[Federal Register Volume 62, Number 150 (Tuesday, August 5, 1997)]
[Proposed Rules]
[Pages 42160-42208]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-20173]



[[Page 42159]]

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Part II





Environmental Protection Agency





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40 CFR Part 131



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

Federal Register / Vol. 62, No. 150 / Tuesday, August 5, 1997 / 
Proposed Rules

[[Page 42160]]


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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.

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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. 
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[[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 <greek-m>g/l (maximum), a zinc criterion of 16 
<greek-m>g/l (maximum) and a cadmium criterion of 0.22 <greek-m>g/l 
(maximum), all in the dissolved form using a hardness of 40 mg/l as 
CaCO<INF>3</INF>. (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 
<greek-m>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 <greek-m>g/l (monthly 
mean); however, EPA disapproved a State-adopted site-specific selenium 
criterion of 8 <greek-m>g/l (monthly mean--critical year only) for 
these waters. Subsequently, EPA promulgated a chronic selenium 
criterion of 5 <greek-m>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 <greek-m>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 <greek-m>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 <greek-m>g/l:

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

[[Page 42169]]

                                                                                                                
Cadmium.................................................   <SUP>1,2,4 4.3     <SUP>1,2,4 2.2        <SUP>1,5 3.7     <SUP>1,5 1.0   
Chromium (VI)...........................................    <SUP>1,2 16        <SUP>1,2 11         <SUP>1,3 15      <SUP>1,3 10     
Copper..................................................  <SUP>1,2,4 13       <SUP>1,2,4 9.0       <SUP>1,5 17      <SUP>1,5 11     
Nickel..................................................  <SUP>1,2,4 470     <SUP>1,2,4 52       <SUP>1,5 1400     <SUP>1,5 160     
Zinc....................................................  <SUP>1,2,4 120     <SUP>1,2,4 120       <SUP>1,5 110     <SUP>1,5 100     
Pentachloro-phenol......................................    <SUP>2,6 19        <SUP>2,6 15           <SUP>6 20        <SUP>6 13     
Lindane (gamma-BHC).....................................       <SUP>2 0.95   <SUP>............        <SUP>7 2           0.08  
Dieldrin................................................       <SUP>2 0.24        <SUP>2 0.056        <SUP>7 2.5         0.0019
Endrin..................................................       <SUP>2 0.086       <SUP>2 0.036        <SUP>7 0.18        0.0023
Mercury.................................................   <SUP>1,2,3 1.4     <SUP>1,2,3 0.77       <SUP>1,3 2.1         0.012 
PCBs....................................................  ............     <SUP>8,9 0.014  <SUP>............   <SUP>8,10 0.014 
Mercury.................................................     <SUP>1,3 1.8       <SUP>1,3 0.94       <SUP>1,3 1.8         0.025 
PCBs....................................................  ............     <SUP>8,9 0.03   <SUP>............   <SUP>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    
  CaCO<INF>3 ) 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 CaCO<INF>3.          
\5\ Freshwater aquatic life criteria for these metals are expressed as a function of total hardness (mg/l as    
  CaCO<INF>3), 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 CaCO<INF>3 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 <greek-m>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 <greek-m>g/l, which it rounded to 20 
<greek-m>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 <greek-m>g/l and a CCC of 5 <greek-m>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 <greek-m>g/l, while a 
CMC for selenate (selenium VI) might have been 12.82 <greek-m>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 
<greek-m>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 <SUP>b, <SUP>c,   magnae
                                   <SUP>a (mg/l)        <SUP>d (mg/l)       <SUP>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  .......
------------------------------------------------------------------------
<SUP>a 10-day LC50 (Niimi and LaHam 1976).            <SUP>d 48-hr LC50 (Maier et 
  al. 1993).                                                            
<SUP>b 48-hr LC50 (Ingersoll et al. 1990).                 <SUP>e 48-hr LC50      
  (Maier et al. 1993).                                                  
<SUP>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 <greek-m>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       <greek-m>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 <ls-thn-eq> 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 c<INF>1</INF> is the concentration of selenite and other 
selenium assumed to have the toxicity of selenite, c<INF>2</INF> is the 
concentration and selenate and other selenium assumed to have the 
toxicity of selenate; and CMC<INF>1</INF> and CMC<INF>2</INF> are the 
CMCs for selenite and selenate respectively. A Criterion Maximum 
Concentration, CMC<INF>Se</INF>, 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 f<INF>1</INF> and f<INF>2</INF> are the fractions of total 
selenium that are treated as selenite and selenate respectively (that 
is, f<INF>1</INF>=c<INF>1</INF>/c<INF>Se</INF> and 
c<INF>Se</INF>=c<INF>1</INF>+c<INF>2</INF>), and 
f<INF>1</INF>+f<INF>2</INF>=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 
(c<INF>1</INF>=0) then the Criterion Maximum Concentration 
(CMC<INF>Se</INF>) would be calculated to be 12.82 <greek-m>g/l, the 
CMC of selenate. On the other hand, if the concentrations of selenate 
and other selenium are zero, then CMC<INF>Se</INF> would be calculated 
to be 185.9 <greek-m>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 
CaCO<INF>3</INF> 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

[[Page 42174]]

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 <greek-m>g/l (CMC) and 3.1 <greek-m>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 <greek-m>g/l dissolved and a 
CCC of 3.1 <greek-m>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 CaCO<INF>3</INF>.
    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 CaCO<INF>3</INF> are 17, 67, 120 and 220 
<greek-m>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

