&EPA
United States
Environmental Protection
Agency
Office of Science and Technology
Washington, DC 20460
EPA-XXX
June 2000
www.epa.gov
Draft Implementation Framework
for the Use of Equilibrium
Partitioning Sediment Guidelines
Guidance for Using Equilibrium
Partitioning Sediment Guidelines (ESGs)
in Water Quality Programs
i^'Sftv
*$*t^2$ji&S£.-fe>-. . .. -/^fe^fiKnr-
*
-------
DRAFT IMPLEMENTATION FRAMEWORK FOR THE USE OF
EQUILIBRIUM PARTITIONING SEDIMENT GUIDELINES
GUIDANCE FOR USING
EQUILIBRIUM PARTITIONING SEDIMENT GUIDELINES (ESGs)
IN WATER QUALITY PROGRAMS
July 2000
United States Environmental Protection Agency
Office of Water
Office of Science and Technology
401 M Street, SW
Washington, DC 20460
-------
THIS PAGE INTENTIONALLY LEFT BLANK
-------
This document provides guidance for applying equilibrium partitioning sediment guidelines
(ESGs) to States, Tribes, EPA Regions, and other entities with regulatory authority over water
quality programs. It also provides guidance on how EPA intends to exercise its discretion in
various environmental protection programs with respect to application of ESGs. The guidance is
designed to implement national policy on these matters. The document does not, however,
substitute for any statute or regulations; nor is it a regulation itself. Thus, it cannot impose
legally binding requirements on EPA, States, Tribes, other regulatory authorities, or the regulated
community, and may not apply to a particular situation based upon the circumstances. EPA,
State, Tribal, and other decision makers retain the discretion to adopt approaches on a case-by-
case basis that differ from this guidance where appropriate. EPA may change this guidance in
the future.
-------
THIS PAGE INTENTIONALLY LEFT BLANK
-------
TABLE OF CONTENTS
LIST OF ACRONYMS iii
EXECUTIVE SUMMARY ES-1
1. INTRODUCTION 1-1
1.1 PURPOSE 1-1
1.2 NEED FOR SEDIMENT QUALITY PROTECTION 1-2
1.3 BIOLOGICAL TESTING FOR SEDIMENT ASSESSMENT 1-3
1.3.1 Whole Sediment Toxicity Tests (Bioassays) 1-3
1.3.2 Benthic Community Assessments , . 1-4
1.4 EQUILIBRIUM PARTITIONING SEDIMENT GUIDELINES 1-5
1.5 ESG IMPLEMENTATION APPROACH 1-12
2. INCORPORATION OF EQUILIBRIUM PARTITIONING
SEDIMENT GUIDELINES INTO STATE AND TRIBAL WATER
QUALITY STANDARDS PROGRAMS 2-1
2.1 PROTECTING SEDIMENT QUALITY THROUGH STATE AND TRIBAL
WATER QUALITY STANDARDS PROGRAMS 2-1
2.1.1 Relationship of Sediment Quality to Designated Uses 2-2
2.1.2 Development of Water Quality Criteria to Protect Sediment Quality 2-3
2.1.3 Implementation Procedures 2-5
2.1.3.1 Translator Procedures 2-6
2.1.3.2 Mixing Zone Policies 2-12
3. DEVELOPMENT OF TOTAL MAXIMUM
DAILY LOADS (TMDLs) FOR SEDIMENT QUALITY PROTECTION ......... 3-1
3.1 INTRODUCTION 3-1
3.1.1 Basis for Listing Water Bodies as Water Quality-Limited
due to Sediment Toxicity 3-2
3.1.2 Identification of Water Quality Indicators and Target Values 3-3
3.1.3 Sediment Quality Modeling 3-3
3.1.4 Follow-up Monitoring 3-5
-------
4. WATER QUALITY-BASED NATIONAL POLLUTANT DISCHARGE
ELIMINATION SYSTEM (NPDES) PERMIT CONDITIONS FOR SEDIMENT
PROTECTION 4-1
4.1 ADDRESSING SEDIMENT CONTAMINATION
THROUGH THE NPDES PROGRAM 4-1
4.1.1 Developing Water Quality-Based Effluent Limits and
Other Requirements for Sediment Quality Protection 4-2
5. APPLICABILITY OF EQUILIBRIUM PARTITIONING
SEDIMENT GUIDELINES IN THE DREDGED MATERIAL
MANAGEMENT PROGRAM 5-1
6. INTEGRATION OF EQUILIBRIUM PARTITIONING SEDIMENT
GUIDELINES WITH THE SUPERFUND PROGRAM 6-1
6.1 INTRODUCTION 6-1
6.2 USING ESGs UNDER CERCLA 6-2
7. INTEGRATION OF EQUILIBRIUM PARTITIONING SEDIMENT
GUIDELINES WITH THE RESOURCE CONSERVATION AJVD
RECOVERY ACT (RCRA) PROGRAM 7-1
7.1 INTRODUCTION 7-1
7.2 USING ESGS UNDER RCRA CORRECTIVE ACTION 7-2
8. REFERENCES 8-1
LIST OF APPENDICES
APPENDIX A. Available Equilibrium Partitioning Sediment Guidelines
APPENDIX B. Sediment Quality Models
-------
LIST OF ACRONYMS
AET Apparent Effects Threshold
AVS Acid Volatile Sulfide
CERCLA Comprehensive Environmental Response, Compensation and Liability Act
CFR Code of Federal Regulations
COPC Contaminant of Potential Concern
CWA Clean Water Act
EFDC Environmental Fluid Dynamics Computer Code
EPA United States Environmental Protection Agency
EqP Equilibrium Partitioning
ERL Effects Range-Low
ERM Effects Range-Median
ESG Equilibrium Partitioning Sediment Guideline
ET Ecotox Threshold
FCV Final Chronic Value
GUI Graphical User Interface
HEM3D Three-Dimensional Hydrodynamic-Eutrophication Model
ITM Inland Testing Manual
K,,,. Organic carbon-interstitial water partition coefficient
Kow Octanol-water partition coefficient
LA Load Allocation
MOS Margin of Safety
MPRSA Marine Protection Research and Sanctuaries Act
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NEPA National Environmental Policy Act
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
NTIS National Technical Information Service
NSI National Sediment Inventory
PAH Polycyclic Aromatic Hydrocarbon
PCB Polychlorinated Biphenyl
PEL Probable Effects Level
RAGS Risk Assessment Guidance for Superfund
RCRA Resource Conservation and Recovery Act
RI/FS Remedial Investigation/Feasibility Study
SAB EPA Science Advisory Board
SCV Secondary Chronic Value
SDZ Sediment Deposition Zone
SEM Simultaneously Extracted Metals
SEMT Simultaneously Extracted concentration of the six (Total) Metals (cadmium,
copper, lead, nickel, silver, and zinc)
SQAL Sediment Quality Advisory Level
SQC Sediment Quality Criteria
-------
TEL Threshold Effects Level
TIE Toxicity Identification Evaluation
TMDL Total Maximum Daily Load
TSDWQ Technical Support Document for Water Quality-Based Toxics Control
USAGE United States Army Corps of Engineers
VIMS Virginia Institute of Marine Science
WASP Water Quality Analysis Simulation Program
WLA Wasteload Allocation
WQC Water Quality Criteria
WQS Water Quality Standards
IV
-------
EXECUTIVE SUMMARY
PURPOSE
This document provides general guidance to States, Tribes,' and others2 for applying the U.S.
Environmental Protection Agency's (EPA's) equilibrium partitioning sediment guidelines
(ESGs) for protection of benthic (sediment-dwelling) organisms. This document also describes
the integral role of other sediment quality assessment tools, such as whole sediment toxicity
tests, in water quality programs. Specifically, this document describes EPA's vision of how
ESGs and complementary tools would be utilized in the following programs:
State and Tribal water quality standards and monitoring programs
Total maximum daily load (TMDL) programs
National Pollutant Discharge Elimination System (NPDES) permitting programs
Dredged material management programs
Superfund programs
Resource Conservation and Recovery Act (RCRA) programs
ESG implementation will vary depending upon applicable regulatory requirements and
programmatic needs.
ESGs are sediment chemical concentrations at or below which direct lethal or sublethal effects
on benthic organisms are not expected. ESGs do not currently address potential food chain
effects of bioaccumulative sediment pollutants. EPA intends to undertake additional work to
develop guidance for assessing bioaccumulative pollutants.
'Throughout this document, "States and Tribes" is intended to include the 50 United States, District of
Columbia, Guam, Virgin Islands, American Samoa, all U.S. Commonwealths and Territories, and Indian Tribes that
EPA determines qualify for treatment as States for purposes of water quality standards (40 CFR 131.3).
is document is also intended for other entities with regulatory authority over water quality programs
(e.g., EPA regional offices and permitting authorities).
ES-1
-------
BACKGROUND
Protecting sediment quality is an important part of restoring and maintaining the biological
integrity of our Nation's waters. Sediment is an integral component of aquatic ecosystems,
providing habitat, feeding, spawning, and rearing areas for many aquatic organisms. Sediment
also serves as a reservoir for contaminants and therefore a source of contaminants to the water
column and organisms. The extent and severity of sediment contamination in the U.S., as
documented in the National Sediment Inventory (U.S. EPA, 1997a) and through contaminated
site histories, emphasize the need for better tools for reducing and preventing sediment
contamination.
Whole sediment toxicity tests (bioassays) are an important tool for sediment quality assessment.
They directly measure sediment toxicity to a test species under laboratory conditions, and are
especially valuable because they account for interactive effects of chemical mixtures. Benthic
community analyses are also useful for sediment assessment, because they account for in-stream
conditions. Numeric sediment quality guidelines are another useful assessment tool, particularly
for identifying individual pollutants causing toxicity. Numeric guidelines can also provide
pollutant-specific targets for restoring and protecting sediment quality.
EPA developed the national equilibrium partitioning sediment guidelines for a broad range of
sediment types. These guidelines, which were developed over a period of several years with
technical review by EPA's Science Advisory Board (SAB), represent sediment chemical
concentrations at or below which it is not expected that there would be direct lethal or sub lethal
effects on benthic organisms.3 EPA recently finalized the methodologies for deriving nationally
applicable ESGs for nonionic organic chemicals and for mixtures of certain metals (cadmium,
copper, lead, nickel, silver, and zinc), and also finalized the methodology for deriving site-
specific ESGs. EPA developed final numeric ESGs for two nonionic organic pesticides (dieldrin
3ESGs do not currently address potential food chain effects of bioaccumulative sediment pollutants. EPA
intends to further evaluate food routes of exposure, bioaccumulation, wildlife, and human health endpoints of
concern.
ES-2
-------
and endrin), and is currently developing an ESG for mixtures of polycyclic aromatic
hydrocarbons (PAHs). EPA calls these guidelines Tier 1 ESGs because they are based on a fiill
minimum aquatic toxicity data set that EPA specifies for development of Clean Water Act
Section 304(a) water quality criteria, and because EPA verified these ESGs using whole
sediment toxicity tests.
In addition, EPA developed Tier 2 ESGs4 for 32 nonionic organic chemicals. EPA derives Tier 2
ESGs in the same way as Tier 1 ESGs, but Tier 2 ESGs can be based on less extensive toxicity
data sets. Additionally, EPA does not require sediment verification tests for Tier 2 ESGs. EPA
recommends that Tier 2 ESGs be implemented in the same manner as Tier 1 ESGs, but with
consideration that there is greater uncertainty associated with Tier 2 values.
EPA based the ESGs on the equilibrium partitioning (EqP) theory, which is a conceptual
approach for predicting the bioavailability of sediment-associated chemicals, and therefore, their
toxicity. The theory assumes that sediment-associated chemicals partition to a state
approximating equilibrium between three phases: the interstitial (pore) water, the binding phases
in sediment which limit bioavailability, and the biota. EPA derived ESGs on the basis of
meeting a protective water-only effects concentration (such as EPA's national recommended
water quality criteria Final Chronic Value (FCV) or Secondary Chronic Value (SCV) for aquatic
life protection) in the interstitial water. For nonionic organic chemicals, EPA expressed ESGs as
the corresponding chemical concentration in sediment, normalized to the fraction of sediment
organic carbon (the primary binding phase for nonionic organics). For metals mixtures, there
were two available guidelines. EPA considered the sediments acceptable for the protection of
benthic organisms if either one of these guidelines was met: 1) the simultaneously extracted
concentration of the six metals (SEMT) is less than or equal to the concentration of acid volatile
sulfide (AVS; the primary binding phase for metals), or 2) the sum of the interstitial water
concentrations for each of the metals divided by their respective FCV is less than or equal to one.
"Tier 2 ESGs were formerly known as Sediment Quality Advisory Levels (SQALs) and were referred to as
SQALs in the National Sediment Inventory (U.S. EPA, 1997a)).
ES-3
-------
The EqP approach to developing benthic toxicity-based sediment guidelines offers advantages
over empirical approaches, which derive guidelines from paired sediment chemical concentration
and biological effects data. The empirical data typically originate from sediments containing a
mixture of contaminants, making it difficult to ascribe the cause of toxicity to a particular
chemical. By contrast, the EqP theory accounts for the bioavailability of chemicals, using
individual chemical data. The EqP theory thus facilitates the identification of causative agents
of toxicity and the establishment of targets for pollutant reduction measures.
However, the EqP theory has limitations which must be recognized when applying ESGs in the
natural environment. Some of these limitations can make ESG values conservative
(overprotective). For example, sediments in the environment may not be near equilibrium, as
assumed by the EqP theory; disequilibrium associated with sediment resuspension would tend to
make ESGs overprotective until near-equilibrium conditions are re-established. Also, additional
partitioning phases (such as pure chemical or soot carbon) may further decrease bioavailability,
thus making ESGs conservatively protective with respect to site-specific bioavailability.5 It
should also be recognized that ESGs do not account for interactive (synergistic or antagonistic)
effects of chemical mixtures, aside from chemical mixtures addressed by specific guidelines
(e.g., cationic metals and PAHs). Additionally, ESGs do not address food chain effects of
bioaccumulative contaminants.
ESG IMPLEMENTATION APPROACH
In consideration of the strengths and limitations of the ESG methodology, EPA does not
recommend that ESGs published concurrently with this draft document be used as numeric
criteria to be adopted by States or Tribes as part of their water quality standards under Section
303(c) of the Clean Water Act. Rather, EPA recommends that the ESGs be used in the following
manner:
3This conservatism can be reduced by developing a site-specific ESG.
ES-4
-------
To help prioritize sites for sediment toxicity or other appropriate testing (as part of State or
Tribal water quality monitoring programs);
To help identify causative pollutants when toxicity is indicated by bioassays or other tools^
To use, as appropriate, in developing TMDLs and NPDES permit limitations; and/or
To serve as screening tools in contaminated Superfund and RCRA site assessments^
Because ESGs are intended to complement existing sediment assessment tools (e.g., bioassays
and benthic community analyses), use of ESGs does not reduce testing or assessment
requirements of existing programs.
