«*
United States Environmental Protection Agency
Office of Water
Office of Research and Development
EPA-822-R-06-001
Mav 2006
FRAMEWORK FOR DEVELOPING
SUSPENDED AND BEDDED SEDIMENTS (SABS)
WATER QUALITY CRITERIA
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EPA-822-R-06-001
May 2006
Framework for Developing Suspended
and Bedded Sediments (SABS) Water
Quality Criteria
Office of Water (OW)
Office of Science and Technology (OST)
Health and Ecological Criteria Division (HECD)
Ecological and Health Process Branch (EHPB)
Washington, DC
Office of Research and Development (ORD)
National Center for Environmental Assessment (NCEA)
Washington, DC
National Exposure Research Laboratory (NERL)
Cincinnati, OH
National Health and Environmental Effects Research Laboratory (NHEERL)
Research Triangle Park, NC
National Risk Management Research Laboratory (NRMRL)
Cincinnati, OH
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TABLE OF CONTENTS
List of Tables iv
List of Figures v
Note to Reader/Disclaimer vi
List of Acronyms vii
Acknowledgments ix
Executive Summary xi
I. Introduction 1
LA. Purpose of This Document 1
IB. The Need for SABS Criteria 2
I.B.I. Suspended and Bedded Sediments (SABS) 3
I.B.2. Summary of the Ecological Effects of SABS 4
IB.3. State Needs Survey 6
IB .4. Application of this Framework for Developing Water Quality
Criteria and Standards 7
IB.5. U.S. EPA-OW/OST Standards and Criteria Strategy 8
1C. Current Water Quality Criteria Related to SABS 9
I.C.I. Existing/Current U.S. EPA Criteria 9
I.C.2. State Criteria 9
ID. Recommendations of the U.S. EPA Science Advisory Board 10
II. Programmatic Elements of SABS Criteria Development 13
II. A. Possible Uses of this Framework 13
II.B. Resources for Framework Implementation 13
II. C. Integration of the SABS Framework with Existing State Programs 14
II.D. Implementation of SABS Criteria and Standards 15
II.D.l. Management Options 17
II.D.2. Evaluation 19
III. Technical Elements of SABS Criteria Development 21
III. A. Need for a Technical Discussion in This Framework 21
III.B. Process for SABS Criteria Development 21
III.B. 1. Step 1 Review Current Designated Uses and Criteria for a Set
of Waterbodies 23
III.B.2. Step 2 Describe SABS Effects on the Waterbodies'
Designated Uses 25
III.B.3. Step 3 Select Specific SABS & Response Indicators 25
III.B.4. Step 4 Define Potential Ranges in Value of SABS and
Response Indicators 28
III.B.5. Step 5 Identify a Response Indicator Value that Protects the
Designated Use 29
III.B.6. Step 6 Analyze and Characterize SABS/Response Associations 30
III.B.7. Step 7 Explain Decisions that Justify Criteria Selection 31
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III.C. Cross-Cutting Concepts 32
III.C.I. Classification of Waterbodies 32
III.C.2. Indicators - Exposure and Response Measurements 34
III.C.3. Integration and Synthesis of Multiple Methods 37
HID. Methods Applicable within the Framework 37
III.D.I. Measurements of SABS; Applicable in Step 3 of the Framework 40
III.D.2. Waterbody Classification; Applicable in Step 4 of the Framework 46
III.D.3. Associating Suspended and Bedded Sediments with Response 52
III.E. Hypothetical Examples of the Synthesis of Methods within the Framework 69
III.E.I Example: Northeastern Headwater Streams 73
III.E.2 Abbreviated Examples 81
REFERENCES CITED 85
APPENDICES
A Glossary of Terms 95
B Impacts of SABS 99
C State Needs Survey, Conducted in 2004 105
D SABS-Related Criteria for Surface Water Quality Ill
E Consultation with the Science Advisory Board 141
F Conceptual Models of SABS Sources and Effects 147
in
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LIST OF TABLES
1. Ranks of SABS stressors among all stressor types 2
2. Sequential elements of a SABS management program 16
3. Issues and management options for addressing SABS imbalances by
waterbody type 18
4. Suitability of SABS indicators by waterbody type 35
5. Summary of Chesapeake Bay water clarity criteria for application to
shallow-water bay grass designated use habitats 60
6. Advantages and disadvantages of methods used in SABS criteria development 70
7. Specific applications of the methods used in the hypothetical model for criteria
development and application 72
8. Decision rationale for selecting a suspended sediments criterion 78
9. Decision rationale for selecting a bedded sediments criterion 80
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LIST OF FIGURES
1. Conceptual diagram of SABS effects in estuaries 5
2. Activities and outputs of the SABS criteria development process 22
3. Seven steps of the SABS criteria development process and relationship
to four activities in Figure 2 24
4. Conceptual linkages among sources of sediment stress and aquatic ecosystem health 26
5. Suspended sediment transport curves for South Fork Forked Deer and Hatchie River ....41
6. RBS in streams of the Coast Range ecoregion of Oregon and Washington
as a function of a relative disturbance gradient in hard volcanic and soft
sedimentary geologies 45
7. RB S in streams of the Coast Range ecoregion in relation to EPT taxa richness 45
8. Turbidity in Oregon streams by reference status and erodibility 50
9. Various stream type succession scenarios 52
10. Quantile regression of the 90th percentile of intolerant invertebrate taxa over a
full range of percent fines in Minnesota streams in two groups of ecoregions 57
11. Availability of light for underwater grasses is influenced by water column and
at-the-leaf surface light attenuation 58
12. Mid-Atlantic region of the U.S. with EMAP wadeable stream sampling sites 65
13. Reverse cumulative distribution function (CDF) for percent fines in the substrate
for stream miles across entire area (all), and reverse conditional CDFs of stream
miles for impacted benthic conditions, unimpacted benthic conditions,
and reference conditions 66
14. Probability of observing EPT taxa richness <9 in mid-Atlantic streams if
specified value of percent fines in the substrate is exceeded 67
15. Conceptual model for the Northeastern headwater stream example 74
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NOTE TO READER
This document is designed as a framework with a recommended process and methods for
developing suspended and bedded sediment criteria. It is not a substitute for the CWA or U.S.
EPA's regulations; nor is it a regulation itself. The Framework does not impose legally binding
requirements on U.S. EPA, states, tribes, territories or the regulated community, and the
recommendations may not apply to some particular situations. U.S EPA, state, tribal, and
territorial decision-makers retain the discretion to adopt methods on a case-by-case basis that are
appropriate to their SABS needs. As research results and new information become available,
U.S. EPA expects to revise this document.
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LIST OF ACRONYMS
BPJ Best Professional Judgment
BMP Best Management Practice
CCC Criterion Continuous Concentration
CCDF Conditional cumulative distribution function
CDF Cumulative distribution function
CI Confidence interval
CMC Criterion Maximum Concentration
CPA Conditional probability analysis
CSREES Cooperative State Research, Education, and Extension Service
CWA Clean Water Act
DIN Dissolved inorganic nitrogen
DIP Dissolved inorganic phosphorus
EMAP U.S. EPA Environmental Monitoring and Assessment Program
U.S. EPA U.S. Environmental Protection Agency
EPT Ephemeroptera, Plecoptera, and Trichoptera metric of mayflies, stoneflies, and
caddisflies
GIS Geographic Information System
HDI Human Disturbance Index
HQ U. S. EPA Headquarters
IBI Index of Biotic Integrity
LA Load Allocations for non-point sources of pollution
LANDSAT Land Remote-Sensing Satellite
MPRSA Marine Protection, Research, and Sanctuaries Act
NAWQA USGS National Water Quality Assessment Program
NMFS NOAA National Marine Fisheries Service
NOAA National Oceanic and Atmospheric Administration
NPDES National Pollutant Discharge Elimination System
NRCS Natural Resources Conservation Service
NTU Nephelometric turbidity units
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ODEQ Oregon Department of Environmental Quality
ORD U. S. EPA Office of Research and Development
OST U.S. EPA Office of Science and Technology
OWOW U. S. EPA Office of Wetlands, Oceans, and Watersheds
PLL Percent Light-at-the-Leaf
PLW Percent Light-through-Water
RBS Relative Bed Stability
RIVPACS River Invertebrate Prediction and Classification System
RTAG Regional Technical Advisory Groups
SABS Suspended and Bedded Sediments
SAV Submerged Aquatic Vegetation
SRI Sediment Risk Index
SSC Suspended-sediment concentration
STC Sediment Transport Curves
TMDL Total Maximum Daily Load
TSS Total suspended solids
UAA Use Attainability Analysis
USDA U.S. Department of Agriculture
USFS U.S. Forest Service
USFWS U. S. Fish and Wildlife Service
USGS U.S. Geological Survey
WARSSS Watershed Assessment of River Stability and Sediment Supply
WLA Waste Load Allocation for point sources of pollution
WQC Water quality criteria
WQS Water quality standard
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ACKNOWLEDGMENTS
The U.S. EPA Science Advisory Board is acknowledged for valuable input during an October
2003 consultation. The Board consisted of scientists and technical experts that met to review and
discuss potential methods for developing water quality criteria for suspended and bedded
sediment (SABS) as described in a discussion paper prepared and presented by U.S. EPA staff.
We greatly appreciated states and staff who responded to a survey of states' needs regarding
SABS criteria. GLEC, Inc. and Tetra Tech, Inc. provided contractual support for this document.
Ben Jessup of Tetra Tech was responsible for much of the editing and document compilation. All
inquiries about this document should be directed to Robert Cantilli by e-mail at
Cantilli .Robert@epamail. epa. gov.
Primary Authors
HECD-OST-OW. HQ
Robert Cantilli*
Rick Stevens
William Swietlik
AWPD-OWOW-OW. HQ
Douglas Norton
ORD-NHEERL
Walter Berry (Narragansett)
Phil Kaufmann (Corvallis)
John Paul (Research Triangle Park)
Robert Spehar (Duluth)
ORD-NRMRL
Susan Cormier (Cincinnati)
Contributing Authors
ORD-NHEERL
Debra Taylor (Duluth)
ORD-NRMRL
ChristopherNietch (Cincinnati)
Tetra Tech, Inc.
Benjamin Jessup
Peer Review
U.S. EPA (Chesapeake Bay)
Richard Batiuk
United States Geological Survey
John Gray
Iowa Department of Natural Resources
Mary Skopec
The Center for Computational Hydroscience
and Engineering
Sam Wang
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HECD-OST-OW. HQ
George Gibson
Steve Potts
Randy Wentsel
SHPD-OST-OW. HQ
Thomas Gardner
Robert Shippen
ORD-NHEERL
Brian Hill (Duluth)
Brian Melzian (Narragansett)
Norman Rubinstein (Narragansett)
OWOW-AWPD
Katie Wolff
ORD-NCEA
Michael Griffith (Cincinnati)
Kate Schoffield (HQ)
ORD-OSP
Erik Winchester
OGC (HQ)
Peter Ford
U.S. EPA Region 4
Jim Harrison (Atlanta)
*Principal U.S. EPA contact
Technical Support and Document Review
U.S. EPA Region 8
Mitra Jha (Denver)
Jim Luey (Denver)
Ministry of Water, Land, and Air Protection,
Victoria. BC
Charles Newcombe
Idaho (DEQ)
Don Essig
Oregon Dept. of Environmental Quality
Doug Drake
GLEC. Inc.
Doug Endicott
Tetra Tech, Inc.
Abby Markowitz
Michael Barb our
ECflex Inc.
Elizabeth Evans Fryer
McNicholas High School
Claire K. Racine
Cover Photograph
Iron River, WI, (1999) near its confluence with Lake Superior
Courtesy of Anett Trebitz and John Morrice
U.S. EPA
Mid-Continent Ecology Division
Duluth, MN
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Framework for Developing SABS Water Quality Criteria U.S. EPA
EXECUTIVE SUMMARY
Suspended and bedded sediments (SABS) occur naturally in all types of waterbodies. In
appropriate amounts, sediments are essential to aquatic ecosystems (e.g., in appropriate amounts,
SABS can contribute to essential habitat for aquatic species' growth and reproduction).
However, imbalanced sediment supply has repeatedly ranked high as a major cause of
waterbody impairment (U.S. EPA 2003a). The quantity and characteristics of SABS can affect
the physical, chemical, and biological integrity of streams, lakes, rivers, estuaries, wetlands, and
coastal waters. Excessive SABS (and in some cases, insufficient SABS) can impair waterbody
uses such as navigation, recreation, and drinking water filtration. An imbalanced sediment
supply resulting from human activities impacts ecological integrity at several scales and trophic
levels.
In 2003, the U.S. EPA Office of Science and Technology (OST) within the Office of Water
(OW) issued a document titled "Strategy for water quality standards and criteria: setting
priorities to strengthen the foundation for protecting and restoring the Nation's waters" (U.S.
EPA 2003a). After a wide-ranging review of the existing water quality standards and criteria
programs within the context of all clean water programs and after extensive discussions with
Water Quality Standards stakeholders, U.S. EPA identified 10 priorities for improving the
quality of the Nation's waters. Development of SABS criteria was among the top priorities. The
U.S. EPA developed this document in support of states, tribes and territories' efforts to establish
SABS criteria that protect the ecological integrity and beneficial uses of water resources, which
are major goals of the Clean Water Act (CWA).
This Framework describes a process that states, tribes, and territories can use to develop SABS
criteria to support water quality standards and protect designated uses. The Framework is
intended to provide a consistent, defensible process for developing SABS criteria that also allows
flexibility for regional and local application and interpretation. The major chapters of the
Framework include both programmatic and technical elements. The programmatic elements
section contains discussions of resources, integration with state programs, and implementation of
criteria and standards. The technical elements section provides analytical methods for SABS
criteria development. Examples are provided to illustrate how the Framework can be applied.
Neither the process nor the methods are meant to be mandatory.
Purpose of Document
The U.S. EPA understands that states, tribes, and territories have an interest in adopting
consistent scientifically defensible SABS criteria. Towards this goal, the U.S. EPA is
providing this Framework, with possible methods that states, tribes, and territories can
use to develop SABS criteria to support water quality standards and protect designated
uses. This Framework describes what is known and what can be done relative to
developing SABS criteria and will evolve as research results and new information
become available.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
This Framework does not intend to prescribe a priority of activities that should be
undertaken for developing SABS criteria. Nor does this Framework intend to suggest that
states, tribes, territories, or other water resource managers need to change their existing
priorities (e.g., switching priorities from one program area to SABS). U.S. EPA is
providing information that water resource managers could use in developing their SABS
criteria.
How Can States, Tribes, and Territories Use this Document?
States, tribes, and territories that desire to develop and implement SABS criteria may use the
process and methods described in this Framework. The Framework is flexible, allowing many
variations in the combination of indicators, classifications, and analytical methods. This
flexibility allows resource managers to customize the criteria development approach to specific
needs and capacities. It also encourages justification for the choices made in customizing the
process. While these methods and processes are explained individually, in practice they will be
applied simultaneously or in combination.
With this Framework, states, tribes, and territories are presented with scientifically valid tools
and technical elements needed for developing criteria, adopting criteria into standards, and
managing and evaluating performance management actions to support attainment of SABS
standards. Adopting criteria into standards could proceed in phases (i.e., going from a planning
phase, to adoption of improved narrative criteria, and then to adoption of improved numeric
criteria). Management for acceptable SABS conditions and evaluation of SABS criteria
performance are complimentary processes that can be accomplished by monitoring SABS
conditions and designated use attainment.
The Framework for SABS Criteria Development
The Framework for SABS criteria development can be expressed as a seven-step process,
described as follows.
1. Review current designated uses and criteria for a set of waterbodies.
2. Describe SABS effects on the waterbodies' designated uses.
3. Select specific SABS criteria and biological response indicators.
4. Define potential ranges in values of the SABS and biological response indicators.
5. Identify a response indicator value that protects the designated use.
6. Analyze and characterize SABS/response associations.
7. Explain decisions that justify criteria selection.
The most significant aspect of the Framework is that it ties SABS criteria to levels that protect
the many uses of waterbodies (e.g., fishing, recreation, swimming, navigation, agricultural uses,
drinking water supply, and aquatic life). The Framework recognizes that SABS are naturally
occurring and are often altered by human activities that are not necessarily well managed but
could be. It recognizes that the level of SABS that is appropriate for one waterbody type, say a
lake, may not be appropriate for the Mississippi River. To accommodate the range of variability
in waterbodies, their uses, and natural sediment regimes, the Framework describes methods for
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Framework for Developing SABS Water Quality Criteria U.S. EPA
classification of waterbodies, measurement of SABS, and measurement of effects. Then criteria
are selected in an analytical fashion that is scientifically defensible. The criteria are linked to
human values and are readily understood by a lay audience. No single study or analytical method
is used or recommended. Rather, the Framework consists of a step-wise process that allows for
the integration of information from different data sets and different perspectives, thereby
increasing confidence in the criteria.
Several appropriate technical aspects to the Framework are discussed, including measures taken
within the water column (e.g., Secchi depth, turbidity, suspended sediment concentration, and
total suspended solids), within bedded sediments (e.g., percent of fine sediments by extent or
composition at depth), and within the waterbody environment (channel, shoreline, and
bathymetric measures). Indicators of designated use impairment (biological response indicators)
are also discussed, especially biological indicators of SABS impairment. Key determinants of
appropriateness for indicators are their variability and relative distinction between impaired and
unimpaired waterbodies and their demonstrated relationship to desirable characteristics and uses
for those waterbodies.
Classification of Waterbodies
SABS conditions vary naturally among broad types of waterbodies such as lakes, rivers,
wetlands, estuaries, and coastal waters. Furthermore, within each type of waterbody, the supply
and movement of sediment varies with physiographic, climatic, and geologic characteristics. To
establish appropriate criteria for sediment, these naturally occurring processes should be
characterized in as much detail as possible. Natural features such as geology, watershed
topography, stream gradient, waterbody morphology, vegetative land cover, climate, soil
erodibility and other landscape characteristics contribute to the variability in sediment supply and
transport. Development of SABS criteria should take into account the natural conditions and
variability of the water. Regardless of the method used to derive criteria, the outcome should not
be beyond the natural expectations. In addition, criteria must protect designated uses. However,
SABS conditions that reflect pristine conditions may not be necessary to fully protect designated
uses (i.e., aquatic life and recreation goals may be fully supported by SABS conditions that are
different than pristine conditions). Criteria will vary with waterbody type and with other natural
waterbody features with respect to designated uses. The Framework recognizes the potential
need for different criteria based on classification of waterbodies and natural sediment regimes. In
fact, the need for classification is addressed in the first step in the Framework and is evaluated
again in steps 4 and 6, with iteration back to step 1 when refinement is necessary.
Illustration of Methods for Use in Criteria Development
The Framework suggests methods that can be used for SABS criteria development. These
methods are presented to illustrate how states, tribes, and territories may identify appropriate
indicators, link sediment measures with biotic responses, establish expectations for specific
waterbodies, define impairment, and evaluate adequacy of SABS models. The methods that are
presented in this Framework are listed below:
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Framework for Developing SABS Water Quality Criteria U.S. EPA
(1) Measurement of Suspended and Bedded Sediment
• Readily Available Measures
• Sediment Transport Curves
• Relative Bed Stability
(2) Waterbody Classification
• Empirical Classification of Reference Sites
• Fluvial Geomorphology
(3) Associating Suspended and Bedded Sediment with Response Indicators
• Controlled Experiment
• Field Observational Studies
- Percentile Analysis (including Reference Condition Methods)
- Exposures and Effects Analysis
- Conditional Probability Analysis
• Waterbody Use Functionality
While each of these methods can be described separately, U.S. EPA recommends that they be
used together in the Framework to take advantage of the strengths of each. In some cases, a
method is only useful for one step in the Framework. For instance, basic statistical methods for
classification of streams are essential for step 1 of the Framework but inadequate to select
protective criteria. Fluvial geomorphology will alert a resource manager to potential impairment
and reveal the evolution of changing stream morphology, but will not necessarily provide a
measure of sediment or impacts to a designated use. Likewise, indicators of the physical
processes moving sediment supply, such as the Relative Bed Stability method, provide an
understanding of the deviation from natural conditions but do not tell if the designated use is
impaired when there is 5% or 50% more sediment. Similarly, whereas the Controlled
Experiment, Field Observational Studies, and Waterbody Use Functionality methods have the
potential to link desired designated uses with sediment regimes, they do not automatically enable
classification.
During an October 3, 2003 consultation on setting SABS criteria, the U.S. EPA Science
Advisory Board recommended that the U.S. EPA develop a synthesized approach. This synthesis
has become the Framework. The Framework includes examples of criteria development
illustrating the potential synthesis of methods that could be applied to various waterbody types
and with different designated uses.
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Framework for Developing SABS Water Quality Criteria
U.S. EPA
Chapter I. INTRODUCTION
LA. Purpose of this Document
Suspended and bedded sediments (SABS) occur naturally in all types of waterbodies. In
appropriate amounts, they are essential to aquatic ecosystems. However, imbalanced sediment
supplies have repeatedly ranked high as a major cause of waterbody impairment (U.S. EPA
2003a). The quantity and characteristics of SABS may affect the physical, chemical, and
biological integrity of streams, lakes, rivers, estuaries, wetlands, and coastal waters. Excessive
SABS (and in some cases, insufficient SABS) can impair waterbody uses such as aquatic life
navigation, recreation, and filterable sources of drinking water.
In response to evidence that imbalanced sediment
supplies have negatively affected water resources
throughout the United States (U.S. EPA 2000a), the
U.S. Environmental Protection Agency (U.S. EPA)
is providing the tools that could support the states,
tribes, and territories in their efforts to establish
SABS criteria in water quality standards that protect
the ecological integrity and beneficial uses of water
resources.
The Agency is providing the
tools that could support state,
tribe and territory efforts to
establish SABS standards that
protect the ecological integrity
and beneficial uses of water
resources.
This document describes a scientific process for
establishing SABS criteria that are protective of national water resources and their designated
uses. This Framework includes (1) an introduction to SABS criteria issues, (2) programmatic
elements for the SABS criteria development effort, and (3) technical elements for developing
SABS criteria. The Framework can be implemented by states, tribes, and territories at the local
and regional levels to meet their specific requirements.
While preparing this document, U.S. EPA consulted various resources, including U.S. EPA
Water Quality Reports and current state and U.S. EPA criteria for SABS-related measures as
well as the U.S. EPA Science Advisory Board and state water quality resource managers. The
results of this preliminary work, along with background on SABS criteria issues, are contained in
Chapter I (Introduction). Chapter II covers the programmatic elements of the Framework,
including the actions U.S. EPA may take towards providing additional information and
implementing the Framework. Chapter III focuses on the technical elements of SABS criteria
development. This chapter illustrates the direction that the scientific research is taking, or could
take. The Framework is described as a process that includes distinct activities and steps, concepts
inherent to the Framework., and methods that can be used within the Framework. The
Framework is illustrated with actual and hypothetical examples for SABS criteria development.
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Framework for Developing SABS Water Quality Criteria
U.S. EPA
LB. The Need for SABS Criteria
The imbalanced loading of SABS to aquatic
systems is considered one of the major causes of
water quality impairment in the Nation (U.S.
EPA 2003a). The 305(b) Water Quality Reports
have consistently listed turbidity, suspended
solids, sediment, and siltation as dominant
polluting factors in rivers and streams, lakes,
reservoirs, ponds, wetlands, and ocean shoreline
waters (Table 1). In 1998, approximately 40%
of assessed river miles in the U.S. had problems
arising from sediment stress (U.S. EPA 2000a).
We use the term 'SABS
imbalance' to connote significant
changes in normal SABS
loading to aquatic systems (i.e.,
changes in comparison to
natural patterns that typically
result in increases or reductions
in sedimentation).
Table 1. Ranks of SABS stressors among all stressor types3 (Modified from Berry et al. 2003).
Waterbody Type
Rivers & Streams
Lakes, Ponds, &
Reservoirs
Wetlands
Estuaries6
Ocean Shoreline
Waters
Pollutant/Stressor
Siltationb
Suspended Solids
Siltation
Suspended Solids
Sediment
Sedimentation &
Siltation
Siltation, Suspended
Solids, Sediment, or
Turbidity
Turbidity
Siltation
Suspended Solids
1994
2cof7d
7 of 7
2 of 7
5 of 7
1 of 9
Oof 7
4 of 7
5 of 7
1996
1 of 8
7 of 8
3 of 7
6 of 7
1 of 8
Oof 7
2 of 8
5 of 8
1998
1 of 8
3 of 7
5 of 7
1 of 7
Oof 7
2 of 7
4 of 7
2000
2 of 8
3 of 7
1 of 6
Oof 7
3 of 7
4 of 7
a Comparisons of 305(b) National Water Quality Inventory Reports by year and waterbody type.
b For streams, siltation is synonymous with increased embeddedness and percent fines.
c Rank among Pollutants/Stressors
d Total number of Pollutants/Stressors. As an example, Siltation was ranked second out of the
seven Pollutants/Stressors found on the table for Rivers & Streams in the 1994 Report.
eNote that Siltation, Suspended Solids, Sediment, and Turbidity were not on the estuary lists for
the 1994, 1996, 1998, and the 2000 305(b) Reports.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
Effects of sediment loading in natural, pristine ecosystems are complex, multi-dimensional and
not fully understood. Changes in sediment loading caused by human activity - SABS imbalance
- add further complexity. We use the term 'SABS imbalance' to connote significant changes in
normal SABS levels in aquatic systems (i.e., changes in comparison to natural patterns that
typically result in increases or reductions in sedimentation). SABS stresses result from changes
in sediment loads originating from within the watershed that ultimately compromise the
ecological integrity of the aquatic environment (Nietch et al. 2005). Waterbody impairment due
to SABS is commonly recognized when aquatic life is impaired. While the biotic effects are the
focus of much of the criteria development effort, other designated uses such as navigation,
drinking water sources, recreation, and agriculture are also vulnerable to impairment by SABS
and are addressed by this Framework.
I.B.I. Suspended and Bedded Sediments (SABS)
SABS are defined as organic and
inorganic particles that are suspended in,
are carried by, or accumulate in
waterbodies. This definition includes the
frequently used terms clean sediment,
suspended sediment, total suspended
solids, turbidity, bedload, fines, deposits,
or, in common terms, soils or eroded
materials. This definition of SABS
includes organic solids such as algal
material, particulate detritus, and other
organic material. SABS are natural parts
of aquatic systems and are not considered harmful until they are out of balance, that is, excessive
or deficient. SABS may be a cause of impairment if this material diminishes the quality or
quantity of the aquatic resource by altering the behavior, health, or survival of biota, the
availability of habitat, the stability of channels and banks, the natural amount and size
distribution of particles in the water column and on the bottom and banks of waterbodies, or by
otherwise impairing designated uses of waterbodies.
SABS are defined as organic and
inorganic particles that are
suspended in, are carried by, or
accumulate in waterbodies. ... SABS
are natural parts of aquatic systems
and are not considered harmful until
they are out of balance, that is,
excessive or deficient.
SABS are further defined in terms of particle sizes, which are related to the mode of action in the
aquatic environment. They can be defined as fine sediment and coarse sediment. Fine sediment is
typically (though not rigidly) considered to consist mostly of particles smaller than 0.85 mm and
coarse sediment is between 0.85 and 9.5 mm. Particles less than 0.063 mm (silt and clay) remain
suspended in flowing freshwater and are largely the cause of turbidity but may settle during low
flow in low gradient streams (Idaho DEQ 2003).
This Framework addresses the physical properties of SABS and intentionally does not address
the effects of co-occurring contaminants or nutrients. Nutrient criteria have been developed by an
U.S. EPA supported effort (see National Nutrient Strategy, U.S. EPA 1998). U.S. EPA has dealt
directly with the toxicity of chemicals in sediments through its work on Equilibrium Partitioning-
Derived Sediment Benchmarks (U.S. EPA 2003b, 2005a). U.S. EPA does recognize, however,
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Framework for Developing SABS Water Quality Criteria U.S. EPA
that managing SABS in the aquatic environment will have consequences on the amount of
toxicants and nutrients associated with SABS and these relationships may need to be examined
further in future efforts. An example of the integrated assessment of sediments and nutrients is
described in the technical section using criteria development for the Chesapeake Bay (Section
III.D.3).
I.B.2. Summary of the Ecological Effects of SABS
The Nation's waters have many designated uses, including drinking water, navigation,
recreation, agriculture (such as irrigation), aquatic life, and fishing for sport and food. While
SABS can affect all of these uses, U.S. EPA is currently focused on SABS effects on aquatic life
for several reasons. First, when SABS diminish the quality of aquatic life by degrading habitat,
other uses such as recreational or commercial fishing may also be diminished. Second, there is
evidence that aquatic-life uses are one of the most sensitive endpoints of altered sediment supply.
Therefore, measuring and monitoring aquatic organisms may provide an early warning that
SABS may become problematic for a wide range of uses. Early action may prevent other uses
from being impacted. This premise influenced water clarity criteria development for the
Chesapeake Bay, where protection of the vegetative habitat was considered equivalent to
protection of the species that used that habitat and the larger ecosystem (U.S. EPA 2003c). For
these reasons, this Framework addresses waterbody designated uses but has a strong focus on
aquatic life uses (e.g., habitat, foraging, refugia). Because of their importance in ecosystem
functions, the imbalance of SABS can have an impact on ecological integrity at several scales
and trophic levels as depicted in the conceptual model (Figure 1). Therefore, a basic premise for
managing SABS in waterbodies is the need to maintain SABS at levels that are protective of the
ecological integrity of aquatic systems.
SABS differ from toxic pollutants in that SABS, including the organic fraction, occur in
waterbodies in natural or background amounts and are essential to the ecological functioning of a
waterbody. In addition, SABS transport toxicants, nutrients, detritus, and other organic matter at
levels that are critical to the health of a waterbody. SABS in natural quantities also replenish
intermittently mobile bottom sediments and create valuable micro-habitats, such as pools and
sand bars.
Sediments can enter waterways through a wide variety of transport mechanisms, including
surface water transport, bank erosion, and atmospheric deposition. Once in the system, re-
suspension and deposition can "recycle" sediments so that they exert water column and benthic
effects repeatedly over time and in multiple locations. Human activities that increase soil erosion
or alter rates of sediment transport in waterways (e.g., forestry, mining, urban development,
agriculture, dredging, channel alteration, and dam construction) are among the most pervasive
causes of sediment imbalance in aquatic systems (Waters 1995; Nietch et al. 2005). Activities
that decrease sediment to aquatic systems are numerous and varied. A major cause is man-made
reservoirs that trap sediment that normally would be carried downstream. Excessive sediment is
a more common cause of sediment imbalance than is sediment deficiency though both can impair
ecosystems.
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Watershed
Activity
5TSL I^K^e^^ "o
Deposition &
Resuspension
' (Zooplsntei)
Smo/hermg, Shading Smothering,
Buri'al, <"*"> Burial
Embeddedness
Scouring
Dredgiri
Smothering,
.Avoidance
Sediment supply
Reproductive pathway
Trophic pathway
Biological effects
Sediment inputs
(Biota labels)
Figure 1. Conceptual diagram of SABS effects in estuaries (courtesy of W. Munns, U.S. EPA).
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Excessive suspended sediment in aquatic systems decrease light penetration, directly impacting
productivity that is especially important in estuarine and marine habitats, where trophic
interrelationships tend to be more complex and marginal when compared to freshwater aquatic
systems. Decreased water clarity impairs visibility and associated behaviors such as prey capture
and predator avoidance, recognition of reproductive cues, and other behaviors that alter
reproduction and survival. At very high levels, suspended sediments can cause physical abrasion
and clogging of filtration and respiratory organs.
In flowing waters, bedded sediments are likely to have a more significant impact on habitat and
biota than suspended sediments; while most organisms can tolerate episodic occurrences of
increased levels of suspended sediments, impacts can become chronic once the sediment is
settled. When sediments are deposited or shift longitudinally along the streambed, infaunal or
epibenthic organisms and demersal eggs are vulnerable to smothering and entrapment. In smaller
amounts, excess fine sediments can fill in gaps between larger substrate particles, embedding the
larger particles, and eliminating interstitial spaces that could otherwise be used as habitat for
reproduction, feeding, and cover for invertebrates and fish. A noteworthy example of effects of
bedded sediments in streams and rivers is the loss of spawning habitat for salmonid fishes due to
increased embeddedness. Increased sedimentation can limit the amount of oxygen in the
spawning beds, which can reduce hatching success, trap the fry in the sediment after hatching, or
reduce the area of habitat suitable for development. Appendix B details many other direct and
indirect effects of SABS.
I.B.3. State Needs Survey
In September 2004, a survey was conducted to solicit input from nine states on the status of
SABS-related impairment and monitoring in their state, as well as technical, budgetary, and other
needs for developing numeric SABS criteria. Details of the survey are included in Appendix C.
The results presented below pertain only to those states surveyed and cannot be extrapolated to
the entire Nation. Three states (Delaware, New Hampshire, and New York) consider SABS a
minor or lower priority problem, while states in other parts of the country consider SABS a
major problem. SABS criteria appear to be partially established for most of the states surveyed
and are a mix of narrative and numeric criteria and standards.
Wyoming, for example, has numeric criteria for turbidity but narrative criteria for suspended and
settleable solids. The programs under which states apply SABS criteria/standards include Total
Maximum Daily Load (TMDL) reporting, National Pollutant Discharge Elimination System
(NPDES), surface water monitoring programs and various state-level programs. The majority of
states surveyed use turbidity and total suspended solids (TSS) as indicators for suspended
sediments; North Carolina also uses Secchi depth and Michigan uses light penetration. Bedded
sediments are most commonly measured with embeddedness, followed by percent fines,
Wolman pebble counts, substrate stability, best professional judgment using photos, and
intergravel dissolved oxygen.
Most respondents felt the need to improve water quality criteria for SABS in their state. The
Wyoming respondent suggested that there is a greater need for bedded sediment criteria than
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suspended sediment criteria, which already exist in many places (as criteria for turbidity or TSS).
All designated uses, except agricultural uses, were considered vulnerable to SABS impairment.
Each of the states surveyed envision technical and scientific obstacles to SABS criteria
development. Some pointed out that, in most waterbodies, SABS occur naturally and with
significant variability, making the development and application of strict numeric criteria
difficult. Others mentioned the lack of sound scientific data that could lead to numeric criteria for
threatened and endangered species. In addition to technical and scientific obstacles, states may
also face political obstacles where SABS sources are mostly non-point, such as from agricultural
lands. Louisiana was unique in that sediment starvation in their coastal wetlands was the primary
concern; their criteria should be sensitive to the state's efforts at arresting wetland subsidence.
Program elements considered most useful for SABS criteria development include
personnel/expertise, money/grants and access to data on SABS effects from scientific literature
as well as from other states. Some elements of the Framework were considered less useful by a
minority of respondents.
I.B.4. Application of this Framework for Developing SABS Water Quality
Criteria and Standards
Water Quality Criteria
Water quality criteria (WQC) describe the quality of water that will generally support designated
use(s). U.S. EPA, under Section 304(a) of the CWA, periodically publishes WQC
recommendations for use by states, tribes, and territories in developing and adopting water
quality standards. Water quality criteria published pursuant to Section 304(a) of the CWA are
based solely on data and scientific judgments on the relationship between pollutant
concentrations and environmental (and human health) effects and do not consider economic
impacts or the technological feasibility of meeting the criteria values in ambient water.
When establishing SABS numeric criteria, states, tribes, and territories can use the process
described in this document or other scientifically defensible approaches for deriving criteria.
U.S. EPA's 304(a) criteria recommendations have been instrumental for states, tribes, and
territories to control many forms of pollution and improve water quality across the Nation.
As mentioned previously, in addition to aquatic life uses, waterbodies have other designated uses
that need to be protected from stressors such as excess SABS. These include recreation in and on
the water, navigation, drinking water sources, industrial water use, and agricultural water use.
Waterbodies may have multiple use designations, including those just listed and aquatic life.
Water Quality Standards
Water quality standards (WQS) consist of three elements: (1) one or more designated uses for a
waterbody, (2) WQC to protect the designated use(s), and (3) an antidegradation policy. States,
tribes, and territories adopt WQS to protect public health and welfare, protect designated uses,
enhance the quality of water, and serve the purposes of the CWA. Section 101(a) of the CWA
specifies that WQS should provide, wherever attainable, "water quality which provides for the
protection and propagation offish, shellfish, and wildlife and provides for recreation in and on
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the water." Section 303(c) states that WQS should be established taking into consideration
waterbody use and value for public water supplies, propagation offish and wildlife, recreation,
agriculture, industry, navigation, and other purposes.
Antidegradation provisions specify that all existing uses of a waterbody, that have occurred since
November 28, 1975, should be maintained, regardless of whether they are specified as
designated uses. If the water is of a higher quality than necessary to support fishable/swimmable
uses, then that water quality must be maintained unless important economic and social goals
dictate otherwise. A three-tiered antidegradation policy is part of each state's WQS:
Tier 1 Maintain existing beneficial uses of surface waters and prevent degradation
that could interfere with those uses.
