Under the NPDES Program, all facilities which discharge pollutants from any point source into waters of the
United States are required to obtain an NPDES permit. Understanding how each of the key terms ("pollutant", "point source" and "waters of the United States") have been defined and interpreted by the regulations is the key to defining the scope of the NPDES Program.
The term pollutant is defined very broadly by the NPDES regulations and litigation and includes any type of industrial,
municipal, and agricultural waste discharged into water.For regulatory purposes, pollutants have been grouped into three
general categories under the NPDES Program: conventional, toxic, and non-conventional.
There are five conventional pollutants
- BOD
- Total Suspended Solids
- Fecal Coliform Bacteria
- Oil and grease
- pH
Toxic pollutants, or priority pollutants, are those defined in Section 307(a )(1) of the CWA and include metals and manmade
organic compounds.
Non-conventional pollutants are those which do not fall under either of the above categories, and include
such parameters as ammonia, nitrogen, phosphorus, chemical oxygen demand (COD), and whole effluent toxicity (WET).
Pollutants can enter waters of the United States from a variety of pathways including agricultural, domestic, and industrial sources. For regulatory purposes these sources are generally categorized as either point sources or non-point sources. Typical point source discharges include discharges from publicly owned treatment works ( POTWs), discharges from industrial facilities, and discharges associated with urban runoff. While provisions of the NPDES Program do address certain specific types of agricultural activities (i.e. concentrated animal feeding operations), the majority of agricultural facilities are defined as non-point sources and are exempt from NPDES regulation.
Pollutant contributions to waters of the United States may come from both direct and indirect sources. Direct sources discharge wastewater directly into the receiving water body, whereas indirect sources discharge wastewater to a POTW, which in turn discharges into the receiving water body. Under the national program, NPDES permits are issued only to direct point source discharges. Industrial and commercial indirect dischargers are addressed by the National Pretreatment Program.
As indicated above, the primary focus of the NPDES permitting program is municipal and non-municipal (industrial) direct dischargers. Within these major categories of dischargers, however, there are a number of more specific types of discharges that are regulated under the NPDES Program.
A permit is typically a license for a facility to discharge a specified amount of a pollutant into a receiving water under certain conditions; however, permits may also authorize facilities to process, incinerate, landfill, or beneficially use sewage sludge. The two basic types of NPDES permits issued are individual and general permits.
An individual permit is a permit specifically tailored to an individual facility. Once a facility submits the appropriate application(s), the permitting authority develops a permit for that particular facility based on the information contained in the permit application (e.g. types of activity, nature of discharge, receiving water quality). The authority issues the permit to the facility for a specific time period (not to exceed five years) with a requirement that the facility reapply prior to the expiration date.
A general permit covers multiple facilities within a specific category. General permits may offer a cost-effective option for permitting agencies because of the large number of facilities that can be covered under a single permit. According to the NPDES regulations at 40 CFR §l22.28, general permits may be written to cover categories of point sources having common elements, such as: Storm water point sources; Facilities that involve the same or substantially similar types of operations; Facilities that discharge the same types of wastes or engage in the same types of sludge use or disposal practices; Facilities that require the same effluent limits, operating conditions, or standards for sewage sludge use or disposal; and Facilities that require the same or similar monitoring.
General permits, however, may only be issued to dischargers within a specific geographical area such as city, county, or state political boundaries; designated planning areas; sewer districts or sewer authorities; state highway systems; standard metropolitan statistical areas; or urbanized areas. By issuing general permits, the permitting authority allocates resources in a more efficient manner to provide more timely permit coverage. For example, a large number of facilities that have certain elements in common may be covered under a general permit without expending the time and money necessary to issue an individual permit to each of these facilities. In addition, using a general permit ensures consistency of permit conditions for similar facilities.
All NPDES permits, at a minimum, consist of five general sections:
- Cover Page - Typically contains the name and location of the permittee, a statement authorizing the discharge, and the specific locations for which a discharge is authorized.
- Effluent Limits - The primary mechanism for controlling discharges of pollutants to receiving waters. Permit writers spend a majority of their time deriving appropriate effluent limits based on applicable technology-based and water quality-based standards.
- Monitoring and Reporting Requirements - Used to characterize waste streams and receiving waters, evaluate wastewater treatment efficiency, and determine compliance with permit conditions.
- Special Conditions - Conditions developed to supplement effluent limit guidelines. Examples include:
- best management practices (BMPs);
- additional monitoring activities;
- ambient stream surveys and;
- toxicity reduction evaluations (TREs).
- Standard Conditions - Preestablished conditions that apply to all NPDES permits and delineate the legal, administrative, and procedural requirements of the permit.
Every permit contains these five basic sections, but the contents of sections will vary depending on whether the permit is issued to a municipal or industrial facility and whether the permit will be issued to an individual facility or to multiple dischargers (i.e. a general permit).
