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The Hanging Gardens of the Circle Line is a proposal to transform seven defunct ventilation shafts along the length of the Circle Line. These shafts - a legacy of the steam era of the early Metropolitan and District Railways - remain hidden behind high walls and false facades in an attempt to conceal their presence.
Out of the seven chosen ventilation shafts (there are thirty in total), one is elaborated on here: the ventiltion shaft at 23-24 Leinster Gardens. Whereas other shafts are hidden behind anonymous brick walls, this site is unique for its false facade - erected to conceal the signs of industry from the wealthy neighbourhood of the time.
Spatially, this concealment presents an opportunity to discretely introduce something unexpected into the area.
In order to do this, however, attention must be paid to the TfL railway below (used by both the Circle and District lines). The issue of ownership is a grey area here because the ground plane is being created rather than claimed. While it is assumed that TfL would claim air rights above the track, it is worth noting that such claims are not made when the same track passes beneath other, intact, properties; nor are TfL denied the right to build tunnels due to these properties’ sub-soil rights(which hypothetically extend to the centre of the Earth).
It is this sub-surface nature of TfL’s presence which creates the ingredients for the proposal. Theseventilation shafts, while no longer required for the venting of steam trains’ condensers, present unexpected moments of connection between the underground and the everyday world. A unique microclimate is created: heat from the trains gives a mediated all-year-round temperature to the tunnel walls (temperatures will rise further when the mechanically ventilated S Stock trains are introduced between 2010-2013); the air is heavy with particles not found elsewhere (iron from brake linings, hair and skin from passengers); and unique fauna from the underground has a rare access point to the world above (e.g. the mosquito, Culex pipiens molestus, lives only in the London Underground and has evolved to be an entirely distinct species).
The area to be served by the proposal is very much characterised by its proximity to Hyde Park with an abundance of hotels and expensive properties altered to allow for more dense but less expensive lets. Due to this, it could be argued that the area is characterised by a largely transient community of tourists, business people, and short-term lets.
This is echoed, too, in the Park itself, which - though providing ample public park space - does so with a broader catchment than could benefit any immediate neighbours. With no direct control or privacy over communal space, the sense of community is diluted to the point of non-existence. Both private and public space are largely occupied by a population in flux. This proposal seeks to improve this situation by suggesting a series of interventions spaced throughout such London communities for the benefit of the local long-term residents, shop keepers, and the local ecology.


Proposal:
The Hanging Gardens of the Circle Line celebrate the poetry of small things: the intimacy of tending to seeds and growth over time. They introduce community spaces across London in areas that need it most while allowing TfL to engage in a radically eco-friendly project, resulting in never-before-seen environments.
Each hanging garden is composed of a dense yet lightweight tensile structure hung over a ventilation shaft of the Circle Line. Designed to be structurally secure in order to hold the weight of soil, plants, and people, it also acts as a membrane with activity above and below; the unique climatic inputs of the underground complimenting the existing rain and sun of the above ground.This new relationship between the city and nature creates a micro-climate where moderated soil temperatures (via waste heat from the Underground) and mineral enrichment (via London Underground air particles) mitigate the tide of the seasons and allows for near sub-tropical flora growth. Fauna, too, play their part: the blossoming flowers will eventually give a boost to the dwindling bee population of London. In the interim, however, the London Underground mosquitoes are immediately available from below to pollinate the garden (mosquitoes rely on pollen for energy and move on once a bee population arrives).
For the residents, this unexpected ecology provides many benefits. From the outset, it allows a place to belong - a garden to tend and a process of growth to be a part of. As the first generation of flora blossoms - flowers, ivy, and shrubs - the tended garden offers out berries for residents or local shop owners and flowers for local markets. As the garden matures, fruit trees and more exotic flowers are able to flourish (such as Osteospermum Cultivar, Heliconia Cultivar and Bellis Perennis Cultivar). Amongst this growth, the palette of colours continues to grow.
In addition to the ground plane (which is always available along the length of the garden to ensure disabled access), a new environment for climbing plants such as vines and ivy is created. Taking advantage of the piston effect (where trains entering or exiting a tunnel push warm air out to the surroundings), a constant stream of fresh warm air is directed to these plants, ensuring that they too can benefit from the nutrients and warmth otherwise placed in the soil. This high-level growth is also ideal for those in a wheelchair, when flowerbeds may not be otherwise reachable.


http://www.architectsjournal.co.uk/home/riba-forgotten-spaces/forgotten-spaces-commended-hanging-gardens-of-the-circle-line-by-chris-hildrey/5217409.article
http://news.bbc.co.uk/local/london/hi/people_and_places/arts_and_culture/newsid_8706000/8706961.stm
http://www.architecture.com/RegionsAndInternational/UKNationsAndRegions/England/RIBALondon/EventsAndProjects/ForgottenSpaces2010/WinnersandShortlistedGallery/HangingGardensoftheCircleLinebyChrisHildrey.aspx