La Goccia Urban Forest

Le Officine del Gas and the forest

In 1905 the Union de Gaz de Paris built the Grandi Officine del Gas della Bovisa on a parcel of land shaped like a falling drop, enclosed on every side by railway tracks. The shape gave the area its name. For half a century the works gasified coal to light Milan. As the technology changed the plant was decommissioned in stages and closed for good in 1994.

The plant's gates then stayed shut for thirty years. Pioneer species arrived first and dropped enough leaf litter to build humus. The new soil brought insects, then animals, then plants long considered lost from the Milanese plain. The site now holds eighteen hectares of forest, roughly fifteen thousand trees, more than 250 vascular plant species and forty species of birds, all of it growing on contaminated ground.

Eighty-five years of gas production contaminated the soil. Thirty years of abandonment grew a forest over it. Our work is to undo the damage the industry left without losing the ecosystem that grew in its place. When it is finished, La Goccia will be one of the largest contaminated sites in Europe restored through Nature-based Solutions, and a park of a kind Milan has not had before.

Reading the forest, 2021

In June 2021 we surveyed the spontaneous vegetation. We wanted a figure for what the forest was worth, because until then it had only ever been counted as a cost. We ran it as a citizen science survey: over five days about forty people catalogued the trees, shrubs and herbaceous species growing on the site.

Using the sample area method with iTree Eco, we produced a biomass account for the whole forest and a first estimate of the ecosystem services it provides.

The report opened the conversation with the City of Milan. It led to the collaboration pact of September 2022, and to the founding of Osservatorio La Goccia.

The Osservatorio

Osservatorio La Goccia is the partnership we put together to do the work, and have led since. It started in 2022 with the Municipality of Milan, the Natural History Museum of Milan, CNR-IRET, CFU Italia Nostra and Progetto Natura Onlus. For the European project it grew into an ATS and took on soil science, water engineering, microbiology and social research: Università Statale di Milano, Università di Milano-Bicocca, Iridra, M3R, Kilowatt, cheFare, Futurecologies and PACT.

The forest is already doing part of the clean-up. To help those processes along we had to understand them in detail, so what followed was baseline work: a preparatory analysis plan, a strategic direction document, a supplementary soil characterisation campaign, a full forest census, fauna monitoring, forest soil analysis, and an assessment of how far the ecosystem can recover on its own. The work continued under the 2022 pact, then PNRR funding, and now the European grant.

More information at: osservatorio-goccia.org

GOCCIA, European Urban Initiative

Since December 2024 the work has been funded by GOCCIA, Green Opportunities to Clean-up Contaminants through an Interspecies Alliance, a European Urban Initiative Innovative Action financed in part by the ERDF, led by the Municipality of Milan and running to 2028.

Terrapreta leads Osservatorio La Goccia, one of eleven partners in the consortium and the largest after the Municipality.

Through it we lead Work Package 6, Nature-based Solutions for soil and water restoration. We map the soil across the site for fertility, organic matter, carbon storage and water infiltration. We run the experimental desealing plots, lifting asphalt to watch what roots and new topsoil do without help. And we monitor the plant and microorganism systems that determine what the reclamation should do next.

We also lead the project geodatabase. It holds biodiversity, microclimate, soil and water data from every partner in one versioned reference, and feeds the ecological and microclimatic models the project runs on.

The grant also pays for the recovery of a disused warehouse on site, the Ranch, for forest management run with the public, an ethnographic programme, and a governance model that counts the environment itself as a stakeholder.

The project and its programme: eui-goccia.eu

Designing the park

The RPBW masterplan set the frame for the wider area, the Politecnico's Campus Nord, the Fondazione Scuole Civiche and the rebuilt Bovisa and Villapizzone stations, and assigned the public land to the north to the recovery of the forest.

We are main partner of the Municipality of Milan for the restoration project, and landscape architecture consultant of MM Spa through the design phase. The operational reclamation plan has been approved. The landscape design of the park is in progress and concludes in 2026, with the park delivered by the end of 2028.

Remediation runs area by area, in phases, over several years, combining phyto and bioremediation with desealing and reforestation. The park opens in stages as it goes, rather than all at once at the end.

What opens is not a conventional park. Some areas take visitors. Others stay closed, kept for the species already living there, because the forest is the reason the site is worth recovering at all. In a city facing hotter summers and heavier rainfall, eighteen hectares of mature woodland does work that new planting could not match for decades. La Goccia is being designed to protect that first, and to let Milan in around it.