The following paragraphs briefly describe how ESGs could be used in specific programs:
State and Tribal Water Quality Standards and Monitoring Programs
EPA recommends that States and Tribes use their narrative water quality criteria (e.g., "no toxics
in toxic amounts") to protect sediment quality as determined necessary to protect and maintain
designated uses. These criteria can be interpreted using whole sediment toxicity tests (along with
benthic community assessments, if desired) as the primary indicator for assessing water quality
and identifying waters not attaining the applicable water quality standards with respect to
sediment toxicity. If testing indicates that a sediment exhibits toxicity, ESGs (along with
Toxicity Identification Evaluations (TIEs), as needed) can be used to help identify the causative
pollutants or pollutant categories. When chemicals for which there are ESGs are identified as the
cause of toxicity, ESGs can be used to help determine pollutant reductions necessary to meet
water quality standards.
Where toxicity testing has not already been performed, available ESG data can be used to help
prioritize water bodies for such testing. ESGs can also be used as benchmarks for monitoring
progress toward meeting water quality standards.
EPA recognizes that some States and Tribes have adopted empirically derived, numeric sediment
criteria, which are defensible when based on local data. EPA recommends that States and Tribes
ES-5
-------
evaluate such empirically derived criteria with respect to ESGs, which are considered appropriate
for nationwide use, to ensure that the empirically derived criteria are adequately protective
against local benthic community impacts. Any locally developed sediment criteria or guidelines
that address other endpoints (such as bioaccumulation or human health) are broader in scope than
ESGs.
TMDLs for Sediment Quality Protection
Section 303(d) of the Clean Water Act (CWA) provides that States and authorized Tribes are to
establish TMDLs at levels necessary to implement the applicable water quality standards. A
TMDL identifies wasteload allocations for point sources and load allocations for nonpoint
sources and natural background. Under EPA's recommended approach to sediment quality
protection, States or Tribes would use whole sediment toxicity tests (and other appropriate
interpretive tools, if desired) to interpret their narrative criteria with respect to sediment toxicity,
in the absence of applicable State- or Tribe-adopted numeric sediment criteria. If the applicable
State or Tribal water quality standard is not attained for a water body, the water body is listed
under CWA Section 303(d) and a TMDL is developed.
ESGs (and TIEs, as necessary) can be used to help identify the pollutants causing sediment
toxicity. When chemicals for which there are ESGs are identified as the cause of the toxicity,
ESGs can serve as chemical concentration target levels that would be expected to eliminate the
impairment and therefore provide a basis for the TMDL. Follow-up monitoring should include
sediment chemistry analyses to verify that numeric targets are being met, as well as whole
sediment toxicity tests to verify that the sediment is not toxic.
Sediment quality modeling is recommended in development of TMDLs addressing sediment
toxicity. There are a number of sediment models available, but States and Tribes should
recognize that sediment modeling is a relatively resource-intensive task.
ES-6
-------
Water Quality-Based NPDES Permit Conditions Addressing Sediment Toxicity
If a discharge is shown, or has reasonable potential, to cause or contribute to an exceedance of
the applicable water quality standards, including narrative criteria, EPA's regulations require the
permitting authority to develop water quality-based effluent limits. Where the exceedance is due
to sediment contamination, the permit limits will then be based on sediment quality protection.
If sediment downstream of a discharge exhibits toxicity and the causative toxicant appears in the
effluent, the permitting authority or permittee should perform a more detailed analysis (i.e.,
modeling) to confirm and quantify the potential impact from the discharge. If modeling indicates
that the discharge contributes to the existing sediment contamination, appropriate effluent
limitations (based on ESGs or other acceptable target) should be developed.
There may be cases where ambient sediment does not yet exhibit toxicity, but a regulatory
authority may want to ensure that a new loading from a point source will not create a sediment
toxicity problem. In this situation, the regulatory authority may want to establish ESGs as the
primary translator for developing a quantitative interpretation of narrative criteria for that
discharge. Under these circumstances, and where predictive modeling indicates that a discharge
would result in an ESG exceedance, the regulatory authority could find reasonable potential for
sediment contamination. ESGs could then be used as the basis for setting effluent limitations to
help meet applicable water quality standards.
Dredged Material Management
The dredged material management program under Section 103 of the Marine Protection,
Research, and Sanctuaries Act and Section 404 of the Clean Water Act relies heavily upon
biological effects based testing of dredged material, which provides a direct measure of toxicity
for the material as a whole. Because toxicity is a concern regardless of which specific
contaminants are responsible for the toxicity, ESGs should not be used to evaluate the suitability
of dredged material for disposal. Although ESGs are not necessary in the evaluation of dredged
material where biological testing occurs, existing ESG data could be part of the existing
information evaluated to determine whether further sediment evaluation is warranted. For
example, existing data indicating that sediment proposed for discharge under the Clean Water
ES-7
-------
Act exceeds an ESG value would contribute to a "reason to believe" determination in Tier I that
further testing is necessary. Further testing would include Tier in biological evaluations.
Superfund (Comprehensive Environmental Response, Compensation, and
Liability Act) Program and RCRA Corrective Action Program
ESGs can be used by investigators during the screening level ecological risk assessment
conducted as part of the Remedial Investigation/Feasibility Study. The ESGs would be used to
screen out contaminants or parts of a site from further consideration. Contaminants that are
below the ESG values would generally not be carried through as Contaminants of Potential
Concern (COPCs) into the baseline risk assessment. However, contaminant concentrations
which are above the ESG values warrant further investigation. ESGs are meant to be used for
screening purposes only; they are not cleanup levels. ESGs may be used in a similar fashion
during the RCRA Facility Investigation under RCRA Corrective Action.
ES-8
-------
1. INTRODUCTION
1.1 PURPOSE
This document provides general guidance to States, Tribes,1 and others2 for applying the U.S.
Environmental Protection Agency's (EPA's) equilibrium partitioning sediment guidelines
(ESGs) for protection of benthic (sediment-dwelling) organisms. This document also describes
the integral role of other sediment quality assessment tools, such as whole sediment toxicity
tests, in water quality programs. Specifically, this document describes EPA's vision of how
ESGs and complementary tools would be utilized in the following programs:
State and Tribal water quality standards and monitoring programs
Total maximum daily load (TMDL) programs
National Pollutant Discharge Elimination System (NPDES) permitting programs
Dredged material management programs
Superfund programs
Resource Conservation and Recovery Act (RCRA) programs
ESG implementation will vary depending upon applicable regulatory requirements and
programmatic needs.
ESGs are sediment chemical concentrations at or below which direct lethal or sublethal effects
on benthic organisms are not expected. ESGs do not currently address potential food chain
effects of bioaccumulative sediment pollutants. EPA intends to undertake additional work to
develop guidance for assessing bioaccumulative pollutants.
'Throughout this document, "States and Tribes" is intended to include the 50 United States, District of
Columbia, Guam, Virgin Islands, American Samoa, all U.S. Commonwealths and Territories, and Indian Tribes that
EPA determines qualify for treatment as States for purposes of water quality standards (40 CFR 131.3).
2This document is also intended for other entities with regulatory authority over water quality programs
(e.g., EPA regional offices and permitting authorities.)
1-1
-------
1.2 NEED FOR SEDIMENT QUALITY PROTECTION
Protecting sediment quality is an important part of restoring and maintaining the biological
integrity of our Nation's waters. Sediment is an integral component of aquatic ecosystems,
providing habitat, feeding, spawning, and rearing areas for many aquatic organisms. Sediment
also serves as a reservoir for pollutants and therefore a source of pollutants to the water column
and organisms. These pollutants can arise from a number of sources, including municipal and
industrial discharges, urban and agricultural runoff, atmospheric deposition, and port operations.
Chemicals that do not easily degrade can accumulate in sediment to much higher levels than
those found in the water column. Contaminated sediment can cause lethal and sublethal effects
in benthic or other sediment-associated organisms. In addition, natural and human disturbances
can release pollutants to the overlying water, where pelagic (water column) organisms can be
exposed. Sediment pollutants can reduce or eliminate species of recreational, commercial, or
ecological importance, either through direct effects or by affecting the food supply that
sustainable populations require. Furthermore, some pollutants can bioaccumulate through the
food chain and pose health risks to wildlife and human consumers even when sediment-dwelling
organisms are not themselves impacted.
The extent and severity of sediment contamination in the U.S. has been documented in the
National Sediment Inventory (NSI)3 and through contaminated site histories. The NSI screening
evaluation of sediment contamination data indicates that associated adverse effects are probable
in thousands of locations distributed throughout the country. These results emphasize the need
for better tools for reducing and preventing sediment contamination. EPA has helped address
this need by developing sediment assessment and management tools, such as whole sediment
toxicity tests, benthic community analyses, and equilibrium partitioning sediment guidelines, as
discussed in the following sections.
3The National Sediment Inventory, or NSI, is the database of sediment quality information used to develop
EPA's 1997 Report to Congress, The Incidence and Severity of Sediment Contamination in Surface Waters of the
United States, Volume 1: National Sediment Quality Survey (U.S. EPA, 1997a). The database is updated biennally
with new available information on sediment quality at sites throughout the U.S.
1-2
-------
1.3 BIOLOGICAL TESTING FOR SEDIMENT ASSESSMENT
1.3.1 Whole Sediment Toxicity Tests (Bioassays)
Whole sediment toxicity tests are a useful tool for sediment quality assessment, and they have an
important role in many water quality programs. They directly measure the toxicity of a sediment
sample to a test species under controlled laboratory conditions, and are especially valuable
because they account for interactive effects of chemical mixtures. A drawback of toxicity tests is
that they only evaluate the particular species and endpoint being tested. Relying on single-
species tests may not protect other, more sensitive species. Additionally, if only lethal or short-
term sublethal endpoints are used, long-term sublethal effects would not be identified.
EPA has published the following guidance documents which provide laboratory methods for
measuring the toxicity of whole sediments:
Methods for Assessing the Toxicity of Sediment-Associated Contaminants with Estuarine and
Marine Amphipods (U.S. EPA,1994a).
Methods for Measuring the Toxicity and Bioaccumulation of Sediment-Associated
Contaminants with Freshwater Invertebrates, Second edition (U.S. EPA, 2000a).
EPA is also developing the following documents:
Methods for Collection, Storage, and Manipulation of Sediments for Chemical and
Toxicological Analyses.
Methods for Assessing the Chronic Toxicity of Marine and Estuarine Sediment-associated
Contaminants with the Amphipod Leptocheirus plumulosus.
1-3
-------
Additional information on sediment bioassays can be found in the following documents, which
pertain to dredged material management:
Evaluation of Dredged Material Proposed for Ocean Disposal Testing Manual [also
referred to as the Ocean Testing Manual or Green Book] (U.S. EPA/USACE, 1991).
Evaluation of Dredged Material Proposed for Discharge in Waters of the U.S. Testing
Manual [also referred to as the Inland Testing Manual or ITM] (U.S. EPA/USACE, 1998).
1.3.2 Benthic Community Assessments
Benthic community assessments are another valuable tool for assessing sediment quality. They
are useful because they reflect field conditions of exposure to toxic pollutants. However, there
are limitations in using benthic community assessments to assess chemical contamination,
because such assessments also reflect non-contaminant effects (e.g., predation, sediment type,
salinity, temperature).
EPA has published the following guidance documents which include methods for performing
benthic community assessments:
Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton,
Benthic Macroinvertebrates and Fish (Barbour et al., 1999).
Macroinvertebrate Field and Laboratory Methods for Evaluating the Biological Integrity of
Surface Waters (Klemm et al., 1990).
-------
1.4 EQUILIBRIUM PARTITIONING SEDIMENT GUIDELINES
Numeric sediment quality guidelines, such as equilibrium partitioning sediment guidelines
(ESGs), are another useful assessment tool, particularly when used in conjunction with biological
assessment methods. They can help identify individual pollutants causing toxicity, and provide
pollutant-specific targets for restoring and protecting sediment quality.
EPA developed the national ESGs for a broad range of sediment types. These guidelines
represent sediment chemical concentrations at or below which direct lethal or sublethal effects on
benthic organisms are not expected.4 EPA developed the guidelines over a period of several
years, with extensive technical review by EPA's Science Advisory Board (SAB).5 EPA recently
finalized the methodologies for deriving nationally applicable ESGs for nonionic organic
chemicals (U.S. EPA, 2000b) and for mixtures of certain metals (cadmium, copper, lead, nickel,
silver, and zinc) (U.S. EPA, 2000c), and also finalized the methodology for deriving site-specific
ESGs (U.S. EPA, 2000d). EPA developed final numeric ESGs for two nonionic organic
pesticides (dieldrin and endrin) (U.S. EPA, 2000e and 2000f), and is currently developing an
ESG for mixtures of polycyclic aromatic hydrocarbons (PAHs). EPA calls these guidelines Tier
1 ESGs because they are based on a full minimum aquatic toxicity data set that EPA specifies for
development of Clean Water Act Section 304(a) water quality criteria (Stephan et al., 1985).
EPA has also verified these ESGs using whole sediment toxicity tests.
In addition, EPA developed Tier 2 ESGs6 for 32 nonionic organic chemicals (U.S. EPA, 2000g).
EPA derives Tier 2 ESGs in the same manner as Tier 1 ESGs, but Tier 2 ESGs can be based on
less extensive data sets. For example, Tier 2 ESGs can be calculated with fewer water column
4ESGs do not currently address potential food chain effects of bioaccumulativc sediment contaminants.
EPA intends to further evaluate food routes of exposure, bioaccumulation, wildlife, and human health endpoints of
concern.
5In the initial stages of development, ESGs were referred to as Sediment Quality Criteria (SQC).
"Tier 2 ESGs were formerly known as Sediment Advisory Levels (SQALs) and were referred to as SQALs
in the National Sediment Inventory (U.S. EPA, 1997a)).
1-5
-------
toxicity data; this is accounted for through an uncertainty factor which generally makes Tier 2
values more conservative. Additionally, EPA has not performed sediment verification tests on
all Tier 2 ESGs. EPA recommends that Tier 2 ESGs be implemented in the same manner as Tier
1 ESGs, but with consideration that there is greater uncertainty associated with Tier 2 values. A
list of available ESGs is presented in Appendix A. Details on the ESG methodologies and
chemical-specific ESGs can be found in the following documents:
Technical Basis for the Derivation of Equilibrium Partitioning Sediment Guidelines (ESGs)
for the Protection ofBenthic Organisms: Nonionic Organics (U.S. EPA, 2000b).
Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection ofBenthic
Organisms: Metal Mixtures (Cadmium, Copper, Lead, Nickel, Silver, and Zinc) (U.S. EPA,
2000c).
Methods for the Derivation of Site-Specific Equilibrium Partitioning Sediment Guidelines
(ESGs) for the Protection ofBenthic Organisms: Nonionic Organics (U.S. EPA, 2000d).
Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection ofBenthic
Organisms: Dieldrin (U.S. EPA, 2000e).
Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection ofBenthic
Organisms: Endrin (U.S. EPA, 2000f).
Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection ofBenthic
Organisms: Nonionics Compendium (U.S. EPA, 2000g).
Evaluation of the Equilibrium Partitioning (EqP) Approach for Assessing Sediment Quality
(U.S. EPA, 1990a).
1-6
-------
An SAB [Science Advisory Board] Report: Review of Sediment Criteria Development
Methodology for Non-ionic Organic Contaminants (U.S. EPA, 1992).
An SAB Report: Review of an Integrated Approach to Metals Assessment in Surface Waters
and Sediments. (U.S. EPA, 2000h).
EPA based the ESGs on the equilibrium partitioning (EqP) theory, which is a conceptual
approach for predicting the bioavailability of sediment-associated chemicals, and therefore, their
toxicity. The theory assumes that sediment-associated chemicals partition to a state
approximating equilibrium between three phases: the interstitial (pore) water, the binding phases
in sediment which limit bioavailability, and the biota. Under this assumption, the pathway of
chemical exposure (i.e., respiration of interstitial water or ingestion of sediment) is not important,
because the activity of the chemical is the same in each equilibrated phase. If the chemical
concentration in any one phase is known, then the concentration in the others can be predicted.
Thus, if it were possible to measure the interstitial water chemical concentration, or to predict it
from the total sediment concentration and the relevant sediment properties (i.e., binding phase
data), then that concentration could be used to quantify the exposure concentration for an
organism.
For ease of measurement, and to avoid complications due to sorption of hydrophobic chemicals
to dissolved organic carbon, EPA based ESGs for nonionic organic chemicals on sediment
concentrations rather than interstitial water concentrations.7 EPA derived these ESGs by
computing the sediment chemical concentration that would be in equilibrium with an interstitial
water concentration equal to a protective water-only effects concentration, such as EPA's
national recommended water quality criteria (WQC) Final Chronic Value (FCV) or Secondary
7The ESG for metals mixtures consists of two alternatives: one based on the sediment phase, and one based
on the interstitial water phase.
1-7
-------
Chronic Value (SCV) for aquatic life protection8. Use of WQC values is supported by WQC
development data, which indicate that benthic species exhibit sensitivity similar to that of water
column species. This approach is desirable because it takes advantage of the extensive biological
effects database used to develop water quality criteria.
To account for varying bioavailability among sediment types, EPA expressed ESGs in terms of
the principle binding phase in sediment that controls the contaminant bioavailability. For
nonionic organic chemicals, research has shown that the primary binding phase is organic
carbon. For cationic metals in anoxic sediments, the primary binding phase is acid volatile
sulfide (AVS).
EPA describes ESGs by the following equations and statements:
Nonionic organic chemicals (U.S. EPA, 2000b)
ESGOC = KOC*FCV
where
ESGOC = Organic carbon-normalized equilibrium partitioning sediment guideline
Koc = Organic carbon-interstitial water partition coefficient (L/goc)
(This value is typically estimated from the octanol-water partition
coefficient, K,,w.)
FCV = Water quality criteria final chronic value (ug/L)
8FCVs are derived from chronic (or a combination of acute and chronic) aquatic toxicity data for organisms
in different taxonomic families, including benthic organisms, according to the procedures contained in the
Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and
Their Uses (Stephan et al., 1985). The FCV is intended to protect 95% of a group of diverse genera from direct
lethal or sublethal effects. SCVs are based on fewer supporting toxicity data than FCVs and therefore derived using
an added uncertainty factor. Tier 2 ESGs are generally based on SCVs.
As an alternative to using the FCV or SCV, site-specific values can be developed to account for differences between
the sensitivities of benthic organisms which occur at a site and those organisms which were used to derive the
FCV/SCV (U.S. EPA, 2000d).
1-8
-------
If the chemical concentration in sediment is at or below the ESG, adverse effects are not
expected.
Example:
The freshwater ESG for endrin (log K^ = 4.97 L/kg, FCV = 0.05805 ug/L) is calculated as
follows:
ESGOC= (10497 L/kgoc) * (10-3 kgoc/goc) * (0.05805 ug endrin/L) = 5.4 ug endrin/goc
Benthic organisms should be acceptably protected in freshwater sediments containing <5.4 ug
endrin/goc.
Metals mixtures (cadmium, copper, lead, nickel, silver, and zinc) (U.S. EPA, 2000c)
The ESG for metals mixtures consists of two alternatives. Sediment is considered acceptable for
the protection of benthic organisms if either guideline is met.
Either:
1) Acid Volatile Sulfide Guideline
Sediments containing these metals are acceptable for the protection of benthic organisms if
SEMT < AVS
where
SEMT = Simultaneously extracted concentration of the six metals (umol/g)
AVS = Acid volatile sulfide (umol/g)
Or:
2) Interstitial Water Guideline
Alternatively, sediments containing these metals are acceptable for the protection of benthic
organisms if
EiMJ/FCV,d <> 1
where
[M; d] = Dissolved concentration of the i"1 metal in the interstitial water
FCV: d = Water quality criteria final chronic value for the i"1 metal
1-9
-------
That is, the guideline is met if the sum of the interstitial water concentrations divided by the
respective water quality criteria final chronic values for each of the metals is less than or equal to
one.
Example:
Consider a freshwater sediment with the following interstitial water metals concentrations,
assuming the final chronic values are equal to the national recommended water quality criteria
(U.S. EPA, 1999a):
Interstitial Water Final Chronic
Concentration Value
Metal (Dissolved. |ig/L) (Dissolved, ug/L)
Cadmium 0.3 2.2
Copper 2.1 9.0
Lead 0.25 2.5
Nickel 10 52
Zinc 30 120
In this case, £j[Miid]/FCViid = (0.3/2.2) + (2.1/9.0) + (0.25/2.5) + (10/52) + (30/120) = 0.9. Since
this value is < 1, the sediment is considered acceptable for the protection of benthic organisms.
The EqP approach to developing sediment guidelines for the protection of benthic organisms
offers advantages over empirical approaches, which derive guidelines from paired sediment
chemical concentration and biological effects data.9 The data used in empirical approaches
typically originate from sediments containing a mixture of contaminants, making it difficult to
ascribe the cause of toxicity to a particular chemical. By contrast, the EqP theory accounts for
the bioavailability of chemicals, using individual chemical data. The EqP theory thus facilitates
the identification of causative agents of toxicity and the establishment of targets for pollutant
reduction measures.
'Examples of empirical sediment quality guidelines include Apparent Effects Thresholds (AETs), Effects
Range-Low (ERLs) and Effects Range-Median (ERMs), Probable Effects Levels (PELs), and Threshold Effects
Levels (TELs). More information on these guidelines can be found in Volume 1 of The Incidence and Severity of
Sediment Contamination in Surface Waters of the United States (U.S. EPA, 1997a).
1-10
-------
Despite the strengths of the ESG methodology, there are limitations which must be recognized
when applying ESGs in the natural environment. The limitations associated with ESGs include
the following (U.S. EPA, 2000b; U.S. EPA, 2000c; U.S. EPA, 2000d):
General
ESGs do not address bioaccumulation or food-chain effects. This includes effects from
bioaccumulation of metals sometimes observed when the metals ESG is not exceeded.
ESGs do not account for interactive (synergistic, antagonistic) effects of all chemicals in
sediment, aside from chemical mixtures addressed by specific guidelines (e.g., cationic
metals, PAHs).
Factors that may make ESGs overprotective:
Binding phases other than the primary binding phase are not considered by the ESGs and
may further decrease bioavailability in some sediments.10
The equilibrium partitioning theory assumes sediments are at or near equilibrium.
Disequilibrium associated with sediment resuspension would tend to make ESGs
overprotective until near-equilibrium conditions are re-established.
Partitioning of contaminants from sediments may be kinetically-limited in some cases.
Additionally, the following limitations apply specifically to the metals mixtures ESG based on
AVS-SEM:
Proper sampling is especially important, because SEM, and AVS in particular, vary both
spatially and seasonally. Sampling personnel should be careful to measure the sediment
strata of concern, and should consider seasonal sampling to the extent possible. Personnel
should avoid one-time sampling in the summer (when AVS tends to be highest).
'°The primary binding phase for nonionic organic chemicals is organic carbon; the primary binding phases
for metals are AVS and organic carbon for metals. A site-specific ESG can be developed to account for additional
binding phases (such as pure chemical or soot carbon) (U.S. EPA, 2000d).
1-11
-------
The AVS-SEM methodology is not applicable to aerobic sediments. Additionally, for
anaerobic sediments, factors that affect redox conditions (e.g., seasonal patterns, exposure
during tides, resuspension, flooding, and dredging operations) may affect the applicability of
the AVS guideline.
1.5 ESG IMPLEMENTATION APPROACH
In consideration of the strengths and limitations of the ESG methodology, EPA does not
recommend that the ESGs published concurrently with this draft document be used as numeric
criteria to be adopted by States or Tribes as part of their water quality standards under Section
303(c) of the Clean Water Act. Rather, EPA recommends that the ESGs be used in the following
manner:
To help prioritize sites for sediment toxicity or other appropriate testing (as part of State or
Tribal water quality monitoring programs);
To help identify causative pollutants when toxicity is indicated by bioassays or other tools;
To use, as appropriate, in developing TMDLs and NPDES permit limitations; and/or
To serve as screening tools in contaminated Superfund and RCRA site assessments.
1-12
-------
2. INCORPORATION OF EQUILIBRIUM
PARTITIONING SEDIMENT GUIDELINES INTO
STATE AND TRIBAL WATER QUALITY STANDARDS PROGRAMS
2.1 PROTECTING SEDIMENT QUALITY THROUGH STATE AND
TRIBAL WATER QUALITY STANDARDS PROGRAMS
The Clean Water Act (CWA) was established to restore and maintain the quality of waters of the
United States. Under the CWA, States and authorized Tribes are required to establish water
quality standards (WQS) that define the water quality goals of a water body, or portion thereof,
by: 1) designating the use or uses of the water; 2) setting criteria necessary to protect the uses;
and, 3) establishing antidegradation policies to address degradation of water quality.1
Sediment underlying surface water is recognized as a significant source of, and sink for, toxic
pollutants in the aquatic environment. States and Tribes should therefore address sediment
quality as an integral component of their water quality standards programs. EPA strongly
encourages States and Tribes to assess the adequacy of their WQS programs during their triennial
review process, and to incorporate appropriate sediment quality protection policies and
procedures to protect and maintain designated uses.
The Water Quality Standards Handbook, Second Edition (U.S. EPA, 1994b), provides the
framework and specific procedures for development and application of State and Tribal WQS.
However, only a brief overview of sediment protection components is provided. This chapter of
the ESG Implementation Framework is intended to provide supplemental guidance on
incorporating sediment quality protection into the existing framework of State and Tribal WQS
programs.
'See 40 Code of Federal Regulations (CFR) Part 131 for the Water Quality Standards Regulation.
2-1
-------
EPA does not recommend that ESGs be adopted as numeric criteria. Rather, EPA recommends
that States and Tribes use their narrative water quality criteria to protect sediment quality as
determined necessary to protect and maintain designated uses. Under this approach, the narrative
criteria can be implemented using whole sediment toxicity tests (along with benthic community
assessments, if desired) as the primary indicator for assessing water quality and determining
whether waters are attaining the applicable water quality standards with respect to sediment
toxicity (see Section 1.3 for a description of appropriate toxicity tests). If testing indicates that a
sediment exhibits toxicity, ESGs (along with Toxicity Identification Evaluations (TIEs), as
needed) can be used to help identify the causative pollutants or pollutant categories. When
chemicals for which there are ESGs are identified as the cause of toxicity, ESGs can be used to
help determine pollutant reductions necessary to meet the State or Tribal water quality standards.
Available ESG data can also be used to help prioritize water bodies for sediment toxicity testing
where such testing has not already been performed. Additionally, ESGs can be used as
benchmarks for monitoring progress toward attaining water quality standards.
The following provides more detail on how sediment protection would be addressed by WQS,
including: 1) a description of how sediment quality can be considered in designated use analyses
in State and Tribal WQS programs; 2) an approach for adopting State and Tribal water quality
criteria that are protective of sediment quality; and 3) a discussion of how a State or Tribe might
address sediment quality through its WQS implementation procedures (e.g., translator and
mixing zone policies).
2.1.1 Relationship of Sediment Quality to Designated Uses
Use designations for each water body or water body segment are the foundation of the WQS
program. The designated uses define the water quality goals of a water body or segment and are
not limited to uses that are currently being attained. At a minimum, States and authorized Tribes
must provide water quality for the protection and propagation of fish, shellfish, and wildlife, and
provide for recreation in and on the water, where attainable (CWA Section 101 (a)). Sediment
quality can affect whether or not waters are attaining designated uses. Therefore, it is necessary
2-2
-------
and appropriate to assess and protect sediment quality, as an essential component of the total
aquatic environment, to achieve and maintain designated uses.
To determine use attainment, States and Tribes examine the physical, chemical, and biological
characteristics of a water body. EPA recommends using bioassays (and other appropriate
assessment tools, if desired) to assess whether sediment toxicity is preventing use attainment. If
sediment toxicity is indicated, ESGs can be used to help identify the causative pollutant. States
and Tribes can then use this information to assess the potential for attaining designated uses
through the implementation of available controls.
2.1.2 Development of Water Quality Criteria to Protect Sediment Quality
States and authorized Tribes are required to adopt water quality criteria that protect designated
uses. Such criteria must be based on sound scientific rationale, must contain sufficient
parameters to protect the designated uses, and can be expressed in either numeric or narrative
form. Narrative criteria are descriptions of the conditions necessary for a water body to attain its
designated use, while numeric criteria are values expressed as levels, concentrations, toxicity
units, or other numbers deemed necessary to protect designated uses. Narrative criteria can be
used to assess water quality, and also to establish pollutant-specific discharge limits where there
are no numeric criteria or where such criteria are not sufficient to protect the designated use. A
"translator" identifies a process, methodology, or guidance that States or Tribes will use to
quantitatively interpret narrative criteria statements. Translators may consist of biological
assessment methods (e.g., field measures of the biological community), biological monitoring
methods (e.g., laboratory toxicity tests), models or formulae that use input of site-specific
information/data, or other scientifically defensible methods.
