Generation rate and fate of surplus soil extracted in New York City.

With increasing urgency to build earthworks projects to protect against flooding from climate change and mitigate exposure to pollutants in degraded urban soils, many cities could experience increased demand for soil of between 10 and 35 million t in coming decades. This study showed that building construction in New York City (NYC) produces an estimated 1.7 × 106 t of surplus clean native soil (mostly glacial sediments) each year and could be an important source to meet future urban soil demand. This quantity of soil is sufficient to build a 3-m-high earthen levee 21-km long each year and a continuous levee along NYC's 840 km shoreline in about 40 years. Alternately, this quantity is sufficient to build a 15-cm-thick clean soil cover over 7.3 km2 of degraded urban soil each year. Detailed study of the fate of 1.03 × 106 t of surplus soil from 113 building construction projects showed that over 95% was exported, with average one-way soil transportation of about 72 km. Paradoxically, while >74% of soil was recycled, long transportation through a diffused network of recycling facilities caused significant environmental and economic impacts. Each year, surplus soil management from building construction in NYC requires an estimated 60,000 truck-trips and 8.7 × 106 km of truck travel, combusts 4.3 × 106 l of fossil fuel, emits 11,800 t of CO2 and costs over $60 M USD. Soil banking and other programs and public policies to retain soil within cities could increase urban soil supply to meet the rising demand for earthworks projects while also reducing soil transportation and associated environmental and economic impacts and achieving circular urban materials metabolism goals.