Q4-1 Where can I check whether the retaining wall is safe?

Whether the retaining wall is safe depends on the maintenance and management of the owners of the retaining wall, so the government cannot confirm or guarantee it, but it can be confirmed that the procedure has been legally taken.
Confirmation varies according to whether it is thing by permission of construction about residential land development or thing by public establishment confirmation of Building Standard Act (outside site). If you live in the residential land development construction restricted area, it is highly likely that it is due to permission for construction related to residential land development, so please consult with the person in charge of each area of the residential land examination department.

Summary of Guides, etc. on this answer

• About permission of construction about residential land development
  “Guide to Residential Land Development” Part 1, Chapter 2, 1

Contact for inquiries regarding this answer

• About permission of construction about residential land development
  Housing and Architecture Bureau Residential Land Examination Department

For specific details in a specific location, please contact the person in charge of each area.