ESGs are pollutant-specific sediment numeric values at or below which toxic effects in benthic
organisms are not expected. Thus, they are effective tools for restoring and protecting designated
uses impaired by specific pollutants in sediment. However, ESGs are not always sufficient for
assessing sediment toxicity, because other pollutants not addressed by ESGs may be present that
cause or contribute to toxic effects. To a significant extent, sediments in depositional zones tend
2-3
-------
to accumulate a mixture of pollutants. On the other hand, variables such as additional binding
phases not factored into the application of the equilibrium partitioning theory, may provide a
degree of protection not accounted for by the ESG. Because of such limitations, EPA does not
recommend adoption of ESGs as numeric water quality criteria for the protection of CWA
Section 101(a) designated uses. In other words, EPA does not believe that ESGs are appropriate
as sole indicators of use attainment. Instead, EPA recommends using narrative criteria to address
sediment toxicity, and using bioassays and ESGs as a basis for interpreting narrative criteria and
developing pollutant reduction strategies2
Examples of narrative criteria include:
All State waters must, at all times and flows, be free from substances that are toxic to humans
or aquatic life.
All waters, including those within mixing zones, shall be free from substances attributable to
wastewater discharges or other pollutant sources that:
- Settle to form objectionable deposits;
- Float as debris, scum, oil, or other matter forming nuisances
- Produce objectionable color, odor, taste, or turbidity
- Cause injury to, or are toxic to, or produce adverse physiological responses in
humans, animals, or plants
- Produce undesirable or nuisance aquatic life.
While statements like these are broad enough to include sediment quality, States and Tribes
could add an additional narrative criterion to specifically include sediment. Following are two
examples of narrative criteria used in State and Tribal WQS programs to protect sediment
quality. They can generally be described as requiring "no toxics in toxic amounts":
is document does not address the use of empirically derived numeric sediment quality criteria, which
some States and Tribes have adopted. This approach is defensible when the values are derived from local data,
though EPA recommends that States and Tribes evaluate such criteria with respect to ESGs to ensure that the
empirically derived criteria are adequately protective against local benthic community impacts. ESGs are
theoretically derived to account for bioavailability, and are considered appropriate for nationwide use in the
manners described.
2-4
-------
As an integral part of the overall aquatic system, sediment shall be free of toxic substances in
amounts considered to cause unacceptable toxicity to resident biota necessary to support
designated uses.
All sediments, at all times and at all places, shall be free from substances or materials
attributable to municipal, industrial, commercial, domestic, agricultural, land development, or
other sources that are in concentrations that will cause injury to, or are toxic to, or produce
adverse effects in, humans, animals, aquatic life, or plants.
States and Tribes should adopt scientifically defensible methods for interpreting and
implementing their narrative criteria. EPA recommends that States and Tribes use bioassays
(and benthic community assessments, if desired) to ascertain whether sediments comply with a
typical "no toxics in toxic amounts" narrative criterion. The following section provides more
information on sediment criteria implementation procedures.
2.1.3 Implementation Procedures
States and Tribes must ensure that the policies and procedures of their WQS program are
adequate to implement the standards. Consideration should be given to the following items with
respect to sediment quality protection in State and Tribal WQS programs:
Procedures for translating narrative criteria
Mixing zone policies
The following sections provide guidance to water quality managers on how protection of
sediment quality can be incorporated into the application and implementation procedures of a
State or Tribal WQS program.
2-5
-------
2.1.3.1 Translator Procedures
To protect sediment quality through their water quality standards (designated uses and narrative
criteria), a State or Tribe must determine how to assess attainment of those standards. One
option is to use a comprehensive weight-of-evidence approach. An example of this approach is
the Sediment Quality Triad, which consists of three components (Chapman, 1992):
Sediment chemistry - to measure chemical contamination
Sediment bioassays - to measure toxicity
In situ biological variables - to measure alteration of resident biota (e.g., change in benthic
community structure)
These components provide complementary data. Sediment chemistry data provide information
on contamination, and when used with ESGs, also provide insight into potential biological
effects.3 Sediment bioassays are an important component of sediment assessment because they
provide direct evidence of sediment toxicity. However, they do not identify the causative
pollutant. Additionally, the laboratory conditions under which bioassays are conducted may not
accurately reflect field conditions of exposure to toxic chemicals. In situ biological studies (such
as benthic community composition analyses) are useful because they account for field
conditions. However, interpretation with respect to chemical contamination may be confounded
by non-contaminant effects (e.g., competition, predation, sediment type, salinity, temperature,
recent dredging). Because each component alone has limitations, the Triad approach uses all
three sets of measurements to assess sediment contamination. Table 2-1 lists possible
conclusions that can be drawn from various sets of test results.
3In the past, the relationship between contaminants in sediment and their bioavailability was poorly
understood. Therefore, sediment chemistry data were considered to be suitable for providing information on
contamination, but not necessarily on biological effects (Chapman, 1992). ESGs increase the usefulness of
sediment chemistry data, as they are theoretically derived to account for bioavailability.
2-6
-------
Table 2-1.
Possible Conclusions Provided by Using the Sediment Quality Triad Approach
Contamination
+
+
-
+
-
+
Toxicity
+
-
+
-
+
+
Community
Alteration
+
-
_
+
-
+
+
Possible Conclusions
Strong evidence for pollutant-induced degradation.
Strong evidence for absence of pollutant-induced
degradation.
Pollutants are not bioavailable.
Unmeasured pollutants or conditions exist that have the
potential to cause degradation.
Alteration is probably not due to toxic pollutants.
Toxic pollutants are stressing the system.
Unmeasured toxic pollutants are causing degradation.
Pollutants are not bioavailable or alteration is not due
to toxic pollutants.
"+" indicates measured difference between test and control or reference conditions.
"-" indicates no measurable difference between test and control or reference conditions.
Reference: Chapman (1992).
As indicated in Table 2-1, there may be instances where ESG data, sediment toxicity tests, and
benthic community analyses produce conflicting results. In these cases, the interpretation
becomes more complex, but it does not necessarily indicate that any of the data sets are "wrong."
For example, such results can arise from the fact that individual ESGs consider only the effects
of the pollutant or group of pollutants for which they are derived. Therefore, if a sediment shows
toxicity but does not exceed the ESG for a pollutant of interest, it is likely that the toxicity is due
to a different pollutant or pollutants.
In other instances, it may be that an ESG is exceeded but the sediment is not toxic. These
findings are not mutually exclusive, because the inherent sensitivity of the two measures is
different. ESGs are intended to protect relatively sensitive species against both acute and chronic
effects, whereas toxicity tests are run with specific species that may or may not be sensitive to
the pollutants of concern, and sometimes do not encompass the most sensitive endpoints (e.g.,
growth or reproduction). It is also possible for a sediment above the ESG to be non-toxic if there
2-7
-------
are site-specific conditions not accounted for by the equilibrium partitioning model and its
assumptions (e.g., a sediment may contain additional binding phases not considered by the ESGs
which may further decrease pollutant bioavailability).
A comprehensive approach using multiple assessment methods helps eliminate false conclusions
brought about by relying solely on one method of evaluation. It can also be cost-effective when
compared with the costs of environmental damage and remediating such damage. However,
EPA recognizes that such an approach can be resource-intensive. As an alternative, States and
Tribes may wish to use a tiered approach to routine sediment quality assessment. Under the
tiered approach, the narrative criteria would be interpreted using bioassays as the primary
assessment translator (for determining attainment of the criteria), and ESGs as the chemical
cause translator (to provide a basis for developing pollutant reduction strategies for specific
chemicals when toxicity is indicated by bioassays).4 Bioassessments could be used to
supplement findings of toxicity, as a prioritization tool to determine where toxicity testing should
be performed, or as an additional assessment translator to determine impairment. Figure 2-1
illustrates how translators could be used for interpreting narrative criteria for sediment quality
protection.
"There may be cases where ambient sediment does not yet exhibit toxicity, but a regulatory authority may
want to ensure mat a new loading from a point source will not create a sediment toxicity problem. In this situation,
the regulatory authority may want to establish ESGs as the primary translator for interpreting the narrative criteria
for that discharge.
2-8
-------
Figure 2-1.
Narrative Criteria Translators for Sediment Quality Protection
Sediment Quality Assessment
& Attainment of Standards/
NPDES Reasonable Potential Analysis
Assessment Translator
Toxicity testing (and benthic
community assessment, if
desired)
Perform Toxicity
Identification Evaluation ;
(TIE) as necessary
Chemical Cause
Translator:
ESGs
Continue monitoring
as necessary
Derive effluent
limitations
or load allocations
based on ESGs or
other appropriate targets
Under the tiered approach to assessing existing sediment quality, the State or Tribe would
perform appropriate lethal and sublethal sediment toxicity tests to evaluate whether the sediment
is toxic.5 A finding of toxicity should trigger a sediment chemistry analysis, if one has not
already been performed. The chemical analysis should be performed on samples originating
from the same composited homogenate used for the bioassays, so that paired data can be
'See Section 1.3 for a listing of available EPA methods manuals. A comprehensive testing plan would
include the following endpoints: survival, growth, reproduction (and, where applicable, emergence).
2-9
-------
obtained (Chapman, 1992). The chemistry data can be compared to ESGs to help determine
which chemicals may be causing toxicity.6
Under this tiered approach, sediment chemistry data would be used as explanatory variables
rather than primary indicators of sediment toxicity. Nevertheless, chemistry data in themselves
are useful in determining sediment contamination trends. These data can also be compared to
ESGs to help identify areas which may have the potential for adverse impacts. States and Tribes
can use ESGs as an effective prioritization tool to help determine which sediments should be
targeted for biological testing. That is, other factors being equal, sediments with chemical
concentrations exceeding ESGs would have higher priority for further testing compared with
sediments that meet the ESGs. Chemical concentrations exceeding ESGs could also indicate the
need to monitor and assess water column concentrations for those chemicals.
A recommended structure for a tiered approach that utilizes both chemical and biological tests is
presented below:
Tier 1 Perform appropriate sediment toxicity tests7
- Sufficient sample size should be collected to allow for concurrent or subsequent
chemical testing.
- Conduct appropriate lethal and sublethal toxicity tests.
- If the sediment is not found to be toxic, and there is no other evidence (e.g., from
benthic community analyses) of adverse impact, then the water quality standard may
be considered attained, and additional testing is not necessary.
- If the sediment is found to be toxic, or if adverse impact is otherwise indicated, then
the water quality standard may not be attained. If it is determined that the water
6A TIE may be needed to identify the cause of toxicity. See Ankley & Schubauer-Berigan (1995) and U.S.
EPA (199la) for information on performing sediment TIEs. EPA is developing additional guidance on performing
sediment TIEs.
7A State or Tribe may wish to use sediment chemistry data to help prioritize areas for sediment toxicity
testing.
2-10
-------
quality standard is not attained, the water body should be listed under CWA Section
303(d) as needing a Total Maximum Daily Load (TMDL). Proceed to Tier 2.
Tier 2 Determine sources and establish TMDL
- For waters listed under Section 303(d), develop TMDL and identify loading
allocations for point sources and nonpoint sources. This could be initiated with
the following steps:
Assess spatial extent of sediment toxicity and perform chemical testing of
sediments
- Use bioassays (and other assessment methods, if desired) to determine
spatial extent of impact.
- Analyze sediment samples for chemicals for which ESGs exist, as well as
other chemicals anticipated based on past and current pollutant sources.
Determine cause of toxicity
- Compare chemical data to ESGs to help identify pollutants causing
toxicity.
- Conduct sediment TIE as necessary.
EPA recognizes that there are limitations in relying on whole sediment toxicity tests to determine
attainment of water quality standards. Although test organisms are selected on the basis of
overall sensitivity to chemical pollutants and ecological relevance, toxicity tests are conducted
with a limited range of species whose sensitivity cannot be known when the chemicals of
concern are unknown. In contrast, ESGs consider the observed range in species sensitivity and
are derived with the intention of protecting the overall benthic community. ESGs also consider
sensitive endpoints and long exposure durations that may not be represented by the test
procedures used to evaluate sediment toxicity. On the other hand, toxicity tests have strengths in
being able to detect effects from unknown or unmeasured chemicals and interactive toxicity of
multiple chemicals (beyond those chemical groups addressed by ESGs). Sediment assessments
2-11
-------
are strongest when ESGs and sediment toxicity tests are used in combination to balance their
relative strengths and weaknesses.
2.7.3.2 Mixing Zone Policies
States and Tribes have the discretion to adopt mixing zone policies as part of their water quality
standards, [see EPA's Technical Support Document for Water Quality-Based Toxics Control
(TSDWQ) (U.S. EPA, 1991b)]. EPA's current policy addresses mixing zones as allocated
impact zones where certain numeric criteria may be excluded as long as: the designated uses of
the water body as a whole are not impaired; there is no lethal response to organisms passing
through the mixing zone; and there is no significant risk to human health.
EPA believes that the use of sediment "impact zones" analogous to water column mixing zones
is inappropriate due to fundamental differences between the two media. Sediments can act as a
repository for contaminants that will have a continual impact on the resident benthic community,
thus impairing the designated use of the water body. An aqueous mixing zone disappears upon
cessation of a permitted discharge, and water quality is restored to pre-discharge conditions. By
contrast, the sediment impact zone still exists when a discharge ceases, and recovery may take
many years or require remediation. Moreover, contaminated sediment in an impact zone can be
resuspended and moved downstream. Therefore, EPA recommends that States and Tribes not
authorize sediment impact zones. A State or Tribe may wish to conduct modeling analyses of
the sediment deposition zone to predict whether a discharge would create a sediment impact zone
over time. Since ESGs are concentrations below which toxic effects on benthic organisms are
not expected, modeled concentrations below the ESGs would contribute to a finding that the
discharge would not result in an impact zone. Conversely, if modeled concentrations exceed
ESGs, additional limits may be needed to prevent an impact zone from developing. Examples of
available models are described in Appendix B.
2-12
-------
3. DEVELOPMENT OF TOTAL MAXIMUM
DAILY LOADS (TMDLs) FOR SEDIMENT QUALITY PROTECTION
3.1 INTRODUCTION
Section 303(d) of the Clean Water Act (CWA) and its implementing regulations (40 CFR 130.7)
require States and authorized Tribes to establish total maximum daily loads (TMDLs) at levels
necessary to implement applicable water quality standards. TMDLs identify the loading capacity
of the water body, as well as wasteload allocations (WLAs) for point sources and load allocations
(LA) for nonpoint sources and natural background. Under EPA's recommended approach to
sediment quality protection, the State or Tribe would establish a TMDL to address sediment
toxicity when the narrative criterion (e.g., "no toxics in toxic amounts") is exceeded. This
criterion would be interpreted using sediment toxicity tests as the primary indicator for assessing
water quality. If testing indicates that a sediment exhibits toxiciry, ESGs can be used to help
identify the causative pollutants. ESGs can also serve as target levels that would be expected to
eliminate the impairment and therefore serve as a basis for the TMDL.
