Chapter 3 - Water Quality Criteria 

CHAPTER 3 

WATER QUALITY CRITERIA 

The term “water quality criteria” has two different 

definitions under the Clean Water Act (CWA). 

Under section 304(a), EPA publishes water 

quality criteria that consist of scientific 

information regarding concentrations of specific 

chemicals or levels of parameters in water that 

protect aquatic life and human health (see section 

3.1 of this Handbook). The States may use these 

contents as the basis for developing enforceable 

water quality standards. Water quality criteria are 

also elements of State water quality standards 

adopted under section 303(c) of the CWA (see 

sections 3.2 through 3.6 of this Handbook). 

States are required to adopt water quality criteria 

that will protect the designated use(s) of a water 

body. These criteria must be based on sound 

scientific rationale and must contain sufficient 

parameters or constituents to protect the 

designated use. 

3.1 EPA Section 304(a) Guidance 

EPA and a predecessor agency have produced a 

series of scientific water quality criteria guidance 

documents. Early Federal efforts were the 

“Green Book” (FWPCA, 1968) and the “Red 

Book” (USEPA, 1976). EPA also sponsored a 

contract effort that resulted in the “Blue Book” 

(NAS/NAE, 1973). These early efforts were 

premised on the use of literature reviews and the 

collective scientific judgment of Agency and 

advisory panels. However, when faced with the 

need to develop criteria for human health as well 

as aquatic life, the Agency determined that new 

procedures were necessary. Continued reliance 

solely on existing scientific literature was deemed 

inadequate because essential information was not 

available for many pollutants. EPA scientists 

developed formal methodologies for establishing 

scientifically defensible criteria. These were 

subjected to review by the Agency’s Science 

Advisory Board of outside experts and the public. 

This effort culminated on November 28, 1980, 

when the Agency published criteria development 

guidelines for aquatic life and for human health, 

along with criteria for 64 toxic pollutants 

(USEPA, 1980a,b). Since that initial publication, 

the aquatic life methodology was amended 

(Appendix H), and addition al criteria were 

proposed for public comment and finalized as 

Agency criteria guidance. EPA summarized the 

available criteria information in the “Gold Book” 

(USEPA, 1986a), which is updated from time to 

time. However. the individual criteria documents 

(see Appendix I). as updated, are the official 

guidance documents. 

EPA’s criteria documents provide a 

comprehensive toxicological evaluation of each 

chemical. For toxic pollutants, the documents 

tabulate the relevant acute and chronic toxicity 

information for aquatic life and derive the criteria 

maximum concentrations (acute criteria) and 

criteria continuous concentrations (chronic 

criteria) that the Agency recommends to protect 

aquatic life resources. The methodologies for 

these processes are described in Appendices H 

and J and outlined in sections 3.1.2 and 3.1.3 of 

this Handbook. 

3.1.1 State Use of EPA Criteria Documents 

EPA’s water quality criteria documents are 

available to assist States in: 

• adopting water quality standards that include 

appropriate numeric water quality criteria; 

• interpreting existing water quality standards 

that include narrative “no toxics in toxic 

amounts” criteria; 

(8/15/94) 3-1 
Water Quality Standards Handbook - Second Edition 

• making listing decisions under section 304(1) 

of the CWA; 

• writing water quality-based NPDES permits 

and individual control strategies; and 

• providing certification under section 401 of 

the CWA for any Federal permit or license 

(e.g., EPA-issued NPDES permits, CWA 

section 404 permits, or Federal Energy 

Regulatory Commission licenses). 

In these situations, States have primary authority 

to determine the appropriate level to protect 

human health or welfare (in accordance with 

section 303(c)(2) of the CWA) for each water 

body. However, under the Clean Water Act, 

EPA must also review and approve State water 

quality standards; section 304(1) listing decisions 

and draft and final State-issued individual control 

strategies; and in States where EPA writes 

NPDES permits, EPA must develop appropriate 

water quality-based permit limitations. The States 

and EPA therefore have a strong interest in 

assuring that the decisions are legally defensible, 

are based on the best information available, and 

are subject to full and meaningful public comment 

and participation. It is very important that each 

decision be supported by an adequate record. 

Such a record is critical to meaningful comment, 

EPA’s review of the State’s decision, and any 

subsequent administrative or judicial review. 

Any human health criterion for a toxicant is based 

on at least three interrelated considerations: 

• cancer potency or systemic toxicity. 

• exposure. and 

• risk characterization. 

States may make their own judgments on each of 

these factors within reasonable scientific bounds, 

but documentation to support their judgments, 

when different from EPA’s recommendation, must 

be clear and in the public record. If a State relies 

on EPA’s section 304(a) criteria document (or 

other EPA documents), the State may reference 

and rely on the data in these documents and need 

not create duplicative or new material for 

inclusion in their records. However, where sitespecific issues arise or the State decides to adopt 

an approach to any one of these three factors that 

differs from the approach in EPA’s criteria 

document, the State must explain its reasons in a 

manner sufficient for a reviewer to determine that 

the approach chosen is based on sound scientific 

rationale (40 CFR 131.11 (b)). 

3.1.2 Criteria for Aquatic Life Protection 

The development of national numerical water 

quality criteria for the protection of aquatic 

organisms is a complex process that uses 

information from many areas of aquatic 

toxicology. (See Appendix H for a detailed 

discussion of this process.) After a decision is 

made that a national criterion is needed for a 

particular material, all available information 

concerning toxicity to, and bioaccumuiation by. 

aquatic organisms is collected and reviewed for 

acceptability. If enough acceptable data for 48- to 

96-hour toxicity tests on aquatic plants and 

animals are available, they are used to derive the 

acute criterion. If sufficient data on the ratio of 

acute to chronic toxicity concentrations are 

available, they are used to derive the chronic or 

long-term exposure criteria. If justified, one or 

both of the criteria may be related to other water 

quality characteristics, such as pH, temperature, 

or hardness. Separate criteria are developed for 

fresh and salt waters. 

The Water Quality Standards Regulation allows 

States to develop numerical criteria or modify 

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Chapter 3 - Wuter Qualify Criren’n 

EPA’s recommended criteria to account for 

site-specific or other scientifically defensible 

factors. Guidance on modifying national criteria 

is found in sections 3.6 and 3.7. When a 

criterion must be developed for a chemical for 

which a national criterion has not been 

established, the regulatory authority should refer 

to the EPA guidelines (Appendix H). 

Magnitude for Aquatic Life Criteria 

Water quality criteria for aquatic life contain two 

expressions of allowable magnitude: a criterion 

maximum concentration (CMC) to protect against 

acute (short-term) effects; and a criterion 

continuous concentration (CCC) to protect against 

chronic (long-term) effects. EPA derives acute 

criteria from 48- to 96-hour tests of lethality or 

immobilization. EPA derives chronic criteria 

from longer term (often greater than 28-day) tests 

that measure survival, growth, or reproduction. 

Where appropriate, the calculated criteria may be 

lowered to be protective ofcomercially or 

recreationally important species. 

Duration for Aquatic Life Criteria 

The quality of an ambient water typically varies in 

response to variations of effluent quality, stream 

flow, and other factors. Organisms in the 

receiving water are not experiencing constant, 

steady exposure but rather are experiencing 

fluctuating exposures, including periods of high 

concentrations, which may have adverse effects. 

Thus, EPA’s criteria indicate a time period over 

which exposure is to be averaged, as well as an 

upper limit on the average concentration, thereby 

limiting the duration of exposure to elevated 

concentrations. For acute criteria, EPA 

recommends an averaging period of 1 hour. That 

is, to protect against acute effects, the l-hour 

average exposure should not exceed the CMC. 

For chronic criteria, EPA recommends an 

averaging period of 4 days. That is, the 4-day 

average exposure should not exceed the CCC. 

Frequency for Aquatic Life Criteria 

To predict or ascertain the attainment of criteria, 

it is necessary to specify the allowable frequency 

for exceeding the criteria. This is because it is 

statistically impossible to project that criteria will 

never be exceeded. As ecological communities 

are naturally subjected to a series of stresses, the 

allowable frequency of pollutant stress may be set 

at a value that does not significantly increase the 

frequency or severity of all stresses combined. 

EPA recommends an average frequency for 

excursions of both acute and chronic criteria not 

to exceed once in 3 years. In all cases, the 

recommended frequency applies to actual ambient 

concentrations, and excludes the influence of 

measurement imprecision. EPA established its 

recommended frequency as part of its guidelines 

for deriving criteria (Appendix H). EPA selected 

the 3-year average frequency of criteria 

exceedence with the intent of providing for 

ecological recovery from a variety of severe 

stresses. This return interval is roughly 

equivalent to a 7410 design flow condition. 

Because of the nature of the ecological recovery 

studies available, the severity of criteria 

excursions could not be rigorously related to the 

resulting ecological impacts. Nevertheless, EPA 

derives its criteria intending that a single marginal 

criteria excursion (i.e., a slight excursion over a 

l-hour period for acute or over a 4-day period for 

chronic) would require little or no time for 

recovery. If the frequency of marginal criteria 

excursions is not high, it can be shown that the 

frequency of severe stresses, requiring measurable 

recovery periods, would be extremely small. 

EPA thus expects the 3-year return interval to 

provide a very high degree of protection. 

3.1.3 Criteria for Human Health Protection 

This section reviews EPA’s procedures used to 

develop assessments of human health effects in 

developing water quality criteria and reference 

ambient concentrations. A more complete human 

health effects discussion is included in the 

Guidelines und Merhtnioiog~ Used in Ihe 

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Water Quality Standards Handbook - Second Edition 

Preparation of Healrh Eflecfs Assessmens Chapters 

of the Consenr Decree Wur4r Docwnents 

(Appendix J). The procedures contained in this 

document are used in the development and 

updating of EPA water quality criteria and may be 

used in updating State criteria and in developing 

State criteria for those pollutants lacking EPA 

human health criteria. The procedures may also 

be applied as site-specific interpretations of 

narrative standards and as a basis for permit limits 

under 40 CFR 122.44 (d)( l)(vi). 

Magnitude and Duration 

Water quality criteria for human health contain 

only a single expression of allowable magnitude; 

a criterion concentration generally to protect 

against long-term (chronic) human health effects. 

Currently, national policy and prevailing opinion 

in the expert community establish that the 

duration for human health criteria for carcinogens 

should be derived assuming lifetime exposure, 

taken to be a 70-year time period. The duration 

of exposure assumed in deriving criteria for 

noncarcinogens is more complicated owing to a 

wide variety of endpoints: some developmental 

(and thus age-specific and perhaps genderspecific), some lifetime. and some, such as 

organoleptic effects. not duration-related at all. 

Thus, appropriate durations depend on the 

individual noncarcinogenic pollutants and the 

endpoints or adverse effects being considered. 

Human Exposure Considerations 

A complete human exposure evaluation for toxic 

polIutants of concern for bioaccumulation would 

encompass not only estimates of exposures due to 

fish consumption but also exposure from 

background concentrations and other exposure 

routes, The more important of these include 

recreational and occupational contact, dietary 

intake from other than fish, intake from air 

inhalation, and drinking water consumption. For 

section 304(a) criteria de\,elopment, EPA typically 

considers only exposures to a pollutant that occur 

through the ingestion of water and contaminated 

fish and shellfish. This is the exposure default 

assumption, although the human health guidelines 

provide for considering other sources where data 

are available (see 45 F.R. 79354). Thus the 

criteria are based on an assessment of risks 

related to the surface water exposure route only 

(57 F.R. 60862-j). 

The consumption of contaminated fish tissue is of 

serious concern because the presence of even 

extremely low ambient concentrations of 

bioaccumulative pollutants (sublethal to aquatic 

life) in surface waters can result in residue 

concentrations in fish tissue that can pose a human 

health risk. Other exposure route information 

should be considered and incorporated in human 

exposure evaluations to the extent available. 

Levels of actual human exposures from 

consuming contaminated fish vary depending upon 

a number of case-specific consumption factors. 

These factors include type of fish species 

consumed, type of fish tissue consumed, tissue 

lipid content, consumption rate and pattern. and 

food preparation practices. In addition, depending 

on the spatial variability in the fishery area, the 

behavior of the fish species, and the point of 

application of the criterion. the average exposure 

of fish may be only a small fraction of the 

expected exposure at the point of application of 

the criterion. If an effluent attracts fish. the 

average exposure might be greater than the 

expected exposure. 

With shellfish, such as oysters, snails, and 

mussels. whole-body tissue consumption 

commonly occurs, whereas with fish, muscle 

tissue and roe are most commonly eaten. This 

difference in the types of tissues consumed has 

implications for the amount of available 

bioaccumulative contaminants likely to be 

ingested. Whole-body shellfish consumption 

presumably means ingestion of the entire burden 

of bioaccumulative contaminants. However, with 

most fish. selective cleaning and removal of 

internal organs, and sometimes body fat as well, 

from edible tissues, may result in removal of 

much of the lipid material in which 

bioaccurnulative contaminants tend to concentrate. 

3-4 (8115194) 
Chapter 3 - Wnm Qudity Crircria 

Fish Consumption Values 

EPA’s human health criteria have assumed a 

human body weight of 70 kg and the consumption 

of 6.5 g of fish and shellfish per day. Based on 

data collected in 1973-74, the national per capita 

consumption of freshwater and estuarine fish was 

estimated to average 6.5 g/day. Per capita 

consumption of all seafood (including marine 

species) was estimated to average 14.3 g/day. 

The 95th percentile for consumption of all seafood 

by individuals over a period of 1 month was 

estimated to be 42 g/day. The mean lipid content 

of fish and shellfish tissue consumed in this study 

was estimated to be 3.0 percent (USEPA, 198Oc). 

Currently, four levels of fish and shellfish 

consumption are provided in EPA guidance 

(USEPA, 1991a): 

l 6.5 g/day to represent an estimate of average 

consumption of fish and shellfish from 

estuarine and freshwaters by the entire U.S. 

population. This consumption level is based 

on the average of both consumers and 

nonconsumers of. 

l 20 g/day to represent an estimate of the 

average consumption of fish and shellfish 

from marine, estuarine, and freshwaters by 

the IJ.S. population. This average 

consumption level also includes both 

consumers and nonconsumers of, 

l 165 g/day to represent consumption of fish 

and shellfish from marine, estuarine, and 

freshwaters by the 99.9th percentile of the 

U.S. population consuming the most fish or 

seafood. 

l 180 g/day to represent a “reasonable worst 

case” based on the assumption that some 

individuals would consume fishand shellfish 

at a rate equal to the combined consumption 

of red meat, poultry, fish, and shellfish in 

the llnited States. 

EPA is currently updating the national estuarine 

and freshwater fish and shellfish consumption 

default values and will provide a range of 

recommended national consumption values. This 

range will include: 

l mean values appropriate to the population at 

large; and 

l values appropriate for those individuals who 

consume a relatively large proportion of fish 

and shellfish in their diets (maximally 

exposed individuals). 

Many States use EPA’s 6.5 g/day consumption 

value. However, some States use the abovementioned 20 g/day value and, for saltwaters, 

37 g/day. In general, EPA recommends that the 

consumption values used in deriving criteria from 

the formulas in this chapter reflect the most 

current, relevant, and/or site-specific information 

available. 

Bioaccumulat ion Consider-at ions 

The ratio of the contaminant concentrations in fish 

tissue versus that in water is termed either the 

bioconcentration factor (BCF) or the 

bioaccumulation factor (BAF). Rioconcentration 

is defined as involving contaminant uptake from 

water only (not from food). The bioaccumulation 

factor (RAF) is defined similarly to the BCF 

except that it includes contaminant uptake from 

both water and food. Under laboratory 

conditions, measurements of tissue/water 

partitioning are generally considered to involve 

uptake from water only. On the other hand, both 

processes are likely to apply in the field since the 

entire food chain is exposed. 

The BAF/BCF ratio ranges from 1 to 100. with 

the highest ratios applying to organisms in higher 

trophic levels, and to chemicals with logarithm of 

the octanol-water partitioning coefficient (log P) 

clo.sc to 6.5. 

Bioaccumulation considerations are integrated into 

the criteria equations by using food chain 

(8/15!94) 3-s 
multipliers (FMs) in conjunction with the BCF. 

The bioaccurnulation and bioconcentration factors 

for a chemical are related as follows: 

BAF = Fhl x BCF 

By incorporating the FM and BCF terms into the 

criteria equations, bioaccumulation can be 

addressed. 

In Table 3-1, FM values derived from the work 

of Thomann (1987, 1989) are listed according to 

log P value and trophic level of the organism. 

For chemicals with log P values greater than 

about 7. there is additional uncertainty regarding 

the degree of bioaccumulation, but generally, 

trophic level effects appear to decrease due to 

slow transport kinetics of these chemicals in fish, 

the growth rate of the fish, and the chemical’s 

relatively low bioavailability. Trophic level 4 

organisms are typically the most desirable species 

for sport fishing and, thcrcfore, FMs for trophic 

level 4 should generally be used in the equations 

for calculating criteria. In those \crv rare 

situations where only lower trophic level 

organisms are found, e.g., possibly oyster beds, 

an FM for a lower trophic level might be 

considered. 

