Soil contributes significantly to the growth of the growth of living organisms and circulation of water.
Soil contamination usually occurs as a result of illegal waste disposal or leakage of wastewater from factories/business facilities.
Soil contamination is characterized by a high level of such accumulations and ingestion of groundwater contaminated by hazardous substances in the soil, or the contaminated soil itself, may cause damage to human health.
Contaminated soil is therefore closely related to contaminated groundwater.
Once soil or groundwater is contaminated, the persistent adverse effects cannot be eliminated easily.
Therefore, effective measures are essential to reduce soil and groundwater contamination.
In the early 1970s, soil contamination by chromium (VI) compounds contained in chromium slag occurred at old chemical factory sites in the Koto and Edogawa wards. Since then, soil contamination in urban areas has become a serious problem.
In October 2001, according to the Tokyo Metropolitan Environmental Security Ordinance, Tokyo Metropolitan Government (TMG) requires those business companies that handle hazardous substances and are making radical reforms to areas of land to investigate the conditions of soil contamination and to improve the contaminated soil in the event of detection of soil contamination.
The business companies that handle hazardous substances are required to investigate the conditions of soil contamination at the time of any factory closure. Such investigations have revealed soil contamination in approximately 35% of old factory sites. Sectors that radically reform land areas must investigate the history of use of the lands concerned. These investigations suggested that soil contamination might occur in approximately 28% of such areas.
The Japanese Government implemented the Soil Contamination Countermeasures Law in February 2003. Following implementation of the law, 80 districts in Tokyo were designated as special zones. Elimination of soil contamination (decontamination) was conducted in 51 of these 80 districts and their designation was then withdrawn (as of March 2008)
Groundwater accounts for approximately 10% of water usage in Tokyo. Groundwater is not only an important water resource but also an indispensable part of water circulation.
Using excessive amounts of groundwater may cause the land to sink. Because groundwater flows slowly, its contamination tends to prolong effects on the environment. For this reason, conservation of groundwater is an important issue for environmental protection in Tokyo.
TMG has conducted groundwater quality studies in all the districts in Tokyo since the wells used as water sources were discovered to be contaminated with trichloroethylene in 1982. According to the results of studies conducted in fiscal 2006, the measurements obtained at 4 of 71 spots exceeded Environmental Quality Standards. Furthermore, the Government advises owners of the factories where hazardous substances including trichloroethylene are used in controlling infiltration into groundwater and provides appropriate supervision in line with the Water Pollution Control Law.
If groundwater contamination is detected at a site, the owners of the adjacent factories where hazardous substances are handled are required to investigate whether the soil contamination responsible for the groundwater contamination occurs on the factory property or not, in accordance with the Tokyo Metropolitan Environmental Security Ordinance. If contamination is detected on the factory property, they are required to decontaminate both soil and groundwater.
Methods for Groundwater Surveys| Name of survey | Purpose of survey | Details of survey |
|---|---|---|
| Survey of overall conditions | Collection of data about overall conditions of groundwater quality in all Tokyo areas | Implementation of measurements at one spotin each block |
| Survey of areas adjacent to the contaminated well | Confirmation of the range of contamination in the block where new contamination is detected according the results of the survey on overall conditions | Measurement of water quality collected from wells adjacent to the block where new contamination is detected |
| Regular monitoring survey | Continuous monitoring after identification of contamination | Continuous measurement of water quality from the contaminated well |
in the text and access
