The Oncopole photovoltaic park, on the banks of the Garonne, on the former AZF site

Chaire Paysage et énergie (ENSP), 2022

The project was born from the political will of Toulouse Métropole and RMET (Régie Municipale d’Electricité de Toulouse) to rehabilitate the former « AZF » site affected by the 2001 explosion. The photovoltaic power plant, deliberately developed from the Land’Art current, allows the development of this heavily polluted site and its rebirth. Located on a surface of 19 Ha and developing a production capacity of 15 MWp, it is the largest photovoltaic plant in France installed in an urban area.

The Oncopole ZAC in Toulouse, in the heart of the industrial Garonne valley

1 - The Oncopôle ZAC, the south of Toulouse in transformation

The city of Toulouse is located at a natural crossroads between the Pyrenees, the Atlantic and the Mediterranean. It stretches around the broad valley of the Garonne, bordered by its hillsides which open up a generous expanse of alluvial plain. The ZAC de l’Oncopôle, on which the photovoltaic park of the same name is located, is a district situated in the south-west of Toulouse, on the banks of the Garonne. It is a centre of activity focused on research and health. Its vocation is mainly tertiary, with very few residential buildings. The district includes the Marchant Hospital, the Toulouse University Cancer Institute and the Chapitre economic zone. It is crossed by numerous roads that organize the metropolitan ring road.

2 - The Grand Parc Garonne project

The Grand Parc Garonne urban project supported by the Toulouse metropolis aims to reclaim the banks of the river over a 32 kilometre stretch. To achieve this, the city is seeking to develop pedestrian and cycle paths, enhance the natural heritage, strengthen water-related uses and develop new cultural and convivial spaces. The Grand Parc Garonne urban project encompasses the northern part of the Ile du Ramier located opposite the Oncopôle district. The southern part of the island still has an industrial vocation. In particular, there is a factory producing the components of ArianeGroup’s rocket propellants. The chain of islands, including the Ile du Ramier, still has the remains of an important historical industrial activity linked to the production of black powder (gunpowder). Today, the development of the Poudrerie Park tells this story, with the conservation of old buildings and an outdoor exhibition. These are the witnesses of a former identity of these islands, linked to an industrial activity.

3 - Industrial risk and symbolic innovations

On the banks of the Garonne, the new Oncopôle district and the photovoltaic plant occupy the former AZF factory site. The AZF explosion on 21 September 2001 destroyed many buildings, killing and injuring many people and causing lasting trauma to the people of Toulouse. The factory site has since been razed and largely cleaned up. The Oncopôle district of Toulouse is a project initiated by the municipality and the State. It began in September 2006 and was completed in 2014. The cancer research institute is a symbolic building there: a centre linked to care developed on a former industrial disaster site. This is the context in which the Oncopôle photovoltaic park is being built: a risky industrial past, a land opportunity to develop a project on polluted land, but also a sector linked to innovations and contemporary research.

The photovoltaic park and the land art project, carriers of a new vocation for the former industrial site

1 - Other futures for a polluted site that is off limits

The photovoltaic solar power plant is an operation contributing to the reconversion of part of the site, as well as to the metropolitan approach to energy transition. Indeed, Toulouse Métropole has been implementing its climate, air and energy plan since 2019. The site chosen for the photovoltaic park is one of the areas that are still polluted. Following the pre-existing industrial activities, the local authority had cleared the site and installed a cover of approximately 50 cm of topsoil mixed with crushed concrete. Initially, this space was to be integrated into a « Grand Parc Garonne » landscaping project developed on other sections of the river, but as the space was still subject to pollution risks, access to the site for users proved impossible.