Developing a TMDL is a mass balance exercise that considers contaminant loads (particulate and
dissolved) from all sources, incorporates dilution and downstream fate and transport, includes a
margin of safety, and allocates the permissible pollutant load among point sources, nonpoint
sources, and natural/background sources. A TMDL is a written plan and analysis established to
ensure that a waterbody or group of waterbodies within a watershed will attain and maintain
water quality standards throughout the year. A TMDL identifies the wasteload allocations and
load allocations that together, along with a consideration of a margin of safety and seasonal
variations, will achieve water quality standards.
A Waste Load Allocation is the portion of a receiving water's loading capacity that is
allocated to one of its existing or future point sources of pollutants that are subject to
National Pollutant Discharge Elimination System (NPDES) permits.
3-1
-------
A Load Allocation is the portion of a receiving water's loading capacity that is attributed
either to one of its existing or future sources of pollutants that are not subject to NPDES
permits. This includes nonpoint sources, point source discharges of storm water not subject
to NPDES, air deposition, ground water, and pollutant sources upstream of the waterbody
segment for which a TMDL is established.
A Margin of Safety (MOS) is a required component of the TMDL that accounts for the
uncertainty about the relationship between the pollutant loads and the quality of the receiving
water body. The MOS may be incorporated implicitly through conservative assumptions
used to develop the TMDL or explicitly by setting aside a portion of the receiving water's
loading capacity.
The TMDL process is defined in EPA's Guidance for Water Quality-based Decisions: The
TMDL Process (U.S. EPA, 1991c)' and in a series of additional technical documents that define
the mechanics of implementing TMDLs (U.S. EPA 1984; 1986a; 1986b; 1990b). The guidance
provided in those documents also applies to TMDLs for sediment toxicity. The following
sections of this chapter discuss considerations unique to sediment quality protection, as well as
guidance for incorporating ESGs into the TMDL process.
3.1.1 Basis for Listing Water Bodies as Water Quality-Limited due to Sediment Toxicity
States and authorized Tribes are required to identify waters not attaining applicable water quality
standards (designated uses and water quality criteria). As discussed in Chapter 2, EPA
recommends that States and Tribes use a "no toxics in toxic amounts" narrative criterion to
protect sediment quality. EPA recommends that States and Tribes interpret this criterion using
whole sediment toxicity tests as described in Section 1.3 and Section 2.1.3. Other appropriate
interpretive tools, such as bioassessments, could also be used to ascertain impairment. If the
'EPA is in the process of revising this guidance. The second edition was published in draft in August
1999. The final document is expected in September 2000. When published, the new guidance will supercede the
1991 document.
3-2
-------
applicable State or Tribal water quality standard is not attained for a water body, the water body
is listed under CWA Section 303(d) as needing a TMDL.2
3.1.2 Identification of Water Quality Indicators and Target Values
A key component of TMDL development is identification of water quality indicators and target
values that can be used to evaluate and determine attainment of water quality criteria in the listed
water body. EPA recommends using whole sediment toxicity tests as the primary water quality
indicator with respect to sediment toxicity. States and Tribes could also use benthic community
assessments or other appropriate measures as water quality indicators.
If a water body is impaired due to sediment toxicity, the State or Tribe can use toxicity
identification evaluation (TIE) procedures to identify the suspected pollutant or pollutants
causing the impairment. ESGs can be used to help identify the pollutant causing toxicity, but
they may not always be the definitive means. A toxicity identification evaluation is a
comprehensive approach to identifying the causes of the toxicity.3 When chemicals for which
there are ESGs are identified as the cause of the toxicity, ESGs can serve as chemical
concentration target levels that would be expected to eliminate the impairment and therefore
provide a basis for the TMDL.4
3.1.3 Sediment Quality Modeling
In developing a TMDL that addresses sediment toxicity, sediment quality modeling is
recommended to characterize the problem, quantify the source contributions, and establish
allocations. An important component of this is determining where long-term sediment
deposition is occurring, and the probability of contaminant accumulation in this sediment
2EPA is in the process of revising its TMDL rules. Under the expected new rule, impairments due to
sediment toxicity would be listed on Part 1 of the section 303(d) list. The first step of the TMDL would be to
identify the pollutant(s) causing the toxicity.
3See Ankley & Schubauer-Berigan (1995) and U.S. EPA (199la) for information on performing sediment
TIEs. EPA is developing additional guidance on performing sediment TIEs.
4A State or Tribe may wish to derive site-specific sediment guidelines to serve as a basis for a TMDL.
Guidance for deriving site-specific ESGs is provided by U.S. EPA (2000d).
3-3
-------
deposition zone (SDZ). Long-term deposition is emphasized because ESGs were developed for
the protection of resident benthic species; that residency is dependent on relatively stable
sediment conditions. Short-term SDZs should not be considered for TMDLs unless it can be
demonstrated that localized benthic populations are affected and the effects of the SDZ will
persist beyond the time it will take to reduce the contaminant loadings causing impairment. In
this situation, the TMDL will likely address the cause of the SDZ and may focus on removing
that cause. It is important to note that a given water body is likely to have multiple SDZs, and in
some cases it may be difficult to identify a single source of pollutants causing contamination
within an SDZ.
Simulation modeling (as well as chemical-specific monitoring) can be an important tool for
defining SDZ boundaries and linking sediment pollutant contamination to sources. Because
sediment transport and deposition are complex and long-term processes, sediment quality
simulation is considerably more complex than water mixing zone modeling. The modeling tool
should include a sophisticated hydrodynamic component capable of simulating sediment
erosion/resuspension, transport, and deposition, linked to an appropriate dynamic water quality
model. Together, these models can simulate long-term deposition of sediments and enrichment
of pollutants in sediment deposits. This modeling effort will be an iterative process, with
successive runs of the selected model required for each group of pollutants causing
contamination, to account for contributors to the water body, and to adjust loadings to determine
the TMDL that will achieve compliance with the target values. More information on sediment
modeling data needs and available models is presented in Appendix B.
3-4
-------
3.1.4 Follow-up Monitoring
The TMDL process includes follow-up monitoring to evaluate whether the TMDL and associated
control actions are sufficient for attaining water quality goals. For TMDLs that address sediment
toxicity, monitoring should include sediment chemistry analyses to verify that numeric targets
are being met, as well as whole sediment toxicity tests to verify that the sediment is not toxic.5
SEPA is in the process of revising its TMDL rules. Under the expected new rule, TMDLs will be required
to include a follow-up monitoring or modeling plan to assess the performance towards attaining water quality
standards, and to include procedures to revise the TMDL where there is insufficient progress.
3-5
-------
THIS PAGE INTENTIONALLY LEFT BLANK
-------
4. WATER QUALITY-BASED NATIONAL POLLUTANT DISCHARGE
ELIMINATION SYSTEM (NPDES) PERMIT CONDITIONS FOR
SEDIMENT PROTECTION
4.1 ADDRESSING SEDIMENT CONTAMINATION THROUGH THE
NPDES PROGRAM
Point source effluent limitations are implemented through the National Pollutant Discharge
Elimination System (NPDES) permitting program. Limitations may be based on national
effluent limitations guidelines and standards for specific industrial categories, or more stringent
limitations may be imposed as necessary to meet water quality standards. If a discharge causes,
has reasonable potential to cause, or contributes to the nonattainment of water quality standards,
EPA's regulations require the permitting authority to develop water quality-based effluent
limitations. For example, where water quality standards include chemical-specific, numeric
criteria for sediment quality protection, and a discharge causes, has the reasonable potential to
cause, or contributes to an excursion of one of these criteria, the permitting authority must
develop water quality-based effluent limits for that parameter. Also, if a discharge has the
reasonable potential to cause or contribute to an in-stream excursion of a narrative criterion
prohibiting sediment contamination, water quality-based limits based on sediment quality
protection6 would be developed.
EPA anticipates that most sediment quality-based limits will be developed as part of a Total
Maximum Daily Load (TMDL) addressing sediment pollutants. In accordance with EPA's
recommended approach, described in Chapters 2 and 3, States and Tribes would use bioassays as
the primary indicator with respect to sediment toxicity in determining the need for a TMDL to
attain applicable water quality standards. ESGs could then be used as sediment chemical
concentration target levels for the TMDL.
6For conciseness, the term "sediment quality-based limits" is sometimes used in this document in place of
"water quality-based limits based on sediment quality protection."
4-1
-------
There may be cases where ambient sediment does not yet exhibit toxicity, but a regulatory
authority may want to ensure that a new loading from a point source will not create a sediment
toxicity problem. In this situation, the regulatory authority may want to establish ESGs as the
primary translator for developing a quantitative interpretation of narrative criteria for that
discharge.
The following provides a brief discussion of the process for developing water quality-based
effluent limits and other special conditions to protect sediment quality.
4.1.1 Developing Water Quality-Based Effluent Limits and Other Requirements for
Sediment Quality Protection
Regulations at 40 CFR Part 122.44(d)(l) require permitting authorities to determine "whether a
discharge causes, has the reasonable potential to cause, or contributes to an in-stream excursion
above a narrative or numeric criteria within a State [or Tribal] Water Quality Standard," and to
develop water quality-based NPDES permits accordingly. In considering the impact of point
source discharges on sediments, regulatory authorities should obtain sediment toxicity test data
from in-place sediments downstream of the discharges.7 If the sediment exhibits toxicity, and the
causative toxicant appears in an effluent, the regulatory authority or permittee should perform a
more detailed analysis to confirm and quantify the potential impact from the discharge. Often,
this analysis will take place in the context of a TMDL, as described in Chapter 3. In some cases,
a regulatory authority may conduct this analysis for a single discharge where no TMDL has been
developed. In such cases, the regulatory authority could employ the same sediment quality
models described for use in developing TMDLs (see Appendix B). If modeling indicates that the
discharge causes or contributes to the existing sediment contamination, appropriate effluent
limitations (based on using an ESG or other acceptable target as a quantitative translation of the
narrative criteria) should be developed.
7If sediment toxicity data is not available, but other data (e.g., effluent characteristics, sediment chemistry
data) indicate that a discharge may be contributing to sediment toxicity, the permitting authority could include
special conditions in the permit requiring toxicity testing on downstream sediments.
4-2
-------
There may be cases where ambient sediment does not yet exhibit toxicity, but a regulatory
authority may want to ensure that a new loading from a point source will not create a sediment
toxicity problem. In this situation, the regulatory authority may want to establish ESGs as the
primary translator for developing a quantitative interpretation of narrative criteria for that
discharge. Under these circumstances, and where predictive modeling indicates that a discharge
would result in an ESG exceedance, the regulatory authority could find reasonable potential for
sediment contamination. ESGs could then be used as the basis for setting effluent limitations to
help meet applicable water quality standards. ESGs are considered an appropriate basis for
establishing permit limits because sediment concentrations of chemicals at or below the ESG are
not expected to cause an adverse impact to benthic organisms.
Sediment quality-based effluent limitations will be chemical-specific effluent limits, derived
using predictive models such as those described in Appendix B. This approach is similar to the
modeling methodology used for water column contaminants, which involves calculation of an
effluent limit based upon the in-stream water quality criterion. However, instead of back-
calculating from the receiving water body to the discharge, the sediment models predict the
impact of the discharge to the downstream sediment. Therefore, the sediment quality models are
run iteratively with different effluent conditions to determine the wasteload allocations required
to meet the targets.
The permitting authority may monitor (or, in some cases, require the permittee to monitor) the
sediment deposition zone to ensure that the sediment quality-based effluent limits are adequately
protective. Sediment should also be monitored when the permit includes water quality-based
effluent limits based on meeting water column criteria for pollutants that tend to accumulate in
sediment. The expected rate of change in sediment conditions should be considered when
determining monitoring frequency. Factors to be considered in determining an appropriate
monitoring frequency include flow, scouring, and/or substrate materials. EPA recommends that
sediment monitoring (bioassays and chemical analyses) be conducted annually to reflect
potential changes in effluent quality over time. Where these data are collected by the permittee,
4-3
-------
they should be submitted at the time of the analysis, and should be appended to the application
for permit renewal.
4-4
-------
5. APPLICABILITY OF EQUILIBRIUM
PARTITIONING SEDIMENT GUIDELINES IN THE DREDGED
MATERIAL MANAGEMENT PROGRAM
Use of ESGs in the dredged material management programs will generally be limited to
information compiled as a part of evaluating the need for further testing under the Clean Water
Act (CWA) Section 404 program. Both the CWA Section 404 program and the Marine
Protection, Research, and Sanctuaries Act (MPRSA) Section 103 program employ biological
effects-based testing to evaluate proposed discharges of dredged material. These evaluations do
not place an emphasis on what chemical constituents are the source of potential toxicity or
bioaccumulation, but draw conclusions based on whether and to what extent any toxicity or
bioaccumulation occurs. For this reason, utility of ESGs in the dredged material management
programs will be very limited.
Section 404 of the CWA regulates the discharge of dredged material into "waters of the United
States," including all waters landward of the baseline of the territorial sea. The MPRSA
regulates the transportation of dredged material seaward of the baseline (in ocean waters) for the
purpose of disposal. Both programs use a tiered approach to evaluating proposed discharges,
with higher level tiers providing more information until it is sufficient to make a determination
on potential contamination. Although largely the same, the tiered structures vary to reflect
specific regulatory provisions of the two programs.
In 1991, EPA and the USAGE developed an Ocean Testing Manual (also referred to as the Green
Book) entitled "Evaluation of Dredged Material Proposed for Ocean Disposal - Testing Manuar
(U.S. EPA/USACE, 1991) for evaluation of potential contaminant-related impacts associated
with the discharge of dredged material in the ocean, under the MPRSA. In 1998, EPA and the
USAGE issued an Inland Testing Manual (ITM) entitled "Evaluation of Dredged Material
Proposed for Discharge in Waters of the U.S. - Testing Manuar (U.S. EPA/USACE, 1998)
containing the technical protocols for evaluating proposed discharges of dredged material
5-1
-------
associated with navigation dredging projects into waters of the U.S. (fresh, estuarine, and near-
coastal waters), under Section 404 of the CWA.
With respect to the ITM, existing information (including any available ESG values for dredged
material proposed for discharge) forms the basis for determining in Tier I whether a factual
determination of the material's potential contamination can be made (i.e., whether there is a
"reason to believe" the material is contaminated or not). If there is a "reason to believe," further
testing, including bioassays, is conducted. With respect to the Green Book, decisions are
typically based on certain bioassays. Because Tier I existing information usually contains
bioassay results, ESGs (sediment chemistry values) will be of little value in the Tier I evaluation
under the MPRSA. Therefore, use of ESGs in the dredged material management programs will
generally be limited to information compiled as a part of evaluating the need for further testing
under the Clean Water Act (CWA) Section 404 program.
