Suitable Alternative Natural Green Spaces (SANGS) – Arborfield Garrison, Berkshire

OVERVIEW:

As part of the overall package for Arborfield, Suitable Alternative Natural Green Spaces, also known as SANGS 1 and 2 had to be developed.

CHALLENGE

This would involve dealing with various infestations of Japanese Knotweed and ensuring that the plant and spores were removed from the land. Earth had to be moved to ensure the SANGS could deal with a ‘once in a lifetime weather event’, so all water landing on the area could run away quickly and easily – reducing the threat of flooding. Trees would have to be removed and replacements planted, along with solutions put in place to help protect the local species of wildlife.

SOLUTION

As many different species were living in the area, different Eco Features were installed to cater for their individual needs.

Bat Boxes (general) had to be installed away from light sources in order not to disturb the bats. They also needed to be set facing south, south-east, south west in order to allow for daytime warming, but away from any prevailing wind and rain.

Bat Boxes (hibernation) were located at least 4 metres from the ground and were installed as high as possible to deter predation and disturbance but were low enough to enable maintenance. They all had to face in different directions but needed to avoid the prevailing wind and rain and generally were facing North, north-east or north-west to maintain a constant temperature.

Small Open Front Bird Boxes were put in place for small songbirds such as robins, wrens and redstarts. The box entrances were sheltered from the prevailing wind, rain and strong sunlight. Boxes had to be installed away from potential predators such as cats and grey squirrels. Advice from the RSBP website was used which stated “Open-fronted boxes for robins and wrens need to be low down, below 2m, well hidden in vegetation. Those for spotted fly catchers need to be 2-4m high, sheltered by vegetation but with a clear outlook

Small Cavity Bird Boxes for birds such as blue tits, great tits and starlings were installed with similar designs as the open front versions described above. Again, advice was sought form the RSPB website which stated: “Boxes for tits, sparrows or starlings should be fixed two to four metres up a tree (or a wall).

Tawny Owl and Stock Dove Bird Box installations took place on the more mature trees, advice for these was taken from the Barn Owl Trust (Leaflet No.27, 2010) which advised: “Nest boxes need to be sited in one of the most mature trees in the woodland, preferably within the woodland itself rather than on the fringes. Fix your nest box securely to a large tree…the box should be secured not less than 3.7 metres (12’) up or higher if possible. Always face the box entrance away from the prevailing wind (generally this means avoiding the west or south-west).

Kestrel Open Nest Boxes had to be erected near areas of semi-improved grassland which was home to small mammal prey and located on either on isolated trees or at the edge of a woodland overlooking open land. The fronts of the boxes were sheltered from the elements and were angled vertically or slightly downwards.

Barn Owl Boxes were installed so they were sheltered from the prevailing elements. Advice was taken from the Nest Boxes for Use on Trees leaflet No.2 from the Barn Owl Trust (2010): “An isolated tree near an area of good habitat is ideal (for siting a nest box). Whenever possible, choose a tree with rough bark to enable owlets to climb back up to the box should they fall out. Trees on the outside of a copse are acceptable but avoid trees within woodland. If possible, choose a deciduous tree or a Scots Pine. The ideal tree is old and very big. Pick a tree where the box will be visible below the crown (twigs/leaves) of the tree so that Barn Owls can see it and can fly in and out from various directions without having to negotiate small branches in the dark. A height in the region of 4.5-7 metres (14′-24′) may be achieved depending on the tree concerned.

Retained Dead Wood and Loggeries made use of the largest felled trunk and stem sections measuring 10-15cm in diameter and were placed flat on the ground in appropriate locations. Trees recycled for this included oak, beech, sycamore and ash with bark still attached. They were sunk into the ground together to an approximate depth of 60cm in partially shaded areas. Retained dead wood were secured using wire mesh and fenced off or hidden with vegetation if required.

Invertebrate Shelters were installed to provide additional habitat for solitary bees, lacewings and ladybirds. They needed to be placed in a sheltered place either next to a pond or near nectar/pollenating plants. Also known as insect hotels, these were erected at least 1.5m off the ground on suitable trees in sunny but sheltered spots. Designs that were used included Bee and Bug Biomes, Esschert Designed Wood Insect hotels and Bespoke Multifunctional Invertebrate Habitats.

Six Hedgehog Boxes were evenly distributed throughout the northern section of the SANGS. These were incorporated into log and brash piles and were concealed as deep as possible within a perimeter feature to avoid interference by members of the public.

Reptile Hibernacula were constructed of rubble or alternative material and covered with topsoil created from habitat that was to be cleared. They were made 4m l x 2m w x 1m h, in a sunny position with one of the banks facing in a southerly direction.

Log Piles, these were installed across the SANGS by using felled wood from trees across the site. Log piles were made of logs of varying sizes from minimum size of 1m x 0.5m w x 0.3m h. They were set in sunny locations amongst existing vegetation such as long grass and scattered shrub giving some cover adjacent to the log pile. Care had to be taken to ensure they were installed away from high public access in order to reduce disturbances. Exact locations would be determined in liaison with an ecologist.

Egg Laying Sites were made from piles of grass that were cut from habitats to be cleared. They were then placed in a wooden compost frame – heaps would be at least 1m3, but bigger where possible. All were sited in either full or partial sun.

The Sustainable Urban Drainage (SUD) strategy for Arborfield Green included a series of SUD Ponds. They were installed to provide an important role in managing the surface water drainage and offering valuable habitats for different plants and animals. They were made by creating a depression in the soli then lining it with vegetation. Any water runoff from the surrounding area can seep away into the SUD ponds and through their vegetation liners. Swales were installed to provide a means of temporary storage for surface run off – they are linear grass depressions, relatively wide and shallow. These swales were located throughout Arborfield Green, providing a network that connects the SUD ponds. They are empty during dry weather, but in wet weather the rainwater flows along their length – the vegetation slows down the water and filters the surface water flow.

The ponds in Hazebrouck Meadows are habitat ponds and were designed with a range of depths including shallow edges, ledges and deeper central basins. These provided a range of habitats for different plants and species. Many plants only grow in depths of less than 30cm (known as marginal and emergent plants. Plants that are fully submerged in the pond basin provide shelter for aquatic invertebrates. Residents of these habitat ponds include: Pond Skaters, Great Diving Beetles, Frogs, Toads and Dragonflies In one area of the SANGS, a wooden Bat Barn was constructed with a protective fence surrounding it to stop any members of the public or predators finding their way in. It was constructed in such a way that it provided a warm and insulated roof space in the winter with a cooler ground floor ‘coolbox’ for the warmer summer months. This provided a new home for bats that were previously living in buildings located on the former Arborfield Garrison. The barn was designed for most bat species in mind, especially the Pipistrelles and brown long-eared bats which are local to the area.

Reptile Hibernacula’s are mounds that were placed in various locations around Arborfield Green.

They were put in place to create basking space, shelter and winter hibernation locations for the local reptile population.

Weirs, bridges, headwalls, waterways and paths were also constructed or moved in order to allow the free movement of water and allow the general public to enjoy the surroundings without disturbing the local wildlife. Trees were replanted around the site.

RESULT

Through planning, knowledge and dedication, Lawson Group’s teams helped produce a stunning natural area and habitat next to a major development. This will allow local species to thrive for years to come and safeguard the area from large downpours including a ‘once in a lifetime event’.

To find out more on how Lawson Group can help with your next demolition or asbestos removal project, call 01793 782000, email enquiries@lawsongroup.co.uk.