[[Page 42175]]

criteria for metals were in the range of 25 mg/l to 400 mg/l as 
CaCO<INF>3</INF>, 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 CaCO<INF>3</INF>.
    In the past, EPA generally recommended that 25 mg/l as 
CaCO<INF>3</INF> 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 CaCO<INF>3</INF>. 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 CaCO<INF>3</INF>, 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 
CaCO<INF>3</INF>, a hardness of 400 mg/l as CaCO<INF>3</INF> 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 CaCO<INF>3</INF>, and when hardness is greater than 400 mg/l as 
CaCO<INF>3</INF>. 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 CaCO<INF>3</INF>. 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 
CaCO<INF>3</INF>. 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 kilogram person eating 6.5 grams 
per day of maximally contaminated fish and shellfish and drinking 2.0 
liters per day of maximally contaminated drinking water. For example, 
individuals that ingest ten times more of a carcinogenic pollutant than 
is assumed in derivation of the criteria at a 10<SUP>-6</SUP> risk 
level will be protected to a 10<SUP>-5</SUP> level, which EPA has 
historically considered to be adequately protective. There may, 
nevertheless, be circumstances where site-specific numeric criteria 
that are more stringent than the statewide criteria are necessary to 
adequately protect highly exposed subpopulations. Although EPA intends 
to focus on promulgation of appropriate statewide criteria that will 
reduce risks to all exposed individuals, including highly exposed 
subpopulations, site-specific criteria may be developed subsequently by 
the State where warranted to provide necessary additional protection. 
See Human Health Guidelines, Issue 8.
    EPA has a process to develop a scientific consensus on oral 
reference dose assessments and carcinogenicity assessments (hereinafter 
simply cancer slope factors or slope factors or q1*s). Through this 
process, EPA develops a consensus of Agency opinion which is then used 
throughout EPA in risk management decision-making. EPA maintains an 
electronic data base which contains the official Agency consensus for 
oral RfD assessments and carcinogenicity assessments which is known as 
the Integrated Risk Information System (IRIS). It is available for use 
by the public on the National Institutes of Health's National Library 
of Medicine's TOXNET system, and through diskettes from the National 
Technical Information Service (NTIS). (NTIS access number is PB 90-
591330.)
    Section 304(a)(1) of the CWA requires EPA to periodically revise 
its criteria guidance to reflect the latest scientific knowledge: ``(A) 
on the kind and extent of all identifiable effects on health and 
welfare * * * ; (B) on the concentration and dispersal of pollutants, 
or their byproducts, through biological, physical, and chemical 
processes; and (C) on the effects of pollutants on the biological 
community diversity, productivity, and stability, including information 
on the factors affecting eutrophication rates of organic and inorganic 
sedimentation for varying types of receiving waters.'' In developing 
up-to-date water quality criteria for the protection of human health, 
EPA consistently relies upon the most recent IRIS values (RfDs and 
q1*s) as the toxicological basis in the criterion calculation. IRIS 
reflects EPA's most current consensus on the toxicological assessment 
for a chemical. In developing the criteria in today's proposed rule, 
the most recent IRIS values were used together with currently accepted 
exposure parameters for bioconcentration, fish and shellfish and water 
consumption, and body weight. The IRIS cover sheet for each pollutant 
criteria included in today's proposed rule is contained in the 
administrative record.
    For the human health criteria included in today's proposed rule, 
EPA used the Human Health Guidelines on which criteria recommendations 
from the appropriate CWA section 304(a) criteria guidance document were 
based. (These documents are also placed in the administrative record 
for today's proposed rule.) Where EPA has changed any parameters in 
IRIS used in criteria derivation since issuance of the criteria 
guidance document, EPA recalculated the criteria recommendation with 
the latest IRIS information. Thus, there are differences between the 
original criteria guidance document recommendations, and those in this 
proposed rule, but this proposed rule presents EPA's most current CWA 
section 304(a) criteria recommendation. The basis (q1* or RfD/ADI) and 
BCF for each pollutant criterion in today's proposed rule is contained 
in the rule's Administrative Record Matrix which is included in the 
administrative record for the proposed

[[Page 42177]]

