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Connecticut Department of Energy and Environmental Protection Exit

Water Quality Standards

• Water Quality Standards Regulations: Connecticut

• Water Quality Standards and Classifications

Designated Aquatic Life Uses
Habitat for fish and other aquatic life and wildlife

Biological Criteria
__X__ Narrative, with quantitative implementation procedures or translators
_____ Numeric
_____ No criteria

Section 22a-426-5. Biological condition gradient model
(a) The Biological Condition Gradient Model is a model that describes how ecological attributes change in response to increasing levels of stressors. In accordance with the Biological Condition Gradient Model, as the level of stress gets progressively greater, the biological communities, which start out in a natural condition, begin to change as they respond to the stress.
(b) The ecological attribute changes are categorized into tiers, as follows:
(1) Tier 1 - Native condition is such that the native structural, functional and taxonomic integrity is preserved; ecosystem function is preserved within the range of natural variability.
(2) Tier 2 - Minimal changes in the structure of the biotic community and minimal changes in ecosystem function are such that virtually all native taxa are maintained with
some changes in biomass or abundance; ecosystem functions are fully maintained within the range of natural variability.
(3) Tier 3 - Evident changes in structure of the biotic community and minimal changes in ecosystem function due to loss of some sensitive-rare taxa; shifts in relative abundance of taxa but sensitive-ubiquitous taxa are common and abundant; ecosystem functions are fully maintained through redundant attributes of the system.
(4) Tier 4 - Moderate changes in structure of the biotic community with minimal changes in ecosystem function due to replacement of some sensitive-ubiquitous taxa by more tolerant taxa, but reproducing populations of some sensitive taxa are maintained; overall balanced distribution of all expected major groups; ecosystem functions largely maintained through redundant attributes.
(5) Tier 5 - Major changes in structure of the biotic community and moderate changes in ecosystem function are such that the sensitive taxa are markedly diminished; conspicuously unbalanced distribution of major groups from that expected; organism condition shows signs of physiological stress; ecosystem function shows reduced complexity and redundancy; increased build-up or export of unused materials.
(6) Tier 6 - Severe changes in structure of the biotic community and major loss of ecosystem function are such that there are extreme changes in structure; wholesale changes in taxonomic composition; extreme alterations from normal densities and distributions; organism condition is often poor; ecosystem functions are severely altered.
(Effective October 10, 2013)

Antidegradation Policy
Antidegradation policy (PDF) (59 pp, 742 K)

Section 22a-426-8 (a) (2)“Surface waters with an existing quality better than the criteria established in the Connecticut Water Quality Standards shall be maintained at their existing high quality, unless the Commissioner finds, after adequate opportunity for intergovernmental review and public participation, that allowing lower water quality is necessary to accommodate overriding economic or social benefits to the state and to the area in which the surface water is located that are determined by the Commissioner to exist after an analysis of the factors listed in subdivision (1) of subsection (g) of this section, and that existing and designated uses will be fully protected. Factors that may be given consideration when identifying High Quality Waters include but are not limited to the current biological condition, fisheries resources and recreational uses.”

Biological Assessment

What biological assemblages are used in the bioassessment program?
Benthic macroinvertebrates, fish, and periphyton

Are bioassessments used to support 303(d) listings?
Yes. Listing methodology: Table 1-3, page 15 of IWQR (PDF) (61 pp, 3 MB)

How are assemblages used to make impairment decisions?
Biological assemblages are independently applied, along with other concurrent data (e.g. chemical monitoring) and then a weight of evidence approach is used.

Other uses of biocriteria or bioassessment within the water quality program:
​Refining ALU, TMDL development and assessment, non-point source assessments, BMP evaluation, and 305(b) surface water condition assessments

Biological data, especially fish community information, is being incorporated into Stream flow classifications; Refer to: Connecticut Stream Flow Standards and Regulations (PDF) (22 pp, 373 K)

Technical Support Information and Documents:

Reference condition:
​Reference condition is typically defined by landuse, and chemical constituents concentration (e.g. chloride < 5 mg/L) if data are available. Depending on the application, other anthropogenic stressors (i.e. dams, water withdrawal, fish stocking) are also considered.

Technical reference material:
Becker, M.E., T.J. Becker, and C.J. Bellucci. (2018) Diatom tolerance metrics to identify total phosphorus as candidate cause of aquatic life impairment in Connecticut, USA freshwater streams. Ecological Indicators 92:638-646.
Bellucci, C J, M Becker, M Beauchene. 2011. Characteristics of macroinvertebrate and fish communities from 30 least disturbed small streams in Connecticut. Northeastern Naturalist 18:411-444.
Gerritsen J, Jessup B (2007) Calibration of the biological condition gradient for high gradient streams of Connecticut. Report prepared for US EPA Office of Science and Technology and the Connecticut Department of Environmental Protection. TetraTech, Maryland.
Stamp, J, Gerritsen J (2013) A biological condition gradient assessment model for stream fish communities of Connecticut-Final Report. Report prepared for US EPA Office of Science and Technology and the Connecticut Department of Environmental Protection. TetraTech, Maryland.

Biocriteria:
Development of biocriteria involves the collection and interpretation of biological data –e.g. benthic macroinvertebrates, fish, and periphyton. During this process entities typically use biological metrics (usually aggregated into a multimetric index) and/or multivariate analysis to assess whether a waterbody is meeting its designated aquatic life use(s). The reference materials included below include standard operation procedures used in data collection, compilation, technical approaches used to develop biocriteria as well as its implementation procedures.

Technical reference material:
Numeric values are more detailed in CALM for assessments

Supporting Materials:
Bellucci, C, ME Becker, M Beauchene, L. Dunbar (2013) Classifying the health of Connecticut streams using benthic macroinvertebrates with implications for water management. Environmental Management 51:1274-1283.
Gerritsen J, Jessup B (2007) Calibration of the biological condition gradient for high gradient streams of Connecticut. Report prepared for US EPA Office of Science and Technology and the Connecticut Department of Environmental Protection. TetraTech, Maryland.
Kanno Y, Vokoun JC, Beauchene M (2009)Development of dual fishmultimetric indices of biological condition for streams with characteristic thermal gradients and low species richness. Ecol Indic 10:565–571.
Stamp, J, Gerritsen J (2013) A biological condition gradient assessment model for stream fish communities of Connecticut-Final Report. Report prepared for US EPA Office of Science and Technology and the Connecticut Department of Environmental Protection. TetraTech, Maryland.

Stressor identification/causal analysis approach:
​Biological monitoring is used to bracket known stressors to determine the most likely cause of impairment. Conceptual model diagrams are a big component of setting up the sampling design and eliminating potential stressors.

Technical reference material:
Bellucci C, G Hoffman, and S Cormier (2010) An Iterative Approach for Identifying the Causes of Reduced Benthic Macroinvertebrate Diversity in the Willimantic River, Connecticut. U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati, OH. EPA 600-R-08-144.

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