Measured BAFs (especially for those chemicals 

with log P values above 6.5) reported in the 

literature should be used when available. To use 

experimentally measured BAFs in calculating the 

criterion, the (FM x BCF) term is replaced by the 

BAF in the equations in the following section, 

Relatively few BAFs have been measured 

accurately and reported, and their application to 

sites other than the specific ecosystem where they 

were developed is problematic and subject to 

uncertainty. The option is also available to 

develop BAFs experimentally, but this will be 

extremely resource intensive if done on a sitespecific basis with all the necessary experimental 

and quality controls. 

Trophic Levels 

____________________------------------------------------- _-_---_ 

Loi% p 2 3 4 

________________________________________---------------------- 

3.5 1.0 I .o 1.0 

3.6 1.0 I .o 1 .o 

3.7 1.0 1 .o 1.0 

3.8 1.0 1.0 1.0 

3.9 1.0 1 .o 1.0 

4.0 1.1 1 .o 1.0 

4.1 1.1 1.1 1.1 

4.2 1.1 1.1 1.1 

4.3 1.1 1.1 1.1 

4.4 1’ .& 1.1 1.1 

4.5 13 .& 1.2 1.2 

4.6 1.2 1.3 1.3 

4.7 1.3 1.4 1.4 

4.8 1.4 1.5 1.6 

4.9 1.5 1.8 2.0 

5.0 1.6 2.1 2.6 

5.1 1.7 2.5 3.2 

5.2 1.9 3.0 4.3 

5.3 2.2 3.7 5.8 

5.4 2.4 4.6 8.0 

5.5 2.8 5.9 11 

5.6 3.3 7.5 16 

5.7 3.9 9.8 u 

5.8 4.6 13 33 

5.9 5.6 17 47 

6.0 6.8 21 67 

6.1 8.2 25 75 

6.2 10 29 84 

6.3 13 34 92 

6.4 15 39 98 

6.5 19 45 100 

26.5 19.2’ 4s 100’ 

----------------------_--_--_--------------------------------- 

* These recommended FMs are conservative estimates; 

FMs for log P values greater than 6.5 may range from 

the vdiues given to a low as 0.1 for contaminants with 

very low b~oavailabihty. 

Table 3-1. Estimated Food Chain 

hlultipliers (FMs) 

Updating Human Health Criteria Using 

IRIS 

EPA recommends that States use the most current 

risk information in the process of updating human 

3-6 (8115194) 
Chapter 3 - Water Qualify Criteria 

health criteria. The Integrated Risk Information 

System (IRIS) (Barns and Dourson, 1988; 

Appendix N) is an electronic data base of the 

USEPA that provides chemical-specific risk 

information on the relationship between chemical 

exposure and estimated human health effects. Risk 

assessment information contained in IRIS, except 

as specifically noted, has been reviewed and 

agreed upon by an interdisciplinary group of 

scientists representing various Program Offices 

within the Agency and represent an Agency-wide 

consensus. Risk assessment information and 

values are updated on a monthly basis and are 

approved for Agency-wide use. IRIS is intended 

to make risk assessment information readily 

available to those individuals who must perform 

risk assessments and also to increase consistency 

among risk assessment/risk management 

decisions. 

IRIS contains two types of quantitative risks 

values: the oral Reference Dose (RfD) and the 

carcinogenic potency estimate or slope factor. 

The RfD (formerly known as the acceptable daily 

intake or ADI) is the human health hazard 

assessment for noncarcinogenic (target organ) 

effects. The carcinogenic potency estimate 

(formerly known as q,*) represents the upper 

bound cancer-causing potential resulting from 

lifetime exposure to a substance. The RfD or the 

oral carcinogenic potency estimate is used in the 

derivation of EPA human health criteria. 

EPA periodically updates risk assessment 

information, including RfDs, cancer potency 

estimates, and related information on contaminant 

effects, and reports the current information on 

IRIS. Since IRIS contains the Agency’s most 

recent quantitative risk assessment values, current 

IRIS values should be used by States in updating 

or developing new human health criteria. This 

means that the 1980 human health criteria should 

be updated with the latest IRIS values. The 

procedure for deriving an updated human health 

water quality criterion would require inserting the 

current Rfd or carcinogenic potency estimate on 

IRIS into the equations in Exhibit 3.1 or 3.2, as 

appropriate. 

Evdua!e oUw 

aourceeddrtC 

e.g., FDA action 

kvela, MClA, fbk 

auoument fi8h 

amauumgti 

adviaofy levela 

FigUIT! 3-l. Procedure for determining an 

updated criterion using IRIS 

data. 

Figure 3-l shows the procedure for determining 

an updated criterion using IRIS data. If a 

chemical has both carcinogenic and noncarcinogenic effects, i.e., both a cancer potency 

estimate and a RfD, both criteria should be 

calculated. The most stringent criterion applies. 

Caiculoting Criteria for Non-carcinogens 

The RfD is an estimate of the daily exposure to 

the human population that is likely to be without 

appreciable risk of causing deleterious effects 

during a lifetime. The RfD is expressed in units 

of mg toxicant per kg human body weight per 

hY* 

RfDs are derived from the “no-observed-adverseeffect level” (NOAEL) or the “lowest-observedadverse-effect level” (LOAEL) identified from 

chronic or subchronic human epidemiology studies 

or animal exposure studies. (Note: “LOAEL” 

(S/15/94) 3-7 
Water CJuaiity SM Handbook - Second Edition 

and “NOAEL” refer to animal and human 

toxicology and are therefore distinct from the 

atpli3tiC toxicity terms “no-observed-effect 

concentration” (NOEC) and “lowest-observedeffect concentration” (LOEC) .) Uncertainty 

factors are then applied to the NOAEL or LOAEL 

to account for uncertainties in the data associated 

with variability among individuals, extrapolation 

from nonhuman test species to humans, data on 

other than long-term exposures, and the use of a 

LOAEL (USEPA, 1988a). An additional 

uncertainty factor may be applied to account for 

significant weakness or gaps in the database. 

The RfD is a threshold below which systemic 

toxic effects are unlikely to occur. While 

exposures above the RfD increase the probability 

of adverse effmts, they do not produce a certainty 

of adverse effects. Similarly, while exposure at 

or below the RfD reduces the probability, it does 

not guarantee the absence of effects in all persons. 

The RfDs contained in IRIS are values that 

represent EPA’s consensus (and have uncertainty 

spanning perhaps an order of magnitude). This 

means an RfD of 1 .O mg/kg/day could range from 

0.3 to 3.0 mg/kg/day. 

For noncafcinogenic effects, an updated criterion 

can be derived using the equation in Exhibit 3-l. 

If the receiving water body is not used as a 

drinking water source, the factor WI can be 

deleted. Where dietary and/or inhalation 

exposure values are unknown, these factors may 

be deleted from the above calculation. 

Galcuhting Criteria for Carcinogens 

Any human health criterion for a carcinogen is 

based on at least three interrelated considerations: 

cancer potency, exposure, and risk 

characterization. When developing State criteria, 

States may make their own judgments on each of 

these factors within reasonable scientific bounds, 

but documentation to support their judgments 

must be clear and in the public record. 

Maximum protection of human health from the 

potential effects of exposure to carcinogens 

through the consumption of contaminated fish 

and/or other aquatic life would require a criterion 

of zero. The zero level is based upon the 

assumption of non-threshold effects (i.e., no safe 

level exists below which any increase in exposure 

does not result in an increased risk of cancer) for 

carcinogens. However, because a publicly 

acceptable policy for safety does not require the 

absence of all risk, a numerical estimate of 

pollutant concentration (in pgll) which 

corresponds to a given level of risk for a 

population of a specified size is selected instead. 

A cancer risk level is defined as the number of 

new cancers that may result in a population of 

specified size due to an increase in exposure 

(e.g., lo4 risk level = 1 additional cancer in a 

population of 1 million). Cancer risk is calculated 

by multiplying the experimentally derived cancer 

potency estimate by the concentration of the 

chemical in the fish and the average daily i.uman 

consumption of contaminated fish. The risk for a 

specified population (e.g., 1 million people or 10. 

“) is then calculated by dividing the risk level by 

the specific cancer risk. EPA’s ambient water 

quality criteria documents provide risk levels 

ranging from IO5 to 10’ as examples. 

The cancer potency estimate, or slope factor 

(formerly known as the q,*), is derived using 

animal studies. High-dose exposures are 

extrapolated to low-dose concentrations and 

adjusted to a lifetime exposure period through the 

use of a linearized multistage model. The model 

calculates the upper 95 percent confidence limit of 

the slope of a straight line which the model 

postulates to occur at low doses. When based on 

human (epidemiological) data, the slope factor is 

based on the observed increase in cancer risk and 

is not extrapolated. For deriving criteria for 

carcinogens, the oral cancer potency estimates or 

slope factors from IRIS are used. 

It is important to note that cancer potency factors 

may overestimate or underestimate the actual risk. 

Such potency estimates are subject to great 

uncertainty because of two primary factors: 

3-8 (8/15/94) 
Chapter 3 - Water Quality Ckiwri’o 

C(mg/l) = J&fDxWTl m lDT+INlxWT 

WI+fFCxLxF’MxBCF”J 

where: 

C 

IN 

WI 

FC 

L 

FM 

BCF 

updated water quality criterion (mg/l) 

oral reference dose (mg toxicant& human My weight/day) 

weight of an average human adult (70 kg) 

dietary exposure (other than fish) (mg toxicantikg body human 

weight/day) 

inhalation exposure (mg toxicant/kg body human weight/day) 

average human adult water intake (2 l/day) 

daily fish consumption (kg fish/day) 

ratio of lipid fraction of fish tissue consumed to 3% 

food chain multiplier (from Table 3-1) 

bioconcentration factor (mg toxicant@ fish divided by mg toxicant/L 

water) for fish with 3% lipid content 

Exhibit 3-1. Equation for Deriving Human Health Criteria Based on Noncarcinogenic Effects 

l adequacy of the cancer data base (i.e., 

human vs. animal data); and 

l limited information regarding the mechanism 

of cancer causation. 

Risk levels of IO”, 10d, and 10.’ are often used 

by States as minimal risk levels in interpreting 

their standards. EPA considers risks to be 

additive, i.e., the risk from individual chemicals 

is not necessarily the overall risk from exposure 

to water. For example, an individual risk level of 

lo4 may yield a higher overall risk level if 

multiple carcinogenic chemicals are present. 

For carcinogenic effects, the criterion can be 

determined by using the equation in Exhibit 3-2. 

If the receiving water body is not designated as a 

drinking water source, the factor WI can be 

deleted. 

Den’ving Quadative Risk Assessments in 

the Absence of IRIS Values 

The Rfl)s or cancer potency estimates comprise 

the existing dose-response factors for developing 

criteria. When IRIS data are unavailable, 

quantitative risk level information may be 

developed according to a State’s own procedures. 

Some States have established their own 

procedures whereby dose-response factors can be 

developed based upon extrapolation of acute 

and/or chronic animal data to concentrations of 

exposure protective of fish consumption by 

(8/15/94) 3-9 
Water Quality Standards Handbook - Second Edition 

where: 

C 

RL 

91 * 

wl 

FC 

L 

FM 

BCF 

q*[WI+FCxLx(F’MxBCE)] 

updated water quality criterion (mg/l) 

risk level (10’) where x is usually in the range of 4 to 6 

weight of an average human adult (70 kg) 

carcinogenic potency factor (kg day/mg) 

average human adult water intake (2 l/day) 

daily fish consumption (kg fish/day) 

ratio of lipid fraction of fish tissue consumed to 3% assumed by EPA 

food chain multiplier (from Table 3-l) 

bioconcentration factor (mg toxicant/kg fish divided by mg toxicant/L 

water) for fish with 3% lipid content 

Exhibit 3-2. Equation for Deriving Human Health Criteria Based on Carcinogenic Effects 

humans. 

I 3.2 Relationship of Section 304(a) Criteria 

to State Designated Uses 

The section 304(a)( 1) criteria published by EPA 

from time to time can be used to support the 

designated uses found in State standards. The 

following sections briefly discuss the relationship 

between certain criteria and individual use 

classifications. Additional information on this 

subject also can be found in the “Green Book” 

(FWPCA, 1968); the “Blue Book” (NAUNAE, 

1973); the “Red Rook” USEPA, 1976); the EPA 

Water Quality Criteria Documem (see Appendix 

I); the”Gold Rook” (USEPA, 198&t); and future 

EPA section 304(a)(l) water quality criteria 

publications. 

Where a water body is designated for more than 

one use, criteria necessary to protect the most 

sensitive use must be applied. The following four 

sections discuss the major types of use categories. 

3.2.1 Recreation 

Recreational uses of water include activities such 

as swimming, wading, boating, and fishing. 

Often insufficient data exist on the human health 

effects of physical and chemical pollutants, 

including most toxics, to make a determination of 

criteria for recreational uses. However, as a 

general guideline, recreational waters that contain 

chemicals in concentrations toxic or othenvise 

harmful to man if ingested, or irritating to the 

skin or mucous membranes of the human body 

3-10 (8/15/94) 
Chuvrer 3 - Water Oualitv Criteria 

upon brief immersion, should be avoided. The 

section 304(a)(l) human health effects criteria 

based on direct human drinking water intake and 

fish consumption might provide useful guidance in 

these circumstances. Also, section 304(a)(l) 

criteria based on human health effects may be 

used to support this designated use where fishing 

is included in the State definition of “recreation.” 

In this latter situation, only the portion of the 

criterion based on fish consumption should be 

Used. Section 304(a)(l) criteria to protect 

recreational uses are also available for certain 

physical, microbiological, and narrative “free 

from” aesthetic criteria. 

Research regarding bacteriological indicators has 

resulted in EPA recommending that States use 

Ercherichia coli or enterococci as indicators of 

recreational water quality (USEPA, 1986b) rather 

than fecal coliform because of the better 

correlation with gastroenteritis in swimmers. 

The “Green Book” and “Blue Book” provide 

additional information on protecting recreational 

uses such as pH criteria to prevent eye irritation 

and microbiological criteria based on aesthetic 

considerations. 

3.2.2 Aquatic Life 

The section 304(a)(l) criteria for aquatic life 

should be used directly to support this designated 

If subcategories of this use are adopted 

ye?;., to differentiate between coldwater and 

warmwater fisheries), then appropriate criteria 

should be set to reflect the varying needs of such 

subcategories. 

3.2.3 Agricultural and Industrial Uses 

The “Green Book” (FWPCA, 1968) and “Blue 

Book” (NASINAE, 1973) provide some 

information on protecting agricultural and 

industrial uses. Section 304(a)(l) criteria for 

protecting these uses have not been specifically 

developed for numerous parameters pertaining to 

these uses, including most toxics. 

Where criteria have not been specifically 

developed for these uses, the criteria developed 

for human health and aquatic life are usually 

sufficiently stringent to protect these uses. States 

may also establish criteria specifically designed to 

protect these uses. 

3.2.4 Public Water Supply 

The drinking water exposure component of the 

section 304(a){ 1) criteria based on human health 

effects can apply directly to this use classification. 

The criteria also may be appropriately modified 

depending upon whether the specific water supply 

system falls within the auspices of the Safe 

Drinking Water Act’s (SDWA) regulatory control 

and the typz and level of treatment imposed upon 

the supply before delivery to the consumer. The 

SDWA controls the presence of contaminants in 

finished (“at-the-tap”) drinking water. 

A brief description of relevant sections of the 

SDWA is necessary to explain how the Act will 

work in conjunction with section 304(a)( 1) criteria 

in protecting human health from the effects of 

toxics due to consumption of water. Pursuant to 

section 1412 of the SDWA, EPA has promulgated 

“National Primary Drinking Water Standards” for 

certain radionuclide, microbiological, organic, and 

inorganic substances. These standards establish 

maximum contaminant levels (MCLs), which 

specify the maximum permissible level of a 

contaminant in water that may be delivered to a 

user of a public water system now defined as 

serving a minimum of 25 people. MCLs are 

established based on consideration of a range of 

factors including not only the health effects of the 

contaminants but also treatment capability, 

monitoring availability, and costs. Under section 

1401(l)(D)(i) of the SDWA, EPA is also allowed 

to establish the minimum quality criteria for water 

that may be taken into a public water supply 

system. 

Section 304(a)(l) criteria provide estimates of 

pollutant concentrations protective of human 

health, but do not consider treatment technology, 

costs, and other feasibility factors. The section 
War Quality Straduds HandhA - Scumd Edition 

304(a)(l) criteria also include fish 

bioaccumulation and consumption factors in 

addition to direct human drinking water intake. 

These numbers were not developed to serve as 

“at-the-tap” drinking water standards, and they 

have no regulatory significance under the SDWA. 

Drinking water standards are established based on 

considerations, including technological and 

economic feasibility, not relevant to section 

304(a)( 1) criteria. Section 304(a)(l) criteria are 

more analogous to the maximum contaminant 

level goals (MCLGs) (previously known as 

RMCLs) under section I4 12(b)( l)(B) of the 

SDWA in which, based upon a report from the 

National Academy of Sciences, the Administrator 

should set target levels for contaminants in 

drinking water at which “no known or anticipated 

adverse effects occur and which allow an adequate 

margin of safety. ” MCLGs do not take treatment, 

cost, and other feasibility factors into 

consideration. Section 304(a)(l) criteria are, in 

concept, related to the health-based goals specified 

in the MCLGs. 

MCLs of the SDWA, where they exist, control 

toxic chemicals in finished drinking water. 

