Certain operators discharging water have to first obtain National Pollutant Discharge Elimination System permits. It is to prevent discharge of harmful pollutants through MS4 which is a system of conveyances owned by a public entity to discharge the waters. Such a conveyance is designed to collect or carry storm water through ditches, pipes and storm drains. This system is not a sewage treatment plant or its part. The first phase of MS4 covers medium and large size cities as well as counties that have a population of 100,000 or more. It regulates their storm water discharge. The second MS4 phase covers hospitals, prisons, public universities, and some other public establishments. The NPDES is regulated by the United States Environmental Protection Agency. All public entities discharging water must comply with the laws and regulations governing MS4 requirements. There are state specific and municipal specific requirements. The purpose of all these regulations is to minimize the impact of water discharge runoff on common ground and surface water bodies.
