# Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants for the State of California

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## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** August 5, 1997
- **Citation:** 62 FR 42160

## Text

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[WH-FRL-5866-9]
RIN 2040-AC44

Water Quality Standards; Establishment of Numeric Criteria for
Priority Toxic Pollutants for the State of California

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: This rule proposes for the State of California, numeric water
quality criteria for priority toxic pollutants necessary to fulfill the
requirements of section 303(c)(2)(B) of the Clean Water Act (CWA) in
the State of California. This rule also proposes an authorizing
compliance schedule provision.
EPA is proposing this rule based on the Administrator's
determination that criteria are necessary in the State of California to
meet the requirements of CWA section 303(c)(2)(B). This section of the
CWA requires states to adopt numeric water quality criteria for
priority toxic pollutants for which EPA has issued CWA section 304(a)
criteria guidance and whose presence or discharge could reasonably be
expected to interfere with designated uses. Priority toxic pollutants
are identified in 40 CFR 131.36.
EPA is proposing this rule to fill a gap in California water
quality standards that was created in 1994 when a State Court
overturned the State's water quality control plans which contained
water quality criteria for priority toxic pollutants for which EPA had
issued CWA section 304(a) criteria guidance. Thus, the State of
California is currently without numeric water quality criteria for many
priority toxic pollutants as required by the CWA, necessitating this
action by EPA.
When these proposed federal criteria take effect, they will create
legally applicable water quality standards in the State of California
for inland surface waters, enclosed bays and estuaries for all purposes
and programs under the CWA.

DATES: All written comments received on or before September 26, 1997
will be considered in the preparation of the final rule. A public
hearing will be held on September 17, 1997, in San Francisco,
California, and on September 18, 1997, in Los Angeles, California. Both
oral and written comments will be accepted at the hearings.

ADDRESSES: Written comments should be addressed to Diane E. Frankel,
P.E., Esq., California Toxics Rule Project Manager, U.S. Environmental
Protection Agency, Region 9 (WTR-5), Water Management Division, 75
Hawthorne Street, San Francisco, California 94105.
Written comments are encouraged on paper or computer disk by mail.
Faxed comments will not be accepted. For comments on paper, an original
and two copies must be submitted. For computerized comments,
Wordperfect or ASCII format must be used. Comments previously submitted
for other Federal Register notices which are relevant to this notice
must be resubmitted in their entirety to be considered for this
proposed action.
A public hearing will be held at USEPA Region 9, 75 Hawthorne
Street, San Francisco, California, 94105, from 1-5 p.m. on September
17, 1997. A public hearing will also be held at the Los Angeles
Department of Water and Power, 111 North Hope Street, Los Angeles,
California, 90012, from 1-5 p.m. on September 18, 1997.
The public may inspect the administrative record for this
rulemaking, including documentation supporting the aquatic life and
human health criteria, at the U.S. Environmental Protection Agency,
Region 9, Water Management Division, 75 Hawthorne Street, San Francisco
94105 (telephone: 415-744-2125) on weekdays during the Agency's normal
business hours of 8:00 a.m. to 4:30 p.m. A reasonable fee will be
charged for photocopies.

FOR FURTHER INFORMATION CONTACT: Diane E. Frankel, P.E., Esq. or Philip
Woods, U.S. Environmental Protection Agency, Region 9 (WTR-5), Water
Management Division, 75 Hawthorne Street, San Francisco, California
94105, 415-744-2004 or 415-744-1997, respectively.

SUPPLEMENTARY INFORMATION: This preamble is organized according to the
following outline:

A. Introduction and Overview
1. Introduction
2. Overview
B. Statutory and Regulatory Background
C. State of California Actions and Compliance Regarding Section
303(c)(2)(B) of the Clean Water Act (CWA)
1. California Regional Water Quality Control Board Basin Plans,
and the Inland Surface Waters Plan (ISWP) and the Enclosed Bays and
Estuaries Plan (EBEP) of April 1991
2. EPA's Review of California Water Quality Standards for
Priority Toxic Pollutants in the ISWP and EBEP, and the National
Toxics Rule
3. Status of Implementation of CWA Section 303(c)(2)(B)
4. State-Adopted Site-Specific Priority Toxic Pollutant Criteria
D. Rationale and Approach For Developing the Proposed Rule
1. Legal Basis
2. Approach for Developing the Proposed Rule
E. Derivation of Criteria
1. Section 304(a) Criteria Guidance Process
2. Aquatic Life Criteria
a. Freshwater Criteria
b. Freshwater Acute Selenium Criterion
c. Dissolved Metals Criteria
d. Application of Metals Criteria
e. Saltwater Copper Criteria
f. Chronic Averaging Period
g. Hardness
3. Human Health Criteria
a. 2,3,7,8-TCDD (Dioxin) Criteria
b. Arsenic Criteria
c. Mercury Criteria
d. Polychlorinated Biphenyls (PCBs) Criteria
e. Section 304(a) Human Health Criteria Excluded
f. Cancer Risk Level
F. Description of the Proposed Rule
1. Scope
2. EPA Criteria for Priority Toxic Pollutants
3. Implementation
4. Wet Weather Flows
5. Schedules of Compliance
G. Executive Order (E.O.) 12866, Regulatory Planning and Review
1. Baselines
2. Costs
3. Benefits
H. Executive Order (E.O.) 12875, Enhancing the Intergovernmental
Partnership
I. The Unfunded Mandates Reform Act of 1995
J. The Regulatory Flexibility Act
K. The Paperwork Reduction Act
L. The Endangered Species Act

Potentially Affected Entities: Citizens concerned with water
quality in California may be interested in this rulemaking. Entities
discharging pollutants to waters of the United States in California
could be indirectly affected by this rulemaking since water quality
criteria are used to create water quality standards which in turn are
used in developing National Pollutant Discharge Elimination System
(NPDES) permit limits. Categories and entities which may ultimately be
indirectly affected include:

------------------------------------------------------------------------
Examples of potentially
Category indirectly affected entities
------------------------------------------------------------------------
Industry............................... Industries discharging
pollutants to surface waters
in California.
Municipalities......................... Publicly-owned treatment works
discharging pollutants to
surface waters in California.
------------------------------------------------------------------------

[[Page 42161]]

This table is not intended to be exhaustive, but rather provides a
guide for readers regarding NPDES regulated entities likely to be
indirectly affected by this action. This table lists the types of
entities that EPA is now aware could potentially be indirectly affected
by this action. If you have questions regarding this section consult
the person listed in the preceding FOR FURTHER INFORMATION CONTACT
section.

A. Introduction and Overview

1. Introduction

This section of the preamble introduces the topics which are
addressed below and provides a brief overview of EPA's basis and
rationale for proposing federal criteria for the State of California.
Section B briefly describes the evolution of the efforts to control
toxic pollutants; these efforts include the changes enacted in the 1987
CWA Amendments which are the basis for this rule. Section C summarizes
California's efforts since 1987 to implement the requirements of CWA
section 303(c)(2)(B) and describes EPA's procedure and actions for
determining whether California has fully implemented CWA section
303(c)(2)(B). Section D provides the rationale and approach for
developing the proposed rule, including a discussion of EPA's legal
basis for this proposal. Section E describes the development of the
criteria included in this rule. Section F summarizes the provisions of
the proposed rule and discusses implementation issues. Sections G, H,
I, J, K, and L briefly address the requirements of Executive Orders
12866 and 12875, the Unfunded Mandates Reform Act of 1995, the
Regulatory Flexibility Act, the Paperwork Reduction Act, and the
Endangered Species Act, respectively.
Since detailed information concerning many of the topics in this
preamble was published previously in the Federal Register in preambles
for other rulemakings, references are frequently made to those
preambles. Those rulemakings include: Water Quality Standards;
Establishment of Numeric Criteria for Priority Toxic Pollutants, 57 FR
60848, December 22, 1992 (referred to as the National Toxics Rule or
NTR); and the NTR as amended by Administrative Stay of Federal Water
Quality Criteria for Metals and Interim Final Rule, Water Quality
Standards; Establishment of Numeric Criteria for Priority Toxic
Pollutants; States' Compliance--Revision of Metals Criteria, 60 FR
22228, May 4, 1995 (referred to as the National Toxics Rule [NTR], as
amended). The NTR, as amended, is codified at 40 CFR 131.36. A copy of
the NTR, as amended, and its preambles are contained in the
administrative record for this rulemaking.

2. Overview

This proposed rule would establish ambient water quality criteria
for priority toxic pollutants in the State of California. The criteria
in this proposal would supplement the water quality criteria
promulgated for California in the NTR, as amended. In 1991, EPA
approved a number of water quality criteria (discussed in section C,
below), for the State of California. Since EPA had approved these
criteria, it was not necessary to include them in the NTR. However, the
EPA-approved criteria were subsequently invalidated in State
litigation. Thus, this proposal contains criteria to fill the gap
created by the State litigation.
This proposed rule does not change or supersede any criteria
previously promulgated for the State of California in the NTR, as
amended. Criteria which EPA promulgated for California in the NTR, as
amended, are footnoted in the proposed table at 131.38(b)(1), so that
when this proposed rule is promulgated, readers may see the criteria
promulgated in the NTR, as amended, for California and the criteria
promulgated through this rulemaking for California in the same table.
This proposed rule is not intended to apply to waters within Indian
Country. EPA recognizes that there are possibly waters located wholly
or partly in Indian Country that are included in the State's basin
plans. EPA will work with the State and Tribes to identify any such
waters and to seek comment from those entities on whether EPA should
include those waters in the final rulemaking or take other actions to
protect water quality in Indian Country. EPA also solicits comment from
the public on this approach.
This rule is important for several environmental, programmatic and
legal reasons. Control of toxic pollutants in surface waters is
necessary to achieve the CWA's goals and objectives. Many of
California's monitored river miles, lake acres, and estuarine waters
have elevated levels of toxic pollutants. Recent studies on California
water bodies indicate that elevated levels of toxic pollutants exist in
fish tissue which result in fishing advisories or bans. These toxic
pollutants can be attributed to, among other sources, industrial and
municipal discharges.
Water quality standards for toxic pollutants are important to State
and EPA efforts to address water quality problems. Clearly established
water quality goals enhance the effectiveness of many of the State's
and EPA's water programs including permitting, coastal water quality
improvement, fish tissue quality protection, nonpoint source controls,
drinking water quality protection, and ecological protection. Numeric
criteria for toxic pollutants allow the State and EPA to evaluate the
adequacy of existing and potential control measures to protect aquatic
ecosystems and human health. Numeric criteria also provide a more
precise basis for deriving water quality-based effluent limitations in
National Pollutant Discharge Elimination System (NPDES) permits to
control toxic pollutant discharges. Congress recognized these issues
when it enacted section 303(c)(2)(B) to the CWA.
While California recognizes the need for applicable water quality
standards for toxic pollutants, its adoption efforts have been stymied
by a variety of factors. The Administrator has determined that it must
exercise its CWA authorities to move forward the toxic control program,
consistent with the CWA and with the State of California's water
quality standards program.
EPA's action will also help restore equity among the states. The
CWA is designed to ensure all waters are sufficiently clean to protect
public health and/or the environment. The CWA allows some flexibility
and differences among states in their adopted and approved water
quality standards, but it should be implemented in a manner that
ensures a level playing field among states. Although California has
made important progress toward satisfying CWA requirements, it has not
satisfied CWA section 303(c)(2)(B) by adopting water quality standards
for toxic pollutants. This section was added to the CWA by Congress in
1987. The State of California is the only state in the Nation for which
CWA section 303(c)(2)(B) remains substantially unimplemented after
EPA's promulgation of the NTR in December of 1992. Section 303(c)(4) of
the CWA authorizes the EPA Administrator to promulgate standards where
necessary to meet the requirements of the Act. EPA has determined that
this rule is a necessary and important component for the implementation
of CWA section 303(c)(2)(B) in California.
EPA acknowledges that the State of California is working to satisfy
CWA section 303(c)(2)(B). When the State formally adopts criteria
consistent with its statutory requirements, as envisioned by Congress
in the CWA, EPA will act to stay its rule. When any judicial

[[Page 42162]]

review of such State standards is complete and sustains the State
standards, EPA will act to withdraw its rule.

