Candidate – France
Submission by: GRAND LYON METROPOLE
Project name: LES JARDINS DE PRE GAUDRY
Link: https://www.ilex-paysages.com/portfolio/quartier-pre-gaudry/
Short description
The Pré Gaudry gardens in Lyon are an emblematic example of innovative urban regeneration. A former industrial site has been given a new lease of life. At the heart of a densely populated district and its new campus, it has become a new destination, a local urban oasis, a place to rest and cool off.
The designers opted for a strong and lush planting. Wooded islands intermingle with soft pathways, a large open lawn and a rich network of living spaces. Under a generous canopy, space is optimised, multiplying atmospheres and uses.
A shared desire to design a resource-efficient development has led to a focus on circular economy and in-situ soil fertilisation. The collective intelligence and creative enthusiasm of those involved in the project has enabled us to experiment with new techniques for reusing and revitalising inert soil, transforming it into living, fertile soil.
At a time of climate change and the need for our cities to be resilient, the Pré Gaudry gardens are a true open-air laboratory for the renaturation of urban wastelands into islands of freshness and biodiversity.
Social cohesion
On this former industrial site, the Lyon conurbation has planned two major educational facilities: a new local secondary school for 600 pupils and the EM Business School for 5,000 students and teachers.
A peaceful space
More than just a forecourt to link these two establishments and manage traffic flows and reception, the aim was to create a real garden for this new campus, a place to take a break and enjoy the fresh air, a new destination in the heart of the dense neighbourhoods of Gerland.
Natural spaces for living
Designed to slow down the pace of urban life, the Pré Gaudry gardens give pride of place to plants, with wooded islands and shrub beds, a large lawn and soft paths, not forgetting the tall, densely planted trees.
The design of the space creates a variety of atmospheres and living spaces, encouraging people to make the most of them and feel at home. The layout is designed to encourage people to enjoy the friendly, multi-generational spaces: a large lawn, a solarium, planted lounges, a large picnic table and outdoor working areas. The overall design has retained the need to ‘see and be seen’ to maintain a sense of security.
Biodiversity
Biodiversity starts in the soil!
The strength of this project lies in its focus on soil restoration. Often neglected, soil plays a vital role in protecting and restoring biodiversity.
A soil factory
On the one hand, the original soil is compacted and sterilised. On the other, the refusal to bring in soil from outside. How, then, could we create a densely vegetated garden? The only option was to rebuild and reuse the soil on site, a process that involved several stages: first sifting and crushing the silt to remove the rhizomes of Reynoutria japonica, an invasive plant that was present, then composting on site and finally fertilising with green manure. It took only a few months to produce the substrate needed for the entire garden.
Biodynamisation of isolated trees
Biodynamisation of the isolated trees then made it possible to increase the biological potential of the soil: bacteria and/or mycorrhizal strains found on site were replicated in the laboratory and then inoculated at the base of the planted trees.
Living mulch in flower beds
In order to develop soil life, increase its water retention capacity and better protect the plants, an experimental living mulch was placed in all the planted beds: 3 species of earthworm were introduced (inoculated) into the soil.
Economic factors
The sustainable and frugal approach to the whole project has significantly reduced the need for maintenance and the risk of plants dying.
Rainwater recovery
The aim was to ensure that rainwater did not enter the sewerage system. Permeable surfaces were therefore maximised by the creation of continuous pits and the design of recessed landscaped beds with storage areas. The natural overflow is directed to the large lawn designed as a rain garden. On the roadside, Stockholm pits allow rainwater to infiltrate and encourage root development in the trees.
Limiting watering
Tensiometric probes on the trees optimise irrigation by triggering it before the tree is under water stress. This results in better root development and less exposure to temperature fluctuations.
Low maintenance
The quality of the initial soil treatment has reduced the risk of plant loss, while the design of the extensive planting beds has limited the need for maintenance: a resilient plant palette, taking into account the long-term development of the plants, and the use of mulch. In addition, the maintenance of the project was included from the outset (3 years by the company, then taken over by the city’s teams).
Climate
Shade and coolness
The shared ambition to make the Pré Gaudry garden a local island of coolness in the heart of the metropolis required work on several fronts: a high shade factor, complete desilting of the soil, infiltration of rainwater into all the garden beds and lawns, a continuous substrate to ensure continuity of the brown screen over the entire surface of the garden, and the creation of a complete environment with three planting layers: herbaceous, shrubby and woody.
The creation of this island of coolness has given pride of place to the plants, with a canopy of 174 trees, a high shading coefficient and a planted area of 5,600 m², i.e. half the area created.
Water conservation
The project is also based on exemplary management of water resources, with rainwater harvesting and infiltration systems and optimised submersible irrigation to reduce water stress on the plants. 100% of rainwater is recovered through infiltration into the ground.
Brown infrastructure
Finally, a continuous brown screen has been installed throughout the garden to encourage biodiversity and slow down the water cycle.
Wellbeing of visitors/users
A true island of freshness
With the support of the Agence de l’Eau, the Jardins du Pré Gaudry have been designed as an island of coolness to help schoolchildren, students and local residents recharge their batteries. They form a complete natural environment with three levels of planting and can provide plenty of shade in the summer.
