Impaired waters one

The Clean Water Act requires each state to list its polluted water bodies and to set priorities for cleaning them up. Water bodies qualify for the “impaired waters list” when they are too polluted or otherwise degraded to support their designated and existing uses. The impaired waters list is also called the 303(d) list, named after the section in the Act that requires it. The states submit their lists to the U.S. Environmental Protection Agency every two years.

Defining a “threatened or impaired water”

Any water body that does not meet or is not expected to meet the state’s water quality standards after full implementation of basic permits should be considered threatened or impaired and placed on the 303(d) list. This includes waters that fail to support water body uses, fail to meet any one of their applicable criteria — whether narrative or numeric, chemical, physical or biological — and those that fail to meet antidegradation requirements (40CFR130.7(b)(3)).

For example, a water body that appears to meet all its numeric chemical criteria at all times (such as the criteria for dissolved oxygen, pH and various common pollutants) but doesn't meet its narrative biological criteria (such as maintaining a healthy habitat or biological communities sufficient to support native aquatic life and wildlife) should be listed as impaired.

If it can be proven that a particular proposed activity will violate water quality standards, any waters affected by that activity should be listed as threatened (40CFR130.7(b)(5)(ii)). Neither the cause of a water quality problem nor its solutions need to be identified for a water to be listed. For example, waters in which one or more species are in rapid decline should be listed, even if the specific reason(s) for their decline is not yet known. In fact, one of the greatest values of 303(d) listing is to trigger the analysis needed to pinpoint sources of problems.

Once identified, problems can be addressed through the development of comprehensive watershed restoration plans that define specific pollution limits, known as Total Maximum Daily Loads or “TMDLs”.