B. Statutory and Regulatory Background

Section 303(c) of the 1972 Federal Water Pollution Control Act
Amendments (FWPCA) established the statutory basis for the current
water quality standards program. Although the major innovation of the
1972 FWPCA was technology-based controls, Congress maintained the
concept of water quality standards both as a mechanism to establish
goals for the Nation's waters and as a regulatory requirement when
standardized technology controls for point source discharges and/or
nonpoint source controls were inadequate.
Another major innovation in the 1972 FWPCA was the establishment of
the National Pollutant Discharge Elimination System (NPDES) which
requires point source dischargers to obtain a permit before legally
discharging to waters of the United States. In addition to the permit
limits established on the basis of technology (e.g. effluent
limitations guidelines), the Act requires permits to include more
stringent limits as necessary to meet instream water quality standards.
See CWA section 301(b)(1)(C).
Water quality standards are comprised of designated uses, criteria
to meet those uses, and an antidegradation policy. Water quality
standards serve two main functions: they allow for assessment of water
quality in a water body and they provide a basis for determining what
effluent discharge limitations may be allowed in order to protect the
designated uses of the water body.
In its initial efforts to control toxic pollutants, the FWPCA,
pursuant to section 307, required EPA to designate a list of toxic
pollutants and to establish toxic pollutant effluent standards based on
a formal rulemaking record. Such rulemaking required formal hearings.
EPA struggled with this unwieldy process and ultimately promulgated
effluent standards for six toxic pollutants, pollutant families or
mixtures. See 40 CFR Part 129. Congress amended section 307 in the 1977
CWA Amendments by endorsing the Agency's alternative procedure of
regulating toxic pollutants by use of technology-based effluent
limitations guidelines for toxic pollutants, by amending the procedure
for establishing toxic pollutant effluent standards to provide for more
flexibility in the hearing process for establishing a record, and by
directing the Agency to include sixty-five specific pollutants or
classes of pollutants on the toxic pollutant list. EPA published the
required list on January 31, 1978 (43 FR 4109). This toxic pollutant
list was the basis on which EPA focused its efforts on criteria
development for toxic pollutants.
EPA selected key chemicals of concern within the sixty-five
families of pollutants and identified a more specific list of 129
priority toxic pollutants. Two volatile chemicals and one water
unstable chemical were removed from the list (see 46 FR 2266, January
8, 1981; 46 FR 10723, February 4, 1981), so that at present, there are
126 priority toxic pollutants. This list appears in 40 CFR 131.36.
Another critical section of the 1972 FWPCA was section 304(a). CWA
section 304(a)(1) provides, in part, that EPA develop and publish
criteria guidance for water quality reflecting the latest scientific
knowledge on the kind and extent of all identifiable effects on health
and welfare including, but not limited to, plankton, fish, shellfish,
wildlife, plant life, shorelines, beaches, esthetics, and recreation
which may be expected from the presence of pollutants, and on the
effects of pollutants on biological community diversity, productivity,
etc.
In order to avoid confusion, it must be recognized that the CWA
uses the term ``criteria'' in two separate ways. In CWA section 303(c),
which is discussed above, the term is part of the definition of a water
quality standard. That is, a water quality standard is comprised of
designated uses and the criteria necessary to protect those uses. The
term ``criteria'' refers to the ambient component of the water quality
standard contained in state or federal law. However, CWA section
304(a)(1) directs EPA to publish water quality ``criteria'' guidance
which encompass scientific assessments of the health and ecological
effects of various pollutants listed pursuant to CWA section 307(a)(1)
and which are used to support development of ambient criteria as part
of water quality standards. CWA section 304(a) criteria guidance are
intended as guidance only and have no binding effect. States may
consider these criteria guidance in adopting regulatory criteria.
To implement CWA section 304(a)(1), EPA initially produced a series
of scientific water quality criteria guidance documents. EPA's most
recently published criteria documents are summarized in one document
entitled, Quality Criteria for Water 1986 (1986 ``Gold Book''). EPA has
updated many of the criteria since publication of the 1986 Gold Book.
EPA's criteria guidance (both the earlier documents and updates
including those in the Agency's Integrated Risk Information System
[IRIS]), provide a comprehensive toxicological evaluation of each
chemical and the individual criteria recommendations, as updated, are
the official guidance. For toxic pollutants, the recommendations
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)
which the Agency recommends to protect aquatic life resources. For
human health criteria, the recommendations provide the appropriate
reference doses, and if appropriate, the carcinogenic slope factors,
and derives recommended criteria. The details of this process are
discussed in a later part of this preamble.
Criteria documents, along with any more recent scientific data and
information, may be used to interpret a state's narrative criterion
pursuant to 40 CFR 122.44(d)(1)(vi), and serve to establish State and
EPA permit discharge limits pursuant to CWA section 301(b)(1)(C) which
requires NPDES permits to contain limitations required to implement any
applicable water quality standard established in the CWA.
In support of the November, 1983 water quality standards
rulemaking, EPA issued program guidance entitled, Water Quality
Standards Handbook (December 1983) simultaneously with the publication
of the final rule. The forward to that guidance noted EPA's two-fold
water quality based approach to controlling toxic pollutants: chemical
specific numeric criteria and biological testing in whole effluent or
ambient waters to comply with narrative ``no toxics in toxic amounts''
standards. More detailed programmatic guidance on the application of
biological testing was provided in the Technical Support Document for
Water Quality-Based Toxics Control (TSD) (EPA 440/4-85-032, September
1985). This document provided the needed information to convert
chemical specific and biologically based criteria into water quality
standards for ambient receiving waters and permit limits for discharges
to those waters. The TSD focused on the use of toxicity testing of
effluent (whole effluent testing or WET methods) to develop effluent
limitations within discharge permits. Such effluent limits were
designed to implement the ``free from toxicity'' narrative standards in
state water quality standards. The TSD also focused on water quality
standards. Procedures and policy were presented

[[Page 42163]]

for appropriate design flows for EPA's section 304(a) acute and chronic
criteria. In 1991, EPA revised and expanded the TSD. (Technical Support
Document for Water Quality-Based Toxics Control (TSD), (EPA 505/2-90-
001, March 1991).) A notice of availability was published in the
Federal Register on April 4, 1991 (56 FR 13827). All references in this
preamble are to the revised TSD.
In 1987, Congress enacted stringent new water quality standard
provisions in the Water Quality Act amendments. The 1987 Amendments to
the CWA (P.L. 100-4) added section 303(c)(2)(B) which provides:

Whenever a State reviews water quality standards pursuant to
paragraph (1) of this subsection, or revises or adopts new standards
pursuant to this paragraph, 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 (1), 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 methods or previously adopted numerical
criteria.

The addition of this new requirement to the existing water quality
standards review and revision process of CWA section 303(c) did not
change the existing procedural or timing provisions. CWA section
303(c)(1) still required that states review their water quality
standards at least once each three year period and transmit the results
to EPA for review. EPA's oversight and promulgation authorities and
statutory schedules in CWA section 303(c)(4) were likewise unchanged.
Rather, the provision required the states to place heavy emphasis on
adopting numeric chemical-specific criteria for toxic pollutants
(rather than narrative approaches) during the next triennial review.
Congress was frustrated that states were not using the numerous CWA
section 304(a) criteria guidance that EPA had and was continuing to
develop, to assist states in controlling the discharge of priority
toxic pollutants. Accordingly, Congress explicitly mandated that states
adopt numeric criteria for toxic pollutants where the discharge or
presence of such pollutants could reasonably be expected to interfere
with such designated uses.
In response to this requirement, EPA strengthened its efforts to
assist state adoption of water quality standards for priority toxic
pollutants. This included developing and issuing guidance for states on
acceptable implementation procedures for several new sections of the
CWA, including sections 303(c)(2)(B) and 304(l). EPA, in devising
guidance for CWA section 303(c)(2)(B), attempted to provide states the
maximum flexibility that complied with the express statutory language
but also with the overriding Congressional objective: Prompt adoption
and implementation of numeric toxic pollutant criteria where necessary
to protect designated uses. EPA believed that flexibility was important
so that each state could satisfy CWA section 303(c)(2)(B) and to the
extent possible, accommodate its existing water quality standards
regulatory approach. EPA's program guidance was issued in final form on
December 12, 1988 and the availability of the guidance was published in
a Federal Register notice on January 5, 1989 (54 FR 346).
EPA's section 303(c)(2)(B) program guidance identified several
options that could be used by a state to meet the requirement that the
state adopt toxic pollutant criteria ``* * *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.'' These options are fully discussed in
the guidance and in the preamble to the National Toxics Rule (NTR) at
57 FR 60853. One option is for a state to adopt statewide numeric
criteria for all section 307(a) toxic pollutants for which EPA has
developed section 304(a) criteria guidance, regardless of whether the
pollutants are known to be present. This option is the most
comprehensive approach to satisfy the statutory requirement, and
ensures comprehensive coverage of the priority toxic pollutants with
scientifically defensible criteria. This option would not impose more
effluent limits on dischargers than any other option, because permit
limits would only be based on the regulation of the particular toxic
pollutants in their discharge and not on the total listing in the water
quality standards. Actual permit limits should be the same under any
option.
EPA's December 1988 guidance also stated that all state standards
triennial reviews initiated after passage of the amended CWA must
include a consideration of numeric toxic criteria.
Beyond the increased Congressional and public concern about the
relative importance of toxic pollutant controls, there was increased
evidence of toxic pollution problems in our Nation's waters. In
response, in 1992, EPA promulgated the NTR pursuant to CWA section
303(c)(4)(B) and 40 CFR 131.22(b) to rectify program deficiencies in 14
states, including the State of California. The State of California was
included for specific pollutants and for specific water bodies which
corresponded with EPA's disapproval in November 1991 of a portion of
each of two statewide plans. EPA did not promulgate criteria for those
portions of the statewide plans which it approved.
Today's action proposes to add priority toxic pollutant criteria
applicable to inland surface waters, enclosed bays and estuaries within
the State of California.

C. State of California Actions and Compliance Regarding Section
303(c)(2)(B) of the Clean Water Act (CWA)

1. California Regional Water Quality Control Board Basin Plans, and the
Inland Surface Waters Plan (ISWP) and the Enclosed Bays and Estuaries
Plan (EBEP) of April 1991

The State of California regulates water quality through its State
Water Resource Control Board (SWRCB) and through nine Regional Water
Quality Control Boards (RWQCBs). Each of the nine RWQCBs represents a
different geographic area; area boundaries are generally along
watershed boundaries. Each RWQCB maintains a Basin Plan which contains
the designated uses of the water bodies within its respective
geographic area within California. These designated uses (or
``beneficial uses'' under State law) together with legally-adopted
criteria (or ``objectives'' under State law), comprise water quality
standards for the water bodies within each of the Basin areas. Each of
the nine RWQCBs undergoes a triennial Basin Planning review process, in
compliance with CWA section 303. The SWRCB provides assistance to the
RWQCBs.
Most of the Basin Plans contain conventional pollutant objectives
such as dissolved oxygen. None of the Basin Plans contains a
comprehensive list of priority toxic pollutant criteria to satisfy CWA
section 303(c)(2)(B). The nine RWQCBs and the SWRCB had intended that
the priority toxic pollutant criteria contained in the three SWRCB
statewide plans, the Inland Surface Water Plan (ISWP), the Enclosed Bay
and Estuary

[[Page 42164]]

Plan (EBEP), and the Ocean Plan, apply to all Basins and satisfy CWA
section 303(c)(2)(B).
On April 11, 1991, the SWRCB adopted two statewide water quality
control plans, the ISWP and the EBEP. These statewide plans contained
narrative and numeric water quality criteria for toxic pollutants, in
part to satisfy CWA section 303(c)(2)(B). The water quality criteria
contained in the SWRCB statewide plans, together with the designated
uses in each of the Basin Plans, created a set of water quality
standards for waters within for the State of California.
Specifically, the two plans established water quality criteria or
objectives for all fresh waters, bays and estuaries in the State. The
plans contained water quality criteria for some priority toxic
pollutants, provisions relating to whole effluent toxicity,
implementation procedures for point and nonpoint sources, and
authorizing compliance schedule provisions. The plans also included
special provisions affecting waters dominated by reclaimed water
(labeled as Category (a) waters), and waters dominated by agricultural
drainage and constructed agricultural drains (labeled as Category (b)
and (c) waters, respectively).

