What is a 303(d)list?

Section 303(d) of the federal Clean Water Act (and related regulations requires states to assess the condition of their waters to determine where water quality is impaired (does not fully meet standards) or threatened (is likely to violate standards in the near future).  The result of this review is the 303(d)list, which must be submitted to the EPA every other year.  Section 303(d) also requires states to prioritize and target water bodies on their list for development of water quality improvement strategies (i.e. TMDLs), and to develop such strategies for impaired and threatened waters.

What is the history of the list?

The federal Clean Water Act passed in 1972.  It was not until 1978 that the EPA started requiring states to submit 303(d) lists and TMDLs, but they provided no guidance on how to do so.  The EPA lost its first court case on this topic in 1984 and in 1991 issued their first guidance document, which was developed jointly with states.

Montana has been documenting water quality conditions in the state since the mid-1970's.  The results of these reviews have been submitted to the federal Environmental Protection Agency (EPA) on a regular basis (as part of the federally-required 305(b) reporting), but were not officially termed 303(d) lists until 1992.  Montana's 1996 and 1998 303(d) lists included about 800 waters considered to be either threatened or impaired.

Passage of HB 546 in 1997 required the DEQ to evaluate all waters on the list to determine if "sufficient credible data" was used in their listing.  The review is to be complete by October of 1999.  State law requires that any waters not meeting the test must be removed from the list and reassessed.

How can I find out if a stream or lake is on the list and for what reason?

The 1996 and 2000 versions of Montana's 303(d) list is posted on this  website.

The lists are also available from DEQ in paper format (contact DEQ's Water Quality Planning Bureau (406)444-6697.  They are lengthy (over an inch thick in paper copy), and include DEQ's assessment of what is causing the impairment and which land uses may be the major contributors.

Some streams on the list go dry...  how can there be water quality problems if there's no water?

Given the general Montana Water Quality Act goal of providing a "comprehensive program for the prevention, abatement, and control of water pollution," even streams that go dry are subject to listing on the state's 303(d) list.  According to DEQ staff, Montana's numeric water quality standards apply when water is in a stream or lake.  If the waterway is intermittent (flow may disappear at some point in the year or ephemeral (flows typically only occur during and soon after rain events), DEQ's "general prohibitions" apply, which generally prohibit placing waste where it is likely to cause pollution of state waters.

Naturally intermittent streams, when flowing, can carry sediments and other pollutants which are major contributors to water quality problems downstream.  For example, waste placed in a dry wash can be carried downstream in a future storm.  Also, DEQ staff note that ephemeral streams often contain deep pools that do not dry up except under extreme drought conditions.  These pools are safe havens for hearty aquatic life and migratory waterfowl.  Other species have evolved to withstand dry spells.  They form cysts, burrow into the soft mud, or even move into the gravel in alluvial aquifers.

If lack of year-round stream flow is human-caused and lack of flow results in a designated use (e.g. support of aquatic life not being fully supported, the stream may be placed on the 303(d) list due to problems related to "flow alterations".

What's the difference between being listed as
impaired vs threatened?

Impaired water bodies do not fully meet water quality standards (i.e. do not fully support their designated uses), even though required technology-based controls and Best Management Practices may already be in place.

Threatened water bodies currently fully support their designated uses, but:

  1. There is a new or proposed pollution source in the watershed that is not subject to the requirements of a discharge permit, the Montana water quality nondegradation law, or reasonable soil, land, and water conservation practices, or
  2. There is a documented declining trend in water quality.

Will one bad sample put a water on the list?

For most uses, not likely.  In some drinking water cases, maybe. For decisions related to most non-drinking water uses, one bad sample wouldn't put a water on the list unless the sample shows a toxic chemical at a level way beyond health standards.  Even then one bad sample would likely be investigated to see if it was the result of laboratory error, and then be re-sampled to confirm the finding.

DEQ staff have developed a preliminary decision making framework for evaluating whether certain levels and combinations of information are sufficient to determine whether or not water quality standards are being met (and designated uses fully supported).  Their criteria generally require that two of three types of information (i.e. chemical, physical, or biological) be provided, and the information for each type generally requires more than one sample.  There is room for situations where overwhelming evidence allows the use of only one category of information, but these situations are rare.

In some drinking water cases, however, if one water sample was taken and analyzed according to DEQ's sampling criteria, and the result shows an exceedence of drinking water standards, and that sample is the only information DEQ has upon which to draw a conclusion, they would likely determine the water is not supportive of drinking water uses.