Source of the Contamination

Mission chain
Briefing
I’m not saying our water’s been tampered with, but based on your samples, I can’t rule out the possibility either. Would you return to the Dam and see what’s wrong?
Objectives
Directive · step 01
Reach the Water Treatment Building in The Dam
Directive · step 02
Search for the Flood Spill Intake near the Swamp
Directive · step 03
Investigate any suspicious objects
Sources: [1]