BOARD01494

• Board Meeting Date: 9/21/1998
• Description: Federal "Clean Water Action Plan" and EPA's Advance Notice of Proposed Rule Making
• Board Meetings - Doc Type: Memo

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&EPA

Fact Sheet

Criteria - 40 CFR 131.11

Water quality criteria are levels of individual pollutants or water quality characteristics, or
descriptions of conditions of a water body that, if met, will generally protect the designated uses
of the water. EP A, under section 304(a) of the Act, periodically publishes recommendations
(guidance) for use by States and Tribes to set water quality criteria.

There are three principal categories of water quality criteria, and within these broad categories,
there are different types of criteria:

. criteria to protect human health (chemical-specific and miCrobiological criteria)

. criteria to protect aquatic life (chemical-specific, toxicity, biological, sediment, and physical
criteria such as habitat and flow balance)

.

. criteria to protect wildlife (chemical-specific criteria)

Many criteria are developed to apply generally. They may also be developed or adapted to apply
site-specifically. CW A section 303(a)-(c) requires States authorized Tribes to evaluate the need
for water quality criteria to protect designated uses and then to adopt water quality criteria (either
EPA's or its own) sufficient to protect designated uses of State or Tribal waters. Economic and
technological factors (e.g., the ability of analytical techniques to detect the pollutant and
treatment cost considerations) may not be used to justify adoption of criteria that do not protect
the designated use. Criteria may be expressed in either narrative or numeric forms.

Narrative criteria are descriptions of conditions necessary for the water body to attain its
designated use. Often expressed as "free from" certain characteristics, narrative criteria can be
the basis for controlling nuisance conditions, e.g. floating debris or objectionable deposits.
Narrative criteria are often the basis for limiting toxicity in discharges. States and Tribes
establish narrative criteria where numeric criteria cannot be established or to supplement numeric
criteria under 40 CFR 131.11 (b )(2). When a water body is classified for more than one use,
criteria necessary to protect the most sensitive use must be applied to the water body (40 CFR
131.11 (a)).

Numeric criteria are values expressed as levels, concentrations, toxicity units, or other numbers
deemed necessary to protect designated uses. Water quality criteria developed under Section
304(a) are based solely on data and scientific judgments on the relationship between pollutant
. concentrations and environmental and human health effects. EPA criteria under section 304(a)