Under the Ground Water Rule, large systems disinfecting must monitor continuously while small systems must monitor daily.

• A. Large systems continuously; Small systems daily
• B. Large systems daily; Small systems continuously
• C. Large systems every 4 hours; Small systems once per shift
• D. Large systems once per shift; Small systems every 4 hours

Answer: (A)

The key idea is that monitoring requirements under the Ground Water Rule scale with system size to ensure ongoing protection. Large disinfecting groundwater systems must have continuous monitoring of the disinfectant residual, so the system can detect and respond immediately to any drop in residual and prevent unsafe conditions in a big, complex distribution network. Smaller systems are allowed to monitor daily because their simpler, smaller-scale operations carry lower risk and daily checks are typically sufficient to catch problems promptly.

So, the best choice aligns with continuous monitoring for large systems and daily monitoring for small systems. The other options would either misstate the frequency for large or small systems or imply intervals (like every 4 hours or once per shift) that the rule does not require.