Tier 2 Protect water quality in "fishable/swimmable" waters (bodies of water in
which water meets or exceeds the levels necessary to support the propagation
offish, shellfish, and wildlife as well as recreation on and in the water).
Tier 3 Provide special protection for "Outstanding Natural Resource Waters," such
as waters of national or state parks, wildlife refuges, or other waters of
exceptional recreational or ecological significance.
I.B.5. U.S. EPA-OW/OST Standards and Criteria Strategy
Recently, U.S. EPA's Office of Science and Technology (OST) within the Office of Water (OW)
issued a document titled "Strategy for Water Quality Standards and Criteria: Setting Priorities to
Strengthen the Foundation for Protecting and Restoring the Nation's Waters" (U.S. EPA, 2003a).
Working with stakeholders and considering a wide-ranging review of the existing WQS and
criteria program within the context of all CWA programs, U.S. EPA identified 10 priorities for
achieving higher WQS on a national basis. These include providing guidance, strategies, or
approaches for criteria development for several stressors. Producing and implementing a
Framework for the development of SABS criteria was among the top priorities and is the basis
for the present work. OST and the Office of Wetlands, Oceans, and Watersheds (OWOW) are
coordinating efforts with the Office of Research and Development (ORD) to design research and
develop methods that can be used to support SABS criteria development.
One of the milestones of the Standards and Criteria Strategy discussed above was a consultation
with the Science Advisory Board regarding development of SABS criteria. This consultation
took place on October 2, 2003 and resulted in generally agreed-upon recommendations that are
presented in Section ID.
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I. C. Current Water Quality Criteria Related to SABS
I.C.I. Existing/Current U.S. EPA Criteria
In "Quality Criteria for Water" (U.S. EPA 1986), the Agency published the following
recommendations for developing a numeric criterion for suspended solids and turbidity:
Solids (Suspended, Settleable) and Turbidity - Freshwater fish and other aquatic
life: Settleable and suspended solids should not reduce the depth of the
compensation point forphotosynthetic activity by more than 10 percent from the
seasonally established norm for aquatic life.
This criterion has not been frequently adopted or used by states, perhaps because certain methods
are somewhat difficult to perform. A narrative "free from" aesthetic standard that states have
occasionally adopted into their water quality standards was published in the same document
(U.S. EPA 1986), stating:
Aesthetic Qualities -All waters shall be free from substances attributable to
wastewater or other discharges that: settle to form objectionable deposits; float
as debris, scum, oil, or other matter to form nuisances; produce objectionable
color, odor, taste or turbidity; injure or are toxic or produce adverse
physiological response in humans, animals, or plants; [or] produce undesirable
or nuisance aquatic life.
I.C.2. Current State Criteria
In addition to the more recent needs survey discussed in section IB.3 above, U.S. EPA
conducted a study of published SABS criteria in all states in 2001 (Appendix D). Based on the
study, some form of numeric SABS criteria existed in 32 of the 53 states, tribes, and territories,
and the District of Columbia. Narrative criteria were identified in 13 states with no numeric
criteria (and in 23 of the states with numeric criteria as well), leaving eight states with neither
numeric nor narrative sediment criteria identified. Of these eight states without criteria, five
listed an alternative or guide for establishing sediment criteria such as effluent controls or
regional criteria. Additional reviews of state criteria have been compiled by Caux et al. (1997a),
Singleton (1985), Idaho DEQ (2003), and Rosetta (2005).
Of the 32 states with numeric criteria, 30 had criteria for turbidity and seven for suspended
solids. Five of these 32 states listed criteria for both turbidity and suspended solids. Criteria were
in the form of exceedances over background (e.g., "not more than 10% above background" or
"no more than 10 NTUs above background") or absolute values (e.g., "not greater than 100
NTU"). States have established statewide and/or basin-specific criteria depending on the
presence of salmonids. In general, concerns are the effects of water clarity and light scattering on
aquatic life. The majority of states use U.S. EPA method 180.1 to measure turbidity and U.S.
EPA method 160.2 (40 CFR Part 136) to measure TSS. For example, suspended solids criteria
vary from 30 mg/L up to 263 mg/L for aquatic life uses and up to 500 mg/L for storm water
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pollution control in North Carolina. Florida uses transparency as a criterion (not to be reduced by
more than 10%).
States, under pressure to develop and issue total maximum daily loads (TMDLs) for SABS-
impaired waterbodies, are moving forward on their own to develop new-and-improved SABS
criteria from which to develop TMDLs. U.S. EPA believes it is valuable to examine what states
have done in the past, are currently doing, and plan to do in the future in developing SABS
criteria as a way to identify methods that may be useful, either directly or with adaptation, for the
entire Nation. U.S. EPA also believes this same consideration should be given to the SABS
criteria efforts in other countries. Therefore, promising methods used by some states and other
countries have been reviewed by U.S. EPA and are included in the Framework. As new methods
become available, U.S. EPA may review and consider them either for application nationwide or
for updating this document. Criteria have recently been developed by Idaho, Oregon, and New
Mexico (United States), British Columbia (Canada), Australia, New Zealand, and the European
Union (Appendix D).
LD. Recommendations of the U.S. EPA Science Advisory Board
As part of the current effort to develop national SABS criteria, the U.S. EPA Science Advisory
Board met on October 2, 2003 to discuss various methods for establishing criteria. This meeting
resulted in several generally agreed-upon recommendations. It is important to note, however, that
the Science Advisory Board did not reach consensus and votes were not taken. The general
recommendations are summarized here and detailed in Appendix E. The specific approaches
mentioned here are discussed in detail in Section HID.
Overall Recommendations
• Consideration should be given to setting criteria from the management perspective,
classifying by waterbody function and designated uses, while ensuring that resource
managers know what natural levels of SABS are expected for any given waterbody.
• Criteria should be developed for each major waterbody type (lakes, estuaries, wetlands,
rivers, streams, headwaters, etc.) and then tiered by classes of similar waterbody types
within each of these major categories (e.g., high-gradient vs. low-gradient mountain
streams).
• As no single criterion or indicator will work for each major waterbody type and class,
several different criteria or indicators should be developed to address key distinctions
in SABS among waterbody types and classes.
• Criteria should be based on a synthesis of methods that demonstrate the relationship
between the measurements of SABS and aquatic life or a valued ecological resource.
The conditional probability and reference condition approaches could be used to meet
this requirement.
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• The strengths and weaknesses of each method should be clearly explained for states,
tribes, and territories.
• Any uncertainty with respect to ecological theory or statistical model development
should be clearly documented and considered during criteria selection and
implementation.
• The problem of SABS imbalance resulting from too little sediment should not be
overlooked.
• Recommended methods should be clear and understandable.
• Work should continue that develops methods and other approaches for establishing
SABS criteria. Real data should be used in creating examples of a synthesized process.
• Recommended that there is national consistency in assessment, management, and
evaluation.
It has been and will continue to be the intention of the U.S. EPA to consider all of these
recommendations during the development and implementation of this Framework. For instance,
the recommendation that actual or available data should be used in creating examples of a
synthesized approach (or combination of approaches) was interpreted as a need for case studies.
U.S. EPA initiated a case study that is included as a draft using hypothetical examples (see
Section III.E). Case studies, using actual state data, are now under development and may be
included in U.S. EPA SABS documents in the future. The Board did not suggest any new,
unique, or "silver bullet" methods that would solve all problems or be quickly and easily
implemented.
However, U.S. EPA is not taking a supervisory role in defining criteria near jurisdictional
boundaries but will support the efforts of bordering states and act as a mediator if needed. This
document is designed to provide a Framework for developing SABS criteria. It is not a substitute
for the CWA or U.S. EPA's regulations nor is it a regulation itself. The Framework does not
impose legally binding requirements on U.S. EPA, states, tribes, territories or the regulated
community and may not apply to some particular situations. U.S. EPA, state, tribal, and
territorial decision-makers retain the discretion to adopt methods and approaches on a case-by-
case basis that are appropriate to their SABS needs.
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Chapter II. PROGRAMMA TIC ELEMENTS OF
SABS CRITERIA DEVELOPMENT
II.A. Possible Uses of this Framework
Using this Framework, states, tribes, and territories could develop new, or review existing,
SABS criteria (narrative and numeric criteria). These criteria could then be incorporated into
WQS and implemented in various water quality programs. Criteria development could follow the
process as described in Chapter III, proceeding first in regions and watersheds where applicable
data are currently available. Where states have existing SABS criteria, these criteria could be
reviewed in the context of the overall Framework.
II. B. Resources for Framework Implementation
For those states developing SABS criteria or beginning the process of addressing SABS, this
Framework provides several resource elements. For example, components of the Framework
include techniques for sampling, data management, and analysis. The resources include
professional contacts for technical and administrative issues and communication vehicles. These
tools and resources are yet to be developed, and the following list is a sampling of possibilities.
The final list of tools and resources may differ as needs are identified, tools are developed and
U.S. EPA support evolves.
U.S. EPA Expertise
U.S. EPA Headquarters, ORD, and Regional staff will be interested in how state, tribal, and
territorial officials, and other interested parties develop SABS criteria.
Internet Resources
In support of SABS criteria development, U.S. EPA plans to build and maintain a Web site
devoted to SABS information and knowledge exchange. This Web site could serve at least three
functions: (1) as a portal for communication among states, tribes, and territories (2) as a source
of data on SABS exposures and biotic responses and (3) as a center for distribution of tools for
SABS criteria development.
Communication
SABS criteria development will benefit from dialogue among all parties involved, including
state, tribe, and territorial water resource managers, scientists, National and Regional SABS
Teams, and U.S. EPA. Moreover, parties will benefit and learn from third-party communication.
For example, exchange of information between a state scientist and Regional SABS Team
members may be useful to a scientist in another state in the same region. A SABS Web site may
help facilitate this type of communication, where frequently asked questions can be answered,
problems and solutions can be posted, virtual brainstorming can occur, and innovative ideas can
be shared.
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SABSDatasets
As datasets with sufficient data for analysis are identified, they should be made available, for
example, via a Web site. These datasets may include state monitoring records, academic studies,
or federal agency research. Perhaps the biggest challenge of SABS criteria development will be
establishing links between SABS exposures and biotic responses so that effect levels can be
identified. Reviewing the existing data in the primary scientific literature will help this process
(e.g., Berry et al. 2003). These reviews may be the starting point for quantifying relationships
between SABS and biotic responses, which may assist in both setting criteria and monitoring
management actions.
Data Management: Storage and Processing
States, tribes, and territories will benefit from consistent and compatible data storage, retrieval,
and assessment systems to help interpret data so that it is meaningful for management decisions.
Convenient data storage and modeling programs will enhance data assessment, and also, if
consistent throughout a region, promote coordinated inter-state surveys and data sharing. The
U.S. EPA Storage and Retrieval database (STORET) or the U.S. Geologic Survey may be an
appropriate starting point for data management though other alternatives may exist or be
developed.
//. C. Integration of the SABS Framework with Existing State
Programs
The SABS Framework provides a scientifically defensible process and the necessary methods
and analytical tools for states, tribes, and territories to develop or adjust numeric SABS criteria
into their WQS. This Framework could help water quality resource managers support efforts to
achieve and maintain protective water quality conditions as well as identify impaired waters and
their causes. Some state, tribal and territorial efforts that may be supported by SABS Framework
implementation and WQS revisions include
Total maximum daily loads (TMDLs), waste load allocations (WLAs) for point sources
of pollution and load allocations (LAs) for non-point sources of pollution
• Water quality management plans which prescribe the regulatory, construction and
management activities necessary to meet the waterbody goals
• NPDES water quality-based effluent limitations for point source discharges
• Water quality certifications under CWA § 401 for activities that may affect water quality
and that require a federal license or permit
• Reports, such as those required under CWA § 305(b), that document current water
quality conditions and CWA § 303(d) that list impaired waters and
CWA § 319 management plans for the control of non-point sources of pollution.
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Protection of waterbodies from SABS imbalances may require management actions. SABS
management is a process that should integrate a number of programs and management
approaches, including but not limited to
• Non-point and Watershed programs
• NPDES Permitting programs
• Nutrient and Contaminated Sediment Management
• Marine Protection, Research, and Sanctuaries Act (MPRSA) permits for ocean dumping
CWA permitting for dredge and fill activities
• Biosolids Management programs
As the process and methods outlined in this Framework are implemented or utilized, we will
informally gather and evaluate feedback and experiences from states, tribes, territories, and other
water resource managers to ensure the SABS Framework works well. Suggestions, comments,
and input may include data sets, existing analysis or insights into the interactions between SABS
sources and waterbody conditions and knowledge of SABS conditions and designated use
attainment. If necessary, we will revise the document accordingly and issue another edition.
II.D. Implementation of SABS Criteria and Standards
As stated previously, the primary goal of this Framework is to provide useful tools for
developing SABS criteria. This Framework could also help water quality resource managers
manage and evaluate SABS through application of criteria and standards. There are some
fundamental management concepts that should apply in most situations. The SABS program
needs to consider what activities will be needed once SABS criteria have been established.
Possible sequential steps are outlined in Table 2.
This Framework incorporates all the key elements essential to good management planning, but
the user might find that some steps can be consolidated or that circumstances necessitate a
different sequence. With a good database predicated on reliable indicators and the comparable
analytical methods for development of regional SABS criteria, states, tribes, and territories will
be capable of assessing the SABS status of their waters, and establishing their criteria as well as
planning, prioritizing, and evaluating their management responses.
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Table 2. Sequential elements of a SABS management program.
Step
Description
1
Identify
Problem
Identify waterbodies where SABS may contribute to non-attainment of aquatic life and
other designated uses based on landscape or mechanistic screening. Collect SABS indicator
measurements from the sites to confirm exceedance of protective SABS criteria. If
possible, collect biological data or other indicators of designated uses to confirm loss or
reduction of the designated use. If the designated use is not impaired, the level of SABS
may be tolerated at the location and the site need not be listed as impaired. If there is
reduction or loss of a designated use, the impairment should be addressed. The problem
should be defined in terms that make it possible to seek a solution. Be aware that if the
designated uses are fully supported but sediment is exported to other waterbodies, these
sites may be a source for sediment that is impairing a different waterbody.
Investigate
Background
Use literature searches, questionnaires, interviews, and other background investigations to
describe the lost designated use due to exceedance of SABS criteria. Compile and analyze
available data and other information. Develop list of possible sediment loading sources
and/or other factors leading to SABS imbalance. At this and the following two stages,
identify and characterize fully supported biological and physical reference conditions or
reference sites.
Gather Data
Design and conduct a field study to sample physical, chemical, and biological parameters
and sediment loading sources in the watersheds. This step should be of sufficient duration
to accommodate seasonal and annual variation and possible storm events.
4
Confirm
Problem
Conduct a thorough causal assessment of all of the above information. Consider the other
possible causes for the impairment. If SABS are identified among the probable cause(s),
estimate sediment loading from all identified sources.
5
Develop
Alternative
Management
Options
Develop a list of management alternatives to address each sediment source. Evaluate risk
associated with each alternative and its impact on present uses with respect to the
likelihood of restoring the designated use, scientific validity, cost-effectiveness, and
sociopolitical feasibility. Involve local and state-level governments, property owners,
citizen groups, and public and business interests in discussions about the optimal approach.
Potential management options for SABS in different waterbodies are presented in Table 3.
6
Detail
Management
Plan
Prepare a plan that discusses how to address each key element of the SABS problem in the
most effective sequence. Indicate the rationale for selecting a particular course of action.
Include a stepwise sequence of coordinated activities in detail. Management plans are
typically written for a five-year period. Changes in SABS ought to be detected in this time
frame, which is short enough to be accommodated within most budgets. Longer projects
might require sequential management plans and will be more apt to detect biological
recovery.
Implement and
Communicate
Initiate the management program, including consideration of SABS water quality criteria
(WQC) and other WQS. Where appropriate, establish SABS limitations in NPDES permits
and develop TMDLs as elements of the program. Maintain community, interest group, and
other agency involvement through regular updates on the process. Communications may
begin at step 4 or sooner but should be emphasized here.
8
Monitor and
Review
Incorporate water quality monitoring before, during, and after the project to demonstrate
relative response of the system to management efforts. Build in specific intervals for
management review to allow response to changing circumstances, modifications of
approaches and schedules, and changes in emphasis.
Complete and
Evaluate
Determine if the water resource has been protected or improved. Give credit to the
community and other participants. Report on successes and failures for future applications
and on lessons that are learned.
10
Monitor and
Maintain
Controls
Water resource monitoring stations and parameters continue on a reduced scale (e.g., fewer
sampling stations, fewer parameters, less frequent sampling). Ensure regular maintenance
of management efforts to preserve the effects achieved. Monitoring provides warning of
any future degradation, allowing resource managers to intervene in a timely, cost-effective
manner. Close the cycle by returning to step 1.
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II.D.l. Management Options
The management of SABS imbalance involves a sequential investigation and decision-making
process, including a multidisciplinary evaluation of possible mitigating, remedial or other
alternative actions to address SABS problems and prioritize them and their possible solutions.
Although not intended to be exhaustive, Table 3 summarizes remediation, protection, and
management approaches by waterbody type. It is an introductory presentation of some of the
readily evident options that states, tribes, territories and other responsible parties can use to make
a positive response to the situations with imbalanced SABS regimes.
Another management resource is the "Draft Handbook for Developing Watershed Plans to
Restore and Protect Our Waters" (U.S. EPA 2005b), which is available at
http://www.epa.gov/owow/nps/watershed handbook/. The handbook contains in-depth guidance
on quantifying existing pollutant loads including SABS, developing estimates of the load
reductions required to meet water quality standards, developing effective management measures,
and tracking progress once the plan is implemented. As indicated previously, during this pilot
phase we will informally gather and evaluate feedback and experiences from states, tribes,
territories, and other water resource managers to ensure the SABS Framework works well. If
necessary, we will revise the document accordingly and issue another edition.
In considering the various management options for controlling SABS imbalances (Table 3), the
resource manager should keep in mind that the different waterbody types described here may
often be interrelated (e.g., streams draining to and from lakes and rivers entering estuaries and
coastal waters). Under these circumstances, the resource manager would select management plan
practices that are protective of downstream resources. For example, biota in high gradient
streams may tolerate spates of high sediment loads during storms, whereas reservoirs and low
gradient streams may be overwhelmed as these materials settle.
It should be noted that activity in upland portions of the watershed could affect all waterbody
types in the drainage system. Management in upland areas should proceed with consideration of
the connectivity between land disturbance anywhere in the watershed and effects on the SABS
loadings to aquatic systems. Watershed approaches to management provide options that consider
sources and controls for SABS for all connected waterbodies. They offer the advantages of
allowing communities to focus resources on the most serious sources of excess sediment in the
watershed. Additional basic management actions can be found in other U.S. EPA documents
such as Protocol for Developing Sediment TMDLs (1999) and Guidance Specifying Management
Measures for Sources of Nonpoint Pollution in Coastal Waters (1993).
An example of an assessment framework to guide sediment management actions for streams is
the U.S. EPA-funded study called the Watershed Assessment of River Stability and Sediment
Supply (WARSSS). It is based on geomorphic analysis of current sedimentary states of
watersheds and stream systems and pertains to development of a sediment assessment framework
(http://www.epa.gov/warsss). WARSSS is based on modeled associations between SABS
sources and channel conditions and the models are calibrated on field observations.
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Table 3. Issues and management options for addressing SABS imbalances by waterbody type.
STREAMS AND RIVERS
LAKES AND RESERVOIRS
WETLANDS
ESTUARIESAND
COASTAL WATERS
Issue Area
Land use
Hydrology, hydraulics
(flow regime, storm water
management, stream
regulation)
Impoundment removal
Restoration of riparian
and flood plain wetlands
Storm water management
Vegetative buffer zones
Watershed land use
changes
Habitat restoration
Water level control
Restoration and protection
of strategic wetlands
Storm water management
Wetland protection and
restoration
Vegetative buffer zones
Watershed land use
changes
Land use planning
Protect and restore
streams entering wetland
Land use and
development controls
Restricted
estuaries/coastal areas
Shoreline erosion controls
Sea grass replenishment
Management Option
Include land use as a separate early warning indicator (i.e., if development is
proposed in a watershed, an environmental impact study should be done to
assess the potential impact on the surrounding watershed).
Identify natural hydrologic regimes and use such information in addressing
runoff control or dam operations to better replicate natural conditions in the
waterbodies while allowing development, generating power, or preserving
intended reservoir levels.
Remove man-made impoundments that have lost their utility and are now
causes of flow interruption and sources of downstream sediment imbalance.
Implement programs designed to restore riparian and flood plain wetlands.
Implement storm water BMPs such as constructing ponds, wetlands,
infiltration and detention basins, and diversions.
Preserve or reestablish natural, indigenous vegetation (groundcover, shrubs,
and trees) in the riparian zone to intercept sediment runoff before the runoff
reaches the waterbody.
Identify critical loading sources and promote changes of these land use
practices. Examples of practices to promote are implementation of
conservation farming; use of road, commercial and municipal runoff diversions
and detentions; restoration of woodlots in critical drainage areas; and land use
planning to avoid excessive tiers of lake residences.
Improve lake nursery and spawning areas to restore a diverse aquatic
community and food chain.
Initiate winter or other episodic draughts of lake/reservoir waters to augment
sediment removal or consolidation.
Restore and protect wetlands located in areas critical to water quality concerns.
Implement storm water BMPs such as constructing ponds, wetlands,
infiltration and detention basins, and diversions.
Preserve and restore wetlands through the implementation of voluntary and
regulatory programs.
Preserve or reestablish natural, indigenous vegetation (ground cover, shrubs,
and trees) as buffer zones adjacent to wetlands to intercept sediment runoff
before the runoff reaches the wetland.
Identify critical land loading sources and promote changes of these land
practices. Examples of changes that could be made include the implementation
of conservation farming techniques; runoff diversions and detentions, filter
strips, and vegetated drainage ways; the implementation of forestry BMPS; and
the implementation of controls on urbanization and industrial development.
Protect wetlands by limiting amounts of impervious surfaces, limiting
development near waterbodies or steep slopes, and minimizing discharges from
storm water, sewer, and septic systems.
Stabilize stream channels and establish riparian buffers to reduce the amount of
sediment entering a wetland.
Promote natural vegetative cover in shore areas and zoning restrictions on
dense residential or commercial/industrial development along shoreline areas.
Protect sensitive waters such as endangered shellfish beds, spawning and
nursery areas, and recovering weed beds.
Implement erosion controls on banks subject to wave or ice damage. Restrict
access to sensitive shorelines, dune restoration areas, and shorelines susceptible
to erosion.
Restore submerged and emergent aquatic vegetation in estuaries, including
wetland areas. Plant and protect emergent and terrestrial riparian vegetation as
further protection of tidal zone wetlands from runoff.
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The study considers hillslope and channel processes responsible for changes in erosion and
sedimentation and related stream channel instability. Two hierarchical levels of assessment are
included that provide (1) an initial broad overview "screening level" to identify and prioritize
potentially high risk watersheds or river systems that require a more detailed predictive
assessment for process-specific mitigation and (2) a process-based, quantitative prediction of
potential sediment sources, magnitude of sediment delivery, streamflow changes, and river
stability related to the nature, extent and location of a variety of land uses. WARSSS includes a
bank erosion model for quantifying the relative contribution of bank erosion versus hillslope and
other sources of sediment (Rosgen 2001). A monitoring methodology related to the prediction
process allows validation of the assessment approach and tracks the effectiveness of
recommended mitigation to reduce existing excess sediment loading and improve channel
stability. As an assessment framework rather than a rigid methodology, individual steps in a
WARSSS assessment are amenable at the user's discretion to substitution of alternate models or
measures better suited to the region or waterbody type being assessed.
II.D.2. Evaluation
When appropriate indicators and criteria have been established, states, tribes, or territories may
be able to evaluate the effectiveness of management and regulatory approaches. Progress in
management of SABS imbalance and designated use impairment should be assessed by
comparing changes in sediment flux from the land, SABS indicators, and designated uses
through the state's water quality monitoring programs. Timely evaluation of program
effectiveness allows for successful management approaches and techniques to be shared and
repeated in similar circumstances elsewhere. Where success has not been achieved, the
knowledge gained is valuable in developing alternative approaches and in avoiding repetition of
the same unproductive activity. This information could be shared through correspondence and
national meetings to enhance management effectiveness.
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Chapter III. TECHNICAL ELEMENTS OF
SABS CRITERIA DEVELOPMENT
III. A. Need for a Technical Discussion in This Framework
This chapter is an introduction to the scientific process, potential methods, and current research
regarding development of SABS criteria. Inclusion of a technical section is intended to provide
as much clarity as is possible to those looking for a defensible, transparent approach toward
setting SABS criteria. The SABS technical workgroup decided that issuing workable scientific
methods, along with the intent to develop SABS criteria, would expedite implementation. The
workgroup committee is aware that this technical information does not cover all possibilities but
believes that these methods provide a starting point to initiate SABS criteria development. The
Framework may encourage research that could further improve the methods.
While all the material has been reviewed by the workgroup, which consist of experts in various
aspects of SABS policy and science and knowledgeable peer reviewers, some of the material
may still be in an exploratory or developmental stage. This applies especially to some of the
analytical methods (Section HID) and the hypothetical example that illustrates how these
methods can be combined to develop SABS criteria (Section III.E).
IILB. Process for SABS Criteria Development
The basic process for developing SABS criteria, outlined in Figure 2, consists of four types of
activities: (1) gathering information, (2) synthesizing the state of knowledge, (3) analyzing
available data, and (4) selecting criteria values. The process begins by gathering information
from the literature, regulations and stakeholders about data sources and possible classifications
for waterbodies. The information is then synthesized, depicted in a conceptual model, and
described in text format. From the conceptual model, measurements are selected and the
rationale for the selection is recorded. Next, available data sets are assembled and analyzed. The
details of some possible analyses are presented in Sections HID and III.E. Outputs from the data
analysis phase may include analysis designs, evaluated classifications, exposure-response
profiles, background SABS regimes, ranges of protective responses, and probabilities of adverse
effects. Finally, the outputs from the analysis phase are considered in the decision analysis phase
where SABS criteria values are selected and the rationale for the selection is described. SABS
criteria can then be implemented within a comprehensive management plan as described in Table
2.
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Sources
-Literature
-Stakeholders
-Regulations
-State Data
Outputs
-Conceptual Models
-Selected Measurements
-Selection Rationale
Outputs
-Analysis Design
-Evaluated Classification
-Exposure Response Profiles
-Background SABS Regimes
-Range of Protective Responses
-Probability of Adverse Effects
Outputs
-Decision Rationale
-Criteria Values
Criteria
Development
Process
Gather
Information
Synthesize
State of
Knowledge
Analyze
Available
Data
Select
Criteria
Values
Revise
Waterbody
Classification
Collect
Additional
Data
Implement
Criteria
Figure 2. Activities and outputs of the SABS criteria development process.
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Although presented as a sequence of steps, iteration may be necessary. For instance, a set of
waterbodies may be classified as a group at the beginning of the process, but new information
may arise and require waterbody types to be assigned to more specific categories. Available data
may be insufficient and require additional data collection. In all cases, analysis that develops
SABS associations with response indicators should take advantage of the benefits of comparing
results from several methods using different data sets, thereby, allowing criteria selection to be
supported by the strength-of-evidence.
The four activities can be expanded to reveal the greater detail shown in Figure 3 that presents
the elements of the SABS Criteria Development Framework (in seven steps). Each of the seven
steps is described briefly below. In addition, hypothetical examples that illustrate how one could
implement the seven steps are presented in Section III.E as a synthesis of the methods. The
methods for classification, analysis, and characterization of SABS/response associations are
presented in Section HID along with specific examples.
III.B.l. Step 1. Review Current Designated Uses and Criteria for a Set of
Waterbodies
The development of SABS criteria begins by selecting and characterizing a type of waterbody
and identifying the specific designated uses for which the local authority desires to set protective
criteria. Although waterbody type (streams, rivers, estuaries, coastal areas, lakes, or wetlands)
may be sufficient as a classification variable, more refined classification relevant to SABS is
usually necessary during this step or in step 4.
Existing designated uses and associated narrative or numeric criteria should be reviewed and an
initial determination should be made as to whether these are protective of the valued resources.
Uses are designated to support and protect navigable waterways, industrial, and agricultural uses,
recreational activities, drinking water sources, and aquatic life. Designated uses may be very
general (e.g., biotic integrity) or more specific (e.g., high-energy, cold-water streams that
supports salmonid fisheries). Extremely vulnerable or highly valued waterbody types may have
their own specific designated uses that provide special protection for valued, threatened and
endangered species or important ecological functions. With a more specific designated use, the
SABS criteria will be more defensible. However, it is important to balance the desire for
defensibility against the need to avoid proliferation of so many specific standards that SABS
criteria become impractical to implement. Davies and Jackson (2006) discuss the appropriate use
of biological information to tier designated aquatic life uses in WQS.
Criteria should be identified for all current designated uses. If these criteria need refinement, or if
a new criterion is needed for a new designated use, then a general description is required of the
point of transition between support and non-support of the designated use for a group of
waterbodies. Initially, the criteria should be described in narrative terms and then quantified in
subsequent steps. It is important to note that premature declaration of a specific threshold may
introduce bias into the criteria development process.
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Gather
Information
1 . Review current designated uses
and criteria for a set of waterbodies
Synthesize
State of
Knowledge
2. Describe SABS effects on the
waterbodies' designated uses
3. Select specific SABS and
response indicators
Analyze
Available
Data
4. Define potential ranges in value of
the SABS and response indicators
5. Identify a response indicator value
that protects the designated use
6. Analyze and characterize
SABS/response associations
Select
Criteria
Values
7. Explain decisions that justify
criteria selection
Figure 3. Seven steps of the SABS criteria development process and relationship to four
activities in Figure 2.
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III.B.2. Step 2. Describe SABS Effects on the Waterbodies' Designated Uses
SABS criteria should have a strong scientific basis, including both a causal mechanism and
empirical evidence of association between SABS and the designated use, described in either
positive terms or in the form of use impairment. A literature review is critical to identify
evidence of causal mechanisms and the current state of knowledge related to the SABS criterion
under consideration, including examples of exposure-response relationships. An additional
review of relevant and available data sets would reveal both potential data sources and
significant data gaps that may affect the course of SABS criteria development.
The current scientific understanding of the ways that SABS impair the designated use may be
described in text and conceptual diagrams (Figure 4). The use of both of these communication
tools helps ensure clarity of thought and consistent logic while developing the SABS criteria.
Their use also enables easier identification of appropriate indicators (see step 3) and ultimately
enables the defense of the selected criteria and standards. Most importantly, the underlying
scientific basis linking SABS with designated uses should be articulated. Sections IB.2 and
Appendix B provide some useful documentation of how SABS can impair waterbody types.
Additional examples of conceptual models can be found in Appendix F and Section III.E.l.
Associations between SABS and designated use in terms of impairment (through the response
indicator) should be supported by peer-reviewed literature or confirmed with data sets that the
state, tribe or territory has compiled and analyzed. For instance, associational analysis
(correlation, regression) of survey data including measurements of both biota and SABS might
show the strength of exposure-response relationships. A combination of mechanistic studies and
correlative associations provide the most defensible rationale for selection of SABS and response
indicators in step 3.
III.B.3. Step 3. Select Specific SABS and Response Indicators
Selecting specific SABS and response indicators sets the stage for data analysis in steps 4, 5, and
6 through selection of the quantitative measurements for SABS (exposure indicators) that are
believed to reduce the support of a designated use as described in the conceptual model (step 2).
For example some typical measurements are Secchi distance to measure clarity, suspended
sediment concentration to measure inorganic particles and percent fines to measure settled
particles. Composite indicators of sediment movement are calculated from more than one
measurement (See Relative Bed Stability, Section III.D.l). SABS exposure indicators should
represent levels of intensity, frequency and duration as well as quantify the attributes of SABS
that are responsible for impairment as evaluated in step 7. A mechanistic connection between the
SABS indicator and the response indicator, as described in step 2, is also necessary to support the
analyses described in step 6.
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Anthropogenic
Activities
Land Use
Urbanization
-Construction
-Imperviousness
-Street Dirt
Silviculture
- Harvests
-Riparian Loss
Agricultural
-Tiling
-Ditching
-Wetland Loss
-Farm/Range
Practices
Sediment-related Process Alterations
^ Land- ^ Water-
Based Based
Stream/Lake/
Estuary/ Wetland -
Sediment Stress
Related Ecological
Parameters/Processes
Ecosystem
Health Effects
Figure 4. Conceptual linkages among sources of sediment stress and aquatic ecosystem health
(Nietch et al. 2005).
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Also in step 3, the response measures that will be used to define impairment are selected.
Examples of response measures include abundance of a species, presence or absence of a
species, and clogging rate of drinking water filters due to source water impurities. In some cases
the distinction between the SABS and the response indicator can be confusing. For instance, rate
of stream bank erosion may be a measure of sediment to a stream, a SABS indicator, or it can be
a measure of aquatic habitat loss or damage to adjacent real estate, a response indicator as
described for the Waterbody Use Functionality method (Section III.D.3). Care should be taken to
recognize how the indicator is being used.
Indicators should be selected that are appropriate for the waterbody type, classification, region,
and designated use. Furthermore, indicators should be selected that have the following
characteristics: (1) association with the designated uses, (2) quantifiable with available or
accessible data, (3) dependable measurement characteristics, (4) appropriate for the specific
analytical method, and (5) valued by stakeholders. Response indicators should relate directly to
the designated use and quantify how well the waterbody type is meeting expectations for that
use. If the designated use is the support of aquatic life, biocriteria such as an index of biotic
integrity may be the appropriate indicator of response. The best response indicator would have a
robust relationship with SABS levels. Existing biocriteria probably address general impairment,
not SABS-specific impairment, and metrics that are more responsive to SABS levels should be
selected as response indicators if they are available and the responsiveness can be documented.
For designated uses more specific than "aquatic life" other appropriate entities and attributes
may be used for defining attainment (U.S. EPA 2003d).
After the response indicator is selected, the level of protection is defined. This is a value
judgment. For chemical criteria, the U.S. EPA has defined that level as protecting 95% of the
tested species. Identifying the level for sediment is challenging. Current knowledge of SABS
effects does not permit the same type of rigorous calculation for SABS. In the meantime,
alternative standards can be used. A protective level may be pre-determined if criteria already
exist in state standards for the designated use selected in step 1. Otherwise, impairment
thresholds can be determined in step 5.
Data availability and accessibility may be significant factors in the selection of indicators. Many
state programs are currently collecting and compiling monitoring data for purposes other than
SABS criteria development. If these monitoring data are sufficient and relevant to the SABS
criteria development effort, they should certainly be used, eliminating the need for a new and
specifically designed monitoring program. Sufficiency of existing data should be determined
through consideration of the program sampling design, sample size, sample frequency and
timing, performance characteristics of the data (precision, bias, accuracy, representativeness, and
completeness) and whether the indicators already sampled represent relevant SABS and response
measures. Existing multi-purpose data would be valuable for preliminary analyses of potential
value ranges (step 4), protective response indicator levels (step 5), and exposure-response
relationships (step 6).
If existing data are found to be insufficient or irrelevant in steps 3-6, then a new and specifically
designed SABS monitoring program should be implemented. New study designs that incorporate
sampling of biological assemblages or individual taxa should target the biota that have
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measurable responses to the SABS indicators of interest over the expected range of values as
recorded in the scientific literature (step 2). The sampling design used to collect the data is very
important. Data sources and sampling designs can introduce bias and imprecision. Imprecision
adds noise that limits the ability to reach sound conclusions. Bias clouds our understanding of
mechanisms but its uniform nature still allows trends to be detected. Interpretation of data should
assume that both processes are acting to increase uncertainty and that attempts to minimize their
effects will be necessary. A probability-based design is ideal for quantifying status and trends
and allows extrapolation of analytical results throughout the geographic area of interest.
However, a targeted design, including the highest and lowest quality sites, is typically required to
assure that the full range of exposure and response is represented to develop a complete
exposure-response model. A hybrid design, a probability-based design augmented with targeted
sites, combines the advantages of both methods and improves the overall analysis.
Frequency and timing of sample collection may also be an important consideration in the
selection of indicators. For instance, some suspended sediment indicators vary with climatic as
well as geographical variation. Data for such indicators may need to be collected more frequently
or with prescribed timing in relation to storm events. Both data collection and adjustment of
expectations can be more complex for some indicators, and investigators should be confident that
they can collect sufficient data to account for multiple sources of spatial and temporal variability.
III.B.4. Step 4. Define Potential Ranges in Value of the SABS and Response
Indicators
Once the ecology of the waterbody type is reviewed and SABS and response indicators are
selected, then it is time to begin the analysis phase. The first step is to analyze the natural and
altered waterbody characteristics that affect SABS regimes. For instance, SABS regimes may be
affected by natural differences in responses to SABS variables by region, waterbody size,
geomorphology, hydrology, lithology, soils, and so on. They may also be affected by land uses
or modifications to the waterbody itself such as dams, channelization, and water diversion, to
name a few (see Cross-Cutting Concepts, Section III.C.I, for a more extensive description.).
