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An interview with the chairman of the Japan Association on Environmental Studies, Akio Hata (17 June, 2008)

The subject is of the soil contamination of the expected relocation site of the Tokyo Tsukiji Market, at the Toyosu area at the Tokyo Koto Ward. The expert panel of the Government (Chairman Tatemasa Hirata, Wakayama University professor) which has been considering the measures concluded in their proposal, "Safeties can be secured by measures." But the whole picture of the contamination is hidden in a veil of mystery and the concerns about the efficiencies of the measures remain. We asked Osaka University professor, Akio Hata, who has been chasing up the Toyosu contamination, to point out the problem areas. (City News Department: Akihiro Asada)


* The Research

It's wrong to estimate clay layers as impermeable layers. "Hydraulic transmissivity," that indicate the level of the permeability has not come to full disclosure, so the contamination cannot be detected without digging. As a matter of fact, at the redevelopment of the former Mitsubishi Metal Industries, Ltd. site at the Osaka City, Kita Ward, "Osaka Amenity Park (OAP)," heavy-metal contaminations were found out after the construction of the complex facilities such as apartments were finished and the pollution by toxic substances were reaching the third layer of clay, 40-meters underground.
Even though they have only researched shallow points at Toyosu, one-third of the points were found polluted higher than the environmental safety standards, and the range was wide. They should have researched at least 10-meters underground at the whole area. The Tokyo Government made an excuse that opening holes would spread the pollution, but subtle holes are not a problem.

* The Measures

The Toyosu site has a very high groundwater level. Therefore, the drainage is very bad and rain makes the area like a rice paddy. It also takes time for the water level to go down. Especially, at the 5-Quadro, where the fruit and vegetable market is planned to be located, the underground water exists right beneath the land surface. Despite pavements and underground impervious walls, the water will leak from cracks and niches.
It is tech-wise; very difficult to lower the level of the underground water and to purify it to a level that clears the environmental safety standards. Even replaced, the soil has a risk to be polluted again. Safeties could be secured only by replacing the whole polluted soil and pumping up the whole groundwater to purify it, but that would cost a couple of hundreds-billion yen.

* The Influence

Low atmospheric pressure and higher temperatures cause more benzene and cyanogens to vaporize. The estimation of the expert panel was made only under ordinary temperatures and normal pressures--lacking changes of conditions--thus not proper.
Benzene affects the health of a person in a long-term span, but in terms of cyanogens, minim amounts lead to an acute poisoning. If cyanogens would be detected at the market, a situation like, "The Atomic Bomb Tuna (Number 5 Fukuryu-maru that was exposed to radiation by an atomic test shipped their tuna to the Tsukiji Market and caused all the auctions to stop)," would be likely to occur again.
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