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Water: Module 5

Basic Course: Key Concepts (Module 5.i)

A Variance: Temporary Modification to Water Quality Standards

Module 5. Water Quality Flexibilities

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Situations can arise in which an individual or group of dischargers determine they cannot immediately meet their permit limits but are uncertain if they can ultimately meet them. For example, the discharger may want to more fully assess its ability to operate within a State/Tribe's water quality standards before investing in expensive controls. Or, the discharger(s) may be anticipating a less-expensive control technology becoming available in the near term.

For such situations, the regulations afford the flexibility to adopt a variance that temporarily modifies the water quailty standards to the highest use and criteria that are currently available. This varied use and criteria then serve as the basis for the permit limits that a disharger can meet for the duration of the variance.

Key Point. A water quality variance is a temporary change in a State/Tribe's water quality standards and its relevant criteria, usually regarding a specific pollutant. That is, the underlying standards remain in place. In granting the variance, the State/Tribe must follow its established variance policies and the variance is then subject to public and EPA review. Variances should be reviewed on a triennial basis along with the rest of the State/Tribe’s water quality standards.
Concepts Applied. Read how the flexibility to issue variances was written into the Tribal water quality standards for Pueblo of Acoma in New Mexico (PDF) (55 pp., 2.4 MB, About PDF) (See p. 2-23 (variances) and p. 2-24 (short-term exceedances).)

For informational purposes only–Not official statements of EPA policy.

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