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3.2.7 Water Body and Marginal Areas
Groundwater rebound will result in the formation of a water body within the quarry void with the resulting water level at around 27m AOD. Although steep sided on three sides the north-eastern slope [south-western aspect] shall have more extensive shallows which will provide further ecological diversity.
4 PROGRAMME OF WORKS
4.1 Soils reinstatement
In order to provide suitable substrate for the establishment of calcareous grassland a mix of soils and rock/overburden shall be used. It is important that the soil/soil forming material is of a suitably high pH and low nutrient/phosphate level; this may be tested and adjusted if necessary by altering the mix with quarry fines. This substrate shall also be free draining, particularly on the southern aspect of the grassland area.
Elsewhere the stored soils may also be reinstated to complete restoration prior to planting. The landscaped bund shall be planted with trees to create a woodland corridor; this requires deeper soil forming material and will benefit from the placement of topsoil.
Within the quarry void it may also be beneficial to seed with scrub species. This shall improve landscape fit creating a glen like habitat. In marginal areas which may be seasonally wet this may include willow. In both cases some soil forming material shall be required in order to provide a suitable planting substrate.
4.2 Planting and Maintenance
Planting would be carried out in the first appropriate planting season. On completion of planting there will be a 5 year aftercare period for weed control, beating up and general maintenance.
4.2.1 Woodland
As this is an extension to a semi-natural woodland area the planting of trees should be a 3m centres or more. The basic tall tree framework should be established and infilled with understorey species. Tall trees such as Ash and Oak can be spaced at 6m spacing as standard along the
perimeter and within the centre of the site to give height and structure. Spacing can be reduced at the crown of the mound to increase the sense of curvature. The less tall species can then be inter-planted to give a final 3m spacing throughout.
It is likely that hedgerow and woodland flowers will colonise naturally but species can be introduced by taking litter from Sloggal Glen and spreading it around the planted trees and shrubs.
The following list is based on species found in Sloggal Glen omitting species that are not native to the Isle of Man [apart from Hawthorn]. The structure will be provided by the larger and medium size trees including Ash [Fraxinus excelsior], Mountain Ash [Sorbus aucuparia], Wych Elm [Ulmas glabra] and the understorey will be formed with Hawthorn, [Crataegus monogyna], Holly [Ilex aquifolium], Elder [Sambucus nigra], Dog-rose [Rosa cananina] and Sweet Briar [Rosa rubiginosa]. Additional species that might be considered are Hazel and Oak which would be of benefit to biodiversity and the structure of the woodland belt.
These species will provide habitat for insects, food and shelter for birds and small animals, and food for butterflies.
The suggested species mix is as follows:
The provenance of planting stock should be indigenous to the island as far as possible and grown in IoM nurseries.
| Oak [Quercus petraea] | small feathered |
| Ash [Fraxinus excelsior] | small feathered |
| Wych Elm [Ulmas glabra] | small feathered |
| Mountain Ash [Sorbus aucuparia] | small feathered |
| Hawthorn [Crataegus monogyna] | 40-60cm transplants |
| Elder [Sambucus nigra] | 40-60cm transplants |
| Holly [Ilex aquifolium] | 40-60cm transplants |
| Hazel [Corylus avellana] | 40-60cm transplants |
| Blackthorn [Prunus spinosa] | 40-60cm transplants |
| Dog rose [Rosa canina] | 60-80cm transplants |
| Sweet Briar [Rosa rubiginosa] | 60-80cm transplants |
| Sherard's Downy Rose [Rosa sherardii] | 60-80cm transplants |
Preparation: The area to be planted will be restored and landscaped to a suitable form.
Planting: Notch planting of smaller whips; the slightly larger small feathered trees pit planted and these individual trees protected by 750mm spiral tree guards.
While it may be possible to source a suitable 'brush harvested' seed mix from Rosehill, additional planting may be undertaken using plugs or plants in the same way as is proposed at Colas' New Turkeyland calcareous grassland restoration project.
All rock faces will be left geotechnically stable. Faces shall in part include bare rock which shall be left to naturally weather, primarily on the south-eastern face, and in places shall include scree slopes.
Assisted natural regeneration is the preferred method of vegetation establishment wherever possible as this generally produces a more natural and sustainable habitat. In relation to scrub species it may be possible to simply allow natural revegetation from adjacent seed sources. This should however be closely monitored as part of the aftercare scheme and seeding or brash spreading may be undertaken as necessary. In light of this the proposals for restoration are simply to provide a suitable mosaic of soil forming materials and bare areas, these shall become colonised to varying degrees and produce the desired scrub mosaic.
The water body shall have a gently sloping northern margin with the quarry faces forming low but steep sides to the south-east and south-west. The north-western margin shall vary with steep faces at its southern extent grading up to shallower slopes to the north.
Aftercare of the site shall be subject to an aftercare scheme in line with UK best practice. Restoration of soils will be undertaken immediately after quarrying operations cease. Woodland planting shall be undertaken in the first suitable season after replacement of soils.
Aftercare shall vary in relation to each restored area, in terms of the level of management required and also the temporal extent of such management. In general terms the aftercare should comply with the following:
Year 1
Year 2
Years 3, 4 and 5
Checking and repairing tree protection as necessary, pruning any minor damage and removal of debris or litter. The use of any chemicals would be undertaken by certified personnel in accordance with current standards and regulations.
The restoration scheme, as detailed above, addresses the stability of slopes and provides a framework for the establishment of a variety of habitats.
This scheme shall be of significant benefit to ecology as well as the landscape of the site and the wider area.
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