2 - Joint management of a symbolically important site

The metropolis launched a call for expressions of interest in 2017. Urbasolar, a company specialising in the rehabilitation of degraded sites into solar parks, was selected to develop the project. The management of the site and the financial investments are shared between public, citizen and private actors: the developer Urbasolar, the Régie Municipale d’Electricité de Toulouse, Toulouse Métropole, the citizen cooperative Citoy’enR and the Agence Régionale Énergie Climat (AREC) Occitanie. Urbasolar is carrying out the project, with an application for a prefectural building permit at the end of 2017, which will be granted in May 2018.

3 - Historical monuments and landscape integration

The project is partially located within the 500m perimeter around the Marchant Hospital, a listed building. The submission of the project for the building permit therefore requires the approval of the Architecte des Bâtiments de France (ABF). The DREAL is involved in the process in terms of the landscape theme. Following several technical meetings, it was suggested to the project leader that he develop a land-art project to enhance the technical installation. Potentially, it could be perceived by travellers landing at Toulouse-Blagnac airport (landing axis), but above all by future users of the urban cable car (between the Oncopôle and Paul Sabatier University). The plastic intervention also enables the technical project to be enhanced. Several candidates responded to the consultation launched by Toulouse Métropole and a jury determined the most interesting and, above all, the most sustainable project. The Toulouse artist Damien Aspe was chosen to design the landscape integration using Land Art. The building permit was validated and the project built in 2020.

A site with a strong symbolic charge and part of the geography of the Toulouse metropolis

1 - Terms of reference for an artistic conception of landscape integration

The developer and Toulouse Metropole have drawn up a set of specifications for the artistic intervention for the Oncopôle photovoltaic park project. They participate in the choice of the artist, but do not have any other say in the project decisions. The specifications indicate that the panels must be of a solid colour, with a regular orientation and layout of the locations.

2 - The « Rainbow blast » project, land art and symbol in the landscape

The visual artist Damien Aspe developed his concept for the project, which he entitled « Rainbow Blast », based on the notion of shock waves.

The deaths, injuries, material damage and trauma of the people of Toulouse were clearly caused, not by the explosion, but by the shockwave of the explosion. Moreover, the heart of the AZF trial lies in the scientific study of this acoustic phenomenon. In order to explain their theories to the neophytes that we are, the experts must materialize the propagation of sound in a graphic way for a good presentation and understanding of it. An auditory phenomenon is then transformed into a visual phenomenon. In order to perceive the shapes and speeds of propagation, the use of colour gradients seems invariable. The different graphs of the experts of the AZF trial are an example of this. It seems interesting to draw inspiration from these technical diagrams and to reproduce the sound shock wave in a visual way. Extract from Damien Aspe’s project file.

The space is thus cut out by concentric curves from the hypocentre zone of the explosion, in order to obtain a gradient of rounded colours on the terrain of the photovoltaic park. The artist uses photomontages and contextualised diagrams to explain his point. This artistic intervention allows the hypocentre of the explosion to be materialized in an indirect way, in order to keep the memory of it. The gradient of curved colours opposes the natural counter-curve of the site.

According to the artist, the choice of colours implies the visual aspect of an inverted rainbow. This deliberate choice of the rainbow was made for several reasons:

The sun is a source of energy and light (colours). The role of a solar power plant is to recover the energy of the sun’s rays and transform it into electricity. The artwork reproduces a rainbow, which is an optical and meteorological phenomenon that makes the continuous spectrum of sunlight visible. In oriental culture, the rainbow has always been considered as a mediation path between the upper and the lower. Here, through the reflection of the sky in the photovoltaic panels, and the rainbow produced by the coloured panels, these vertical elements are presented in their horizontality. In Western symbolism, the rainbow is often associated with joy and cheerfulness or renewal. Its presence on a site with strong traumatic connotations makes sense. The rainbow is also used as a flag of peace, could it become a symbol of the end of the legal conflict around this story? By its location, the rainbow of the solar power plant is geographically in the middle, between the two strategic points that oppose the two parties… quite a symbol. It also embodies the environmental protection movement, notably by Greenpeace via the Rainbow Warrior story. This strong connotation takes on its interest on a site that belonged to a Seveso petrochemical industry, whose part on which the rainbow unfolds is still polluted.