2. EPA's Review of California Water Quality Standards for Priority
Toxic Pollutants in the ISWP and EBEP, and the National Toxics Rule

The EPA Administrator has delegated the responsibility and
authority for review and approval or disapproval of all new or revised
state water quality standards to the EPA Regional Administrators (see
40 CFR 131.21). Thus, state actions under CWA section 303(c)(2)(B) are
submitted to the appropriate EPA Regional Administrator for review and
approval.
In mid-April 1991, the SWRCB submitted to EPA for review and
approval the two statewide water quality control plans--the ISWP and
the EBEP. On November 6, 1991, EPA Region 9 formally concluded its
review of the SWRCB's plans. EPA approved the narrative water quality
criterion and the toxicity criterion in each of the plans. EPA also
approved the numeric water quality criteria contained in both plans,
finding them to be consistent with the requirements of section
303(c)(2)(B) of the CWA and with EPA's national criteria guidance
published pursuant to section 304(a) of the CWA.
EPA noted the lack of criteria for some pollutants, and found that,
because of the omissions, the plans did not fully satisfy CWA section
303(c)(2)(B). The plans did not contain criteria for all listed
pollutants for which EPA had published national criteria guidance. The
ISWP contained human health criteria for only 65 pollutants, and the
EBEP contained human health criteria for only 61 pollutants for which
EPA had issued section 304(a) guidance criteria. Both the ISWP and EBEP
contained aquatic life criteria for all pollutants except cyanide and
chromium III (freshwater only) for which EPA has CWA section 304(a)
criteria guidance. The SWRCB's administrative record stated that all
priority pollutants with EPA criteria guidance were likely to be
present in California waters. However, the SWRCB's record contained
insufficient information to support a finding that the excluded
pollutants were not reasonably expected to interfere with designated
uses of the waters of the State.
Although EPA approved the statewide selenium objective in the ISWP
and EBEP, EPA disapproved the criteria for the San Francisco Bay and
Delta, because there was clear evidence that the criteria would not
protect the designated fish and wildlife uses (the California
Department of Health Services had issued waterfowl consumption
advisories due to selenium concentrations, and scientific studies had
documented selenium toxicity to fish and wildlife). EPA restated its
commitment to object to National Pollutant Discharge Elimination System
(NPDES) permits issued for San Francisco Bay that contained effluent
limits based on an objective greater than 5 ppb (four day average) and
20 ppb (1 hour average), the freshwater criteria. EPA reaffirmed its
disapproval of site-specific selenium criteria for portions of the San
Joaquin River, Salt Slough, and Mud Slough. EPA also disapproved of the
categorical deferrals and exemptions. These disapprovals included the
disapproval of the State's deferral of water quality objectives to
effluent dominated streams (Category a) and to streams dominated by
agricultural drainage (Category b), and the disapproval of the
exemption of water quality objectives to constructed agricultural
drains (Category c). EPA found the definitions of the categories
imprecise and overly broad which could have led to an incorrect
interpretation.
Since EPA had disapproved portions of each of the California
statewide plans which were necessary to satisfy CWA section
303(c)(2)(B), California was included in EPA's promulgation of the
National Toxics Rule (NTR) (40 CFR 131.36, 57 FR 60848). EPA
promulgated specific criteria for certain water bodies in California.
The NTR was amended, effective April 14, 1995, to stay certain
metals criteria which had been promulgated as total recoverable;
effective April 15, 1995, EPA promulgated interim final metals criteria
as dissolved concentrations for those metals which had been stayed
(Administrative Stay of Federal Water Quality Criteria for Metals and
Interim Final Rule, Water Quality Standards; Establishment of Numeric
Criteria for Priority Toxic Pollutants; States' Compliance--Revision of
Metals Criteria; 60 FR 22228, May 4, 1995 [the NTR, as amended]). The
stay was in response to a lawsuit against EPA challenging, among other
issues, metals criteria expressed as total recoverable concentrations.
A partial Settlement Agreement required EPA to stay specific metals
criteria in the NTR. EPA then promulgated certain metals criteria in
the dissolved form through the use of conversion factors. These factors
are listed in the NTR, as amended. A scientific discussion of these
criteria is found in the next section.
Since certain criteria have already been promulgated for specific
water bodies in the State of California in the NTR, as amended, they
are not within the scope of today's proposed rule. However, for clarity
in reading a comprehensive rule for the State of California, these
criteria are incorporated in proposed 40 CFR 131.38(d)(2). Footnotes to
the Table in proposed 40 CFR 131.38(b)(1) and proposed 40 CFR
131.38(d)(3) clarify which criteria (and for which specific water
bodies) have been promulgated by the NTR, as amended, and are therefore
excluded from this proposed rule. The appropriate (freshwater or
saltwater) aquatic life criteria which were promulgated in the NTR, as
amended, for all inland surface waters and enclosed bays and estuaries
include: chromium III and cyanide. The appropriate (water and organism
or organism only) human health criteria which were promulgated in the
NTR, as amended, for all inland surface waters and enclosed bays and
estuaries include: antimony; thallium; asbestos; acrolein;
acrylonitrile; carbon tetrachloride; chlorobenzene; 1,2-dichloroethane;
1,1-dichloroethylene; 1,3-dichloropropylene; ethylbenzene; 1,1,2,2-
tetrachloroethane; tetrachloroethylene; 1,1,2-trichloroethane;
trichloroethylene; vinyl chloride; 2,4-dichlorophenol; 2-methyl-4,6-
dinitrophenol; 2,4-dinitrophenol; benzidine; bis(2-chloroethyl)ether;
bis(2-ethylhexyl)phthalate; 3,3-dichlorobenzidine; diethyl phthalate;

[[Page 42165]]

dimethyl phthalate; di-n-butyl phthalate; 2,4-dinitrotoluene; 1,2-
diphenylhydrazine; hexachlorobutadiene; hexachlorocyclopentadiene;
hexachloroethane; isophorone; nitrobenzene; n-nitrosodimethylamine; and
n-nitrosodiphenylamine. Other pollutant criteria were promulgated in
the NTR, as amended, for specific water bodies, but not all inland
surface waters and enclosed bays and estuaries.

3. Status of Implementation of CWA Section 303(c)(2)(B)

Shortly after the SWRCB adopted the ISWP and EBEP, several
dischargers filed suit against the State alleging that it had not
adopted the two plans in compliance with State law. The plaintiffs in a
consolidated case included: the County of Sacramento, Sacramento County
Water Agency; Sacramento Regional County Sanitation District; the City
of Sacramento; the City of Sunnyvale; the City of San Jose; the City of
Stockton; and Simpson Paper Company.
The dischargers alleged that the State had not adopted the ISWP and
EBEP in compliance with the California Administrative Procedures Act
(Gov Code. Section 11340, et seq.), the California Environmental
Quality Act (Pub. Re Code, Section 21000, et seq.), and the Porter-
Cologne Act (Wat. Code, Section 13200, et seq.). The allegation that
the State did not sufficiently consider economics when adopting water
quality objectives, as allegedly required by Section 13241 of the
Porter Cologne Act, was an important issue in the litigation.
In October of 1993, the Superior Court of California, County of
Sacramento, issued a tentative decision in favor of the dischargers. In
March of 1994, the Court issued a substantively similar final decision
in favor of the dischargers. Final judgments from the Court in July of
1994 ordered the SWRCB to rescind the ISWP and EBEP. On September 22,
1994, the SWRCB formally rescinded the two statewide water quality
control plans. The State is currently in the process of readopting
water quality control plans for inland surface waters, enclosed bays
and estuaries.
CWA section 303(c)(2)(B) was fully implemented in the State of
California from December of 1992, when the NTR was promulgated, until
September of 1994, when the SWRCB was required to rescind the ISWP and
EBEP. The provisions for California in EPA's NTR together with the
approved portions of California's ISWP and EBEP implemented the
requirements of CWA section 303(c)(2)(B). However, since September of
1994, when the SWRCB rescinded the ISWP and EBEP, the requirements of
section 303(c)(2)(B) have not been fully implemented in California.
The scope of today's rule is to re-establish criteria for the
remaining priority toxic pollutants to meet the requirements of section
303(c)(2)(B) of the CWA. Pursuant to section 303(c)(4), the
Administrator has determined that it is necessary to include in today's
proposed action criteria for priority toxic pollutants, which are not
covered by the NTR, as amended, or by the State through site-specific
criteria, for waters of the United States in the State of California.

4. State-Adopted Site-Specific Priority Toxic Pollutant Criteria

The State has the discretion to develop site-specific criteria when
appropriate e.g., when statewide criteria appear over- or under-
protective of designated uses. Periodically, the State through its
RWQCBs will adopt site-specific criteria for priority toxic pollutants
within respective Basin Plans. These criteria are intended to be
effective throughout the Basin or throughout a designated water body.
Under California law, these criteria must be publicly reviewed and
approved by the RWQCB, the SWRCB, and the State's Office of
Administrative Law (OAL). Once this adoption process is complete, the
criteria become State law.
These criteria must be submitted to the EPA Regional Administrator
for review and approval under CWA section 303. These criteria are
usually submitted to EPA as part of a RWQCB Basin Plan Amendment, after
the Amendment has been adopted under the State's process and has become
State law.
State-Adopted Site-Specific Criteria Under EPA Review: Basin Plan
Updates: The State of California has recently reviewed and updated all
of its RWQCB Basin Plans. All of these Basin Plans have completed the
State review and adoption process and have been submitted to EPA for
review and approval. Some of the Basin Plans contain site-specific
criteria. In these cases, the State-adopted site-specific criteria are
used for water quality programs.
EPA Region 9 intends to make a determination on all State-adopted,
site-specific criteria that are currently under EPA review. If, after
this proposal, but before promulgation of this final rule, EPA approves
any State-adopted site-specific criteria, the EPA Administrator may
make a finding in the final rule that it will be unnecessary to
promulgate criteria for those site-specific pollutants and associated
water bodies. If EPA disapproves any State-adopted site-specific
criteria, today's proposed statewide criteria would apply for those
pollutants and associated water bodies.
However, if EPA promulgates statewide federal criteria as proposed
in this rule, prior to a decision on any State-adopted site-specific
criteria, the more stringent of the two criteria would be used for
water quality programs. Both federal and State water quality programs
must be satisfied, and application of the more stringent of the two
criteria would satisfy both.
Santa Ana River: EPA is currently reviewing State-adopted site-
specific criteria for copper, cadmium and lead for portions of the
Santa Ana River. These criteria are contained in the Santa Ana Region
Basin Plan Amendments (RWQCB for the Santa Ana Region). EPA intends to
complete its review and make a final determination on these site-
specific criteria prior to the promulgation of this rule.
If EPA approves the State-adopted site-specific criteria, the EPA
Administrator can make a finding in the final rule that it will be
unnecessary to promulgate federal criteria for those site-specific
pollutants and associated water bodies. If EPA disapproves the State-
adopted site-specific criteria, today's proposed statewide criteria,
when promulgated final, would apply for those pollutants and water
bodies.
State-Adopted Site-Specific Criteria with EPA Approval: In several
cases, the EPA Regional Administrator has reviewed and approved of
State-adopted site-specific criteria within the State of California.
Three of these cases are discussed below separately.
Unfortunately, EPA does not have a complete listing of all of the
site-specific criteria that may remain in place as State law after the
State court decision vacated the ISWP and the EBEP. Consequently, EPA
is proposing these criteria for all waters, except for those discussed
below in the preamble and cited in the regulatory text. If the State or
another member of the public, as confirmed by the State, indicates in
comments that there is a site-specific, State criterion that was
approved by EPA and continues to be an appropriate value, EPA would
amend the regulatory text of the final rule such that the otherwise
applicable criteria would not apply in that instance.
Sacramento River: EPA has approved site-specific criteria for
copper, cadmium and zinc in the Sacramento River, upstream of Hamilton
City, in the

[[Page 42166]]