However, because of variations in treatment, 

ambient water criteria may be used by the States 

as a supplement to SDWA regulations. When 

setting water quality criteria for public water 

supplies, States have the option of applying 

MCLs, section 304(a)(l) human health effects 

criteria, modified section 304(a)(l) criteria, or 

controls more stringent than these three to protect 

against the effects of contaminants by ingestion 

from drinking water. 

For treated drinking water supplies serving 25 

people or greater, States must control 

contaminants down to levels at least as stringent 

as MCLs (where they exist for the pollutants of 

concern) in the finished drinking water. 

However, States also have the options to control 

toxics in the ambient water by choosing section 

304(a)( 1) criteria, adjusted section 304(a)( 1) 

criteria resulting from the reduction of the direct 

drinking water exposure component in the criteria 

calculation to the extent that the treatment process 

reduces the level of pollutants, or a more stringent 

contaminant level than the former three options. 

cl 

3.3 State Criteria Requirements 

Section I3 1.1 l(a)( 1) of the Regulation requires 

States to adopt water quality criteria to protect the 

designated use(s). The State criteria must be 

based on sound scientific rationale and must 

contain sufficient parameters or constituents to 

protect the designated use(s). For waters with 

multiple use designations, the criteria must 

support the most sensitive use. 

In section 13 1.11, States are encouraged to adopt 

both numeric and narrative criteria. Aquatic life 

criteria should protect against both short-term 

(acute) and long-term (chronic) effects. Numeric 

criteria are particularly important where the cause 

of toxicity is known or for protection against 

pollutants with potential human health impacts or 

bioaccumulation potential. Numeric water quality 

criteria may also be the best way to address 

nonpoint source pollution problems. Narrative 

criteria can be the basis for limiting toxicity in 

waste discharges where a specific pollutant can be 

identified as causing or contributing to the toxicity 

but where there are no numeric criteria in the 

State standards. Narrative criteria also can be 

used where toxicity cannot be traced to a 

particular pollutant. 

Section 13 1.1 l(a)(2) requires States to develop 

implementation procedures which explain how the 

State will ensure that narrative toxics criteria are 

met. 

To more fully protect aquatic habitats, it is EPA’s 

policy that States fully integrate chemical-specific, 

whole-effluent, and biological assessment 

approaches in State water quality programs (see 

Appendix R). Specifically, each of these three 

methods can provide a valid assessment of m 

wmenf of designated aquatic life uses but can 

rarely demonstrate use attainment separately. 

Therefore, EPA supports a policy of independent 

application of these three water quality assessment 

3-12 (lv15194) 
Chapter 3 - Water Quality Crirm’a 

approaches. Independent application means that 

the validity of the results of any one of the 

approaches does not depend on confirmation by 

one or both of the other methods. This policy is 

based on the unique attributes, limitations, and 

program applications of each of the three 

approaches. Each method alone can provide valid 

and independently sufficient evidence of nonattainment of water quality standards, irrespective 

of any evidence, or lack thereof, derived from the 

other two approaches. The failure of one method 

to confirm impacts identified by another method 

does not negate the results of the initial 

assessment. 

It is also EPA’s policy that States should 

designate aquatic life uses that appropriately 

address biological integrity and adopt biological 

criteria necessary to protect those uses (see 

section 3.5.3 and Appendices C, K, and R). 

cl 

3.4 Criteria for Toxicants 

Applicable requirements for State adoption of 

water quality criteria for toxicants vary depending 

upon the toxicant. The reason for this is that the 

1983 Water Quality Standards Regulation 

(Appendix A) and the Water Quality Act of 1987 

which amended the Clean Water Act (Public Law 

100-4) include more specific requirements for the 

particular toxicants listed pursuant to CWA 

section 307(a). For regulatory purposes, EPA has 

translated the 65 compounds and families of 

compounds listed pursuant to section 307(a) into 

126 more specific substances, which EPA refers 

to as “priority toxic pollutants.” The 126 priority 

toxic pollutants are listed in the WQS regulation 

and in Appendix P of this Handbook. Because of 

the more specific requirements for priority toxic 

pollutants* it is convenient to organize the 

requirements applicable to State adoption of 

criteria for toxicants into three categories: 

a requirements applicable to priority toxic 

pollutants that have been the subject of CWA 

section 304(a)(l) criteria guidance (see 

section 3.4.1); 

l requirements applicable to priority toxic 

pollutants that have not been the subject of 

CWA section 304(a)( 1) criteria guidance (see 

section 3.4.1); and 

0 requirements applicable to all other toxicants 

(e.g., non-conventional pollutants like 

ammonia and chlorine) (see section 3.4.2). 

3.4.1 Priority Toxic Pollutant Criteria 

The criteria requirements applicable to priority 

toxic pollutants (i.e., the first two categories 

above) are specified in CWA section 303(c)(2)(B). 

Section 303(c)(2)(B), as added by the Water 

Quality Act of 1987, provides that: 

Whenever a State reviews water quality 

standards pursuant to paragraph (1) of 

this subsection, or revises or adopts 

new standards pursuant to this 

paragraph 1 such State shall adopt 

criteria for all toxic pollutants listed 

pursuant to section 307(a)( 1) of this Act 

for which criteria have been published 

under section 304(a), the discharge or 

presence of which in the affected 

waters could reasonably be expected to 

interfere with those designated uses 

adopted by the State, as necessary to 

support such designated uses. Such 

criteria shall be specific numerical 

criteria for such toxic pollutants. 

Where such numerical criteria are not 

available, whenever a State reviews 

water quality standards pursuant to 

paragraph (I), or revises or adopts new 

standards pursuant to this paragraph, 

such State shall adopt criteria based on 

biological monitoring or assessment 

methods consistent with information 

published pursuant to section 304(a)(8). 

Nothing in this section shall be 

construed to limit or delay the use of 

effluent limitations or other permit 

conditions based on or involving 

biological monitoring or assessment 

(8/15/94) 3-13 
Water Oualitv Stan&& Handbook - Second Edition 

methods or previously adopted 

numerical criteria. 

EPA, in devising guidance for section 

303(c)(2)(B), attempted to provide States with the 

maximum flexibility that complied with the 

express statutory language but also with the 

overriding congressional objective: prompt 

adoption and implementation of numeric toxics 

criteria. EPA believed that flexibility was 

important so that each State could comply with 

section 303(c)(2)(B) and to the extent possible, 

accommodate its existing water quality standards 

regulatory approach. 

General Requirements 

To carry out the requirements of section 

303(c)(2)(B), whenever a State revises its water 

quality standards, it must review all available 

information and data to first determine whether 

the discharge or the presence of a toxic pollutant 

is interfering with or is likely to interfere with the 

attainment of the designated uses of any water 

body segment. 

If the data indicate that it is reasonable to expect 

the toxic pollutant to interfere with the use, or it 

actually is interfering with the use, then the State 

must adopt a numeric limit for the specific 

pollutant. If a State is unsure whether a toxic 

pollutant is interfering with, or is likely to 

interfere with, the designated use and therefore is 

unsure that control of the pollutant is necessary to 

support the designated use, the State should 

undertake to develop sufficient information upon 

which to make such a determination. Presence of 

facilities that manufacture or use the section 

307(a) toxic pollutants or other information 

indicating that such pollutants are discharged or 

will be discharged strongly suggests that such 

pollutants could be interfering with attaining 

designated uses. If a State expects the pollutant 

not to interfere with the designated use, then 

section 303(1)(2)(B) does not require a numeric 

standard for that pollutant. 

Section 303(c)(2)(B) addresses only pollutants 

listed as “toxic” pursuant to section 307(a) of the 

Act, which are codified at 40 CFR 131.36(b). 

The section 307(a) list contains 65 compounds and 

families of compounds, which potentially include 

thousands of specific compounds. The Agency 

has interpreted that list to include 126 “priority” 

toxic pollutants for regulatory purposes. 

Reference in this guidance to toxic pollutants or 

section 307(a) toxic pollutants refers to the 126 

priority toxic pollutants unless otherwise noted. 

Both the list of priority toxic pollutants and 

recommended criteria levels are subject to change. 

The national criteria recommendations published 

by EPA under section 304(a) (see section 3.1, 

above) of the Act include values for both acute 

and chronic aquatic life protection; only chronic 

criteria recommendations have been established to 

3-14 (8115194) 
Chapter 3 - Water Qualitv Criteria 

protect human health. To comply with the 

statute, a State needs to adopt aquatic life and 

human health criteria where necessary to support 

the appropriate designated uses. Criteria for the 

protection of human health are needed for water 

bodies designated for public water supply. When 

fish ingestion is considered an important activity, 

then the human health-related water quality 

criteria recommendation developed under section 

304(a) of the CWA should be used; that is, the 

portion of the criteria recommendation based on 

fish consumption. For those pollutants designated 

as carcinogens, the recommendation for a human 

health criterion is generally more stringent than 

the aquatic life criterion for the same pollutant. 

In contrast, the aquatic life criteria 

recommendations for noncarcinogens are 

generally more stringent than the human health 

recommendations. When a State adopts a human 

health criterion for a carcinogen, the State needs 

to select a risk level. EPA has estimated risk 

levels of 10-5, 10d6, and IO-’ in its criteria 

documents under one set of exposure assumptions. 

However, the State is not limited to choosing 

among the risk levels published in the section 

304(a) criteria documents, nor is the State limited 

to the base case exposure assumptions; it must 

choose the risk level for its conditions and explain 

its rationale. 

EPA generally regulates pollutants treated as 

carcinogens in the range of lob to lo4 to protect 

average exposed individuals and more highly 

exposed populations. However, if a State selects 

a criterion that represents an upper bound risk 

level less protective than I in 100,000 (e.g., lo’), 

the State needs to have substantial support in the 

record for this level. This support focuses on two 

distinct issues. First, the record must include 

documentation that the decision maker considered 

the public interest of the State in selecting the risk 

level, including documentation of public 

participation in the decision making process as 

required by the Water Quality Standards 

Regulation at 40 CFR 13 1.20(b). Second, the 

record must include an analysis showing that the 

risk level selected, when combined with other risk 

assessment variables, is a balanced and reasonable 

estimate of actual risk posed, based on the best 

and most representative information available. 

The importance of the estimated actual risk 

increases as the degree of conservatism in the 

selected risk level diminishes. EPA carefully 

evaluates all assumptions used by a State if the 

State chose to alter any one of the standard EPA 

assumption values (57 F.R. 60864, December 22, 

1993). 

EPA does not intend to propose changes to the 

current requirements regarding the bases on which 

a State can adopt numeric criteria (40 CFR 

13 I, I I (b)( 1)). Under EPA’s regulation, in 

addition to basing numeric criteria on EPA’s 

section 304(a) criteria documents, States may also 

base numeric criteria on site-specific 

determinations or other scientifically defensible 

methods. 

EPA expects each State to comply with the neu 

statutory requirements in any section 303(c) water 

quality standards review initiated after enactment 

of the Water Quality Act of 1987. The structure 

of section 303(c) is to require States to review 

their water quality standards at least once each 3 

year period. Section 303(c)(2)(B) instructs States 

to include reviews for toxics criteria whenever 

they initiate a triennial review. Therefore, even 

if a State has complied with section 303(c)(2)(B), 

the State must review its standards each triennium 

to ensure that section 303(c)(2)(B) requirements 

continue to be met, considering that EPA may 

have published additional section 304(a) criteria 

documents and that the State will have new 

information on existing water quality and on 

pollution sources. 

It should be noted that nothing in the Act or in the 

Water Quality Standards Regulation restricfs the 

right of a State to adopt numeric criteria for any 

pollutant not listed pursuant to section 307(a)(l), 

and that such criteria may he expressed as 

concentration limits for an individual pollutant or 

for a toxicity parameter itself as measured by 

whole-effluent toxicity testing. However, neither 

numeric toxic criteria nor whole-effluent toxicity 

(S/15/94) 3-15 
Watu Quality Stamhrds Handbook - Secmd Edition 

should be used as a surrogate for, or to supersede 

the other. 

State Options 

States may meet the requirements of CWA section 

303(c)(2)(B) by choosing one of three 

scientifically and technically sound options (or 

some combination thereof): 

(1) 

(2) 

(3) 

Adopt statewide numeric criteria in State 

water quality standards for all section 307(a) 

toxic pollutants for which EPA has 

developed criteria guidance, regardless of 

whether the pollutants are known to be 

present; 

Adopt specific numeric criteria in State 

water quality standards for section 307(a) 

toxic pollutants as necessary to support 

designated uses where such poilutants are 

discharged or are present in the affected 

waters and could reasonably be expected to 

interfere with designated uses; 

Adopt a “translator procedure” to be applied 

to a narrative water quality standard 

provision that prohibits toxicity in receiving 

waters. Such a procedure is to be used by 

the State in calculating derived numeric 

criteria, which shall be used for all purposes 

under section 303(c) of the CWA. At a 

minimum, such criteria need to be developed 

for section 307(a) toxic pollutants, as 

necessary to support designated uses, where 

these pollutants are discharged or present in 

the affected waters and could reasonably be 

expected to interfere with designated uses, 

Option I is consistent with State authority to 

establish water quality standards. Option 2 most 

directly reflects the CWA requirements and is the 

option recommended by EPA. Option 3, while 

meeting the requirements of the CWA, is best 

suited to supplement numeric criteria from option 

I or 2. The three options are discussed in more 

detail below. 

OFmON 1 

Adopt statewide numeric criteria in State water 

quality standards for all section 307(a) toxic 

polh~tants for which EPA has developed criteria 

guidance, regardless of whether the pollutants 

am known to be present. 

Pro: 

l simple, straightfonvard implementation 

l ensures that States will satisfy statute 

l makes maximum uses of EPA 

recommendations 

0 gets specific numbers into State water quality 

standards fast, at first 

Con: 

a some priority toxic pollutants may not be 

discharged in State 

a may cause unnecessary monitoring by States 

0 might result in “paper standards” 

Option I is within a State’s legal authority under 

the CWA to adopt broad water quality standards. 

This option is the most comprehensive approach 

to satisfy the statutory requirements because it 

would include all of the priority toxic pollutants 

for which EPA has prepared section 304(a) 

criteria guidance for either or both aquatic life 

protection and human health protection. In 

addition to a simple adoption of EPA’s section 

304(a) guidance as standards, a State must select 

a risk level for those toxic pollutants which are 

carcinogens (i.e., that cause or may cause cancer 

in humans). 

Many States find this option attractive because it 

ensures comprehensive coverage of the priority 

toxic pollutants with scientifically defensible 

criteria without the need to conduct a resourceintensive evaluation of the particular segments and 

3-16 (8’15’94) 
Chaprer 3 - Water Quality Criteria 

pollutants requiring criteria. This option also 

would not be more costly to dischargers than 

other options because permit limits would be 

based only on the regulation of the particular 

toxic pollutants in their discharges and not on the 

total listing in the water quality standards. Thus, 

actual permit limits should be the same under any 

of the options. 

The State may also exercise its authority to use 

one or more of the techniques for adjusting water 

quality standards: 

8 establish or revise designated stream uses 

based on use attainability analyses (see 

section 2.9); 

l develop site-specific criteria; or 

0 allow short-term variances (see section 5.3) 

when appropriate. 

All three of these techniques may apply to 

standards developed under any of the three 

options discussed in this guidance. It is likely 

that States electing to use option 1 will rely more 

on variances because the other two options are 

implemented with more site-specific data being 

available. It should be noted, however, that 

permits issued pursuant to such water quality 

variances still must comply with any applicable 

antidegradation and antibacksliding requirements. 

OITION 2 

Adopt specific numeric criteria in State water 

quality standards for section 307(a) toxic 

pollutants as necessary to support designated 

uses where such pollutants are discharged or 

are present in the affected waters and could 

reasonably be expected to interfere with 

designated uses. 

Pro: 

l directly reflects statutory requirement 

l standards based on demonstrated need to 

control problem pollutants 

l State can use EPA’s section 304(a) national 

criteria recommendations or other 

scientificallyacceptablealtemative, including 

site-specific criteria 

l State can consider current or potential toxic 

pollutant problems 

l State can go beyond section 307(a) toxics 

list, as desired 

Con: 

may be difficult and time consuming to 

determine if, and which, pollutants are 

interfering with the designated use 

adoption of standards can require lengthy 

debates on correct criteria limit to be 

included in standards 

successful State toxic control programs based 

on narrative criteria may be halted or slowed 

as the State applies its limited resources to 

developing numeric standards 

difficult to update criteria once adopted as 

part of standards 

to be absolutely technically defensible, may 

need site-specific criteria in many situations, 

leading to a large workload for regulatory 

agency 

EPA recommends that a State use this option to 

meet the statutory requirement. It directly reflects 

all the Act’s requirements and is flexible, 

resulting in adoption of numeric water quality 

standards as needed. To assure that the State is 

capable of dealing with new problems as they 

arise, EPA also recommends that States adopt a 

translator procedure the same as, or similar to, 

that described in option 3, but applicable to all 

chemicals causing toxicity and not just priority 

pollutants as is the case for option 3. 