rule. In addition, all recalculated human health numbers are denoted by 
an ``a'' in the criteria matrix in 40 CFR 131.38(b)(1) of the proposed 
rule. The pollutants for which a revised human health criterion has 
been calculated since the December 1992 NTR include: mercury; 
dichlorobromomethane; 1,2-dichloropropane; 1,2-trans-dichloroethylene; 
2,4-dimethylphenol; acenaphthene; benzo(a)anthracene; benzo(a)pyrene; 
benzo(b)flouranthene; benzo(k)flouranthene; 2-chloronaphthalene; 
chrysene; dibenzo(a,h)anthracene; indeno(1,2,3-cd)pyrene; N-nitrosodi-
n-propylamine; alpha-endosulfan; beta-endosulfan; endosulfan sulfate; 
2-chlorophenol; butylbenzyl phthalate; and polychlorinated biphenyls.
    In November of 1991, the proposed NTR presented criteria for 
several pollutants in parentheses. These were pollutants for which, in 
1980, insufficient information existed to develop human health water 
quality criteria, but for which, in 1991, sufficient information 
existed. Since these criteria did not undergo the public review and 
comment in a manner similar to the other water quality criteria 
presented in the NTR (for which sufficient information was available in 
1980 to develop a criterion, as presented in the 1980 criteria guidance 
documents), they were not proposed for adoption into the water quality 
criteria, but were presented to serve as notice for inclusion in future 
state triennial reviews. Today's rule proposes criteria for these nine 
pollutants: copper; 1, 2-dichloropropane; 1,2-trans-dichloroethylene; 
2,4-dimethylphenol; acenaphthene; 2-chloronaphthalene; N-nitrosodi-n-
propylamine; 2-chlorophenol; butylbenzene phthalate. All the criteria 
are based on IRIS values--either an RfD or q1*--which were listed on 
IRIS as of November 1991, the date of the proposed NTR. These values 
have not changed since the final NTR was published in December of 1992. 
The rule's Administrative Record Matrix in the administrative record of 
today's proposed rule contains the specific RfDs, q1*s, and BCFs used 
in calculating these criteria.
    Potential Changes to the Human Health Criteria Methodology: EPA 
expects to propose in the near future several changes to the 1980 
ambient water quality criteria derivation guidelines (the Human Health 
Guidelines). The methodology revisions anticipated reflect significant 
scientific advances that have occurred during the past several years in 
such key areas as cancer and noncancer risk assessments, exposure 
assessments and bioaccumulation. Some anticipated areas of major 
change, which are being considered in this process include:
    1. The new Proposed Guidelines on Carcinogen Risk Assessment 
emphasize the consideration of mode of action and route of exposure. A 
weight of evidence narrative will be used instead of the traditional 
alphanumeric classification (e.g., A, B, C, D, E carcinogens). For dose 
response assessments, two steps will be involved: determining the range 
of observation (observed effect) and the range of extrapolation. To 
characterize the cancer potency, a biologically-based chemical-specific 
model will be used. In many cases, however, sufficient data may not 
exist to apply a biological based model. In these cases, linear and 
nonlinear defaults will be used. A linear default will be used for 
those chemicals which indicate they are DNA reactive or when other 
evidence supports linearity. In addition, if a chemical is not DNA 
reactive but insufficient data exist to characterize a nonlinear mode 
of action, linearity will be assumed and a linear default will be 
recommended. The nonlinear default (margin of exposure approach) will 
be used for those chemicals which are not DNA reactive and for those 
for which sufficient data to characterize a nonlinear mode of action 
exist.
    2. For noncarcinogens, the concept of an expressing an RfD as a 
range rather than a single value will be presented for comment. In 
developing water quality criteria, EPA will provide a default RfD 
which, in most cases, will be the midpoint of the range, commonly 
referred to as the point estimate. Alternative approaches, such as the 
benchmark dose and categorical regression analysis may be employed in 
developing an RfD and analyzing the risk above the RfD point estimate.
    3. Default fish and shellfish consumption values are presented for 
the general population, for sportfishers, and for subsistence fishers, 
replacing the single value of 6.5 grams/day used in the 1980 guidance. 
States may use a fish and shellfish intake level derived from local 
data on fish and shellfish consumption in place of the default values 
provided. However, the fish and shellfish intake level chosen must be 
protective of highly exposed individuals in the population.
    4. All criteria should be derived using a bioaccumulation factor 
(BAF); none should be derived using a bioconcentration factor (BCF), 
which was used in the 1980 guidance.
    5. As an alternative to expressing ambient water quality criteria 
as a water concentration, criteria may also be expressed in terms of 
fish tissue concentration. For some substances, particularly those that 
are expected to exhibit substantial bioaccumulation, the ambient water 
quality criteria derived may have extremely low values, possibly below 
the practical limits for detecting and quantifying the substance in the 
water column. It may be more practical and meaningful in these cases to 
focus on the concentration of those substances in fish tissue, since 
fish ingestion would be the predominant source of exposure for these 
substances that bioaccumulate.
    6. When deriving ambient water quality criteria for noncarcinogens 
and nonlinear carcinogens, a factor (referred to as the relative source 
contribution) should be included to account for other non-water 
exposure sources so that the entire RfD will not be not allocated to 
drinking water and fish consumption alone.
    For more details on these changes and others, please refer to the 
upcoming Federal Register notice.
    It should be noted that the changes outlined above may result in 
significant numeric changes in the ambient water quality criteria. For 
example, for those chemicals which are bioaccumulative in nature (e.g., 
with bioconcentration factors (BCFs) of 300 or more), bioaccumulation 
factors may be developed which are 1-3 orders of magnitude greater than 
the BCFs developed in 1980. This would result in a criterion which is 
1-3 orders of magnitude more stringent, if all other parameters (such 
as RfDs and q1 *s) remain roughly unchanged.
    EPA will continue to rely on existing criteria as the basis for 
regulatory and non-regulatory decisions, until EPA revises and reissues 
a 304(a) criteria guidance using the revised final human health 
criterion methodology. The existing criteria are still viewed as 
scientifically acceptable by EPA. The intention of the methodology 
revisions is to present the latest scientific advancements in the areas 
of risk and exposure assessment in order to incrementally improve the 
already sound toxicological and exposure bases for these criteria. As 
EPA's current human health criteria are the product of several years 
worth of development, it is reasonable to assume that revisiting all 
existing criteria could require comparable amounts of time and 
resources. Given these circumstances, EPA is proposing a process for 
revisiting these criteria as part of the overall revisions to the 
methodology for deriving human health criteria that is expected to be 
published in the Federal Register in 1997.

