What is the required continuous chlorine residual monitoring population threshold under the SWTR?

Under the Surface Water Treatment Rule (SWTR), the requirement for continuous chlorine residual monitoring applies to public water systems that serve a certain population threshold. In this context, the correct population threshold for requiring continuous monitoring is 3,300 people. This regulation was established to ensure adequate protections against microbial contamination in drinking water, particularly for systems using surface water sources.

For systems serving populations below this threshold, the regulations may allow for less stringent monitoring requirements. Therefore, the choice of 3,300 people is significant, as it marks the point at which continuous monitoring becomes a regulatory necessity to maintain water safety and quality standards. This approach highlights the focus on protecting public health by ensuring sufficient chlorine levels to effectively control pathogens in drinking water.