Adopt Numeric Biological Criteria
EPA recommends that states and tribes adopt biological criteria
into water quality standards that will provide a quantitative basis
for assessing attainment of specific designated aquatic life uses.
Technical guidance on the development of biological criteria for
specific surface water types (streams
and small rivers; lakes
and reservoirs; and estuaries and near coastal
waters) have been published. Guidance for wetlands
is being developed by EPA in conjunction with Federal, state, and
academic scientists. The Agency recommends that, at a minimum, states
adopt biological criteria for specific waterbody types after publication
of technical guidance for those waters.
EPA recommends that adoption of a numeric biological criteria into
water quality standards should not occur before the state or tribe
has:
- Confidence in the science supporting the criteria
- Experience with implementation
- Engaged stakeholders and the public so they understand what
biological criteria are and how they will be applied.
Realistically, a State or Tribe may not be ready to adopt a numeric
biological criteria for many years. For example, the State of Ohio
initiated development of their numeric biological criteria for streams
and rivers in early 1980's. Numeric biological criteria were adopted
in State standards in 1990 (Yoder and Rankin, 1995). Maine
initiated development of biological criteria for streams and rivers
in the 1980's and is undergoing rulemaking to adopt numeric biological
criteria into their water quality standards in 1999. EPA recommends
that states or tribes consider adopting an interim narrative statement
that describes specific designated aquatic life uses and reference
technical procedures while developing numeric criteria. This
interim step should result in the quantitative translation of a
state's or tribe's designated aquatic life use for a specific waterbody
and further supplement the narrative biocriteria.
Steps in adopting numeric biological criteria:
- Establish confidence in the science supporting the biocriteria
- Gain experience with implementation
- Engage stakeholders and the public so that they understand what
biocriteria are and how they will be applied
- Consider an interim step: adopt a narrative statement
that describes specific designated aquatic life uses and references
technical procedures or indices that translate the narrative statement
into quantitative measurements
- Refine methods to reflect advances in science and technology
- Build a comprehensive bioassessment data base
- Test and validate metrics, or indices, to ensure they are reliable
indicators of human disturbance and are able to discern between
changes due to natural variability and human activity
- Adopt numeric biocriteria for specific waterbody types sequentially
into water quality standards as EPA publishes technical guidance
for those waters
Adoption of numeric or statistically equivalent biological criteria
into water quality standards means that numeric values for the biological
criteria and/or the standardized technical procedures for deriving
numeric biological criteria are directly incorporated into a state
or tribe's water quality standards.
Examples - Ohio and Maine Adopt Numeric Biocriteria
The state of Ohio
has adopted into water quality standards numeric biological criteria
for streams that is consistent with EPA's Biological
Criteria: Technical Guidance for Streams and Small Rivers
(1996). Ohio's biological criteria are based on regional reference
conditions and utilizes a multi-metric approach. Numeric biological
criteria for different ecoregions have been adopted into Ohio's
water quality standards.
The state of Maine is in the process of adopting numeric biological
criteria into their water quality standards. Maine has utilized
both multi-metric and multi-variant
procedures in developing their biological criteria.
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