Background
The U.S. Army Corps of Engineers (USAGE), the Federal agency designated to maintain
navigable waters, conducts a majority of the dredging projects and disposal under its
Congressionally authorized civil works program. The balance of the dredging and disposal is
conducted by a number of local public and private entities. In either case, the disposal is
subjected to a regulatory program administered jointly by the USAGE and EPA under Section
103 of the Marine Protection, Research, and Sanctuaries Act (MPRSA) for ocean disposal and
Section 404 of the Clean Water Act (CWA) for discharge at open water sites, confined disposal
facilities with return flow to waters of the U.S., and for beneficial uses.
EPA shares the responsibility of managing dredged material, principally in the development of
the environmental criteria and guidelines by which proposed discharges are evaluated and
disposal sites are selected, and in the exercise of its environmental oversight authority. Joint
EPA/USACE guidance manuals detailing the testing and analysis protocols for dredged material
disposal are well established. In addition, dredged material management activities are generally
5-2
-------
subject to National Environmental Policy Act (NEPA), as well as a number of other laws,
executive orders, and State and local regulations.
For more information on these testing regimes, please consult EPA's website at:
http://www.epa.gov/owow.
5-3
-------
THIS PAGE INTENTIONALLY LEFT BLANK
5-4
-------
6. INTEGRATION OF EQUILIBRIUM PARTITIONING SEDIMENT
GUIDELINES WITH THE SUPERFUND PROGRAM
6.1 INTRODUCTION
The purpose of the Superfund program is to address threats to human health or the environment
resulting from releases or potential releases of hazardous substances, pollutants or contaminants.
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
provides the Federal government the authority to respond or compel the responsible party to
respond to actual or threatened releases. By Executive Order, the President delegated primary
responsibility to EPA for managing these activities under the Superfund program.
CERCLA provides one of the most comprehensive authorities available to EPA to obtain
sediment clean-up, reimbursement of EPA clean-up costs, and compensation to natural resource
trustees for damage to natural resources. Local governments and States or Tribes typically
identify sites that should be evaluated for threats to public health and the environment. EPA
evaluates whether sites should be added to the National Priorities List (NPL) using the Hazard
Ranking System. Sites identified in the National Sediment Quality Survey and that are not
currently under the jurisdiction of another program (e.g., RCRA) may be appropriate for
evaluation under CERCLA. However, the decision on whether to evaluate a site for NPL listing
will be made separately by the Superfund program, based on a number of factors, including
human health and environmental threats, ongoing cleanup actions, and State or Tribal views.
Consistent with CERCLA and its implementing regulations, the National Oil and Hazardous
Substances Pollution Contingency Plan (NCP), EPA will seek to remediate contaminated
sediment sites to eliminate unacceptable risks to human health and the environment. EPA's
cleanup will normally be sufficient to support existing and designated uses of the contaminated
waterbody, including potential or designated uses of the sediment. Under CERCLA 121(b)(l),
remedial actions which permanently reduce the volume, toxicity, or mobility of hazardous
6-1
-------
substances, pollutants and contaminants through treatment as a principal element are preferred,
and under the NCP, EPA expects to treat principal threats posed by a site wherever practicable.
6.2 USING ESGs UNDER CERCLA
For sites listed on the NPL, EPA carries out an analysis of risks posed by contaminants at the site
to human health and the environment, examines the feasibility of various response action
alternatives to reduce risk, and then, using the nine criteria established in the National Oil and
Hazardous Substances Pollution Contingency Plan (40 CFR Part 300), selects an appropriate
remedy and cleanup levels. The Risk Assessment Guidance for Superfund (RAGS), (U.S. EPA,
1989a; U.S. EPA, 1989b; U.S. EPA 1997b) provides guidance for assessing human health and
environmental risks. Various EPA publications, including guidance in RAGS, Ecological
Updates, fact sheets, and OSWER Directive 9285.7-28 P (U.S. EPA, 1999b), are used to develop
assessments that are presented as a part of the Remedial Investigation/Feasibility Study (RI/FS)
of a CERCLA site. The process is designed for the purpose of assessing exposure routes from
contamination at CERCLA sites, including those involving sediments.
The ecological risk assessments performed in the Superfund program often include a screening
procedure to determine which, if any, of the contaminants found at a site are present in
concentrations that may be harmful to ecological receptors. In this step, the maximum measured
contaminant concentration at a site is compared to an ecotoxicologically-based benchmark; if the
concentration exceeds the benchmark, further assessment is warranted to determine the
ecological risk posed by the contaminant. This screening step is often useful at Superfund sites,
where a large number of contaminants may be detected. While exceeding the benchmark does
not indicate the level or type of risk involved, concentrations below the benchmark should not
result in significant adverse effects to ecological receptors when appropriately conservative
benchmarks are used (U.S. EPA, 1996a).
ESGs can be used to screen out contaminants or parts of a site from further consideration during
the screening level ecological risk assessment [Steps one and two (1997b)]. Contaminants that
6-2
-------
are below the ESG values would generally not be carried through as Contaminants of Potential
Concern (COPCs) into the baseline risk assessment. However, contaminant concentrations
which are above the ESG values warrant further investigation. This use of ESGs is consistent
with the use of "Ecotox Threshold (ET)" benchmark values previously put forth by Superfund
(U.S. EPA 1996a). Current ESGs are derived in the same manner as the "Alternative Method 1 -
Sediment Quality Benchmark" ETs described by U.S. EPA (1996a), but based on newer
information in some cases. Hence, the ESGs would replace these values. (Note however, that
the ESGs are presented on an organic carbon basis, whereas the ETs assumed a sediment organic
carbon fraction of one percent.)
EPA is currently developing an ESG for mixtures of polycyclic aromatic hydrocarbons (PAHs),
to replace previously proposed criteria for individual PAHs. Thus the "Preferred Method -
Sediment Quality Criteria" ETs for acenaphthene, fluoranthene and phenanthrene listed by U.S.
EPA (1996a) would be replaced by a PAH mixture ESG. It should be noted that ESGs are meant
to be used for screening purposes only; they are not cleanup levels. (Under CERCLA and the
NCP, cleanup levels are established after a site-specific analysis that considers and balances
several criteria.) The CERCLA program also intends to use the EPA-wide sediment testing
methods of the Tiered Testing Framework (discussed in U.S. EPA, 1998) in the risk assessment
process.
6-3
-------
THIS PAGE INTENTIONALLY LEFT BLANK
6-4
-------
7. INTEGRATION OF EQUILIBRIUM
PARTITIONING SEDIMENT GUIDELINES WITH THE RESOURCE
CONSERVATION AND RECOVERY ACT (RCRA) PROGRAM
7.1 INTRODUCTION
The Resource Conservation and Recovery Act (RCRA) is designed to ensure that wastes are
managed in an environmentally safe manner and that human health and the environment are
protected from the hazards posed by contamination at hazardous waste management facilities.
The most common way that the Resource Conservation and Recovery Act (RCRA) program
addresses contaminated sediments is during cleanup under the RCRA Corrective Action
program. RCRA Corrective Action is generally run by EPA authorized state programs.
Currently there are 33 states and territories authorized for Corrective Action. It should also be
noted that RCRA requirements for proper management of hazardous waste (e.g., treatment,
storage, disposal regulations) help prevent the contamination of sediments in the first instance.
Sediment contamination is frequently a concern at RCRA facilities. There are over 5,000
facilities that are subject to RCRA Corrective Action authority. According to a recent survey of
Corrective Action facilities which had either selected a final remedy or implemented interim
measures, over half of these facilities are located within one-quarter mile of a surface water body.
Therefore, sediment contamination as a result of releases from RCRA facilities is a potential
concern. (Citation, "A Study of the Implementation of the RCRA Corrective Action Program"
U.S. EPA, Office of Solid Waste, To be finalized in Summer 2000).
For contamination problems at RCRA sites, EPA, or the authorized state, carries out an
investigation of the threats posed by contaminants at the site to human health and the
environment. This initial investigation is similar to those conducted in the Superfund program.
Sediment problems may also be addressed under other RCRA remedial authorities, such as
RCRA §7003, which gives EPA authority to respond under certain circumstances where
7-1
-------
hazardous or solid wastes may present an imminent and substantial endangerment to human
health or the environment.
Like the Superfund program, sites are remediated under RCRA Corrective Action to support
current and reasonably anticipated uses. RCRA authority for Corrective Action is to clean up
releases from a specific facility, therefore it is less amenable to an area-wide approach than
Superfund. RCRA sediment cleanups may often best be addressed as part of a broader sediment
cleanup action.
7.2 USING ESGs UNDER RCRA CORRECTIVE ACTION
Similar to CERCLA, RCRA does assessments of sites, then, where necessary, more detailed
investigations, followed, where necessary, by remedy selection and remedy implementation. The
RCRA regulations allow significant flexibility in these procedures.
Like Superfund, EPA typically requires a site investigation when potential threats are identified.
Before cleanup decisions can be made at RCRA Corrective Action sites, some level of
characterization is necessary to ascertain the nature and extent of contamination at a site and to
gather information necessary to support selection and implementation of appropriate remedies.
In the CERCLA program, this step is referred to as the Remedial Investigation or RI; in the
RCRA program this step is referred to as the RCRA Facility Investigation, or RFI.
Carefully designed and implemented RFIs are critical to accurately characterize the nature,
extent, direction, rate, movement, and concentration of releases at a given facility. This
information is needed to determine potential risks to human health and the environment and
support development of corrective measures should they prove necessary. It can also be used to
eliminate, or screen, facilities which are shown not to present unacceptable risks from further
consideration. It is likely that if sediment contamination was suspected at a corrective action
facility, it is during the RFI that the sediment contamination would be investigated and
determined to be present or not. Similar to Superfund (see section 6.2), we recommend the use
7-2
-------
of ESGs to screen out threats. The RCRA Corrective Action program generally feels that ESGs
should be used for screening purposes only, and should not be used as final cleanup levels.
Although our Superfund and RCRA Corrective Action terminology for specific types of
investigations may differ, RCRA Corrective Action generally uses many of the same guidances
as Superfund. As described in the 1996 Advance Notice of Proposed Rulemaking (61 FR 19432,
May 1, 1996) site-specific risk assessments at RCRA facilities may, where appropriate, be
conducted in accordance with the Risk Assessment Guidance for Superfund (RAGS), (US EPA
1989a; US EPA 1989b; US EPA, 1997b) for assessing human health and environmental impacts.
The RCRA Corrective Action program intends in the near future to make an announcement
recommending the use of Ecological Risk Assessment and Risk Management Principles for
Superfund Sites (OSWER Directive 9285.7-28P) at appropriate RCRA Corrective Action sites.
EPA encourages Regional and State programs to use the ESG guidance in conducting site
assessments at sites that have sediment contamination. The RCRA Corrective Action program
plans to distribute the ESG guidance to Regional and State program offices for use in conducting
assessments and investigations at sites with sediment contamination.
7-3
-------
THIS PAGE INTENTIONALLY LEFT BLANK
7-4
-------
8. REFERENCES
Ankley, G.T. and M.K. Schubauer-Berigan. 1995. Background and overview of current
sediment toxicity identification evaluation procedures. Journal of Aquatic Ecosystem Health.
4:133-149.
Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid Reassessment
Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and
Fish. Second edition. EPA 841-B-99-002. .
U.S. EPA, Office of Water, Washington, DC.
Chapman, P. M. September 1992. Sediment Quality Triad Approach. In: Sediment
Classification Methods Compendium. EPA 823 -R-92-006. U.S. EPA, Office of Water,
Washington, DC.
Klemm, D.J., P. A. Lewis, F. Fulk, and J.M. Lazorchak. 1990. Macroinvertebrate Field and
Laboratory Methods for Evaluating the Biological Integrity of Surface Waters.
. EPA 600-4-90-030. U.S. EPA, Office
of Research and Development, Washington, DC.
Stephan, C.E., D.I. Mount, D.J. 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 (NTIS),
Springfield, VA, . phone 703/605-6000.
U.S. EPA. 1984. Technical Guidance Manual for Performing Wasteload Allocations. Book 2,
Streams and Rivers. EPA 440/4-84-022. U.S. EPA, Office of Water Regulations and Standards,
Washington, DC.
8-1
-------
U.S. EPA. 1986a. Technical Guidance Manual for Performing Wasteload Allocations. Book 4,
Lakes, Reservoirs, and Impoundments. EPA 440/4-87-002. U.S. EPA, Office of Water
Regulations and Standards, Washington, DC.
U.S. EPA. 1986b. Technical Guidance Manual for Performing Wasteload Allocations. Book 6,
Design Conditions. U.S. EPA, Office of Water Regulations and Standards, Washington, DC.
U.S. EPA. 1989a. Risk Assessment Guidance for Superfund, Volume I, Human Health
Evaluation Manual (Part A). Interim Final. EPA/540/1-89/002; NTIS PB90-155581.
. U.S. EPA, Office of Emergency and
Remedial Response, Washington, DC.
U.S. EPA. 1989b. Risk Assessment Guidance for Superfund, Volume II - Environmental
Evaluation Manual. Interim Final. EPA 540/1-89/001. U.S. EPA, Office of Emergency and
Remedial Response, Washington, DC.
U.S. EPA. 1990a. Evaluation of the Equilibrium Partitioning (EqP) Approach for Assessing
Sediment Quality. EPA-SAB-EPEC-90-006. U.S. EPA, Science Advisory Board, Sediment
Criteria Subcommittee of the Ecological Processes and Effects Committee, Washington, DC.
U.S. EPA. 1990b. Technical Guidance Manual for Performing Wasteload Allocations. Book 3,
Estuaries. U.S. EPA, Office of Water Regulations and Standards, Washington DC.
U.S. EPA. 1991a. Sediment Toxicity Identification Evaluation: Phase I (Characterization),
Phase II (Identification) and Phase III (Confirmation) Modifications of Effluent Procedures.
EPA/600/6-91/007. U.S. EPA, Office of Research and Development, Environmental Research
Laboratory, Duluth, MN.
8-2
-------
U.S. EPA. 1991b. Technical Support Document for Water Quality-based Toxics Control. EPA-
505-2-90-001 (PB91-127415). U.S. EPA, Office of Water, Office of Water Enforcement and
Permits and Office of Water Regulations and Standards, Washington, DC.
U.S. EPA. 1991c. Guidance for Water Quality-based Decisions: The TMDL Process. EPA
440/4-91-001. U.S. EPA, Office of Water, Washington, DC.
