Osaka City, Tokyo Toyosu (Koto-ku, Tokyo) - Plow field restoration (around 2007)

Osaka City, Tokyo Toyosu (Koto-ku, Tokyo) - Plow field restoration (around 2007)

In the 2000s, as industrial zones formed during Japan's rapid economic growth period declined in Japan's metropolitan areas, "brownfield revitalization," the conversion of former factory sites into residential and commercial facilities, became an important urban issue. However, many former factory sites were contaminated with volatile organic compounds, heavy metals, and oils, posing a serious obstacle to urban redevelopment, and the Soil Contamination Countermeasures Law, enacted in 2003, required landowners to investigate, report, and take cleanup measures, making "elimination of environmental risks" a prerequisite for proceeding with redevelopment.

In Osaka City, the focus was on the redevelopment of industrial sites in the bay area, and heavy metal and oil contamination was identified as a problem at the former sites of petrochemical complexes and steel-related facilities. In promoting redevelopment, the local government, general contractors, and environmental companies worked together to introduce a purification process and convert the sites into logistics centers and condominium developments. Remediation methods used included soil washing and solidification and stabilization, low-temperature thermal desorption for oil contamination, and soil gas suction and activated carbon treatment for VOCs.

Meanwhile, in Tokyo, the former Tokyo Gas factory site on Toyosu attracted nationwide attention when surveys from 2001 onward detected benzene and cyanide compounds 1,000 times higher than standards, raising strong concerns about plans to convert the site to a food market. The cleanup cost was estimated at approximately 67 billion yen and became a major point of contention for the Tokyo government. The cleanup methods used included soil excavation and removal, groundwater pumping and activated carbon treatment, and barrier walls to prevent the spread of contamination, and required large-scale technology and long-term monitoring.

The background at the time was the major policy issue of balancing urban redevelopment and environmental risk management. The cases of Osaka and Tokyo show that soil remediation was more than just an environmental measure; it was at the intersection of urban planning, economic policy, and social consensus building. The Toyosu issue, in particular, sparked resident unrest and political confrontation, and the transparency of environmental surveys and the accountability of the government were strongly called into question.

These examples highlight the fact that "brownfield regeneration" in Japan is an effort that involves not only environmental engineering but also social governance. Osaka and Toyosu were symbolic examples of how environmental engineering, urban policy, and citizen consensus must proceed in a three-pronged approach.