[[Page 42178]]

    The State of California in its Ocean Plan, adopted in 1990 and 
approved by EPA in 1991, established numerical water quality criteria 
using an average fish and shellfish consumption rate of 23 grams per 
day. This value is based on an earlier California Department of Health 
Services estimate. The State is currently in the process of readopting 
its water quality control plans for inland surface waters, enclosed 
bays, and estuaries. The State intends to consider information on fish 
and shellfish consumption rates evaluated and summarized in a recent 
report prepared by the State's Office of Environmental Health Hazard 
Assessment. The report, which is undergoing final evaluation, is 
expected to be made public in 1997. EPA supports the State's use of any 
appropriate higher state-specific fish and shellfish consumption rates 
in its readoption of criteria in its statewide plans.
a. 2,3,7,8-TCDD (Dioxin) Criteria
    In today's action, EPA is proposing human health water quality 
criteria for 2,3,7,8-tetrachlorodibenzo-p-dioxin (``dioxin'') at the 
same levels as promulgated in the NTR, as amended. These criteria are 
derived from EPA's 1984 CWA section 304(a) criteria guidance document 
for dioxin.
    EPA has been evaluating the health threat posed by dioxin nearly 
continuously for well over a decade. Following issuance of the 1984 
criteria guidance document, evaluating the health effects of dioxin and 
recommending human health criteria for dioxin, EPA prepared draft 
reassessments reviewing new scientific information relating to dioxin 
in 1985 and 1988. EPA's Science Advisory Board (SAB), reviewing the 
1988 draft reassessment, concluded that while the risk assessment 
approach used in 1984 criteria guidance document had inadequacies, a 
better alternative was unavailable (see SAB's Dioxin Panel Review of 
Documents from the Office or Research and Development relating to the 
Risk and Exposure Assessment of 2,3,7,8-TCDD (EPA--SAB-EC-90-003, 
November 28, 1989) included in the administrative record for today's 
proposed rule). Between 1988 and 1990, EPA issued numerous reports and 
guidances relating to the control of dioxin discharges from pulp and 
paper mills. See e.g., EPA Memorandum, ``Strategy for the Regulation of 
Discharges of PHDDs & PHDFs from Pulp and Paper Mills to the Waters of 
the United States,'' from Asst. Administrator for Water to Regional 
Water Mgmt Div. Directors and NPDES State Directors, dated May 21, 1990 
(AR NL-16); EPA Memorandum, ``State Policies, Water Quality Standards, 
and Permit Limitations Related to 2,3,7,8-TCDD in Surface Water,'' from 
Assistant Administrators to Water Management Div. Directors, dated 
January 5, 1990 (AR VA-66). These documents are available in the 
administrative record for today's proposed rule.
    In 1991, EPA's Administrator announced another scientific 
reassessment of the risks of exposure to dioxin (see Memorandum from 
Administrator William K. Reilly to Erich W. Bretthauer, Assistant 
Administrator for Research and Development and E. Donald Elliott, 
General Counsel, entitled Dioxin: Follow-Up to Briefing on Scientific 
Developments, April 8, 1991, included in the administrative record for 
today's proposed rule). At that time, the Administrator made clear that 
while the reassessment was underway, EPA would continue to regulate 
dioxin in accordance with existing Agency policy and existing risk 
methodologies. Thereafter, the Agency proceeded to regulate dioxin in a 
number of environmental programs, including standards under the Safe 
Drinking Water Act and the Clean Water Act.
    The Administrator's promulgation of the dioxin human health 
criteria in the 1992 NTR affirmed his decision that the ongoing 
reassessment should not defer or delay regulating this potent 
contaminant, and further, that the risk assessment in the 1984 criteria 
guidance document for dioxin continued to be scientifically defensible. 
Until the reassessment process was completed, the Agency could not 
``say with any certainty what the degree or directions of any changes 
in the risk estimates might be'' (57 F. R. at 60863-64).
    The basis for the dioxin criteria as well as the decision to 
include the dioxin criteria in the 1992 NTR pending the results of the 
reassessment were challenged. See American Forest and Paper Ass'n, Inc. 
et al. v. U.S. EPA (Consolidated Case No. 93-0694 (RMU) D.D.C.). By 
order dated September 4, 1996, the Court upheld EPA's decision. EPA's 
brief and the Court's decision are included in the administrative 
record for today's proposed rule.
    EPA has undertaken significant effort toward completion of the 
dioxin reassessment. On September 13, 1994, EPA released for public 
review and comment a draft reassessment of toxicity and exposure to 
dioxin. See Health Assessment Document for 2,3,7,8-Tetrachlorobenzo-p-
Dioxin (TCDD) and Related Compounds, U.S. EPA, 1994. EPA is currently 
addressing comments made by the public and the SAB and anticipates that 
the final revised reassessment will go to the SAB in the near future. 
With today's proposal, the Administrator reaffirms that, 
notwithstanding the on-going risk reassessment, EPA intends to continue 
to regulate dioxin to avoid further harm to public health, and the 
basis for the dioxin criteria, both in terms of the cancer potency and 
the exposure estimates, remains scientifically defensible. The fact 
that EPA is reassessing the risk of dioxin, virtually a continuous 
process to evaluate new scientific information, does not mean that the 
current risk assessment is ``wrong''. It continues to be EPA's position 
that until the risk assessment for dioxin is revised, EPA supports and 
will continue to use the existing risk assessment for the regulation of 
dioxin in the environment. Accordingly, EPA today proposes dioxin 
criteria based on the 1984 criteria guidance document for dioxin and 
promulgated in the NTR in 1992.
    Toxicity Equivalency: The State of California, in its 1991 water 
quality control plans, adopted human health criteria for dioxin and 
dioxin-like compounds based on the concept of toxicity equivalency 
(TEQ) using toxicity equivalency factors (TEFs). EPA Region 9 reviewed 
and approved the State's use of the TEQ concept and TEFs in setting the 
State's human health water quality criteria for dioxin and dioxin-like 
compounds.
    In 1987, EPA formally embraced the TEQ concept as an interim 
procedure to estimate the risks associated with exposures to 210 
chlorinated dibenzo-p-dioxin and chlorinated dibenzofuran (CDD/CDF) 
congeners, including 2,3,7,8-TCDD. This procedure uses a set of derived 
TEFs to convert the concentration of any CDD/CDF congener into an 
equivalent concentration of 2,3,7,8-TCDD. In 1989, EPA updated its TEFs 
based on an examination of relevant scientific evidence and a 
recognition of the value of international consistency. This updated 
information can be found in EPA's 1989 Update to the Interim Procedures 
for Estimating Risks Associated with Exposures to Mixtures of 
Chlorinated Dibenzo-p-dioxins and -dibenzofurans (CDDs and CDFs) (EPA /
625/3-89/016, March 1989). EPA had been active in an international 
effort aimed at adopting a common set of TEFs (International TEFs/89 or 
I-TEFs/89), to facilitate information exchange on environmental 
contamination of CDD/CDF. This document reflects EPA's support of an 
internationally consistent set of TEFs, the I-TEFs/89.
    EPA uses I-TEFs/89 in many of its regulatory programs, and 
encourages