Characterization of the natural and disturbed SABS regimes and response indicator values is
dependent on waterbodies selected in step 1 and the appropriate classification within that
waterbody type. Classification is typically based on expected, not observed, natural indicator
levels. Waterbody classifications are evaluated in light of the potential and observed responses at
step 6.
The process of classification or stratification identifies waterbody types with shared SABS
regimens so that variability within a class is minimized compared to the variability among
classes or variability caused by disturbance. For instance, high gradient streams would be
expected to have less deposited sediments than low gradient systems where stream power is less
and, therefore, particles settle. Properly recognizing natural supply regimes is particularly
important for wetlands, where alteration of sediment supply could mean the difference between
wetland loss due to accelerated subsidence or loss due to filling. Analytical methods that may be
used to classify streams for SABS include most statistical tests that allow comparison among two
or more potential populations. For example, if the central tendencies or distributions for
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measured suspended sediment concentration are different for undisturbed streams from two
different ecoregions, these two types of streams should be analyzed separately and may require
different sediment criteria. Issues associated with classification are more fully described in
Section III.D.2. The sub-classes of waterbody types are then evaluated for existing and nearly
natural levels of SABS.
Sediment supply and redistribution are natural processes that can be disrupted, leading to
impairment of the designated uses of waterbodies. When impairment relates to rates of habitat
loss or other non-aquatic biological endpoints, natural levels of SABS should be estimated to
determine appropriate levels that will maintain or restore the designated use. Natural levels of
SABS can be modeled using site and landscape characteristics or observed within groups of
reference sites with similar characteristics. The potential natural range of a SABS indicator for a
set of waterbodies is usually not the same as the observed range of the indicator for the same set
of waterbodies. Examining the discrepancy between the potential and the observed is an
instructive exercise in determining the extent and magnitude of SABS imbalances. Like the
analysis of SABS indicator value ranges, the natural potential and observed ranges of response
indicator values should also be examined in this step. This exercise will illustrate the extent and
magnitude of response indicator imbalances. These values may prove useful in determining a
threshold of non-attainment of designated use in step 5.
III.B.5. Step 5. Identify a Response Indicator Value that Protects the
Designated Use
If there is a preexisting criterion for the designated use, for instance, a defined score from a
benthic invertebrate index, and this criterion is used as the response indicator, then the criterion
level for attainment identified in step 1 is the value used in subsequent analysis steps. If there is
no preexisting criterion that is acceptable or if a more specific response indicator is preferred,
then a response level that protects the designated use should be selected.
An appropriate transition point may be selected as a threshold of impairment by analysis of
available data. Because natural systems are characterized as responding incrementally to changes
in exposures, response indicators rarely exhibit an unambiguous inflection between unimpaired
(or minimally impaired) and impaired conditions. Therefore, threshold levels of impairment
should be supported with a detailed description of the procedure used to determine the threshold,
preferably documented with peer-reviewed literature. There are three general ways to set
thresholds for a given set of analyses on a data set:
(1) Ad hoc - A subjective approach in which thresholds are arbitrarily set at a specific percentile
of reference sites, all sites, or some other subset of the data. The result may be biased because it
depends on how the sites and percentile were selected. In explaining the selected threshold, this
potential bias and subjective process should be recognized.
(2) Resource Managers decision - A resource manager sets a threshold that she/he is comfortable
with - for example, at 90% probability of identifying a degraded resource. Rationale for
threshold selections can include considerations of costs associated with false positive and false
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negative results. It can also include the resource manager's preferences regarding acceptable
uncertainties, tolerable sacrifices, and desirable resource protection.
(3) Statistical significance - An objective approach that is dependent on the sample size and
variability. However, subjective decisions must be made in defining a difference to check for,
perhaps in biomarkers, and the level of significance to use.
III.B.6. Step 6. Analyze and Characterize SABS/Response Associations
A specific body of water is impaired when it is not attaining its designated uses. Step 6 describes
the procedure for identification of the level of SABS that is likely to cause failure to attain a
designated use. First, it is necessary to show a relationship between the SABS and response
indicators using one or more of the available quantitative analysis techniques. Analytical
methods to establish an exposure-response relationship are of two types, based on either
controlled experiments in the laboratory or field or descriptive analyses of biological and SABS
indicators as they normally occur in the region, often termed "field observations." Field
observations can be analyzed as a continuous or categorical relationship. Next, SABS levels that
are either detrimental to or protective of the designated use must be identified. This may be
accomplished by relating SABS indicator values with the transition point for the response
indicator identified in step 5.
There is always uncertainty when trying to link exposure levels to an effect, in this case, linking
SABS levels with use attainment. Awareness of the sources of these uncertainties and
recognition of assumptions made during study design, data collection, and analysis are
paramount. Some key issues to consider for dealing with uncertainty are mentioned here.
Detailed guidance may be more fully described in future technical manuals.
Imbalanced SABS regimes may occur concurrently with other stressors, such as elevated
nutrients or temperature. In such cases of multiple, simultaneous stressors, it is possible that the
SABS indicator may be a causal agent of use impairment at only some of the sites used to
develop the relationship. It is also possible that SABS may indirectly cause effects through an
intermediate cause, such as settled particles restricting the flow through interstitial spaces in the
bedded sediments thus reducing food availability, gas exchange, temperature maintenance, and
waste removal (see Appendix F, Model 2). The SABS would then be considered part of a causal
pathway that results in a deleterious effect. Controlling for multiple stressors and accounting for
complex secondary effects is sometimes possible when using controlled experiments (see
Section III.D.3). However, any correlative association may be confounded and may not be
causal. These caveats must be considered when applying any of the methods. Nevertheless, the
SABS indicators should be shown to be associated with a biological response. A SABS criterion
can then be determined that is likely to result in biological conditions that permit a body of water
to either attain or not attain its designated use(s).
Finally, the waterbody classification identified in step 1 and refined in step 4 needs to be
reevaluated to see if it remains defensible. If further refinement of the classification scheme is
needed, then the process is reiterated until defensible associations are developed. For example, if
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classification of streams by size results in similar levels of SABS for non-attainment in each size
class, then the classification would be unnecessary. However, if classification indicated that
different levels or measures of SABS would indicate non-attainment, then the classification was
important in the criteria development process. At this point, a level of the SABS indicator that
separates attainment from non-attainment for a designated use and waterbody class (the SABS
criterion) should be established.
III.B.2. Step 7. Explain Decisions that Justify Criteria Selection
The scientific basis for setting any SABS criterion should be documented, including the actual
criterion, magnitude, duration, and frequency variations (if necessary). All the steps used to
establish this criterion should be recorded as well (including description of the data used).
Different methods or studies will often indicate different SABS levels. The rationale for
resolving these differences must be clear, reasonable, and scientifically defensible. Factors that
may influence the decision may include choosing the most conservative method, selecting the
method that enables the use of the highest quality data, averaging the results of several methods,
or incorporating the weight of evidence in other ways. See Linkov et al. (2004) and Stahl et al.
(2002) for various decisional analysis approaches.
One way to illustrate options that have been considered is to model expected impacts using
simulations that reflect various potential SABS criteria. Building models that link criteria with
impacts for evaluating potential criteria offers a number of advantages. For example, accurate
predictive models require a thorough working knowledge of a system. If the output of such a
model does not reflect field observations (e.g., relationships among causes, stressors, and
responses are not consistent), this might indicate that more information about a system is needed
to make effective management decisions or that the model needs refinement. Conversely, models
that accurately reflect the relationships seen in field data may be useful for making management
decisions. Models also allow virtual manipulation of systems beyond what is typically possible
via experimentation, and without exorbitant time or cost commitment. For instance, what is the
effect of setting a criterion at 30% versus 10% fines? If a researcher has developed a model of
SABS effects on low-gradient streams in forested watersheds with aquatic life designated use,
then the model could be used to compare the effect on benthic macroinvertebrate assemblages.
Furthermore, if the indicators were collected with a probability-based design, a cumulative
distribution function can be constructed for the entire resource, known impaired resources,
known unimpaired resources, and best conditions. Then, various SABS indicator levels can be
overlaid on these distributions to evaluate the trade-offs of varying criteria levels, giving an
estimate of error rates associated with the proposed criterion. False positives (identifying a
waterbody as impaired when it is not) and false negatives (failure to detect truly impaired
waterbodies) are valuable quantitative indications of uncertainties associated with an established
criterion. Models can also be used to estimate the costs of remediation to specific criterion levels.
For instance, what will be the cost of being more protective? What are the accrued societal
benefits at the more protective level? And, what is the cost of having to remediate to a greater
level as more waterbodies fall within the category not meeting the criterion?
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Framework for Developing SABS Water Quality Criteria U.S. EPA
III. C. Cross-Cutting Concepts
III.C.l. Classification of Waterbodies
As discussed earlier, SABS conditions vary naturally among waterbody types and geographic
regions because of differences in supply and transport properties. Natural features such as
geology, watershed topography, waterbody morphology, vegetative land cover, climate, soil
erodibility and other landscape characteristics contribute to the variability in sediment supply and
transport (Appendix F, Model 3). Expectations of sediment conditions must be established in the
context of natural variability before impairment can be assessed. Moreover, certain indicators
may be much more effective in certain regions or waterbody types than others. The waterbody
types that form the basic strata are
Rivers and streams
Lakes, ponds, and reservoirs
• Wetlands
• Estuaries
Coastal marine waters.
Further classification to account for more complex natural variability in sediment conditions may
also be needed. Classification to account for natural variability was strongly recommended by
the U.S. EPA Science Advisory Board.
Waterbody types
WQS are typically tailored for different waterbody types. A number of factors, such as flow
regime, water (and sediment) retention time, sediment input sources, indicator biota, and many
others make different types of waterbodies distinct. These natural differences imply SABS
imbalances, and the way that those imbalances are measured and managed, are specific to each
waterbody type.
For SABS criteria development, states, tribes, and territories may consider stratifying, at a
minimum, by the five major waterbody types listed above. Stratifying waterbodies in this way
will lend organizational and scientific plausibility to the overall criteria development process.
Approaches for assessing SABS should consider that although waterbody types can be addressed
separately, they are not independent of one another, but rather, are part of interconnected and
larger basins or watersheds. The interconnectedness of systems highlights the need for integrated
assessment and control of SABS for all waterbody types.
Regions
Stratification by region may be essential for discerning major locational differences in
waterbodies (e.g., ecoregions, biogeographic provinces, physiographic/geologic regions, climatic
regions). For instance, Simon et al. (2004) used ecoregional stratification to produce suspended-
sediment 'reference' values using the flow that occurs, on average, every one and a half years as
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a measure of effective discharge for suspended-sediment transport. Regional stratification may
also serve to simplify the criteria development process by limiting the waterbody types,
analytical data to be reviewed, and range of classes within waterbody.
The well-documented "ecoregion" system (Omernik 1995; Omernik et al. 1988) may be a useful
framework to stratify regions for SABS assessment because it has been used successfully to
develop biological criteria. If it is found to be appropriate for the development of regional SABS
criteria, it is encouraged that the scale of ecoregion aggregation and division be determined. The
degree of variability within each of the ecoregions would determine the final regional scheme.
Ecoregional stratification does not preclude the use of other classification schemes if they are
judged to be more appropriate.
Classification beyond Waterbody Types and Regions
Even after stratifying by waterbody type and region, the variation of natural SABS levels within
these strata may require finer levels of classification or classification based on other factors. For
example, streams within one region may have low-gradient and high-gradient classes. A
measurement of waterbody size (e.g., stream order, lake area, catchment area, discharge) may
also be used to classify waters. Lakes may be classified by size or retention time. These different
classes within waterbody types have different levels of naturally occurring SABS and may
respond differently to an imbalance of SABS. The actual number of classes recognized within a
stratum depends on a number of factors, including variation among classes in natural levels of
SABS, similarities and differences among classes in effective response indicators, and data
available for development of criteria.
The goal of defining classes within strata is to achieve a balance between accounting for the
natural differences in SABS among individual waterbodies and finding some commonalities
among waterbodies so that each river or lake does not become a class. One option is to identify
the waterbody type in the watershed or basin that is less tolerant to shifts in sediment supply.
Criteria developed for this waterbody type may automatically set the criteria for upstream
waterbodies, which may be sources of sediment but resilient in the face of episodic spates of
increased sediment loads. Taking this tact may reduce the number of classes and customized
criteria. It may also enable remediation plans on a basin or watershed scale (see the example for
the Chesapeake Bay, Section III.D.3).
Classification requires defining likely classes and describing indicator ranges among proposed
classes. Classification should progress using data from waterbodies that are unimpaired. Splitting
into more refined classes has possible drawbacks. There may not be enough sites to perform a
statistical evaluation or enough resources to collect data from the field. Too many classes may
make it difficult to know which criteria to apply in a particular case. Classification using
stochastic or deterministic models does not require as many data points per class as classification
methods based exclusively on statistical analysis of field data. However, the cost (in terms of
dollars and time) of initiating a new model development effort may be excessive.
33
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An ideal indicator is
measurable, quantifiable,
reproducible, and
comparable.
Framework for Developing SABS Water Quality Criteria U.S. EPA
III.C.2. Indicators - Exposure and Response Measurements
The selection of indicators is a major element within the Framework and is a key step in defining
impairment and monitoring management actions. When attempting to meet WQS, resource
managers rely upon narrative or numeric criteria to determine whether a designated use is being
protected. In many cases, resource managers select specific, measurable variables, or indicators,
to express a narrative standard in terms of the pollutant of
concern. A numeric target value for the variable is a
threshold between the impaired and unimpaired designated
use of the waterbody. The most effective indicators are
quantitative measures that can be used to establish the
relationship between pollutant sources and their impact on
water quality.
There are many indicators of SABS-caused impairment. Most fall into one of five discrete
categories: (1) water column measures, (2) substrate measures, (3) channel/bathymetric
characteristics, (4) biotic response measures, and (5) functional measures. The first three
categories are types of exposure measures; the last two are measures related to effects and
designated uses. Indicators should be appropriate to the waterbody type (Table 4) and allow
analysts to efficiently discriminate impaired from unimpaired conditions.
When adopting a particular indicator or suite of indicators, it is important to consider various
technical, practical, and socioeconomic considerations. An ideal indicator is measurable,
quantifiable, reproducible, and comparable. In addition, it is important to weigh the costs of
obtaining data compared against the value of the information produced. Each potential indicator
has specific measurement methods, appropriate applications, precedent uses as indicators, and
ranges of possible criterion values. When applied properly and judiciously, indicators can
provide the requisite understanding of SABS processes to show the link to biological resources
or designated uses and to identify the management actions with the highest likelihood of success.
In practice, selection of appropriate indicators will require investigation into measurement
techniques, specific applicability, and performance characteristics that cannot be completely
reviewed in this Framework.
Exposure Measures
There are three main classes of sediment-exposure indicators: (1) water-column measures, (2)
substrate measures (including bedload), and (3) channel/bathymetric characteristics. Each can be
characterized by one or more metrics tailored to the specific indicator. For example, metrics
associated with suspended sediment and turbidity tend to be more effective in identifying water-
column impairments in still or slow-moving water, such as in lakes, estuaries, and some coastal
areas, and some rivers at sluggish flows. In faster-moving waters, bedded sediments and bedload
may have relatively greater impacts on habitat and biota than water column impairments. This is
in part due to the episodic nature of suspended sediment flux in faster-moving waters, in which
most aquatic organisms have adaptive characteristics for withstanding short-term exposures to
turbid waters.
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Table 4. Suitability of SABS indicators by waterbody type. • = appropriate application, ® =
limited applicability, O = not appropriate
Rivers and
Streams
Lakes, Ponds,
and Reservoirs
Wetlands
Estuaries
Coastal Marine
Waters
Suspended Sediment
Turbidity
Total Suspended Solids
Suspended Sediment
Concentration
Light Penetration
Water Clarity
•
•
•
®
•
®
®
•
•
•
®
®
•
®
®
®
®
®
•
•
®
®
®
®
•
Bedded Sediment
Bedload Sediment
Percent fine sediment at
surface
Percent fine sediment at
depth
Sedimentation rate
Embeddedness
Suspendable Solids
Particle size distribution
Particle size geometric
mean
Substrate Stability
Relative Bed Stability
Bottom Deposit Depth
Residual Pool Volume
Bank Stability
Waterbody Dimensions
Bathymetry
Riffle/Pool ratios
Gradient
Sinuosity
Incision
•
•
•
•
•
•
•
•
•
•
®
•
•
•
•
•
•
•
•
0
•
®
•
•
•
•
•
®
O
•
O
•
•
•
0
O
0
0
0
•
•
•
O
®
•
•
O
O
•
•
•
•
•
0
®
0
•
®
•
•
•
®
•
®
®
®
O
•
®
•
•
•
0
O
0
0
0
O
0
®
O
0
O
0
®
O
•
O
0
O
•
0
O
0
0
Response Indicators
Biological Measures
Eroding Banks
Reservoir Filling Rate
Filter Clogging
•
•
•
•
•
•
•
•
•
O
•
O
•
•
•
O
•
•
0
O
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Suspended sediments reduce water clarity and light penetration. The particles can be abrasive,
clogging biological and man-made filters. If the particles are organic or algal, they may also alter
water quality via decomposition and shift in community structure (such as an altered food
source). Suspended sediments also have the potential to settle. No single indicator measures
exposures that would be adequate to reflect all of these effects. Therefore, it may be judicious to
measure a suite of indicators.
Physical measures associated with substrate or bedded sediments include embeddedness, percent
coverage or percent volume of fine sediments, and substrate stability indices. Bedload transport
is largely responsible for changes in channel morphology and habitat.
Channel/bathymetric characteristics are measures associated with the morphological stability that
change near-shore or wetted basin physical characteristics. They can reveal effects of erosion,
transport, and deposition on channel morphology and habitat conditions. Channel/bathymetric
characteristics can be used to infer past, present, and potential future erosional and depositional
processes. A process-based understanding of the fluvial system can lead to development of
causative links to management practices aimed at remediation of sediment problems.
Biotic Response Measures
The existing biomonitoring programs in many states, tribes, and territories sample aquatic life
that may be sensitive to SABS. Biological metrics can provide discriminating indicators for
SABS associated with impairment of the aquatic conditions. Aquatic organisms may be
measured in the water column as well as in or near the sediment or substrate. Because the
presence, diversity, and productivity of aquatic organisms can be used to infer habitat suitability,
biological indicators can complement physical
exposure indicators in SABS criteria
development as well as provide information
on overall biological integrity. Biotic
responses may be measured or calculated in
numerous ways, including metrics of taxa
assemblages or presence and abundance of
specific taxa such as threatened, endangered,
invasive, or exotic species. For example,
researchers have assigned sediment tolerance values to specific organisms in stream
environments, allowing calculation of metrics that may prove uniquely responsive to SABS
effects (Relyea et al. 2000; Yuan 2006).
It is important to note that biological measures may not always indicate or diagnose SABS
impairment. An excess of SABS may result in a predictable change in the biota. However, any
given change in the biota may not be attributable definitively to SABS. SABS is only one of
many stressors in aquatic systems that can cause similar responses in the biota.
Biological metrics can be
discriminating indicators for SABS
associated with impairment of the
aquatic conditions though they
may not be sufficiently specific for
diagnosis of SABS impairment.
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III.C.3. Integration and Synthesis of Multiple Methods
One conclusion of the U.S. EPA Science Advisory Board was that no single method would
suffice for complete criteria development in every situation and that multiple methods applied
simultaneously (synthesized) may be more appropriate for criteria development. This conclusion
recognizes the complexity of natural SABS settings, the variable applicability of methods in
those settings and the flexibility required by states, tribes, and territories to use their SABS data
to their best advantage. Various methods are described in Section HID, organized by groupings
that are appropriate for measuring and calculating SABS indicators, for classifying waterbodies,
and for developing associations between indicators of SABS with indicators of designated uses.
A key element is that the methods and resulting evidence are best used in combination. Results
from different methods can provide independent collaboration of scientific findings. They are
best applied when interpreted in terms of a watershed or interconnected waterbodies. In other
words, the evidence should be evaluated in such a way that upstream criteria protect not only the
immediate waterbody but downstream designated uses as well. Examples of how these methods
could be used in combination (a synthesis of methods) are described in Section III.E.
III.D. Methods Applicable within the Framework
At this time, U.S. EPA has been examining various methods for use in developing water quality
criteria for SABS that are applicable within this Framework. Some of these methods are
presented here as they relate to three activities: (1) measuring suspended and bedded sediments,
(2) evaluating water body classification, and (3) associating suspended and bedded sediments
with designated uses. These methods are generally applicable in steps 3, 4, and 6 of the
Framework, respectively. The presented statistical methods can often be applied to more than
one activity. Some methods are well developed, whereas, others may have been tested in only
certain classes of waterbodies. All these methods need to be evaluated and applied to local
situations. The Framework is flexible, allowing many variations in the combination of indicators,
classifications, and analytical methods. This flexibility allows resource managers to customize
the criteria development process to specific needs and capacities. It also encourages justification
for the choices made in customizing the process. While these methods are explained
individually, in practice they will be applied simultaneously or in combination.
(1) Measurement of Suspended and Bedded Sediment (Step 3)
• Readily Available Measures
Sediment Transport Curves
Relative Bed Stability
(2) Waterbody Classification (Step 4)
• Empirical Classification (Reference Condition)
Fluvial Geomorphology
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(3) Associating Suspended and Bedded Sediment with Response Indicators (Step 6)
• Controlled Experiment
• Field Observational Studies
- Percentile Analysis (including Reference Condition Methods)
- Exposures and Effects Analysis
- Conditional Probability Analysis
• Waterbody Use Functionality
Brief examples of some of these methods are included with the descriptions below. The
examples use data sets generously provided by the state of Oregon, the Chesapeake Bay
Program, and the U.S. EPA Environmental and Monitoring Assessment Program (EMAP). These
example analyses demonstrate that acceptable data sets may be already available or can be
developed within a few years.
To select a SABS indicator value that is protective of a designated use, common sense and clear
thinking are indispensable. This section will provide some analytical methods and a few tips, but
the investigators should provide the clear thinking and rationale for each of their choices.
Choices of indicators and thresholds require reliance on assumptions regarding mechanisms,
modeled relationships, bias, measurement precision, and other analytical elements. Selection of a
protective response level requires a trade-off between full protection and what the public will
support and implement. These assumptions and compromises should be examined transparently
and often during the criteria development process. The four elements that have the strongest
impact on criteria development include selection of endpoints and measurements, classification,
methods for demonstrating associations, and selection of criteria values.
Selection of endpoints and measurements should support the goal of showing a causal
relationship between SABS and an impaired designated use. The most mechanistically plausible
relationships are those that are specific rather than general, rely on few classifications, and make
direct association with few intervening steps.
• Specific indicators are better than general ones. The association of stoneflies, a type of
benthic invertebrate, and silt free substrates is more definitive than an invertebrate index
or even the number of ephemeroptera, plecoptera, and trichoptera (EPT) taxa with silt
free substrates. This is because most stoneflies have very narrow habitat and water
quality requirements, whereas benthic macroinvertebrates occupy many niches. EPT, a
metric of mayflies, stoneflies and caddisflies, includes mayflies that burrow in sediment
and caddisflies that thrive on fine particulate matter. Indices are designed to detect a wide
range of causes rather than impacts of SABS alone.
• Indicators are better if they rely on few classifications. Relative Bed Stability is a
measure that inherently uses channel characteristics in calculation of the metric. Because
the channel characteristics incorporate the same determinants that might be used to
classify sites, more sites can be lumped into a single class, with individual site
differences accounted for in the metric. This reduces the chances of a categorical error in
site classification, though some gross and easily recognized class may still be needed
(e.g., wadeable streams within a single ecoregion).
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Framework for Developing SABS Water Quality Criteria U.S. EPA
• Indicators with direct associations are better than those with indirect pathways. An
association of suspended sediment concentration (SSC) and extent of eelgrass bed is
more readily demonstrated than SSC and blue crab catch. This is because the catch is
dependent on effort as well as abundance, and sediment does not directly affect the crab
as much as it affects eelgrass beds. Therefore, there is an indirect association rather than
a direct one. In a conceptual model there would be multiple boxes and arrows to make
the connection.
Classification is a statistical method for removing variation due to factors other than SABS that
affect the SABS and response indicators. It is most appropriate and necessary for observational
field survey data. Classification may be unnecessary if assessment endpoints are specific. If field
data are plotted for the presence of brook trout and total suspended solids, the classification is de
facto for those streams with brook trout. Classification is explicit in controlled experiments,
where the laboratory conditions or experimental setting defines the class. Classification is
looking as much for similarities as it is for differences. No two sites are the same. However, by
placing different sites in the same class, we are recognizing their relative similarity among all
sites in the data set. In doing so, we allow for potential bias and error (some sites are not as
similar as others) and simplify criteria application (by not expecting definition of site-specific
criteria).
Methods for demonstrating associations between the SABS measurement and the response
measurement can show that an adverse effect is likely to occur given some level of SABS. To
demonstrate an association, it is recommended that one use at least two methods that rely on
different assumptions, different data sets, and different statistical methods. For instance, results
from controlled experiments can be compared with characterizations based on independent field
observations.
When SABS are characterized with respect to reference sites or acceptable physical conditions, it
is possible to describe deviation from the reference conditions in terms of SABS measurements
alone. These deviations may be interesting and perhaps even indicate increased human activity in
the watershed, but it is possible that they are also insignificant to the function and attainment of
the designated use. Until the SABS indicators are linked to the response indicator (selected
because it represents the designated use), changes in the SABS indicator cannot be interpreted in
the criteria setting context.
Selection of a criterion value is often a value judgment that can be somewhat distanced from
scientific methods, especially when clear inflection points are not evident in stressor-response
curves. Despite the many uncertainties, one can determine defensible criteria when different data
sets and different types of associations support or corroborate one another. Examples of different
types of evidence include:
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Framework for Developing SABS Water Quality Criteria U.S. EPA
Plausible effects based on laboratory and field exposures
• The interactions among gradient, flow, substrate, and other variables
• The connectedness of abiotic and biotic components in ecosystems
Characteristics of chronic and episodic exposures to SABS
Levels of SABS in upstream locations and how they relate to downstream resources
with different tolerances to SABS.
III.D.l. Measurements of SABS; Applicable in Step 3 of the Framework
Measurements are usually required for sources, exposures, and responses of SABS. The
mechanistic pathways through which sediment can affect biological assemblages can be depicted
in conceptual models. Associations between indicators that are close together in the conceptual
model (only one arrow connecting) are easy to demonstrate because there are few unmeasured
variables that will affect the interaction. Keep in mind that the measurements that are selected
will need to be associated with a designated use so that an effect level can be demonstrated.
Readily Available Measures
Some of the technical issues and considerations for selecting measurements of SABS were
described as part of steps 2, 3, 4 and 5 and in Section III.C.2. Table 4 lists possible indicators
sorted by their usefulness in measuring suspended or bedded sediment and their applicability to
waterbody type. Naming conventions are listed in ASTM's Terminology for Fluvial Sediment, D
4410-98 (2005), which contains the widely accepted definitions for riverine and most other
freshwater environments. Of the five fundamental sedimentation methods listed by ASTM D
4410-98, erosion, transportation, and deposition are relevant to the SABS guidelines.
Approaches are also reviewed and published by ASTM (2005), for example, turbidity (ASTM D
1889-00) and suspended sediment concentration (ASTM D 3977-97). The USGS has been a
leader in the development of reliable measures of the fluvial-sediment method and their Web site
is a good place to find useful methods for measuring SABS
(http://water.usgs.gov/osw/techniques/sediment.html).
The mechanistic pathways through which sediment can affect biological assemblages are
depicted in several conceptual models (Appendix F). For suspended (Model 1) and bedded
sediments (Model 2), boxes are highlighted in grey that directly measure characteristics of
sediment that affect aquatic life. For instance, Secchi distance could be selected to measure light
penetration. Substrate stability and substrate movement and scouring are more dynamic
processes that can be inferred, measured, or modeled. Land cover/land use and in-stream factors
that alter sediment supply are depicted in Model 3. Whichever SABS measurements are selected
should be associated with a response variable so that an effect level can be estimated.
Associations between indicators that are directly connected conceptual model are easier to
confirm because there are fewer unmeasured variables that will affect the interaction. The
following two sections describe two methods, sediment transport curves and Relative Bed
Stability (RBS), that may be less well known than more commonly used measures of SABS.
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Sediment Transport Curves
Sediment transport curves (STC) are graphics for displaying the relationship between measured
sediment values (either bedload or suspended sediment load) and measured or expected flow or
discharge. Departure of measured sediment values at a given flow from expected sediment loads
may help indicate the type and magnitude of impairment and may help a resource manager
identify targets for reestablishing more stable sediment conditions for the waterbody.
Stream stability shifts are reflected in STCs, also termed sediment rating curves, where measured
sediment values are regressed against measured discharge. The upward shift in the slope or
intercept values of the STC are due to increased sediment supply resulting from a variety of
sources. The upward shift in the STC exponentially increases the sediment yield for selected
increments of stream-flow. Land uses that increase stream-flow magnitude and duration can be
instrumental in accelerating "flow related" increases in sediment. Figure 5, below, provides an
example of STCs for two rivers of different channel type, sediment budget, and stability.
100000 -|
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Figure 5: Suspended sediment transport curves for South Fork, Forked Deer and Hatchie River
(from Simon, 1989).
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Framework for Developing SABS Water Quality Criteria
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Although understanding of STCs is limited, they may have some application potential related to
criteria if reference relationships can be developed. Suspended sediment concentration, for
example, is often correlated with flow rate, and the literature offers some evidence that sediment
transport coefficients and flow are predictably interrelated within a given region (Hawkins
2002). In an examination of STCs for suspended sediment and bedload of 160 Rocky Mountain
rivers and streams, Troendle et al. (2001) were not able to show differences in dimensionless
sediment transport attributable to geomorphic channel type, but the analysis did reliably detect
departure of generally unstable stream types as a group from values expected of stable channels.
Ongoing work in developing and testing reference STCs continues mainly in the Rocky
Mountain States with some investigations in other regions of the United States and Great Britain.
Preliminary findings suggest that channel type plus stability may reveal a stronger relationship
than channel type alone.
Relative Bed Stability
Relative bed stability (RBS) is a comparison of bed
at bankfull flow, which is proportional to the
estimated shear stress at bankfull flow. Although
many human activities directly or indirectly alter
stream substrates, streambed particle sizes also
vary naturally in streams with different sizes,
slopes, and surficial geology (Leopold et al.
1964; Morisawa 1968). The size composition of
a streambed depends on the rates of supply of
various sediment sizes to the stream and the rate
at which the flow takes them downstream
(Mackin 1948). Topography, precipitation, and
land cover influence sediment supply to streams,
but the source of sediments is the basin soil and
geology, and supplies are greater where these
materials are inherently more erodible.
substrate size divided by the mobile diameter
Relative Bed Stability is an index of
substrate mobility with respect to
physical characteristics of the
waterbody. Substrates are
expected to move a calculable
degree for each natural hydrologic
and geomorphic condition. When
observed substrate mobility is
considerably greater or /ess than
the predicted, human-induced
SABS stresses are indicated.
Once sediments reach a channel and become part of the streambed, their transport is largely a
function of channel slope and discharge during floods (in turn, discharge is largely dependent
upon drainage area, precipitation, and runoff rates). For streams that have the same rate of
sediment input from watershed erosion, steeper streams tend to have coarser substrates than
those with lower gradient, and larger streams (because they tend to be deeper) have coarser
substrates than small ones flowing at the same slope. However, this transport capability can be
greatly altered by the presence of such features as large woody debris and complexities in
channel shape (sinuosity, pools, width/depth ratio, etc.).
The combination of these factors determines the depth and velocity of streamflow and the shear
stress (erosive force) that it exerts on the streambed. By comparing the actual particle sizes
observed in a stream with a calculation of the sizes of particles that can be mobilized by that
stream, the streambed stability can be evaluated. Furthermore, the degree to which streambed
instability is due to accumulation of fine sediments can be evaluated, and watershed data can be
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Framework for Developing SABS Water Quality Criteria U.S. EPA
examined to infer whether the sediment supply to the stream may be augmented by upslope
erosion from human activities and natural disturbances.
RBS is calculated as the ratio of observed bed substrate particle diameter divided by the
calculated "critical" or mobile particle diameter (Dingman 1984; Gordon et al. 1992). RBS is the
inverse of the substrate "fining" measure calculated by Buffington and Montgomery (1999a,b)
The RBS is conceptually similar to the "Riffle Stability Index" of Kappesser (2002), the bed
stability ratio discussed by Dietrich et al. (1989), and the ratio of critical near-bed water velocity
to actual near-bed velocity defined by Jowett (1989).
When evaluating the stability of whole streambeds (vs. individual bed particles), observed-bed
substrate is typically represented by the average diameter of surface substrate particles (e.g., D50
or the geometric mean). The widely accepted procedures for measuring substrate particle size
distribution in a stream channel typically employ a systematic "pebble count" as described by
Wolman (1954). For calculating critical (mobile) substrate diameter in a natural stream, it is
necessary to estimate average streambed tractive force, or shear stress, for some common
reference flow conditions likely to mobilize the streambed. Bankfull discharge is typically
chosen for this purpose although this is more appropriate for gravel-bed streams than for "live-
bed" streams such as naturally sand-bedded streams that transport bedload at lower flows.
One method for estimating the critical substrate particle diameter in a stream is based on
sediment transport theory (e.g., Simons and Senturk 1977), which allows an estimate of the
average streambed shear stress or erosive tractive force on the bed during bankfull flow. When
developing this method, EMAP researchers (Kaufmann et al. 1999; Kaufmann and Larsen 2006)
used physical habitat measurements collected in synoptic surveys (Kaufmann and Robison 1998)
to estimate the channel characteristics affecting bed shear stress at bankfull flows. These field
measurements include bankfull channel dimensions, slope, channel complexity, and large woody
debris. Using channel and substrate data as described above, EMAP researchers modified the
Dingman (1984) critical diameter calculation to accommodate losses in shear stress resulting
from large woody debris and channel complexity (Kaufmann et al. 1999). The reductions in
shear stress and, therefore, critical diameter, caused by these roughness elements allow fine
particles to be more stable in a stream of a given slope and depth.
RBS values in EMAP sample streams range from 0.0001 to 1000. A high positive value of RBS
(e.g., 100-1000) indicates an extremely stable, immovable stream substrate like that in an
armored canal, a tailwater reach below a dam, or other situations where the sediment supply is
low, relative to the hydraulic competence of the stream to transport bedload sediments
downstream (Dietrich et al. 1989). Very small RBS values (e.g., 0.0001-0.01) describe a channel
composed of substrates that are frequently moved by even small floods.
Scientists hypothesize that given a natural disturbance regime, sediment supply in watersheds not
altered by human disturbances will be in approximate long-term dynamic equilibrium with
transport. Kaufmann et al. (1999) argued that, on a regional scale, streams will adjust sediment
transport over time to match supply from natural weathering and delivery mechanisms driven by
the natural disturbance regime. Consequently, for streams with sediment transport limited by
competence (critical shear stress) rather than total capacity (stream power), RBS in appropriately
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Framework for Developing SABS Water Quality Criteria U.S. EPA
stratified regional reference sites should tend towards a range characteristic of the climate,
lithology, and natural disturbance regime (Kaufmann and Hughes 2006).
In support of this assertion, Stoddard et al. (2005) found that Logic (RBS) in reference sites
differed among aggregated ecoregions of the Western U.S.A., where, for example, the 25th
percentiles of reference sites in mountain ecoregions ranged from -0.6 to -1.1 compared with -1.7
for plains ecoregions. RBS values considerably lower than 1.0 (LogioRBS «0} may be the
norm in streams draining watersheds relatively undisturbed by humans if those streams are
characterized by natural features (lithology, soils, topography, climate, and vegetation) that are
conducive to high rates of sediment supply and transport.
In particular, naturally fine-bedded streams with unstable beds (i.e., LogioRBS «0), would be
expected to drain relatively undisturbed watersheds where streambed textural responses are
constrained by a lack of coarse particle sizes in sediment inputs from the drainage area. In
addition, RBS in streams with minimal human disturbance might be expected to differ
systematically across a geomorphic gradient from streams with transport dominated by bedload
to those dominated by suspended load - generally this occurs in a downstream direction in the
stream continuum. Logic (RBS) values considerably lower than zero may be expected in these
examples of naturally fine-bedded alluvial streams where transport is limited by average stream
power rather than bankfull shear stress.
Alternate hypotheses concerning the expected values of RBS using synoptic data from EMAP
surveys are being evaluated. As the EMAP approach for assessing excess streambed
sedimentation in low-gradient, fine-bedded streams and rivers is refined, it may be necessary to
modify the method (currently based on the competence of bankfull floods to move given sizes of
particles). For these waters, it is useful to estimate bed stability in terms of the proportion of the
year that the bed is in motion.
