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Bioassessment and Biocriteria Program Status for Vermont: Streams and Wadeable Rivers

State Program Contact

Watershed Management Division - Biomonitoring Exit

Water Quality Standards

WQS Information
The link to Vermont's WQS that are in effect for Clean Water Act purposes is provided. These are the WQS approved by EPA.
The state of Vermont provided information and links to sections of their administrative code on designated aquatic life use, biological criteria, antidegradation as well as technical support documents and information on its bioassessment and biocriteria programs. These are included for your convenience and may or may not reflect the most recently EPA approved WQS. The following links exit the site Exit

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Designated Aquatic Life Uses
There are currently three tiers of supporting ALS. The water quality standards also include a warm water/cold water designation which is used in the D.O and temperature criteria.
  • Class A is as naturally occurs
  • Class B(1): A minor change from natural condition
  • Class B(2): A moderate change from natural condition

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

Vermont currently has biocriteria to determine ALS for three narrative tiers in the VTWQS for streams; visit Vermont Water Quality Standards (PDF) (108 pp, 3 MB)

Section 29A-306(a)(1):  Class A(1) Ecological Waters

  1. Management Objectives. Waters shall be managed to achieve and maintain excellent biological integrity and aquatic biota and wildlife consistent with waters in their natural condition.
  2. Biological Criteria. Measures of biological integrity for aquatic macroinvertebrate and fish assemblages consistent with waters in their natural condition.

Section 29A-306(a)(2):  Class B(1) Waters

  1. Management Objectives. Waters shall be managed to achieve and maintain very good biological integrity.
  2. Biological Criteria. Change from the natural condition for aquatic macroinvertebrate and fish assemblages limited to minor changes in the relative proportions of taxonomic and functional components. Relative proportions of tolerant and intolerant aquatic organisms consistent with waters in their natural condition.

Section 3-04 Class A(2) and B(2) Waters

  1. Management Objectives. Waters shall be managed to achieve and maintain good biological integrity.
  2. Biological Criteria. Change from the natural condition for aquatic macroinvertebrate and fish assemblages not exceeding moderate changes in the relative proportions of taxonomic, functional, tolerant, and intolerant aquatic organisms.

Biocriteria (numeric) are currently described and protocols described; these are currently in adopted procedure by the Secretary of ANR, and were moved into rule with the most recent iteration of the Vermont WQS (Appendix G). Biocriteria have been developed for fish and macroinvertebrate communities in wadeable streams. Two Fish Indices of Biological Integrity (IBI) are described, a Cold Water IBI, and a Mixed Water IBI. Three macroinvertebrate multimetric procedures are used for high and moderate gradient (predominantly hard bottom) streams: 1- Small High Gradient (SHG) streams, 2- Moderate High Gradient (MHG) streams, and 3- Warm Water Moderate Gradient (WWMG) streams. Vermont has also developed and implemented low gradient macroinvertebrate IBI procedures for two low gradient stream types (Hybrid Low Gradient (HLG) streams, and Slow Low Gradient (SLG) streams).

Section 29A-305 Numeric Biological Indices and Aquatic Habitat Assessments

  1. In addition to other applicable provisions of these rules and other appropriate methods of evaluation, the Secretary may establish and apply numeric biological indices to determine whether there is full support of aquatic biota and aquatic habitat uses for each class of water.  In establishing numeric biological indices, the Secretary shall establish procedures that employ standard sampling and analytical methods to characterize the biological integrity of the natural condition using reference water bodies. Standardized sampling and analytical methods used to characterize the biological integrity of these communities are provided in Appendix G of these rules. Characteristic measures of biological integrity include community level parameters such as: species richness, diversity, relative abundance of tolerant and intolerant species, density, and functional group composition.
  2. In addition, the Secretary may determine whether there is full support of aquatic biota and aquatic habitat uses through other appropriate methods of evaluation, including habitat assessments.