(S/15/94) 3-17 
Water Quality Standards Handbook - Second Edition 

Beginning in 1988, EPA provided States with 

candidate lists of priority toxic pollutants and 

water bodies in support of CWA section 304(l) 

implementation. These lists were developed 

because States were required to evaluate existing 

and readily available water-related data to comply 

with section 304(l), 40 CFR 130.10(d). A similar 

“strawman” analysis of priority pollutants 

potentially requiring adoption of numeric criteria 

under section 303(c)(2)(B) was furnished to most 

States in September or October of 1990 for their 

use in ongoing and subsequent triennial reviews. 

The primary differences between the “strawman” 

analysis and the section 304(l) candidate lists were 

that the “strawman” analysis (I) organized the 

results by chemical rather than by water body, (2) 

included data for certain STORET monitoring 

stations that were not used in constructing the 

candidate lists, (3) included data from the Toxics 

Release Inventory database, and (4) did not 

include a number of data sources used in 

preparing the candidate lists (e.g., those, such as 

fish kill information, that did not provide 

chemical-specific information). 

EPA intends for States, at a minimum, to use the 

information gathered in support of section 304(l) 

requirements as a starting point for identifying (1) 

water segments that will need new and/or revised 

water quality standards for section 307(a) toxic 

pollutants, and (2) which priority toxic pollutants 

require adoption of numeric criteria. In the 

longer term, EPA expects similar determinations 

to occur during each triennial review of water 

quality standards as required by section 303(c). 

In identifying the need for numeric criteria, EPA 

is encouraging States to use information and data 

such as: 

l presence or potential construction of 

facilities that manufacture or use priority 

toxic pollutants; 

l ambient water monitoring data, including 

those for sediment and aquatic life (e.g., fish 

tissue data); 

NPDES permit applications and permittee 

self-monitoring reports; 

effluent guideline development documents, 

many of which contain section 307(a)(l) 

priority pollutant scans; 

pesticide and herbicide application 

information and other records of pesticide or 

herbicide inventories; 

public water supply source monitoring data 

noting pollutants with Maximum 

Contaminant Levels (MCLs); and 

any other relevant information on toxic 

pollutants collected by Federal, State, 

interstate agencies, academic groups, or 

scientific organizations. 

States are also expected to take into account 

newer information as it became available, such as 

information in annual reports from the Toxic 

Chemical Release Inventory requirements of the 

Emergency Planning and Community Right-ToKnow Act of 1986 (Title III, Public Law 99-499). 

Where the State’s review indicates a reasonable 

expectation of a problem from the discharge or 

presence of toxic pollutants, the State should 

identify the pollutant(s) and the relevant 

segment(s). In making these determinations, 

States should use their own EPA-approved criteria 

or existing EPA water quality criteria for 

purposes of segment identification. After the 

review, the State may use other means to establish 

the final criterion as it revises its standards. 

As with option 1, a State using option 2 must 

follow all its legal and administrative 

requirements for adoption of water quality 

standards. Since the resulting numeric criteria are 

part of a State’s water quality standards, they are 

required to be submitted by the State to EPA for 

review and either approval or disapproval. 

EPA believes this option offers the State optimum 

flexibility. For section 307(a) toxic pollutants 

3-18 (8115194) 
Chapter 3 - Water Quaiih, Criteria 

adversely affecting designated uses, numeric 

criteria are available for permitting purposes. For 

other situations, the State has the option of 

defining site-specific criteria. 

OPTION 3 

Adopt a procedure to be applied to the 

narrative water quality standard provision that 

prohibits toxicity in receiving waters. Such a 

procedure would be used by a State in 

calculating derived numeric criteria to be used 

for all purposes of water quality criteria under 

section 303(c) of the CWA. At a minimum 

such criteria need to be derived for section 

307(a) toxic pollutants where the discharge or 

presence of such pollutants in the affected 

waters could reasonably be expected to 

interfere with designated uses, as necessary to 

support such designated uses. 

Pro: 

allows a State flexibility to control priority 

toxic pollutants 

reduces time and cost required to adopt 

specific numeric criteria as water quality 

standards regulations 

allows immediate use of latest scientific 

information available at the time a State 

needs to develop derived numeric criteria 

revisions and additions to derived numeric 

criteria can be made without need to revise 

State law 

State can deal more easily with a situation 

where it did not establish water quality 

standards for the section 307(a) toxic 

pollutants during the most recent triennial 

review 

State can address problems from non-section 

307(a) toxic pollutants 

Con: 

0 EPA is currently on notice that a derived 

numeric criterion may invite legal challenge 

a once the necessary procedures are adopted to 

enhance legal defensibility (e.g., appropriate 

scientific methods and public participation 

and review), actual savings in time and costs 

may be less than expected 

l public participation in development of 

derived numeric criteria may be limited 

when such criteria are not addressed in a 

hearing on water quality standards 

EPA believes that adoption of a narrative standard 

along with a translator mechanism as part of a 

State’s water quality standard satisfies the 

substantive requirements of the statute. These 

criteria are subject to all the State’s legal and 

administrative requirements for adoption of 

standards plus review and either approval or 

disapproval by EPA, and result in the 

development of derived numeric criteria for 

specific section 307(a) toxic pollutants. They are 

also subject to an opportunity for public 

participation. Nevertheless, EPA believes the 

most appropriate use of option 3 is as a 

supplement to either option 1 or 2. Thus, a State 

would have formally adopted numeric criteria for 

toxic pollutants that occur frequently; that have 

general applicability statewide for inclusion in 

NPDES permits, total maximum daily loads, and 

waste load altocations; and that also would have 

a sound and predictable method to develop 

additional numeric criteria as needed. This 

combination of options provides a complete 

regulatory scheme. 

Although the approach in option 3 is similar to 

that currently allowed in the Water Quality 

Standards Regulation (40 CFR 131.1 l(a)(2)), this 

guidance discusses several administrative and 

scientific requirements that EPA believes are 

necessary to comply with section 303(c)(2)(B). 

(8/15/94) 3-19 
Water Quality Standuds Handbook - Sccoad Edition 

(1) The Option 3 Procedure Must Be Used To 

Calculate Derived Numeric Water Quality 

Criteria 

States must adopt a specific procedure to be 

applied to a narrative water quality criterion. To 

satisfy section 303(c)(2)(B), this procedure shall 

be used by the State in calculating derived 

numeric criteria, which shall be used for all 

purposes under section 303(c) of the CWA. Such 

criteria need to be developed for section 307(a) 

toxic pollutants as necessary to support designated 

uses, where these pollutants are discharged or are 

present in the affected waters and could 

reasonably be expected to interfere with the 

designated uses. 

To assure protection from short-term exposures, 

the State procedure should ensure development of 

derived numeric water quality criteria based on 

valid acute aquatic toxicity tests that are lethal to 

half the affected organisms (LC50) for the species 

representative of or similar to those found in the 

State. In addition, the State procedure should 

ensure development of derived numeric water 

quality criteria for protection from chronic 

exposure by using an appropriate safety factor 

applicable to this acute limit. If there are 

saltwater components to the State’s aquatic 

resources, the State should establish appropriate 

derived numeric criteria for saltwater in addition 

to those for freshwater. 

The State’s documentation of the tests should 

include a detailed discussion of its quality control 

and quality assurance procedures. The State 

should also include a description (or reference 

existing technical agreements with EPA) of the 

procedure it will use to calculate derived acute 

and chronic numeric criteria from the test data, 

and how these derived criteria will be used as the 

basis for deriving appropriate TMDLs, WLAs, 

and NPDES permit limits. 

As discussed above, the procedure for calculating 

derived numeric criteria needs to protect aquatic 

life from both acute and chronic exposure to 

specific chemicals. Chronic aquatic life criteria 

are to be met at the edge of the mixing zone. 

The acute criteria are to be met (1) at the end-ofpipe if mixing is not rapid and complete and a 

high rate diffuser is not present; or (2) after 

mixing if mixing is rapid and complete or a high 

rate diffuser is present. (See EPA’s Technical 

Suppon Document for War4r Quality-based Toxics 

Control, USEPA 1991a.) 

EPA has not established a national policy 

specifying the point of application in the receiving 

water to be used with human health criteria. 

However, EPA has approved State standards that 

apply human health criteria for fish consumption 

at the mixing zone boundary and/or apply the 

criteria for drinking water consumption, at a 

minimum, at the point of use. EPA has also 

proposed more stringent requirements for the 

application of human health criteria for highly 

bioaccumulative pollutants in the Wafer Qualify 

guidance for flu Great L.&es System (50 F. R. 

20931, 21035, April 16, 1993) including 

elimination of mixing zones. 

In addition, the State should also include an 

indication of potential bioconcentration or 

bioaccumulation by providing for: 

l laboratory tests that measure the steady-state 

bioconcentration rate achieved by a 

susceptible organism; and/or 

l field data in which ambient concentrations 

and tissue loads are measured to give an 

appropriate factor. 

In developing a procedure to be used in 

calculating derived numeric criteria for the 

protection of aquatic life, the State should 

consider the potential impact that bioconcentration 

has on aquatic and terrestrial food chains. 

The State should also use the derived 

bioconcentration factor and food chain multiplier 

to calculate chronically protective numeric criteria 

for humans that consume aquatic organisms. In 

calculating this derived numeric criterion, the 

State should indicate data requirements to be met 

3-20 (8115194) 
Chapter 3 - Warm Quality Crimia 

when dealing with either threshold (toxic) or nonthreshold (carcinogenic) compounds. The State 

should describe the species and the minimum 

number of tests, which may generally be met by 

a single mammalian chronic test if it is of good 

quality and if the weight of evidence indicates that 

the results are reasonable. The State should 

provide the method to calculate a derived numeric 

criterion from the appropriate test result. 

Both the threshold and non-threshold criteria for 

protecting human health should contain exposure 

assumptions, and the State procedure should be 

used to calculate derived numeric criteria that 

address the consumption of water, consumption of 

fish, and combined consumption of both water 

and fish. The State should provide the 

assumptions regarding the amount of fish and the 

quantity of water consumed per person per day, 

as well as the rationale used to select the 

assumptions. It needs to include the number of 

tests, the species necessary to establish a doseresponse relationship, and the procedure to be 

used to calculate the derived numeric criteria. 

For non-threshold contaminants, the State should 

specify the model used to extrapolate to low dose 

and the risk level. It should also address 

incidental exposure from other water sources 

(e.g., swimming). When calculating derived 

numeric criteria for multiple exposure to 

pollutants, the State should consider additive 

effects, especially for carcinogenic substances, 

and should factor in the contribution to the daily 

intake of toxicants from other sources (e.g., food, 

air) when data are available. 

(2) The State Must Demonstrate That the 

Procedure Results in Derived Numeric 

Criteria Are Protective 

The State needs to demonstrate that its procedures 

for developing criteria, including translator 

methods, yield fully protective criteria for human 

health and for aquatic life. EPA’s review process 

will proceed according to EPA’s regulation of 40 

CFR 13 1.11, which requires that criteria be based 

on sound scientific rationale and be protective of 

all designated uses. EPA will use the expertise 

and experience it has gained in developing section 

304(a) criteria for toxic pollutants by application 

of its own translator method ([JSEPA, 1980b; 

USEPA, 1985b). 

Once EPA has approved the State’s procedure, 

the Agency’s review of derived numeric criteria, 

for example, for pollutants other than section 

307(a) toxic pollutants resulting from the State’s 

procedure, will focus on the adequacy of the data 

base rather than the calculation method. EPA 

also encourages States to apply such a procedure 

to calculate derived numeric criteria to be used as 

the basis for deriving permit limitations for 

nonconventional pollutants that also cause 

toxicity. 

(3) The State Must Provide Full Opportunity 

for Public Participation in Adoption of the 

Procedure 

The Water Quality Standards Regulation requires 

States to hold public hearings to review and revise 

water quality standards in accordance with 

provisions of State law and EPA’s Public 

Participation Regulation (40 CFR 25). Where a 

State plans to adopt a procedure to be applied to 

the narrative criterion, it must provide full 

opportunity for public participation in the 

development and adoption of the procedure as part 

of the State’s water quality standards. 

While it is not necessary for the State to adopt 

each derived numeric criterion into its water 

quality standards and submit it to EPA for review 

and approval, EPA is very concerned that all 

affected parties have adequate opportunity to 

participate in the development of a derived 

(8/15i94) 3-2 1 
Water Quality Standards Handbook - Second Edition 

numeric criterion even though it is not being 

adopted directly as a water quality standard. 

A State can satisfy the need to provide an 

opportunity for public participation in the 

development of derived numeric criteria in several 

ways, including: 

0 a specific hearing on the derived numeric 

criterion; 

l the opportunity for a public hearing on an 

NPDES permits as long as public notice is 

given that a criterion for a toxic pollutant as 

part of the permit issuance is being 

contemplated; or 

l a hearing coincidental with any other hearing 

as long as it is made clear that development 

of a specific criterion is also being 

undertaken. 

For example, as States develop their lists and 

individual control strategies (ICSs) under section 

304( 1), they may seek full public participation. 

NPDES regulations also specify public 

participation requirements related to State permit 

issuance. Finally, States have public participation 

requirements associated with Water Quality 

Management Plan updates. States may take 

advantage of any of these public participation 

requirements to fulfill the requirement for public 

review of any resulting derived numeric criteria. 

In such cases, the State must give prior notice that 

development of such criteria is under 

consideration. 

(4) The Procedure Must Be FormalIy Adopted 

and Mandatory 

Where a State elects to supplement its narrative 

criterion with an accompanying implementing 

procedure, it must formally adopt such a 

procedure as a part of its water quality standards. 

The procedure must be used by the State to 

calculate derived numeric criteria that will be used 

as the basis for all standards’ purposes, including 

the following: developing TMDLs, WLAs, and 

limits in NPDES permits; determining whether 

water use designations are being met; and 

identifying potential nonpoint source pollution 

problems. 

(5’) The Procedure Must Be Approved by EPA 

as Part of the State’s Water Quality 

Standards Regulation 

To be consistent with the requirements of the Act, 

the State’s procedure to be applied to the narrative 

criterion must be submitted to EPA for review 

and approval, and will become a part of the 

State’s water quality standards. (See 40 CFR 

131.21 for further discussion.) This requirement 

may be satisfied by a reference in the standards to 

the procedure, which may be contained in another 

document, which has legal effect and is binding 

on the State, and all the requirements for public 

review, State implementation, and EPA review 

and approval are satisfied. 

Criteria Based on Biological Monitoring 

For priority toxic pollutants for which EPA has 

not issued section 304(a)( 1) criteria guidance, 

CWA section 303(c)(2)(B) requires States to adopt 

criteria based on biological monitoring or 

assessment methods. The phrase “biological 

monitoring or assessment methods” includes: 

l whole-effluent toxicity control methods; 

l biological criteria methods; or 

l other methods based on biological 

monitoring or assessment. 

The phrase “biological monitoring or assessment 

methods” in its broadest sense also includes 

criteria developed through translator procedures. 

This broad interpretation of that phrase is 

consistent with EPA’s policy of applying 

chemical-specific, biological, and whole-effluent 

toxicity methods independently in an integrated 

toxics control program. It is also consistent with 

the intent of Congress to expand State standards 

programs beyond chemical-specific approaches. 

3-22 (8/15/94) 
Chaprer 3 - Wurrr Qutrlm Crileriu 

States should also consider developing protocols 

to derive and adopt nurncric criteria for priority 

toxic pollutants; (or other pollutants) where EPA 

has not issued sccticjn 304(a) criteria guidance. 

The S (ate should consider available laboratory 

toxicity test data that may be sufficient to support 

derivation of chemical-specific criteria. Existing 

data nwd not be as comprehensive as that 

required to meet EPA’s 1985 guidelines in order 

for a State to use its own protocols to derive 

criteria. EPA has described such protocols in the 

proposed Wult’r Qlctrliiy Guiilunw for Ih4 Great 

Lakes .Y~.sff*m (38 f:.R. 20892. at 21016, April 16, 

1993.) This is particularly important where other 

components of a Stitc’s narrative criterion 

implementation proccdl.re (e.g., WET controls or 

biological criteria) may not ensure full protection 

of designated uses. f:or some pollutants, a 

combination of chemical-specific and other 

approaches IS ncccssary (e.g., pollutants where 

bioaccumulation in fish tissue or water 

consumption by humans is a primary concern). 

Biologically based monitoring or assessment 

methods serve as the basis for control where no 

specific numeric criteria exist or where calculation 

or application of pollutant-by-pc~llutant criteria 

appears int‘cdsiblc. Also, the.se methods may 

serve as a supplemental measurement of 

attainment of water quality standards in addition 

to numeric and narratlvc criteria. The 

requirement for both numeric criteria and 

biologically based methods demonstrates that 

section 303(c)( 2 j(B) contemplates that States 

develop a comprehensi\,e toxics control program 

regardless of the status of EPA’s section 304(a) 

criteria. 

The whole-effluent toxicity (WET) testing 

procedure is the principal biological monitoring 

guidance developed by EPA to date. The purpose 

of the WET procedure is to control point source 

dischargers of toxic pollutants. The procedure is 

particularly useful for monitoring and controlling 

the toxicity of complex effluents that may not be 

well controlled through chemical-specific numeric 

criteria. As such, biologically based effluent 

testing procedures are a necessary component of 

a State’s toxics control program under section 

303(c)(2)(B) and a principal means for 

implementing a State’s narrative “free from 

toxics” standard. 