U.S. EPA. 1992. An SAB Report: Review of Sediment Criteria Development Methodology for
Non-ionic Organic Contaminants. EPA-SAB-EPEC-93-002. U.S. EPA, Science Advisory
Board, Sediment Quality Subcommittee of the Ecological Processes and Effects Committee,
Washington, DC.
U.S. EPA. 1994a. Methods for Assessing the Toxicity of Sediment-Associated Contaminants
with Estuarine and Marine Amphipods. EPA-600-R-94-025. U.S. EPA, Office of Research and
Development, Duluth, MM.
U.S. EPA. 1994b. Water Quality Standards Handbook, Second Edition. EPA-823-B-94-005a.
U.S. EPA, Office of Water, Office of Science and Technology, Washington, DC.
U.S. EPA. 1996a. Ecotox Thresholds. ECO Update, Intermittent Bulletin, Volume 3, Number
2. Publication 9345.0-12FSI; EPA 540/F-95/038; NTIS PB95-963324.
. U.S. EPA, Office of Solid Waste
and Emergency Response, Washington, DC.
U.S. EPA. 1996b. Corrective Action for Releases From Solid Waste Management Units at
Hazardous Waste Management Facilities: Advanced Notice of Proposed Rulemaking. (61 FR
19432) May 1, 1996.
U. S. EPA. 1997a. The Incidence and Severity of Sediment Contamination in the United States.
Volume 1: National Sediment Quality Survey (EPA-823-R-97-006); Volume 2: Data Summaries
8-3
-------
for Areas of Probable Concern (EPA-823-R-97-007); Volume 3: Sediment Contaminant Point
Source Inventory. (EPA-823-R-97-008). . U.S. EPA,
Office of Water, Office of Science and Technology, Washington, DC.
U.S. EPA. 1997b. Ecological Risk Assessment Guidance for Superfund: Process for Designing
and Conducting Ecological Risk Assessments. Interim Final. EPA 540-R-97-006. OSWER
Directive 9285.7-25. NTIS PB97-963211. . U.S. EPA, Office of Solid Waste and Emergency Response, Washington, DC.
U.S. EPA. 1998. EPA's Contaminated Sediment Management Strategy. EPA-823-R-98-001.
. U.S. EPA, Office of Water, Washington, DC.
U.S. EPA. 1999a. National Recommended Water Quality Criteria - Correction. EPA-822-Z-
99-001. . U.S. EPA, Office of Water, Washington, DC.
U.S. EPA. 1999b. Issuance of Final Guidance: Ecological Risk Assessment and Risk
Management Principles for Superfund Sites. OSWER Directive 9285.7-28 P.
. U.S. EPA, Office of Solid Waste
and Emergency Response, Washington, DC.
U.S. EPA. 2000a. Methods for Measuring the Toxicity and Bioaccumulation of Sediment-
associated Contaminants with Freshwater Invertebrates. Second edition. EPA-600-R-99-064.
U.S. EPA, Office of Research and Development and Office of Water, Washington, DC.
U.S. EPA. 2000b. Technical Basis for the Derivation of Equilibrium Partitioning Sediment
Guidelines (ESGs)for the Protection ofBenthic Organisms: Nonionic Organics. EPA-822-R-
00-001. U.S. EPA, Office of Science and Technology, Washington, DC.
-------
U.S. EPA. 2000c. Equilibrium Partitioning Sediment Guidelines (ESGs)for the Protection of
Benthic Organisms: Metal Mixtures (Cadmium, Copper, Lead, Nickel, Silver, and Zinc). EPA-
822-R-00-005. U.S. EPA, Office of Science and Technology, Washington, DC.
U.S. EPA. 2000d. Methods for the Derivation of Site-Specific Equilibrium Partitioning
Sediment Guidelines (ESGs) for the Protection of Benthic Organisms: Nonionic Organics.
EPA-822-R-00-002. U.S. EPA, Office of Science and Technology, Washington, DC.
U.S. EPA. 2000e. Equilibrium partitioning Sediment Guidelines (ESGs) for the Protection of
Benthic Organisms: Dieldrin. EPA-822-R-00-003. U.S. EPA, Office of Science and
Technology, Washington, DC.
U.S. EPA. 2000f. Equilibrium partitioning Sediment Guidelines (ESGs) for the Protection of
Benthic Organisms: Endrin. EPA-822-R-00-004. U.S. EPA, Office of Science and Technology,
Washington, DC.
U.S. EPA. 2000g. Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection of
Benthic Organisms: Nonionics Compendium. EPA-822-R-00-006. U.S. EPA, Office of Science
and Technology, Washington, DC.
U.S. EPA. 2000h. An SAB Report: Review of an Integrated Approach to Metals Assessment in
Surface Waters and Sediments. EPA-SAB-EPEC-00-005. .
U.S. EPA, Science Advisory Board, Ecological Processes and Effects Committee, Washington,
DC.
U.S. EPA/USACE. 1991. Evaluation of Dredged Material Proposed for Ocean Disposal -
Testing Manual (also referred to as the Ocean Testing Manual or the Green Book). EPA-503/8-
91/001. . U.S. EPA, Office of Water, and U.S. Army
Corps of Engineers, Washington, DC.
8-5
-------
U.S. EPA/US ACE. 1998. Evaluation of Dredged Material Proposed for Discharge in Waters of
the U.S. - Testing Manual (also referred to as the Inland Testing Manual or the ITM). EPA-823-
B-98-004. . U.S. EPA, Office of Water, and U.S. Army Corps of
Engineers, Washington, DC.
8-6
-------
APPENDIX A: AVAILABLE EQUILIBRIUM
PARTITIONING SEDIMENT GUIDELINES
METHODOLOGIES
Equilibrium Partitioning Sediment Guideline (ESG) derivation methods are available for the
following:
Non-ionic organic chemicals (U.S. EPA, 2000a)
Site-specific conditions (U.S. EPA, 2000b)
TIER 1 ESGs
EPA bases Tier 1 ESGs on a full minimum aquatic toxicity data set that EPA specifies for
development of Clean Water Act Section 304(a) water quality criteria (Stephan et al., 1985).
EPA has verified Tier 1 ESGs using whole sediment toxicity tests.
Tier 1 ESGs are available for the following chemicals:
Metal mixtures (cadmium, copper, lead, nickel, silver, and zinc) (U.S. EPA, 2000c)
Dieldrin (U.S. EPA, 2000d)
Endrin (U.S. EPA, 2000e)
A-l
-------
TIER 2 ESGs
EPA derives Tier 2 ESGs in the same manner as Tier 1 ESGs, but Tier 2 ESGs can be based on
less extensive data sets. For example, Tier 2 ESGs can be calculated with fewer water column
toxicity data; this is accounted for through an uncertainty factor which generally makes Tier 2
values more conservative. Additionally, EPA has not performed sediment verification tests for
all Tier 2 ESGs with whole sediment toxicity tests. EPA recommends that Tier 2 ESGs be
implemented in the same manner as Tier 1 ESGs, but with consideration that there is greater
conservatism associated with Tier 2 values.
Tier 2 ESGs are available for the following chemicals (U.S. EPA, 2000f):
Chemical Abstract
(CAS) Number
71432
319868
58899
92524
101553
85687
108907
333415
132649
95501
541731
106467
84742
84662
115297
959988
33213659
100414
Chemical Name
Benzene
Delta-BHC
Gamma-BHC, Lindane
Biphenyl
4-Bromophenyl phenyl ether
Butyl benzyl phthalate
Chlorobenzene
Diazinon
Dibenzofuran
1 ,2-Dichlorobenzene
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
Di-n-butyl phthalate
Diethyl phthalate
Endosulfan mixed isomers
Alpha-Endosulfan
Beta-Endosulfan
Ethylbenzene
A-2
-------
Chemical Abstract
(CAS) Number
67721
121755
72435
608935
79345
127184
56235
108883
8001352
75252
120821
71556
79016
108383
Chemical Name
Hexachloroethane
Malathion
Methoxychlor
Pentachlorobenzene
1 , 1 ,2,2-Tetrachloroethane
Tetrachloro ethene
Tetrachloromethane
Toluene
Toxaphene
Tribromomethane (Bromoform)
1, 2, 4-Trichlorobenzene
1,1, 1 -Trichloroethane
Trichloroethene
m-Xylene
REFERENCES
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.
U.S. EPA. 2000a. Technical Basis for the Derivation of Equilibrium Partitioning Sediment
Guidelines (ESGs) for the Protection ofBenthic Organisms: Nonionic Organics. EPA-822-R-
00-001. U.S. EPA, Office of Science and Technology, Washington, DC.
A-3
-------
U.S. EPA. 2000b. Methods for the Derivation of Site-Specific Equilibrium Partitioning
Sediment Guidelines (ESGs)for the Protection ofBenthic Organisms: Nonionic Organics. EPA-
822-R-00-002. U.S. EPA, Office of Science and Technology, Washington, DC.
U.S. EPA. 2000c. Equilibrium Partitioning Sediment Guidelines (ESGs)for the Protection of
Benthic Organisms: Metal Mixtures (Cadmium, Copper, Lead, Nickel, Silver, and Zinc). EPA-
822-R-00-005. U.S. EPA, Office of Science and Technology, Washington, DC.
U.S. EPA 2000d. Equilibrium partitioning Sediment Guidelines (ESGs)for the Protection of
Benthic Organisms: Dieldrin. EPA-822-R-00-003. U.S. EPA, Office of Science and
Technology, Washington, DC.
U.S. EPA 2000e. Equilibrium partitioning Sediment Guidelines (ESGs)for the Protection of
Benthic Organisms: Endrin. EPA-822-R-00-004. U.S. EPA, Office of Science and Technology,
Washington, DC.
U.S. EPA 2000f. Equilibrium Partitioning Sediment Guidelines (ESGs)for the Protection of
Benthic Organisms: Nonionics Compendium. EPA-822-R-00-006. U.S. EPA, Office of Science
and Technology, Washington, DC.
A-4
-------
APPENDIX B: SEDIMENT QUALITY MODELS
INTRODUCTION
There are a number of models that have been developed for water quality and sedimentation
loading by Federal, State, and private institutes. This appendix provides a description of the
available models and a brief discussion of how to select an appropriate model.
Originally, these water quality and sediment loading models were written with an emphasis on
the dynamics of chemical concentrations in the water column after discharge. More recent
versions simulate water column-sediment interactions, including settlement, resuspension, and
advection. The primary goal of such models is to estimate the areal extent and degree of
sediment contamination attributable to a discharge. This information can then be used to predict
where the discharge will cause an impact to receiving sediments. Additionally, several models
are discussed in this appendix that may be used to predict sediment deposition, resuspension, and
scour. While not specifically designed for contaminant fate and transport modeling, these
models have utility in defining sediment yields within specific design criteria, and have utility in
predicting total loads to a sediment deposition zone (SDZ).
DATA NEEDS
Models that simulate SDZ dynamics and sediment quality are generally more complex and
require more extensive input data than water mixing zone models. Required inputs include data
describing water body hydrodynamic characteristics, point and nonpoint discharges, background
sediment load and contaminant levels, temperature, bathymetry, grain size distribution, organic
carbon content of suspended and bed sediments, partitioning coefficients for the contaminants of
concern, and additional data (Table B-l).
B-l
-------
Table B-l. Data needs for SDZ modeling
Background Receiving Water Data
Seasonal flow rates (speed and volume, cumulative probability distribution)
Background sediment load
Background pollutant loads
Effluent Data
Effluent flow rates
Effluent pollutant load
Density and temperature
Effluent paniculate load
Receiving Water Data
Density gradients
Ambient current speed and direction
Sedimentation rates
SDZ baseline contaminant levels
Physical boundaries of the water body system
Temperature
Bathymetry
Bed sediment composition
Sediment grain size distribution
Sediment organic carbon content
Solid/liquid phase partitioning coefficients for pollutants of concern
Where known or available, information on the location, settling rates (kg/sediment/day), and
existing pollutant loads in the SDZ are useful to calibrate models. States and Tribes may
consider requiring sediment collection and analyses by dischargers prior to setting SDZ limits.
MODEL DESCRIPTIONS
The EFDC/HEM3D model (Hamrick, 1992, 1996) is single source code three-dimensional
modeling system having hydrodynamic, water quality-eutrophication, sediment transport and
toxic contaminant transport components transparently linked together. The model can execute in
a fully coupled model simultaneously simulating hydrodynamics and sediment and contaminant
transport or in a transport only mode using saved hydrodynamic transport information. The
model also includes an embedded near field mixing zone model which has the capability of
interfacing with the far field transport. A water quality-eutrophication model is also incorporated
into EFDC (Environmental Fluid Dynamics Computer Code) (Park, et al., 1995; Hamrick and
Wu, 1996). The EFDC model also incorporates the capability to provide hydrodynamic and
B-2
-------
sediment transport information to the WASP4 and WASPS models. The public domain model is
well documented and the source code is available. The EFDC model was originally developed at
the Virginia Institute of Marine Science (VIMS). The VIMS version without the full sediment
and toxic contaminant simulation capability is referred to as the three-dimensional
hydrodynamic-eutrophication model (HEM3D). The version described above is available from
the model's principal author.
The EFDC Advanced Modeling Toolkit is currently under development with release scheduled
for late 2000. The principle components of the toolkit are a grid generator to set up the physical
domain of the model, a graphical user interface (GUI) to the EFDC model, and a post-processor
to view model output. The grid generator will import shoreline and bathymetry files in a variety
of formats, convert shoreline and bathymetry to a Cartesian grid scheme, save the physical
domain and grid data to a relational data base management system, and export the physical data
to text files required by the EFDC Fortran code.
The CORMIX models (Jirka and Akar, 1991; Jirka and Doneker, 1991) are the most widely used
near-field mixing zone models for water quality studies. The CORMIX 1 and CORMIX2
packages can be used to analyze buoyant submerged discharges from single-port outfalls and
multi-port diffusers, respectively, into a flowing, density stratified ambient environment. The
expert system approach implemented in CORMIX 1 selects from 35 possible classes, the solution
class most representative of the specified situation, and provides the user with graphical and
tabular summaries of the solution results which are used to define the mixing zone. The expert
system approach implemented in CORMDC2 can select for 24 possible classes, the solution class
most representative of the specified situation and providing graphical tabular summaries of the
solution results for dilution and near-field mixing zone definition. The user interface for both
models is in the form of an interactive expert system. Since the models do not explicitly
represent settling and dissolved-sorbed phase partitioning, settling effects must be approximated
by first using the model to calculate spatial concentration field neglecting particulate settling.
Next, the distribution of settling material and sorbed contaminants on the bed is determined
based on the horizontal settling projection of the concentration field onto the sediment bed.