Section 29A-105: Antidegradation Policy

  1. General. All waters shall be managed in accordance with these rules to protect, maintain, and improve water quality.
  2. Protection and Determination of Existing Uses. Existing uses of waters and the level of water quality necessary to protect those existing uses shall be maintained and protected regardless of the water’s classification. Determinations of what constitute existing uses of particular waters shall be made either during the basin planning process or on a case-by-case basis during consideration of an application. The use of waters to receive or transport discharges of waste shall not constitute an existing use for purposes of these rules. In making a determination of the existing uses to be protected and maintained under this section and all other sections of these rules, the Secretary shall consider at least the following factors:
    (1) Aquatic biota and wildlife that utilize or are present in the waters;
    (2) Habitat that supports or is capable of supporting aquatic biota, wildlife, or plant life;
    (3) The use of the waters for recreation or fishing;
    (4) The use of the water for public water source, or commercial activity that depends directly on the preservation of an existing high level of water quality; and
    (5) For factors (1) and (2) above, evidence of the use’s ecological significance in the functioning of the ecosystem or evidence of the use’s rarity.
  3. Protection and Maintenance of High Quality Waters.
    (1) Waters the existing quality of which exceeds any applicable water quality criteria provide important environmental, economic, social, and other benefits to the people of the State. Except as provided in subdivision (2) of this subsection, such waters shall be managed to maintain and protect the higher water quality and minimize risk to existing and designated uses. In all cases, the level of water quality necessary to maintain and protect all existing uses as well as applicable water quality criteria shall be maintained.
    (2) A limited reduction in the existing higher quality of such waters may be allowed only when it is shown that:
         (A)through the applicable permitting or approval process, the Secretary has provided public notice of the draft decision and an opportunity for public comment on the decision;
         (B) after an analysis of alternatives, allowing lower water quality is necessary to prevent substantial adverse economic or social impacts on the people of the State; and
          (C) there shall be achieved the highest statutory and regulatory requirements for all new or existing point sources, and all cost effective and reasonable best management practices for nonpoint source control, consistent with state law.
    (3) The analysis of alternatives required under subdivision (c)(2)(B) of this subsection shall evaluate a range of alternatives that would prevent or lessen the degradation associated with the proposed activity. When the analysis identifies one or more practicable alternatives, the Secretary shall only find that a lowering is necessary if one such practicable alternative is selected for implementation. For purposes of this section, “practicable” means technologically possible, able to be put into practice, and economically viable.”
    (4) To the extent any reduction in the quality of high quality waters is allowed, such reduction shall be limited to that which complies with subdivision (c)(2) of this subsection.
  4. Protection of Outstanding Resource Waters. The Secretary may under 10 V.S.A. § 1424a designate certain waters as Outstanding Resource Waters. Outstanding Resource Waters are listed in Appendix H of these rules. Where the Secretary so designates such waters for specific exceptional natural, recreational, cultural, or scenic values, their existing quality, associated with the values for which they have been designated, shall, at a minimum, be protected and maintained.​

Biological Assessment

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

Are bioassessments used to support 303(d) listings?
Yes. Listing methodology: Vermont Surface Water Assessment and Listing Methodology (PDF) (39 pp, 729 K)
Vermont DEC Monitoring and Assessment Program - Assessment and Listing webpage

How are assemblages used to make impairment decisions?
Both assemblages are applied independently, and if data is available both need to meet their respective biocriteria.

Other uses of biocriteria or bioassessment within the water quality program:
Refining ALU, TMDL development and assessment, non-point source assessments, BMP evaluation, 305(b) surface water condition assessments, probabilistic surveys and assessments, participation in regional monitoring network, and restoration goals.

Technical Support Information and Documents:

Reference condition:
Reference sites were selected based on professional judgment and selected from a large existing database. Reference sites are those streams that are considered least impaired: mostly forested, do not receive WWTF discharge; generally have an alkalinity> 5 mg/L (to protect from including acid rain influences), and conductivity < 100 µhoms (to protect against chloride and general development).

Technical reference material: 
Biocriteria for Fish and Macroinvertebrate Assemblages in Vermont Wadeable Streams and Rivers (PDF) (90 pp, 534 K) 

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:
Executive Summary: Biocriteria for Fish and Macroinvertebrate Assemblages in Vermont Wadeable Streams and Rivers - Development Phase
Biocriteria for Fish and Macroinvertebrate Assemblages in Vermont Wadeable Streams and Rivers - Development Phase
Biocriteria for Fish and Macroinvertebrate Assemblages in Vermont Wadeable Streams and Rivers - Implementation Phase

Stressor identification/causal analysis approach:
An informal process is used; however in order to list a waterbody as “impaired” a likely pollutant must be identified. This is done in several ways; and is generally based on sampling for the pollutant type that is indicated by the biological “fingerprint” of the macroinvertebrate/fish community. Biological communities with a fingerprint of low abundance/richness – water quality sampling targets likely toxic pollutants; a fingerprint of high density/richness/Bio Index/lower EPT – water quality sampling targets nutrients/ organic inputs and temperature; a fingerprint of low density/high Oligochaeta/low EPT richness - stormwater scour, scour, and/or sediment sources may be identified. 

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