Guidance documents EPA considers to serve the 

purpose of section 304(a)(8) include the Technical 

Support Documeru fr,r Wuter Quulif)-bused ToxicJ 

Control (USEPA, 199 1 a; Guiddines jiv Deriviq 

Nationul Water Quulity Criteriu.fiv rhe Protecrion 

of Aquuric Organisms and Their Uses (Appendix 

H); Guidelines and Merhodolqqv Usd in the 

Preparabon of Health Eflecr As.ses.snwrr Chapters 

of the Cement Decree Water Crireriu Documenrs 

(Appendix 1); Methods fiv Meusuring Awe 

Toxicity of Efluenrs to Freshwarer uncl Marine 

Organisms (USEPA, 199 Id); Short- Term Methods 

$v Esrimaring the Chronic Ttsriciry rrf Efluenrs 

and Receiving Waters to Fw.sh\rwer 0r~unism.s 

(USEPA, 199 le); and Shon-Term Mrrhtds /iv 

Esrimaring she Chronic Toxicir?* 04‘ IZfluenrs and 

Receiving Waters 10 Murinc und Emarine 

Organisms (USEPA, 19910. 

3.4.2 Criteria for Nonconventional Pollutants 

Criteria requirements applicable to toxicants that 

are not priority toxic pollutants (e.g.. ammonia 

and chlorine), are specified in the 1983 Water 

Quality Standards Regulation (see 40 CFR 

131.11). Under these requirements, States must 

adopt criteria based on sound scientific rationale 

that cover sufficient parameters to protect 

designated uses. Both numeric and narrative 

criteria (discussed in sections 3.5.1 and 3.5.2, 

below) may be applied to meet these 

requirements. 

cl 

3.5 Forms of Criteria 

States are required to adopt water quality criteria, 

based on sound scientific rationale, that contain 

sufficient parameters or constituents to protect the 

designated use. EPA believes that an effective 

State water quality standards program should 

include both parameter-specific (e.g., ambient 

numeric criteria) and narrative approaches. 

(8/15/94) 3-23 
Water Quality Standards Handbook - Second Ed&on 

3.5.1 Numeric Criteria 

Numeric criteria are required where necessary to 

protect designated uses. Numeric criteria to 

protect aquatic life should be developed to address 

both short-term (acute) and long-term (chronic) 

effects. Saltwater species, as well as freshwater 

species, must be adequately protected. Adoption 

of numeric criteria is particularly important for 

toxicants known to be impairing surface waters 

and for toxicants with potential human health 

impacts (e.g., those with high bioaccumulation 

potential). Human health should be protected 

from exposure resulting from consumption of 

water and fish or other aquatic life (e.g., mussels, 

crayfish). Numeric water quality criteria also are 

useful in addressing nonpoint source pollution 

problems. 

In evaluating whether chemical-specific numeric 

criteria for toxicants that are m priority toxic 

pollutants are required, States should consider 

whether other approaches (such as whole-effluent 

toxicity criteria or biological controls) will ensure 

full protection of designated uses. As mentioned 

above, a combination of independent approaches 

may be required in some cases to support the 

designated uses and comply with the requirements 

of the Water Quality Standards Regulation (e.g., 

pollutants where bioaccumulation in fish tissue or 

water consumption by humans is a primary 

concern). 

3.5.2 Narrative Criteria 

To supplement numeric criteria for toxicants, all 

States have also adopted narrative criteria for 

toxicants. Such narrative criteria are statements 

that describe the desired u’ater quality goal, such 

as the following: 

All waters, including those within 

mixing zones, shall be free from 

substances attributable to wastewater 

discharges or other pollutant sources 

that: 

Settle to form objectional 

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; or 

Produce undesirable or nuisance 

aquatic life (54 F.R. 28627, July 

6, 1989). 

EPA considers that the narrative criteria apply to 

all designated uses at all flows and are necessary 

to meet the statutory requirements of section 

303(c)(2)(A) of the CWA. 

Narrative toxic criteria (No. 4, above) can be the 

basis for establishing chemical-specific limits for 

waste discharges where a specific pollutant can be 

identified as causing or contributing to the toxicity 

and the State has not adopted chemical-specific 

numeric criteria. Narrative toxic criteria are cited 

as a basis for establishing whole-effluent toxicity 

controls in EPA permitting regulations at 40 CFR 

122.44(d)(l)(v). 

To ensure that narrative criteria for toxicants are 

attained, the Water Quality Standards Regulation 

requires States to develop implementation 

procedures (see 40 CFR 131. I l(a)(2)). Such 

implementation procedures (Exhibit 3-3) should 

address all mechanisms to be used by the State to 

ensure that narrative criteria are attained. 

Because implementation of chemical-specific 

numeric criteria is a key component of State 

toxics control programs, narrative criteria 

implementation procedures must describe or 

reference the State’s procedures to implement 

such chemical-specific numeric criteria (e.g., 

procedures for establishing chemical-specific 

permit limits under the NPDES permitting 

(8115194) 
Chuprn 3 - Wa~cr Quality Critcrio 

State implementation procedures for narrative toxics criteria should describe the following: 

8 Specific, scientifically defensible methods by which the State will implement its narrative 

toxics standard for all toxicants, including: 

- methods for chemical-specific criteria, including methods for applying chemical-specific 

criteria in permits, developing or modifying chemical-specific criteria via a “translator 

procedure” (defined and discussed below), and calculating site-specific criteria based 

on local water chemistry or biology); 

- methods for developing and implementing whole-effluent toxicity criteria and/or 

controls; and 

- methods for developing and implementing biological criteria. 

l How these methods will be integrated in the State’s toxics control program (i.e., how the 

State will proceed when the specified methods produce conflicting or inconsistent results). 

l Application criteria and information needed to apply numerical criteria, for example: 

- methods the State will use to identify those pollutants to be regulated in a specific 

discharge; 

- an incremental cancer risk level for carcinogens: 

- methtis for identifying compliance thresholds in permits where calculated limits are 

below detection; 

- methods for selecting appropriate hardness, pH, and temperature variables for criteria 

expressed as functions; 

- methods or policies controlling the size and in-zone quality of mixing zones; 

- design flows to be used in translating chemical-specific numeric criteria for aquatic life 

and human health into permit limits; and 

- other methods and information needed to apply standards on a case-by-case basis. 

Exhibit 3-3. Components of a State Implementation Procedure for Narrative Toxics Criteria 

(8f 15f94) 3-25 
H’utrr Oulltv Standards Handhook - Second Edition 

program). Implementation procedures must also 

address State programs to control whole-effluent 

toxicity (WET) and may address programs to 

implement biological criteria, where such 

programs have been developed by the State. 

Implementation procedures therefore serve as 

umbrella documents that describe how the State’s 

various toxics control programs are integrated to 

ensure adequate protection for aquatic life and 

human health and attainment of the narrative 

toxics criterion. In essence, the procedure should 

apply the “independent application” principle, 

which provides for independent evaluations of 

attainment of a designated use based on chemicalspecific, whole-eftluent toxicity, and biological 

criteria methods (see section 3.5.3 and 

Appendices C. K. and R). 

EPA encourages, and may ultimately require, 

State implementation procedures to provide for 

implementation of biological criteria. However, 

the regulatory basis for requiring whole-effluent 

toxicity (WET) controls is clear. EPA regulations 

at 40 CFR 122.44(d)(l)(v) require NPDES 

permits to contain WET limits where a permittee 

has been shown to cause, have the reasonable 

potential to cause, or contribute to an in-stream 

excursion of a narrative criterion. Implementation 

of chemical-specific controls is also required by 

EPA regulations at 40 CFR 122.44(d)(l). State 

implementation procedures should, at a minimum, 

specify or reference methods to be used in 

implementingchemical-specificand whole-effluent 

toxicity-based controls, explain how these 

methods are integrated, and specify needed 

application criteria. 

In addition to EPA’s regulation at 40 CFR 13 1, 

EPA has regulations at 40 CFR 122.44 that cover 

the National Surface Water Toxics Control 

Program. These regulations are intrinsically 

linked to the requirements to achieve water 

quality standards, and specifically address the 

control of pollutants both with and without 

n urneric criteria. For example, section 

12?.44(d)( l)(vi) provides the permitting authority 

with several options for establishing effluent limits 

when a State does not have a chemical-specific 

numeric criterion for a pollutant present in an 

effluent at a concentration that causes or 

contributes to a violation of the State’s narrative 

criteria. 

3.5.3 Biological Criteria 

The Clean Water Act of 1972 directs EPA to 

develop programs that will evaluate, restore, and 

maintain the chemical, physical, and biological 

integrity of the Nation’s waters. In response to 

this directive, States and EPA have implemented 

chemically based water quality programs that 

address significant water pollution problems. 

However, over the past 20 years, it has become 

apparent that these programs alone cannot identify 

and address all surface water pollution problems. 

To help create a more comprehensive program, 

EPA is setting a priority for the development of 

biological criteria as part of State water quality 

standards. This effort will help States and EPA 

(1) achieve the biological integrity objective of the 

CWA set forth in section 101, and (2) comply 

with the statutory requirements under sections 303 

and 304 of the Act (see Appendices C and K). 

Regulatory Bases for Biocriteria 

The primary statutory basis for EPA’s policy that 

States should develop biocriteria is found in 

sections 101(a) and 303(c)(2)(B) of the Clean 

Water Act. Section 101(a) of the CWA gives the 

general goal of biological criteria. It establishes 

as the objective of the Act the restoration and 

maintenance of the chemical, physical, and 

biological integrity of the Nation’s waters. To 

meet this objective, water quality criteria should 

address biological integrity. Section 101(a) 

includes the interim water quality goal for the 

protection and propagation of fish, shellfish, and 

wildlife. 

Section 304(a) of the Act provides the legal basis 

for the development of informational criteria, 

including biological criteria. Specific directives 

for the development of regulatory biocriteria can 

be found in section 303(c), which requires EPA to 

develop criteria based on biological assessment 

3-26 (8f 15194) 
hlJpkT 3 - WlJJPT @JAcJlif~ CriJWifJ 

methods when numerical criteria are not 

established. 

Section 304(a) directs EPA to develop and publish 

water quality criteria and information on methods 

for measuring water quality and establishing water 

quality criteria for toxic pollutants on bases other 

than pollutant-by-pollutant, including biological 

monitoring and assessment methods that assess: 

l the effects of pollutants on aquatic 

community components (“. . . plankton, 

fish, shellfish, wildlife, plant life . . .“) and 

community attributes (“. . . biological 

community diversity, productivity, and 

stability . . . I’) in any body of water; and 

0 factors necessary ” . . . to restore and 

maintain the chemical, physical, and 

biological integrity of all navigable waters . 

. . ” for ” . . . the protection of shellfish, 

fish, and wildlife for classes and categories 

of receiving waters , . . .” 

Once biocriteria are formally adopted into State 

standards, biocriteria and aquatic life use 

designations serve as direct, legal endpoints for 

determining aquatic life use attainment/nonattainment. CWA section 303(c)(2)(B) provides 

that when numeric criteria are not available, 

States shall adopt criteria for toxics based on 

biological monitoring or assessment methods; 

biocriteria can be used to meet this requirement. 

Development and Implementation of 

Biocriteria 

Biocriteria are numerical values or narrative 

expressions that describe the expected reference 

biological integrity of aquatic communities 

inhabiting waters of a designated aquatic life use. 

In the most desirable scenario, these would be 

waters that are either in pristine condition or 

minimally impaired. However, in some areas 

these conditions no longer exist and may not be 

attainable. In these situations, the reference 

biological communities represent the best 

attainable conditions. In either case, the reference 

conditions then become the basis for developing 

biocriteria for major surface water types (streams, 

rivers, lakes. wetlands, estuaries, or marine 

waters). 

Biological criteria support designated aquatic life 

use classifications for application in State 

standards (see chapter 2). Each State develops its 

own designated use classification system based on 

the generic uses cited in the Act (e.g., protection 

and propagation of fish, shellfish, and wildlife). 

Designated uses are intentionally general. 

However, States may develop subcategories 

within use designations to refine and clarify the 

use class. Clarification of the use class is 

particularly helpful when a variety of surface 

waters with distinct characteristics fit within the 

same use class. or do not fit well into any 

category. 

For example, subcategories of aquatic life uses 

may be on the basis of attainable habitat (e.g., 

coldwater versus warmwater stream systems as 

represented by distinctive trout or bass fish 

communities, respectively). Special uses may 

also be designated to protect particularly unique, 

sensitive, or valuable aquatic species, 

communities, or habitats. 

Resident biota integrate multiple impacts over 

time and can detect impairment from known and 

unknown causes. Biological criteria can be used 

to verify improvement in water quality in 

response to regulatory and other improvement 

efforts and to detect new or continuing 

degradation of waters. Biological criteria also 

provide a framework for developing improved 

best management practices and management 

measures for nonpoint source impacts. Numeric 

biological criteria can provide effective 

monitoring criteria for more definitive evaluation 

of the health of an aquatic ecosystem. 

The assessment of the biological integrity of a 

water body should include measures of the 

structure and function of the aquatic community 

within a specified habitat. Expert knowledge of 

the system is required for the selection of 

(8!15/94) 3-27 
Water Ouahtv Standards Hnndbcmk - Secand Edition 

appropriate biological components and 

measurement indices. The development and 

implementation of biological criteria requires: 

selection of surface waters to use in 

developing reference conditions for each 

designated use; 

measurement of the structure and function of 

aquatic communities in reference surface 

waters to establish biological criteria; 

measurement of the physical habitat and 

other environmental characteristics of the 

water resource; and 

establishment of a protocol to compare the 

biological criteria to biota in comparable test 

waters to determine whether impairment has 

occur-red. 

These elements serve as an interactive network 

that is particularly important during early 

development of biological criteria where rapid 

accumulation of information is effective for 

refining both designated uses and developing 

biological criteria values and the supporting 

biological monitoring and assessment techniques. 

3.54 Sediment Criteria 

While ambient water quality criteria are playing 

an important role in assuring a healthy aquatic 

environment, they alone have not been sufficient 

to ensure appropriate levels of environmental 

protection. Sediment contamination, which can 

involve deposition of toxicants over long periods 

of time, is responsible for water quality impacts 

in some areas. 

EPA has authority to pursue the development of 

sediment criteria in streams, lakes and other 

waters of the United States under sections 104 and 

304(a)( 1) and (2) of the CWA as follows: 

l section 104(n)( 1) authorizes the 

Administrator to establish national programs 

that study the effects of pollution, including 

sedimentation, in estuaries on aquatic life; 

l section 304(a)( 1) directs the Administrator to 

develop and publish criteria for water 

quality, including information on the factors 

affecting rates of organic and inorganic 

sedimentation for varying types of receiving 

waters; 

a section 304(a)(2) directs the Administrator to 

develop and publish information on, among 

other issues, “the factors necessary for the 

protection and propagation of shellfish, fish, 

and wildlife for classes and categories of 

receiving waters. . , .” 

To the extent that sediment criteria could be 

developed that address the concerns of the section 

404(b)( 1) Guidelines for discharges of dredged or 

fill material under the CWA or the Marine 

Protection, Research, and Sanctuaries Act, they 

could also be incorporated into those regulations. 

EPA’s current sediment criteria development 

effort, as described below, focuses on criteria for 

the protection of aquatic life. EPA anticipates 

potential future expansion of this effort to include 

sediment criteria for the protection of hurnan 

health. 

Chemical Approach to Sediment Criteria 

Development 

Over the past several years, sediment criteria 

development activities have centered on evaluating 

and developing the Equilibrium Partitioning 

Approach for generating sediment criteria. The 

Equilibrium Partitioning Approach focuses on 

predicting the chemical interaction between 

sediments and contaminants. Developing an 

understanding of the principal factors that 

influence the sediment/contaminant interactions 

will allow predictions to be made regarding the 

level of contaminant concentration that benthic 

and other organisms may be exposed to. Chronic 

water quality criteria, or possibly other 

toxicological endpoints, can then be used to 

3-28 ;a1 15/94) 
Chapter 3 - Wa~rr Qualin, Criteria 

predict potential biological effects. In addition to 

the development of sediment criteria, EPA is also 

working to develop a standardized sediment 

toxicity test that could be used with or 

independently of sediment criteria to assess 

chronic effects in fresh and marine waters. 

Eguilibtium Partitioning (EqP) Sediment 

Quality C&e&2 (SQC) are the U.S. 

Environmental Protection Agency’s best 

recommendation of the concentration of a 

substance in sediment that will not 

unacceptably qffect benthic organisms or 

their uses. 

Methodologies for deriving effects-based SQC 

vary for different classes of compounds. For 

non-ionic organic chemicals, the methodology 

requires normalization to organic carbon. A 

methodology for deriving effects-based sediment 

criteria for metal contaminants is under 

development and is expected to require 

normalization to acid volatile sulfide. EqP SQC 

values can be derived for varying degrees of 

uncertainty and levels of protection, thus 

permitting use for ecosystem protection and 

remedial programs. 

Application of Sediment Criteria 

SQC would provide a basis for making more 

informed decisions on the environmental impacts 

of contaminated sediments. Existing sediment 

assessment methodologies are limited in their 

ability to identify chemicals of concern, 

responsible parties, degree of contamination, and 

zones of impact. To make the most informed 

decisions, EPA believes that a comprehensive 

approach using SQC and biological test methods 

is preferred. 

