pH

Conductivity (µS∙cm⁻¹)

AMD classes

Diagnostic

pH < 4

>1000

I

confirmed acid mine drainage

4 < pH < 5

>750

II

Acid mine drainage in development confirmed

5 < pH < 6

>500

III

Acid mine drainage in potential development

pH > 6

≤500

IV

No risk of acid mine drainage