Central Valley Region (RWQCB for the Central Valley Region) of the
State of California. EPA approved these site-specific criteria by
letter dated August 7, 1985. Specifically, EPA approved for the
Sacramento River (and tributaries) above Hamilton City, a copper
criterion of 5.6 g/l (maximum), a zinc criterion of 16
g/l (maximum) and a cadmium criterion of 0.22 g/l
(maximum), all in the dissolved form using a hardness of 40 mg/l as
CaCO3. (These criteria were actually adopted by the State
and approved by EPA as equations which vary with hardness.) These
``maximum'' criteria correspond to acute criteria in today's proposed
rule. Therefore, federal acute criteria for copper, cadmium, and zinc
for the Sacramento River (and tributaries) above Hamilton City are not
necessary to protect the designated uses and are not included in the
proposed rule. However, the EPA Administrator is making a finding that
it is necessary to include chronic criteria for copper, cadmium and
zinc for the Sacramento River (and tributaries) above Hamilton City, as
part of the proposed statewide criteria in today's proposed rule.
San Joaquin River: Site-specific selenium criteria in portions of
the San Joaquin River, in the Central Valley Region, are not included
in this proposed rule because they either have been previously approved
by EPA or promulgated by EPA as part of the NTR. EPA approved and
disapproved State-adopted site-specific selenium criteria in portions
of the San Joaquin River, in the Central Valley Region of the State of
California (RWQCB for the Central Valley Region). EPA's determination
on these site-specific criteria is contained in a letter dated April
13, 1990.
Specifically, EPA approved for the San Joaquin River, mouth of
Merced River to Vernalis, an aquatic life selenium criterion of 12
g/l (maximum with the understanding that the instantaneous
maximum concentration may not exceed the objective more than once every
three years). Today's proposed rule does not affect this federally-
approved, State-adopted site-specific acute criterion, and it remains
in effect for the San Joaquin River, mouth of Merced River to Vernalis.
Therefore, an acute criterion for selenium in the San Joaquin River,
mouth of Merced River to Vernalis is not necessary to protect the
designated use and thus is not included in the proposed rule.
By letter dated April 13, 1990, EPA also approved for the San
Joaquin River, mouth of Merced River to Vernalis, a State-adopted site-
specific aquatic life selenium criterion of 5 g/l (monthly
mean); however, EPA disapproved a State-adopted site-specific selenium
criterion of 8 g/l (monthly mean--critical year only) for
these waters. Subsequently, EPA promulgated a chronic selenium
criterion of 5 g/l (4 day average) for waters of the San
Joaquin River from the mouth of the Merced River to Vernalis in the
NTR. This chronic criterion applies to all water quality programs
concerning the San Joaquin River, mouth of Merced River to Vernalis.
Today's proposed rule does not affect the federally-promulgated chronic
selenium criterion of 5 g/l (4 day average) set forth in the
NTR. This previously federally-promulgated criterion remains in effect
for the San Joaquin River, mouth of Merced River to Vernalis.
Grassland Water District, San Luis National Wildlife Refuge, and
Los Banos State Wildlife Refuge: EPA approved for the Grassland Water
District, San Luis National Wildlife Refuge, and Los Banos State
Wildlife Refuge, a State-adopted site-specific aquatic life selenium
criterion of 2 g/l (monthly mean) by letter dated April 13,
1990. This federally-approved, State-adopted site-specific chronic
criterion remains in effect for the Grassland Water District, San Luis
National Wildlife Refuge and Los Banos State Wildlife Refuge. Therefore
it is not necessary to include in today's proposed rule, a chronic
criterion for selenium for the Grassland Water District, San Luis
National Wildlife Refuge and Los Banos State Wildlife Refuge.

D. Rationale and Approach for Developing the Proposed Rule

This section explains EPA's legal basis for today's proposed rule,
and discusses EPA's general approach for developing the specific
requirements for the State of California.
In addition to Congressional directive, there are a number of
environmental and programmatic reasons why establishing water quality
standards for toxic pollutants in California is important. Control of
toxic pollutants in surface waters is critical to the success of a
number of CWA programs and objectives, including permitting, fish
tissue quality protection, coastal water quality improvement, sediment
contamination control, certain nonpoint source controls, pollution
prevention planning, and ecological protection.

1. Legal Basis

CWA section 303(c) specifies that adoption of water quality
standards is primarily the responsibility of the states. However, CWA
section 303(c) also describes a role for the federal government to
oversee state actions to ensure compliance with CWA requirements. If
EPA's review of the states' standards finds flaws or omissions, then
the CWA authorizes EPA to correct the deficiencies (see CWA section
303(c)(4)). This water quality standards promulgation authority has
been used by EPA to issue final rules on several separate occasions,
including the NTR, as amended, which promulgated criteria similar to
those included here for a number of states. These actions have
addressed both insufficiently protective state criteria and/or
designated uses and failure to adopt needed criteria. Thus, today's
action is not unique.
The CWA in section 303(c)(4) provides two bases for promulgation of
federal water quality standards. The first basis, in paragraph (A),
applies when a state submits new or revised standards that EPA
determines are not consistent with the applicable requirements of the
CWA. If, after EPA's disapproval, the state does not amend its rules so
as to be consistent with the CWA, EPA is to promptly propose
appropriate federal water quality standards for that state. The second
basis for an EPA action is in paragraph (B), which provides that EPA
shall promptly initiate promulgation ``* * * in any case where the
Administrator determines that a revised or new standard is necessary to
meet the requirements of this Act.'' EPA is using section 303(c)(4)(B)
as the legal basis for this proposed rule.
As stated in the preamble to the NTR, the Administrator's
determination under CWA section 303(c)(4) that criteria are necessary
to meet the requirements of the Act could be supported in several ways.
EPA does not believe that it is necessary to support the criteria
proposed today on a pollutant-specific, water body-by-water-body basis.
For EPA to undertake an effort to conduct research and studies of each
stream segment or water body across the State of California to
demonstrate that for each toxic pollutant for which EPA has issued CWA
section 304(a) criteria guidance there is a ``discharge or presence''
of that pollutant which could reasonably ``be expected to interfere
with'' the designated use would impose an enormous administrative
burden and would be contrary to the statutory directive for swift
action manifested by the 1987 addition of section 303(c)(2)(B) to the
CWA.
Consistent with EPA's approach in the NTR, EPA interprets section
303(c)(2)(B) of the CWA to allow EPA to act where the State has not
succeeded in establishing numeric water quality standards for toxic
pollutants. This

[[Page 42167]]

inaction can be the basis for the Administrator's determination under
section 303(c)(4) that new or revised criteria are necessary to ensure
designated uses are protected. Here, this determination is buttressed
by the evidence in the record for the rule of the discharge or presence
of priority toxic pollutants in the State's waters for which the State
does not have numeric water quality criteria.
EPA's interpretation of section 303(c)(2)(B) is supported by the
language of the provision, the statutory framework and purpose of
section 303, and the legislative history. In adding section
303(c)(2)(B) to the CWA, Congress understood the existing requirements
in section 303(c)(1) for triennial water quality standards review and
submissions and in section 303(c)(4)(B) for promulgation. CWA section
303(c) includes numerous deadlines and section 303(c)(4) directs the
Administrator to act ``promptly'' where the Administrator determines
that a revised or new standard is necessary to meet the requirements of
the Act. Congress, by linking section 303(c)(2)(B) to the section
303(c)(1) three-year review period, gave States a last chance to
correct this deficiency on their own. The legislative history of the
provision demonstrates that chief Senate sponsors, including Senators
Stafford, Chaffee and others wanted the provision to eliminate State
and EPA delays and force quick action. Thus, to interpret CWA section
303(c)(2)(B) and (c)(4) to require such a cumbersome pollutant specific
effort on each stream segment would essentially render section
303(c)(2)(B) meaningless. The provision and its legislative background
indicate that the Administrator's determination to invoke her section
303(c)(4)(B) authority can be met by a generic finding of inaction by
the State without the need to develop pollutant specific data for
individual stream segments.
This determination is supported by information in the rulemaking
record showing the discharge or presence of priority toxic pollutants
throughout the State. While this data is not necessarily complete, it
constitutes a strong record supporting the need for numeric criteria
for priority toxic pollutants with section 304(a) criteria guidance
where the State does not have numeric criteria.
Today's proposed rule would not impose any undue or inappropriate
burden on the State of California or its dischargers. It merely puts in
place numeric criteria for toxic pollutants that are already utilized
in other states in implementing CWA programs. Under this rulemaking,
the State of California retains the ability to adopt alternative water
quality criteria simply by completing its criteria adoption process.
Upon EPA approval of those criteria, EPA will initiate action to stay
the federally-promulgated criteria.

2. Approach for Developing the Proposed Rule

In summary, EPA developed the criteria proposed in today's rule as
follows. Where EPA promulgated criteria for California in the NTR, as
amended, EPA has not acted to amend the criteria in the NTR, as
amended. Where criteria for California were not included in the NTR, as
amended, EPA used section 304(a) national criteria guidance documents
as a basis for the criteria proposed in this rule. EPA then determined
whether new information since the development of the national criteria
guidance documents warranted any changes. New information came from two
sources. For human health criteria, new or revised risk reference doses
and cancer potency factors on EPA's Integrated Risk Information System
(IRIS) as of October 1996 form the basis for criteria values different
from the national criteria guidance documents. For aquatic life
criteria, updated data sets resulting in revised criteria maximum
concentrations (CMCs) and criteria continuous concentrations (CCCs)
formed the basis for differences from the national criteria guidance
documents. Both of these types of changes are discussed in more detail
in the following section. This revised information was used to develop
the water quality criteria proposed here for the State of California.

E. Derivation of Criteria

1. Section 304(a) Criteria Guidance Process

Under CWA section 304(a), EPA has developed methodologies and
specific criteria guidance to protect aquatic life and human health.
These methodologies are intended to provide protection for all surface
waters on a national basis. The methodologies have been subject to
public review, as have the individual criteria guidance documents.
Additionally, the methodologies have been reviewed and approved by
EPA's Science Advisory Board (SAB) of external experts.
EPA has included in the record of this rule the aquatic life
methodology as described in ``Appendix B--Guidelines for Deriving Water
Quality Criteria for the Protection of Aquatic Life and Its Uses'' to
the ``Water Quality Criteria Documents; Availability'' (45 FR 79341,
November 28, 1980) as amended by the ``Summary of Revisions to
Guidelines for Deriving Numerical National Water Quality Criteria for
the Protection of Aquatic Organisms and Their Uses'' (50 FR 30792, July
29, 1985). (Note: Throughout the remainder of this preamble, this
reference is described as the 1985 Guidelines. Any page number
references are to the actual guidance document, not the notice of
availability in the Federal Register. A copy of the 1985 Guidelines is
available through the National Technical Information Service (PB85-
227049), is in the administrative record for this rule, and is
abstracted in Appendix A of Quality Criteria for Water, 1986.) EPA has
also included in the administrative record of this rule the human
health methodology as described in ``Appendix C--Guidelines and
Methodology Used in the Preparation of Health Effects Assessment
Chapters of the Consent Decree Water Criteria Documents'' (45 FR 79347,
November 28, 1980). (Note: Throughout the remainder of this preamble,
this reference is described as the Human Health Guidelines or the 1980
Guidelines.) EPA also recommends that the following be reviewed:
``Appendix D--Response to Comments on Guidelines for Deriving Water
Quality Criteria for the Protection of Aquatic Life and Its Uses,'' (45
FR 79357, November 28, 1980); ``Appendix E--Responses to Public
Comments on the Human Health Effects Methodology for Deriving Ambient
Water Quality Criteria'' (45 FR 79368, November 28, 1980); and
``Appendix B--Response to Comments on Guidelines for Deriving Numerical
National Water Quality Criteria for the Protection of Aquatic Organisms
and Their Uses'' (50 FR 30793, July 29, 1985). EPA placed into the
administrative record for this rulemaking the most current individual
criteria guidance for the priority toxic pollutants included in today's
rule. (Note: All references to appendices are to the associated Federal
Register publication.)

