At the fundamentals level you learned what the National Primary Drinking Water Regulations are and why they exist. At this level, the question shifts: once a standard exists, how does a system actually prove it's meeting it, day after day, and what has to happen the moment it isn't? This tier covers the operational mechanics every Class C / Class 2 operator needs to run compliance in practice — the Consumer Confidence Report, the Public Notification tier system, routine monitoring schedules, and a distinction that trips up a lot of operators the first time they see it: the difference between an MCL and an Action Level.
Recap and a New Distinction: MCL, MCLG, and Action Level
You already know an MCL is the enforceable limit and the MCLG is the non-enforceable health goal. Now add a third term that behaves differently from both: the Action Level.
An Action Level isn't a d