In watersheds where sediment supplies are augmented relative to a stream's bedload transport
competence, evidence will likely show an excess of fine sediments (Dietrich et al. 1989). Very
small RBS values (e.g., 0.0001- 0.01) indicate excessive amounts of fine particles compared with
expected values in most relatively undisturbed watersheds. Such evidence of excess fine
sediments in the stream bed (RBS«1) typically occurs when land use activities increase
hillslope erosion (Lisle 1982; Dietrich et al. 1989; Lisle and Hilton 1992), especially when there
is also damage to riparian vegetation.
In streams draining basins of equal erodibility, RBS values should decrease in proportion to
increases in sediment supply above that provided by the natural land disturbance regime. To the
extent that human land use increases sediment supply by land erosion within regions of relatively
uniform erodibility, RBS of streams in surveys should be inversely proportional to basin and
riparian land use intensity and extent (Kaufmann et al. 1999; Kaufmann and Larsen 2006).
Finally, as the basin lithology within a geoclimatic region becomes more erodible, the RBS
steeply declines with progressive disturbance (Kaufmann and Hughes 2006). As demonstrated
for streams in the Pacific coastal region by Kaufmann and Larsen (2006), this means that any
given amount of land use disturbance is expected to augment sediment supplies to a greater
degree in basins underlain by erodible rocks than by more resistant rock (Figure 6).
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Framework for Developing SABS Water Quality Criteria
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1-
I
m -i
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= D
f.
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Hard Volcanic Geology
i
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ft
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t
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Soft Sedimentary Geology 1 U
123456? 123450?
Basin and Riparian Disturbance Index
Figure 6 RBS in streams of the Coast Range ecoregion of Oregon and Washington as a function
of a relative disturbance gradient in hard volcanic and soft sedimentary geologies (Kaufmann et
al. 2004).
Once the degree of sedimentation is estimated
for sample sites, deviations from expected
values can be examined in relation to key
aquatic species, guilds, or biotic assemblages
(algae, macroinvertebrates, fish, rooted
aquatic plants). A relationship observed
between RBS and the biotic metric is positive
evidence that excessive fine sediments are
affecting aquatic life uses (Figure 7) and that
the RBS indicator may be a reliable basis for
establishing SABS criteria. Scatter at the low
end of the plot may be due to poor biological
conditions that are attributable to stressors
other than RBS. These patterns are consistent
with the hypothesis that sediment is limiting
biota when the upper limits of the plot are
showing a response. In large, representative
surveys of sites from across an ecoregion, the
upper limits represent the best biological
conditions that can be expected for the
corresponding RBS values.
40
w «rt
0 JO
c
o
S
CO
Q_
LLJ
20
10
• XXX
• X
-4-3-2-1 0 1
Log (RBS)
Figure 7. RBS in streams of the Coast Range
ecoregion in relation to EPT taxa richness
(Kaufmann et al. 2004). Data points represented
with an "x" have 20% or more bedrock at the
site. Circles are sites with less than 20% bedrock.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
III.D.2. Waterbody Classification: Applicable in Step 4 of the Framework
Sediment is a natural component of aquatic ecosystems. Some ecosystems, by their very nature,
have evolved under conditions of extremely low sediment supply and others with a lot. Some
systems evolved with unstable substrates and others with stable substrates. Some experience a
steady supply of sediment and others have periods of sediment starvation and periods of
sediment inundation. It doesn't make sense to apply very low sediment criteria to a system that
would naturally experience a heavier supply of sediment. Similarly, it would be inappropriate to
permit high levels of fine sediments in a system that is normally characterized by cobbles or
bedrock substrate. Therefore, aquatic systems with similar sediment regimes need to be classified
and sorted into similar categories or arranged along a predictable continuum so that appropriate
sediment criteria can be developed and applied.
The natural sediment regime for a waterbody can be estimated based on geographical,
geomorphic, and climatic characteristics of waterbodies in a nearly natural state (reference
conditions). We refer to this method as the Empirical Classification Method. The Fluvial
Geomorphology Method \$ based on model building and field observation and is useful for
selecting stable sites and avoiding those in successional states.
Empirical Classification
Empirical classification refers to an investigation of SABS conditions that can be expected in
systems that are functioning in pristine or minimally disturbed watersheds. The expectations are
not uniform across all systems. Rather, they vary according to variations in underlying geology,
soil characteristics, climate, vegetative types, and other natural determinants. At the heart of
empirical classification is the identification of the natural determinants that are most influential
to variations in SABS conditions. Once determinants are identified, they can be used to describe
distinct site classes or a continuum of classes. The SABS conditions observed in those sites with
minimal landscape disturbance become the standard to which any other site within the class can
be compared.
Classification techniques could be
used to identify degraded site classes
At the heart of empirical classification is
the identification of the natural
with respect to SABS. However if the determ,nants that are most inf,uentia, to
differences attributable to natural . 0/1(-,0
variation were not first identified, it variations in SABS Conditions.
would be difficult to distinguish true
degradation from acceptable natural differences. For this reason, the classification techniques are
best applied in sites with no known impacts or few impacts if non-impacted sites are nonexistent.
Sites with few or no impacts are generally termed reference sites as these are the sites to which
we refer when defining unaltered (or best observable) SABS conditions.
The first step in empirical classification is identifying wholly natural or minimally disturbed
reference sites. After removing sites with known impacts, it is assumed that any observed
variation in SABS conditions is due to natural factors. The next step is to explain the observed
variation in SABS conditions in terms of natural determinants. The step described above
regarding definition of reference SABS conditions and comparison to those conditions for
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Framework for Developing SABS Water Quality Criteria U.S. EPA
determination of imbalances is really beyond the scope of the classification exercise but is
addressed in subsequent sections. If analytical anomalies are discovered as indicated in step 6 of
the Framework, it may be necessary to return to this step and reclassify.
Identifying Reference Sites. Sediment supply and hydrology respond to most landscape
modifications. Thus, contemporary land use data are important in identifying reference sites.
Current land use data are available for most of the contiguous U.S. (e.g., LAND SAT), and the
technology is advancing rapidly so that more contemporary data are being made available
rapidly. Historic land uses should also be considered when selecting sites with nearly natural
sediment regimes, especially for bedded sediments. The time required for stream channels to
return to equilibrium after landscape alteration is on a scale of decades to centuries, if not longer
(Trimble 1974; Schumm 1977; Brunsden and Thornes 1979; Trimble 1999).
Streams in catchments that have experienced historic landscape disturbance by human activities
for an extended time or intensity may still be undergoing geomorphic readjustment. Unless this
is an acceptable class in itself, these sites should be excluded from the reference data set. Other
waterbody types may also require considerable time to reach equilibrium after disturbance in the
watershed. Historic land use data can often be reconstructed from tax data, historic photographs,
and historic diaries. Techniques have been developed by fluvial geomorphologists to identify or
infer past land use disturbance (e.g., dendrochronology, sediment profile dating, floodplain and
terrace coring, etc.) (Knighton 1984). These can be used to investigate past impacts within a
potential reference catchment though they may be prohibitive in terms of cost, time, and
expertise.
Modifications within the channel or waterbody are also important for defining sites with nearly
natural sediment regimes. The presence of dams, channelization, dredging, and diversions will
all affect in-stream sediment dynamics. Dams alter the sediment supply and hydrology of rivers
and, therefore, have dramatic impacts on sediment dynamics, often for long distances
downstream (Walker 1985; Reiser et al. 1989; Gregory and Madew 1982; Gordon et al. 1992).
Channelization, dredging, and other channel modifications alter stream channel geometry
because channel geometry is related to stream power and, therefore, sediment transport, sediment
and channel features can migrate downstream and upstream following channel impacts, causing
long-term channel instability and altered sediment dynamics (Miller 1991; Simon and Hupp
1992). Water diversions alter the hydrology of receiving streams and the resulting reduction in
flow can lead to channel destabilization by sediment accretion.
A deliberative process for identifying reference sites includes listing all conditions that should be
met for a site to be designated as reference. Criteria should address measures that are
independent of the SABS and response indicators for which criteria are being developed. Persons
familiar to the region are most knowledgeable about what factors might be used.
The following are examples of possible criteria for selecting reference streams based on
information about land use/land cover and stream morphology. Obviously, criteria would be
differently customized for other waterbody types and prevailing regional stressors.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
• Upwards of 95% of the watershed is in natural and undisturbed cover.
• Historical land uses did not disturb more than 10% of the land in the last 50 years or more
than 25% of the land in the last 100 years.
• Activities in the portions of the watershed are not in natural cover or are not in sediment
generating land uses, such as mining, clear-cut logging, or cultivation on steep slopes.
• Roads cross the stream once per kilometer or less and do not dominate riparian areas.
• The stream channel is not altered by dams, channelization, dredging, or diversions within
10 miles upstream of the sampling location.
• The stream channel was not altered in the last 50 years.
• Stream channel is not in an erosive successional stage.
Reference Site Identification in Oregon
The Oregon Department of Environmental Quality (ODEQ) is in the process of establishing
SABS criteria in wadeable streams. As a first step in the process, reference sites were
identified using multiple types of quantitative and qualitative information (Drake 2004). To
identify reference sites, ODEQ used GIS analysis and aerial photos or thematic mapping
data, or both, to pre-screen areas and find watersheds with minimal human disturbance.
Using best professional judgment (BPJ), resource specialists edited the list of potential sites
within unimpaired areas. A Human Disturbance Index (HDI) was developed for the
candidate reference reaches and watersheds based on reach level observations and
watershed-scale geographic information. The HDI score was used to help select and rank
reference sites in a basin or region. Verification of reference sites includes evaluating
physical habitat and biological and water quality data. Outlying data may indicate problems
that would exclude sites from the reference set. After identifying reference sites, ODEQ
went on to investigate differences in SABS indicators among potential site classes. The
studies revealed that ecoregions are reasonable determinants of natural SABS variations.
Identify Potential Class Determinants. The naturally occurring factors that can potentially
affect SABS supply make a lengthy list. Well established empirical and theoretical relationships
describe the effects of landscape topography, climate, and geology (including soil properties) on
sediment dynamics (examples in Knighton 1984 and Gordon et al. 1992). Classification
determinants may include underlying geology, soil type, gradient, hydrology, climate,
topography, and catchment geomorphology. Determinants that are substantially influenced by
human activities, such as land use or vegetative cover, should be avoided because their use
would introduce the risk of defining classes based on degrees of impact, not natural variation.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
Since many state and federal biological monitoring programs (e.g., state biocriteria programs,
EMAP, NAWQA) have identified reference sites and now have sizable reference databases, it
may be possible to mine the existing regional reference data, augmented with basin-level data as
necessary, to examine preliminary models. In some cases, EMAP and NAWQA have sufficient
data, including extensive sediment, physical and hydrologic data, to develop good predictive
models of reference sediment conditions. Many of the state programs, however, do not collect
hydrologic or sediment data other than that necessary to conduct qualitative habitat assessments,
and their reference sites may need to be revisited to collect the relevant data.
Data on soils, including factors such as soil type, texture, erodibility, and porosity, would be
ideal for determining classes. Soil maps containing such information are available for much of
the U.S. and are maintained by the Natural Resources Conservation Service (NRCS). Climate
data, including precipitation and hydrology are also desirable for building predictive models.
Climate data are available for most of the U.S. through NOAA and state climate offices and are
often accessible via the Internet. Hydrologic data are maintained by several agencies, including
the USGS and state geological surveys. However, detailed hydrology is only available for
gauged catchments and may have to be modeled for others. A variety of hydrologic models can
be used as necessary (Gordon et al. 1992), those predicting base-flow and peak-flow perhaps
being most useful. Catchment geomorphology is necessary, including data on topography and
catchment size. These data are readily extracted from surface topographic maps using GIS
software.
If there is an absence of a robust data set for reference sites across the range of waterbodies in a
region, then the suspended sediment regime may be modeled from theoretical principles that do
not require detailed field data. Some validation would be necessary for acceptable uncertainty in
the results. Theoretical models could be used to predict sediment characteristics for specific sites
or site classes and then used to classify streams based on the modeled sediment regimes.
Classification using existing stochastic or deterministic modeling does not require as many data
points per class as classification methods based exclusively on field data. However, the cost (in
terms of dollars and time) of initiating a new model development effort may be prohibitive.
Establish Meaningful Classes. The challenge of defining classes is to achieve a balance
between accounting for the natural variation in SABS among individual waterbodies and finding
some commonalities among waterbodies. If this is not done, each waterbody will have its own
SABS criteria, which can become cumbersome and costly. Too many classes may make it
difficult to know which criteria to apply in a particular case. These types and amounts of relevant
data may limit classification analysis. There may not be enough sites to define multiple classes or
enough resources to collect additional data from the field. Five reference samples per discrete
waterbody type is an absolute minimum reference data set; however, the small sample set will
have low statistical power to detect differences. A data set of 30 samples per waterbody class is
desirable but often unobtainable (Elliott 1977).
The impacts and behavior of suspended and settled particles have different modes of action and
may require separate classification analyses. For that matter, each SABS indicator may require a
separate analysis although multivariate analysis would allow consideration of multiple SABS
signals in a single analysis. If discrete classes are to be defined (as opposed to a continuum), then
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Framework for Developing SABS Water Quality Criteria
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the investigator should define the categorical parameters for each grouping of sites, based on one
determinant or a combination of determinants. Exploration of potential groupings is difficult to
automate, so a priori hypotheses of reasonable classes should be tested first, and further
exploration should be guided by the preliminary results.
The full range of conditions can be evaluated rather than categorically defining classes. For
instance, basin size as a classification variable need not have arbitrarily sized bins to define
distinct classes. Rather a continuous range of stream sizes can be modeled if there is sufficient
power to predict SABS conditions relative to stream size. Often, several variables have more
predictive power than a single variable, in which case multivariate analysis is required.
If identifiable groups of sites are found to be different then a decision must be made whether to
separate the groups or retain a single group. The example in Figure 8 illustrates that groups can
appear different but closer examination suggests that they should remain a single classification.
The magnitude of difference between groups, sample sizes, and uncertainty will affect the
decision. Serious consideration should be given to the possibility that any statistical difference is
due to difference in disturbance between the groups rather than different sediment supply and
transport regimes. For example, reference streams with erodible soils and resistant soils may
appear to be reasonable classes of streams; however, both groups have similar levels of turbidity
under least disturbed conditions (Figure 8). This similarity could be misinterpreted if the criteria
for reference sites are less stringent; thereby allowing a few disturbed sites into the "reference"
group.
Reference vs. Non-reference Turbidity by LEthology
E rod \ \> \ e Re si sta n t
Reference Sites
n Median FH 25%-759
Erotli ble Resistant
Non-reference Sites
Non-Outlier Range
Figure 8. Turbidity in Oregon streams by reference status and erodibility (Rosetta 2005).
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Framework for Developing SABS Water Quality Criteria U.S. EPA
Empirical classification is based on appropriately applied statistical methods that test whether
two or more groups are likely to be similar or different. The basic premise is that the sediment
indicator of interest will behave similarly in similar systems and differently in different systems.
Within sites of the same class, SABS indicators are expected to have similar natural levels.
Therefore, a single criterion can be defined to illustrate the natural expectations within each
distinct class. Characteristics of the reference indicator distribution such as central tendencies
(mean, mode, median) and shape of the distribution (skewness and kurtosis) are compared
among classes. Most statistical texts and statistical software packages are available that describe
commonly used techniques.
The selection of statistical methods will vary depending on the assumed underlying statistical
distribution of the data, whether discrete or continuous relationships are analyzed, and whether
single or multivariate comparisons are analyzed. Various statistical methods have been described
for classification in developing biological criteria (Barbour et al. 1999; Hughes 1995). One rather
simple visual is to construct box-and-whisker plots of the sediment indicator of interest and to
compare overlapping confidence intervals. Another is to construct a series of cumulative
distribution functions (CDFs) and compare differences using the Kolmorogorv-Smirnov Test.
Fluvial Geomorphology
Fluvial geomorphology involves the study of the primary physical processes in streams and
rivers that erode, transport and deposit sediment, thereby influencing channel form, stability, and
changes over time. Geomorphology is relevant to criteria development as a source of measurable
parameters that can indicate departure from a sediment regime needed to support the designated
uses of a given waterbody. Further, classification of different waterbody types based on
geomorphic principles can be used to stratify waterbodies into more homogeneous clusters for
which more specific and appropriate sediment criteria can be developed.
Numerous authors (Rosgen 1994, 1996; Montgomery and Buffington 1993; Meyers and
Swanson 1992; Simon 1992) have observed the relationship between channel type classifications
and differences in stability among channel types. This relationship has ramifications for selecting
reference streams and for determining appropriate strategies for sediment management. Channel
evolution theory, which generally contrasts the structural properties of stable and unstable (or
transitional) channels and identifies common sets of steps that transitional channels pass through
in evolving toward a more stable state, further suggests that it may be possible to predict the type
of stable channel that will evolve from a given type of transitional, unstable channel. This could
be valuable when setting waterbody-specific sediment criteria.
Several decades ago, Pfankuch (1975) developed a system to rate channel stability. This rating
system has been widely used by hydrologists to quantify stream erosion potential and by fish
biologists to measure potential stresses to littoral habitat. Channel instability measures that are
not sensitive to natural expectations for the channel type and evolution may give a false sense of
impairment. Instability of a stream channel might be acceptable and, in some cases, might be
considered a reference condition because for short time intervals, all self-adjusting (alluvial)
channels, whether natural or altered, can be viewed as being unstable because the fluxes of water
and sediment are always changing. Rosgen (1996) has proposed a channel stability rating scale
that combines Pfankuch stability ratings and stream geomorphology.
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Framework for Developing SABS Water Quality Criteria
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Streamflow changes, sediment budget changes, and many other causes lead to channel change
that result in stability shifts. These shifts and adjustments lead to stream channel morphological
changes culminating in a stream type change. Stream type succession sequences were first
described as stages of channel evolution by Schumm et al. (1984) and Simon and Hupp (1986).
The nine successional sequences (Figure 9) show progressions through different stream classes
from the Rosgen system and indicate a larger range of possible morphological shifts and their
tendency toward a stable end-point (Rosgen 1999, 2001). The stream successional theory
suggests that streams depicted in the first and last frames of Figure 9 are morphologically stable
and would be appropriate reference sites. The intermediate stages are inappropriate reference
conditions because sediment is either being eroded or deposited at unnatural rates.
The channel type classes in the Rosgen
classification system (Rosgen 1994)
were developed and defined by
recognizing consistent patterns in
channel measurements from numerous
reference reaches. Parameters
commonly measured to document
channel dimension, pattern and profile
include bankfull width/depth ratio,
channel slope, sinuosity, entrenchment
ratio, and bedload particle size
distribution. For a channel class that is
typically stable, the physical traits of a
reference reach would likely
complement the biological traits
documented in the same channel type's
bioassessment reference condition.
Likewise, typically unstable classes'
reference reach data may co-occur with
and help explain sub-par
bioassessments. The added value of
structural reference reach data is their
closer relationship to sediment supply
and transport processes that play a part
in determining stream disturbance by
sediment.
i&iC_
5. E --------------- »• Gc --------------------- » F ---------------------------- » C
6. B
> B
*tf
Eh
GU
Figure 9: Various stream type succession
scenarios (after Rosgen 2001).
III.D.3. Associating Suspended and Bedded Sediments with Response
Indicators Applicable in Step 6 of the Framework
There are two general categories of methods for establishing quantitative associations between a
relevant measure of SABS and a response measurement that are relevant to the designated use
(see Section III.B step 4). The first method has the potential to reduce uncertainty regarding the
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Framework for Developing SABS Water Quality Criteria U.S. EPA
cause of changes in the biological response by controlling experimental conditions. This is
referred to as the Controlled Experiment method and may be performed in the laboratory or in
field mesocosms. The second method embodies all the complexity of waterbodies as they occur
in the region of interest and is based on field sampling but cannot control other variables in the
same way as in controlled experiments. This is referred to as the Field Observational method.
Using evidence from both controlled experiments and field observational analysis provides a
powerful duo of experimental rigor and a characterization of actual SABS and biological
conditions in a waterbody class. Furthermore, when both controlled experimental findings and
associations derived from in-stream measurements result in similar values, there is greater
confidence in setting the SABS criterion.
The Chesapeake Bay Criteria (Batiuk et al. 2000) and the Draft Technical Basis for Revising
Turbidity Criteria (Rosetta 2005) are excellent examples of criteria development programs that
benefit from the combination of mechanistic knowledge, controlled experiments, and field
observations for setting criteria for different designated uses. The Chesapeake Bay project is
described as an example of integration of many types of evidence and the complexity of
biological endpoints that can be affected. The Draft Technical Basis for Revising Turbidity
Criteria is concerned with water clarity and uses NTU as the measurement endpoint and
considers NTU as a surrogate that is somewhat protective of sedimentation and loss of habitat.
The U.S. EPA Science Advisory Board identified the conditional probability approach as
particularly useful for evaluating field observation data, which assigns probabilities of
impairments based on SABS measurements. Our example uses EMAP data from the mid-
Atlantic Region.
Controlled Experiments
Since the early 1980's, under Section 304(a)
of the CWA, U.S. EPA has been developing
WQC for toxic chemicals to protect aquatic
life. The majority of U.S. EPA's aquatic life
criteria have been derived from two
methods: (l)the 1980 Guidelines for
Deriving Water Quality Criteria for the
Protection of Aquatic Life and Its Uses
(U.S. EPA 1980, Appendix B), and (2) the
1985 Guidelines for Deriving Numerical
National Aquatic Life Criteria for Protection of Aquatic Organisms and Their Uses (Stephan et
al. 1985). The U.S. EPA is preparing a third revision that will incorporate the scientific and
technological advancements of the last 20 years. Current chemical criteria incorporate
magnitude, duration, and frequency endpoints. These are developed according to strict guidelines
using a species sensitivity distribution method (Stephan et al. 1985). SABS criteria based on
exposure-response data can be developed, in theory, much like chemical criteria. However,
achieving this goal - development of SABS criteria using the exposure-response - will be a
challenge because suitable methods, relevant data requirements, and accepted "endpoints" for
SABS currently do not exist.
The controlled experiment is one in
which aquatic organisms are tested
under controlled conditions for
behavioral or physical responses to
stressors. The stressors are varied
during the experiments so that
responses can be quantified with
respect to the level of exposure.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
Thresholds for SABS can be developed using the exposure-response if exposure-response
relationship(s) can be developed for selected groups of organisms. This method involves testing
aquatic organisms for adverse effects using suspended sediment (e.g. water cloudiness) or
bedded sediment (e.g., spatial extent) to quantify the character and severity of response as a
function of level of exposure. Experiments can be conducted either in the laboratory or field and
the results can be used in conjunction with other SABS measurements to determine impairment
in a waterbody. Results can also be used to develop exposure-response models which may be
useful at similar sites.
Exposure-response models currently exist for some species in some habitats, and criteria have
been developed for their protection (e.g., British Columbia Guidelines in Caux et al. (1997a),
Chesapeake Bay Water Clarity Guidelines in U.S. EPA 2003c). The Chesapeake Bay Water
Clarity Guidelines, for example, use a model that predicts the effect of reduced water clarity, due
in part to suspended sediments, on submerged aquatic vegetation (U.S. EPA 2003c).
Similar constructs are available in some commercially available modeling software packages as
well as in the U.S. EPA-supported ecosystem model AQUATOX (freely available at
http://www.epa.gov/ost/models/aquatox/). Currently, AQUATOX is able to simulate the impacts
of suspended sediment on light penetration in the water column and associated impacts on
primary productivity and ecosystem structure and function. It also can simulate the effects of the
organic portion of the sediments on the nutrient dynamics of the system. Future versions of the
model may include the ability to simulate other effects, including physical smothering of
spawned fish eggs by deposited sediment.
Guidelines for water quality criteria presented in Stephan et al. (1985) promote an approach
based on data from at least eight families from a diverse group of taxa. The diversity of tested
species is intended to assure protection of various components of an aquatic ecosystem. A
Criterion Maximum Concentration (CMC) is determined using average effects levels. Chronic
toxicity test data (longer term survival, growth, or reproduction) should be available for at least
three taxa to derive a Criterion Continuous Concentration (CCC). The chronic criterion can be
set by determining an appropriate acute-chronic ratio (the ratio of acutely toxic concentrations to
the chronically toxic concentrations) and applying that ratio to the criteria. When necessary, the
criteria - acute or chronic or both - can be adjusted to protect locally important or sensitive
species that were not considered during development of the criterion, or it can be adjusted based
on local water chemistry.
Sediment criteria may be based on experimental studies for a few sensitive indicator species
(e.g., salmonids, certain corals, certain mayfly, stonefly and caddisfly taxa, or bluegills). Each
indicator species could represent certain types of beneficial uses, aquatic systems, or regions of
the country. This is similar to a risk assessment approach.
The main strength of the controlled experiment method is that it employs techniques that are
used in standardized toxicity test methodologies and that are generally accepted by the scientific,
regulatory and stakeholder communities. The method is explicitly causative; controlled
laboratory or field mesocosm analyses address a single SABS indicator in relation to one or a
few response indicator(s). SABS criteria can be customized to the types of aquatic life present at
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Framework for Developing SABS Water Quality Criteria U.S. EPA
each site and may be adjustable to account for field conditions that are not simulated in the
laboratory. Moreover, it may be possible, using this method, to specify the amount of reduction
in SABS needed to maintain desired aquatic resources.
U.S. EPA has concluded that sound exposure-response, SABS data are lacking for most species,
and standardized consensus-based test methods for determining SABS effects are generally
unavailable. Therefore, it is unlikely that a list of acute and chronic values for SABS can be
developed in the short-term and such an effort would require substantial resources. A second
difficulty is that SABS can consist of many substances depending on the site. Therefore, much
like other "conglomerate" substances such as oil and grease or dissolved solids, it will be
difficult to identify appropriate criteria for SABS without first determining the specific type of
SABS (organic vs. inorganic; silt vs. clay, fine vs. coarse, etc.).
For bedded sediments, the substrate surrounding the fine sediments is an additional variable. The
lack of standard endpoints for determining the effects of either suspended or bedded sediments
on specific organisms and the need for the development of minimum data requirements are
additional drawbacks. If thresholds could be developed through controlled experimentation, there
would still be uncertainties due to interactions of the many other factors that influence SABS
effects and that are not generally tested during controlled experiments.
The controlled experiment method has two characteristics that result in uncertainty. Firstly, it is
difficult to account for natural or background conditions and organisms' acclimation to dynamic
environmental changes in SABS. Secondly, SABS do not necessarily act on organisms in the
environment in the same way as toxicants. The change point between a detrimental level of
SABS and a beneficial one is a function of amount, duration, and distribution rather than of
concentration and duration. In principle, these limitations could be addressed through certain
U.S. EPA-approved mechanisms to modify national criteria on a site-specific basis. The
Recalculation Procedure (U.S. EPA 1994), for example, could be used in lieu of national SABS
criteria based on the types of species that could occur in the region or waterbody classification,
and their natural sensitivity to SABS. However, use of such a procedure assumes the availability
of fairly large acute toxicity database (>20 genera, at a minimum), which may not be feasible in
the short-term.
Field Observations
As bioassessment and biocriteria have become common tools for assessing the status of aquatic
life, rich data sets have been generated that include measures of physical, chemical, biological,
and landscape characteristics. These data sets provide an opportunity to examine relationships
between SABS and other variables. This Section focuses only on the relationship between SABS
and biological indicators, but the analytical methods and study design concepts are also relevant
to other physical and chemical attributes of aquatic systems and is essentially the basis of the
Waterbody Use Functionality (Section III.D.3). The strength of using field observational
methods is that they enable analysis of SABS and their potential effect on biota as they occur in a
defined region or class of waterbody type. This strength is also its weakness because variability
among field samples might reflect natural variability, or SABS, or some other stressor linked to
human activity. Therefore, analysis must take into account that a lower than expected
measurement of a biological indicator may be due to other causes besides the one of interest, in
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this case SABS. Any analysis must consider these other sources of variation when developing
stressor/response relationships using field sampling.
Percentile Analysis (Including Reference Condition Methods). One method is to attempt to
remove sites with known stressors from the data set that is analyzed. This is the basis for some
types of reference condition analyses more specifically termed here as Percentile Analysis.
Percentile Analysis method for developing sediment criteria follows the example of the regional
reference condition method for developing biological criteria (Barbour et al. 1999; Hughes
1995). It is based on the a priori selection of a population of sites with a similar SABS regime
(Section III.D.2.). From the population of sites with similar sediment regimes, a subset of sites
are selected that meet designated uses (e.g., supports cold water fishery), represent best attained
conditions for a specific assessment endpoint (e.g., presence of threatened species) or represent
nearly natural SABS conditions (as described in Section III.D.2). Some factors should be kept in
mind when using a Percentile Analysis method.
(1) Using a population of sites that meets designated uses is defensible, but may put valued
resources at risk if the sites do not protect downstream uses, if the designated uses are
somewhat lax, or if waterbody sub-types were too broadly defined.
(2) Best attained condition as an approach to select sites can demonstrate that the standards
will be achievable but may underestimate impacts in classes of waterbodies that are
generally highly altered. Even the best available conditions might not really meet the
expectations of the CWA. However, using the best sites can point management in the
right direction and clearly help to define highly degraded sites.
(3) Using sites with nearly natural SABS regimes is sensitive to errors in selecting criteria for
defining natural sites. This does not directly demonstrate how SABS affects the response
indicator or designated use.
In all three cases, distributions of SABS for the population of sites is described, usually as a
cumulative distribution function or box plot, a value from within that distribution is selected as
the SABS criterion. More than one designated use can be defined for a class of streams. For
instance, a different criterion might be selected for exceptional waterbodies and another selected
criterion that enables streams to meet state water quality standards for aquatic life. Typically, the
criterion is set at the 75th percentile of sites attaining their designated use or characterized as best
attainable conditions. The selection of the percentile is also influenced by the desired level of
protection, which is dependent on the designated use. Therefore, criteria for designated uses of
"exceptional biodiversity" or "irrigation supply" may be based on different percentiles.
Exposure and Effects Analysis. Another method assumes that SABS is a limiting stressor on
biological communities and that the upper limit of biological measurements is an estimate of the
best possible performance expected for a system given any point along a range of exposures.
This assumption may be violated if the biological measurement is influenced in a positive
direction by another stressor, for instance, moderate organic enrichment increasing fish biomass.
There are a number of statistical methods that can be used to analyze these data sets. For
continuous variables they include, but are not limited to, conditional probability analysis,
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regression, quantile regression, maximum response curves, and several different multivariate
statistical analyses. With quantile regression, the likely biological conditions in the absence of
any other stressors are described by estimating changes in the response variable relative to a
measurement of SABS near the upper range of the response distribution (i.e., 90th or 95th
percentile; Figure 10). Regular regression models the median (i.e., 50th percentile) relationship.
These same statistical methods can also be applied to data sets in which SABS is reduced as a
part of mitigation. Specifically, if the response indicator is measured before and several times
after intervention at a single site, the level of SABS that is present when the designated use is
met represents a threshold, which may be considered when setting criteria. The combination of
field observations and controlled experiments is illustrated in the Chesapeake Bay Case.
i/)
i/)
20 -
15 -
TO
X
5 10
"c
2
5H
0 -
o o
o
.p o oo o o
^^
Ecoregions 46, 47, 48, and 51
Ecoregions 50 and 52
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Framework for Developing SABS Water Quality Criteria
U.S. EPA
I
Ligjil TtLULsiiiibsii.ii)
Light Atlenwukni
Surface
Synthesis of Controlled Experiments and Field Observations in the Chesapeake Bay
The Chesapeake Bay-specific water clarity criteria constitute one of the best examples of the use
of exposure-response methods for development of SABS criteria. The criteria are based on a
conceptual model of the effects of reduced light to the leaves of submerged aquatic vegetation
(Figure 11). This model was developed using knowledge from both controlled experiments and
field observations.
The loss of underwater bay grasses from the shallow waters of the Chesapeake Bay is a
widespread, well-documented problem caused by decreased light intensity. Also certain
wavelengths of light may not be transmitted through the water. The loss of underwater bay grass
beds is of particular concern because these plants create rich animal habitats that support the
growth of diverse fish and invertebrate populations and provide food for waterfowl. The primary
causes of losses are nutrient over-enrichment and increased suspended sediments in the water
and the associated reduction
of light. The key to
restoring the bay grass beds
is to provide the necessary
levels of light penetration in
shallow waters to support
their survival, growth, and
reproduction. The
Chesapeake Bay Water
Clarity Guidelines employ a
model to predict the effect
of reduced water clarity,
due in part to suspended
sediments, on underwater
bay grasses (U.S. EPA
2003c). This model is based
on associations derived
from both controlled
experiments and field
observations that link
changes in valued attributes
of the Bay with different
exposures to nutrient
enrichment and suspended
sediment.
f1.. illk I'M
Chlorophyll a
Tuial
Suspended
S-^N
•Wolcr
* Color
1
tpiphyte*
I.tglht.nl.] .euf * Sediments
•1'M.ri:. f- l.igtit Anenunticm
Figure 11. Availability of light for underwater grasses is influenced
by water column and at-the-leaf surface light attenuation. DIN =
dissolved inorganic nitrogen, DIP = dissolved inorganic phosphorus.
The Chesapeake Bay-specific water clarity criteria were derived in four stages: (1) water
column-based light requirements for bay grass survival and growth were determined, (2) factors
contributing to water-column light attenuation were quantified, (3) contributions from epiphytes
to light attenuation at the leaf surface were factored into analyses for estimating total light
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Synthesis of Controlled Experiments and Field Observations in the Chesapeake Bay
(continued)
attenuation and (4) a set of minimal requirements for light penetration through the water and at
the leaf surface were determined to give the water clarity criteria values.
The principal relationships between water quality conditions and light regimes for the growth of
underwater bay grasses are illustrated in a conceptual diagram (Figure 11). Incident light is
attenuated through the water column above the bay grasses by particulate matter (chlorophyll-a
and total suspended solids), by dissolved organic matter and by water itself. The water-column
light attenuation coefficient (Kd) is dominated by contributions from chlorophyll-a and total
suspended solids. Light that actually reaches the underwater bay grass leaves also is attenuated
by the epiphytic material (i.e., algae, bacteria, detritus and sediment) that accumulates on the
leaves. This epiphytic light attenuation coefficient (Ke) increases exponentially with epiphyte
biomass. Dissolved inorganic nitrogen (DIN) and phosphorous (DIP) in the water column
stimulate the growth of epiphytic (and water-column) algae. Suspended solids also can settle
onto bay grass leaves. Because epiphytic algae also require light to grow, water depth and water-
column light attenuation constrain epiphyte accumulation on bay grass leaves, and light
attenuation by epiphytic material depends on the mass of both algae and total suspended solids
settling on the leaves.
An algorithm was developed to estimate light attenuation at the leaf due to the biomass of
epiphytic algae and other materials attached to bay grass leaves (Kemp et al. 2004; Batiuk et al.
2000). The algorithm was verified by applying it to Chesapeake Bay water quality monitoring
data. It uses monitoring data for the water-column light attenuation coefficient (or Secchi depth),
total suspended solids, DIN and DIP concentrations to calculate the potential contribution of
epiphytic materials to total light attenuation for bay grasses at a particular depth. Using a set of
commonly monitored water quality parameters, attainment of the percent light-through-water
(PLW) water clarity criteria and percent light-at-the-leaf (PLL) diagnostic parameter can be
readily determined for any established restoration depth.
To determine the Chesapeake Bay water clarity criteria necessary to ensure that sufficient light
reaches bay grass leaves at a defined restoration depth, three lines of evidence were compared:
• Application of bay grasses habitat requirement parameter values to the new algorithm
for calculating percent light-at-the-leaf.
Evaluation of results of light requirement studies in areas with few or no epiphytes.
• Comparison of median field measurements of the amount of light reaching plants'
leaves (estimated through the percent light-at-the-leaf algorithm) along gradients of
underwater bay grasses growth observed in the Chesapeake Bay and its tidal tributaries.
Based on a thorough review of controlled shading experiments and model findings published in
the scientific literature, a PLW value of greater than 20 percent is needed for the minimum light
requirement of Chesapeake Bay mesohaline and polyhaline species (Batiuk et al. 2000).
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Synthesis of Controlled Experiments and Field Observations in the Chesapeake Bay
(continued)
Consistent with the literature-derived value, the PLW requirement of 22 percent was determined
for mesohaline and polyhaline regions of the Chesapeake Bay and its tidal tributaries using the
algorithm for calculating percent light-at-the-leaf This PLW requirement was confirmed by
almost two decades of field observations in the Potomac and York Rivers (Batiuk et al. 1992,
2000; Moore 1996; Moore et al. 2001).
Based on published model findings reviewed in Batiuk et al. (2000) and confirmed by a review
of recent tidal Potomac and Patuxent River research and monitoring studies, a PLW requirement
of 13 percent was determined to apply to Chesapeake Bay tidal-fresh and oligohaline species.