2. Aquatic Life Criteria

Aquatic life criteria may be expressed in numeric or narrative
form. EPA's 1985 Guidelines describe an objective, internally
consistent and appropriate way of deriving chemical-specific, numeric
water quality criteria for the protection of the presence of, as well
as the uses of, both fresh and marine water aquatic organisms.
An aquatic life criterion derived using EPA's CWA section 304(a)
method ``might be thought of as an estimate of the highest
concentration of a substance in water which does not present a
significant risk to the aquatic organisms

[[Page 42168]]

in the water and their uses.'' (45 FR 79341.) The term ``their uses''
refers to consumption by humans and wildlife (1985 Guidelines, page
48). EPA's guidelines are designed to derive criteria that protect
aquatic communities by protecting most of the species and their uses
most of the time, but not necessarily all of the species all of the
time (1985 Guidelines, page 1). EPA's 1985 Guidelines attempt to
provide a reasonable and adequate amount of protection with only a
small possibility of substantial overprotection or underprotection. As
discussed in detail below, there are several individual factors which
may make the criteria somewhat overprotective or underprotective. The
approach EPA is using is believed to be as well balanced as possible,
given the state of the science.
Numerical aquatic life criteria derived using EPA's 1985 Guidelines
are expressed as short-term and long-term numbers, rather than one
number, in order that the criteria more accurately reflect
toxicological and practical realities. The combination of a criteria
maximum concentration (CMC), a short-term concentration acute limit,
and a criteria continuous concentration (CCC), a four-day average
concentration chronic limit, provide protection of aquatic life and its
uses from acute and chronic toxicity to animals and plants, and from
bioconcentration by aquatic organisms, without being as restrictive as
a one-number criterion would have to be. (1985 Guidelines, pages 4, 5.)
The terms CMC and CCC are the scientifically correct names for the two
(acute and chronic) values of a criterion for a pollutant; however,
this document will also refer to acute criterion and chronic criterion
to which they are more commonly referred.
The two-number criteria are intended to identify average pollutant
concentrations which will produce water quality generally suited to
maintenance of aquatic life and their uses while restricting the
duration of excursions over the average so that total exposures will
not cause unacceptable adverse effects. Merely specifying an average
value over a time period is insufficient unless the time period is
short, because excursions higher than the average can kill or cause
substantial damage in short periods.
A minimum data set of eight specified families is required for
criteria development (details are given in the 1985 Guidelines, page
22). The eight specific families are intended to be representative of a
wide spectrum of aquatic life. For this reason it is not necessary that
the specific organisms tested be actually present in the water body.
States may develop site-specific criteria using native species,
provided that the broad spectrum represented by the eight families is
maintained. All aquatic organisms and their common uses are meant to be
considered, but not necessarily protected, if relevant data are
available.
EPA's application of guidelines to develop the criteria matrix in
the proposed rule is judged by the Agency to be applicable to all
waters of the United States, and to all ecosystems (1985 Guidelines,
page 4). There are waters and ecosystems where site-specific criteria
could be developed, as discussed below, but the State should identify
those waters and develop the appropriate site-specific criteria.
Fresh water and salt water (including both estuarine and marine
waters) have different chemical compositions, and freshwater and
saltwater species rarely inhabit the same water simultaneously. To
provide additional accuracy, criteria are developed for fresh water and
for salt water.
Limitations of the analyses which may make the criteria
underprotective include the fact that data for all species are not
available and therefore not considered; the analysis also applies to
criteria on an individual basis with no consideration of additive or
synergistic effects, and the analysis does not consider impacts on
wildlife, due principally to a lack of data. Chemical toxicity is often
related to certain receiving water characteristics (pH, hardness, etc.)
of a water body. Adoption of some criteria without consideration of
these parameters could result in the criteria being overprotective.
a. Freshwater Criteria
For this proposal, EPA updated freshwater aquatic life criteria
contained in CWA section 304(a) criteria guidance first published in
the early 1980's and later modified in the NTR, as amended, for the
following eleven pollutants: arsenic, cadmium, chromium (VI), copper,
mercury, dieldrin, endrin, lindane (gamma BHC), nickel,
pentachlorophenol, and zinc. These updates are explained in a technical
support document entitled, 1995 Updates: Water Quality Criteria
Documents for the Protection of Aquatic Life in Ambient Water, (U.S.
EPA-820-B-96-001, September 1996), available in the administrative
record to this rulemaking; this document presents the derivation of
each of the final CMCs and CCCs and the toxicity studies from which the
updated freshwater criteria for the eleven pollutants were derived. The
presentation of polychlorinated biphenyls (PCB) criteria in the
criteria matrix for this proposal differs from that in the NTR, as
amended; for this proposal, the criteria are expressed as a total of
all aroclors, while for the NTR, as amended, the criteria are expressed
for each aroclor. The mercury criteria also differ in this proposal due
to the Agency's movement away from aquatic life criteria based on the
Final Residue Value (FRV) procedure of the 1985 Guidance. Differences
between the eleven CMCs and CCCs as contained in CWA section 304(a)
criteria guidance documents and the CMCs and CCCs in this proposed rule
can be attributed to one or more of the following reasons.
First, EPA derived and published CWA section 304(a) criteria
guidance documents between 1980 and 1987. Some of the aquatic life
criteria in this proposed rule were calculated using data published
subsequent to the issuance of individual 304(a) criteria guidance
documents or using other new information. The pollutants for which this
applies are: arsenic, cadmium, chromium (VI), copper, mercury,
dieldrin, endrin, lindane, nickel, pentachlorophenol, and zinc. The use
of an updated database resulted in less restrictive acute and/or
chronic criteria for cadmium and zinc as compared to the published
criteria guidance documents. EPA believes that the differences between
the proposed updated criteria and the national published criteria
guidance documents are insignificant. However, EPA believes that it is
appropriate to propose criteria in this rule based on the most recent
data. The following table shows the differences between the proposed
criteria for this rule and the 304(a) criteria guidance which were
promulgated in the NTR, as amended. All values are in micrograms per
liter or g/l:

----------------------------------------------------------------------------------------------------------------
Proposed freshwater NTR freshwater
Compound -------------------------------------------------------
CMC CCC CMC CCC
----------------------------------------------------------------------------------------------------------------
Arsenic................................................. 1,2 340 1,2 150 1,3 360 1,3 190

[[Page 42169]]

Cadmium................................................. 1,2,4 4.3 1,2,4 2.2 1,5 3.7 1,5 1.0
Chromium (VI)........................................... 1,2 16 1,2 11 1,3 15 1,3 10
Copper.................................................. 1,2,4 13 1,2,4 9.0 1,5 17 1,5 11
Nickel.................................................. 1,2,4 470 1,2,4 52 1,5 1400 1,5 160
Zinc.................................................... 1,2,4 120 1,2,4 120 1,5 110 1,5 100
Pentachloro-phenol...................................... 2,6 19 2,6 15 6 20 6 13
Lindane (gamma-BHC)..................................... 2 0.95 ............ 7 2 0.08
Dieldrin................................................ 2 0.24 2 0.056 7 2.5 0.0019
Endrin.................................................. 2 0.086 2 0.036 7 0.18 0.0023
Mercury................................................. 1,2,3 1.4 1,2,3 0.77 1,3 2.1 0.012
PCBs.................................................... ............ 8,9 0.014 ............ 8,10 0.014
Mercury................................................. 1,3 1.8 1,3 0.94 1,3 1.8 0.025
PCBs.................................................... ............ 8,9 0.03 ............ 8,10 0.03
----------------------------------------------------------------------------------------------------------------
\1\ These freshwater and saltwater criteria for metals are expressed in terms of the dissolved fraction of the
metal in the water column, not the total recoverable fraction. Criterion values were calculated by using EPA's
CWA 304(a) criteria guidance values (described in the total recoverable fraction) and then applying conversion
factors as in the NTR, as amended, (60 FR 22228, May 4, 1995 and 40 CFR part 131).
\2\ This criterion has been recalculated pursuant to 1995 Updates: Water Quality Criteria Documents for the
Protection of Aquatic Life in Ambient Water (EPA-820-B-96-001, September 1996). See also the Great Lakes Water
Quality Initiative (40 CFR Parts 9, 122, 123, 131, and 132; Final Water Quality Guidance for the Great Lakes
System, Final Rule; 60 FR 15366, March 23, 1995) and Great Lakes Water Quality Initiative Criteria Documents
for the Protection of Aquatic Life in Ambient Water (EPA-820-B-95-004, March 1995).
\3\ Criteria for these metals are expressed as a function of the water-effect ratio (WER) as defined in 40 CFR
131.36(c).
\4\ These freshwater aquatic life criteria for metals are expressed as a function of total hardness (mg/l as
CaCO3 ) in the water body. The equations are provided in the proposed rule at 40 CFR 131.38(b)(2). Values
displayed above and in the proposed rule matrix correspond to a total hardness of 100 mg/l as CaCO3.
\5\ Freshwater aquatic life criteria for these metals are expressed as a function of total hardness (mg/l as
CaCO3), and as a function of the pollutant's water-effect ratio, WER, as defined in 40 CFR 131.36(c). The
equations are provided in the NTR, as amended, and values above and in the rule matrix correspond to a total
hardness of 100 mg/l as CaCO3 and a water-effect ratio of 1.0.
\6\ These freshwater aquatic life criteria for pentachlorophenol are expressed as a function of pH, and are
calculated as follows: (Values displayed above in the matrix correspond to a pH of 7.8.) CMC=exp(1.005 (pH)-
4.830). CCC=exp(1.005(pH)-5.290).
\7\ These aquatic life criteria for these pollutants were issued in 1980 utilizing the 1980 Guidelines for
criteria development. The acute values shown are final acute values (FAV) which by the 1980 Guidelines are
instantaneous values.
\8\ The CAS numbers for the PCB compounds are 53469219, 11097691, 11104282, 11141165, 12672296, 11096825, and
12674112, respectively.
\9\ This proposed criterion is the sum of all aroclors.
\10\ This criterion was listed for each aroclor in the matrix at 40 CFR 131.36(b)(1).

Secondly, some of the 304(a) criteria guidance documents were
derived using a methodology which preceded EPA's current methodology,
the 1985 Guidelines (pages 16 and 17).
In this proposed rule, where sufficient data existed to use the
1985 Guidelines, EPA recalculated the criteria. The chemicals for which
this applies are: dieldrin, endrin, and lindane (gamma BHC) (chronic
criterion only). The NTR, as amended, however, did not update the 1980
criteria using the 1985 Guidelines.
Third, EPA has deleted some of the data used in deriving three
criteria: specifically, the 1984 criterion for copper and the 1980
criteria for dieldrin and endrin, because under EPA's 1985 Guidelines,
the toxicity testing procedure was unacceptable.
Fourth, in several of the 304(a) criteria guidance documents, the
range of Species Mean Acute Values (SMAVs) or Species Mean Chronic
Values (SMCVs) was greater than a factor of five for some genera.
Because of this wide range, EPA set the Genus Mean Acute Values (GMAVs)
or Genus Mean Chronic Values (GMCVs) for those genera equal to the
lowest SMAV or SMCV for that genus in order to provide adequate
protection to all tested species in the genus. The pollutants for which
this applies are cadmium, copper and dieldrin.
In addition to the reasons cited earlier concerning differences
between NTR, as amended, criteria and proposed CMCs for this
rulemaking, several of the proposed CCCs are affected by a preference
of using freshwater Acute-Chronic Ratios (ACRs). In some of the 304(a)
criteria guidance documents, EPA had used saltwater ACRs in the
calculation of freshwater Final Chronic Values (FCVs) when available.
In updating criteria, EPA generally did not use saltwater ACRs when
there were a sufficient number of acceptable freshwater ACRs to
calculate a Final Acute-Chronic Ratio (FACR) because freshwater data is
preferable for freshwater criteria. When there was an insufficient
number of freshwater ACRs to calculate a FACR, EPA used saltwater ACRs
with any acceptable freshwater ACRs. The pollutants for which this
applies are: dieldrin, endrin and nickel. Removal of saltwater ACRs
from the data sets had a minor effect on the resultant criteria.
Today's rule utilizes the Final Residue Value (FRV) procedure of
the 1985 Guidelines for PCBs. The 1985 national methodology in the 1985
Guidelines indicates that the FRV is intended to prevent concentrations
of pollutants in commercial or recreational aquatic species from
affecting the marketability of those species or affecting wildlife that
consume aquatic life. While in today's rule the FRV is used to
calculate the chronic values for PCBs, EPA believes it may not be as
protective as criteria derived from the Final Chronic Value (FCV).
However, the use of the FRV in deriving the chronic values for PCBs
represents EPA's best available scientific approach. The NTR, as
amended, criteria for dieldrin, endrin, and mercury were based on FRVs
calculated from FDA action levels. EPA now believes that the human
health criteria proposed elsewhere in this notice will provide an
appropriate level of protection to humans consuming freshwater fish and
shellfish, but that use of the FDA action levels to protect aquatic
life (fish and propagation of fish) is inappropriate. In this rule, EPA
updated the chronic values for dieldrin, endrin and mercury based on
Final Chronic Values (FCVs) calculated by dividing a Final Acute Value
(FAV) by the Final Acute-Chronic Ratio (FACR).
The derivation of each of these criteria, and the toxicity studies
upon

