Technical Support Fact Sheet
410 Severn Avenue, Suite 109
Annapolis, Maryland 21403
voice 410-267-5700 • toll free 800-YOUR-BAY • www.chesapeakebay.net
1 0/2003
Guiding Chesapeake Bay Water Quality Restoration:
Conducting Use Attainability Analyses (UAAs)
Background
To improve water quality for the living resources of the Chesapeake Bay, the Chesapeake Bay Program
partners-the U.S. Environmental Protection Agency (EPA), the states of Maryland, Virginia, Pennsylvania, New
York, Delaware and West Virginia and the District of Columbia-have initiated a process to develop new water
quality standards for the Bay and its tidal rivers. Maryland, Virginia, Delaware and the District of Columbia have
committed to adopt their new state
water quality standards by 2005.
A water quality standard defines the
water quality goals of a water body, or
portion thereof, in part, by designating
the use or uses to be made of the
water and by setting criteria necessary
to protect the uses. As part of the
commitment to restore Chesapeake
Bay water quality, the EPA, in close
collaboration with its watershed
partners, published new Chesapeake
Bay regional water quality criteria for
dissolved oxygen, water clarity and
chlorophyll a in April 2003.
In developing new criteria, the
partners also determined that the
current underlying tidal-water
designated uses must be refined to
better reflect desired Chesapeake Bay
water quality conditions. Current
designated uses applied to the waters
of the Chesapeake and its tidal
tributaries do not fully reflect natural
conditions and are too broad in their
definition of 'use' to support the
adoption of a more habitat-specific
aquatic life criteria. Furthermore, they
change across jurisdictional borders in
the same body of water. Therefore,
the Chesapeake Bay Program
partners have recommended that the following five refined aquatic life designated uses be applied to the appropriate
habitats in the Chesapeake Bay and its tidal tributaries:
Migratory fish spawning and nursery;
Open-water fish and shellfish;
Deep-water seasonal fish and shellfish;
Deep-channel seasonal refuge; and
Shallow-water bay grass.
Chesapeake Bay Program
A Watershed Partnership
Conceptual illustration of the five recommended Chesapeake Bay
tidal-water designated uses.
A. Cross-Section of Chesapeake Bay or Tidal Tributary
Shallow-Water
Bay Gtb3s Uae
Open-Water
Fish andShelHish Use
Deep-Water
Seesinal Fish and
a-elhish Use
Deep-Channel
Seasonal Fteluge Use
B. Oblique View of Ihe Chesapeake Bay and its Tidal Tributaries
Migratory Fish
Spawnrg and
i Nursery Use
Open-Water
Fish and ShaHish Use
Dee p-Wa ter
Seasonal Fish and
Deep-Channel
Seasonal Fleluge Use
Shellfish Use
The Chesapeake Bay Program is restoring the Bay through a partnership among the U.S. Environmental Protection Agency representing the federal
government, the State of Maryland, the Commonwealth of Pennsylvania, the Commonwealth of Virginia, the District of Columbia, the Chesapeake Bay
Commission, and participating citizen advisory groups.

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Conducting Use Attainability Analyses
Page 2
Use Attainability Analysis Defined
As part of their water quality standards development process, the states and the District of Columbia will conduct
use attainability analyses (UAA). A UAA is a scientific study to assess the factors affecting the attainment of a use.
The factors may be of a physical, chemical, biological and/or economic nature. The federal water quality standards
regulation requires states to undertake UAAs to remove or establish a subcategory of a designated use that requires
less stringent water quality criteria. The evaluations conducted in a UAA determine the attainable uses for a water
body.
Evaluating Physical, Chemical and Biological Factors
The physical, chemical and biological factors affecting the attainment of a use are evaluated through a water body
survey and assessment. Such surveys and assessments conducted by a state should be sufficiently detailed to
answer the following questions:
What are the aquatic use(s) currently being achieved in the water body?
What are the causes of any impairment of the aquatic uses?
What are the aquatic use(s) that can be attained based on the physical, chemical and biological
characteristics of the water body?
When conducting surveys and assessments as part of a UAA, the EPA encourages states to use existing data to
the greatest possible extent. Also, there are many analytical methods available that can be used by states as part
of the survey and assessment process. States have the discretion to determine the appropriate parameters and
methodologies as long as they are scientifically and technically supportable.
Summary of Typical Factors Used in Conducting a Water Body Survey and Assessment
Physical Factors
Chemical Factors
Bioloaical Factors
instream characteristics
dissolved oxygen
biological inventory
-size (mean width./depth)

