Yes, EPA’s Surface Water Treatment Rule (SWTR) requires that:
- disinfectant residual concentration at the point of entry (POE) to the distribution system cannot be less than 0.2 mg/L for more than 4 hours
- disinfectant residual concentration in the distribution system cannot be undetectable or have a heterotrophic plate count (HPC) of more than 500/mL, in more than 5% of the samples in one month, for 2 consecutive months
- Residual concentrations can be measured as free chlorine, total chlorine, combined chlorine (total chlorine minus free chlorine), or chlorine dioxide
- monitoring for disinfectant residual concentrations at the same locations and at the same times as total coliforms are sampled under the Total Coliform Rule or the Revised Total Coliform Rule (as of April 2016).
Here's a link to the EPA's SWTR webpage for more information: