F. Geology & Hydrology ( PDF | 31.0 MB ) - RWE.com

development area is located along a ridge of hills stretching from Bryn Ocyn
and Tir Mostyn in the north, through Foel Frech in the centre, to Craig Bronbanog
in the south. Numerous watercourses intersect the development area,
often located within steep-sided valleys and flowing at steep gradients
unsuitable for peat accumulation. The sources of these watercourses are
however generally located in flatter areas and small depressions where water
tends to accumulate, and are suitable areas for peat formation. Cross
reference with the BGS map data shows that all of the BGS mapped peat
deposits are located in watercourse source areas, including a large (max 450m
by 300m) deposit surrounding the Aber Waen-lydan source and a 2km long
continuous peat deposit in the upper reaches of Nant Llyfarddu and an
unnamed tributary of Afon Alwen.
Not all watercourses draining the site have a BGS mapped peat deposit in
their upper reaches and it is possible that these areas may hold previously
unidentified peat deposits. Other areas which could be suitable for peat
accumulation include spurs and other flatter parts of the site. The potential
for peat accumulation based on topographic features is considered in more
detail for each turbine location in Section 3.2.
3.1.6 Phase 1 Habitat Survey
The results of the Phase 1 Habitat Survey and NVC survey (see Annex E of the
ES) were reviewed to locate any areas of identified peat-forming mire habitat
or plant communities within the development area, which could be an
indication of significant peat accumulations and active peat bog. It should be
noted, however, that the majority of the development area is characterised by
coniferous plantation and therefore the vegetation survey results will only
indicate areas of peatland that have not been previously planted over.
The Phase 1 Habitat survey did not identify any mire habitat within the
development area. Mire habitat includes: blanket bog; raised bog; wet and
dry modified bog; acid, neutral or basic flushes; bryophyte dominated spring;
and valley, basin and flood plain mires. Parts of the development area have,
however, been classified as acid dry heathland, where ericoid species
constitute greater than 25% of the shrub layer (and there is less than 30% tree
cover). Clearance of previous coniferous plantations has created micromosaics
of habitats within the heathland, with the undulating micro
topography resulting in the colonisation of depressions by species such as:
Sphagnum mosses, hare’s tail cotton-grass, sedges and rushes (ie species
thriving in the wet); and on the raised areas by heather, bilberry, heath
bedstraw and wavy hair-grass. Although some of these species indicate the
presence of underlying peat in certain areas, the NVC results suggest that the
wider habitat should still be considered as heath habitat.
The lack of mire habitat within the development area indicates that, although
there may be peat deposits beneath the coniferous plantation forest and
beneath the heathland habitat, the site cannot be considered to hold important
active peatland habitat (ie there are no areas characterised within the survey
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