What is considered the most certain remedy for dealing with a persistent chemical when immediate peace of mind is required?

Answer

Carefully excavating the top contaminated soil layer and replacing it with fresh topsoil

For small areas where certainty is paramount, the most drastic yet effective measure is physical removal, which involves excavating the top six to twelve inches of the affected soil and substituting it with clean material.

What is considered the most certain remedy for dealing with a persistent chemical when immediate peace of mind is required?
environmentpersistencesoildegradationtoxin