Sediment criteria will be particularly valuable in 

site-monitoring applications where sediment 

contaminant concentrations are gradually 

approaching a criterion over time or as a 

preventive tool to ensure that point and nonpoint 

sources of contamination are controlled and that 

uncontaminated sediments remain uncontaminated. 

Also comparison of field measurements to 

sediment criteria will be a reliable method for 

providing early warning of a potential problem. 

An early warning would provide an opportunity to 

take corrective action before adverse impacts 

occur. For the reasons mentioned above, it has 

been identified that SQC are essential to resolving 

key contaminated sediment and source control 

issues in the Great Lakes. 

Spec$c Applications 

Specific applications of sediment criteria are 

under development. The primary use of FqPbased sediment criteria will be to assess risks 

associated with contaminants in sediments. The 

various offices and programs concerned with 

contaminated sediment have different regulatory 

mandates and, thus, have different needs and 

areas for potential application of sediment criteria. 

Because each regulatory need is different, EqPbased sediment quality criteria designed 

specifically to meet the needs of one office or 

program may have to be implemented in different 

ways to meet the needs of another office or 

program. 

One mode of application of FqP-based numerical 

sediment quality criteria would be in a tiered 

approach. In such an application, when 

contaminants in sediments exceed the sediment 

quality criteria the sediments would be considered 

as causing unacceptable impacts. Further testing 

may or may not be required depending on sitespecific conditions and the degree in which a 

criterion has been violated. (In locations where 

contamination significantly exceeds a criterion, no 

additional testing would be required. Where 

sediment contaminant levels are close to a 

criterion, additional testing might be necessary.) 

Contaminants in a sediment at concentrations less 

than the sediment criterion would not be of 

concern. However, in some cases the sediment 

could not be considered safe because it might 

contain other contaminants above safe levels for 

which no sediment criteria exist. In addition, the 

synergistic, antagonistic, or additive effects of 

(8!15!94) 3-29 
Water Quality Standards Handhwk - Second E&bon 

several contaminants in the sediments may be of 

concern. 

Additional testing in other tiers of an evaluation 

approach, such astoxicity tests, could be required 

to determine if the sediment is safe. It is likely 

that such testing would incorporate site-specific 

considerations. Examples of specific applications 

of sediment criteria after they are developed 

include the following: 

0 Establish permit limits for point sources to 

ensure that uncontaminated sediments remain 

uncontaminated or sediments already 

contaminated have an opportunity to cleanse 

themselves. Of course, this would occur 

only after criteria and the means to tie point 

sources to sediment contamination are 

developed. 

l Establish target levels for nonpoint sources 

of sediment contamination. 

0 For remediation activities, SQC would be 

valuable in identifying: 

- need for remediation. 

- spatial extent of remediation area, 

- benetits derived from remediation 

activities, 

- responsible parties, 

- impacts of depositing contaminated 

sediments in water environments, and 

- success of remediation activities. 

In tiered testing sediment evaluation processes, 

sediment criteria and biological testing procedures 

work very well together. 

Sediment Criteria Status 

Science Advisory Board Review 

The Science Advisory Board has completed a 

second review of the EqP approach to deriving 

sediment quality criteria for non-ionic 

contaminants. The November 1992 report 

(USEPA, 1992~) endorses the EqP approach to 

deriving criteria as ‘I. . . sufficiently valid to be 

used in the regulatory process if the uncertainty 

associated with the method is considered, 

described, and incorporated,” and that “EPA 

should . . . establish criteria on the basis of 

present knowledge within the bounds of 

uncertainty. . . .” 

The Science Advisory Board also identified the 

need for “. . . a better understanding of the 

uncertainty around the assumptions inherent in the 

approach, including assumptions of equilibrium, 

bioavailability, and kinetics, all critical to the 

application of the EqP.” 

Sediment Criteria Documents and 

Application Guidance 

EPA efforts at producing sediment criteria 

documents are being directed first toward 

phenanthrene, fluoranthene. dieldrin, 

acenaphthene, and endrin. Efforts are also being 

directed towards producing a guidance docurncnt 

on the derivation and interpretation of sediment 

quality criteria. The criteria documents were 

announced in the Fe&ml ReKisrer in January 

1994; the public comment period ended June 

1994. Final documents and implementation 

guidance should be available in early 1996. 
Methodology for Developing Sediment 

Criteria for Metal Contaminants 

EPA is proceeding to develop a methodology for 

calculating sediment criteria for benthic toxicity to 

metal contaminants, with key work focused on 

identifying and understanding the role of acid 

volatile sulfides (AVS), and other binding factors, 

in controlling the bioavailability of metal 

contaminants. A variety of field and laboratory 

verification studies are under way 10 add 

additional support to the methodology. Standard 

AVS sampling and analytical procedures are 

under development. Presentation of the metals 

methodology to the SAB for review is anticipated 

for Fall 1994. 

BiolbgicaL Approach to Sediment Criteria 

Development 

Under the Contaminated Sediment Management 

Strategy, EPA programs have committed to using 

consistent biological methods to determine if 

sediments are contaminated. In the water 

program, these biological methods will be used as 

a complement to the sediment-chemical criteria 

under development. The biological methods 

consist of both toxicity and bioaccumulation tests. 

Freshwater and saltwater benthic species, selected 

to represent the sensitive range of species’ 

responses to toxicity. are used in toxicity tests to 

measure sediment toxicity. Insensitive freshwater 

and saltwater benthic species that form the base of 

the food chain are used in toxicity tests to 

measure the bioaccumulation potential of 

sediment. In FY 1994, acute toxicity tests and 

bioaccumulation tests selected by all the Agency 

programs should be standardized and available for 

use. Training for States and EPA Regions on 

these methods is expected to begin in FY 1995. 

In the next few years, research will be conducted 

to develop standardized chronic toxicity tests for 

sediment as well as toxicity identification 

evaluation (TIE) methods. The TIE approach will 

be used to identify the specific chemicals in a 

sediment causing acute or chronic toxicity in the 

test organisms. Under the Contaminated 

Sediment Management Strategy, EPA’s programs 

have also agreed to incorporate these chronic 

toxicity and TIE methods into their scdirncnt 

testing when they are available. 

3.5.5 Wildlife Criteria 

Terrestrial and avian spccics arc usciul as 

sentinels for the health of the ecob>‘stcnl as a 

whole. In many cases, damage to wildlife 

indicates that the ecosystem Itself is damaged. 

Many wildlife species that are heavily dependent 

on the aquatic food web reflect the health of 

aquatic systems. In the case of toxic chemicals, 

terminal predators such as otter, mink. gulls, 

terns, eagles, ospreys, and turtles arc useful as 

integrative indicators of the status or health of the 

ecosystem, 

Statutory and Regulatory Aut horitl 

Section 101(a)(2) of the CWA sets. as an interim 

goal of, 

. . . wherever attainable . . water 

quality which provides for the 

SK :tion 304(a)( I) of the Act also rcquircs ItPA to: 

protectio n 

shellfish, 

added). 

and propagation of fish. 

and wildlife . (emphasis 

. . . develop and publish criteria for 

water quality accurately reflecting . . . the 

kind and extent of all identifiable effects on 

health and welfare including . . . wildlife. 

The Water Quality Standards Regulation reflect 

the statutory goals and requirements by requiring 

States to adopt, where attainable, the CWA 

section 101(a)(2) goal uses of protection and 

propagation of fish, shellfish, and n,ildlife (40 

CFR 131. lo), and to adopt water quality criteria 

sufficient to protect the designated USL’ (40 CFR 

131.11). 

(8/15/94) 3-31 
Water Quality Se Handbook - Second Edition 

Wildlife Protection in Current Aquatic 

Criteria 

Current water quality criteria methodology is 

designed to protect fish, benthic invertebrates, and 

zooplankton; however, there is a provision in the 

current aquatic life criteria guidelines (Appendix 

H) that is intended to protect wildlife that 

consume aquatic organisms from the 

bioaccumulative potential of a compound. The 

final residue value can be based on either the 

FDA Action Level or a wildlife feeding study. 

However, if maximum permissible tissue 

concentration is not available from a wildlife 

feeding study, a final residue value cannot be 

derived and the criteria quantification procedure 

continues without further consideration of wildlife 

impacts. Historically, wildlife have been 

considered only after detrimental effects on 

wildlife populations have been observed in the 

environment (this occurred with relationship to 

DDT, selenium, and PCBs). 

Wildlife Criteria Development 

EPA’s national wildlife criteria effort began 

following release of a 1987 Government 

Accounting Office study entitled Wild@? 

Munagement - Nutionul Refuge Contamination Is 

D$iculr To Confirm and Cleun Up (GAO, 1987). 

After waterfowl deformities observed at Kesterson 

Wildlife Refuge were linked to selenium 

contamination in the water, Congress requested 

this study and recommended that “the 

Administrator of EPA, in close coordination with 

the Secretary of the Interior, develop water 

quality criteria for protecting wildlife and their 

refuge habitat. q 

In November of 1988, EPA’s Environmental 

Research Laboratory in Corvallis sponsored a 

workshop entitled Wurer Quality Criteria To 

Protect Wildli/4 Resources, (USEPA, 1989g) 

which was co-chaired by EPA and the Fish and 

Wildlife Service (FWS). The workshop brought 

together 26 professionals from a variety of 

institutions, including EPA, FWS, State 

governments, academia, and consultants who had 

expertise in wildlife toxicity, aquatic toxicity, 

=)logy 7 environmental risk assessment, and 

conservation. Efforts at he workshop focused on 

evaluating the need for, and developing a strategy 

for production of wildlife criteria. Two 

recommendations came out of that workshop: 

(1) The process by which ambient 

water quality criteria are 

established should be modified to 

consider effects on wildlife; and 

(2) chemicals should be prioritized 

based on their potential to 

adversely impact wildlife species. 

Based on the workshop recommendations, 

screening level wildlife criteria (SLWC) were 

calculated for priority pollutants and chemicals of 

concern submitted by the FWS to gauge the extent 

of the problem by: 

( 1) evaluating whether existing water 

quality criteria for aquatic life are 

protective of wildlife, and 

(2) prioritizing chemicals for their potential 

to adversely impact wildlife species. 

There were 82 chemicals for which EPA had the 

necessary toxicity information as well as ambient 

water quality criteria, advisories, or lowestobserved-adverse-effect levels (LOAELs) to 

compare with the SLWC values. As would be 

expected, the majority of chemicals had SLWC 

larger than existing water quality criteria, 

advisories, or LOAELs for aquatic life. 

However, the screen identified classes of 

compounds for which current ambient water 

quality criteria may not be adequately protective 

of wildlife: chlorinated alkanes, benzenes, 

phenols, metals, DDT, and dioxins. hlany of 

these compounds are produced in very large 

amounts and have a variety of uses (e.g., 

solvents, flame retardants, organic syntheses of 

fungicides and herbicides, and manufacture of 

plastics and textiles. The manufacture and use of 

3-32 (8: lSi94) 
ChaDler 3 - Water C?udiN Critm’a 

these materials produce waste byproduct). Also, 

5 of the 21 are among the top 25 pollutants 

identified at Superfund sites in 1985 (3 metals, 2 

organ&). 

Following this initial effort, EPA held a national 

meeting in April 1992’ to constructively discuss 

and evaluate proposed methodologies for deriving 

wildlife criteria to build consensus among the 

scientific community as to the most defensible 

scientifically approach(es) to be pursued by EPA 

in developing useful and effective wildlife criteria. 

The conclusions of this national meeting were as 

follows: 

0 wildlife criteria should have a tissue-residue 

component when appropriate; 

0 peer-review of wildlife criteria and data sets 

should be used in their derivation; 

a wildlife criteria should incorporate methods 

to establish site-specific wildlife criteria; 

0 additional amphibian and reptile toxicity data 

are needed; 

l further development of inter-species 

toxicological sensitivity factors are needed; 

and 

0 criteria methods should measure biomarkers 

in conjunction with other studies. 

On April 16, 1993, EPA proposed wildlife 

criteria in the Wurer Qualify Guidunce for fk 

Great Lakes Sysrem (58 F.R. 20802). The 

proposed wildlife criteria are based on the current 

EPA noncancer human health criteria approach. 

In this proposal, in addition to requesting 

comments on the proposed Great Lakes criteria 

and methods, EPA also requested comments on 

possible modifications of the proposed Great 

Lakes approach for consideration in the 

development of national wildlife criteria. 

3.5.6 Numeric Criteria for Wetlands 

Extension of the EPA national 304(a) numeric 

aquatic life criteria to wetlands is recommended 

as part of a program to develop standards and 

criteria for wetlands. Appendices D and E 

provide an overview of the need for standards and 

criteria for wetlands. The 304(a) numeric aquatic 

life criteria are designed to be protective of 

aquatic life for surface waters and are generally 

applicable to most wetland types. Appendix E 

provides a possible approach, based on the sitespecific guidelines, for detecting wetland types 

that might not be protected by direct application 

of national 304(a) criteria. The evaluation can be 

simple and inexpensive for those wetland types 

for which sufficient water chemistry and species 

assemblage data are available, but will be less 

useful for wetland types for which these data are 

not readily available. In Appendix E, the sitespecific approach is described and recommended 

for wetlands for which modification of the 304(a) 

numeric criteria are considered necessary. The 

results of this type of evaluation, combined with 

information on local or regional environmental 

threats, can be used to prioritize wetland types 

(and individual criteria) for further site-specific 

evaluations and/or additional data collection. 

Close coordination among regulatory agencies, 

wetland scientists, and criteria experts will be 

required. 

(8/lSB4) 3-33 
Water Quality StadarJs tiandtxx)k - Second Edition 

cl 3.6 Policy on Aquatic Life Criteria for 

Metals 

It is the policy of the Office of Water that the use 

of dissolved metal to set and measure compliance 

with water quality standards is the recommended 

approach, because dissolved metal more closely 

approximates the bioavailable fraction of metal in 

the water column than does total recoverable 

metal. This conclusion regarding metals 

bioavailability is supported by a majority of the 

scientific community within and outside EPA. 

One reason is that a primary mechanism for water 

column toxicity is adsorption at the gill surface 

which requires metals to be in the dissolved form. 

Until the scientific uncertainties are better 

resolved, a range of different risk management 

decisions can be justified by a State. EPA 

recommends that State water quality standards be 

based on dissolved metal--a conversion factor 

must be used in order to express the EPA criteria 

articulated as total recoverable as dissolved. (See 

the paragraph below for technical details on 

developing dissolved criteria.) EPA will also 

approve a State risk management decision to adopt 

standards based on total recoverable metal, if 

those standards are otherwise approvable as a 

matter of law. (o$?ce (f Wurer Polity and 

Technicui Guidunc*e on Inteprerarion and 

Implemenrurion of Aquatic Lif4 Meruls Cri(eria 

USEPA, 1993f) 

3.6.1 Background 

The implementation of metals criteria is complex 

due to the site-specific nature of metals toxicity. 

This issue covers a number of areas including the 

expression of aquatic life criteria; total maximum 

daily loads (TMDLs), permits, effluent 

monitoring, and compliance; and ambient 

monitoring. The following Sections, based on the 

policy memorandum referenced above, provide 

additional guidance in each of these areas. 

Included in this Handbook as Appendix J are 

three guidance documents issued along with the 

Office of Water policy memorandum with 

additional technical &tails. They arc: (;rtitiurrcv 

Docwrrenr on Elrpw.\.vion of .4cprrc‘ l,if> C‘rilcjriu 

us I>issrh~ed C’rircrid (.Atta~~hmcrlt #Z), (;rridutrc.u 

Uocumenr on ll~numic* Mi dc*lin,q tlrui Trtrn.~Ifrror.s 

(Attachment #3). and (;uitfto~t~ I)oc~14m4~ru on 

Monitoring (Attachment #4). These will be 

supplement& as additional inti~rmation bcconles 

available. 

Since metals toxicity is significantly affected by 

site-specific factors, it presents a number of 

programmatic challenges. Factors that must be 

considered in the rnanagcment of metals in the 

aquatic environment include: toxicity specitic to 

effluent chemistry; toxicity specific to ambient 

water chemistry; different ptttcrns of toxicity for 

different metals; evolution oi the state of the 

science of metals toxicity. fate. ilnd transport; 

resource limitations for monitoring. analysis, 

implementation. and research functions; concerns 

regarding some of the analytical data currently on 

record due to possible sampling and analytical 

contamination; and lack of standardized protocols 

for clean and ultraclcan m&Is analysis. The 

States have the key role in the risk management 

process of balancing these factors in the 

management of water programs. The site-specific 

nature of this issue could he perceived as 

requiring a permit-hy-permit approach to 

implementation. Howc\.t’r. IFA belic\,es that this 

guidance can be cffcctively implemented on a 

broader level, across any w’ntcrs with roughly the 

same physical and chcrnrcal characteristics, and 

recommends that States work with the III’,4 with 

that perspctive in mind. 

3.6.2 Expression of Aquatic Life Criteria 

Dissolved vs. Total Hecovemhle .\letal 

A major issue is whether, and how, to use 

dissolved metal concentrations (“dissolved metal”) 

or total recoverable metal concentrations (“total 

recoverable metal”) III setting State water quality 

standards. In the past, States t1aL.c used both 

approaches when applying the same EPA Section 

304(a) criteria guidance. Some older criteria 

documents may have facilitated thcsc diifcrent 
Chapter 3 - Water Quality Cri~ria 

approaches to interpretation of the criteria because 

the documents were somewhat equivocal with 

regards to analytical methods. The May 1992 

interim guidance continued the policy that either 

approach was acceptable. 

