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The Japan Association for the 2025 World Exposition (hereinafter referred to as “the Association”) plans to publish the results of gas concentration measurements during the construction of the venue on a regular basis. The results of gas concentration measurements for November and December 2024 have now been compiled.
A summary of the measurement results is as follows:
・No methane gas concentrations of 1.5 vol% or more were detected inside buildings in November and December. In addition, no methane gas was detected in the underground pits of the east and west toilets, where methane gas had been continuously detected in the past. The Association will continue with the installation of mechanical ventilation equipment and detectors in the GW construction area.
・For underground pits for outdoor electrical and telecommunications equipment and rainwater and sewage systems, 104 locations were measured in November and 372 locations were measured in December. A methane gas concentration of 1.5 vol% or more was detected at five locations: two near the east toilet in the GW construction area, two near the west entrance plaza of Transport Terminal 1, and one in the PW construction area near the GW construction area. Methane concentrations of more than 1.5 vol% were not detected in any underground pits for rainwater and sewage systems that were measured for the first time.
・Of the locations where concentrations of 1.5 vol% or more were detected, a concentration of 5 vol% or more was detected twice out of a total of eight measurements taken at one underground pit for electrical and telecommunications equipment near the east toilet. The methane concentration in this pit has been confirmed to be 0 vol% after natural ventilation, however safety measures will continue to be taken during construction, and monitoring will be carried out on an ongoing basis. In addition to ventilation measures, such as replacing the lid with a perforated lid, measures to prevent gas ingress will also be implemented.
・In addition, methane gas concentrations of 5 vol% or more were detected in one underground pit for electrical and telecommunications equipment near the West Entrance Plaza of Transport Terminal 1. Based on these results, safety measures will be taken during construction, and continuous monitoring will be carried out. In addition, ventilation measures have been implemented by replacing the lid with a perforated lid.
*Until the lid is replaced with a perforated lid, measures are being taken to open the lid. Measurements in January confirmed that the gas concentration in the pit was 0 vol%.
In the GW and PW construction zones, all necessary works such as installation of mechanical ventilation equipment and detectors, ingress prevention measures, replacement with perforated manhole covers and permeable paving will be completed by the opening of the Expo, while taking into account the measurement results to date. A system will then be established to constantly measure and check the safety of gas concentrations throughout the venue under the guidance of experts throughout the duration of the Expo, and the status of safety checks will be open to the public.