Les Hortes de Baix constitute a 3.7Ha irrigated heritage site attached to the old town of Caldes de Montbui, a Roman-founded thermal town near Barcelona. This area has suffered the progressive landscape, environmental and social degradation characteristic of peri-urban landscapes of the 20th century, caused mainly by the pollution of the waters of the local stream that supplies the irrigation system, by poor accessibility and by the restructurings of the community of watering. These vegetable gardens were historically irrigated with the leftover thermal water from the washrooms and with rainwater from the stream that empties into the main drain. This ditch, formed by almost 3m high stone walls, is the main element of the irrigation system. But with urban growth, the stream has been covered and much of the black water from the urban centre has been turned into it, thus turning the main ditch of the vegetable gardens into an open sewer. This has caused a significant health risk for horticultural production and has also damaged public accessibility (due to bad smells and a bad visual effect). The shortage of clean water for irrigation has activated the claim of thermal water as a public asset to be reintegrated into the citizenry’s imagination. The project originates from the municipal Public Spaces Board, a space that gives voice to local initiatives for the improvement of public space. The City Council activates the order to respond to the need for more clean water, irrigation, to channel the flow of black water that runs in the open and to facilitate access to the vegetable gardens from the urban centre. As authors of the project we set out to understand private horticultural parcelling as a new self-managed public space that promotes food sovereignty; to co-design the entire process with the community of irrigators and other agents involved, and to recognise the value that traditional water management represents as material and intangible heritage. With the community of horticulturists - about 70 people - the inadequate management of thermal water left over from the spas that is poured into the stream is detected, proposing to reuse it for irrigation together with water from more laundries. Through a two-year participatory action research, the community of irrigators is reactivated and limited interventions are agreed upon that do not alter the current irrigation system or its social management. The work is carried out with a low-cost budget and a Municipal Employment Plan. Maintenance is undertaken by the irrigator community. The project is divided into two phases: the intervention for the sustainable management of the irrigation system and the footbridge to improve the accessibility of which a first section has been executed that connects to the existing access road, while the second section to the stream is currently being developed. Based on the process involved and to guarantee the water supply, the water from the spas is recovered, which accumulates in a compensation glass on Passeig de la Riera, a space for public visibility of the thermal water as well as a meeting point, as happens in the laundromats that border this promenade. From this glass, the thermal water is led to the vegetable gardens. A new public reservoir for accumulation and cooling is built there to distribute the water in daily flood irrigation shifts. The recognition of the operation of the thermal irrigation system allows the existing ditches to be recycled, maintaining their operation by gravity and avoiding the mechanisation of any new device introduced to facilitate their management and maintenance. In the existing main ditch, the black water is channeled to the collector and a footbridge is incorporated to improve access to the area, supported inside the walls so as not to alter the identity value of the characteristic traces of the landscape of these gardens. The presence of material elements typical of horticultural self-construction is enhanced: granite bowls in the main ditch, manual folding ceramic bricks, manual gate boxes, nets and fences. The live willow is reintroduced to the fence, formerly used for wicker basketry heated with thermal water. In addition, it opts for an innovative pilot system: phytoremediation with macrophytes resistant to the temperature of the thermal water and planted on floating planters, to assimilate the residual organic matter without altering the fluctuating condition of the water level of the pond that is filled and emptied daily. We evaluate the project at three levels: political, productive and citizen. At a political level, the Administration has opted for the dignification of the field and the long and intense process of participation culminates in the creation of a hitherto non-existent gardeners' association. A board and commissions are established to ensure the self-management of the vegetable gardens, the establishment of internal rules, communication with the City Council, the visibility of the historical and cultural heritage they represent and the transfer of the necessary intergenerational knowledge. At a productive level, obtaining more clean water allows the practice of organic farming and the increase of irrigation shifts to double the number of days, conditions that strengthen this space of self-production for local consumption and the reduction of emissions. In the long term, it is expected that the cultivated product can be sold for consumption by visitors. At citizen level, the gardens have been opened up to the neighbours, becoming a public space for walking, recognition and pedagogy of the agricultural space. Added to these successes is the challenge experienced by the coordinating architects. Taking on the role of mediators and observers has offered us new conceptual references within ecological and community design, and has allowed us to develop new tools for decision-making and communication of the technical aspects of the project.