The position that the dissolved metals approach is 

more accurate has been questioned because it 

neglects the possible toxicity of particulate metal. 

It is true that some studies have indicated that 

particulate metals appear to contribute to the 

toxicity of metals, perhaps because of factors such 

as desorption of metals at the gill surface, but 

these same studies indicate the toxicity of 

particulate metal is substantially less than that of 

dissolved metal. 

Furthermore, any error incurred from 

excluding the contribution of particulate metal will 

generally be compensated by other factors which 

make criteria conservative. For example, metals 

in toxicity tests are added as simple salts to 

relatively clean water. Due to the likely presence 

of a significant concentration of metals binding 

agents in many discharges and ambient waters, 

metals in toxicity tests would generally be 

expected to be more bioavailable than metals in 

discharges or in ambient waters. 

If total recoverable metal is used for the 

purpose of specifying water quality standards, the 

lower bioavailability of particulate metal and 

lower bioavailability of sorbed metals as they are 

discharged may result in an overly conservative 

water quality standard. The use of dissolved 

metal in water quality standards gives a more 

accurate result in the water column. However, 

total recoverable measurements in ambient water 

have value, in that exceedences of criteria on a 

total recoverable basis are an indication that metal 

loadings could be a stress to the ecosystem, 

particularly in locations other than the water 

column (e.g., in the sediments). 

The reasons for the potential consideration of total 

recoverable measurements include risk 

management considerations not covered by 

evaluation of water column toxicity alone. The 

ambient water quality criteria are neither designed 

nor intended to protect sediments, or to prevent 

effects in the food webs containing sediment 

dwelling organisms. A risk manager, however, 

may consider sediments and food chain effects 

and may decide to take a conservative approach 

for metals, considering that metals are very 

persistent chemicals. This conservative approach 

could include the use of total recoverable metal in 

water quality standards. However, since 

consideration of sediment impacts is not 

incorporated into the criteria methodology, the 

degree of conservatism inherent in the total 

recoverable approach is unknown. The 

uncertainty of metal impacts in sediments stem 

from the lack of sediment criteria and an 

imprecise understanding of the fate and transport 

of metals. EPA will continue to pursue research 

and other activities to close these knowledge gaps. 

Dissolved Cfiteriu 

In the toxicity tests used to develop EPA metals 

criteria for aquatic life, some fraction of the metal 

is dissolved while some fraction is bound to 

particulate matter. The present criteria were 

developed using total recoverable metal 

measurements or measures expected to give 

equivalent results in toxicity tests, and are 

articulated as total recoverable. Therefore, in 

order to express the EPA criteria as dissolved, a 

total recoverable to dissolved conversion factor 

must be used. Attachment #2 in Appendix J 

provides guidance for calculating EPA dissolved 

criteria from the published total recoverable 

criteria. The data expressed as percentage metal 

dissolved are presented as recommended values 

and ranges. However, the choice within ranges is 

a State risk management decision. EPA has 

recently supplemented the data for copper and is 

proceeding to further supplement the data for 

copper and other metals. As testing is completed, 

EPA will make this information available and this 

is expected to reduce the magnitude of the ranges 

for some of the conversion factors provided. 

EPA also strongly encourages the application of 

dissolved criteria across a watershed or 

(8115194) 3-35 
W8ter Quality Straduds Handback - Second Editiom 

water-body, as technically sound and the best use 

of resources. 

Site-Specfic Criteria ModQhtions 

While the above methods will correct some sitespecific factors affecting metals toxicity, further 

refinements are possible. EPA has issued 

guidance for three site-specific criteria 

development methodologies: recalculation 

procedure, water-effect ratio (WER) procedure 

(called the indicator species procedure in previous 

guidance) and resident species procedure. (See 

Section 3.7 of this Chapter.) 

In the National Toxics Rule (57 FR 60848, 

December 22, 1992), EPA recommended the 

WER as an optional method for site-specific 

criteria development for certain metals. EPA 

committed in the NTR preamble to provide 

additional guidance on determining the WERs. 

The Interim Guidance on rhe Determination and 

Use of Water-Eflect Rutios for MetaLr was issued 

by EPA on February 22, 1994 and is intended to 

fulfill that commitment. This interim guidance 

supersedes all guidance concerning water-effect 

ratios and the recalculation procedure previously 

issued by EPA. This guidance is included as 

Appendix L to this Handbook. 

In order to meet current needs, but allow for 

changes suggested by protocol users, EPA issued 

the guidance as “interim.” EPA will accept 

WERs developed using this guidance, as well as 

by using other scientifically defensible protocols. 

3.6.3 Total Maximum Daily Loads (TMDLs) 

and National Pollutant Discharge 

Elimination System (NPDES) Permits 

Dynamic Water Quaiity Modeling 

Although not specifically part of the reassessment 

of water quality criteria for metals, dynamic or 

probabilistic models are another useful tool for 

implementing water quality criteria, especially for 

those criteria protecting aquatic life. These 

models provide another way to incorporate sitespecific data. The Technical Suppn Document 

for Water Quulity-bused Toxics Conrrol (TSD) 

(USEPA, 1991a) describes dynamic, as well as 

static (steady-sbte) models. Dynamic models 

make the best use of the specified magnitude, 

duration, and frequency of water quality criteria 

and, therefore, provide a more accurate 

representation of the probability that a water 

quality standard exceedence will occur. In 

contrast, steady-state models frequently apply a 

number of simplifying, worst case assumptions 

which makes them less complex but also less 

accurate than dynamic models. 

Dynamic models have received increased attention 

over the last few years as a result of the 

widespread belief that steady-state modeling is 

over-conservative due to environmentally 

conservative dilution assumptions. This belief has 

led to the misconception that dynamic models will 

always lead to less stringent regulatory controls 

(e.g., NPDES effluent limits) than steady-state 

models, which is not true in every application of 

dynamic models. EPA considers dynamic models 

to be a more accurate approach to implementing 

water quality criteria and continues to recommend 

their use. Dynamic modeling does require a 

commitment of resources to develop appropriate 

data. (See Appendix J, Attachment #3 and the 

USEPA, 1991a for details on tht: use of dynamic 

models.) 

Dissolved-Total Metal Tmnsltlrors 

Expressing ambient water quality criteria for 

metals as the dissolved form of a metal poses a 

3-36 (8’15’94) 
Chaprer 3 - Warrr Quality Crirrria 

need to be able to translate from dissolved metal 

to total recoverable metal for TMDLs and 

NPDES permits. TMDLs for metals must be able 

to calculate: (1) dissolved metal in order to 

ascertain attainment of water quality standards, 

and (2) total recoverable metal in order to achieve 

mass balance necessary for permitting purposes. 

EPA’s NPDES regulations require that limits of 

metals in permits be stated as total recoverable in 

most cases (see 40 CFR #122.45(c)) except when 

an effluent guideline specifies the limitation in 

another form of the metal, the approved analytical 

methods measure only dissolved metal, or the 

permit writer expresses a metals limit in another 

form (e.g., dissolved, valent specific, or total) 

when required to carry out provisions of the 

Clean Water Act. This is because the chemical 

conditions in ambient waters frequently differ 

substantially from those in the effluent, and there 

is no assurance that effluent particulate metal 

would not dissolve after discharge. The NPDES 

rule does not require that State water quality 

standards be expressed as total recoverable; 

rather, the rule requires permit writers to translate 

between different metal forms in the calculation of 

the permit limit so that a total recoverable limit 

can be established. Roth the TMDL and NPDES 

uses of water quality criteria require the ability to 

translate between dissolved metal and total 

recoverable metal. Appendix J, Attachment #3 

provides guidance on this translation. 

3.6.4 Guidance on Monitoring 

Use of Clean Sampling and Analytical 

Techniques 

In assessing waterbodies to determine the potential 

for toxicity problems due to metals, the quality of 

the data used is an important issue. Metals data 

are used to determine attainment status for water 

quality standards, discern trends in water quality, 

estimate background loads for TMDLs, calibrate 

fate and transport models, estimate effluent 

concentrations (including effluent variability), 

assess permit compliance, and conduct research. 

The quality of trace level metal data, especially 

below 1 ppb, may be compromised due to 

contamination of samples during collection, 

preparation, storage, and analysis. Depending on 

the level of metal present, the use of “clean” and 

“ultraclean” techniques for sampling and analysis 

may be critical to accurate data for 

implementation of aquatic life criteria for metals. 

The significance of the sampling and analysis 

contamination problem increases as the ambient 

and effluent metal concentration decreases and, 

therefore, problems are more likely in ambient 

measurements. “Clean” techniques refer to those 

requirements (or practices for sample collection 

and handling) necessary to product reliable 

analytical data in the part per billion (ppb) range. 

“Ultraclean” techniques refer to those 

requirements or practices necessary to produce 

reliable analytical data in the part per trillion (ppt) 

range. Because typical concentrations of metals 

in surface waters and effluents vary from one 

metal to another, the effect of contamination on 

the quality of metals monitoring data varies 

appreciably. 

EPA plans to develop protocols on the use of 

clean and ultra-clean techniques and is 

coordinating with the United States Geological 

Survey (USGS) on this project, bccausc USGS has 

been doing work on these techniques for some 

time, especially the sampling proccdurcs. Draft 

protocols for clean tcchniqucs were presented at 

the Norfolk, VA analytical methods confcrcnce in 

the Spring of 1994 and final protocols are 

expected to be available in early 1995. The 

development of comparable protocols for ultraclean techniques is underway and are expected to 

be available in late 1995. In dr\,cloping these 

protocols, we will consider the costs of these 

techniques and will give guidance as to the 

situations where their use is necessary. Appendix 

L, pp. 98-108 provide some general guidance on 

the use of clean analytical tcchniqucs. We 

recommend that this guidance hc used by States 

and Regions as an interim step, while the clean 

and ultra-clean protocols are hcing dcicloped. 

(8!15/94) 3-37 
Water Oualrtv Standards Handbook - Second Ed&m 

Use of ~listoricd l&a 

The concerns about metals sampling and analysis 

discussed above raise corresponding concerns 

about the validity of historical data. Data on 

effluent and ambient metal concentrations are 

collected by a variety of organizations including 

Federal agencies (e.g., EPA, USGS), State 

pollution control agencies and health departments, 

local govern men t agencies, municipalities, 

industrial dischargers, researchers, and others. 

The data are collected for a variety of purposes as 

discussed above. 

Concern about the reliability of the sample 

collection and analysis procedures is greatest 

where they have been used to monitor very low 

level metal concentrations. Specifically, studies 

have shown data sets with contamination problems 

during sample collection and laboratory analysis, 

that have resulted in inaccurate measurements. 

For example, in developing a TMDL for New 

York Harbor. some historical ambient data 

showed extcnslve metals problems in the harbor, 

while other historical ambient data showed only 

limited metaIs problems. Careful resampling and 

analysis In 19921993 showed the Iatter view was 

correct. The key to producing accurate data is 

appropriate quality assurance (QA) and quality 

control (CJ‘) procedures. EPA believes that most 

historical data for metals, collected and analyzed 

with appropriate QA and QC at levels of 1 ppb or 

higher, are reliable. The data used in 

development of EPA criteria are also considered 

reliable, both because they meet the above test 

and because the toxicity test solutions are created 

by adding known amounts of metals. 

With respect to effluent monitoring reported by an 

NPDES permittee, the permittee is responsible for 

collecting and reporting quality data on a 

Discharge Monitoring Report (DMR). Permitting 

authorities should continue to consider the 

information reported to be true, accurate, and 

complete as certified by the permittee. Where the 

permittee becomes aware of new information 

specific to the effluent discharge that questions the 

quality of previously submitted DMR data, the 

permittee must promptly submit that information 

to the permitting authority. The permitting 

authority will consider all information submitted 

by the permittee in determining appropriate 

enforcement responses to monitoring/reporting 

and effluent violations. (See Appendix J, 

Attachment #4 for additional details.) 

cl 

3.7 Site-Specific Aquatic Life Criteria 

The purpose of this section is to provide guidance 

for the development of site-specific water quality 

criteria which reflect local environmental 

conditions. Site-specific criteria are allowed by 

regulation and are subject to EPA review and 

approval. The Federal water quality standards 

regulation at section 13 1.1 l(b)( l)(ii) provides 

States with the opportunity to adopt water quality 

criteria that are * . . . modified to reflect site-specific 

conditions. * Site-specific criteria, as with all 

water quality criteria, must be based on a sound 

scientific rationale in order to protect the 

designated use. Existing guidance and practice 

are that EPA will approve site-specific criteria 

developed using appropriate procedures. 

A site-specific criterion is intended to come closer 

than the national criterion to providing the 

intended level of protection to the aquatic life at 

the site, usually by taking into account the 

biological and/or chemical conditions (i.e., the 

species composition and/or water quality 

characteristics) at the site. The fact that the U.S. 

EPA has made these procedures available should 

not be interpreted as implying that the agency 

advocates that states derive site-specific criteria 

before setting state standards. Also, derivation of 

a site-specific criterion does not change the 

intended level of protection of the aquatic life at 

the site. 

3.7.1 History of Site-Specific Criteria 

Guidance 

National water quality criteria for aquatic life may 

be under- or over-protective if: 

3-38 (8115194) 
Chapter 3 - Water Qud+ Cruu-itI 

(1) the species at the site are more or less 

sensitive than those included in the national 

criteria data set (e.g., the national criteria 

data set contains data for trout, salmon, 

penaeid shrimp, and other aquatic species 

that have been shown to be especially 

sensitive to some materials), or 

(2) physical and/or chemical characteristics of 

the site alter the biological availability 

and/or toxicity of the chemical (e.g., 

alkalinity, hardness, pH, suspended solids 

and salinity influence the concentration(s) of 

the toxic form(s) of some heavy metals, 

ammonia and other chemicals). 

Therefore, it is appropriate that site-specific 

procedures address each of these conditions 

separately as well as the combination of the two. 

In the early 1980’s, EPA recognized that 

laboratory-derived water quality criteria might not 

accurately reflect site-specific conditions and, in 

response, created three procedures to derive sitespecific criteria. This Handbook contains the 

details of these procedures, referenced below. 

1. The Recalculation Procedure is intended to 

take into account relevant differences 

between the sensitivities of the aquatic 

organisms in the national dataset and the 

sensitivities of organisms that occur at the 

site (see Appendix L, pp. 90-97). 

2. The Water-Effect Ratio Procu (called the 

Indicator Species Procedure in USEPA, 

1983a; 1984f ) provided for the use of a 

water-effect ratio (WER) that is intended to 

take into account relevant differences 

between the toxicities of the chemical in 

laboratory dilution water and in site water 

(see Appendix L). 

3. The Resident ws Procedm intended to 

take into account both kinds of differences 

simultaneously (see Section 3.7.6). 

These procedures were first published in the 1983 

Water Quality Stundurds Handbook (USEPA, 

1983a) and expanded upon in the Guidelinasfor 

Deriving Numerical Aqua ric Site-SpeciJic Watt>r 

Quuiity Criteriu by Mtdfiing hlurionul Critcriu 

(USEPA, 1984f). Interest has increased in recent 

years as states have devoted more attention to 

chemical-specific water quality criteria for aquatic 

life. In addition, interest in water-effect ratios 

increased when they were integrated into some of 

the aquatic life criteria for metals that were 

promulgated for several states in the National 

Toxics Rule (57 E.B 60848. December 22, 1992). 

The Oflee of Water Policy and Technicul 

Guidance on Integwetarion and Implementation of 

Aquutic Lif4 Criteria for Metals (USEPA, 19930 

(see Section 3.6 of this Handbook) provided 

further guidance on site-specific criteria for metals 

by recommending the use of dissolved metals for 

setting and measuring compliance with water 

quality standards. 

The early guidance concerning WERs (USEPA, 

1983a; 1984f) contained few details and needed 

revision, especially to take into account newer 

guidance concerning metals. To meet this need, 

EPA issued Interim Guidunc-e on the 

Determination and Use of Water-Eflec.1 Rutios for 

Metals in 1994 (Appendix L). Metals are 

specifically addressed in Appendix L because of 

the National Toxics Rule and because of current 

interest in aquatic life criteria for metals; although 

most of this guidance also applies to other 

pollutants, some obviously applies only to metals. 

Appendix L supersedes a!1 guidance concerning 

water-effect ratios and the Indicator Species 

Procedure given in Chapter 4 of the Wuter 

Quality Stand&s Handbook (USEPA, l983a) and 

in Guidelinesfor Deriving h?unericul Aquutic SiteSpecljic Water Quuiity Criteriu by Mod@ing 

Nutional Criteria (USEPA, 1984f). Appendix I- 

(p. 90-98) also supersedes the guidance in these 

earlier documents for the Recalculation Procedure 

for performing site-specific criteria modifications. 

The Resident Species Procedure remains 

essentially unchanged since 1983 (except for 

changes in the averaging priods to conform to 

the 1985 aquatic life criteria guidelines (USEPA. 

198Sb) and is presented in Section 3.7.6, below. 

