Alpha
This is a rebuild of Drinking Water Watch and not yet the official record. Use the agency’s current Drinking Water Watch for anything you need to rely on.
Presence/Absence Indicator
From the help published with Drinking Water Watch 3.5, reproduced as delivered.
The Presence/Absence Indicator indicates whether
results of an analysis were positive (P-Presence) or negative (A-Absence).
Indication of presence or absence creates an analytical result for a specific
analyte.