This light requirement was calculated using the algorithm for calculating percent light-at-the-leaf
and the appropriate SAV habitat requirements for Kd. The PLW requirement is consistent with
the 13.5 percent value published by Dennison et al. (1993). The PLW requirements in both
salinity regimes were validated through an ecoepidemiological analysis of 14 years (1985-1998)
of Chesapeake Bay water quality monitoring data.
The Chesapeake Bay water clarity criteria are summarized in Table 5 as PLW and Secchi depth
equivalents over a range of application depths. They reflect a set of minimum light requirements
to protect underwater bay grass species. The Secchi depth criteria vary across salinity regimes
and through the seasons because of differing light requirements, growth potential, and
reproductive strategies.
Table 5. Summary of Chesapeake Bay water clarity criteria for application to shallow-water bay
grass designated use habitats (U.S. EPA 2003c).*
Salinity
Regime
Tidal-fresh
Oligohaline
Mesohaline
Polyhaline
Criteria as
Percent
Light
Through
Water
13%
13%
22%
22%
Water Clarity Criteria as Secchi Depth
Water Clarity Criteria Application Depths
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.0
Secchi Depth (meters)
for above Criteria Application Depth
0.2
0.2
0.2
0.2
0.4
0.4
0.5
0.5
0.5
0.5
0.7
0.7
0.7
0.7
1.0
1.0
0.9
0.9
1.2
1.2
1.1
1.1
1.4
1.4
1.2
1.2
1.7
1.7
1.4
1.4
1.9
1.9
Temporal
Application
Apr 1 - Oct 31
Apr 1 - Oct 31
Apr 1 - Oct 31
Marl - May 31
Sep 1 - NovSO
*Based on application of the equation, PLW = 100exp(-Kd*Z). The appropriate PLW criterion value and
the selected application depth (Z) are inserted and the equation is solved for the light attenuation
coefficient (Kd). The generated Kd value is then converted to Secchi depth (in meters) using the
conversion factor Kd = 1.45/Secchi depth.
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Conditional Probability Analysis. This detailed section is devoted to the Conditional
Probability Analysis (CPA) method because the Science Advisory Board found this to be one of
the more useful methods for showing the relationships between the SABS indicator and the
desired condition of the waterbodies, conveying the impacts of selecting different SABS criteria
and ability to inherently incorporate uncertainty into the analyses. The CPA method is illustrated
in the mid-Atlantic stream case. This case also introduces some methods for evaluating change-
points (thresholds or transition points) that may be helpful for identifying reasonable criteria
values. Refer to Paul and McDonald (2005) for details of the CPA method and the application to
mid-Atlantic streams.
The application of the CPA method for criteria development describes the association between
the SABS indicator and the designated use indicator as a probability of observing impairment (or
not observing impairment) when a particular level of SABS indicator is exceeded. The CPA
method communicates the outcome in terms that are relatively easy to understand. A
hypothetical outcome might include sites with more than 60% fines, where there is a 90%
probability that the biota will be impaired. The analysis provides the user with the ability to
evaluate the probability of impact across the full range of observed SABS levels.
The following are recommended for application
for criteria development to take advantage of the
full capability of CPA: (1) monitoring data should
be acquired using a probability-based sampling
design, (2) some metric must quantify SABS
levels, (3) a response metric must be sufficiently
sensitive to respond to the extant levels of the
SABS metric, (4) independent studies should
identify the characteristics of an impacted
response metric; and (5) the SABS metric must be
capable of exerting a strong effect on the response
metric.
Probability-based design data can provide
estimates of the probability of occurrence for a
sampled variable in the statistical population. The
statistical population is the desired resource for which various statistical parameters will be
estimated and from which samples will be drawn for data acquisition. For example, consider the
statistical population of all stream segments in a state. If 75% of the stream segments sampled
exhibit impacted benthic communities, then the probability of observing benthic impairment in
any of the stream segments in the state was 0.75 during the sampling period. When data are
collected from a targeted set of sites and are not probability-based, then the bias introduced by
site selection factors must be accounted for if the results are to have any reasonable meaning
beyond the locations actually sampled.
The probability of observing a certain event, y, is denoted as P (y). A conditional probability
is the probability of an event y occurring given that some other event x also has occurred. It is
denoted P (y | x). The vertical line means "conditioned on," not "divided by." Thus, a conditional
Conditional probability
analysis quantifies the
likelihood that biotic impacts
will occur when a given level
of SABS exposure is
exceeded. Probabilities are
based on the likelihood of
observing an undesirable
response indicator. Judgments
as to acceptable SABS
indicator levels can be made
based on desired probability of
impact.
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Framework for Developing SABS Water Quality Criteria U.S. EPA
probability describes the likelihood of observing an event of interest in a subset of samples
drawn from the original statistical population. These subsets are defined by conditions when x
has occurred, in addition to those used to define the entire statistical population. Conditional
probability can be calculated as the ratio of the joint probability that y and x occur
simultaneously in a given sample (P (y, x)) from the original statistical population, to the
probability of x in the original population
P(y|x) = P(y,x)/P(x) (1)
This is considered a definition of conditional probability (Hogg and Ledolter, 1992). An example
of a conditional probability statement would be the probability of benthic community impact if
total copper levels in the sediments exceed 10 ppm. The events y and x are considered
statistically independent if, and only if, their conditional probabilities (of one another) are equal
to their (unconditional) probabilities in the original statistical population. Conditional
probabilities differ from joint probabilities, which are often used in risk assessment (e.g.,
Verdonck et al. 2003). Joint probability, when the two variables are statistically independent, is
calculated simply as the product of P (y) and P (x). So, P (y, x) = P (y) * P (x). If two variables
are statistically independent, then the conditional probability is equal to the unconditional
probability (see Paul and McDonald (2005) for additional information).
Application of Conditional Probability Analysis for Criteria Development. Our application
of the CPA method for criteria development starts with a two-step procedure to calculate the
conditional probabilities (Paul and McDonald 2005). We let y represent the dichotomous
response variable (1 for impaired conditions, 0 for good conditions) and assume it to be a
random variable. We let x be the SABS indicator, which is also a random variable. We let xc be
the conditioning value for the SABS indicator. In the first step, we identify subsets of the
sampled resource (e.g., stream segments) for which x > xc (i.e., we order the samples based on
the value of SABS indicator). In the second step, we determine which of the SABS indicator
values also have impaired response indicator values. This allows us to determine, for example,
the fraction of the stream miles in which SABS indicator values are greater than or equal to a
specific value (xc) and also had impaired biological response. This two-step procedure is applied
over the range of observed SABS indicator values. This produces an empirical curve for the
conditional probability, the probability of expecting an impaired biological response when
observed SABS indicator values are greater than or equal to xc.
This empirical curve provides the probability of impairment of the ecological system (e.g.,
benthic community structure degradation) for an exposure to high levels of SABS indicator.
Confidence intervals (CIs) for this empirical curve are estimated for each value of xc by
assuming that the individual values that go into determining P(y =1 x < xc) can be treated as a
simple random sample when at least two individual values are available.
Identifying Thresholds of Impact. Threshold levels for pollutants or pollution, such as SABS,
that elicit different levels of biological impact in waterbody elements of a region need to be
identified for eventual use in developing criteria. A threshold of impact is identified as a
changepoint separating the empirical conditional probability curve into two parts: the part of the
curve above the changepoint and the part below it. For those samples that are above the
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Framework for Developing SABS Water Quality Criteria U.S. EPA
changepoint, the probability of impact is different than what one would expect for the entire
geographic area. A confounding factor in the identification of a changepoint is that these two
groups created by the changepoint are not independent (i.e., the numbers used to create the points
above the changepoint are a subset of the numbers used to create the points below the
changepoint). Thus, a traditional t-test cannot be used in the determination of the changepoint
since the data are not independent (Venables and Ripley 1997). Using a weight-of-evidence
approach with different techniques will identify the change point. Three examples of these
techniques are (1) non-overlapping confidence intervals, (2) change in curvature of fitted curve,
and (3) nonparametric deviance reduction. Other possible techniques could be used to identify a
changepoint. In this demonstration, specific values for factors and confidence intervals were
selected only as examples. Values used in an actual application of this approach would depend
on the particular management requirements and objectives.
The use of non-overlapping confidence intervals (CI) to determine a changepoint involves
determining when the lower CI of the empirical curve no longer overlaps the upper CI of the
unconditional value (Cherry 1996, 1998; Austin and Hux 2002; Rahlfs 1997). This procedure is a
conservative estimate for significant difference since the CIs could overlap when the values are
significantly different (Austin and Hux 2002). The bootstrap percentile confidence intervals,
based on a bootstrap distribution of 1000 samples, were used for this evaluation. The a-level for
the non-overlapping confidence interval must be adjusted to account for the one-sided nature of
this test, whereas the a-level for developing the confidence intervals for the curves was based on
a two-sided test (i.e., a factor of 2 in the a-level).
The second technique used for selecting a threshold of impact through changepoint identification
is to fit an equation to the empirical curve for conditional probability. The following constraints
are used: the conditional probability approaches the unconditional value, P (y = 1) as x goes to
the minimum x-value; the conditional probability approaches 1 as x goes to the maximum value;
and there is a curvature change at the inflection point of the curve. The following functional form
satisfies these constraints:
+ (D0 - 1) /l + exp(B0 (xc -x0 )), for xc >x0
(2)
+ (D0-l)/(l + exp(B1(xc-x0))j, for xc x0, and
BI is curvature for values of xc < x0.
The parameters XQ, BO, and BI are determined from a nonlinear least squares regression
(Venables and Ripley 1997). Uncertainty in the parameters is estimated from the standard errors
generated by the regression software and, where possible, by computing asymmetric confidence
intervals (Venables and Ripley 1997). The residuals from the regression are checked for
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normality. While it may be generally possible to fit equation (4) to the empirical curve, the
curvature values (B0 and BI) may not be significantly different, and a threshold would not be
identified with this technique.
The third technique uses nonparametric deviance reduction to determine the changepoint. This
determines the dividing point for splitting the data into two groups resulting in the largest
reduction in the deviance in the data (Qian et al. 2003). The deviance is defined as
(3)
z=l
where:
D is the deviance,
N is the sample size,
P; is the conditional probability P (y = 1 | x > x;), and
P* is the mean of P; based on a sample size of N.
When the data are divided into two groups, the sum of the deviance for the two subgroups is
always less than or equal to the deviance for the entire data set. When the split in the data
minimizes the deviance, the threshold is identified. This has been used to detect ecological
changes along an environmental gradient (Qian et al. 2003). Qian et al. (2003) compared results
of deviance reduction with a Bayesian hierarchical modeling and found that the nonparametric
provides similar results with the Bayesian analysis.
The deviance reduction point generally can be determined, but it may or may not be of biological
significance. Uncertainty in the deviance reduction changepoint (90% and 95% confidence
intervals) is estimated from the empirical percentiles for the bootstrap distribution from
resampling 1000 times (Manly 1997). An approximate %2 test was used to determine the
significance of the changepoint. The test assumes that the deviance reduction divided by the
scale parameter is approximately y2 distributed with 1 degree of freedom (Venables and Ripley
1997). A large deviance reduction will result in a small p-value, and the consequent rejection of
the null hypothesis (Ho: no changepoint).
Biological Importance of Identified Thresholds. For use in criteria development, some level of
biological importance needs to be associated with the threshold of impact value that is identified.
The changepoint value determined by each technique must separate the samples so that the
probability of impact for samples above the threshold would be different than what one would
expect for the entire geographic area. As an example, a summary of literature values on the
response offish and benthic invertebrates at low reported levels of percent fines in the substrate
(Newcombe and Jensen 1996; Berry et al. 2003; Bash et al. 2001) was used to identify biological
importance for the mid-Atlantic streams case.
Statistical Analysis of Data. Several statistical analyses are useful in addition to the conditional
probability determination. The cumulative distribution function (CDF), the conditional
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cumulative distribution function (CCDF), and their reverses were used to complement the
conditional probability calculation. The CDF gives probability that x is less than or equal to xc:
(4)
The reverse CDF is the probability that x is greater than xc, which is the complement of equation
(5) or,
(5)
*.•<*„
The conditional cumulative distribution function (CCDF) is the distribution for a subset of the
total data, conditioned on a second variable [F(y | x)]. The reverse CCDF uses l-F(y | x). The
reverse functions are consistent with the CPA results, which are expressed as a threshold (i.e.,
exceeding some value xc).
Application of Conditional Probability Analysis to Mid-Atlantic Wadeable Streams
CPA was used to establish realistic thresholds for impacts to stream biotic condition from non-
point source pollution in the mid-Atlantic region of the U.S. (Paul and McDonald 2005). The
mid-Atlantic was selected because of the extensive amount of research and monitoring of
streams that has been done in this region (see example in Boward et al. 1999; U.S. EPA 2000b),
which provided the information base needed to satisfy conditions for application of CPA.
These data were collected from mid-Atlantic streams in 1993 and 1994 and include 102 stream
segments in 1st to 3rd (Strahler) order wadeable streams as part of EMAP (Herlihy et al. 2000)
(Figure 12). These segments were selected
for sampling using a spatially balanced
probability design. Inclusion probabilities
for each sampled stream segment were
determined using the sample sizes for each
Strahler order and the total length of
streams within each order in the region.
Sampling locations within stream
segments were chosen randomly.
Quantitative data for stream
macroinvertebrates, habitat, and water
quality were collected at each site.
Sampling took place during a yearly, two-
month sampling window from April Fjgure u Mid-Atlantic region of the U.S. with
through mid-June. EMAP wadeable stream sampling sites.
• •
)•' V '•••
/. « • •
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Framework for Developing SABS Water Quality Criteria
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Application of Conditional Probability Analysis to Mid-Atlantic Wadeable Streams (continued)
Stream benthic macroinvertebrates are a robust measure of stream condition, integrating
temporal pollutant exposure. They are responsive to in-stream changes to sediment levels.
Benthic stream community taxa in the orders Ephemeroptera (mayflies), Plecoptera (stoneflies),
and Trichoptera (caddisflies) (collectively known as EPT) are considered reasonably sensitive
indicator organisms since they exhibit a decrease in taxa richness with increased degradation of
stream conditions. EPT taxa were used to identify SABS-related impacts in stream segments in
the mid-Atlantic. When EPT taxa were < 9 in these stream segments, the streams were
considered impaired (Davis and Scott 2000).
For the purpose of this study, percent fines in the substrate were used as a surrogate indicator for
sedimentation in streams. Percent fines (silt/clay fraction, < 0.06 mm) represent a direct measure
of the smallest class of sediments. Percent fines are strongly correlated with sediment
embeddedness, a source of the most-likely-to-be resuspended sediment, and an indirect measure
of suspended sediment levels in the water column. Streams containing a larger fraction of fine
sediment would be expected to have a benthic community at greater risk for impact.
The reverse cumulative distribution function (CDF) and reverse conditional CDFs for percent
fines in the substrate are expressed as proportion of stream miles (Figure 13). The sampled
stream segment values are weighted by inclusion probabilities to convert to stream miles. The
distribution for impacted benthic communities is displaced to the right of the distribution for
benthic communities in good condition as should be expected. The distribution for reference
conditions (the best conditions) is shifted to the left (towards lower percent fines) of that for
unimpacted streams.
unimpacted benthic conditions
reference cond
Percent Fines in Substrate
Figure 13. Reverse cumulative distribution function (CDF) for percent fines in the substrate
(silt/clay fraction, < 0.06 mm) for stream miles across entire area (all), and reverse conditional
CDFs of stream miles for impacted benthic conditions (EPT taxa richness < 9), unimpacted
benthic conditions (EPT taxa richness > 9) and reference conditions. Vertical line is where the
threshold of 15 percent fines intersects the curves.
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Application of Conditional Probability Analysis to Mid-Atlantic Wadeable Streams (continued)
The outcome of the CPA application suggests that when percent fines in the substrate is greater
than 49%, there is a 100% probability that the benthic communities are impacted (Figure 14). All
sites with percent fines in the substrate in excess of 49% had EPT taxa richness less than 9. As
the percent fines approach zero, there is a background level of impact on EPT taxa richness from
all sources of stress in the region (mean = 42%, 95% confidence interval of 30-56%). Thus,
irrespective of the level of percent fines in the substrate, approximately 42% of the stream-miles
in the region will likely exhibit an impact on EPT taxa richness, Therefore, to detect a significant
signal due to percent fines in the substrate affecting the U.S. EPA taxa richness, the upper
confidence limit on our estimate of the background impairment (e.g., 56%, Figure 14) must not
overlap with the lower confidence limit on the probability of benthic impact. This occurs when
the percent fines in the substrate is 15%. It could be argued that this is the initial threshold of
impact that is distinguishable from background within this geographic area. The mean
probability of observing impacted EPT taxa richness associated with this threshold is 67%.
20
40
60
80
100
Percent Fines in Substrate
Figure 14. Probability of observing EPT taxa richness < 9 (benthic impact) in mid-Atlantic
streams (open circles) if specified value of percent fines in the substrate (silt/clay fraction, < 0.06
mm) is exceeded. Solid line is fit to data using equation (2).
The CPA method identified a threshold of 15% fines (from non-overlapping confidence
intervals) would translate into approximately 47% of the total stream miles in the geographic
area exceeding the threshold (from Figure 13). Similarly, only a small percentage of streams with
reference condition characteristics (6%) or good benthic conditions (21%) would exceed the 15%
fines threshold, but a much larger percentage of streams where impacts are occurring (74%)
would exceed it. These values provide an estimate of the number of "false positives" for this
value of a threshold for percent fines as the indicator of sedimentation. Because multiple
stressors often impact stream communities, we cannot estimate the "false negatives." A
community not stressed by the stressor of interest might be stressed in some other way.
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Waterbody Use Functionality
The waterbody use functionality method is proposed for developing SABS criteria for designated
uses other than aquatic life. This method examines the existing literature and focuses criteria on
non-aquatic life uses such as recreational (swimming, boating, etc.), industrial, navigational,
drinking water, and agricultural uses, among others. Although not emphasized in the CWA,
economic impacts from poor stewardship of sediment supply can also have costly repercussions.
Some impaired functional uses related to sediment management include flooding, bank erosion
with collapsing infrastructure, and loss of coastal wetlands and protection from storm surges
among others. As costs continue to rise, these functions can no longer be overlooked.
The waterbody use
functionality approach
focuses the process of
SABS criteria development
on the desired outcome:
attainment of all the
designated uses of the
waterbody. This approach
is proposed in cases where
uses other than aquatic life
uses must be attained.
Functional-based benchmarks for protecting uses other
than aquatic life apply primarily to waterbodies where
aquatic life uses do not exist (historically, not present or
removed through a Use Attainability Analysis (UAA), or
where multiple designated uses have been assigned to a
waterbody (such as a large river system) and SABS
levels fluctuate substantially throughout the extent of the
system. However, where multiple designated uses (such
as aquatic life and irrigation) overlap in a waterbody or
on a specific segment or portion of the waterbody,
SABS criteria established to protect the aquatic life use
most likely will be stringent enough to protect all other
uses except perhaps drinking water uses. In such cases,
additional functional criteria may not be necessary. This
is a presumption that needs further investigation.
Benchmarks protective of the functional use would be based on data and information from the
literature, field observations, and state experiences. For example, if shipping and navigational
uses were the primary use of a waterbody, criteria would be established to prevent or minimize
the depositional rates of sediments that would prevent accelerated filling of shipping channels
thereby preventing frequent dredging to maintain those channels.
For agricultural water usage, including irrigation and livestock watering, benchmarks could be
established based on data that illustrate the level of sediment that causes problems to pumps and
piping or increases the need and expense for filtering. Similarly, benchmarks could be set to
protect levels of clarity for swimming, sources of drinking water and other functional uses where
the literature indicates potential thresholds for protecting these non-aquatic life uses. Exposure-
response relationships for aquatic biota would not be a critical basis for these criteria.
Examples where functional benchmarks have already been suggested or applied include National
Academy of Sciences (NAS)/National Academy of Engineering (NAE) (1973), National
Technical Advisory Committee (NTAC) (1968), Australian and New Zealand Environment and
Conservation Council (ANZECC 2000; Parametrix 2003). Some narrative and numeric examples
include:
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• Waters used for bathing and swimming should have sufficient clarity to allow for the
detection of subsurface hazards or submerged objects and for locating swimmers in
danger of drowning.
• Clarity should be such that a Secchi disk is visible at minimum depth of four feet given
its conclusion that clarity in recreational waters is highly desirable from the standpoint of
visual appeal, recreational opportunity, enjoyment, and safety.
• The visual clarity guidelines are based on the objective that to protect visual clarity of
waters used for swimming, the horizontal sighting of a 200mm diameter black disc
should exceed 1.6 m.
• Turbidity in water should be readily removable by coagulation, sedimentation, and
filtration; it should not be present to an extent that will overload the water treatment plant
facilities, and should not cause unreasonable treatment costs. In addition, turbidity should
not frequently change or vary in characteristics to the extent that such changes cause
upsets in water treatment processes.
• No more than 15 NTUs over background will generally protect the visual aesthetic
quality of a clear water stream.
Advantages and Disadvantages of the Methods
The U.S. EPA Science Advisory Board recommended that the distinct advantages and
disadvantages of each method should be considered when deciding how to apply them in specific
criteria development situations. Table 6 summarizes this information.
III.E. Hypothetical Examples of the Synthesis of Methods Within the
Framework
The following hypothetical examples illustrate the process for developing SABS criteria in
representative waterbody types. The first scenario describes the sequence of SABS criteria
development steps for a statewide set of high gradient, 2nd to 3rd order headwater streams. This
hypothetical scenario includes (1) the decision process for the selection of measurements for
SABS and response variables that are appropriate to the waterbody type and designated uses; (2)
the possible rationales for selecting analytical methods for linking SABS to impacts; and (3) the
importance of using a logical and transparent decision analysis to select SABS criteria. Fewer
detailed example scenarios are also provided for several other waterbody types, including large
rivers, regulated rivers, wetlands, lakes, ponds and reservoirs, estuaries, estuarine wetlands, and
coastal waters. Different designated uses and types of criteria are also mentioned to give the
reader a sense of the range of situations in which SABS criteria development might occur. Actual
data analysis is not included in these hypothetical cases. Efforts are ongoing to prepare one or
more case studies based on actual data sets.
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Table 6. Advantages and disadvantages of methods used in SABS criteria development.
Advantages
Disadvantages
Measurement of SABS
Readily
Available
Measures
(e.g., SSC,
Percent fines,
Secchi
distance)
Published methods with known
performance
Often measured by state, tribal,
territorial, and federal monitoring
programs
Good body of published literature
linking direct measures to
biological effects and to land
cover/land use
Often not easily tracked to sources
Sediment
Transport
Curves
Can reveal channel stability's
effects on within-channel sediment
loads, and explain past, present,
and predicted erosional and
depositional processes that may
affect restoration
Applies only in flowing waters (though
similar systems may be developed for slow
and still waterbody types)
Requires extensive field sampling under
specific field conditions.
Not vetted for all waterbody types.
Relative Bed
Stability
Accounts for local environmental
conditions (standardized to the
reference condition)
Measures both excessive and
deficient sediments
Not as effective in sand bedded rivers and
streams where fine sediments are
transported frequently and where SABS
impairment is not closely related to
sediment transport competence
Current formulation only useful for
flowing waterbodies though analogous
methods may be developed to evaluate
stability of sediments in lakes and coastal
waters as influenced by wave action.
Classification
Empirical
Classification
Many states are familiar with this
method, having used it in
biological assessment programs
May be cost effective because the
framework is in place in many
states
Reference site selection can be subjective.
Large data sets are preferred and not
always available for all classes that should
be compared.
Fluvial
Geomorph-
ology
Good for stratification before
assessment or for diagnostics after
identifying impairment
Can reveal channel stability's
effects on within-channel sediment
loads and explain past, present,
and predicted erosional and
depositional processes that may
affect restoration
May be more indicative of sediment effects
some distance from the observed
geomorphology rather that at the location
Measurements are local rather than based
on landscape scale parameters, and
therefore, require field sampling.
Not verified for all waterbody types.
Inferring mechanisms from form has not
been demonstrated to be technically
supportable
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Table 6. (continued)
Advantages
Disadvantages
Associating SABS to Response Indicators
Controlled
Experiments
Cause and effect relationships
supported
Familiar derivation and application
Criteria can be tailored to biotic
types in the system
Thresholds can be identified for
individual species
Standard development is
independent of setting so that
states could adopt standards after
development in any region (more
cost effective to states)
Data are lacking for many species and
development of criteria would take time
and money (if only sensitive species were
addressed, investment could be reduced)
Sediment criteria may not be specific to
site conditions (because sediment character
and site context are variable)
SABS do not act in the environment as do
toxicants
Difficult to factor in background levels
Field
Observations:
Percentile of a
Distribution of
Exposures
and
Full Range of
Exposures and
Effects
Familiar derivation and application
Criteria can be tailored to biotic
types in the system
Thresholds can be identified for
individual species
Field conditions and background
levels are taken into account
Many states are familiar with this ,
having used it in biological
assessment programs
May be cost effective because the
framework is in place in many
states
Other stressors confound the association.
When least disturbed sites are compared,
there is an assumption that these will meet
designated uses and that may not be true
The reference condition may represent an
unattainable condition
Field
Observations:
Conditional
Probability of a
Selected Effect
Provides likelihood of impact for
exceeding pollutant or pollution
level
Incorporates statements of
uncertainty
Use of probability-based survey
data permits an unbiased
extrapolation of results to the
statistical population from which
the sample was drawn
Other stressors confound the association.
Traditionally, a single-factor (although it
could be modified to include multiple
factors)
Waterbody Use
Functionality
Applies in waterbodies where
aquatic life is not a primary
concern
Explicit stratification by
designated use
• Does not protect ecological integrity in
waterbodies that are not designated as
having an aquatic life use
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The detailed scenario and other examples illustrate how some of the proposed methods might be
used together to establish SABS criteria (Table 7). Each of these cases is based on activities and
steps within the process that is described in Section III.B of this Framework:
1. Review current designated uses and criteria for a set of waterbodies
2. Describe SABS effects on the waterbodies' designated uses
3. Select specific SABS and response indicators
4. Define potential ranges in value of the SABS and response indicators
5. Identify a response indicator value that protects the designated use
6. Analyze and characterize SABS - response associations
7. Explain decisions that justify criteria selection
Table 7. Specific applications of the methods used in the hypothetical model for criteria
development and application.
Empirical Classification
Fluvial Geomorphology
Relative Bed Stability
Controlled Experiments
Field Observations
Conditional Probability Analysis
Waterbody Use Functionality
Application/Use
To characterize range of biological, physical, or
chemical conditions
To verify stream type classification
To classify waterbodies with similar sediment
dynamics
To evaluate observed against expected stream bed
particle size characteristics
To evaluate threshold of impact
To confirm a plausible effect given the exposure
frequency, duration and magnitude
To establish thresholds and criteria
Possibly to classify waterbodies
To establish thresholds and criteria
The examples below illustrate how several methods are used together to develop independent
response ranges and identify criteria based on thresholds of effects. That is, a combination of
classification, controlled laboratory findings, departure from reference condition, and
associations derived from in-stream measurements all play a part. When different quantitative
methods result in values that are similar, there is greater confidence the criteria will be protective
of the designated use. Different methods are italicized and bolded at each appearance to
emphasize the roles they play individually and together in the development process. Note that all
numbers are hypothetical and are included, not to recommend criteria values but rather to more
clearly demonstrate the decision process.
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III.E.l. Example: Northeastern Headwater Streams
In this scenario, we assume that a resource manager is developing criteria for a statewide set of
2nd or 3rd order, high gradient headwater streams. These streams had been grouped by similarity
in form and function during a statewide classification of all waterbodies, based on & fluvial
geomorphology method. The headwaters class contained high gradient systems that move
substrates of widely varying sizes during storm events. These were small streams with mostly
cobble/gravel bed materials and sediment transport that were limited by competence (critical
shear stress). Despite the high gradient of the streams and the predominantly coarse bed
materials and natural tendency to export rather than accumulate sediment, substantial sources of
fine sediment may exist in the watershed, banks and bed. Moreover, in- and near-channel
disturbances combined with 'flashy' high-flow patterns were capable of mobilizing excessive fine
sediment loads thereby causing channel alterations, bank instability, and subsequent biotic
impairments in these streams.
Step 1. Review current designated uses and criteria for a set of waterbodies:
The major designated use of these streams is a cold-water fishery. No specific criteria existed for
SABS indicators. The designated use was stated in very general terms and the resource manager
decided to refine it as 'support of spawning populations of native brook trout' to distinguish it
from 'seasonal survival of stocked trout'. Continuing to meet this designated use is dependent on
many attributes of stream condition, such as sufficient depth, flow, clarity, and oxygenation;
clean gravels for spawning; sufficient habitat and cover for invertebrates and small fish, as well
as the trout themselves; an appropriate water temperature regime; and the absence of other
conflicting or incompatible uses. Excessive sediment loads can affect several of these attributes
at sensitive life stages.
Step 2. Describe SABS effects on the waterbodies' designated uses:
To begin the process, the resource manager considered the potential ways that excess sediment
could adversely affect the brook trout fishery. The resource manager identified several
mechanisms that could reduce trout survival: (1) physical abrasion by suspended particles, (2)
decreased visibility reducing successful sight-feeding, (3) reduced prey capture due to low
abundance of prey from the lack of suitable habitat for invertebrates, (4) poor
reproduction/recruitment through the loss of spawning habitat or damage to the eggs or sac fry,
(5) increased width/depth ratio, lower pool frequency and depth due to sediment deposition,
reducing the abundance and quality of territory for adult and juvenile trout; and (6) increased
maximum water temperatures associated with the deposition-driven increased width/depth ratio,
causing decreased DO and lethal or sub-lethal effects (e.g., disease, crowding at cool seeps) on
adult fish. These mechanisms were depicted in a conceptual model, which was useful for
illustrating the relationships among the SABS, designated uses, and potential measurements to
quantify the associations (Figure 15). The resource manager conducted a literature review to
support the linkages described in the conceptual model and discovered a variety of observed sub-
lethal effects for brook trout including inhibition of prey capture, growth, and egg survival. A
review of available data sets revealed that these exact measurements were not monitored in the
state's own studies though reasonable surrogates were noted. As a result, our hypothetical
resource manager considered what types of data were available to use or what could reasonably
be developed in the context of a variety of possible methods for criteria development.
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Step 3. Select specific SABS and response indicators:
In this step the resource manager selected measurements that defined the impairment as well as
the suspended or bedded sediment measurements. The resource manager knew that selection
could be based either on previously established designated use criteria or could be independently
established. The resource manager recognized that the absence of brook trout would be the most
definitive threshold, but significantly reduced populations could also be documented and
defended as impairments.
In this hypothetical case, the conceptual model illustrates that three response indicators were
identified: (1) the presence of brook trout, (2) reproductive success, and (3) available prey. The
resource manager needed to select appropriate measurements for these response indicators. The
resource manager selected density of adult brook trout as a direct measure of the designated use.
For assessing reproductive success, the resource manager chose the percent survival to swim-up
stage because this addresses a life stage of the brook trout that is sensitive to SABS and is
feasible to measure. For prey availability, the number of Ephemeroptera, Trichoptera, and
Plecoptera (EPT) insect taxa was considered a reasonable surrogate although some of these
species are not normally brook trout prey and the number of species may not necessarily
represent either abundance or availability as prey for trout. These uncertainties were noted in the
decision record.
Likewise, data for prey capture and abundance may be unavailable or too costly to measure, and
we assume that this is the case for our hypothetical case. Inspection of the conceptual model
suggested that, at a minimum, there should be one SABS indicator for suspended sediments as
well as an indicator for bedded sediments. The resource manager selected turbidity (NTU) for
water clarity and percent fines for settled particles, based on the availability of data in the region
and based on reported mechanistic and exposure/response associations between turbidity and
percent fines and effects to salmonids and invertebrates. The resource manager documented two
reasons for his decision to use these SABS indicators: (1) based on the literature, low levels of
turbidity and percent fines were linked with trout spawning success and macroinvertebrate prey
productivity, and (2) data for analysis regarding turbidity, percent fines, density of trout and the
macroinvertebrate assemblage were readily available from both state studies and EMAP.
Step 4. Define potential ranges in value of the SABS and response indicators
In our case, we will assume that the EMAP data set had more than 100 sample locations in cold,
headwater streams where fish surveys were conducted along with benthic macroinvertebrate
sampling, water quality analysis, and characterization of physical habitat. To determine the range
of indicator values that are possible for the waterbody class, the empirical classification method
was used. First, non-SABS parameters were
selected to identify high quality reference streams.
The resource manager used both land cover (high
percent natural) and water quality (low
conductivity and metals concentrations) criteria.
Through GIS analysis and database queries, the
resource manager identified 25 sites with more
than 95% natural land cover, specific conductance
less than 100 uS/cm, and no exceedances of U.S.
All numbers used in these
examples are hypothetical and
are included not to recommend
criteria values but rather to
more clearly demonstrate the
decision process.
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EPA hardness adjusted metals criteria. These 25 sites were considered to be minimally impacted
and were representative of as nearly natural conditions as was available. Additional parameters
were examined in the reference sites to confirm the classification and to minimize the influence
of other potential stressor sources. The resource manager sought evidence of cold water
temperatures throughout the year, suitable hydrologic conditions, the absence of point sources or
development, excellent water quality including low levels of contaminants, high concentrations
of dissolved oxygen, and a forested riparian zone. No further classification was deemed
necessary after examining the reference data.
Natural indicator ranges were plotted for these 25 sites and were compared to ranges of the same
indicators in the 75+ remaining sites. For most of the indicators plotted, the reference distribution
overlapped partially with the non-reference distribution, with the ranges of non-reference values
showing a greater percentage of sites with "worse" SABS and biological conditions. These
findings suggested that some sites had conditions that were closer to the natural potential than
others and that the tested indicators may be reasonable measurements for assessing SABS and
biological conditions. There were consistently three to four reference sites that had poorer
indicator values than the remaining data and the resource managers decided to use the 75th
percentile of SABS data and the 25th percentile of biological data to describe reasonable
expectations for the natural potential. The few sites with poorer indicator values could not be
associated with a consistent source of variability.
Step 5. Identify a response indicator value that protects the designated use
Three biological measures were selected as response indicators: (1) The 25th percentiles of the
distributions were 4.3 adult brook trout per 100 square meters, (2) 15 EPT taxa, and (3) percent
survival to swim-up stage. In this hypothetical example, percent survival to swim-up stage was
not measured in the field because it would require destructive sampling. For this response
indicator, literature suggested that 86% survival was adequate for sustained reproduction.
Additional literature review supported the state's findings regarding adult trout densities, with a
mean value of 6.2 fish/100 square meters in productive trout streams averaged over three studies.
The EPT richness values in reference sites were found to be similar in cold water streams of
neighboring states.
These numbers are for illustration purposes only and are not meant to represent actual targets.
The 25th percentile of reference values were therefore established as response indicator
transition points between attainment and non-attainment of the designated use (i.e., support of
spawning populations of native brook trout). Below, the completion of the hypothetical case
using the multi-step process is discussed separately for suspended sediments and for bedded
sediments, with reference to the individual methods used to develop the criteria for each.
Suspended Sediment Criterion Development
In this case, two exposure-response techniques (controlled experiments and field observations)
are used in combination to complete the development of a criterion for suspended sediment.
Step 6. Analyze and characterize SABS - response associations
To use the controlled experiment method to define the association between SABS indicators and
biological responses, the resource manager carefully reviewed the scientific literature for
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independent reviews, reports, and peer-reviewed publications linking specific levels of turbidity
and suspended solids to adverse responses of salmonids including brook trout. In the tradition of
criteria-setting based on controlled laboratory tests of chemicals, the most sensitive life stage of
the brook trout was selected as the specific response measurement whenever possible.
Fortunately for our resource manager, studies that extended from fertilization to the swim-up
stage for brook trout were available. The resource manager identified three high quality studies
that were based on (1) high percentage of survival in controls, (2) appropriate statistical analysis,
and (3) clear documentation. Since the thresholds for significant effects for 86% survival from
the three studies were within the same order of magnitude, the geometric mean was calculated
and, for illustrative purposes, it was assumed to be 8 NTU. In addition, physiological condition
studies were examined and assumed effects were reported between 3 and 10 NTUs. Although
this might be sufficient to set a suspended sediment criterion and thereby define impairment,
additional evidence would strengthen the confidence in the decision. Thus, in our hypothetical
case, the resource manager decided to use another analytical method to confirm the
exposure/response analysis.
There are several ways that the field observational methods can be used to partially characterize
SABS-response indicator associations. For the sake of brevity, we only illustrate one here, the
conditional probability analysis (CPA) method. The analysis depended on multiple field-
collected samples that should include a measure of SABS and a measurement of the designated
use. In our hypothetical case, the resource manager wanted to determine the turbidity level at
which adult brook trout density is reduced below 4.3 fish/lOOm2, the transition point identified in
step 5. So, the resource manager plotted turbidity on the x-axis and brook trout density on the_y-
axis, performed a quantile regression analysis, and recorded the maximal trout abundance given
an observed level of turbidity.