(Extract from Damien Aspe’s project file).

Thus, the conception of Land art to materialise the landscape integration of the panels of the power station allows the symbolic and iconic dimension to be associated with technical issues, for a site with a turbulent history, needing to be associated with a discourse of both renewal and memory.

3 - Conversion of the site at risk

The Oncopôle solar power plant includes technical innovations that allow its installation to be adapted to a site that has been partially decontaminated and is located on the left bank of the Garonne. The land belongs to the Toulouse metropolis. The shape of the plot is irregular and slightly set back from the river. The power plant is located in the red zone of the PPRi (HRVi), where construction is prohibited except in exceptional cases (hazard of less than 50 cm of water in periods of high flooding and negligible effect of the installations on the impact of the water level upstream). Prior to the construction of the park, the area was managed as grassland, with no access possible. Construction was forbidden for a long time, and permission was finally obtained for the installation of the park.

4 - Landscaping of access and views

The site can be seen from overflights of planes landing at Blagnac airport, from the view of future users of the Toulouse cable car, as well as from the hillsides of Pech David and in particular from Pech David Park located opposite on the other bank of the Garonne. The site’s surroundings are visually a little steep when one is on the path that runs alongside it, with high metal fences delimiting the space. The fence is being revegetated and educational panels are to be installed.

The visual impression of the coloured panels is interesting from the slopes of Pech David and fits well with the context of the area (innovation centres, nearby ring road, industrial zone). However, as the back of the panels does not seem to have been specifically worked on, the viewpoint appears less interesting when driving further north on the hillside. A pedestrian and bicycle path along the banks of the Garonne (Via Garona) runs alongside the photovoltaic park to the west. Further west, part of the explosion site still remains. 5 - Materiality of the panels, flooding and land art The Oncopôle park is becoming one of the largest French photovoltaic power plants in an urban environment, consisting of 35,000 photovoltaic panels. As the site is located in a flood-prone and polluted area, digging was avoided; only piles could be « driven » into the ground at a greater spacing than for a traditional power plant. The photovoltaic tables also had to be raised to allow the water to flow freely.

1500 coloured panels are inserted between the photovoltaic modules.

Geographical integration for ground-mounted park projects

1 - A desire for landscape integration

One of the interests of the project seems to have obtained from the community and its project leader a step forward in the reflection on the « plastic » work of a photovoltaic park. However, the implementation of the project details could have gone further in the attention to detail. The final result lacks some ambition; the coloured panels are too few in number and too inconspicuous. Moreover, it was not possible for the public actors to highlight the qualitative treatment of certain details, such as the base of the electrical equipment, or a landscape project linked to the photovoltaic park, which would have brought real added value to this site located in a natural area on the banks of the Garonne.

2 - The « Garonne grandeur nature » plan and the inclusion of the site in its geography

The « Garonne grandeur nature » plan supported by the Toulouse metropolis aims to carry out numerous actions to make the link between the city and the river more tangible. It is undoubtedly regrettable that in this context of a global desire for nature in the city, the analysis of the landscape inscription has not taken into account the reflections on landscape issues integrating other dimensions than that of the history of the AZF site (for example, by taking an interest in the ecological and geomorphological interest specific to the environment of the Garonne banks) and by leaving aside the questions of accessibility to the banks.

3 - The climate, air and energy plan

The Toulouse metropolitan area has been implementing its climate and energy plan since 2019. This project is part of this plan, and its scope is interesting. The electricity produced is on the scale of the city’s needs (19,350 MWh produced per year, the equivalent of the electricity consumption of 4,100 households), and the shared investments guarantee a contribution for the city and its citizens in the long term.


  • Experience extracted from the guide «  Energy transition : towards desirable landscapes  » carried out in 2021 - 2022 by the Landscape and Energy Chair of the Ecole Nationale Supérieure du Paysage de Versailles :

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