Planning and current status of a new offshore final disposal site in Tokyo Bay (1995-2020s)

Planning and current status of a new offshore final disposal site in Tokyo Bay (1995-2020s)

In 1995, the Tokyo Metropolitan Government and Chiba Prefecture agreed on a plan to establish a new final disposal site for waste in Tokyo Bay, a new sea-level repository. The plan called for the construction of a repository with a total area of approximately 480 hectares off the coast of Kisarazu City, Chiba Prefecture, to accept 1.4 million tons of waste per year. The waste included construction waste, industrial waste, and incinerated ash from household waste. Hazardous substances such as PCBs and heavy metals were also to be properly disposed of. Kajima Corporation, Shimizu Corporation, and Taisei Corporation participated in the construction, while Sumitomo Metal Mining and Hitachi, Ltd. were involved in providing technology for the environmental protection equipment. Fishermen's compensation and ecological impact studies were also conducted to address the concerns of the fishermen's association and local residents in Chiba Prefecture.

In the 2020s, the new marine landfill continues to play an important role in waste disposal in the Tokyo metropolitan area under the management of the Tokyo Metropolitan Government's Bureau of Port and Harbor. The total area of the landfill is equivalent to approximately 100 Tokyo Domes, of which 319 hectares are used for landfill disposal of waste. The waste includes incinerator ash, crushed residues of noncombustible waste, and crushed residues of bulky waste, and the annual volume of waste to be landfilled in the 2020s is estimated to be approximately 500,000 tons. The amount of landfilled waste has been decreasing since the beginning of 1995 due to waste reduction and recycling promotion.

However, due to the difficulty of constructing a new landfill within the Port of Tokyo, measures to extend the life of the landfill have become an important issue. Specific measures include promotion of the 3Rs (reduce, reuse, recycle) of waste, conversion of incinerated ash into resources such as cement material and roadbed material, and improvement of landfill efficiency.

In addition, leachate management, landfill gas management, and environmental monitoring are strictly enforced to protect the environment. After leachate is stored in a collection pond, water quality and quantity are adjusted in a regulating pond, and then treated at a wastewater treatment plant. Landfill gas (mainly methane gas) is collected through degassing wells, and combustion treatment and energy use are also being considered. Environmental monitoring regularly examines the quality of the sea area and air quality around the disposal site to monitor environmental impacts.

The new offshore disposal site is currently located adjacent to the landfill outside the central breakwater in Koto-ku, Tokyo, and will continue to serve as the center of waste disposal. The Tokyo Metropolitan Government has formulated the 9th Revised Port Plan for the Port of Tokyo for the 2040s, and is working to establish a sustainable waste disposal system.