For our hypothetical case using the data set of more than 100 sample locations in headwater
streams, the analysis indicated that during low flow conditions adult brook trout only occurred in
streams with less than 20 NTUs. Furthermore, a strong association between turbidity and brook
trout density was found using the state's own data with a reduction to 4.3 fish/100m2 occurring
between 12 and 15 NTUs. The greatest densities were observed between 3 and 10 NTU. These
turbidity levels were compared with results of the controlled experiment method described
previously.
An additional method was applied based on a separate data set: creel surveys of fly fishermen.
The survey showed that most fishing on popular trout streams occurred only when stream
turbidity was less than 5 NTU. Results from the questionnaire of fly fisherman revealed that their
decision to fish or not to fish was based on perceived fishing success attributed to the visibility of
their trout flies to the brook trout.
Step 7. Explain decisions that justify criteria selection
In this hypothetical case, two response indicators were evaluated, survival to swim-up stage from
controlled experiments reported in the scientific literature and density of brook trout based on
exposure/response analysis of field observations. Based on these two different types of
information presented in the scenario, our hypothetical resource manager drafted his decision as
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well as the rationale for that decision. A decision table (Table 8) is valuable for illustrating the
benefits and drawbacks of alternative criteria levels. The turbidity levels associated with the
transition points of the response indicators were 8 NTU for 86% survival of swim-up fry and 12-
15 NTU for adult densities of 4.3 fish/100 square meters. The resource manager decided that 15
NTU was not sufficiently protective since adverse effects appeared to have occurred in streams
in the state at or near that level. The resource manager might also consider that although 5 NTU
may have an economic benefit on recreational fisheries, this level of water clarity may be
difficult to achieve and was lower than necessary to protect the fishery because the state's own
data clearly showed that brook trout could thrive in waters as high as 10 NTU. Since the duration
and frequency of the exposures in the field was uncertain, the resource manager decided to adopt
8 NTU as a reasonably protective criterion based on controlled laboratory studies on the most
sensitive life stage and because this value was within the range in which high quality trout
fisheries were reported for the state. Additional site specific testing for extent and duration would
be addressed on a site-by-site basis.
Table 8. Decision rationale for selecting a suspended sediment criterion.
Potential
criterion (NTU)
15
10
8
5
Advantages
Brook trout were present at this
value based on the state's
monitoring data.
Value is the geometric mean
threshold in controlled laboratory
exposures.
Value may have an economic
benefit.
Disadvantages
Value was not sufficiently protective
since adverse effects occurred at or
near that level in the state's streams.
Value may be lower than necessary
to protect the fishery. Value may be
difficult to achieve.
This hypothetical scenario illustrates the approach and reasoning for indicator selection, data
analysis and suspended sediment criterion selection. Another alternative might be to use species
sensitivity distribution curves to derive a criterion that is protective of 95% of species; and there
are still other alternatives. What is essential is that the scientific analysis be sound and the
rationale for decision-making transparent, logical, and defensible. Remember that this is a
hypothetical example and values are not based an actual analysis of the literature or data sets.
Bedded Sediment Criterion Development
In this case, the conditional probability analysis (CPA), fluvial geomorphology, and relative
bed stability (RBS) methods were used to complete the development of a criterion for bedded
sediment.
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Step 6. Analyze and characterize SABS - response associations
The resource manager used the CPA method to determine the probability of observing reduction
below acceptable levels of EPT taxa (15 taxa). Percent fines was selected as the SABS
measurement for bedded sediment (Step 3). The resource manager could confidently apply the
CPA method because data were available from an EMAP study where sampling locations were
randomly selected. Results from the CPA indicated an 80% chance for the presence of fewer
than 15 species of EPT when the percentage of fine sediments (<0.06mm) exceeded 20%. There
was a 60% chance of fewer than 15 species of EPT when the percentage of sediments exceeded
10% fines. In a similar analysis using density of brook trout, there was an 80% chance of less
than 4.3 fish/m2 in cold water streams with less than 25% fine sediments and a 60% chance at
12% fine sediments.
The resource manager also knew that in a neighboring state restoration efforts were already
underway in two streams that had originally only supported stocked brook trout. The resource
manager of the study had used the fluvial geomorphology method to evaluate SABS in the two
streams and designed controls including stabilization of stream banks consistent with the on-
going adjustment of the channel toward a more stable form and the creation of in-stream
complexity by adding large boulders to the stream. Before implementing the controls, SABS and
biological response indicators were measured. After implementation, sampling continued at
regular intervals. Year-old trout were observed in one stream two years after intervention; the
percent fines had declined to 5%.
No recovery was seen in the second stream where percent fines were reduced but were measured
at 12%. The resource manager was unsure of the reason(s) why the second stream had not
recovered. Stressor(s) could include insufficient recovery to permit areas of down-welling and
up-welling, which are necessary for spawning, or insufficient recovery time to reduce the levels
of percent fines. Although this was not enough information to use in development of alternative
criteria, the resource manager recognized its value in providing some quantitative response data
consistent with the results from other methods, providing SABS measures that were more closely
related to problematic SABS source locations (e.g., the unstable banks) and thereby helping him
target restoration actions more effectively, and providing valuable post-project monitoring
information.
The resource manager also recognized that he could apply the RBS method because fluvial
geomorphology data were also collected by a state agency and by EMAP. These measures
included ongoing channel adjustment, bank instability, and dominant bed particle size along with
channel gradient and other measures to help classify the waterbody type. The channel
morphology data provide an opportunity to characterize a range of values for headwaters streams
for percent fines and RBS measures. In particular, the RBS data set provided him with
information on the abiotic sediment regime in its characterization of expected bed composition
and particle sizes, and a range of departures from reference exemplified by the observed bed
composition.
As a comparison with the other methods that analyze associations with percent fines, the
resource manager determined whether thresholds occurred at a relatively consistent RBS ratio
value. The resource manager also noted that results from such an analysis might demonstrate
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suitability of a selected RBS value associated with an effects threshold as an alternative criterion
for percent fines. Further, the resource manager planned to look for associations among the RBS
values, embeddedness, and geomorphic indicators of ongoing channel instability and adjustment,
in the possibility that these can either cross-validate or provide additional criteria alternatives in
the future.
Step 7. Explain decisions that justify criteria selection
The resource manager knew from the adjacent state's experience that a reduction to 5% fines
could restore a fishery, but the exact threshold was still very uncertain and based on only one
stream that had recovered and one that did not. The resource manager also knew that the choice
of a probable effect level was critical to a decision. A decision table (Table 9) is valuable for
illustrating the benefits and drawbacks of alternative criteria levels. If the resource manager
chose the 80% level (20 - 25% fines) he/she would have a high probability of losing the trout
fishery. The resource manager believed that he/she could demonstrate to the water director the
economic and political efficacy of setting the threshold at a 60% effect level (10-12% fines),
which would be more protective. Percent fines at this level still posed some risk to the fishery, so
the resource manager recommended that the lower end of the range (10%) be selected as a
provisional criterion and that the criterion should be revisited after data were collected from
several streams in his state that he/she knew would require TMDLs and restoration. The resource
manager recommended careful monitoring of streams during the provisional period and after the
criterion was implemented. The 10% fine sediment provisional criterion was selected as a
reasonably protective level for the support of brook trout.
Table 9. Decision rationale for selecting a bedded sediments criterion
Potential
Criterion
(percent fines)
20-25%
10-12%
10%
5%
Advantages
More likely to be protective
Unstocked, juvenile trout
observed in similar fishery after
5% fines were achieved
Disadvantages
80% chance of loss invertebrate food
base and reduced fishery, may require
costly stocking due to lack of survival
of early life stages
60% chance of loss of fishery. No
recovery in similar fishery at 12%
fines.
More difficult to achieve than a more
relaxed criterion.
More difficult to achieve than a more
relaxed criterion.
Scenario Summary
In this hypothetical scenario, the SABS criteria established for headwater streams were
developed and confirmed using statewide and regional data sets. We could imagine that a limited
statewide analysis validated the regional study and that the criteria of 8 NTUs for suspended
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sediments and 10% fines for bedded sediments were adopted as standards for headwater streams
with the native cold-water fisheries designation throughout the state.
This scenario illustrated a variety of applications of the methods discussed throughout this
Framework but these do not constitute all the roles each might potentially play. For more
detailed examples of applications of the individual methods, see Section HID.
III.E.2. Abbreviated Examples
SABS criteria can be developed using the multi-step process and these same general methods for
any waterbody type. To avoid redundancy, other waterbody types are presented in a much
shorter format than for headwater streams.
Large Rivers
Large rivers (e.g., fifth order or greater) collect and transport SABS in ways inherently different
than the smaller headwater streams. Sediments may reach the larger and lower gradient
watercourses through upstream sources as well as erosion from the intensive land uses
(agriculture and urban development) that are prevalent in wide, gently sloping valleys. The
predominant bed material would be composed of gravel and smaller size particles that could be
suspended or moved with small flow increases. Deep pools and large quantities of water allow
for designated uses such as drinking water supply and primary contact recreation (swimming and
boating). Aquatic life uses shift to warm water species (e.g., bass fisheries) and the benthic
macroinvertebrate community is fundamentally different compared to upstream.
Resource managers will be faced with a separate SABS criteria development effort for the large
river waterbody type or class to address unique designated uses and different expectations for
SABS indicators and the biotic assemblages. This separate effort will follow the same multiple
steps described in Section III.B of this Framework. SABS indicators and criteria development
approaches for large rivers may differ from the scenario above. Indicators pertaining to
suspended sediments (TSS, turbidity, clarity) may be more universally applicable than measures
of bedded sediments. However, some large rivers may have a certain degree of cobble and larger
substrates that should be preserved or restored as important habitat. All the previously described
methods for SABS criteria development could be applied to large rivers, including the waterbody
use functionality method, which has limited applicability in headwater streams. Waterbody use
functionality drives criteria development efforts for the uses not pertaining to aquatic life (e.g.,
navigation, drinking water source, and recreation). Turbidity/suspended sediments should be low
enough to allow efficient water filtration for drinking water, and water clarity must allow
visibility that is safe for swimmers and boaters.
Regulated Rivers
Dams that disrupt river flow to create reservoirs also block the flow of sediments. Cobble, heavy
gravel, and sands can build up behind dams, causing channel armoring and a deficiency of
sediments below dams. While these changes can result in alterations to water quality, the major
impacts are on habitat for fish and benthic macroinvertebrates as measured by the composition of
the substrate. The RBS method can yield effective indicators of substrate changes below dams.
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After examining RBS values in areas unaffected by dams (empirical classification) as well as
scientific literature regarding sediment alterations caused by dams, a SABS criterion based on
RBS could be established, above which altered sediment supplies and channel armoring would
be indicated.
Wetlands
Riparian wetlands in side channels and floodplains are critical habitat for fish spawning and for
amphibians that lay egg masses on stable substrates. Because wetlands are natural deposition
zones for sediments, bedded sediment criteria for stream channels would not be appropriate for
the adjacent wetlands. Instead, the Sediment Risk Index (SRI, U.S. EPA 2002) could be used as
an indicator. The indicator, based on predicted soil erosion and delivery from agricultural lands,
could be correlated with metrics from amphibian surveys. A criterion could be established based
on field observation methods that demonstrate associations between the SRI and the presence of
sensitive frog species. Turbidity criteria that might be applied in the main channel would not be
applicable in the wetlands because water turnover rates are generally slower and fine clays can
remain in suspension for longer periods.
Lakes, Ponds, and Reservoirs
Natural lakes and ponds would likely be designated for aquatic life use such that naturally
occurring species could survive and reproduce, providing opportunities for recreational fisheries
and wildlife observations. These waterbodies would vary considerably in SABS conditions and
might require classification based on size and substrate type.
For aesthetic purposes related to aquatic life and recreational uses, Secchi depth was selected as
an indicator of water clarity. This measure is easy to understand from an aesthetic perspective; it
is a visual estimate of the depth of water through which a black and white disk can be seen. A
criterion was established such that the Secchi disk must be visible at a minimum depth of four
feet. This allows sufficient clarity in recreational waters to provide visual appeal, recreational
opportunity, enjoyment, and safety (Smith and Davies-Colley 1992). Secchi depth also indicates
planktonic density. This aspect of the measure needs consideration when management options
are recommended because both excess sediment supply and high nutrient concentrations can
cause shallower Secchi depth readings.
Many lakes and ponds are actually reservoirs created to provide hydropower, drinking water
supply, and agricultural water supply. Secondary uses include non-contact recreational use. Low
turbidity is required for efficient operation of pumps, turbines, filters, and treatments; and water
clarity can be desirable for aesthetic reasons. Therefore, the waterbody use functionality method
can be used for setting criteria for these designated uses. Criteria for bedded sediments may not
be required if reservoir capacities are not threatened by excessive sedimentation and lakebeds are
naturally composed of fine materials.
Estuaries
Bass fisheries, shellfish, and submerged aquatic vegetation (SAV) beds that provide critical
habitat are valued resources in estuaries. SAVs represent one of the components of the estuarine
ecosystem that is most sensitive to increases in SABS. A criterion based on water clarity would
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(if attained) provide conditions for optimal growth and reproduction of SAVs and would not
impair other habitats and organisms.
Criteria could be developed using the field observations method. In an example from the
Potomac estuary and the Chesapeake Bay, existing studies were compiled in a worldwide
literature synthesis. The criteria derived from the literature were evaluated with site-specific field
studies, model simulation, and diagnostic tools (see example in Section III.D.3). The criteria
were stratified by depth and salinity regime and adjusted by season. The final criteria used
percent light through water (PLW) as the indicator and had a range of 13-22 PLW.
Estuarine Wetlands
Emergent wetlands that line estuaries and bays may also be subject to excessive SABS effects.
Water clarity may not be an issue in these generally shallow waterbodies, but sediment
accumulation as it affects anadromous fish spawning may require establishment of criteria for
bedded sediments. If the majority of sediments settling in the wetlands come from upland
sources, as opposed to suspended sources flowing in from the deeper estuary, then an indicator
of sediment supply (such as the Sediment Risk Index) may be appropriate for the estuarine
wetlands as it was for the wetlands in the upper parts of the watershed.
Coastal Waters
Natural marine sediment supplies as well as discharge from the estuary and other smaller rivers
and streams heavily influence SABS conditions at the mouth of the estuaries and in other coastal
waters. Criteria established in the contributing waterbodies may be considered sufficient for
protecting designated uses for coastal waters and beaches. Some states may have sensitive
aquatic life (corals), ecologically significant coastal wetlands, and economically important
recreational uses (beaches) that merit protection that is not provided through criteria applied to
the contributing waterbodies. Classification could be guided using the Classical Framework for
Coastal Systems (U.S. EPA 2004). This framework includes conceptual models of SABS
impacts in coastal areas that would be a good starting point for criteria development.
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Schumm, S.A, M.D. Harvey and C.A. Watson. 1984. Incised channels: morphology, dynamics
and control. Water Resources Publications, Littleton, CO. 200 pp.
Simon, A. 1989. A model of channel response in disturbed alluvial channels. Earth Surface
Processes andLandforms 14(1): 11-26.
Simon, A. 1992. Energy, time, and channel evolution in catastrophically disturbed fluvial
systems. Geomorphology 5:345-372.
Simon, A. and C.R. Hupp. 1986. Channel evolution in modified Tennessee streams.
Proceedings, Fourth Federal Interagency Sedimentation Conference, March, 1986, Las
Vegas, Nevada, v. 2, p. 71-82.
Simon, A. and C.R. Hupp. 1992. Geomorphic and vegetative recovery processes along modified
stream channels of West Tennessee. United States Geological Survey Open-File Report
91-502.
Simon, A., W. Dickerson and A. Heins. 2004. Suspended-sediment transport rates at the 1.5-year
recurrence interval for ecoregions of the United States: Transport conditions at the
bankfull and effective discharge? Geomorphology 58:243-262.
Simons, D.B. and F. Senturk. 1977. Sediment Transport Technology. Water Resources
Publications. Fort Collins, CO. 807 pp.
Singleton, HJ. 1985. Water Quality Criteria for Particulate Matter: Technical Appendix.
Ministry of the Environment, Lands, and Parks, Victoria, B.C. pp. 1-82.
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Singleton, H. 2001. The British Columbia Ambient Water Quality Guidelines (Criteria) for
Turbidity, Suspended and Benthic Sediments. Available at:
http://www.env.gov.bc.ca/wat/.
Smith, D.G. and RJ. Davies-Colley. 1992. Perception of Water Clarity and Color in Terms of
Suitability for Recreational Use. Journal of Environmental Management 36(2):226-235.
Stahl, C.H., A. J. Cimorelli and A.H. Chow. 2002. A new approach to environmental decision
analysis: multi-criteria integrated resource assessment (MIRA). Bulletin of Science,
Technology and Society 22(6):443-459.
Staver, L.W., K.W. Staver and J.C. Stevenson. 1996. Nutrient Inputs to the Choptank River
Estuary: Implications for Watershed Management. Estuaries 19:342-358.
Stephan, C.E., D.I. Mount, DJ. Hansen, J.H. Gentile, G.A. Chapman and W.A. Brungs. 1985.
Guidelines for deriving numerical national water quality criteria for the protection of
aquatic organisms and their uses. PB85-227049. National Technical Information Service,
Springfield, VA.
Stevens, L.E. 1995. Flow regulation, geomorphology, and Colorado River marsh development in
the Grand Canyon, Arizona. Ecological Applications 5:1025-1039.
Stoddard, J.L., D.V. Peck, S.G. Paulsen, J. Van Sickle, C.P. Hawkins, A.T. Herlihy, R.M.
Hughes, P.R. Kaufmann, D.P. Larsen, G. Lomnicky, A.R. Olsen, S.A. Peterson, P.L.
Ringold and T.R. Whittier. 2005. An Ecological Assessment of Western Streams and
Rivers. EPA 620/R-05/005, U.S. Environmental Protection Agency, Washington, DC.
Trimble, S.W. 1974. Man-induced soil erosion on the southern Piedmont, 1700-1970. Soil
Conservation Society of America.
Trimble, S.W. 1999. Decreased rates of alluvial sediment storage in the Coon Creek Basin,
Wisconsin 1975-1993. Science. 285:1244-1246.
Troendle, C.A., D.L. Rosgen, S.E. Ryan, L.S. Forth and J.M. Nankervis. 2001. Developing a
"reference" sediment transport relationship. Proceedings 7th Interagency Sedimentation
Conference, March 25-29, 2002, Reno, NV.
U.S. EPA. 1980. Water Quality Criteria Documents. Federal Register 45:79318-79379.
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Washington, DC. Available at: http://www.epa.gov/waterscience/criteria/goldbook.pdf
U.S. EPA. 1993. Guidance Specifying Management Measures for Sources of Nonpoint Pollution
in Coastal Waters. EPA 840-B-92-002. U.S. EPA, Office of Water, Washington, DC.
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U.S. EPA. 1994. Interim Guidance on Determination and Use of Water Effect Ratios for Metals.
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U.S. EPA. 1998. National Strategy for the Development of Regional Nutrient Criteria.
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Office of Water, Washington DC. 132 pp.
U.S. EPA. 2000a. Draft Technical Framework to Support the Development of Water Quality
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Region 3. Philadelphia, PA. 364 pp.
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Strengthen the Foundation for Protecting and Restoring the Nation's Waters. Office of
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Copper, Lead, Nickel, Silver and Zinc). EPA-600-R-02-011. U.S. EPA, Office of
Research and Development. Washington, DC.
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U.S. EPA. 2005b. Draft Handbook for Developing Watershed Plans to Restore and Protect Our
Waters. EPA-841-B-05-005. U.S. EPA, Office of Research and Development.
Washington, DC.
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Fisheries Society Monograph 7. American Fisheries Society, Bethesda, MD.
Wilber, D.H. and D.G. Clarke. 2001. Biological effects of suspended sediments: a review of
suspended sediment impacts on fish and shellfish with relation to dredging activities in
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American Geophysical Union 35(6):951-956.
Wood, PJ. and P.D. Armitage. 1997. Biological effects of fine sediment in the lotic
environment. Environmental Management 21 (2):203-217.
Yuan, L. 2006. Estimation and application of macroinvertebrate tolerance values. U.S. EPA,
Office of Research and Development, National Center for Environmental Assessment,
Washington, DC. (in preparation).
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Appendix A
Glossary of Terms
Aquatic Life Use- A use designation in state/tribal water quality standards that generally
provides for survival and reproduction of desirable fish, shellfish, and other aquatic organisms;
classifications specified in state water quality standards relating to the level of protection
afforded to the resident biological community.
Bedload- Sediment that moves along and is in contact with the stream or river bottom.
Clean sediments- Suspended and bedded sediments that are not contaminated with toxicants.
Contaminated sediments- Deposited or accumulated sediments, typically on the bottom of a
waterbody, that contain contaminants. These may or may not be toxic as revealed by a whole
sediment toxicity test or as predicted by equilibrium partitioning.
Controlled experiment- An experiment in which replicate experimental units (e.g., organisms,
sediment microbial communities, or colonized rock baskets) are randomly assigned to treatment
groups that receive controlled levels of exposure to an agent and responses of interest are
observed.
Criteria- Under section 304(a) of the Clean Water Act, U.S. EPA publishes scientific
information regarding concentrations of specific chemicals or levels of variables in water that
protect aquatic life and human health.
2Criteria- Levels of individual pollutants, water quality characteristics, or descriptions of
conditions of a waterbody, adopted into state water quality standards that, if met, will generally
protect the designated use of the water. In many cases, states make use of the criteria developed
by U.S. EPA as described in the first definition of criteria.
Designated Uses- Those uses specified in state/tribal water quality standards for each waterbody
or segment, whether or not they are being attained. The term is sometimes referred to as
Beneficial Uses, (i.e., desirable uses that water quality should support). Examples are drinking
water supply, primary contact recreation (such as swimming), and aquatic life support.
Embeddedness- The degree to which larger substrate particles (gravel, cobble and boulders) in
the bottom of a stream or river are surrounded by deposited sediment.
Erodibility- A soils sensitivity to the effects of wind and water on the soil structure.
Fines- Fine particulate material such as silt and clay particles typically of less than 0.85 mm
diameter though other diameters can be specified.
Fluvial Geomorphology- The study of the influence of flowing surface water on the Earth's
surficial sediments through the processes of erosion and deposition.
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Kurtosis- Kurtosis is the degree of peakedness of a distribution.
Nephelometric Turbidity Units (NTU)- The units of measurement for turbidity in water as
determined by the degree light is scattered at right angles when compared to a standard reference
solution.
Reference Condition- The condition that approximates a natural, unimpacted condition
(biological, chemical, physical, etc.) for a waterbody. Reference condition is best determined by
collecting measurements at a number of sites in a similar waterbody class or region under
undisturbed or minimally disturbed conditions (by human activity), if they exist.
Secchi disk- A black and white quadrant disk, typically 20cm in diameter, used to determine
water clarity by measuring the distance through the water column at which the disk disappears
and appears.
Sediment- Fragmented material that originates from weathering and erosion of rocks or
unconsolidated deposits, including organic material, and is transported by, suspended in, or
deposited by water.
Sedimentation- The deposition of sediment.
Settleable solids- Solids that will settle to the bottom of a cone-shaped container in a standard
time interval (e.g., an Imhoff cone in a 60-minute period).
Silt- Non-cohesive inorganic particles. Individual particles are not visible to the unaided human
eye (0.002 to 0.05 mm). Silt will crumble when rolled into a ball.
Siltation- The process by which a river, lake, or other waterbody becomes clogged with
sediment.
Suspended and Bedded Sediments (SABS)- Organic and inorganic particles that are suspended
in, are carried by, or accumulate in waterbodies. SABS are natural parts of aquatic systems and
cannot be considered as pollutants until they are out of balance, in excess or deficient.
Suspended load- Sediment that is derived from a river/streambed and is wholly or intermittently
supported in the water column by turbulence.
Suspended sediment- Very fine soil particles that remain in suspension in water for a
considerable period of time without contact with the bottom. Such material remains in
suspension due to the upward components of turbulence and currents and/or by colloidal
suspension.
Suspended-sediment concentration (SSC)- The dry weight of sediment from a know volume of
water-sediment mixture, typically expressed in milligrams per liter. Primarily fine inorganic clay,
silt, and sand, but also includes the well-decomposed organic matter typically found in soils.
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Total Suspended Solids (TSS)- Suspended organic and inorganic solids that are not in solution
and can be removed by filtration. Suspended solids usually contribute directly to turbidity.
Turbidity- The scattering of light by fine, suspended particles which causes water to have a
cloudy appearance. Turbidity is an optical property of water. More specifically, turbidity is the
intensity of light scattered at one or more angles to an incident beam of light as measured by a
turbidity meter or nephelometer.
Washload- Sediments smaller than 63 microns that are not from the bed but could be from bank
erosion or upland sources.
Water Quality Standards- Are provisions in state, tribal, or territorial law or regulations that
define the water quality goals of a waterbody, or segment thereof by (1) designating the use or
uses to be made of the water, (2) setting criteria necessary to protect the uses, and (3) protecting
existing water quality through anti-degradation policies and implementation procedures.
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Appendix B
Impacts of Suspended and Bedded Sediments (SABS)
SABS are a unique water quality problem when compared to most toxic chemicals, in that
suspended solids and bedded sediments (including the organic fraction) occur naturally in water
bodies in natural or background amounts and are essential to the ecological function of a water
body. Suspended solids and sediments transport nutrients, detritus, and other organic matter in
natural amounts that are critical to the health of a water body. Suspended solids and sediment in
natural quantities also replenish sediment bedloads and create valuable micro-habitats, such as
pools and sand bars. Therefore, a basic premise for managing suspended and bedded sediments
in water bodies to protect aquatic life uses may be the need to maintain natural or background
levels of SABS in water bodies.
However, SABS in excessive amounts constitute a major ecosystem stressor. According to the
U.S. EPA National Water Quality Inventory - 2000 Report, excessive sediment was the leading
cause of impairment of the Nation's waters. The highest frequency of impairment was reported
for rivers and streams, followed by lakes, reservoirs, ponds, and estuaries. In 1998,
approximately 40% of assessed river miles in the U.S. were impaired or threatened from
excessive SABS.
Suspended and bedded sediments have three major avenues of effect in aquatic systems: (1)
direct effects on aquatic life, (2) direct effects on physical habitat, which result in indirect effects
on aquatic life, and 3) effects on uses other than aquatic life, such as recreation or drinking water.
SABS can be broken down into suspended sediments and bedded sediments. In considering
impacts, suspended sediment is the portion of SABS that exert a negative impact via suspension
in the water column, such as shading of submerged macrophytes. Bedded sediments are those
sediments that have a negative impact when they settle out on the bottom of the water body and
smother spawning beds and other habitats. In discussions within the Framework, thresholds of
effects on biota are omitted because of high variability found in the literature, specificity of
application that cannot be explained in brief, and intentions to avoid bias in future criteria
development exercises. The following discussion is excerpted from Jha (2003). Comprehensive
reviews of the effects of SABS can be found in the scientific literature (e.g., Jha 2003; Berry et
al. 2003;Wilber and Clarke 2001; Waters 1995; Chapman 1988; Wood and Armitage 1997;
Newcombe and Jensen 1996; Nalepa and Quigley 1980).
Suspended sediments
-Direct effects on aquatic life
Suspended sediments can directly affect many components of the biota, including algae and
macrophytes, invertebrates, and fish. The increased turbidity associated with suspended
sediments can reduce primary productivity of algae as well as the growth and reproduction of
submerged vegetation. In some systems, increased sediment can lead to a shift from macrophyte-
dominated productivity to algal-dominated productivity.
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The direct effects of suspended sediments on invertebrates and fish are complex, ranging from
behavioral to physiological to lexicological. The severity of effect caused by suspended
sediments is a function of many factors, including sediment concentration, duration, organism
life history stage, temperature, physical and chemical characteristics of the particles, associated
toxicants, acclimatization, other stressors, and interactions of these factors. Suspended sediment
effects have been scored on a qualitative scale as severity of ill effect (SEV), and they include
everything from no behavioral effects (lowest on the scale) to behavioral effects (low on the
scale), to sublethal effects (higher on the scale), to lethal effects (highest on the scale)
(Newcombe and Jensen 1996).
Invertebrates may show behavioral, physiological, or toxicological responses to excess
suspended sediment. For example, invertebrate drift is a behavior that is directly affected by
increased suspended sediment load in freshwater streams. These changes may be associated with
a shift in dominance from Ephemeroptera, Plecoptera, and Trichoptera (EPT) insect taxa to other
less sediment-sensitive taxa of the benthic assemblage.
Suspended sediments also have a negative affect on the survival of freshwater mussels. Increased
levels of SABS impair ingestion rates of freshwater mussels. Laboratory studies have shown
that survival may be species-specific. Mussels compensate for increased levels of suspended
sediment by increasing filtration rates, increasing the proportion of filtered material that is
rejected, and increasing the selection efficiency for organic matter. Species-specific responses to
SABS are adaptations to sediment levels in the local environment, such that species inhabiting
turbid environments are better able to select between organic and inorganic particles. Many of
the endangered freshwater mussel species have evolved in fast flowing streams with historically
low levels of suspended sediment. Such species may not be able to actively select between
organic and inorganic particles in the water column. Therefore, even low levels of sediment may
reduce feeding and, in turn, reduce growth and reproduction.
Suspended sediments also affect fish populations. Two major effects of SABS on fish include (1)
behavioral effects, such as inability to see prey or feed normally and (2) physiological effects,
such as gill clogging. Certain fish populations may be severely impacted in their ability to feed
by even small increases in SABS concentrations because of increased turbidity. Fish that need to
see their prey to feed suffer from reduced visibility in turbid water and may be restricted from
otherwise satisfactory habitat.
Many species offish may relocate when sediment load is increased because fish can readily
disperse. Other behavioral responses include an increased frequency of the cough reflex and
temporary disruption of territoriality. The severity of the behavioral response is associated with
the timing of disturbance, the level of stress, decreased energy reserves, phagocytes, metabolic
depletion, seasonal variation, and alteration of the habitat.
Physiological effects of gill clogging can result in impaired growth, histological changes to gill
tissue, alterations in blood chemistry, and an overall decrease in health and resistance to
parasitism and disease. Lower doses or shorter duration of SABS will have transitory effects,
while higher doses for longer periods can result in more lasting and severe effects. Fish can also
swallow large quantities of sediment, causing illness, reduced growth and eventual death,
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depending on other contaminants that may be adsorbed to the sediment. Some other
physiological changes include release of stress hormones (e.g., cortisol and epinephrine),
compensatory response to decrease in gill function, and clogging gill mucus causing
asphyxiation and traumatization of gill tissue. The severity of damage appears to be related to the
dose of exposure as well as the size and angularity of the particles involved.
-Indirect effects on aquatic life
A potential problem with suspended sediment in reservoirs, coastal wetlands, estuaries, and near-
shore zones is decreased light penetration, which often causes aquatic macrophytes to be
replaced with algal communities, with resulting changes in both the invertebrate and fish
communities. A loss of macrophytes can represent a loss of habitat for certain species that use
them as protective refugia. Reduced light availability can also limit the feeding efficiency of
macroinvertebrates and fish. Invertebrates and fish may avoid areas of high turbidity or low light,
affecting community structure and dynamics.
-Effects on other designated uses
Excessive suspended sediments can affect designated uses other than aquatic life. Recreation can
be impacted if swimmers prefer clear water to turbid water, or if highly turbid water makes
swimming hazardous by hiding submerged objects. Anglers may be less able to see fish in turbid
water. Finally, excess sediments in waterbodies used for drinking water necessitate the use of
expensive filtration systems to make the water suitable for human consumption.
Bedded sediments
-Direct effects on aquatic life
Excessive bedded sediment can affect aquatic life in several ways. The effects of reduced
primary production on aquatic invertebrates and fishes at higher trophic levels are compounded
when SABS settles on remaining macrophytes. The macrophyte quality also is reduced as a food
source. Sea grasses and other submerged aquatic vegetation (SAV) are considered "keystone"
species in temperate and tropical estuaries and coastal areas. These flora have a variety of
beneficial attributes including providing food and shelter for many aquatic and terrestrial species.
For example, large-scale declines of submerged aquatic vegetation (SAV) in Chesapeake Bay are
directly related to increasing amounts of nutrients, and secondarily to sediments entering the Bay
(Staver et al. 1996). There also has been a worldwide decline in sea grasses including dramatic
regional losses in the Gulf of Mexico. When studied in detail, seagrass declines have always
been linked to nutrient enrichment as the most important cause, but suspended sediment remains
a suspected secondary cause in several cases.
Many species offish and macroinvertebrates use the interstitial spaces at the bottom of streams
to lay their eggs. Reproductive success is severely affected by sediment deposition particularly in
benthic spawning fishes. The primary mechanisms of action are through increased egg mortality,
reduced egg hatch and a reduction in the successful emergence of larvae. The cause of egg
survival rates and egg death are due to reduced permeability of the streambed and to burial by
settled particles. Thin coverings (a few millimeters) of fine particles are believed to disrupt the
normal exchange of gases and metabolic wastes between the egg and water.
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Sediment deposition has caused significant reduction in numbers and standing crop biomass in
large game fish because of increased vulnerability of their eggs to predation in gravel and small
rubble, reduction in oxygen supply to eggs, and increased embryo mortality. Differences in
sensitivity, egg mortality effects, early life stages (i.e., eggs, larvae) and magnitude of impact
upon fish population are associated with amount of elevated sediment loads, size of the sediment
particles involved, seasonal variation, and rates of sediment deposition. Even if intergravel flow
is adequate for embryo development, sand that plugs the interstitial areas near the surface of the
stream bed can prevent alevins from emerging from the gravel.
High and sustained levels of bedded sediment may cause permanent alterations in
macroinvertebrate community structure, including diversity, density, biomass, growth, rates of
reproduction, and mortality. Three major relationships between benthic invertebrate communities
and sediment deposition in streams have been reported, including correlation between abundance
of micro-invertebrates and substrate particle size, embeddedness of substrate and loss of
interstitial space, and change in species composition with change in substrate composition.
Specific effects on invertebrates include abrasion, clogging of filtration mechanisms, thereby
interfering with ingestion and respiration and, in extreme cases, smothering and burial resulting
in mortality.
In marine environments, corals differ greatly in their ability to resist SABS, with most species
being highly sensitive to even small amounts while a minority are able to tolerate extremely
embedded sediment conditions and a few are even able to live directly in sedimented bottoms.
Excessive sedimentation can adversely affect the structure and function of the coral reef
ecosystem by altering physical and biological processes through a variety of mechanisms. These
all require expenditure of metabolic energy and when sedimentation is excessive, organisms
eventually reach the point where they can no longer spare the energy to keep themselves clean,
and the affected tissues die back. Excess SABS cause reduced growth rates, temporary
bleaching, and complex food web-associated effects to reef dwelling organisms other than corals.
Coral larvae will not settle and establish themselves in shifting sediments. Increases in
sedimentation rates alter the distribution of corals and their associated reef constituents by
influencing the ability of coral larvae to settle and survive.
-Indirect effects on aquatic life
Some of the indirect effects of bedded sediments stem from the feeding mechanisms of aquatic
animals. Increases in sediment deposition that affect the growth, abundance, or species
composition of the periphytic (attached) algal community will also have an effect on the
macroinvertebrate grazers that feed predominantly on periphyton. For example in the Chattooga
River watershed, accelerated sedimentation was identified as the leading cause of habitat loss
and reduction in bed form diversity (Pruitt et al. 2001). Effects on aquatic individuals,
populations, and communities are expressed through alterations in local food webs and habitat.
When sedimentation exceeds certain thresholds, ensuing effects will likely involve decline of the
existing aquatic invertebrate community and subsequent colonization by pioneer species.
Increased sedimentation also may functionally shift the fish community from generalist feeding
and spawning guilds to more bottom-oriented, sediment tolerant fishes.
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-Effects on other designated uses
The build-up of deposited sediment can interfere with other designated uses besides aquatic life.
Sedimentation can interfere with habitat quality in all waterbody types, but particularly in
wetlands, where the water filtering capabilities may be affected. Over time, the deposition of
sediment can alter water tables and channel depths, affecting drinking water, agriculture, and
recreational and commercial boating and navigation. The removal of deposited sediments via
dredging is costly and may cause detrimental re-suspension of sediments.
Other SABS Effects
Effects of SABS on waterbodies result not only from excess SABS but also from SABS
starvation and changes in supply. Sediment starvation caused by structures such as dams and
levees is a problem in some ecosystems, ranging from the loss of native fish species and native
riparian ecosystem structure in many dammed western rivers (e.g., Colorado River, Platte River,
Missouri River) to the subsidence and loss of wetlands (e.g., Mississippi Delta in Louisiana).
Changes in the supply rate of sediment can cause drastic changes in aquatic, wetland, and
riparian vegetation. Undesirable changes in vegetation can be induced by both decreases and
increases in SABS from natural levels.
