Do I have to remove the contamination as soon as it is designated as an area requiring action or a notification area at the time of character change?

The Soil Contamination Countermeasures Act requires that human intake of harmful substances contained in contaminated soil be cut off.
Measures such as the removal of contamination are required in areas requiring action, but it is not necessarily necessary to remove soil contamination, but it is also possible to take measures such as pavement and contain the original position.
In addition, the notification area required at the time of character change is an area where measures such as removal of pollution are not required. However, a notification is required at least 14 days before changing the characteristics of the land.
※The same applies to ordinances related to the conservation, etc. of the living environment in Yokohama.

・Structure of Soil Contamination Countermeasures (Ministry of the Environment) (outside site)