[[Page 42170]]

which they are based, are discussed in a technical support document
entitled, 1995 Updates: Water Quality Criteria Documents for the
Protection of Aquatic Life in Ambient Water (EPA-820-B-96-001,
September 1996). This document is available in the administrative
record for this rulemaking.
b. Freshwater Acute Selenium Criterion
EPA is proposing a different freshwater acute aquatic life
criterion for selenium in this proposed rule than was promulgated in
the NTR, as amended. EPA's proposal here is consistent with EPA's
recent (proposed) selenium criterion maximum concentration for the
Water Quality Guidance for the Great Lakes System (61 FR 58444,
November 14, 1996). This proposal takes into account data showing that
selenium's two most prevalent oxidation states, selenite and selenate,
present differing potentials for aquatic toxicity, as well as new data
indicating that various forms of selenium are additive. Additivity
increases the toxicity of mixtures of different forms of the pollutant.
The new approach produces a different selenium acute criterion
concentration, or CMC, depending upon the relative proportions of
selenite, selenate, and other forms of selenium that are present. While
these revisions may produce either a less or a more stringent acute
criterion for selenium, depending on which form of the pollutant is
predominant in a water body, the proposed freshwater acute criterion
will protect aquatic life in fresh waters of the State of California.
Derivation of the Current Freshwater Criterion for Selenium: When
EPA published a recommended freshwater aquatic life criterion for
selenium in 1987, it considered both field data on chronic toxicity
from Belews Lake in North Carolina and laboratory data showing chronic
effects. A comparison of the data indicated that selenium was more
toxic to aquatic life in the field than in standard laboratory toxicity
tests. Consequently, to ensure that the criterion would protect aquatic
life, EPA derived a chronic criterion, or a CCC, of 5 g/l for
total recoverable selenium from the field data. Because the Belews Lake
study did not distinguish between selenite, selenate, and any other
form of selenium, and because some forms of selenium can convert to
other forms over time (U.S. EPA, 1987), EPA established a single CCC
for selenium rather than a separate CCC for selenite and/or selenate.
EPA reasoned that acute effects would also be more severe in the
field than in the laboratory. EPA, however, was not able to find any
field studies assessing acute effects. Consequently, EPA back-
calculated the CMC from the field-derived CCC for total selenium,
arriving at a value of 19.98 g/l, which it rounded to 20
g/l. When EPA proposed and promulgated selenium criteria for
the NTR, as amended, it used the same field-data approach and
calculated a CMC of 20 g/l and a CCC of 5 g/l for all
forms of selenium.
EPA noted that, had it concluded that laboratory data could serve
as a basis for the selenium criteria, there were sufficient laboratory
studies on acute effects to establish separate CMCs for both selenate
and selenite. EPA calculated that a CMC for selenite (selenium IV)
based on laboratory data might have been 185.9 g/l, while a
CMC for selenate (selenium VI) might have been 12.82 g/l. As
explained above, however, EPA chose to base the CMC on field data that
did not differentiate between selenite and selenate.
EPA is proposing a different approach to that used in the NTR,
amended, for the fresh waters of California covered by this proposed
rule. EPA is proposing a new CMC for total selenium based on more
recent studies which indicate that the toxicities of various forms of
selenium are additive. EPA is proposing an equation that will allow
calculation of a CMC for selenium based on the relative proportions of
selenite, selenate and other selenium forms present in a specific water
body. The toxicities for selenite and selenate used in this equation
are based on the laboratory studies cited in the 1987 and 1995 selenium
criteria documents, and are identical to the values calculated in those
documents.
EPA continues to believe that the field data support a CCC of 5
g/l for selenium. The chronic criterion addresses longer-term
exposures to selenium under field conditions, including exposure
through the food chain. EPA has no field data that can support
different chronic criteria for different forms of selenium.
Furthermore, EPA believes that current studies show that the various
forms of selenium ``interconvert'' to other forms over these longer
time frames, so that the relative proportions of the different forms
change during the exposure period. A form that exhibits low toxicity at
one point during the exposure period may convert to a different, more
toxic form at a different point.
Selenium Chemistry: Selenium takes several forms in ambient waters
which can significantly alter its toxicity to aquatic life, as shown
below. Inorganic selenium has two oxidation states (i.e., selenium IV,
or selenite, and selenium VI, or selenate), which can exist
simultaneously in aerobic surface water at pH 6.5 to 9.0. Chemical
conversion from one oxidation state to another often proceeds at such a
slow rate in aerobic surface water that thermodynamic considerations do
not determine the relative concentrations of the oxidation states.
Although selenate (selenium VI) is thermodynamically favored in
oxygenated alkaline water, substantial concentrations of both
organoselenium (selenium minus II) and selenite (selenium IV) are not
uncommon (Burton et al. 1980; Cutter and Bruland 1984; Measures and
Burton 1978; North Carolina Department of Natural Resources and
Community Development 1986; Robberecht and Van Gricken 1982; Takayanagi
and Cossa 1985; Takayanagi and Wong 1984a,b: Uchida et al. 1980).
Various forms of organic selenium also occur in water (Besser et
al. 1994; Cutter 1991). Toxicity data for some organic selenium forms
are available and are compared below to toxicity data for selenite and
selenate:

[[Page 42171]]

------------------------------------------------------------------------
Daphnia
Compound Zebrafish C. riparius b, c, magnae
a (mg/l) d (mg/l) e (mg/
--------------------------------------------------------------------l)--
Selenate........................ 18. 16.2 10.5 2.84
Seleno-DL-cystine............... 12 ................. 2.01
Selenite........................ 1. 7.95 14.6 0.55
Seleno-DL-methionine............ 0.1 ................. 0.31
Seleno-L-methionine............. .......... 5.78 6.88 .......
------------------------------------------------------------------------
a 10-day LC50 (Niimi and LaHam 1976). d 48-hr LC50 (Maier et
al. 1993).
b 48-hr LC50 (Ingersoll et al. 1990). e 48-hr LC50
(Maier et al. 1993).
c River Water.

Cutter (1991) described methods for measuring total recoverable and
dissolved selenate, selenite, organoselenium, and selenium in water,
and other information concerning the measurement of selenium in water
has been published by Besser et al. (1994), McKeown and Marinas (1986),
Pitts et al. (1994), and Takayanagi and Cosa (1985).
EPA believes that recent studies demonstrate the acute toxicities
of selenate, selenite, and one form of organoselenium are additive;
that is, these forms are more toxic together then they are separately
(Hamilton and Buhl 1990; Maier et al. 1993). The studies demonstrated
additivity by comparing the toxicities of mixtures to the toxicities of
the separate toxicants. Thus, EPA believes that it would be appropriate
to establish separate CMCs for selenate and selenite only in situations
in which either selenate or selenite is the only form of selenium in
the water column. When more than one form occurs in the water,
additivity should be taken into account so that the CMC for selenium is
a function of the toxicities and concentrations of the forms. EPA is
proposing an equation that can be used to derive an appropriate
criterion for total selenium based on the relative concentrations of
selenite, selenate, and all other forms of selenium found in a
particular water body.
Toxicity of Three Categories of Selenium: Selenium (IV). EPA is
proposing to rely on the laboratory data contained in the 1987 and 1995
criteria documents to establish an acute toxicity of 185.9 g/l
for selenite.
Selenium (VI). EPA is proposing to rely on the laboratory data
contained in the 1987 and 1995 criteria documents to establish an acute
toxicity of 12.83 g/l for selenate.
Other Forms of Selenium. EPA has not found and believes that
sufficient toxicity data do not exist to allow derivation of CMCs for
other selenium compounds. Nevertheless, as indicated in the previous
table, the acute toxicity of such other forms of selenium appears to be
significant with toxicity increasing by as much as 180 times depending
on the form of selenium and the test organism. Toxicity tests conducted
on the other forms of selenium indicate that they can be more toxic
than selenate and selenite. Consequently, in order not to ignore the
toxicity of these other forms of selenium, EPA is proposing to assume
that half of the measured or derived concentration of ``other''
selenium forms is as toxic as selenate and half is as toxic as
selenite. EPA believes this default assumption is more reasonable than
assuming either that the entire quantity of ``other'' forms is as toxic
as either selenate or selenite, or that it is not toxic. Such
assumptions would be more likely to over-predict or under-predict the
toxicity of this ``other forms'' category. EPA is also reluctant to
compute any type of ``average'' from the toxicity data on ``other
forms'' presented in the table above. These data are quite sparse.
Moreover, they reflect only organic selenium forms, and the toxicities
of other inorganic forms and compounds may be quite different.
Equation: Additive toxicity means that the concentrations of the
different forms should be added together after adjusting for the
relative toxicity of each. For a single toxicant the goal is for the
concentration, c, to be less than or equal to the criterion, CMC; that
is, the ratio c/CMC 1. For additive toxicants the goal is
for the sum of such ratios to be less than or equal to 1. Thus, for two
forms of selenium with additive acute toxicities, the concentration of
each form should be controlled such that:
[GRAPHIC] [TIFF OMITTED] TP05AU97.000

where c1 is the concentration of selenite and other
selenium assumed to have the toxicity of selenite, c2 is the
concentration and selenate and other selenium assumed to have the
toxicity of selenate; and CMC1 and CMC2 are the
CMCs for selenite and selenate respectively. A Criterion Maximum
Concentration, CMCSe, for the combined additive forms of
selenium can then be calculated from the following equation, which is
derived from the previous one:
[GRAPHIC] [TIFF OMITTED] TP05AU97.001

where f1 and f2 are the fractions of total
selenium that are treated as selenite and selenate respectively (that
is, f1=c1/cSe and
cSe=c1+c2), and
f1+f2=1.

The above equations, when coupled with the assumption that half of
the other selenium (including organoselenium) has the toxicity of
selenite and half has the toxicity of selenate, behave as follows. If
the concentrations of selenite and other selenium are zero
(c1=0) then the Criterion Maximum Concentration
(CMCSe) would be calculated to be 12.82 g/l, the
CMC of selenate. On the other hand, if the concentrations of selenate
and other selenium are zero, then CMCSe would be calculated
to be 185.9 g/l, the CMC of selenite. In determining
compliance with this criterion, EPA expects that monitoring to
determine speciation will be necessary.
EPA is requesting comment on the data and approach for deriving the
proposed CMC for selenium applicable to California in this rulemaking.
Specifically, EPA is requesting comment on the scientific basis for
establishing the additivity of the toxicities of the various forms of
selenium (selenate, selenite, and other selenium compounds). EPA also
requests comments on the procedure used to account for the additivity
of the various forms of selenium in the criterion derivation algorithm.
If persons have filed comments on the November 1996 notice, cited
above, that they wish to submit for this rulemaking, they should submit
them as described above.
c. Dissolved Metals Criteria
In December of 1992, in the NTR, EPA promulgated water quality
criteria for several states that had failed to meet the requirements of
CWA section 303(c)(2)(B). Included among the water quality criteria
promulgated were numeric criteria for the protection of aquatic life
for 11 metals: arsenic,

[[Page 42172]]

cadmium, chromium (III), chromium (VI), copper, lead, mercury, nickel,
selenium, silver and zinc. Criteria for two metals applied to the State
of California: chromium III and selenium.
The Agency received extensive public comment during the development
of the NTR regarding the most appropriate approach for expressing the
metals criteria. The principal issue was the correlation between metals
that are measured and metals that are bioavailable and toxic to aquatic
life.
At the time of the NTR promulgation, Agency policy was to express
metals criteria, as recommended in the section 304(a) criteria guidance
documents, as total recoverable metal measurements. Agency guidance
prior to the NTR promulgation indicated that metals criteria may be
expressed either as total recoverable metal or dissolved metal. See
Interim Guidance on Interpretation and Implementation of Aquatic Life
Criteria for Metals, U.S. EPA, May 1992 (notice of availability
published at 57 FR 4041, June 5, 1992). Since the NTR covered a
substantial number of water bodies of varying water quality, EPA
selected what it considered a simple, conservative approach to
implement the metals criteria, namely, the total recoverable method.
EPA continued to work with the states and other interested parties
on the issue of metals bioavailability and toxicity. EPA held a
workshop of invited experts on the issue and as a result of the
consultations, the Agency issued a policy memorandum on October 1,
1993, entitled, Office of Water Policy and Technical Guidance on
Interpretation and Implementation of Aquatic Life Metals Criteria (the
Metals Policy). The Metals Policy states:

It is now 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 the metal in the
water column than does total recoverable metal.

It further states:

Until the scientific uncertainties are better resolved, a range
of different risk management decisions can be justified. EPA
recommends that State water quality standards be based on dissolved
metal. 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.