For example, in the Platte and Missouri Rivers, decreases in both sediment supply and scouring
flows have resulted in the growth of stable riparian forests (including many exotic eastern tree
species) and the loss of sandbar habitat for several wildlife species (e.g., cranes and piping
plovers) (Johnson 1994). In the Colorado River, decreased sediment supply (but continuing
scouring flow) has resulted in the loss of riparian wetland habitat dependent on sandbars
(Stevens 1995). The magnitude and timing of sedimentation may influence structure and
recolonization of aquatic plant communities.
In summary, the current literature suggests that imbalanced SABS contribute significantly to
detrimental effects on North American aquatic life and can impact other uses of waters.
Improved SABS criteria are needed to properly manage the level of SABS in aquatic ecosystems
to minimize or avoid these effects.
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Appendix C
State Needs Survey
Conducted in 2004
In September, 2004, a survey was conducted to solicit input from states on the status of SABS
related impairment and monitoring in their state, as well as technical, budgetary, and other needs
for developing numeric SABS criteria. One state was randomly chosen from each of the 10 U.S.
EPA regions. States initially contacted included New Hampshire (NH), New York (NY),
Delaware (DE), Louisiana (LA), North Carolina (NC), Michigan (MI), Kansas (KS), Wyoming
(WY), Oregon (OR), and California (CA). In each state, a person working with water quality
standards was contacted and sent the survey, which was often completed with the aid of people
working directly with water quality monitoring. In one case (Kansas), two state employees
responded with similar answers. The staff in Louisiana chose not to respond to the surveyor se,
but provided written responses that were modified into survey answers. The responses
summarized below are from the following states: NH, NY, DE, NC, MI, KS, WY, OR.
California did not respond.
STATE NEEDS SURVEY
Name
Telephone Number
Job position
Date
The U.S. EPA intends to publish a draft Framework for Developing Suspended and Bedded
Sediment (SABS) Water Quality Criteria. This survey is being conducted to summarize issues
regarding SABS criteria development that are important to the states. Please answer to the best of
your knowledge. If you cannot answer confidently, provide a reference to another state employee
that would be more qualified to answer. Though some questions are categorical, additional
comments are invited.
1. How would you characterize suspended and bedded sediment (SABS) related
water body impairment in your state?
(5) Major problem
(3) Minor problem
(0) Not a problem at all
2. What is the current status of criteria/standards for SABS in your state? Are they
fully implemented or under development?
Existing Under Development
(1) (0) No criteria or standards
(1) (0) Narrative criteria
(1) (1) Numeric criteria
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(5) (0) Standards with narrative criteria
(3) (0) Standards with numeric criteria
3. Are you applying SABS criteria now? In what capacity or which programs (e.g.,
requirements of the Clean Water Act, TMDLs, upstream/downstream
monitoring for discharges)?
KS: Kansas 305(b) reports and 303(d) lists have long recognized SABS-related impairments
in streams and reservoirs, but the extent of the problem has not been accurately reflected
in these documents. Most of the reported problems in streams have been identified
through biological monitoring efforts rather than through the state's more extensive
stream chemistry monitoring program. An expansion of the state's biological monitoring
program would undoubtedly paint a bleaker picture. (Historically, a TSS criterion of 100
mg/L was applied to streams in Kansas for diagnostic and 305(b) reporting purposes.
This BPJ-based criterion was ultimately abandoned owing to a general lack of supporting
scientific evidence.)
MI: Yes, Michigan is currently applying SAB type criteria under the NPDES program and the
surface water monitoring program.
NH: Not for benthic deposits. Streams: Photo documentation or BPJ for assessing impairment.
Yes, for turbidity. Primarily for episodic events related to construction. Ad hoc.
NC: Yes- CWA requirements, TMDL (turbidity -TSS); monitoring (NPDES and ambient)-
Lakes and Streams; Storm water
DE: No
NY: Yes, we are applying narrative sediment standards currently.
OR: We have done TMDLs for sediment. We require turbidity monitoring for some sources.
WY: Turbidity limits and monitoring are routinely required when appropriate on construction
sites. Limits for suspended solids (TSS) are also place on various industrial and
municipal discharge permits e.g., (coal mines, municipalities).
4. Do you feel there is a need for improving your water quality criteria for SABS?
KS: Definitely
MI: The current approach is working, however other options would be considered.
NH: I guess so for benthic deposits, no further development for turbidity
NC: Yes
DE: Not sure
NY: Numeric standards are preferable to narrative, but development of numeric standards is
not a high priority for NYS. We believe that our assessments done for aquatic life use are
appropriate and adequate. To protect the aesthetic quality of the waters, and recreation
and other best uses, the standards might be useful, but there are other higher priorities for
standards development in the state.
OR Yes
WY: There is always a need for improving WQ standards.
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5. If you have SABS criteria/standards, what is/are your indicator(s) for:
a. Suspended sediments: (6) turbidity
(5) total suspended solids
(1) light penetration
(1) other- secchi depth
b. Bedded sediments: (1) Wolman pebble counts
(3) embeddedness
( ) percent fines by volume
(2) percent fines by area
( ) silt depth
(1) substrate stability
( ) residual pool volume
(2) other - best personal judgement &
photos; intergravel dissolved oxygen
c. Biology (7) benthic macroinvertebrates
(4) fish
(3) periphyton
(1) other - mussels
6. What designated uses other than aquatic life uses do you feel are vulnerable to
SABS impairment in your state?
(3) Fish consumption
(5) Primary contact recreation
(3) Secondary contact recreation
(7) Drinking water supply
(0) Agriculture use
(2) Industrial use
(1) Navigation
7. Do you foresee specific technical/scientific problems with development or
application of SABS criteria in your state? If yes, please explain.
(5) Yes
(0) No
(3) Not sure
KS: Money and other resource issues may pose a far greater concern.
In agricultural regions, political opposition may pose an even greater
challenge (technical and scientific difficulties may seem minor by
comparison). U.S. EPA will need to convince the states that it is serious
about tackling this issue.
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NH: No expert on staff, what parameters, bedload, rate of erosion, deposition, embeddedness
tough to hang your hat on, for streams: rock baskets - if impaired - then pursue
sedimentation measure.
NC: Analytical techniques, background issues
NY: For bedded sediments, there will some difficulties
OR: Yes how to deal with natural variability; which are the best measures; what levels are
needed to protect threatened and endangered species, particularly salmonids
WY: The largest problem with sediment in Wyoming is clean sediment rather than
contaminated sediment and its effects on habitat. The issue is keeping sediment transport
in balance which is different for each stream system. This makes every decision site-
specific and usually requires more data than we can get to do it right.
8. The following elements/resources are potentially part of the draft Framework
for Developing SABS Criteria that is being considered. Please rate their utility
for your criteria development process as: very useful, somewhat useful,
unknown, not very useful, not at all useful.
Elements
a. Personnel/expertise
b. Money /grants
c. Existing criteria/standards
d. Technical documentation/manuals
e. Access to data on SABS effects from scientific
literature
f . S AB S data for your State
g. Analytical methods for converting narrative to
numeric criteria
h. Example case studies
i. Web-based communication with U.S. EPA and
others in criteria development process
j . Data management tools
^
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8
6
3
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6
5
4
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2
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5
5
2
2
3
5
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9. What other information, in addition to what is listed in the above table, would
you find useful for improving or deriving better numeric SABS criteria?
KS: In the assessment of aquatic life support, we would benefit from a
clearer knowledge of the sensitivity of different taxa and assemblages
to SABS exposure, that is, from the application of more widely
accepted biological indicators
MI: U.S. EPA derived SAB criteria and standards that included state
involvement.
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NH: Workshops
NC: Data specific to bedded sediments
OR: Clarity about what uses we're trying to protect at what level and which measures/criteria
are best suited to each purpose. A way to do this with as few criteria/measures as possible
and as simply as possible. Something that is implementable technically and from a
resource perspective. Assistance with how to deal with uncertainty and sublethal impacts.
How to deal with systems that are dynamic and with natural disturbance.
WY: I don't know.
Survey Respondents:
Delaware: Hassan Mirsajadi, Environmental Engineer, Watershed assessment, Department of
Natural Resource and Environmental Control
Kansas: Robert T. Angelo, Chief, Technical Services Section, Bureau of Environmental Field
Services, Kansas Department of Health and Environment; and Bret Holman, Kansas Water
Quality Standards Coordinator, Kansas Department of Health and Environment
Louisiana: Kristine Pintado, Environmental Scientist, Office of Environmental Assessment,
Department of Environmental Quality
Michigan: Sylvia Heaton, Senior Aquatic Biologist, Water Quality Standards Coordinator,
Department of Environmental Quality
New Hampshire: David Neils, Biologist, Department of Environmental Services
New York: Margaret Novak, Chief, Statewide Waters Monitoring Section, Department of
Environmental Conservation
North Carolina: Dianne Reid, Environmental Biologist, Supervisor, Intensive Survey Unit,
Department of Environment and Natural Resources; and Connie Brower, Environmental
Chemist, Classifications and Standards Unit, Department of Environment and Natural Resources
Oregon: Debra Studevant, Water quality standards coordinator, Department of Environmental
Quality
Wyoming: Bill DiRienzo, Watershed Program Supervisor, Department of Environmental
Quality
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Appendix D
SABS-Related Criteria for Surface Water Quality
D.I Examples of Approaches Currently in Use or Under Development in States and
Internationally
Idaho:
In Idaho, as in many states, new numeric criteria must comply with existing narrative WQS, such
as: "Sediment shall not exceed quantities ... which impair beneficial uses" (IDAPA
58.01.02.200.08). One of the important beneficial uses of Idaho streams is production of trout
and salmon for ecological and recreational purposes. Although macroinvertebrate and fish
community integrity are measured in Idaho (using the Stream Macroinvertebrate Index and the
Stream Fish Index), these measures are not currently used as indicators of SABS impairment.
Rather, the state considers as indicators water column and instream measures that change with
increasing fine sediments and are known to affect growth, survival, reproductive success, and
habitat suitability of salmonids and other aquatic. These include decreases in light penetration,
riffle stability, and intergravel dissolved oxygen, and increases in turbidity, total suspended
solids, embeddedness, extent of streambed covered by surface fines, and percent subsurface fines
in potential spawning gravels. Target levels for these measures are based on relationships in the
scientific literature (primarily from studies in the Northwestern U.S.), background conditions in
Idaho streams, and existing Idaho WQS (Idaho DEQ 2003).
New Mexico:
New Mexico recently developed a draft protocol to support an interpretation of their state WQS
stream bottom deposits narrative standard (New Mexico Environment Department 2002), which
states:
Surface waters of the State shall be free of water contaminants from other than natural
causes that will settle and damage or impair the normal growth, Junction, or
reproduction of aquatic life or significantly alter the physical or chemical properties of
the bottom.
Unlike Idaho, New Mexico's draft protocol calls for making use attainment decisions based on
both biological and non-biological indicators. The approach is based on reference condition sites.
Specifically, the protocol is a quantitative, three-step assessment procedure for determining
whether the above narrative standard is being attained in a particular stream reach or segment by
(1) comparing changes or differences, if any, between the site of concern and a reference site, (2)
directly evaluating instream habitat by measuring either substrate size (mainly fines, 2 mm or
less) abundance or cobble embeddedness, and (3) verifying or confirming results obtained in step
2 by assessing and comparing benthic macroinvertebrate communities (or fish) at the same sites.
British Columbia, Canada:
Environment Canada has narrative guidelines for deposited bedload sediment, streambed
substrate, suspended sediment, and turbidity for aquatic life uses. The British Columbia (BC)
Ministry of Water, Land and Air Protection released the Ambient Water Quality Guidelines
(Criteria) for Turbidity and Suspended and Benthic Sediments that contain numeric thresholds
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compliant with the national narrative guidelines (Singleton 2001, technical appendices; Caux et
al. 1997a,b).
The BC guidelines are broken down by five water uses (untreated drinking water, treated
drinking water, recreation and aesthetics, aquatic life, and the final catch-all, terrestrial life,
irrigation, and industrial uses), three sediment indicators (turbidity, suspended sediments, and
stream substrate composition), and two flow conditions (clear flow and turbid flow). Numeric
criteria, based on background conditions, exist for each indicator and flow condition for aquatic
life use.
Australia and New Zealand:
The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC
2000) define criteria for visual clarity and aesthetics, and outline an approach for defining trigger
values which, when exceeded, indicate that a problem may be present due to the stressor of
concern. The visual clarity guidelines are based on the objective that to protect visual clarity of
waters used for swimming, the horizontal sighting of a 200mm diameter black disc should
exceed 1.6 m. For protecting the aesthetic quality of recreational waters the natural visual clarity
should not be reduced by more than 20 percent, the natural hue of water should not be changed
by more than 10 points on the Munsell Scale and the natural reflectance of the water should not
be changed by more than 50 percent.
The trigger values approach mirrors the reference condition method using biological or
ecological indicators. The trigger value is defined as the level of key physical or chemical
stressors below which ecologically or biologically meaningful changes do not occur, i.e. the
acceptable level of change. Regarding sediments as pollutants, the guidelines address turbidity
and suspended particulate matter, and the 80th percentile of the reference system distribution is
chosen. Default trigger values are provided for use where either an appropriate reference system
is not available, or the scale of operation makes it difficult to justify the allocation of resources to
collect the necessary information on a reference system.
European Union (EU):
The European Water Framework Directive (WFD) directs the member states to establish goals,
basin plans, and monitoring of ecological quality (The European Parliament and the Council of
the European Union 2000). Assessment of ecological quality is based on a reference condition
method. Annex II of the Directive specifies methods for establishing type-specific reference
conditions for surface waterbody types. Reference conditions may be based on field data,
modeling, or professional judgment. Member states are also directed to collect and maintain
information on the type and magnitude of significant anthropogenic pressures such as urban
development, forestry, and fisheries.
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Table D.I. Suspended and Bedded Sediments (SABS)-Related Criteria for Surface Water Quality by state (U.S. EPA 2001).
State
Numeric
Narrative
(0
(0
jC
<
TURBIDITY:
Public Water Supply: There shall be no turbidity of other than natural origin
that will cause substantial visible contrast with the natural appearance of waters
or interfere with any beneficial uses they serve. Furthermore, in no case shall
turbidity exceed 50 Nephelometric units above background. Background will
be interpreted as the natural condition of the receiving waters, without the
influence of man-made or man-induced causes. Turbidity levels caused by
natural runoff will be included in establishing background levels.
The following uses require the same turbidity criteria as described above:
swimming and other whole body water-contact sports; shellfish harvesting; fish
and wildlife; agricultural and industrial water supply; industrial operations; and
navigation.
(0
JJJ
<
FRESH WATER USES:
Drinking Water Supply and Culinary Food Processing, Contact
Recreation: Nephelometric turbidity units (NTU) may not exceed 5
Nephelometric units above natural conditions when the natural turbidity is 50
NTU or less, and may not have more than 10% increase in turbidity when the
natural turbidity is more than 50, not to exceed a maximum increase of 25
NTU. No measurable increase in concentration of settleable solids above
natural conditions, measured by the volumetric Imhoff cone.
Secondary Contact Recreation: Shall not exceed 5 NTU above natural
conditions when natural turbidity is 50 NTU or less, and not have more than
20% increase in turbidity when the natural condition is more than 50 NTU, not
to exceed a maximum increase of 50 NTU. For all lake waters, shall not exceed
5 NTU over natural conditions.
Aquaculture: May not exceed 25 NTU above natural conditions. For all lake
waters, may not exceed 5 NTU above natural conditions.
Water Supply: aquaculture, industrial: No imposed loads that will
interfere with established water supply treatment levels.
Agriculture: may not cause detrimental effects on indicated use.
In other surface waters: no sediment loads (suspended or
deposited) that may cause adverse effects on aquatic animal or
plant life, their reproduction, or habitat may be present.
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Table D.I. cont
State
Numeric
Narrative
o
JO
<
Growth and Propagation of Fish, Shellfish, and Other Aquatic Life: The
percent accumulation of fine sediment in the range of 0.1 mm to 4.0 mm in the
gravel bed of waters used by anadromous or resident fish for spawning may not
be increased more than 5% by weight above natural conditions (as shown from
grain size accumulation graph). In no case may the 0.1 mm to 4.0 mm fine
sediment range in those gravel beds exceed a maximum of 30% by weight (as
shown from grain size accumulation graph).
Water Supply Agriculture, including Irrigation and Stock Watering: For
sprinkler irrigation, water must be free of particles of 0.074 mm or coarser. For
irrigation or water spreading, may not exceed 200 mg/1 for an extended period
of time.
CO
c
o
N
Designated uses of a surface water may include full body contact, partial body
contact, domestic water source, fish consumption, aquatic and wildlife (cold
water fishery), aquatic and wildlife (warm water fishery), aquatic and wildlife
(ephemeral), aquatic and wildlife (effluent dependent water), agricultural
irrigation, and agricultural livestock watering.
The following water quality standards for turbidity, expressed as a maximum
concentration in Nephelometric Turbidity Units (NTU), shall not be exceeded:
Full body contact and incidental human contact: Not to exceed 50 NTU in
streams, or 25 NTU in lakes.
Aquatic and Wildlife (cold water fishery): Not to exceed 10 NTU in rivers,
streams, other flowing waters, lakes, reservoirs, tanks and ponds.
Aquatic and Wildlife (warm water fishery): Not to exceed 50 NTU in rivers,
streams, and other flowing waters. Not to exceed 25 NTU in lakes, reservoirs,
tanks and ponds.
A surface water shall be free from pollutants in amounts or
combinations that:
1. Settle to form bottom deposits that inhibit or prohibit the
habitation, growth, or propagation of aquatic life or that
impair recreational uses.
2. Cause objectionable odor in the area in which the surface
water is located.
3. Cause off-taste or odor in drinking water.
4. Cause off-flavor in aquatic organisms or waterfowl.
5. Are toxic to humans, animals, plants, or other organisms.
6. Cause the growth of algae or aquatic plants that inhibit or
prohibit the habitation, growth, or propagation of other
aquatic life or that impair recreational uses.
7. Cause or contribute to a violation of an aquifer water
quality standard.
8. Change the color of the surface water from natural
background levels of color.
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Table D.I. cont.
State
Numeric
Narrative
to
CO
CO
1_
<
In establishing these standards, the Commission has taken into consideration
the use and value of the streams for public water supplies, commercial,
industrial and agricultural uses, aesthetics, recreational purposes, propagation
of fish and wildlife, other beneficial uses, and views expressed at public
hearings.
There shall be no distinctly visible increase in turbidity of receiving waters
attributable to municipal, industrial, agricultural, other waste discharges or
instream activities.
Water bodies/Streams Limit (NTU)
Ozark Highlands 10
Boston Mountains 10
Arkansas River Valley 21
Ouachita Mountains 10
Springwater-influenced Gulf Coastal 21
Typical Gulf Coastal 45
Channel-Altered Delta 75
Arkansas River 50
Mississippi River 50
Red River 50
St. Francis River 75
Trout 10
Lakes and Reservoirs 25
Significant physical alterations of the habitat within extraordinary
resource waters, ecologically sensitive waterbodies or natural and
scenic waterways are not allowed.
CO
'E
CO
O
None listed in state regulations.
U.S. EPA provides some (from California Water Quality Standards by River
Basins, Ca. 1975).
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Table D.I. cont.
State
Numeric
Narrative
o
T3
o
O
Provide some numeric standards by major river systems, although no turbidity
or other sediment-related criteria are specified.
The Commission recognizes that excessive salinity and suspended
solids levels can be detrimental to the water use classifications.
The Commission has established salinity standards for the
Colorado River Basin ("Water Quality Standards for Salinity
including Numeric Criteria and Plan of Implementation of Salinity
Control", Commission Regulation No. 39) but has not established
or assigned other standards for salinity or suspended solids control
practices to be developed through 208 plans, coordination with
agricultural agencies, and further studies of existing water quality.
3
o
c
c
o
O
Could not identify any sediment-related criteria for non-point source
(U.S. EPA document lists upper turbidity limits for streams classed)
(0
I
a)
a
For all Fresh Waters: Turbidity shall not exceed natural levels by more than
10 Nephelometric or Formazin Turbidity Units.
For mixing zones, there is a limit of 10 NTU above natural background.
(0
o
Turbidity: Shall not exceed 29 NTUs above natural background conditions.
Biological Integrity: No more than a 75% reduction of benthic macro-
invertebrates using the Shannon-Weaver Index relative to established
background levels measured using organisms retained by a U.S. Standard No.
30 sieve collected and composited from a minimum of three natural mini-
Dendy type artificial substrate samples of 0.1 to 0.15 m2, incubated for 4
weeks.
Transparency: Shall not be reduced by more than 10%.
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Table D.I. cont.
State
Numeric
Narrative
re
s>
o
o>
O
All waters shall be free from turbidity which results in a substantial visual
contrast in a water body due to a man-made activity. The upstream appearance
of a body of water shall be as observed at a point immediately upstream of a
turbidity-causing man-made activity. That upstream appearance shall be
compared to a point which is located sufficiently downstream from the activity
so as to provide an appropriate mixing zone.
All waters shall be free from material related to municipal,
industrial or other discharges which produce turbidity, color, odor
or other objectionable conditions which interfere with legitimate
water uses.
(0
(0
Streams: Not to exceed the given value:
Parameter
Suspended
Solids (mg/L)
Turbidity
(N.T.U)
Geometric Mean
10.0**
5.0*
2.0**
More Than:
10% of the
Time
30.0**
15.0*
5.5**
2% of the Time
55.0**
25.0*
10.0**
*Wet Season- November 1 through April 30
**Dry Season- May 1 through October 31
Bottom criteria for streams:
(A) Episodic deposits of flood-borne soil sediment shall not occur in
quantities exceeding an equivalent thickness of five millimeters (0.20
inch) over hard bottoms twenty-four hours after a heavy rainstorm.
(B) Episodic deposits of flood-borne soil sediment shall not occur in
quantities exceeding an equivalent thickness often millimeters (0.40
inch) over soft bottoms twenty-four hours after a heavy rainstorm.
(C) In soft bottom material in pool sections of streams, oxidation-reduction
potential (EH) in the top ten centimeters (four inches) shall not be less
than+100 millivolts.
(D) In soft bottom material in pool sections of streams, no more than fifty
per cent of the grain size distribution of sediment shall be smaller
than 0.125 millimeter (0.005 inch) in diameter.
All waters shall be free of substances attributable to domestic,
industrial, or other controllable sources of pollutants, including:
(1) Materials that will settle to form objectionable sludge or
bottom deposits.
(2) Floating debris, oil, grease, scum, or other floating
materials.
(3) Substances in amounts sufficient to produce taste in the
water or detectable off-flavor in the flesh offish, or in
amounts sufficient to produce objectionable color,
turbidity or other conditions in the receiving waters.
(4) High or low temperatures; biocides; pathogenic
organisms; toxic, radioactive, corrosive, or other
deleterious substances at levels or in combinations
sufficient to be toxic or harmful to human, animal, plant,
or aquatic life, or in amounts sufficient to interfere with
any beneficial use of the water.
(5) Substances or conditions or combinations thereof in
concentrations which produce undesirable aquatic life.
(6) Soil particles resulting from erosion on land involved in
earthwork, such as the construction of public works;
highways; subdivisions; recreational, commercial, or
industrial developments; or the cultivation and
management of agricultural lands.
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Table D.I. cont.
State
__ __
+j
c
o
o^
'<5
£
(0
I
Numeric
Biological criteria for streams:
The director shall prescribe the appropriate parameters, measures, and criteria
for monitoring stream bottom biological communities including their habitat,
which may be affected by proposed actions. Permanent benchmark stations
may be required where necessary for monitoring purposes. The water quality
criteria for this subsection shall be deemed to be met if time
benchmark stations
series surveys of
indicate no relative changes in the relevant biological
communities, as noted by biological community indicators or by indicator
organisms which may be applicable to the specific site.
Coastal and Marine
Turbidity (NTU) not to exceed the given value:
Location
All Estuaries
Pearl Harbor
Embayments
Open Coastal
Waters
Oceanic Waters
Marine
Geometric Mean
1.5
4.0
0.4
0.5*
0.02**
0.03
0.1
More
10% of the Time
3.0
8.0
1.0
1.25*
0.05**
0.1
Than
2% of the Time
5.0
15.0
1.5
2.0*
1.0**
0.2
* Wet season - November 1 through April 30.
** Dry season - May 1 through October 31.
Marine Bottom Types:
Sand beaches: No more than fifty per cent of the grain size
distribution of
sediment shall be smaller than 0.125 millimeters in diameter.
Lava rock shorelines: Episodic deposits of flood-borne sediment shall not
occur in quantities exceeding an equivalent thickness of five
millimeters (0.20
inch) for longer than twenty -four hours after a heavy rainstorm.
Marine pools and protected coves: No more than fifty per cent of the grain
size distribution of the sediment shall be smaller than 0.125
diameter.
Hard bottoms: No
millimeters in
thicker than an equivalent of five millimeters (0.2 inch).
Soft bottoms: No thicker than an equivalent often millimeters (0.4 inch).
Narrative
The water quality standards (for most subsections) shall be deemed
to be met if time series surveys of benchmark station indicate no
relative changes in the relevant biological communities, as noted
by biological community indicators or by indicator organisms
which may be applicable to the specific site.
Specific criteria to be applied to all reef flats and reef communities:
No action shall be undertaken which would substantially risk
damage, impairment, or alteration of the biological characteristics
of the areas named herein.
"Soft bottom communities" means poorly described and "patchy"
communities, mostly of burrowing organisms, living in deposits at
depths between two to forty meters (approximately six to one
hundred thirty feet). The particle size of sediment, depth below sea
level, and degree of water movement and associated sediment
turnover dictate the composition of animals which rework the
bottom with burrows, trails, tracks, ripples, hummocks, and
depressions.
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Table D.I. cont.
State
Numeric
Narrative
o
o
(0
(0
Reef Flats and Reef Communities:
No more than fifty per cent of the grain size distribution of sand patches shall
be smaller than 0.125 millimeters in diameter; Episodic deposits of flood-
borne soil sediment shall not occur in quantities exceeding equivalent
thicknesses for longer than twenty-four hours after a heavy rainstorm as
follows:
Living coral surfaces: No thicker than an equivalent of two millimeters (0.08
inch).
o
.c
(0
Aquatic Habitat Parameters: These parameters may include, but are not
limited to, stream width, stream depth, stream shade, measurements of
sediment impacts, bank stability, water flows, and other physical characteristics
of the stream that affect habitat for fish, macroinvertebrates or other aquatic
life; and (3-20-97).
Biological Parameters: These parameters may include, but are not limited to,
evaluation of aquatic macroinvertebrates including Ephemeroptera, Plecoptera
and Trichoptera (EPT), Hilsenhoff Biotic Index, measures of functional feeding
groups, and the variety and number offish or other aquatic life to determine
biological community diversity and functionality.
In determining whether a water body fully supports designated and
existing beneficial uses, the Department shall determine whether
all of the applicable water quality standards are being achieved,
including any criteria developed pursuant to these rules, and
whether a healthy, balanced biological community is present. The
Department shall utilize biological and aquatic habitat parameters
listed below and in the current version of the "Water Body
Assessment Guidance", as published by the Idaho Department of
Environmental Quality, as a guide to assist in the assessment of
beneficial use status. These parameters are not to be considered or
treated as individual water quality criteria or otherwise interpreted
or applied as water quality standards.
c
Soil Loss: Effective January 1, 1994 to January 1, 2000, all land greater than
5% slope subject to this program shall be considered in compliance with the
state program if the long term annual soil losses are kept at or below one and
one-half "T" value. Effective January 1, 2000, and thereafter, all land subject to
the Act shall meet "T" value. The soil loss tolerance as established by the Soil
Conservation Service and as published in the Soil Conservation Service
Technical Guide (United States Department of Agriculture, Soil Conservation
Service, Field Offices in Illinois) are adopted as the official "T" values for soils
of Illinois.
Studies have not yet been able to accurately determine what part of
the stream sediment load is attributable to stream bank erosion and
what part comes from non-point sources of erosion. While the
Department will encourage all conservation measures and practices
to minimize stream bank erosion, more research needs to be done
before the feasibility of and the responsibility for controlling
stream bank erosion can be determined.
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Table D.I. cont.
State
Numeric
Narrative
No sediment-related criteria identified.
(0
c
(0
(1) All waters at all times and at all places, including the mixing
zone, shall meet the minimum conditions of being free from
substances, materials, floating debris, oil, or scum attributable to
municipal, industrial, agricultural, and other land use practices, or
other discharges that:
(A) Will settle to form putrescent or otherwise objectionable
deposits.
(B) Are in amounts sufficient to be unsightly or deleterious.
(C) Produce color, visible oil sheen, odor, or other conditions in
such degree as to create a nuisance.
(D) Are in amounts sufficient to be acutely toxic to, or to
otherwise severely injure or kill aquatic life, other animals,
plants, or humans.
(0
o
Criteria applicable to all surface waters including general use and designated
use waters, at all places and at all times to protect livestock and wildlife
watering, aquatic life, noncontact recreation, crop irrigation, and industrial,
domestic, agricultural and other incidental water withdrawal uses not protected
by the specific numerical criteria.
Turbidity: The turbidity of the receiving water shall not be increased by more
than 25 Nephelometric Turbidity Units (N.T.U.) by any point source discharge.
Physical and biological integrity: The waters designated as high-
quality resource waters will receive protection of existing uses
through maintaining water quality levels necessary to fully protect
existing uses or improve water quality to levels necessary to meet
the designated use criterion. This involves the protection of such
features of the water body as channel alignment, bed
characteristics, water velocity, aquatic habitat, and the type,
distribution and abundance of existing aquatic species.
(0
(/)
c
(0
Surface waters shall be free, at all times, from the harmful effects
of substances that originate from artificial sources of pollution and
that produce any public health hazard, nuisance condition, or
impairment of a designated use.
Suspended solids added to surface waters by artificial sources shall
not interfere with the behavior, reproduction, physical habitat, or
other factors related to the survival and propagation of aquatic or
semi-aquatic life or terrestrial wildlife.
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o
AQUATIC LIFE:
Warm water aquatic habitat: The following parameters and associated
criteria shall apply for the protection of productive warm water aquatic
communities, fowl, animal wildlife, arboreous growth, agricultural, and
industrial uses:
Total suspended solids: Total suspended solids shall not be changed to the
extent that the indigenous aquatic community is adversely affected.
Settleable solids: The addition of settleable solids that may alter the stream
bottom so as to adversely affect productive aquatic communities is prohibited.
Surface waters shall not be aesthetically or otherwise degraded by
substances that:
(a) Settle to form objectionable deposits.
(b) Float as debris, scum, oil, or other matter to form a
nuisance.
(c) Produce objectionable color, odor, taste, or turbidity.
(d) Injure, are chronically or acutely toxic to or produce adverse
physiological or behavioral responses in humans, animals,
fish and other aquatic life.
(e) Produce undesirable aquatic life or result in the dominance
of nuisance species.
(f) Cause fish flesh tainting. The concentration of all phenolic
compounds which cause fish flesh tainting shall not exceed
five (5) |ig/L as an instream value.
(0
c
(0
o
Turbidity other than that of natural origin shall not cause substantial visual
contrast with the natural appearance of the waters of the state or impair any
designated water use. Turbidity shall not significantly exceed background;
background is defined as the natural condition of the water. Determination of
background will be on a case-by-case basis.
As a guideline, maximum turbidity levels, expressed as Nephelometric
Turbidity Units (NTU), are established and shall apply for the following named
waterbodies and major aquatic habitat types of the state:
i. Red, Mermentau, Atchafalaya, Mississippi, and Vermilion Rivers and Bayou
Teche-150 NTU; ii. estuarine lakes, bays, bayous, and canals-50 NTU; iii.
Amite, Pearl, Ouachita, Sabine, Calcasieu, Tangipahoa, Tickfaw, and
Tchefuncte Rivers—50 NTU; iv. freshwater lakes, reservoirs, and oxbows-25
NTU; v. designated scenic streams and outstanding natural resource waters not
specifically listed in Subsection B.9.b.i-iv of this Section—25 NTU; and vi.
other state waters and waterbody segments where natural background turbidity
exceeds the values specified in these clauses, turbidity in NTU caused by any
discharges shall be restricted to the appropriate background value plus 10
percent. This shall not apply to designated intermittent streams.
All waters shall be free from such concentrations of substances
attributable to wastewater or other discharges sufficient to:
a. Settle to form objectionable deposits.
b. Float as debris, scum, oil, or other matter to form
nuisances or to negatively impact the aesthetics.
c. Result in objectionable color, odor, taste, or turbidity.
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State
Numeric
Narrative
c
o
(0
c
(0
o
Biological and Aquatic Community Integrity: The biological and community
structure and function in state waters shall be maintained, protected, and
restored except where not attainable and feasible as defined in LAC
33:IX.1109.B.3. This is the ideal condition of the aquatic community inhabiting
the unimpaired water bodies of a specified habitat and region as measured by
community structure and function. The biological integrity will be guided by
the fish and wildlife propagation use designated for that particular water body.
Fish and wildlife propagation uses are defined in LAC 33:IX.1111.C. The
condition of these aquatic communities shall be determined from the measures
of physical, chemical, and biological characteristics of each surface water body
type, according to its designated use (LAC 33 :IX. 1123). Reference site
conditions will represent naturally attainable conditions. These sites should be
the least impacted and most representative of water body types.
Such reference sites or segments of water bodies shall be those observed to
support the greatest variety and abundance of aquatic life in the region as is
expected to be or has been recorded during past surveys in natural settings
essentially undisturbed by human impacts, development, or discharges. This
condition shall be determined by consistent sampling and reliable measures of
selected, indicative communities of animals and/or invertebrates as established
by the department and may be used in conjunction with acceptable chemical,
physical, and microbial water quality measurements and records as deemed for
this purpose.
No sediment-related criteria identified.
(0
Turbidity (All streams):
Turbidity in the surface water resulting from any discharge may not exceed 150
units at any time or 50 units as a monthly average. Units shall be measured in
NTU.
Turbidity may not exceed level detrimental to aquatic life.
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State
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Narrative
to
ts
a)
to
3
-C
o
(0
(0
(0
(0
Water Body Classification
Class A - These waters are designated as a source of public water supply.
Class B - These waters are designated as a habitat for fish, other aquatic life,
and wildlife, and for primary and secondary contact recreation.
(c) Class C - These waters are designated as a habitat for fish, other aquatic life
and wildlife, and for secondary contact recreation.
Class SA - These waters are designated as an excellent habitat for fish, other
aquatic life and wildlife and for primary and secondary contact recreation. In
approved areas they shall be suitable for shellfish harvesting without
depuration (Open Shellfish Areas). These waters shall have excellent aesthetic
value.
Class SB - These waters are designated as a habitat for fish, other aquatic life
and wildlife and for primary and secondary contact recreation. In approved
areas they shall be suitable for shellfish harvesting with depuration (Restricted
Shellfish Areas). These waters shall have consistently good aesthetic value.
No sediment-related numeric criteria are specified.
CLASS A, B, C, SA, SB
Solids: These waters shall be free from floating, suspended and
settleable solids in concentrations or combinations that would
impair any use assigned to this class, that would cause aesthetically
objectionable conditions, or that would impair the benthic biota or
degrade the chemical composition of the bottom.
Color and Turbidity: These waters shall be free from color and
turbidity in concentrations or combinations that are aesthetically
objectionable or would impair any use assigned to this class.
c
(0
O)
Uses an effluent limitation system. No numeric criteria were identified.
(0
+J
o
(0
a)
c
c
Turbidity:
Domestic consumption
Class A-5
Class B-5
Class C-24
Fisheries and recreation
Class A-10
Class B-25
Class C-25
Industrial consumption
Class A-5
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Narrative
Q.
Q.
'55
to
'55
to
The turbidity outside the limits of a 750-foot mixing zone shall not exceed the
background turbidity at the time of discharge by more than 50 NTU.
Waters shall be free from materials attributable to municipal,
industrial, agricultural or other discharges producing color, odor,
taste, total suspended solids, or other conditions in such degree as
to create a nuisance, render the waters injurious to public health,
recreation or to aquatic life and wildlife or adversely affect the
palatability of fish, aesthetic quality, or impair the waters for any
designated uses.
3
O
(0
to
Turbidity and Color: Water contaminants shall not cause or
contribute to turbidity or color that will cause substantial visible
contrast with the natural appearance of the stream or lake or
interfere with beneficial uses.
Solids: Water contaminants shall not cause or contribute to solids
in excess of a level that will interfere with beneficial uses. The
stream or lake bottom shall be free of materials which will
adversely alter the composition of the benthos, interfere with the
spawning offish or development of their eggs or adversely change
the physical or chemical nature of the bottom.
Biocriteria: The biological integrity of waters, as measured by
lists or numeric diversity indices of benthic invertebrates, fish,
algae or other appropriate biological indicators, shall not be
significantly different from reference waters. Waters shall be
compared with reference waters of similar size within an
ecoregion. Reference water locations are listed in a Table.