[[Page 42179]]

their use in state programs. EPA supports and encourages the State of 
California's use of EPA's 1989 Interim Procedures in implementing the 
2,3,7,8-TCDD water quality criteria contained in today's proposed rule. 
The concept of TEQ and the use of the I-TEFs/89, as outlined in EPA's 
1989 Interim Procedures, provide valuable guidance in using the 
2,3,7,8-TCDD water quality criteria in setting National Pollutant 
Discharge Elimination System (NPDES) water quality-based permit limits 
that are protective of human health for dioxin and dioxin-like 
compounds.
b. Arsenic Criteria
    EPA is not proposing human health criteria for arsenic in today's 
proposed rule. EPA recognizes that EPA promulgated human health water 
quality criteria for arsenic for a number of states in 1992 based on 
EPA's 1980 section 304(a) criteria guidance for arsenic as updated in 
IRIS. However, a number of issues and uncertainties have arisen 
concerning the health effects of arsenic. These issues and 
uncertainties (summarized in ``Issues Related to Health Risk of 
Arsenic'' contained in the administrative record for today's proposed 
rule) include arsenic exposure evaluations, metabolism and 
detoxification processes, analytical methods, and effects at low doses. 
EPA has determined that these issues and uncertainties are sufficiently 
significant to necessitate a careful evaluation of the risks of arsenic 
exposure before the Agency promulgates water quality criteria for 
arsenic in additional states. Today's decision is consistent with the 
recent decision by the Assistant Administrator for Water (Memorandum 
from R. Perciasepe to Assistant and Regional Administrators dated 
February 6, 1995, also included in the administrative record) deferring 
the revision of the drinking water standard of 0.05 mg/l for arsenic 
pending, among other things, the review of the risk assessment for 
arsenic. This review is currently underway.
    Given these circumstances, EPA has made a risk management decision 
not to propose human health criteria for arsenic. Permitting 
authorities in California should rely on existing narrative water 
quality criteria to establish effluent limitations as necessary for 
arsenic. California has previously expressed its science and policy 
position by establishing a criterion level of 5 <greek-m>g/l for 
arsenic; EPA recommends that permitting authorities refer to that value 
in evaluating and interpreting the narrative water quality criteria.
c. Mercury Criteria
    The criteria proposed here use the latest RfD in EPA's Integrated 
Risk Information System (IRIS) and the weighted average practical 
bioconcentration factor (PBCF) from the 1980 section 304(a) criteria 
guidance document for mercury. EPA considered the approach used in the 
Great Lakes Water Quality Initiative (GLI) incorporating 
Bioaccumulation Factors (BAFs), but rejected this approach for reasons 
stated below. The equation used here to derive an ambient water quality 
criterion for mercury from exposure to organisms and water is the 
following:
    For organism and water consumption:
    [GRAPHIC] [TIFF OMITTED] TP05AU97.002
    
Where:

RfD = Reference Dose
BW = Body Weight
WC = Water Consumption
FC = Total Fish and Shellfish Consumption per Day
PBCF = Practical Bioconcentration Factor (weighted average)