A peaceful environment
The main walkway is complemented by more intimate counter avenues through the flowerbeds, leading to a number of areas for rest and relaxation. Whether you’re taking a lunch break, working at the large outdoor table between classes, waiting for a friend or chatting to a relative, the quality of the landscaping creates a calm and reassuring environment for everyone. The large south-facing lawn is a true space of freedom. It leads gently to Fontenay Avenue, a green lung at the heart of Gerland and a privileged route for pedestrians, prams and people with reduced mobility.
The selection, origin and quality of used products and materials (greenery and constructing materials)
A diversified and resistant plant palette
The plant palette for the Jardins de Pré-Gaudry consists of three layers: trees, shrubs, and herbaceous perennials. It is based on research into local biotopes in the Lyon region. While most of the selected plants are indigenous, some varieties of the same species with superior morphological or adaptive characteristics have been used. Additionally, some horticultural or Mediterranean plants have been added to ensure year-round interest and to enhance biodiversity.
In addition to the standard trees, rows of 30/35 fastigiate trees punctuate the path. Their slender forms make them real landmarks in the space.
The plants were supplied by local nurseries.
In figures: 174 trees planted, 731 balustrades, 1,670 shrubs, 21,000 perennials.
Creating fertile land in situ
The circular economy is at the heart of the project, with in-situ soil recycling, without the need to add soil from outside. The previously sterile and compacted soil has been regenerated by in-situ fertilisation. The creation of a continuous, fertile substrate allows roots to develop and strengthens the brown fabric of the garden.
Simple materials
In order to reduce maintenance costs, the materials used were chosen for their simplicity (concrete, stabilised soil).
The overall design (landscape and optional associated buildings)
The Pré Gaudry gardens in Lyon are an emblematic example of the practical responses that green infrastructure can provide to current urban issues: meeting climate challenges, restoring and maintaining biodiversity, restoring the water cycle, improving the living environment, strengthening social ties, enhancing the attractiveness of the area, user well-being, etc.
Beyond the initial brief
The chosen development proposal went well beyond the initial request, which was for a forecourt to link the new college and the new EM Lyon Business School buildings, and for the extension of the Allée de Fontenay, the main thoroughfare in the Gerland district.
A piece of urban nature
The vision was more ambitious. In addition to managing pedestrian flows, it transformed the esplanade into a veritable garden and cool island. The space has become a place to live, relax and enjoy nature, a new and attractive destination. This urban garden, with its wooded islands, large 2,500 m² lawn and meeting spaces, offers a breath of fresh air in the heart of the densely urbanised neighbourhoods of Gerland.
Multiplying uses
The design multiplies uses, places and situations, offering a network of friendly, multi-generational spaces: nature lounges, a giant 22-metre table, numerous benches around the school courtyards, soft paths, etc.
The impact on the environment (holistic, circular approach)
Soil regeneration
In order to limit the consumption of natural resources, the principles of the circular economy are at the heart of the project. The original soil, which was sterile and compacted, was regenerated using a combination of in-situ fertilisation techniques (composting, biodynamics, earthworm mulching). The fertile substrate produced avoided the need to add soil from outside, thus preserving as much agricultural land as possible.
Conservation of water resources
The aim of not discharging rainwater into the network has determined the design of the public spaces: maximising permeable surfaces, creating continuous pits, designing recessed landscaped beds with storage areas; the large lawn is also a rain garden, and Stockholm pits allow rainwater to infiltrate while encouraging tree root development.
Tensiometric probes also allow for a significant reduction in irrigation.
Refreshing the city
The initial ambition to create a local oasis of freshness in the heart of the city has guided the objectives to be achieved: a high coefficient of shading, complete desoiling of the soil, retention and infiltration of rainwater in all the garden beds and lawns, a continuous substrate for a continuous brown screen over the entire surface of the garden, the creation of a complete environment with its three planting layers: herbaceous, shrubby and woody.
The innovation value of the project
The Pré Gaudry gardens rehabilitation project is a highly innovative open-air laboratory for the reclamation of degraded soils in an urban environment. It is based on a co-construction approach and state-of-the-art soil engineering, with the aim of revitalising sterile soil by creating a living, fertile anthroposol while limiting external inputs.
One of the most innovative aspects of the project is the multidisciplinary and local approach to soil amelioration. The complete desilting of the soil, combined with advanced techniques such as the mechanical treatment of Japanese knotweed in situ, the inoculation of earthworms and bacteria, and the integrated management of rainwater, made it possible not only to conserve resources but also to develop a fertile soil in situ. The aim was to recreate conditions conducive to vegetation without resorting to imported soil, a challenge that was met thanks to the collaboration of all those involved.
Experimentation with agro-ecological techniques, such as earthworm planting in collaboration with the INRA, played a key role in the biodynamisation of the soil. By using different species of earthworms to improve soil structure and promote water retention, this technique has helped to sustain the development of the planted vegetation. At the same time, rigorous monitoring protocols, including tomography, have been put in place.