(0
c
(0
+J
c
O
Turbidity
B-l Streams: The maximum allowable increase above naturally occurring
turbidity is 5 NTU.
B-2 and B-3 Streams: The maximum allowable increase above naturally
occurring turbidity is 10 NTU.
C-l Streams: The maximum allowable increase above naturally occurring
turbidity is 5 NTU.
C-2 Streams: The maximum allowable increase above naturally occurring
turbidity is 10 NTU.
Bl B2 B-3 C-l C-2 water bodies
No increases are allowed above naturally occurring concentrations
of sediment, settleable solids, oils, or floating solids, which will or
are likely to create a nuisance or render the waters harmful,
detrimental, or injurious to public health, recreation, safety,
welfare, livestock, wild animals, birds, fish, or other wildlife.
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^
to
(0
No sediment-related criteria identified.
(0
T3
(0
a)
Class A waters include waters or portions of waters located in areas of little
human habitation, no industrial development or intensive agriculture and where
the watershed is relatively undisturbed by man's activity:
Settleable solids: Only amounts attributable to man's activities which will not
make the waters unsafe or unsuitable as a drinking water source or which will
not be detrimental to aquatic life or for any other beneficial use established for
this class.
Specific turbidity (NTU) and suspended solids (mg/1) values are given for
specific rivers in the state.
Aquatic life: The water must be suitable as a habitat for fish and other aquatic
life existing in a body of water. This does not preclude the reestablishment of
other fish or aquatic life.
For some waters (not all), turbidity is included in the following
statement:
Waters must be free from high temperature, biocides, organisms
pathogenic to human beings, toxic, corrosive or other deleterious
substances attributable to domestic or industrial waste or other
controllable sources at levels or combinations sufficient to be toxic
to human, animal, plant or aquatic life or in amounts sufficient to
interfere with any beneficial use of the water. Compliance with the
provisions of this subsection may be determined in accordance
with methods of testing prescribed by the department. If used as an
indicator, survival of test organisms must not be significantly less
in test water than in control water.
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Narrative
to
a.
CO
i
a>
Deposits
(a) Class A waters shall contain no benthic deposits, unless naturally
occurring.
(b) Class B waters shall contain no benthic deposits that have a detrimental
impact on the benthic community, unless naturally occurring.
Turbidity
(a) Class A waters shall contain no turbidity, unless naturally occurring.
(b) Class B waters shall not exceed naturally occurring conditioning by
more than 10 NTUs.
(c) Waters identified in RSA 485-A:8, III shall contain no turbidity of
unreasonable kind or quality.
(d) Class C is the same as class B.
Aquatic Life
(a) The surface waters shall support and maintain a balanced, integrated,
and adaptive community of organisms having a species composition,
diversity, and functional organizational comparable to that of similar
natural habitats of a region.
(b) Differences from naturally occurring conditions shall be limited to non-
detrimental differences in community structure and function.
(1) All surface waters shall be free from substances in kind or
quantity that:
a. Settle to form harmful deposits.
b. Float as foam, debris, scum or other visible substances.
c. Produce odor, color, taste or turbidity which is not
naturally occurring and
d. Would render it unsuitable for its designated uses.
e. Result in the dominance of nuisance species, or
f. Interfere with recreational activities.
12
a>
->
a>
SOLIDS, SUSPENDED 25.0 (mg/L)
Turbidity: Fresh waters that are not designated as FWl(those fresh waters, as
designated in N.J.A.C. 7:9B-1.15(h) Table 6, that are to be maintained in their
natural state of quality (set aside for posterity) and not subjected to any man-
made wastewater discharges or increases in runoff from anthropogenic
activities) orPinelands Waters: Maximum 30-day average of 15 NTU, a
maximum of 50 NTU at any time.
Coastal saline waters: Levels shall not exceed 10.0 NTU.
Saline Estuaries: Maximum 30-day average of 10 NTU, a maximum of 30
NTU at any time.
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o
o
'R
a>
Turbidity: Turbidity attributable to other than natural causes shall
not reduce light transmission to the point that the normal growth,
function, or reproduction of aquatic life is impaired or that will
cause substantial visible contrast with the natural appearance of the
water.
Bottom Deposits: Surface waters of the state shall be free of water
contaminants from other than natural causes that will settle and
damage or impair the normal growth, function, or reproduction of
aquatic life or significantly alter the physical or chemical
properties of the bottom.
O
0)
TURBIDITY
Water Body Types AA, A, B, C, D, SA, SB, SC, SD, I: No increase except
from natural sources that will cause a substantial visible contrast to natural
conditions.
In water body type GA, turbidity shall not exceed 5 NTU.
Suspended, Colloidal and Settleable Solids
AA, A, B, C, D, SA, SB, SC, I, SD, A-Special
None from sewage, industrial colloidal and wastes or other wastes
that will cause deposition or impair the waters for their best usages.
(0
_c
1
(0
O
-C
Turbidity: the turbidity in the receiving water shall not exceed:
50 Nephelometric Turbidity Units (NTU) in streams not designated as trout
waters.
10 NTU in streams, lakes or reservoirs designated as trout waters.
25 NTU for lakes and reservoirs not designated as trout waters.
If turbidity exceeds these levels compared to natural background conditions,
the existing turbidity level cannot be increased.
Compliance with this turbidity standard can be met when land management
activities that employ Best Management Practices (BMPs) [as defined by Rule
.0202(6) of this Section] recommended by the Designated Nonpoint Source
Agency [as defined by Rule .0202 of this Section]. BMPs must be in full
compliance with all specifications governing the proper design, installation,
operation and maintenance of such BMPs.
Water Body Classification
Class C: freshwaters protected for secondary recreation, fishing,
and aquatic life including propagation and survival, and wildlife.
All freshwaters shall be classified to protect these uses at a
minimum.
Class B: freshwaters protected for primary recreation which
includes swimming on a frequent or organized basis and all Class
C uses.
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o
(0
c
(0
o
Nonpoint Source and Storm water Pollution Control Criteria For Entire
Watershed
WS-II Waters
(i) Nonpoint Source and Storm water Pollution Control Criteria For Entire
Watershed:
(A) Low Density Option: Development density must be limited to either
no more than one dwelling unit per acre of single family detached residential
development (or 40,000 square foot lot excluding roadway right-of-way) or
12 percent built-upon area for all other residential and non-residential
development in the watershed outside of the critical area; Storm water runoff
from the development shall be transported by vegetated conveyances to the
maximum extent practicable.
(B) High Density Option: If new development exceeds the low density
option requirements as stated in Sub-Item (3)(b)(i)(A) of this Rule, then
engineered storm water controls must be used to control runoff from the first
inch of rainfall; new residential and non-residential development shall not
exceed 30 percent built-upon area.
(C) Land within the watershed shall be deemed compliant with the density
requirements if the following condition is met: The density of all existing
development at the time of reclassification does not exceed the density
requirement when densities are averaged throughout the entire watershed area
at the time of classification.
(D) Cluster development is allowed on a project-by-project basis.
(E) Minimum 100 foot vegetative buffer is required for all new
development activities that exceed the low density option requirements as
specified in Sub-Items (3)(b)(i)(A) and Sub-Item (3)(b)(ii)(A) of this Rule;
otherwise a minimum 30 foot vegetative buffer for development activities is
required along all perennial waters indicated on the most recent versions of
U.S.G.S. 1:24,000 (7.5 minute) scale topographic maps or as determined by
local government studies; nothing in this Section shall stand as a bar to
desirable artificial stream bank or shoreline stabilization.
Class WS: waters protected as water supplies. (There are five sub-
categories depending on degree of development in the watershed.)
The following are supplemental classifications:
(A) Trout waters (Tr): freshwaters protected for natural trout
propagation and survival of stocked trout.
(B) Swamp waters (Sw): waters which have low velocities and
other natural characteristics which are different from
adjacent streams.
(C) Nutrient Sensitive Waters (NSW): waters subject to
growths of microscopic or macroscopic vegetation requiring
limitations on nutrient inputs.
(D) Outstanding Resource Waters (ORW): unique and special
waters of exceptional state or national recreational or
ecological significance that require special protection to
maintain existing uses.
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o
(0
_c
1
(0
O
.c
(F) No new development is allowed in the buffer; water dependent
structures, or other structures such as flag poles, signs and security lights,
which result in only diminimus increases in impervious area and public
projects such as road crossings and greenways may be allowed where no
practicable alternative exists; these activities shall minimize built-upon
surface area, direct runoff away from the surface waters and maximize the
utilization of BMPs.
Other water classes have similar BMP type rules with some of the numbers
changed slightly.
Critical Area Nonpoint Source and Storm water Pollution Control
Criteria: Total dissolved solids not greater than 500 mg/1.
Class I streams: Suspended solids- Thirty milligrams per liter consecutive
thirty-day average.
Class II: none
O
O
Water quality standards are specified as deviation from biotic indices for each
ecoregion. Values of the index are specified in detail by waterbody or
ecoregion [not reproduced here].
(0
o
-C
Classification:
The narrative and numerical criteria in this section are designated to promote
fish and wildlife propagation for the fishery classifications of Habitat Limited
Aquatic Community, Warm Water Aquatic Community, Cool Water Aquatic
Community (Excluding Lake Waters), and Trout Fishery (Put and Take), (c)
Cool Water Aquatic Community subcategory. Cool Water Aquatic Community
means a subcategory of the beneficial use category "Fish and Wildlife
Propagation" where the water quality, water temperature, and habitat are
adequate to support warm water intolerant climax fish communities and
includes an environment suitable for the full range of cool water benthos.
Typical species may include smallmouth bass, certain darters and stoneflies.
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o
(0
o
-C
Turbidity from other than natural sources shall be restricted to not exceed the
following numerical limits:
Cool Water Aquatic Community/Trout Fisheries: 10 NTU. Lakes: 25 NTU
Other surface waters: 50 NTU.
In waters where background turbidity exceeds these values, turbidity from
point sources shall be restricted to not exceed ambient levels.
Numerical criteria listed above apply only to normal stream flow conditions.
Elevated turbidity levels may be expected during, and for several days after, a
runoff
event.
Biological Criteria
Aquatic life in all waterbodies designated Fish and Wildlife Propagation
(excluding waters designated "Trout, put-and-take") shall not exhibit degraded
conditions as indicated by one or both of the following:
(i) comparative regional reference data from a station of reasonably similar
watershed size or flow, habitat type and Fish and Wildlife beneficial use
subcategory designation or (ii) by comparison with historical data from the
waterbody being evaluated.
c
O
O)
a)
Turbidity (Nephelometric Turbidity Units, NTU): No more than a ten percent
cumulative increase in natural stream turbidities shall be allowed, as measured
relative to a control point immediately upstream of the turbidity causing
activity. However, limited duration activities necessary to address an
emergency or to accommodate essential dredging, construction or other
legitimate activities and which cause the standard to be exceeded may be
authorized provided all practicable turbidity control techniques have been
applied and one of the following has been granted.
The formation of appreciable bottom or sludge deposits or the formation of any
organic or inorganic deposits deleterious to fish or other aquatic life or
injurious to public health, recreation, or industry shall not be allowed [some
modifications to standards for specific rivers].
Notwithstanding the water quality standards contained below, the
highest and best practicable treatment and/or control of wastes,
activities, and flows shall in every case be provided so as to
maintain dissolved oxygen and overall water quality at the highest
possible levels and water temperatures, coliform bacteria
concentrations, dissolved chemical substances, toxic materials,
radioactivity, turbidities, color, odor, and other deleterious factors
at the lowest possible levels.
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State
(0
"o
co
Q
.c
+j
3
O
(/)
Numeric
Biological assessment methods may be employed in appropriate situations to
determine abnormal nutrient enrichment, median tolerance limits (TLm),
concentration of toxic substances, acceptable instream concentrations, or
acceptable effluent concentrations for maintenance of a balanced indigenous
aquatic community.
Put, Grow, and Take (TPGT) are freshwaters suitable for supporting growth of
stocked trout populations and a balanced indigenous aquatic community of
fauna and flora. Suitable also for uses listed in Freshwaters. For this class:
Turbidity: Not to exceed 10% above natural conditions, provided existing uses
are maintained.
Other water classes do not have specific criteria for turbidity.
Narrative
4. All ground waters and surface waters of the state shall at all
times, regardless of flow, be free from:
a. Sewage, industrial waste, or other waste that will settle
to form sludge deposits that are unsightly, putrescent, or
odorous to such degree as to create a nuisance, or
interfere with classified water uses or existing water
uses.
b. Floating debris, oil, grease, scum, and other floating
material attributable to sewage, industrial waste, or other
waste in amounts sufficient to be unsightly to such a
degree as to create a nuisance or interfere with classified
water uses or existing water uses.
c. Sewage, industrial, or other waste which produce taste or
odor or change the existing color or physical, chemical,
or biological conditions in the receiving waters or
aquifers to such a degree as to create a nuisance, or
interfere with classified water uses (except classified
uses within mixing zones as described in this regulation)
or existing water uses.
d. High temperature, toxic, corrosive, or deleterious
substances attributable to sewage, industrial waste, or
other waste in concentrations or combinations which
interfere with classified water.
b. uses (except classified uses within mixing zones as
described in this regulation), existing water uses, or which
are harmful to human, animal, plant or aquatic life.
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^
(0
Q
o
Coldwater permanent fish life propagation waters: Total suspended solids
(TSS) less than 30 mg/L as a 30 day average and 53 mg/L as a daily maximum.
Coldwater semi-permanent fish life propagation waters: TSS less than 90
mg/L as a 30 day average and 158 mg/L as a daily maximum.
Warm water permanent and semi-permanent fish life propagation waters:
TSS less than 90 mg/L as a 30 day average and 158 mg/L as a daily maximum.
Warm water marginal fish life propagation waters: TSS less than 150 mg/L
as a 30 day average and 263 mg/L as a daily maximum.
Effluent Criteria: Effluents discharged from water pollution control facilities
into waters classified for the beneficial use of coldwater permanent fish life
propagation and coldwater marginal fish life propagation must be of high
quality. In order to protect these uses, the effluent may not exceed 10 mg/L of
suspended solids and 10 mg/L of 5-day biochemical oxygen demand.
Raw or treated sewage, garbage, rubble, unpermitted fill materials,
municipal wastes, industrial wastes, or agricultural wastes which
produce floating solids, scum, oil slicks, material discoloration,
visible gassing, sludge deposits, sediments, slimes, algal blooms,
fungus growths, or other offensive effects may not be discharged
or caused to be discharged into surface waters of the state.
All waters of the state must be free from substances, whether
attributable to human-induced point source discharges or nonpoint
source activities, in concentrations or combinations which will
adversely impact the structure and function of indigenous or
intentionally introduced aquatic communities.
0)
0)
c
c
Turbidity or Color - There shall be no turbidity or color in amounts or
characteristics that cannot be reduced to acceptable concentrations by
conventional water treatment processes.
For all beneficial uses:
Solids, Floating Materials and Deposits - There shall be no
distinctly visible solids, scum, foam, oily slick, or the formation of
slimes, bottom deposits or sludge banks of such size or character as
may impair the usefulness of the water as a source of domestic
water supply.
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State
Numeric
Narrative
to
CO
X
Five subcategories of aquatic life use are established. They include limited,
intermediate, high, and exceptional aquatic life and oyster waters.
No specific criteria for a sediment-related number.
Surface water shall be essentially free of floating debris and
suspended solids that are conducive to producing adverse
responses in aquatic organisms or putrescible sludge deposits or
sediment layers which adversely affect benthic biota or any lawful
uses.
Surface waters shall be essentially free of settleable solids
conducive to changes in flow characteristics of stream channels or
the untimely filling of surface water in the state. Waste discharges
shall not cause substantial and persistent changes from ambient
conditions of turbidity or color. Waste discharges shall not cause
substantial and persistent changes from ambient conditions of
turbidity or color.
Aquatic life uses. Vegetative and physical components of the
aquatic environment will be maintained or mitigated to protect
aquatic life uses.
Turbidity Increase: 10 NTU for coldwater and warm water game fish and
other cold water aquatic life, including the necessary aquatic organisms in their
food chain: 15 NTU for non-game fish and waterfowl, shore birds and other
water-oriented wildlife.
Total Suspended Solids: 35 mg/L for coldwater game fish and other cold
water aquatic life, including the necessary aquatic organisms in their food
chain; 90 mg/L for warm water game and non-game fish.
It shall be unlawful, and a violation of these regulations, for any
person to discharge or place any waste or other substance in such a
way as will be or may become offensive such as unnatural
deposits, floating debris, oil, scum or other nuisances such as color,
odor or taste; or cause conditions which produce undesirable
aquatic life or which produce objectionable tastes in edible aquatic
organisms; or result in concentrations or combinations of
substances which produce undesirable physiological responses in
desirable resident fish, or other desirable aquatic life, or
undesirable human health effects, as determined by bioassay or
other tests performed in accordance with standard procedures.
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Narrative
o
The following water quality criteria shall be achieved in all Class A(l)
ecological waters.
Turbidity - Not to exceed 10 NTU (Nepholometric Turbidity Units).
Aquatic Biota, Wildlife, and Aquatic Habitat - Change from the natural
condition is limited to minimal impacts from human activity. Measures of
biological integrity for aquatic macroinvertebrates and fish assemblages are
within the range of the natural condition. Uses related to either the physical,
chemical, or biological integrity of the aquatic habitat or the composition or life
cycle functions of aquatic biota or wildlife are fully supported. All life cycle
functions, including over wintering and reproductive requirements are
maintained and protected.
Water Quality Criteria for Class B waters for Turbidity - The following
criteria shall be achieved:
a. In Cold Water Fish Habitat waters - Not to exceed 10 NTU.
b. In Warm Water Fish Habitat waters - Not to exceed 25 NTU.
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.
Aquatic Biota, Wildlife and Aquatic Habitat - No change from the reference
condition that would prevent the full support of aquatic biota, wildlife, or
aquatic habitat uses. Biological integrity is maintained and all expected
functional groups are present in a high quality habitat. All life-cycle functions,
including over wintering and reproductive requirements are maintained and
protected. In addition, the following criteria shall be achieved:
Water Management Type One waters - change from the reference condition for
aquatic macroinvertebrate and fish assemblages shall be limited to minor
changes in the relative proportions of taxonomic and functional components;
relative proportions of tolerant and intolerant components are within the range
of the reference condition. Changes in the aquatic habitat shall be limited to
minimal differences from the reference condition consistent with the full
support of all aquatic biota and wildlife uses.
Settleable solids, floating solids, oil, grease, scum, or total
suspended solids: None in such concentrations or combinations
that would prevent the full support of uses.
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. These numeric
biological indices shall be derived from measures of the biological
integrity of the reference condition for different water body types.
In establishing numeric biological indices, the Secretary shall
establish procedures that employ standard sampling and analytical
methods to characterize the biological integrity of the appropriate
reference condition. Characteristic measures of biological integrity
include but are not limited to community level measurements such
as: species richness, diversity, relative abundance of tolerant and
intolerant species, density, and functional composition.
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U.S. EPA
Table D.I. cont.
State
Numeric
Narrative
c
o
c
o
Water Management Type Two waters - change from the reference condition for
aquatic macroinvertebrate and fish assemblages shall be limited to moderate
changes in the relative proportions of tolerant, intolerant, taxonomic, and
functional components. Changes in the aquatic habitat shall be limited to minor
differences from the reference condition consistent with the full support of all
aquatic biota and wildlife uses.
Water Management Type Three waters - change from the reference condition
for aquatic macroinvertebrate and fish assemblages shall be limited to moderate
changes in the relative proportions of tolerant, intolerant, taxonomic, and
functional components. Changes in the aquatic habitat shall be limited to
moderate differences from the reference condition consistent with the full
support of all aquatic biota and wildlife uses. When such habitat changes are a
result of hydrological modification or water level fluctuation, compliance may
be determined on the basis of aquatic habitat studies.
(0
'E
None identified for standards.
Turbidity and suspended solid criteria provided as effluent limits on specific
water bodies.
All state waters, including wetlands, shall be free from substances
attributable to sewage, industrial waste, or other waste in
concentrations, amounts, or combinations which contravene
established standards or interfere directly or indirectly with
designated uses of such water or which are inimical or harmful to
human, animal, plant, or aquatic life.
Specific substances to be controlled include, but are not limited to:
floating debris, oil, scum, and other floating materials; toxic
substances (including those which bioaccumulate); substances that
produce color, tastes, turbidity, odors, or settle to form sludge
deposits; and substances which nourish undesirable or nuisance
aquatic plant life. Effluents which tend to raise the temperature of
the receiving water will also be controlled.
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Table D.I. cont.
State
Numeric
Narrative
c
o
+J
O)
c
i
Class AA (Extraordinary), Class A (Excellent):
Turbidity shall not exceed 5 NTU over background turbidity when the
background turbidity is 50 NTU or less, or have more than a 10 percent
increase in turbidity when the background turbidity is more than 50 NTU.
Class B (Good) and C (Fair)
Turbidity shall not exceed 10 NTU over background turbidity when the
background turbidity is 50 NTU or less, or have more than a 20 percent
increase in turbidity when the background turbidity is more than 50 NTU.
Lake Class: Turbidity shall not exceed 5 NTU over background conditions.
CO
'E
2
Categories A, B, and C:
No point or non-point source to West Virginia's waters shall contribute a net
load of suspended matter such that the turbidity exceeds 10 NTU's over
background turbidity when the background is 50 NTU or less, or have more
than a 10% increase in turbidity (plus 10 NTU minimum) when the background
turbidity is more than 50 NTUs. This limitation shall apply to all earth
disturbance activities and shall be determined by measuring stream quality
directly above and below the area where drainage from such activity enters the
affected stream. Any earth disturbing activity continuously or intermittently
carried on by the same or associated persons on the same stream or tributary
segment shall be allowed a single net loading increase.
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Table D.I. cont.
State
Numeric
Narrative
c
'55
c
o
o
Practices attributable to municipal, industrial, commercial,
domestic, agricultural, land development or other activities shall be
controlled so that all waters including the mixing zone and the
effluent channel meet the following conditions at all times and
under all flow conditions:
(a) Substances that will cause objectionable deposits on the shore
or in the bed of a body of water shall not be present in such
amounts as to interfere with public rights in waters of the state.
(b) Floating or submerged debris, oil, scum or other material shall
not be present in such amounts as to interfere with public
rights in waters of the state.
(c) Materials producing color, odor, taste or unsightliness shall
not be present in such amounts as to interfere with public
rights in waters of the state.
(d) Substances in concentrations or combinations which are toxic
or harmful to humans shall not be present in amounts found to
be of public health significance, nor shall substances be
present in amounts which are acutely harmful to animal, plant
or aquatic life.
O)
_c
o
$
(a) In all Class 1 and 2 waters which are cold-water fisheries, the discharge
of substances attributable to or influenced by the activities of man shall
not be present in quantities which would result in a turbidity increase of
more than 10 Nephelometric Turbidity Units (NTUs).
(b) In all Class 3 waters and in Class 1 and 2 waters which are warm-water
fisheries, the discharge of substances attributable to or influenced by the
activities of man shall not be present in quantities which would result in
a turbidity increase of more than 15 NTUs.
In all Wyoming surface waters, substances attributable to or
influenced by the activities of man that will settle to form sludge,
bank or bottom deposits shall not be present in quantities which
could result in significant aesthetic degradation, significant
degradation of habitat for aquatic life or adversely affect public
water supplies, agricultural or industrial water use, plant life or
wildlife.
In all Wyoming surface waters, floating and suspended solids
attributable to or influenced by the activities of man shall not be
present in quantities which could result in significant aesthetic
degradation, significant degradation of habitat for aquatic life, or
adversely affect public water supplies, agricultural or industrial
water use, plant life or wildlife.
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Table D.I. cont.
State
Numeric
Narrative
re
!5
_3
O
O
"S
+j
O
No turbidity increase over 20 NTU for waterbody classes A, B, and C.
The surface waters of the District shall be free from substances
attributable to point or nonpoint sources discharged in amounts that
do any one of the following:
(a) Settle to form objectionable deposits.
(b) Float as debris, scum, oil or other matter to form nuisances.
(c) Produce objectionable odor, color, taste or turbidity.
(d) Cause injury to, are toxic to or produce adverse
physiological or behavioral changes in humans, plants or
animals.
(e) Produce undesirable aquatic life or result in the dominance
of nuisance species.
(f) Impair the biological community which naturally occurs in
the waters or depends on the waters for their survival and
propagation.
O
O
(2
o
r
o>
3
a.
Coastal waters and estuarine waters of high quality and/or exceptional
ecological or
recreational value whose existing characteristics shall not be altered, except by
natural causes, in order to preserve the existing natural phenomena.
Coastal waters and estuarine waters intended for use in primary and secondary
contact recreation, and for propagation and preservation of desirable species
Turbidity shall not exceed 10 NTU, except by natural causes.
Surface waters intended for use as a raw source of public water supply,
propagation and preservation of desirable species as well as primary and
secondary contact recreation: Turbidity shall not exceed 50 (NTU, except when
due to natural phenomena.
The waters of Puerto Rico shall not contain floating debris, scum
and other floating materials attributable to discharges in amounts
sufficient to be unsightly or deleterious to the existing or
designated uses of the waterbody.
The waters of Puerto Rico shall be free from color, odor, taste and
turbidity attributable to discharges in such a degree as to create a
nuisance to the enjoyment of the existing or designated uses of the
waterbody.
. T3
O) C
None
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Appendix E
Summary of the October 2,2003
Consultation with the Science Advisory Board
The Ecological Processes and Effects Committee (EPEC) of the Science Advisory Board met
October 2, 2003 in an informal consultation to review and discuss potential approaches to
developing water quality criteria for suspended and bedded sediments as described in a
discussion paper prepared and presented by U.S. EPA staff. The following summary includes
additional information that was not detailed in Section ID of the Framework. This summary
does not represent Committee consensus or majority opinions since votes were not taken and no
attempt was made to reach consensus under the consultation process.
EPEC Science Advisory Board Members
Chair: Dr. Virginia Dale
Panel Members: Dr. Gregory Biddinger
Dr. Ivan Fernandez
Dr. Cynthia Gilmour
Dr. Charles Hawkins
Dr. Lawrence Master
Dr. Judy Meyer
Dr. Michael Newman
Dr. Charles Pettinger
Consultants: Dr. Brian Bledsoe
Mr. Charles Rabeni
Mr. Timothy Thompson
SAB Staff: Dr. L. Joseph Bachman
Dr. Vanessa Vu
Need to Focus on Both Flowing Waters as Well as Slow Waters
A couple of Committee members indicated that the focus of the U.S. EPA discussion
paper and the U.S. EPA staff presentations was primarily on running water habitats.
Some of the Committee members wanted to emphasize that slow or still water habitats
(large rivers, lakes, estuaries, and oceans) were as important. Members suggested that
Idaho, California, Washington, and British Columbia have criteria/guidelines that would
be a good starting point for developing criteria for running water habitats. The
Chesapeake Bay methods may be a good starting point for large rivers and estuaries,
especially where water column conditions are less variable in space and time.
Some members of the Committee felt that because the two types of habitats are so
different (running water and slow or still water), there may be a need to stratify using this
division, use different biological endpoints in the two types, and develop different
criteria. Some members suggested that bedded sediment criteria may be more appropriate
for running water habitats and suspended measures would be more appropriate for slow
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or still water habitats. Pelagic target organisms may be important in slow water habitats,
whereas benthic organisms may be critical in running waters.
Too Little Sediment is a Problem
The focus of the discussion was on excess sediments, but some members of the
Committee also pointed out that lack of sediments is sometimes a problem in regulated
rivers and in bedrock channels. There was feedback that both extremes of sediment
conditions should and could be addressed using some of the methods under discussion.
Appropriate Focus of Criteria
There were different opinions voiced regarding the starting point of any assessment or
criteria. Some thought that the criterion should reflect a water body's ecological potential
given the intended use of the water body, focusing on the question of "How should we
manage given what's here?" as opposed to "How does this compare to reference
condition?" This would preclude any stratification based on natural waterbody types,
using the intended use as the stratifying factor. This would also simplify the modeling
processes; the endpoints would be selected to work within management models, and there
would be no need to define reference conditions (which are sometimes difficult to
identify).
An opposing view was that reference condition is important to define, even if it is not
attainable. Society should know what it is giving up in terms of natural waterbodies.
When reference conditions are not attainable or can not be identified, then the natural
conditions can be estimated and a Use Attainability Analysis can be performed. It was
also suggested that designated uses of a waterbody may overlap and be in conflict with
each other. Also, the intent is to protect aquatic life; by focusing only on designated uses,
some systems may be written off as not being biologically valuable.
Reference conditions were differentiated from background conditions, as being natural
conditions found in unimpacted settings similar to the assessed water body, whereas
background conditions are detected upstream of a suspected inducement of sediment
pollution. Some Committee members were concerned about finding sufficient reference
conditions, especially for large rivers. Expectations for reference conditions should not be
set using estimates of pre-colonial conditions. It was not clear that any Committee
member was advocating the use of background conditions.
Build In Uncertainty in Methods/Approaches
Some Committee members stated more than once that uncertainty is an important
component of any assessment and it should be inherent to any methods developed for
setting or applying sediment criteria. Criteria could be set while recognizing and
accounting for uncertainty before triggering management action. The Conditional
Probability was attractive because it is inherently based on uncertainty. Variability also
needs to be addressed in terms of flow because suspended sediment measures are
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associated with flow conditions. The time when a measurement is taken may be as
important as how it is taken; base flow may be best for comparison with biological
conditions.
Work Towards National Consistency
The Committee discussed maintaining consistency of sediment assessments among states.
Obvious differences in sediment assessments across state borders should be eliminated.
How this is to be done was not spelled out though coordination at the watershed or
regional level was implied. The State-by-State Reference Condition Method implies that
each state would be autonomous in setting criteria and that the state border issue could be
a problem unless the U.S. EPA has some hand in maintaining consistency.
Reaction to the Staffs Criteria Development Methods
Pros and cons of each criteria development approach were discussed by the Committee first in
isolation, then as a synthesis of methods. The Committee concluded that there was no one single
method that could do everything, but features of each one were valuable and should be combined
into a synthesized framework.
Toxicological Method
The first method discussed was the Toxicological Method. It was thought to be very
different from the other method with some merits and some detractions. One advantage is
that it can identify thresholds for specific species. Also, the laboratory experiments may
help define the nature of the response curve for single species and provide a basis for
dose-response experiments in the field. Some Committee members thought that the
Toxicological Method could complement another method, at least as an additional line of
evidence, but that it was not a valid stand-alone method primarily because impacts are
context dependent and are not reproducible in the laboratory.
A concern that came up in relation to the toxicological method, but that is of general
concern regardless of method, is that the endpoint of the experiments must be translatable
into loads for management purposes. Managers may typically model in terms of turbidity
or TSS and they are not accustomed to using LDso concentrations, other explicitly
toxicological measures, or other measures associated with other methods. For
management purposes, the criteria must be in units that can be modeled. Other
Committee members commented that methods must be "doable," that is, able to be
implemented.
Conditional Probability Analysis (CPA) Method
The CPA method was attractive to some Committee members because it inherently
includes statements of uncertainty (variability) and because it could lead to powerful
causal analysis. When the question came up about whether this method is essentially
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single factor ecology, it was suggested that multiple conditions could be used in the
models, but that it would be data intensive to do so.
Relative Bed Stability (RBS) Method
The RBS method was viewed as best for use in running water habitats and seemed, to
some Committee members, as difficult to use in fine bedded systems such as large rivers.
In large rivers, sediment analysis may require sieving techniques and assessment of
stream power as opposed to stream competence. The limited applicability in slow or still
waters was a detractor for the method. On the positive side, some members said the
method showed promise if it used a classification scheme that truly adjusts expectations
for natural erosional inputs. The comparison of observed conditions to expected
conditions automatically puts the RBS value on a relative scale, which could be
standardized across state lines and would be easier to interpret than a table of different
criteria for different water body classes. There was considerable technical discussion
regarding this method.
One concern expressed by some members with the method was that the biological
response to the RBS parameter did not seem to be linear; responses were only obvious
with the very worst conditions. This was explained as evidence of a possible threshold.
Members suggested that any method needs to show a strong link between the
measurement and biological conditions.
Reference Condition Method
Many Committee members seemed to express that the Reference Condition Method was
a good method but not a stand-alone approach. It was noted that many states have already
invested in this method during biological assessments, and additional costs for
developing sediment criteria would, therefore, be marginal. There was some concern
about using single number thresholds, and some solutions included using
observed/expected ratios, using sediment rating curves to incorporate variable flow
conditions, and the Conditional Probability Analysis as part of the Reference Condition
Method.
Fluvial Geomorphological Method
Some Committee members considered the Fluvial Geomorphological Method a good
screening level method because sediment budgeting already uses such a method.
Committee members noted that natural sediment regimes characteristic of particular
stream types show some consistency, and channel evolution theory explains the changes
of unstable channels in ways that may help clarify thresholds of impairment and aid
efforts to restore impaired streams. Sediment Rating Curves were recognized as
potentially useful but not sufficiently developed, and they are difficult to apply. Some
committee members called channel type classification useful to some degree but advised
that U.S. EPA be aware of and consider the different schools of thought about classifying
based on different channel parameters.
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The Committee indicated that the Fluvial Geomorphological Method focused on the
sediment sources and exposure without considering biotic effects which were considered
essential for criteria development. Despite this point, one member did state that abiotic,
in-channel measurements would be useful as a component of ecological condition. Some
members viewed Hydrogeomorphic classification as a good method for stratification after
identifying impairment and before assessment and diagnosis.
Synthesis of Methods
Some members proposed a synthesis of methods that would take advantage of the
strengths of several methods. The Reference Condition and Conditional Probability
Approach methods were suggested as central to a framework that could be supported
with elements from all of the other methods. In terms of the process that was presented
by staff in the briefing materials, it was suggested that selection of indicators might not
be the first step, but should come later. The Committee considered this a work in progress
and suggested continued work on the synthesis of methods using real data.
Key Feedback by the Committee on the Methods:
• A synthesis of the methods for setting sediment criteria would be optimal.
• The Toxicological Method would be best used to support other methods, but should not
be pursued as a primary method.
• The CPA Method has merit because it inherently included measures of uncertainty.
• The RBS Method has merit in running water systems.
• The Reference Condition Method has merit and could be used as the core or backbone of
a synthesized process.
• The Fluvial Geomorphological Method would be best used for classification or
diagnosis/causal assessment but not for effects assessment because it is not closely
related to biological integrity.
Key Differences of Opinion
The Committee was divided on the definition and use of reference conditions. Some
advocated description of reference conditions and classification by natural types,
estimating reference conditions in cases where appropriate unimpaired systems could not
be identified and sampled. Other members suggested that management objectives (water
body function and designated uses) should be the primary classification scheme,
especially for systems with no pristine reference examples (e.g., large rivers).
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Appendix F
Conceptual Models of SABS Sources and Effects
The following conceptual model depicts relationships from sources of increased erosion of
sediments from terrestrial environments to their effects on benthic invertebrates. The model can
be viewed as three subunits (1) Increased suspended sediment supply through various
mechanisms to their effect on the biota, (2) Increased deposited sediments and their effects on
biota, and (3) Terrestrial environments to increased transport of sediment. Both suspended and
deposited sediment can affect aquatic biota, and these effects have been examined in numerous
review documents (e.g., Waters 1995; Wood and Armitage 1997). Models were prepared by
Kate Schoffield, U.S. EPA, NCEA.
147
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KEY
source ] additional step in
causal pathway
proximate
stress or
t suspended sediment
t deposited sediment
I light in
water column
t filter
clogging
t physical abrasion
by sediment
biological impairment
S ^\
f I taxa with \
V exposed gills J
Model 1. Suspended sediments.
148
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t suspended sediment
>,
| deposited sediment
i
substrate size
interstitial spaces
substrate
diversity
substrate
stability
I interstitial
I interstitial
coverage of fines
*
\ sediment movement
and scouring
t _>
i
1
| biofil
i
±
f I surface A
V gatherers )
Q»
m
\
Mduiidi nuvv
y y V, >
^
t burial 1 — } ^ °
I J IT
<
f dislodgement
>r
scrapers j
i i
f
rganic
latter
1
(\ detritivores J) >
4<
4 DO ^
\ fine substr
habitats
TNH3
N<
C 1 aerophiles ^
f ^~~~~~^___^-^
(^ \, riffle species^)
i
>
i
f
\\ burrowers
r f sprav
\
jrs ^)
biological impairment
Model 2. Deposited sediments.
149
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watershed
de vegetation
( riparian ^|
I de vegetation J
f impoundment
L (upstream)
gravel ^ f point source
mining ) I inputs
impoundment ^
(downstream) J
>
f \
11 sediment 1
content of water con
j ^
f
t sediment
content of water
t water velocity
or discharge
t channel erosion
water velocity
or discharge
t input of fine sediment
Model 3. Sources and processes.
150
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