-fish
-flow/velocity
toxicants
-macroinvertebrates
-annual hydrology

-microinvertebrates
-total volume
suspended solids
-phytoplankton
-reaeration rates

-periphyton
-gradient/pools/riffles
nutrients
-macrophytes
-temperature
-nitrogen

-sedimentation
-phosphorus
biological potential analysis
-channel modifications

-diversity indices
-channel stability
sediment oxygen demand
-HSI models

-tissue analyses
substrate composition and
salinity
-recovery index
characteristics
-intolerant species analysis

hardness
-omnivore-carnivore analysis
channel debris



alkalinity
pH
biological potential analysis
sludge deposits
-reference reach comparison
riparian characteristics
dissolved solids

downstream characteristics


The Chesapeake Bay Program is restoring the Bay through a partnership among the U.S. Environmental Protection Agency representing the federal
government, the State of Maryland, the Commonwealth of Pennsylvania, the Commonwealth of Virginia, the District of Columbia, the Chesapeake Bay
Commission, and participating citizen advisory groups.

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Conducting Use Attainability Analyses
Page 3
Physical Factors
Physical habitat plays an important role in the overall aquatic ecosystem and impacts the types and number of
species present in a particular body of water. During the survey and assessment process, physical parameters of a
water body are examined to identify factors that impair the propagation and protection of aquatic life and to
determine what uses could be obtained in the water body given such limitations. In general, physical parameters
such as flow, temperature, water depth, velocity, substrate, reaeration rates and other factors are used to preclude
attainment of the designated use. Once any physical limitations have been identified, then a careful consideration of
the ability to restore the physical integrity of the water is made. Such considerations may include whether it would
cause more environmental damage to correct the problem than to leave the water as is, or whether physical
impediments such as dams can be operated or modified in a way that would allow attainment of the use.
Chemical Evaluations
The chemical evaluation conducted during the survey and assessment process entails examining the chemical
characteristics of a water body to determine why a designated use is not being met and to determine the potential of
a particular species to survive in the water body if the concentrations of particular chemicals were modified. The
type of parameters considered are determined by a state, but examples of the chemical factors that might be
considered during this phase of the process include dissolved oxygen levels, suspended solids, salinity, alkalinity
and nutrients. As part of the evaluation of water chemistry composition, a natural background evaluation is useful in
determining the relative contribution of natural background contaminants to the water body. Determination that the
natural background concentration of a pollutant is adversely impacting the survival of a species is a legitimate factor
that effectively prevents a designated use from being met.
Biological Evaluations
In evaluating what aquatic life protection uses are attainable, the biology of the water body should be evaluated.
The EPA encourages states to:
provide a more precise statement of which species exist in the water body and should be protected;
determine the biological health of the water body; and
determine the species that could potentially exist in the water body if the physical and chemical factors
impairing a use were corrected.
Before any field work is conducted, existing data should be collected. The EPA can provide data from intensive
monitoring surveys and special studies. Data, especially for fish, may be available from state fish and game
departments, or through environmental impact statements, permit reviews, surveys and academic or other studies.
Economic Factors
When evaluating use attainability, states may consider whether controls more stringent than those required by
sections 301 (b)(1 )(A) and (B) and 306 of the Clean Water Act would result in substantial and widespread economic
and social impacts. Although the EPA is responsible for approving a state's water quality standards, the state is
responsible for interpreting the circumstances of each case and determining where there are substantial and
widespread economic and social impacts, or where important social and economic development would be
inappropriately precluded. Each analysis of economic impacts must demonstrate:
that the polluting entity, whether privately or publicly owned, would face substantial financial impacts due to
the costs of the necessary pollution controls and
that the affected community would bear significant adverse impacts if the entity is required to meet existing
or proposed water quality standards.
For public-sector entities, substantial impacts include financial impacts on the community, taking into consideration
current socioeconomic conditions. Wdespread, on the other hand, refers to changes in the community's
socioeconomic conditions. By contrast, for private-sector entities, substantial impacts refer to financial impacts and
widespread impacts refer to socioeconomic impacts on the surrounding community.
The Chesapeake Bay Program is restoring the Bay through a partnership among the U.S. Environmental Protection Agency representing the federal
government, the State of Maryland, the Commonwealth of Pennsylvania, the Commonwealth of Virginia, the District of Columbia, the Chesapeake Bay
Commission, and participating citizen advisory groups.