The adoption of the Metals Policy did not change EPA's position
that the existing total recoverable criteria published under section
304(a) of the CWA were scientifically defensible. EPA believed, and
continues to believe, that when a state develops and adopts its
standards, the state, in making its risk management decision, may want
to consider sediment, food chain effects, and other fate-related issues
and decide to adopt total recoverable or dissolved metals criteria.
In 1993, a number of parties brought lawsuits challenging the NTR
metals criteria. See American Forest and Paper Ass'n, Inc. et al. v.
U.S. EPA (Consolidated Case No. 93-0694 (RMU), D.D.C.). The plaintiffs
in those lawsuits wanted the permitting authorities in the NTR states
to use criteria based on dissolved metal rather than total recoverable
metal. After careful consideration, EPA concluded that it was in the
public interest to revise the metals criteria promulgated in the NTR to
reflect the Office of Water's new metals policy. On February 15, 1995,
EPA and the plaintiffs filed a partial settlement agreement with the
Court. Pursuant to the terms of the agreement, EPA agreed to issue an
administrative stay of the numeric aquatic life water quality criteria
(expressed as total recoverable metal) for: arsenic; cadmium, chromium
(III); chromium (VI); copper; lead, mercury (acute only), nickel,
selenium (saltwater only), silver, and zinc. The stay was effective
April 14, 1995 (60 FR 22228, May 4, 1995), and was only intended to be
in effect until EPA took action to amend the NTR by promulgating new
metals criteria based on dissolved metal. EPA published an interim
final amendment to the NTR effective April 15, 1995; this amendment
promulgated new metals criteria for the metals listed in the stay (60
FR 22229, May 4, 1995).
The numeric criteria in the NTR, as amended, reflect the Office of
Water's current policy with respect to metals. The 1995 NTR amendment
promulgated dissolved metals criteria as substitutes for the total
recoverable metals criteria subject to the EPA's administrative stay.
The NTR promulgated freshwater chromium (III) criteria and freshwater
selenium criteria for the State of California. However, since the
amendments did not change the freshwater selenium criteria, only
California's chromium (III) criteria were changed to the dissolved form
through the NTR, as amended.
Since EPA's previous criteria guidance had been expressed as total
recoverable metal, to express the criteria as dissolved, conversion
factors were developed to account for the possible presence of
particulate metal in the laboratory toxicity tests used to develop the
total recoverable criteria. Initially, EPA included a set of
recommended freshwater conversion factors with the Metals Policy. Based
on additional laboratory evaluations that simulated the original
toxicity tests, EPA refined the procedures used to develop freshwater
conversion factors for aquatic life criteria. These new conversion
factors were made available for public review and comment in the
amendments to the NTR on May 4, 1995, at 60 FR 22229.
EPA also conducted saltwater laboratory simulation tests for the
development of conversion factors for saltwater metals criteria. The
saltwater tests results were first available in the amendments to the
NTR on May 4, 1995. The conversion factors in this proposed rule and
other technical reports are the same as those referenced in the May 4,
1995 amendments to the NTR and supersede the conversion factors in
Attachment 2 of the Metals Policy.
Freshwater Criteria Conversion Factors: The freshwater conversion
factors contained in today's proposed rule are contained in the
Derivation of Conversion Factors for the Calculation of Dissolved
Freshwater Aquatic Life Criteria for Metals, U.S. EPA, 1995, available
in the administrative record for this rulemaking. This study did not
include laboratory simulation tests for mercury or silver; therefore,
the freshwater conversion factors for mercury and silver used today are
from the Metals Policy, also in the record for this rule. These
conversion factors are presented in 40 CFR 131.38(b)(2) of today's
proposed rule.
The conversion factors for most freshwater metals were established
as constant values. For cadmium and lead however, EPA found that water
hardness mediated the conversion factor and should be taken into
account when converting total recoverable cadmium and lead criteria to
dissolved. 40 CFR 131.38(b)(2) of today's proposed rule presents the
hardness-dependent conversion factors for cadmium and lead.
Saltwater Criteria Conversion Factors: Acute saltwater conversion
factors were first promulgated in the amendments to the NTR, and are
again being proposed in this rule. The data and the acute criteria
conversion factors for salt water are contained in the Derivation of
Conversion Factors for the Calculation of Dissolved Saltwater Aquatic
Life Criteria for Metals, U.S. EPA, 1995. This summary report and its
supporting data are available in the administrative record. Saltwater
chronic conversion factors have not been developed separately and
therefore are not available in today's proposed rule. Based on close
similarities between the

[[Page 42173]]

freshwater acute and chronic conversion factors, EPA believes that, if
calculated, the chronic saltwater conversion factors would be nearly
the same as the acute saltwater factors. In the absence of these
chronic conversion factors, the saltwater acute conversion factors
would apply. Salt water simulation tests were not completed for mercury
or silver, therefore, the conversion factors from the Metals Policy
continue to apply. The saltwater conversion factors are presented in 40
CFR 131.38(b)(2) of today's proposed rule.
Calculation of Dissolved Metals Criteria: Metals criteria values in
today's proposed rule in the matrix at 131.38(b)(1) are shown as
dissolved metal. These criteria have been calculated in one of two
ways. For freshwater metals criteria that are hardness-dependent, the
dissolved metal criteria value is calculated separately for each
hardness using the table at proposed 40 CFR 131.38(b)(2). The hardness-
dependent freshwater values presented in the matrix at proposed 40 CFR
131.38(b)(1) have been calculated using a hardness of 100 mg/l as
CaCO3 for illustrative purposes only. Saltwater and
freshwater metals criteria that are not hardness-dependent are
calculated by taking the total recoverable criteria values (from EPA's
national section 304(a) criteria guidance documents, as updated as
described in section a. above) before rounding, and multiplying them by
the appropriate conversion factors. The final dissolved metals criteria
values, as they appear in the matrix at proposed 40 CFR 131.38(b)(1),
are rounded to two significant figures.
Translators for Dissolved to Total Recoverable Metals Limits: EPA's
National Pollutant Discharge Elimination System (NPDES) regulations
require that limits for 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 metal's limit in another form (e.g.,
dissolved, specific valence, or total) when required to carry out
provisions of the CWA. 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 metals
would not dissolve after discharge. The NPDES permit regulations do not
require that water quality standards be expressed as total recoverable;
rather, the regulations require permit writers to develop permit limits
that are expressed in terms of metals concentrations and loadings that
are measured using the total recoverable method. Expressing criteria as
dissolved metal requires translation between different metal forms in
the calculation of the permit limit so that a total recoverable permit
limit can be established that will achieve water quality standards.
Thus, it is important that permitting authorities and other authorities
have the ability to translate between dissolved metal in ambient waters
and total recoverable metal in effluent.
EPA has completed guidance on the use of translators to convert
from dissolved metals criteria to total recoverable permit limits. The
document, The Metals Translator: Guidance for Calculating a Total
Recoverable Permit Limit From a Dissolved Criterion (EPA 823-B-96-007,
June 1996), is included in the administrative record for today's
proposed rule. This technical guidance examines how to develop a metals
translator which is defined as the fraction of total recoverable metal
in the downstream water that is dissolved, i.e., the dissolved metal
concentration divided by the total recoverable metal concentration. A
translator may take one of three forms: (1) It may be assumed to be
equivalent to the criteria guidance conversion factors; (2) it may be
developed directly as the ratio of dissolved to total recoverable
metal; and (3) it may be developed through the use of a partition
coefficient that is functionally related to the number of metal binding
sites on the adsorbent in the water column (e.g., concentrations of
total suspended solids or TSS). This guidance document discusses these
three forms of translators, as well as field study designs, data
generation and analysis, and site-specific study plans to generate
site-specific translators.
California Regional Water Quality Control Boards may use any of
these methods in developing water quality-based permit limits to meet
dissolved metals criteria. EPA encourages the State to adopt a
statewide policy on the use of translators so that the most appropriate
method or methods are used consistently within California.
d. Application of Metals Criteria
In selecting an approach for implementing the metals criteria, the
principal issue is the correlation between metals that are measured and
metals that are biologically available and toxic. In order to assure
that the metals criteria are appropriate for the chemical conditions
under which they are applied, EPA is providing for the adjustment of
the criteria through application of the ``water-effect ratio''
procedure. EPA notes that performing the testing to use a site-specific
water-effect ratio is optional on the part of the State.
In the NTR, as amended, EPA identified the water-effect ratio (WER)
procedure as a method for optional site-specific criteria development
for certain metals. The WER approach compares bioavailability and
toxicity of a specific pollutant in receiving waters and in laboratory
waters. A WER is an appropriate measure of the toxicity of a material
obtained in a site water divided by the same measure of the toxicity of
the same material obtained simultaneously in a laboratory dilution
water.
On February 22, 1994, EPA issued Interim Guidance on the
Determination and Use of the Water-Effect Ratios for Metals (EPA 823-B-
94-001) now incorporated into the updated Second Edition of the Water
Quality Standards Handbook, Appendix L. In accordance with the WER
guidance and where application of the WER is deemed appropriate, EPA
strongly encourages the application of the WER on a watershed or water
body basis in California as opposed to application on a discharger-by-
discharger basis. This approach is technically sound, an efficient use
of resources, and allowable for NPDES permitting authorities.
The rule proposes that a default WER value of 1.0 will be assumed,
if no site-specific WER will be determined. To use a WER other than the
default of 1.0, the rule proposes that the WER must be determined as
set forth in EPA's WER guidance or determined by another scientifically
defensible method that has been adopted by the State as part of its
water quality standards program and approved by EPA.
The WER is a more comprehensive mechanism for addressing
bioavailability issues than simply expressing the criteria in terms of
dissolved metal. Consequently, expressing the criteria in terms of
dissolved metal, as done in today's proposed rule for California, does
not completely eliminate the utility of the WER. This is particularly
true for copper, a metal that forms reduced-toxicity complexes with
dissolved organic matter.
The Interim Guidance on Determination and Use of Water-Effect
Ratios for Metals explains the relationship between WERs for dissolved
criteria and WERs for total recoverable criteria. Dissolved
measurements are to be used in the site-specific toxicity testing
underlying the WERs for dissolved criteria. Because