(8f15f94) 3-39 
Water Oual~tv Stan&r& Handbook - Second Edition 

The previous guidance concerning site-specific 

procedures did nor allow the Recalculation 

Procedure and the WER procedure to be used 

together in the derivation of a site-specific aquatic 

life criterion; the only way to take into account 

both species composition and water quality 

characteristics in the determination of a sitespecific criterion was to use the Resident Species 

Procedure. Acidic change contained Atgendk 

w excut in iurisdictions that are sm 

the National Toxics Rule. the Recalculation 

Procedure and the WER Procedure may now be 

ther provided that the recalculation 

procedure is performed first. Both the 

Recalculation Procedure and the WER Procedure 

are based directly on the guidelines for deriving 

national aquatic life criteria (USEPA 1985 ) and, 

when the two are used together, use of the 

Recalculation Procedure must be performed first 

because the Recalculation Procedure has specific 

implications concerning the determination of the 

WER. 

3.7.2 Preparing to Calculate Site-Specific 

Criteria 

Adopting site-specific criteria in water quality 

standards is a State option--not a requirement. 

Moreover, EPA is not advocating that States use 

site-specific criteria development procedures for 

setting all aquatic life criteria as opposed to using 

the National Section 304(a) criteria 

recommendations. Site-specific criteria are not 

needed in all situations. When a State considers 

the possibility of developing site-specific criteria, 

it is essential to involve the appropriate EPA 

Regional office at the start of the project. 

This early planning is also essential if it appears 

that data generation and testing may be conducted 

by a party other than the State or EPA. The State 

and EPA need to apply the procedures judiciously 

and must consider the complexity of the problem 

and the extent of knowledge available concerning 

the fate and effect of the pollutant under 

consideration. If site-specific criteria are 

developed without early EPA involvement in the 

planning and design of the task. the State may 

expect EPA to take additional time to closely 

scrutinize the results before granting any approval 

to the formally adopted standards. 

The following sequence of decisions need to be 

made before any of the procedures are initiated: 

+ verify that site-specific criteria are actually 

needed (e.g., that the use of clean sampling 

and/or analytical techniques, especially for 

metals, do not result in attainment of 

standards. ) 

+ Define the site boundaries. 

+ Determine from the national criterion 

document and other sources if physical 

and/or chemical characteristics are known to 

affect the biological availability and/or 

toxicity of a material of interest. 

+ If data in the national criterion document 

and/or from other sources indicate that the 

range of sensitivity of the selected resident 

species to the material of interest is different 

from the range for the species in the national 

criterion document, and variation in physical 

and/or chemical characteristics of the site 

water is not expected to be a factor, use the 

Reculmlurion Prowdure (Section 3.7.4). 

3-40 (8!15!94) 
Chuplcr 3 - Wtrwr Qdiry Critrria 

+ If data in the national criterion document 

and/or from other sources indicate that 

physical and/or chemical characteristics of 

the site water may affect the biological 

availability and/or toxicity of the material of 

interest, and the selected resident species 

range of sensitivity is similar to that for the 

species in the national criterion document, 

use the Wuter-E$Pct Ratio Procedure 

(Section 3.7-S). 

+ If data in the national criterion document 

and/or from other sources indicated that 

physical and/or chemical characteristics of 

the site water may affect the biological 

availability and/or toxicity of the material of 

interest, and the selected resident species 

range of sensitivity is different from that for 

the species in the national criterion 

document, and if both these differences are 

to be taken into account, use the 

Reculculwion Procedure in conjunction with 

the Wuter-E$ect Rutio Procedure or use the 

Resident Species Procedure (Section 3.7.6). 

3.7.3 Definition of a Site 

Since the rationales for site-specific criteria are 

usually based on potential differences in species 

sensitivity, physical and chemical characteristics 

of the water, or a combination of the two, the 

concept of site must be consistent with this 

rationale. 

In the general context of site-specific criteria, a 

“site” may be a state, region, watershed, 

water-body, or segment of a waterbody. The sitespecific criterion is to be derived to provide 

adequate protection for the entire site, however 

the site is defined. 

If water quality effects on toxicity are not a 

consideration, the site can be as large as a 

generally consistent biogeographic zone permits. 

For example, large portions of the Chesapeake 

Bay, Lake Michigan, or the Ohio River may be 

considered as one site if their respective aquatic 

communities do not vary substantially. However, 

when a site-specific criterion is derived using the 

Recalculation Procedure, all species that “occur at 

the site” need to be taken into account when 

deciding what species, if any, are to be deleted 

from the dataset. Unique populations or less 

sensitive uses within sites may justify a 

designation as a distinct site. 

If the species of a site are toxicologically 

comparable to those in the national criteria data 

set for a material of interest, and physical and/or 

chemical water characteristics are the only factors 

supporting modification of the national criteria, 

then the site can be defined on the basis of 

expected changes in the material’s biological 

availability and/or toxicity due to physical and 

chemical variability of the site water. However, 

when a site-specific criterion is derived using a 

WER, the WER is to be adequately protective of 

the entire site. If, for example. a site-specific 

criterion is being derived for an estuary, WERs 

could be determined using samples of the surface 

water obtained from various sampling stations, 

which, to avoid confusion, should not be called 

“sites”. If all the WERs were sufficiently similar, 

one site-specific criterion could be derived to 

apply to the whole estuary. If tht: WERs were 

sufficiently different, either the lowest WE,R could 

be used to derive a site-specific criterion for the 

whole estuary, or the data might indicate that the 

estuary should be divided into two or more sites, 

each with its own criterion. 

3.7.4 The Recalculation Procedure 

The Recalculation Procedure is intended to cause 

a site-specific criterion to appropriately differ 

from a national aquatic life criterion if justified by 

demonstrated pertinent toxicological differences 

between the aquatic species that occur at the site 

and those that were used in the derivation of the 

national criterion. There are at least three reasons 

why such differences might exist between the two 

sets of species. 

+ First, the national dataset contains aquatic 

species that are sensitive to many pollutants, 
Water &al~ty Standards Handbook - Second Edltlon 

but these and comparably sensitive species 

might not occur at the site. 

+ Second, a species that is critical at the site 

might be sensitive to the pollutant and 

require a lower criterion. (A critical species 

is a species that is commercially or 

recreationally important at the site, a species 

that exists at the site and is listed as 

threatened or endangered under section 4 of 

the Endangered Species Act, or a species for 

which there is evidence that the loss of the 

species from the site is likely to cause an 

unacceptable impact on a commercially or 

recreationally important species, a threatened 

or endangered species, the abundances of a 

variety of other species, or the structure or 

function of the community.) 

+ Third, the species that occur at the site 

might represent a narrower mix of species 

than those in the national dataset due to a 

limited range of natural environmental 

conditions. 

The procedure presented in Appendix L, pp. 90- 

98 is structured so that corrections and additions 

can be made to the national dataset without the 

deletion process being used to take into account 

taxa that do not occur at the site; in effect, this 

procedure makes it possible to update the national 

aquatic life criterion. All corrections and 

additions that have been approved by EPA are 

required, whereas use of the deletion process is 

optional. The deletion process may not be used 

to remove species from the criterion calculation 

that are not currently present at a site due to 

degraded conditions. 

The Recalculation Procedure is more likely to 

result in lowering a criterion if the net result of 

addition and deletion is to decrease the number of 

genera in the dataset. whereas the procedure is 

more likely to result in raising a criterion if the 

net result of addition and deletion is to increase 

the number of genera in the dataset. 

For the lipid soluble chemicals whose national 

Final Residue Values are based on Food and Drug 

Administration (FDA) action levels, adjustments 

in those values based on the percent lipid content 

of resident aquatic species is appropriate for the 

derivation of site-specific Final Residue Values. 

For lipid-soluble materials, the national Final 

Residue Value is based on an average I 1 percent 

lipid content for edible portions for the freshwater 

chinook salmon and lake trout and an average of 

10 percent lipids for the edible portion for 

saltwater Atlantic herring. Resident species of 

concern may have higher (e.g., Lake Superior 

siscowet, a race of lake trout) or lower (e.g., 

many sport fish) percent lipid content than used 

for the national Final Residue Value. 
Chapter 3 - Wufrr Qucdirv Criwrkr 

For some lipid-soluble materials such as 

polychlorinated biphenyls (PCB) and DDT, the 

national Final Residue Value is based on wildlife 

consumers of fish and aquatic invertebrate species 

rather than an FDA action level because the 

former provides a more stringent residue level. 

See the National Guidelines (USEPA, 1985b) for 

details. 

For the lipid-soluble materials whose national 

Final Residue Values are based on wildlife 

effects, the limiting wildlife species (mink for 

PCB and brown pelican for DDT) are considered 

acceptable surrogates for resident avian and 

mammalian species (e.g., herons, gulls, terns, 

otter, etc.) Conservatism is appropriate for those 

two chemicals, and no less restrictive modification 

of the national Final Residue Value is appropriate. 

The site-specific Final Residue Value would be 

the same as the national value. 

3.7.5 The Water-Effect Ratio (WER) 

Procedure 

The guidance on the Water-Effect Ratio Procedure 

presented in Appendix L is intended to produce 

WERs that may be used to derive site-specific 

aquatic life criteria from most national and state 

aquatic life criteria that were derived from 

laboratory toxicity data. 

As indicated in Appendix L, the 

determination of a water-effect ratio may require 

substantial resources. A discharger should 

consider cost-effective, preliminary measures 

described in this Appendix L (e.g., use of “clean” 

sampling and chemical analytical techniques 

especially for metals, or in non-NTR States, a 

recalculated criterion) to determine if an indicator 

species site-specific criterion is really needed. In 

many instances, use of these other meaSures may 

eliminate the need for deriving water-effect ratios. 

The methods described in the 1994 interim 

guidance (Appendix L) should be sufficient to 

develop site-specific criteria that resolve concerns 

of dischargers when there appears to be no 

instream toxicity but, where (a) a discharge 

appears to exceed existing or proposed water 

quality-based permit limits, or (b) an instream 

concentration appears to exceed an cxlsting or 

proposed water quality criterion. 

WERs obtained usinp the methods described in 

&pendix L should onlv be used to adjust aauatic 

. . 

life mena that were derived usinp laboratory 

toxicitv WERs determined using the 

methods described herein cannot be used to adjust 

the residue-based mercury Criterion Continuous 

Concentration (CCC) or the field-based selenium 

freshwater criterion. 

Except in jurisdictions that are subject to the 

NTR, the WERs may also be used with sitespecific aquatic life criteria that are derived using 

the Recalculation Procedure described in 

Appendix L (p.90). 

Water-wfect Ratios in the Detivafion of 

Site-Specfic C.lireti.0 

A central question concerning WIlRs is whether 

their use by a State results in a sitc-specific 

criterion subject to EPA review and approval 

under Section 303(c) of the Clean Water Act? 

Derivation of a water-effect ratio by a State is a 

site-specific criterion adjustment subject to EPA 

review and approval/disapproval under Section 

303(c). There are two options by w.hich this 

review can be accomplished. 

Option 1: 

A State may derive and submit each individual 

water-effect ratio determination to EPA ior review 

and approval. This would be accomplished 

through the normal review and revision process 

used by a State. 

Option 2: 

A State can amend its water quality standards to 

provide a formal procedure which includes 

derivation of water-effect ratios, appropriate 

definition of sites, and enforceable monitoring 

provisions to assure that designated uses are 

(8115194) 3-43 
Water Quality Standards Handtxmk - Second Edition 

protected. Both this procedure and the resulting 

criteria would be subject to full public 

participation requirements. EPA would review 

and approve/disapprove this protocol as a revised 

standard as part of the State’s triennial 

review/revision. After adoption of the procedure, 

public review of a site-specific criterion could be 

accomplished in conjunction with the public 

review required for permit issuance. For public 

information, EPA recommends that once a year 

the State publish a list of site-specific criteria. 

An exception to this policy applies to the waters 

of the jurisdictions included in the National 

Toxics Rule. The EPA review is not required for 

the jurisdictions included in the National Toxics 

Rule where EPA establishd the procedure for the 

State for application to the criteria promulgated. 

The National Toxics Rule was a formal 

rulemaking process (with notice and comment) in 

which EPA pre-authorized the use of a correctly 

applied water-effect ratio. That same process has 

not yet taken place in States not included in the 

National Toxics Rule. 

However, the National Toxics Rule does not 

affect State authority to establish scientifically 

defensible procedures to determine Federally 

authorized WERs. to certify those WERs in 

NPDFS permit proceedings, or to deny their 

application based on the State’s risk management 

analysis. 

As described in Section 12 1.36(b)(iii) of the water 

quality standards regulation (the official regulatory 

reference to the National Toxics Rule), the watereffect ratio is a site-specific calculation. As 

indicated on page 60866 of the preamble to the 

National Toxics Rule, the rule was constructed as 

a rebuttabIe presumption. The water-effect ratio is 

assigned a value of 1 .O until a different watereffect ratio is derived from suitable tests 

representative of conditions in the affected 

waterbody. It is the responsibility of the State to 

determine whether to rebut the assumed value of 

1 .O in the National Toxics Rule and apply another 

value of the water-effect ratio in order to establish 

a site-specific criterion. The site-specific criterion 

is then used to develop appropriate NPDES permit 

limits. The rule thus provides a State with the 

flexibility to derive an appropriate site-specific 

criterion for specific waterbodies. 

As a point of emphasis, although a water-effect 

ratio affects permit limits for individual 

dischargers, it is the State in all cases that 

determines if derivation of a site-specific criterion 

based on the water-effect ratio is allowed and it is 

the State that ensures that the calculations and 

data analysis are done completely and correctly. 

3.7.6 The Resident Species Procedure 

The resident Species Procedure for the derivation 

of a site-specific criterion accounts for differences 

in resident species sensitivity d differences in 

biological availability and/or toxicity of a material 

due to variability in physical and chemical 

characteristics of a site water. Derivation of the 

site-specific criterion maximum concentration 

(CMC) and site-specific criterion continuous 

concentration (CCC) are accomplished after the 

complete acute toxicity minimum datii set 

requirements have been met by conducting tests 

with resident species in site water. Chronic tests 

may also be necessary. This procedure is 

designed to compensate concurrently for any real 

differences between the sensitivity range of 

species represented in the national data set and for 

site water which may markedly affect the 

biological availability and/or toxicity of the 

material of interest. 

Certain families of organisms have bezn specified 

in the National Guidelines acute toxicity minimum 

data set (e.g., Salmonidae in fresh water and 

Penaeidae or Mysidae in salt water); if this or any 

other requirement cannot be met because the 

family or other group (e.g., insect or hcnthic 

crustacean) in fresh water is not represented by 

resident species, select a substitute(s) from a 

sensitive family represented by one or more 

resident species and meet the 8 family minimum 

data set requirement. If all the families at the site 

have been tested and the minimum data set 

requirements have not been met, use the most 
Chapter 3 - Water Oualim Crireria 

sensitive resident family mean acute value as the 

site-specific Final Acute Value. 

To derive the criterion maximum concentration 

divide the site-specific Final Acute Value by two. 

The site-specific Final Chronic Value can be 

obtained as described in the Appendix L. The 

lower of the site-specific Final Chronic Value (as 

described in the recalculation procedure - 

Appendix L, p. 90) and the recalculated sitespecific Final Residue Value becomes the sitespecific criterion continuous concentration unless 

plant or other data (including data obtained from 

the site-specific tests) indicates a lower value is 

appropriate. If a problem is identified, judgment 

should be used in establishing the site-specific 

criterion. 

The frequency of testing (e.g., the need for 

seasonal testing) will be related to the variability 

of the physical and chemical characteristics of site 

water as it is expected to affect the biological 

availability and/or toxicity of the material of 

interest. As the variability increases, the 

frequency of testing will increase. Many of the 

limitations djscussed for the previous two 

procedures would also apply to this procedure. 

Endnotes 

1. Proceedings in production. 

Contact: Ecological Risk Assessment Branch (4304) 

U.S. Environmental Protection Agency 

401 M Street, S.W. 

Washington, DC 20460 

Telephone (202) 260- 1940 

(8/15iW) 3-45 
Chapter 4 - Antidegradation 

CHAPTER 4 

ANTIDEGRADATION 

(40 CFR 131.12) 

Table of Contents 

4.1 History of Antidegradation .................................... 4-1 

4.2 Summary of the Antidegradation Policy ............................ 4-1 

4.3 State Antidegradation Requirements ............................... 4-2 

4.4 Protection of Existing Uses - 40 CFR 131.12(a)(1) ..................... 4-3 

4.4.1 Recreational Uses ................................... 4-4 

4.4.2 Aquatic Life/Wildlife Uses .............................. 4-5 

4.4.3 Existing Uses and Physical Modifications ..................... 4-5 

4.4.4 Existing Uses and Mixing Zones .......................... 4-6 

4.5 Protection of Water Quality in High-Quality Waters - 30 CFR 131.12(a)(2) ...... 4-6 

4.6 Applicability of Water Quality Standards to Nonpoint Sources Versus Enforceability 

of Controls ............................................. 4-9 

4.7 Outstanding National Resource Waters (ONRW) - 40 CFR 131.12(a)(3) ....... 4-10 

4.8 Antidegradation Application and Implementation ...................... 4-10 

4.8.1 Antidegradation, Load Allocation, Waste Load Allocation. Total Maximum 

Daily Load, and Permits .............................. 4-12 

4.8.2 Antidegradation and the Public Participation Process ............. 4-13