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National Pollutant Discharge Elimination System

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After the Cuyahoga River caught on fire in 1969, the Environmental Protection Agency (EPA) recognized that the degraded quality of U.S. waterways due to pollution was in need of some serious attention. In 1972, the Clean Water Act was passed, which regulated the emission of pollutants from specific locations, or point sources (i.e., industrial pipes) into waters of the U.S.  


While the quality of our nation’s waters began to improve drastically with the regulation of point source pollutants, polluted water bodies still existed. As was discovered, preventing pollution from point sources was not enough to ensure clean water.  This is because many pollutants enter our waterways indirectly as runoff from impervious surfaces.  When these nonpoint pollutants flow through our storm water systems and out into our rivers and lakes, they degrade the quality of our waterways.  According to the 1996 National Water Quality Inventory, a biennial summary of State surveys of water quality, approximately 40% percent of surveyed U.S. water bodies were still impaired by pollution and did not meet water quality standards. The EPA proclaimed, “13% of impaired rivers, 21% of impaired lake acres, and 45% of impaired estuaries are affected by urban/suburban storm water runoff”.  


The National Pollutant Discharge Elimination System (NPDES) Phase I was formulated in 1990 under the Clean Water Act to address this issue of polluted runoff, or nonpoint source pollution. Nonpoint source pollution is defined as pollution that comes from many different sources over a large area, and it is generated when rain or snowmelt collects impurities as it travels to a body of water.


NPDES Phase I was designed to regulate stormwater runoff discharges on construction sites that disturb five (5) or more acres of property.  Under the Phase I program the EPA additionally required operators of “medium” and “large” (populations 100,000 or greater) Municipal Separate Storm Sewer Systems, or MS4s, to implement a storm water management program.  In 1999 the United States Environmental Protection Agency (USEPA) expanded the NPDES storm water program by designating additional sources of storm water for regulation to protect water quality.  This new, expanded program is NPDES Phase II.  

The new Phase II regulations strengthen the ability of government to regulate sources of nonpoint source pollution, the leading cause of water quality degradation in the United States.  Phase II affects two classes of facilities and associated permits for  coverage on a nationwide basis: small municipalities  (MS4s) and small construction sites.  The OEPA was required to issue permits  December 8, 2002 and regulated entities were required to submit permit  applications and management plans by March 10, 2003.  The Construction Activity  Permit was renewed in 2008 and 2013 and the Small MS4 permit was renewed in 2009  and expected to renew in 2014.

Phase II generally consists of two basic permits commonly referred to as the Construction Activity Permit and the Small MS4 Permit.  The Construction Activity permit applies to ALL construction activities that disturb greater than  one (1) acre regardless of location, population or density. The Small MS4 permit applies to all small MS4s in urbanized areas, or “UA’s”, as designated by the Bureau of Census, as well as small MS4s located outside a UA serving a jurisdiction with a population of at least 10,000 people and a 
population density of at least 1,000 people per square mile.  

Whether the nonpoint source pollution is sediment runoff from a construction site or pesticide runoff from a cornfield, it impairs the quality of our waterways and thus the habitat and the resources within that habitat that many animals rely on for survival. 

For more information on NPDES Phase II and the permit process check out the Ohio EPA websites below:

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