Final answer:
The water system's operator is responsible for correcting the problem when a Maximum Contaminant Level (MCL) is exceeded in a water system.
Step-by-step explanation:
If a water system exceeds a Maximum Contaminant Level (MCL), the water system's operator is responsible for correcting the problem. According to the Safe Drinking Water Act (SDWA) and its amendments, specifically the Amendment SDWA of 1986, MCLs are enforceable standards set by the Environmental Protection Agency (EPA) to ensure the safety of drinking water. When these levels are exceeded, it is the duty of the water system's operator to address and mitigate the contamination issue, ensuring that water meets safety standards before reaching consumers.