B-3
-------
Water Quality Analysis Simulation Program, WASPS is a generalized framework for modeling
contaminant fate and transport in surface waters. WASP and associated sub-models all have the
same general data requirements dealing with water body hydrogeometry, advective and
dispersive flows, settling and resuspension rates, boundary concentrations, pollutant loadings,
and initial conditions. The body of water to be simulated must be divided into a series of
computational elements or segments. Segment volumes, connectivity, and type (surface water,
subsurface water, surface benthic, subsurface benthic) must be specified.
Structurally, the WASPS program includes six mechanisms for describing transport. These
"transport fields" consist of advection and dispersion in the water column; advection and
dispersion in the interstitial water; settling, resuspension, and sedimentation of up to three classes
of solids; and evaporation or precipitation. Each variable is advected and dispersed among water
segments, and exchanged with surficial benthic segments by diffusive mixing. Sorbed or
particulate fractions may settle through water column segments and deposit to or erode from
surficial benthic segments. Within the bed, dissolved variables may migrate downward or
upward through percolation and interstitial water diffusion. Sorbed variables may migrate
downward or upward through net sedimentation or erosion.
TOXI5 is a WASP5-based sub-model that simulates the transport and transformation of one to
three chemicals and one to three types of particulate material. TOXI5 treats sediment as a
conservative constituent that is advected and dispersed among water segments, that settles to and
erodes from benthic segments, and that moves between benthic segments through net
sedimentation or erosion. Settling, deposition, resuspension, and burial velocities are not
calculated, but must be input by the user.
HEC-6 is a riverine sediment transport model built and maintained by the U.S. Army Corps of
Engineers Hydrologic Engineering Center. While not specifically designed to model fate and
transport of sediment contaminants, it is a one-dimensional sediment transport model that can be
used to predict deposition and scour in rivers and reservoirs. HEC-6 is designed primarily to
-------
simulate transport of non-cohesive sediments in systems that frequently experience
resuspension/erosion, rather than deposition of cohesive sediments.
The HSCTM-2D model (Hayter et al, 1998) and TSEDH (Shrestha and Orlob, 1996) are two-
dimensional, in the horizontal plane, finite element based sediment-contaminant transport models
based on the SEDH sediment transport model (Ariathuri and Krone, 1976). The HSCTM-2D
model consists of two modules, one for hydrodynamic modeling (HYDRO2D) and the other for
sediment and inorganic contaminant transport modeling (CS2D). HYDRO2D solves the
equations of motion and continuity for nodal depth-averaged horizontal velocity components and
flow depths. The effects of bottom, internal and surface shear stresses, horizontal salinity
gradients, and the Coriolis force are represented in the equations of motion. CS2D solves the
advection-dispersion equation for nodal vertically-integrated concentrations of suspended
sediment, dissolved and sorbed contaminants, and bed surface elevations. Both models simulate
cohesive and noncohesive sediment transport. Horizontal water column transport includes
advection and shear dispersion. The TSEDH model utilizes equilibrium partitioning and a first
order decay formulation for biological uptake of heavy metals. The HSCTM-2D model
represents interactions between dissolved and particulate contaminants and sediments by
simulating the processes of adsorption and desorption of contaminants, utilizing equilibrium
partitioning, to and from sediments, respectively.
The SEDZL model is a two-dimensional, vertically-averaged hydrodynamic and sediment
transport model that uses finite difference procedures for computational simulations (Ziegler and
Lick, 1986; QEA, 1999). A three-dimensional version of the model (ECOM-SED) incorporated
SEDZL sediment dynamics into the ECOM hydrodynamic model (Blumberg and Mellor, 1987).
The two-dimensional version of SEDZL is suitable for use on vertically well-mixed rivers, lakes,
estuaries and coastal regions. SEDZL simulates the transport of two sediment classes: cohesive
and non-cohesive. For cohesive sediment transport, the model uses a concentration and ambient-
flow-dependent settling formulation to approximate aggregation and disaggregation processes.
The effects of near-bed turbulence on deposition fluxes are incorporated through use of
probability of deposition functions for both sediment classes. Cohesive resuspension is
B-5
-------
simulated using the Lick equation, which predicts resuspension potential as a function of bed
shear stress and bed consolidation. Non-cohesive suspended load transport is simulated using
the van Rijn formulations in conjunction with a bed armoring algorithm. Complete details of the
sediment bed dynamics are presented in QEA (1999). The model has been applied to various
aquatic systems, including: Fox River, Wisconsin (Gailani et al., 1991); Lake Erie (Lick et al.,
1994); Pawtuxet River, Rhode Island (Ziegler and Nesbitt, 1994); Watts Bar Reservoir,
Tennessee (Ziegler and Nesbitt, 1995); and Upper Hudson River (QEA, 1999). The different
studies documented reasonable agreement between model predictions and field observations,
with model results ranging from fair to excellent, depending upon the amount of site-specific
data available to parameterize and calibrate the model. SEDZL is no longer publicly available.
The SERATRA model (Onishi, 1977; Onishi and Wise, 1982) is a two-dimensional, in the
vertical plane sediment and toxic contaminant transport model for rivers and narrow reservoirs,
developed by a Pacific Northwest National Laboratory. The model requires external
specification of the net longitudinal flow and internally computes water column transport by
longitudinal and vertical advection, settling and vertical diffusion. Sediment and sorbed
contaminant exchange with the bed by erosion and deposition flux is calculated in response to
the bed shear stress. The model has been applied to simulate radionuclide transport in the
Columbia River (Onishi and Wise, 1982).
The CE-QUAL-W2 model (Cole and Buchak, 1994) is a two-dimensional in the vertical plane
coupled hydrodynamic and water quality model using a finite difference solution scheme. The
eutrophication component of the model is similar to WASPS in many respects. The model was
designed for rivers, narrow reservoirs and narrow estuaries. Predictive temperature and salinity
transport are also included in the model. Relevant water column state variables include: single
algae class represented in carbon equivalent units, ammonia, nitrite-nitrate, orthophosphate,
labile dissolved organic material, refractory organic material, detritus, carbonaceous biochemical
oxygen demand, and dissolved oxygen. Organic carbon in the sediment bed cannot be
determined.
B-6
-------
Two additional models that can be used to determine total bedloads, deposition and scour output
include the Precipitation-Runoff Modeling System maintained by the U.S. Geological Survey,
and the Watershed Modeling System co-developed and maintained by the U.S. Army Corps of
Engineers and Brigham Young University.
MODEL SELECTION
Within the present state of model development, the primary factors to consider in selecting a
model to simulate SDZ location, sediment and contaminant characteristics, and interactions with
surface waters are:
Environmental setting (water body type)
Model class (near field vs. far field, one dimensional vs. two dimensional, etc.)
Practicability/implementability
These three model selection factors are addressed below.
Environmental Setting. Models should be evaluated for their applicability to the following major
water body types. Table B-2 rates the applicability of the models under consideration to these
water body types.
Low variability rivers or streams, characterized by depth-uniform, one-dimensional flow,
minimal vertical or lateral diffusion, and no reverse flow (due to tides, winds or currents).
High variability rivers or streams, characterized by temporal and spatial variability in flow
and sediment and contaminant loading.
B-7
-------
High trapping efficiency reservoirs and lakes, characterized by two-dimensional horizontally-
averaged flows, significant vertical mixing, possible reverse flows, and high sediment
trapping efficiency with little resuspension of deposited sediments.
One-dimensional estuaries and tidal rivers, which tend to be shallow, narrow, and cross-
sectionally mixed, with unsteady hydrodynamics but slow temporal variability in sediment
and contaminant transport.
Wide, shallow lakes, reservoirs or estuaries, characterized by two-dimensional vertically-
averaged flows, complete vertical mixing, significant tide and wind effects, and possible flow
reversal.
Narrow, stratified estuaries, lakes or reservoirs, characterized by lateral mixing, well-defined
longitudinal flow directions, and significant spatial variability on dissolved and suspended
material distribution in the longitudinal vertical plane.
Geometrically and dynamically complex water bodies, including lakes, rivers, reservoirs,
estuaries, and coastal regions that often have recognizable subregions exhibiting the above
characteristics, thus requiring a three-dimensional approach.
Model Class. The available models can be grouped into the following classes, and should be
selected based on the physical conditions to be analyzed and the type of output desired.
Near-field versus far-field models. Near-field models focus on the immediate area around
the discharge, where the plume is not fully dispersed by background flow. All other models
are far-field and focus on the region beyond the zone of initial dilution in which advection of
the plume is controlled by background field flow.
B-8
-------
Steady-state versus continuous or dynamic models. Steady-state models address only
equilibrium conditions. Continuous or dynamic models can simulate variable conditions
over time, although equilibrium may be reached if external variables remain constant.
Number of dimensions simulated by the model; can be one, two or three. One-dimensional
models assume one-dimensional flow and that conditions do not vary in the second or third
dimensions. Two-dimensional models can be two-dimensional in the horizontal plane
(assumes no variability in the vertical plane) or vertical plane (assumes no variability in the
horizontal plane). Three-dimensional models are best-suited to the most complex physical
and environmental conditions.
Practicability/implementability. The following criteria can be used to assess how practical it
may be to apply a model in a particular situation.
Track record. How good is the model's track record in previous applications?
Degree of empiricism. Includes the degree to which model parameters influence the
performance of the model in accurately answering the question posed.
Level of effort involved in setup and application of the model.
Field data requirements for model calibration and verification.
Expertise required to apply the model and interpret model results.
B-9
-------
DO
Table B-2. Model Applicability for Predicting Sediment Bed Concentration Patterns
Applicability:
H - High
M - Moderate
L -Low
NEAR-FIELD:
CORMIX*
EFDC'
SEDZL'
FAR-FIELD:
WASP5
SEDZL
CE-QUAL-W2
SED2D
TSEDH
SERATRA
EFDC
WATER BODY TYPE
Low
Variability
Streams
and Rivers
H
H
H
H
H
H
H
H
H
H
High
Variability
Streams and
Rivers
H
H
H
H
H
H
H
H
M
H
High Trapping
Efficiency
Reservoirs
and Lakes
H
H
H
H
M
M
M
M
M
H
1 -Dimensional
Tidal
Estuaries
H
H
H
H.
H
H
H
H
M
H
2-Dimensional
(Wide, Shallow,
Vertically-Averaged)
Estuaries and Lakes
H
H
H
H
H
L
H
H
L
H
2-Dimensional
(Narrow, Stratified
Horizontally-Averaged)
Estuaries and Lakes
H
H
H
H
L
L
L
L
M
H
3-Dimensional
(Geometrically and
Dynamically
Complex)
Water Bodies
H
H
H
H
L
L
L
L
L
H
With further modification.
-------
REFERENCES
Ariathurai, R., and R.B. Krone. 1976. Finite element model for cohesive sediment transport.
Journal of Hydraulic Division ofASCE, 102:323-338.
Blumberg, A.F., and G.L. Mellor. 1987. A description of a three-dimensional coastal ocean
circulation model. In: Three-Dimensional Coastal Ocean Models, Coastal and Estuarine
Science, Vol. 4 (Heaps, N.S., editor). American Geophysical Union.
Cole, T.M., and E.M. Buchak. 1994. CE-QUAL-W2: A two-dimensional laterally averaged,
hydrodynamic and water quality model, Version 2.0. Report ITL-93-7. U.S. Army Corps of
Engineers, Waterway Experiment Station, Vicksburg, MS.
Gallani, J., C.K. Ziegler, and W. Lick. 1991. Transport of suspended solids in the lower Fox
River. Journal of Great Lakes Research, 17:479-494.
Hamrick, J.M. 1992. A Three-Dimensional Environmental Fluid Dynamics Computer Code
(EFDC): Theoretical and Computational Aspects. Special Report 317. The College of William
and Mary, Virginia Institute of Marine Science.
Hamrick, J.M. 1997. A theoretical description of sediment and contaminant transport
formulations used in the EFDC model. Technical memorandum TT-EFDC-97-1, Terra Tech,
Inc., Fairfax, VA.
Hamrick, J.M., and T.S. Wu. 1996. Computational design and optimization of the
EFDC/HEM3D surface water hydrodynamic and eutrophication models. Computational
Methods for Next Generation Environmental Models (G. Delich, editor). Society of Industrial
and Applied Mathematics, Philadelphia.
B-ll
-------
Hayter, E.J., M. Bergs, R. Gu, S.C. McCutcheon, S.J. Smith, and H.J. Whiteley. 1998.
"HSCTM-2D, A Finite Element Model for Depth-Averaged Hydrodynamics, Sediment and
Contaminant Transport," Technical Report, EPA National Exposure Research Laboratory,
Ecosystems Research Division, Athens, Georgia.
Jirka, G.H., and PJ. Akar. 1991. Hydrodynamic classification of submerged multiport-diffuser
discharges. Journal of Hydraulic Engineering, 117:1113-1128.
Jirka, G.H., and R.L. Doneker. 1991. Hydrodynamic classification of submerged single-port
discharges. Journal of Hydraulic Engineering, 117:1113-1128.
Lick, W., J. Lick, and C.K. Ziegler. 1994. The resuspension and transport of fine-grained
sediments in Lake Erie. Journal of Great Lakes Research, 20:599-612.
Onishi, Y. 1977. Mathematical simulation of sediment and radionuclide transport in the
Columbia River. BNWL-2228. Battelle Pacific Northwest Laboratories, Richland, WA.
Onishi, Y., and S.E. Wise. 1982. Mathematical model SERATRA, for sediment-contaminant
transport in rivers and its application to pesticide transport in Four Mile and Wolf Creeks in
Iowa. EPA/600/3-82/045. U.S. EPA, Athens, GA.
Park, K., A.Y. Kuo, J. Shen, and J.M. Hamrick. 1995. A three-dimensional hydrodynamic-
eutrophication model (HEM3D); description of water quality and sediment processes submodels.
Special Report 327. The College of William and Mary, Virginia Institute of Marine Science.
Quantitative Environmental Analysis, 1999. PCBs in the Upper Hudson River, Volume 2, A
Model of PCB Fate, Transport and Bioaccumulation, QEA report, May 1999.
Shrestha, P. A., and G.T. Orlob. 196. Multiphase distribution of cohesive sediments and heavy
metals in estuarine systems. Journal of Environmental Engineering, 122:730-740.
B-12
-------
Ziegler, C.K., and W. Lick. 1988. The transport of fine-grained sediment in shallow waters.
Environmental Geology Water Science, 11:123-132.
Ziegler, C.K., and B. Nesbitt. 1994. Fine-grained sediment transport in Pawruxet River, Rhode
Island. Journal of Hydraulic Engineering, 120:561-576.
Ziegler, C.K., and B. Nesbitt. 1995. Long-term simulation of fine-grained sediment transport in
large reservoirs. Journal of Hydraulic Engineering, 121:773-781.
B-13
-------
THIS PAGE INTENTIONALLY LEFT BLANK
B-14
------- |