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Indiana Department of Environmental Management

IDEM > Permitting > Water Permits > Wastewater Permits > National Pollution Discharge Elimination System (NPDES) Overview National Pollution Discharge Elimination System (NPDES) Overview

The State of Indiana's efforts to control the direct discharge of pollutants to waters of the State were inaugurated by the passage of the Stream Pollution Control Law of 1943. The vehicle currently used to control direct discharges to waters of the State is the NPDES (National Pollutant Discharge Elimination System) Permit Program. This was made possible by the passage of the Federal Water Pollution Control Act Amendments of 1972 (also referred to as the Clean Water Act). These permits place limits on the amount of pollutants that may be discharged to waters of the State by each discharger. These limits are set at levels protective of both the aquatic life in the waters which receive the discharge and protective of human health.

The State of Indiana was granted primacy from U.S. EPA to issue these permits on January 1, 1975 through implementation of a memorandum of agreement. From 1975 to 1986 the State managed the NPDES program through the Stream Pollution Control Board with staff provided by the Indiana State Board of Health (ISBH), Division of Water Pollution Control. On April 1, 1986, the Department of Environmental Management came into existence and responsibility of the NPDES program was transferred to the Office of Water Quality (OWQ).

The only significant difference between the two programs is that under the Stream Pollution Control Board the permits were issued by the Technical Secretary; IDEM issues permits through the Commissioner who has delegated the authority to an Assistant Commissioner. Existing staff were transferred from ISBH to IDEM at this time and on June 1, 1986, the IDEM employees were moved from 1330 West Michigan to 105 South Meridian with a satellite office for field personnel located at Bradbury Street. (Currently, field staff are housed at a satellite office located on Shadeland Avenue). The responsibilities at IDEM were increased at this time with the inclusion of semi-public wastewater permits and public water supply permits. Prior to IDEM, semi-publics were handled by ISBH Division of Sanitary Engineering and Public Water Supply by ISBH Water Supply Division.

U.S. EPA, Region 5, has oversight authority for the NPDES permits program. Under terms of the memorandum of agreement, Region 5 has the right to comment on all draft Major discharger permits.

In addition to the NPDES permitting program, OWQ's Permitting Branch operates a pretreatment program which serves an oversight role for municipalities that operate their own municipal pretreatment programs. Further, the NPDES program permits discharges of process wastewater to municipal sewage treatment plants by Industrial Waste Pretreatment (IWP) permits program. Additionally, the Permitting Branch regulates storm water discharges and discharges from combined sewer overflow (CSO) outfalls in its Wet Weather Section. Land Application of waste treatment plant sludge is no longer a part of the Office of Water Quality. It is now a part of the Office of Land Quality.

The purpose of the NPDES permit is to control the point source discharge of pollutants into the waters of the State such that the quality of the water of the State is maintained in accordance with the standards contained in 327 IAC 2. The NPDES permit requirements must ensure that, at a minimum, any new or existing point source must comply with technology-based treatment requirements that are contained in 327 IAC 5-5-2. According to 327 IAC 5-2-2, "Any discharge of pollutants into waters of the State as a point source discharge, except for exclusions made in 327 IAC 5-2-4, is prohibited unless in conformity with a valid NPDES permit obtained prior to discharge." This is the most basic principal of the NPDES permit program.

The majority of NPDES permits have existed since 1974. This means that most of the permit writing is for permit renewals. Approximately 10% of each year's workload is attributed to new permits, modifications and requests for estimated limits. NPDES permits are designed to be re-issued every five years but are administratively extended in full force and effect indefinitely if the permittee applied for a renewal before the current permit expires.

There are several different types of permits that are issued in the NPDES permitting program. They are as follows:

  1. Municipal, Semi-Public or State (sanitary-type discharger)
    1. Major Municipals - A facility owned by a municipality with a design flow of 1 million gallons per day (mgd) or greater (Cities, Towns, Regional Sewer Districts)
    2. Minor Municipals - Any municipally owned facility with a design flow of less than 1 mgd (Cities, Towns, Regional Sewer Districts)
    3. Semipublics - Any facility not municipally, State or Federally owned (i.e.- mobile home parks, schools, restaurants, etc.)
    4. State Owned - A facility owned or managed by a State agency (State parks, prisons, etc.)
    5. Federal - A facility owned by a federal agency (military owned installation, national park, federal penitentiary, etc.)
  2. Industrial (Wastewater generated in producing a product)
    1. Majors - Any point source discharger which is designated as such annually by an agreement between the commissioner and EPA. Classification of a discharger as a major generally involves consideration of factors relating to the significance of the discharger's impact on the environment, such as:
      1. Nature and quantity of pollutants discharged;
      2. Character and assimilative capacity of the receiving waters;
      3. Presence of toxic pollutants in the discharge;
      4. Compliance history of the discharger
    2. Minors - All dischargers which are not designated as major dischargers.
    3. Generals - The purpose of the general permit rule is to provide a streamlined NPDES permitting process for certain classes or categories of industrial point source discharges under the requirements of the applicable general permit rule rather than the requirements of an individual permit specific to a single discharge. The following is a list of the general permit rules and the industrial activities they regulate:
      1. 327 IAC 15-7 Coal mining, coal processing, and reclamation activities
      2. 327 IAC 15-8 Noncontact cooling water
      3. 327 IAC 15-9 Petroleum products terminals
      4. 327 IAC 15-10 Groundwater petroleum remediation systems
      5. 327 IAC 15-11 Hydrostatic testing of commercial pipelines
      6. 327 IAC 15-12 Sand, gravel, dimension stone or crushed stone operations
    4. Cooling Water (Water which is used to remove heat from a product or process, the water may or may not come in contact with the product)
    5. Public Water Supply (Wastewater generated from the process of removing pollutants from ground or surface water for the purpose of producing drinking water)
    6. Industrial Wastewater Pretreatment (IWP) (Processed wastewater generated by Industries that contribute to the overall wastewater received by the plant)
  3. Wet Weather
    1. Storm Water-related (Wastewater resulting from precipitation coming in contact with a substance which is either dissolved or suspended in the water)
    2. Combined Sewer Overflows (CSO) (Wastewater discharged from combined storm and sanitary sewers due to precipitation events)