    For mercury, the most current RfD from IRIS is 1 x 10<SUP>-4</SUP> 
mg/kg/day. The RfD is derived from a benchmark dose analysis using a 
parts per million (ppm) maternal hair concentration as the exposure 
surrogate and the combination of all neurological effects in infants as 
the response variable from the Marsh et. al (1987) study. A Weibel 
model for extra risk was used. The resulting estimated dose at 10% 
extra risk was 11 ppm of maternal hair, or about 1 x 10<SUP>-3</SUP> 
mg/kg/day. An uncertainty factor of 10 was included to arrive at an RfD 
of 1 x 10<SUP>-4</SUP> mg/kg/day. This factor is composed of a half-log 
of 10 for within-human variability and a half log of 10 for database 
insufficiency, notably the lack of a two generation reproductive study.
    The body weight used in the equation for the mercury criteria, as 
discussed in the Human Health Guidelines, is a mean adult human body 
weight of 70 kg. The drinking water consumption rate, as discussed in 
the Human Health Guidelines, is 2.0 liters per day.
    The fish and shellfish consumption for mercury takes into account 
both average fish and shellfish consumption and average intake from 
each body of water. The value for the fish and shellfish consumption is 
based on the average total intake of fish and shellfish from fresh 
water, estuarine coastal and open oceans (18.7 g/day). The average 
individual fish and shellfish consumption from freshwater bodies is 
1.72 g/day (0.00172 kg), from estuarine-coastal waters is 4.78 g/day 
(0.00478 kg), and from open oceans is 12.2 g/day (0.0122 kg). Species 
of fish and shellfish used in the calculation are those from which 
information was available on human consumption on average mercury 
concentration in edible tissue. See Ambient Water Quality Criteria for 
Mercury (EPA 440/5-80-058).
    The BCF is defined as the ratio of chemical concentration in the 
organism to that in surrounding water. Bioconcentration occurs through 
uptake and retention of a substance from water only, through gill 
membranes or other external body surfaces. In the context of setting 
exposure criteria it is generally understood that the terms ``BCF'' and 
``steady-state BCF'' are synonymous. A steady-state condition occurs 
when the organism is exposed for a sufficient length of time that the 
ratio does not change substantially.
    The BCFs that were used herein are the ``Practical Bioconcentration 
Factors (PBCFs)'' that were derived in 1980: 5500 for fresh water, 3765 
for estuarine coastal waters, and 9000 for open oceans. See pages C-
100-1 of Ambient Water Quality Criteria for Mercury (EPA 440/5-80-058) 
for a complete discussion on the PBCF. Because of the way they were 
derived, these PBCFs take into account uptake from food as well as 
uptake from water. A weighted average PBCF was calculated to take into 
account the average consumption from the three waters using the 
following equation:

[[Page 42180]]

[GRAPHIC] [TIFF OMITTED] TP05AU97.003


Given the large value for the weighted average PBCF, the contribution 
of drinking water to total daily intake is negligible so that 
assumptions concerning the chemical form of mercury in drinking water 
become less important. The human health mercury criteria proposed for 
this rule are based on the latest RfD as listed in IRIS and a weighted 
PBCF from the 1980 304(a) criteria guidance document for mercury.
    On March 23, 1995 (60 FR 15366), EPA promulgated the Great Lakes 
Water Quality Initiative (GLI). The GLI incorporated bioaccumulation 
factors (BAFs) in the derivation of criteria to protect human health 
because it is believed BAFs are a better predictor than BCFs of the 
concentration of a chemical within fish tissue as it includes 
consideration of the uptake of contaminants from all routes of 
exposure. A bioaccumulation factor is defined as the ratio (in L/kg) of 
a substance's concentration in tissue to the concentration in the 
ambient water, in situations where both the organism and its food are 
exposed and the ratio does not change substantially over time. The 
final GLI establishes a hierarchy of four methods for deriving BAFs for 
non-polar organic chemicals: (1) Field-measured BAFs; (2) predicted BAF 
derived using a field-measured biota-sediment accumulation factor; (3) 
predicted BAFs derived by multiplying a laboratory-measured BCF by a 
food chain multiplier; and 4) predicted BAFs derived by multiplying a 
BCF calculated from the log Kow by a food-chain multiplier. The final 
GLI developed BAFs for trophic levels three and four fish of the Great 
Lakes Basin. Respectively, the BAFs for mercury for trophic level 3 and 
4 fish were: 27,900 and 140,000.
    The BAF promulgated in the GLI was developed specifically for the 
Great Lakes System. It is uncertain whether the BAFs of 27,900 and 
140,000 are appropriate for use in California at this time, and thus, 
this proposal does not use the BAF in setting the human health criteria 
for mercury. To a considerable degree the magnitude of the BAF for 
mercury in a given system depends on how much of the total mercury in 
that system is present in the methylated form. Methylation rates very 
widely from one aquatic system to another for reasons that are not 
fully understood. Lacking the data, it is difficult to determine if the 
BAF used in the GLI represent the potential for mercury bioaccumulation 
in surface waters in California. It should be noted, however, that 
there is no scientific reason to believe that a true average BAF in 
California, were it known, would be lower than that developed for the 
Great Lakes basin; that is, the true average for California could be 
higher or lower than the BAF developed for the GLI.
    EPA is developing a national BAF for mercury. The mercury BAF is 
part of the Mercury Study Report to Congress: SAB Review Draft (The 
Draft Report to Congress) . The Draft Report to Congress is currently 
available through NTIS (EPA-452/R-96-001a-h) . The next step is for the 
SAB to review the Draft Report to Congress. After the SAB reviews the 
Draft Report and the Agency makes changes based on their comments, the 
Report to Congress will be released with a final national BAF for 
mercury. Once the Report to Congress has been publicly reviewed, and 
finalized, the Agency will consider the science and could make changes 
to the section 304(a) criteria guidance for mercury to reflect the 
recommendation of the Report to Congress. If the section 304(a) 
criteria guidance for mercury changes, states will be expected to 
review their water quality standards for mercury and determine if their 
standards are protective.
d. Polychlorinated Biphenyls (PCBs) Criteria
    The NTR, as amended, calculated human health criteria for PCBs 
using a cancer potency factor of 7.7 per (mg/kg)/day from the Agency's 
IRIS. This cancer potency factor was derived from the Norback and 
Weltman (1985) study which looked at rats that were fed Aroclor 1260. 
The study used the linearized multistage model with a default cross-
species scaling factor (body weight ratio to the 2/3 power). Although 
it is known that PCB congeners vary greatly as to their potency in 
producing biological effects, for purposes of its carcinogenicity 
assessment, EPA considered Aroclor 1260 to be representative of all PCB 
mixtures. The Agency did not pool data from all available congener 
studies or generate a geometric mean from these studies, since the 
Norback and Weltman study was judged by EPA as acceptable, and not of 
marginal quality, in design or conduct as compared with other studies. 
Thereafter, the Institute for Evaluating Health Risks (IEHR, 1991) 
reviewed the pathological slides from the Norback and Weltman study, 
and concluded that some of the malignant liver tumors should have been 
interpreted as nonmalignant lesions, and that the cancer potency factor 
should be 5.1 per (mg/kg)/day as compared with EPA's 7.7 per (mg/kg)/
day.
    The Agency's recent peer-reviewed reassessment of the cancer 
potency of PCBs published in a final report, PCBs: Cancer Dose-Response 
Assessment and Applications to Environmental Mixtures (EPA/600/P-96/
001F), adopts a different approach that distinguishes among PCB 
mixtures by using information on environmental processes. (The report 
is included in the administrative record of today's proposed rule.) The 
report considers all cancer studies (which used commercial mixtures 
only) to develop a range of cancer potency factors, then uses 
information on environmental processes to provide guidance on choosing 
an appropriate potency factor for representative classes of 
environmental mixtures and different pathways. The reassessment 
provides that, depending on the specific application, either central 
estimates or upper bounds can be appropriate. Central estimates 
describe a typical individual's risk, while upper bounds provide 
assurance (i.e., 95% confidence) that this risk is not likely to be 
underestimated if the underlying model is correct. Central estimates 
are used for comparing or ranking environmental hazards, while upper 
bounds provide information about the precision of the comparison or 
ranking. In the reassessment, the use of the upper bound values were 
found to increase cancer potency estimates by two or