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WERs for dissolved criteria generally are little affected by elevated
particulate concentrations, EPA expects those WERs to be somewhat less
than WERs for total recoverable criteria in such situations.
Nevertheless, after the site-specific ratio of dissolved to total metal
has been taken into account, EPA expects a permit limit derived using a
WER for a dissolved criterion to be similar to the permit limit that
would be derived from the WER for the corresponding total recoverable
criterion.
e. Saltwater Copper Criteria
The saltwater copper criteria for aquatic life in today's proposed
rule are 4.8 g/l (CMC) and 3.1 g/l (CCC) in the
dissolved form. New data including data collected from studies for the
New York/New Jersey Harbor and the San Francisco Bay indicated a need
to revise the copper criteria document to reflect a change in the
saltwater CMC and CCC aquatic life values. EPA conducted a
comprehensive literature search and added toxicity test data for seven
new species to the database for the saltwater copper criteria. EPA
believes these new data have national implications and the national
criteria guidance now contain a CMC of 4.8 g/l dissolved and a
CCC of 3.1 g/l dissolved. In the amendments to the NTR, EPA
noticed the availability of data to support these changes to the NTR,
and solicited comments. The data can be found in the draft document
entitled, Ambient Water Quality Criteria--Copper, Addendum 1995. This
document is available from the Office of Water Resource Center and is
available for review in the administrative record for this proposed
rule. EPA is now requesting comments on these revised criteria as
applied to the State of California. Commenters who wish to refer to
their comments on the Notice of Availability must resubmit a copy of
their previous comments.
f. Chronic Averaging Period
In establishing water quality criteria, EPA generally recommends an
``averaging period'' which reflects the duration of exposure required
to elicit effects in individual organisms (TSD, Appendix D-2.) The CCC
is intended to be the highest concentration that could be maintained
indefinitely in a water body without causing an unacceptable effect on
the aquatic community or its uses. (TSD, Appendix D-1). As aquatic
organisms do not generally experience steady exposure, but rather
fluctuating exposures to pollutants, and because aquatic organisms can
generally tolerate higher concentrations of pollutants over a shorter
periods of time, EPA expects that the concentration of a pollutant can
exceed the CCC without causing an unacceptable effect if (a) the
magnitude and duration of exceedences are appropriately limited and (b)
there are compensating periods of time during which the concentration
is below the CCC. This is done by specifying a duration of an
``averaging period'' over which the average concentration should not
exceed the CCC more often than specified by the frequency (TSD,
Appendix D-1).
EPA is proposing a 4-day averaging period for chronic criteria,
which means that measured or predicted ambient pollutant concentrations
should be averaged over a 4-day period to determine attainment of
chronic criteria. EPA acknowledges that the State may develop and adopt
an averaging period that differs from EPA's recommendation, so long as
it is scientifically supportable.
The most important consideration for setting an appropriate
averaging period is the length of time that sensitive organisms can
tolerate exposure to a pollutant at levels exceeding a criterion
without showing adverse effects on survival, growth, or reproduction.
EPA believes that the chronic averaging period must be shorter than the
duration of the chronic tests on which the CCC is based, since, in some
cases, effects are elicited before exposure of the entire duration.
Most of the toxicity tests used to establish the chronic criteria are
conducted using steady exposure to toxicants for a least 28 days. (TSD,
page 35). Some chronic tests, however, are much shorter than this (TSD,
Appendix D-2). EPA selected the 4-day averaging period based on the
shortest duration in which chronic test effects are sometimes observed
for certain species and toxicants. In addition, EPA believes that the
results of some chronic tests are due to an acute effect on a sensitive
life stage that occurs some time during the test, rather than being
caused by long-term stress or long-term accumulation of the test
material in the organisms.
Additional discussion of the rationale for the 4-day averaging
period is contained in Appendix D of the TSD. Balancing all of the
above factors and data, EPA believes that the 4-day averaging period
falls within the scientifically reasonable range of values for choice
of the averaging period, and is an appropriate length of time of
pollutant exposure to ensure protection of sensitive organisms.
EPA established a 4-day averaging period in the NTR. In settlement
of litigation on the NTR, EPA stated that it was ``in the midst of
conducting, sponsoring, or planning research related to the basis for
and application of'' water quality criteria and mentioned the issue of
averaging period. See Partial Settlement Agreement in American Forest
and Paper Ass'n, Inc. et al. v. U.S. EPA (Consolidated Case No. 93-0694
(RMU), D.D.C.). EPA is re-evaluating issues raised about averaging
periods and will, if appropriate, revise the 1985 Guidelines.
EPA received public comment relevant to the averaging period during
the comment period for the 1995 Amendments to the NTR (40 CFR 22228,
May 4, 1995), although these public comments did not address the
chronic averaging period separately from the allowable excursion
frequency and the design flow. These commenters argued that a once-in-
3-year excursion frequency for 4-day average concentrations, or a 7Q10
design flow, was unnecessarily restrictive. For chronic criteria, they
noted that EPA has approved the use of a 30Q3 design flow in Colorado,
a 30Q5 design flow in Maryland, and a 1 percent exceedance frequency in
Pennsylvania. Comments recommended that EPA use the 30Q5 design flow
for chronic criteria.
While EPA is undertaking analysis of the chronic design conditions
as part of the revisions to the 1985 Guidelines, EPA has not yet
completed this work. Until this work is complete, for the reasons set
forth in the TSD, EPA continues to believe that the 4-day chronic
averaging period represents a reasonable, defensible value for this
parameter.
g. Hardness
Freshwater aquatic life criteria for certain metals are expressed
as a function of hardness because hardness and/or water quality
characteristics that are usually correlated with hardness can reduce or
increase the toxicities of some metals. Hardness is used as a surrogate
for a number of water quality characteristics which affect the toxicity
of metals in a variety of ways. Increasing hardness has the effect of
decreasing the toxicity of metals. Water quality criteria to protect
aquatic life may be calculated at different concentrations of
hardnesses measured in mg/l as CaCO3.
Section 131.38(b)(2) of the proposed rule presents the hardness-
dependent equations for freshwater metals criteria. For example, using
the equation for zinc, the total recoverable CMCs at a hardness of 10,
50, 100 or 200 mg/l as CaCO3 are 17, 67, 120 and 220
g/l, respectively. Thus, the specific value in the table in
the proposed regulatory text is for illustrative purposes only. Most of
the data used to develop these hardness equations for deriving aquatic
life

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criteria for metals were in the range of 25 mg/l to 400 mg/l as
CaCO3, and the formulas are therefore most accurate in this
range. The majority of surface waters nationwide and in California have
a hardness of less than 400 mg/l as CaCO3.
In the past, EPA generally recommended that 25 mg/l as
CaCO3 be used as a default hardness value in deriving
freshwater aquatic life criteria for metals when the ambient (or
actual) hardness value is below 25 mg/l as CaCO3. However,
use of the approach results in criteria that may not be fully
protective. Therefore, for waters with a hardness of less than 25 mg/l
as CaCO3, criteria should be calculated using the actual
ambient hardness of the surface water.
In the past, EPA generally recommended that if the hardness was
over 400 mg/l, two options were available: (1) Calculate the criterion
using a default WER of 1.0 and using a hardness of 400 mg/l in the
hardness equation; or (2) calculate the criterion using a WER and the
actual ambient hardness of the surface water in the equation. Use of
the second option is expected to result in the level of protection
intended in the 1985 Guidelines whereas use of the first option is
thought to result in a lower aquatic life criterion. At high hardness
there is an indication that hardness and related inorganic water
quality characteristics do not have as much of an effect on toxicity of
metals as they do at lower hardnesses. Related water quality
characteristics do not correlate as well at higher hardnesses as they
do at lower hardnesses. Therefore, if hardness is over 400 mg/l as
CaCO3, a hardness of 400 mg/l as CaCO3 should be
used with a default WER of 1.0; alternatively, the WER and actual
hardness of the surface water may be used.
EPA requested comments in the NTR amendments on the use of actual
ambient hardness for calculating criteria when the hardness is below 25
mg/l as CaCO3, and when hardness is greater than 400 mg/l as
CaCO3. Most of the comments received were in favor of using
the actual hardness with the use of the water-effect ratio (1.0 unless
otherwise specified by the permitting authority) when the hardness is
greater than 400 mg/l as CaCO3. A few commenters did not
want the water-effect ratio to be mandatory in calculating hardness,
and other commenters had concerns about being responsible for deriving
an appropriate water-effect ratio. Overall, the commenters were in
favor of using the actual hardness when calculating hardness-dependent
freshwater metals criteria for hardness between 0-400 mg/l as
CaCO3. EPA took those comments into account in proposing
today's proposed rule.
A hardness equation is most accurate when the relationships between
hardness and the other important inorganic constituents, notably
alkalinity and pH, are nearly identical in all of the dilution waters
used in the toxicity tests and in the surface waters to which the
equation is to be applied. If an effluent raises hardness but not
alkalinity and/or pH, using the hardness of the downstream water might
provide a lower level of protection than intended by the 1985
guidelines. If it appears that an effluent causes hardness to be
inconsistent with alkalinity and/or pH, the intended level of
protection will usually be maintained or exceeded if either (1) data
are available to demonstrate that alkalinity and/or pH do not affect
the toxicity of the metal, or (2) the hardness used in the hardness
equation is the hardness of upstream water that does not contain the
effluent. The level of protection intended by the 1985 guidelines can
also be provided by using the WER procedure.
In some cases, capping hardness at 400 mg/l might result in a level
of protection that is higher than that intended by the 1985 guidelines,
but any such increase in the level of protection can be overcome by use
of the WER procedure.
For metals whose criteria are expressed as hardness equations, use
of the WER procedure will generally be intended to account for effects
of such water quality characteristics as total organic carbon on the
toxicities of metals. The WER procedure is equally useful for
accounting for any deviation from a hardness equation in a site water.

3. Human Health Criteria

EPA's CWA section 304(a) human health criteria guidance provides
criteria recommendations to minimize adverse human effects due to
substances in ambient water. EPA's CWA section 304(a) criteria guidance
for human health are based on two types of biological endpoints: (1)
Carcinogenicity and (2) systemic toxicity (i.e., all other adverse
effects other than cancer). Thus, there are two procedures for
assessing these health effects: one for carcinogens and one for non-
carcinogens.
EPA's human health guidelines assume that carcinogenicity is a
``non-threshold phenomenon,'' that is, there are no ``safe'' or ``no-
effect levels'' because even extremely small doses are assumed to cause
a finite increase in the incidence of the effect (i.e., cancer).
Therefore, EPA's water quality criteria guidance for carcinogens are
presented as pollutant concentrations corresponding to increases in the
risk of developing cancer. See Human Health Guidelines at 45 FR 79347.
For pollutants that do not manifest any apparent carcinogenic
effect in animal studies (i.e., systemic toxicants), EPA assumes that
the pollutant has a threshold below which no effect will be observed.
This assumption is based on the premise that a physiological mechanism
exists within living organisms to avoid or overcome the adverse effect
of the pollutant below the threshold concentration.
The human health risks of a substance cannot be determined with any
degree of confidence unless dose-response relationships are quantified.
Therefore, a dose-response assessment is required before a criterion
can be calculated. The dose-response assessment determines the
quantitative relationships between the amount of exposure to a
substance and the onset of toxic injury or disease. Data for
determining dose-response relationships are typically derived from
animal studies, or less frequently, from epidemiological studies in
exposed populations.
The dose-response information needed for carcinogens is an estimate
of the carcinogenic potency of the compound. Carcinogenic potency is
defined here as a general term for a chemical's human cancer-causing
potential. This term is often used loosely to refer to the more
specific carcinogenic or cancer slope factor which is defined as an
estimate of carcinogenic potency derived from animal studies or
epidemiological data of human exposure. It is based on extrapolation
from test exposures of high doses over relatively short periods of time
to more realistic low doses over a lifetime exposure period by use of
linear extrapolation models. The cancer slope factor, q1*, is EPA's
estimate of carcinogenic potency and is intended to be a conservative
upper bound estimate (e.g. 95% upper bound confidence limit).
For non-carcinogens, EPA uses the reference dose (RfD) as the dose
response parameter in calculating the criteria. For non-carcinogens,
oral RfD assessments (hereinafter simply ``RfDs'') are developed based
on pollutant concentrations that cause threshold effects. The RfD is an
estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily exposure to the human population (including sensitive subgroups)
that is likely to be without appreciable risk of deleterious effects
during a lifetime. See Human Health

[[Page 42176]]

Guidelines. The RfD was formerly referred to as an ``Acceptable Daily
Intake'' or ADI. The RfD is useful as a reference point for gauging the
potential effect of other doses. Doses that are less than the RfD are
not likely to be associated with any health risks, and are therefore
less likely to be of regulatory concern. As the frequency of exposures
exceeding the RfD increases and as the size of the excess increases,
the probability increases that adverse effect may be observed in a
human population. Nonetheless, a clear conclusion cannot be
categorically drawn that all doses below the RfD are ``acceptable'' and
that all doses in excess of the RfD are ``unacceptable.'' In
extrapolating non-carcinogen animal test data to humans to derive an
RfD, EPA divides a no-observed-effect dose observed in animal studies
by an ``uncertainty factor'' which is based on professional judgment of
toxicologists and typically ranges from 10 to 10,000.
For CWA section 304(a) human health criteria development, EPA
typically considers only exposures to a pollutant that occur through
the ingestion of water and contaminated fish and shellfish. Thus, the
criteria are based on an assessment of risks related to the surface
water exposure route only where designated uses are drinking water and
fish and shellfish consumption.
The assumed exposure pathways in calculating the criteria are the
consumption of 2 liters per day of water at the criteria concentration
and the consumption of 6.5 grams per day of fish and shellfish
contaminated at a level equal to the criteria concentration but
multiplied by a ``bioconcentration factor.'' The use of fish and
shellfish consumption as an exposure factor requires the quantification
of pollutant residues in the edible portions of the ingested species.
Bioconcentration factors (BCFs) are used to relate pollutant
residues in aquatic organisms to the pollutant concentration in ambient
waters. BCFs are quantified by various procedures depending on the
lipid solubility of the pollutant. For lipid soluble pollutants, the
average BCF is calculated from the weighted average percent lipids in
the edible portions of fish and shellfish, which is about 3%; or it is
calculated from theoretical considerations using the octanol/water
partition coefficient. For non-lipid soluble compounds, the BCF is
determined empirically. The assumed water consumption is taken from the
National Academy of Sciences publication Drinking Water and Health
(1977). (Referenced in the Human Health Guidelines.) This value is
appropriate as it includes a margin of safety so that the general
population is protected. See also EPA's discussion of the 2.0 liters/
day assumption at 61 FR 65183 (Dec. 11, 1996). The 6.5 grams per day
contaminated fish and shellfish consumption value was equivalent to the
average per-capita consumption rate of all (contaminated and non-
contaminated) freshwater and estuarine fish and shellfish for the U.S.
population. See Human Health Guidelines.
EPA assumes in calculating water quality criteria that the exposed
individual is an average adult with body weight of 70 kilograms. The
issue of concern is dose per kilogram of body weight. EPA assumes 6.5
grams per day of contaminated fish and shellfish consumption and 2.0
liters per day of contaminated drinking water consumption for a 70
kilogram person in calculating the criteria. Persons of smaller body
weight are expected to ingest less contaminated fish and shellfish and
water, so the dose per kilogram of body weight is generally expected to
be roughly comparable.
There may be subpopulations within a state, such as subsistence
anglers who as a result of greater exposure to a contaminant, are at
greater risk than the hypothetical 70

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A97-20173. Public record. Not legal advice.