Digging a subway means cutting through a lot of dirt, but what to do with it? This is the question that has troubled many construction sites throughout the years and depending on where you’re digging dirt you have different options. The worst, but all too common, option is to send the dirt to a landfill as ridiculous as that sounds. When Line 2 was being built in Toronto they used the dirt to build a whole new park and that approach is becoming popular the world over. Now Toronto is building a new subway and the dirt is being used in nifty ways too.
The hallmark for all cities to get to is the standard set by Paris.
Some global jurisdictions have pushed further into circular approaches that go beyond simple reuse. In France, large volumes of soil from metro construction projects have been integrated into systems designed to keep material within the local economy. Regional operators manage large-scale soil redistribution for parks, green spaces, and land restoration, creating a coordinated soil logistics network across Paris.
Paris’s proactive initiatives like Cycle Terre, carried out between 2018 and 2021, processed suitable excavated clay from the Grand Paris Express project into compressed earth blocks and other low-carbon building materials from a factory 10 kilometres from the excavation sites. This resulted in relatively short transport times and effectively turned soil into a construction input rather than a disposal burden. Ultimately, however, the initiative failed to generate enough commercial contracts and went into liquidation.