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Conducting Use Attainability Analyses
Page 4
UAA Resources for Chesapeake Bay Program Watershed Partners
Technical Support Document
While a UAA is conducted by a state in the course of adopting new or revised water quality standards, the
Chesapeake Bay Program developed a document entitled Technical Support Document for Identification of
Chesapeake Bay Designated Uses and Attainability (Technical Support Document) that provides information on a
watershed-wide scale to promote coordination and consistency across all jurisdictions. The Technical Support
Document provides guidance for refining current designated uses-the five uses listed on the first page of this fact
sheet-and it documents that two factors, natural conditions and human-caused conditions that cannot be remedied,
are likely to be sufficient justification for showing why the current designated uses cannot be met, particularly in the
deeper waters of the Chesapeake Bay.
The Technical Support Document is a compilation of basinwide guidance on UAA-related analyses and was
assembled collaboratively by the relevant jurisdictions; it does not represent a regulation or a set of mandatory
requirements. The EPA encourages jurisdictions to use the information in the Technical Support Document and,
when appropriate, to perform additional analyses relevant to their respective water quality standards development
process.
The Technical Support Document can be found online at: www.chesapeakebav.net/uaasupport.htm. Hard copies
can be obtained by contacting Lois Gartner at 410-267-5748.
Economic Analyses
As a companion piece to the Technical Support Document, the EPA developed a document entitled Economic
Analyses of Nutrient and Sediment Reduction Actions to Restore Chesapeake Bay Water Quality (Economic
Analyses). The Economic Analyses provide states with the results of analyses conducted by the Chesapeake Bay
Program related to controls to meet the revised water quality criteria and uses. Part I of the Economic Analyses
provides estimates of the potential control costs associated with three modeling scenarios of nutrient reduction
measures. Part II describes economic modeling of the potential impacts of these control costs in the Chesapeake
Bay Region. Part III documents a screening-level analysis of potential impacts, also based on the costs of the tier
scenarios. Although this information may be useful to states in conducting their own UAAs, the Chesapeake Bay
Program did not use these analyses to delineate boundaries for the refined designated uses.
The Economic Analyses can be found online at: www.chesapeakebav.net/ecoanalvses.htm.
Other Resources
Water Quality Standards Handbook (Second Edition) available online at:
www.epa.gov/waterscience/standards/handbook.
Interim Economic Guidance for Water Quality Standards-Workbook available online at:
www.epa.gov/waterscience/econ/.
Technical Support Manual: Waterbody Surveys and Assessments for Conducting Use Attainability Analyses,
Volume I and Technical Support Manual: Estuarine Systems, Volume II both available online at:
www.epa.gov/waterscience/librarv/wgstandards/uaavol123.pdf.
The Chesapeake Bay Program is restoring the Bay through a partnership among the U.S. Environmental Protection Agency representing the federal
government, the State of Maryland, the Commonwealth of Pennsylvania, the Commonwealth of Virginia, the District of Columbia, the Chesapeake Bay
Commission, and participating citizen advisory groups.

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