remain associated with organic-rich soils and peat. Large scale excavation, drainage alteration, and vegetation removal can disturb these materials and mobilise fine particles and organic matter into water pathways. Where a site drains to a European protected river system, the absence of baseline sampling and pathway assessment is seen as a serious gap, because it leaves a potential pollutant pathway unquantified.
There are also concerns about the completeness of the Environmental Statement across several other topics. Hydrology and peat assessments are described as unfinished despite the direct catchment connection to the River Wye SAC. The noise assessment is criticised for relying on approaches that do not properly address low-frequency noise, infrasound, amplitude modulation, and indoor effects that are commonly raised for turbines of this height. The carbon assessment is challenged as being based on an outdated and non-compliant calculator and for underrepresenting the impacts of peat-influenced soils, forestry removal, altered hydrology, and the scale of construction materials, including large volumes of concrete.
Transport and access impacts are another practical reason communities object. Construction would require heavy goods vehicles and abnormal loads, including very long turbine components, to move through rural road networks and villages. The documentation acknowledges major and moderate adverse effects on key corridors, but the objection material highlights that essential engineering detail is missing, including swept-path analysis and the level of junction alteration needed to make routes workable and safe. These questions matter because the impacts are not theoretical. They affect road safety, daily travel, community severance, and the ability of emergency services and local traffic to function reliably during construction.
A further critical point is that the scheme’s required 132 kV grid connection is not included within the Environmental Statement assessment described in the objection material. For a development of this scale, grid connection infrastructure is not optional. Excluding it from assessment prevents decision-makers and the public from understanding the full landscape, ecological, and cumulative impacts of the complete project, including the additional corridors, structures, and construction effects that connection infrastructure can bring.
Cumulative impact is a recurring theme for Mid Wales. Communities are already facing multiple energy and grid proposals, each bringing their own construction periods, traffic, habitat disruption, and landscape change. When developments overlap in time or are clustered across the same region, the combined effect can be far greater than the sum of each scheme viewed in isolation. Where cumulative assessment is limited or missing, objectors argue that the planning process is being asked to approve large scale change without properly describing what that change will look and feel like in lived reality.
For people considering an objection, the issues commonly raised are clear. Nant Mithil Energy Park is not simply a set of turbines on a distant skyline. It is a large engineered intervention across 1,773 ha, with 30 turbines up to 220 m, extensive track construction, forestry removal, excavation, and night-time lighting. It sits at the headwaters of a river system connected to the River Wye SAC and beside protected sites, with recognised risks to habitats, species, water quality, and landscape character. Objections also focus on gaps in assessment, including the lack of Cs-137 radiological evaluation, incomplete hydrology and peat work, and the omission of the required 132 kV grid connection from the assessed scheme.
If you live locally, use the area for recreation, care about dark skies, or are concerned about the protection of the River Wye SAC and the wider Radnor Forest uplands, you may wish to register a formal objection referencing the specific impacts on landscape, biodiversity, hydrology, public amenity, transport, and the completeness of the assessments.