[[Page 42181]]

three-fold over those using central tendency. Upper bounds are useful 
for estimating risks or setting exposure-related standards to protect 
public health, and are used by EPA in quantitative cancer risk 
assessment. Thus, the cancer potency of PCB mixtures is determined 
using a tiered approach based on environmental exposure routes with 
upper-bound potency factors (using a body weight ratio to the 3/4 
power) ranging from 0.07 (lowest risk and persistence) to 2 (high risk 
and persistence) per (mg/kg)/day for average lifetime exposures to 
PCBs. It is noteworthy that bioaccumulated PCBs appear to be more toxic 
than commercial PCBs and appear to be more persistent in the body. For 
exposure through the food chain, risks can be higher than other 
exposures.
    EPA issued the final reassessment report on September 27, 1996 and 
updated IRIS to include the reassessment on October 1, 1996. For this 
proposed rule, EPA derived the human health criteria for PCBs using a 
cancer potency factor of 2 per (mg/kg)/day, an upper bound potency 
factor reflecting high risk and persistence. This decision is based on 
recent multimedia studies indicating that the major pathway of exposure 
to persistent toxic substances such as PCBs is via dietary exposure 
(i.e., contaminated fish and shellfish consumption).
    Following is the calculation of the human health criterion (HHC) 
for organism and water consumption:
[GRAPHIC] [TIFF OMITTED] TP05AU97.004

Where:

RF=Risk Factor=1  x  10 (-6)
BW=Body Weight=70 kg
q1*=Cancer slope factor=2 kg-day/mg
WC=Water Consumption=2 l/day
FC=Fish and Shellfish Consumption=0.0065 kg/day
BCF=Bioconcentration Factor=31,200

the HHC (<greek-m>g/l)=0.00017 <greek-m>g/l (rounded to two significant 
digits).

    Following is the calculation of the human health criterion for 
organism only consumption:
[GRAPHIC] [TIFF OMITTED] TP05AU97.005

Where:

RF=Risk Factor=1  x  10 (-6)
BW=Body Weight=70 kg
q1*=Cancer slope factor=2 kg-day/mg
FC=Total Fish and Shellfish Consumption per Day=0.0065 kg/day
BCF=Bioconcentration Factor=31,200

the HHC (<greek-m>g/l)=0.00017 <greek-m>g/l (rounded to two significant 
digits).

