A proposed amendment to a consent decree concerning operation of a municipal wastewater treatment facility and sewer system in violation of the CWA requires the settling defendant to resize a large tunnel (the Northside Interceptor Tunnel) from 23 million gallons to 10.3 million gallons and add a new requirement for sewer separation at one of its combined sewer overflow discharge points that would otherwise be controlled by the Northside Interceptor Tunnel.