Final answer:
The Metropolitan Sewer District of Hamilton County (Ohio) likely violated the Clean Water Act of 1972 by improperly managing combined sewer overflows, which is why they are under a federal consent decree to fix their wastewater control system.
Step-by-step explanation:
The Metropolitan Sewer District of Hamilton County (Ohio) is likely to have violated the Federal Water Pollution Control Act, commonly referred to as the Clean Water Act (CWA) of 1972. This act was a significant environmental law passed by Congress with the goal of maintaining and restoring the quality of the nation's waters, making them swimmable and fishable. The Clean Water Act prohibits the discharge of pollutants into the nation's surface waters without a permit.
The CWA includes regulations for managing combined sewer overflows (CSOs), which can occur in systems like that of Hamilton County during heavy rainfall, leading to the discharge of untreated sewerage. If the Metropolitan Sewer District did not comply with the requirements, such as having necessary permits or adequate control measures in place to prevent these overflows, they could be compelled to fix their wastewater control system under a federal consent decree to adhere to CWA standards.