    The criteria are both equal to 0.00017 <greek-m>g/l and apply to 
the total PCBs or congener or isomer analyses (PCBs exposures should 
not be characterized in terms of aroclors). See PCBs: Cancer Dose 
Response Assessment and Application to Environmental Mixtures (EPA/600/
9-96-001F). For a discussion of the body weight, water consumption, and 
fish and shellfish consumption factors, see the Human Health 
Guidelines. For a discussion of the BCF, see the 304(a) criteria 
guidance document for PCBs (included in the administrative record for 
this proposed rulemaking).
 e. Section 304(a) Human Health Criteria Excluded
    As is the case in the NTR, as amended, today's proposed rule does 
not propose criteria for certain priority pollutants for which CWA 
section 304(a) criteria guidance exists because those criteria were not 
based on toxicity to humans or aquatic organisms. The basis for these 
particular criteria is organoleptic effects (e.g., taste and odor) 
which would make water and edible aquatic life unpalatable but not 
toxic. Because the basis for this rule is to protect the public health 
and aquatic life from toxicity consistent with the language and intent 
in CWA section 303(c)(2)(B), EPA is promulgating criteria only for 
those priority toxic pollutants whose criteria recommendations are 
based on toxicity. The CWA section 304(a) human health criteria based 
on organoleptic effects for zinc and 3-methyl-4-chlorophenol are 
excluded for this reason. See the 1992 NTR discussion at 57 FR 60864.
f. Cancer Risk Level
    EPA's CWA section 304(a) criteria guidance documents for priority 
toxic pollutants that are based on carcinogenicity present 
concentrations for upper bound risk levels of 1 excess cancer case per 
100,000 people (10<SUP>-5</SUP>), per 1,000,000 people 
(10<SUP>-6</SUP>), and per 10,000,000 people (10<SUP>-7</SUP>). 
However, the criteria documents do not recommend a particular risk 
level as EPA policy.
    In today's proposed rule, EPA is proposing criteria that protect at 
an incremental cancer risk level of one in a million (10<SUP>-6</SUP>) 
for all priority toxic pollutants regulated as carcinogens, consistent 
with those criteria promulgated in the NTR, as amended, for the State 
of California. The State had requested EPA to use a 10<SUP>-6</SUP> 
risk level for carcinogenic pollutants in the NTR. In addition, 
standards adopted by the State contained in the Enclosed Bays and 
Estuaries Plan (EBEP), and the Inland Surface Waters Plan (ISWP), 
partially approved by EPA on November 6, 1991, and the Ocean Plan 
approved by EPA on June 28, 1990, contain a risk level of 
10<SUP>-6</SUP> for most carcinogens. Thus, the State has historically 
protected at a 10<SUP>-6</SUP> risk level for carcinogenic pollutants. 
For today's proposed rule, the State has indicated a preference for EPA 
to propose criteria for carcinogenic pollutants at a 10<SUP>-6</SUP> 
risk level, but to also discuss and request comment on a 
10<SUP>-5</SUP> risk level. Therefore, EPA is explicitly requesting 
comment on the adoption of a 10<SUP>-5</SUP> risk level for 
carcinogenic pollutants proposed in this rule for the State of 
California. The effect of a 10<SUP>-5</SUP> risk level will be to 
increase carcinogenic pollutant criteria values (noted in today's 
proposed matrix by footnote c) which are not already promulgated in the 
NTR, as amended, by one order of magnitude. For example, the proposed 
organism-only criterion for gamma BHC (pollutant number 105 in the 
matrix) is 0.013 <greek-m>g/l; the criterion based on a 10<SUP>-5</SUP> 
risk level would be 0.13 <greek-m>g/l.
    The State, in its readoption of its statewide plans for inland 
surface waters and enclosed bays and estuaries may consider other risk 
levels for carcinogenic pollutants. EPA

[[Page 42182]]

recommends that states consider minimum risk levels in the range of 
10<SUP>-4</SUP> to 10<SUP>-6</SUP> for carcinogenic priority toxic 
pollutants to protect public health and welfare. See Human Health 
Guidelines.

F. Description of the Proposed Rule

1. Scope

    Subpart (a), entitled ``Scope'', states that this rule is a 
proposed promulgation of criteria for priority toxic pollutants in the 
State of California for inland surface waters, enclosed bays, and 
estuaries. Subpart (a) also states that this rule contains an 
authorizing compliance schedule provision.

2. EPA Criteria for Priority Toxic Pollutants

    EPA's proposed criteria for California are presented in tabular 
form that will appear at 40 CFR 131.38. For ease of presentation, the 
table that appears in this proposed rule combines water quality 
criteria promulgated in the NTR, as amended, that are outside the scope 
of this rulemaking, with the proposed criteria that are within the 
scope of today's proposed rule. This is intended to help readers 
determine applicable water quality criteria for the State of 
California. The table contains several footnotes for clarification; 
however, when EPA promulgates the final rule, the source of the 
criteria, either the NTR, as amended, or this rulemaking, may no longer 
be included as footnotes to the table.
    As proposed, subpart (b) presents a matrix of the applicable EPA 
aquatic life and/or human health criteria for priority toxic 
pollutants. Section 303(c)(2)(B) of the CWA addresses only pollutants 
listed as ``toxic'' pursuant to section 307(a) of the CWA for which EPA 
has developed section 304(a) criteria guidance. As discussed earlier in 
this preamble, the section 307(a) list of toxics contains 65 compounds 
and families of compounds, which potentially include thousands of 
specific compounds. Of these, the Agency identified a list of 126 
``priority toxic pollutants'' to implement the CWA (see 40 CFR 
131.36(b)). Reference in this proposed rule to priority toxic 
pollutants, toxic pollutants, or toxics refers to the 126 priority 
toxic pollutants.
    EPA has not developed both aquatic life and human health CWA 
section 304(a) criterion guidance for all of the priority toxic 
pollutants. The matrix in paragraph (b) contains human health criteria 
in Column D for 100 priority toxic pollutants which are divided into 
criteria (Column 1) for water consumption (i.e., 2.0 liters per day) 
and aquatic organism consumption (i.e., 6.5 grams per day of aquatic 
organisms), and into criteria (Column 2) for aquatic organism only 
consumption. The term aquatic organism includes fish and shellfish such 
as shrimp, clams, oysters and mussels. One reason the total number of 
priority toxic pollutants with criteria proposed today differs from the 
total number of priority toxic pollutants contained in earlier 
published CWA section 304(a) criteria guidance is because EPA has 
developed and is proposing chromium criteria for two valence states 
with respect to aquatic life criteria. Thus, although chromium is a 
single priority toxic pollutant, there are two criteria for chromium 
for aquatic life protection. See pollutant 5 in today's proposed 40 CFR 
131.38(b). Another reason is that EPA is proposing human health 
criteria for nine priority pollutants for which health-based national 
criteria have been calculated based on information obtained from EPA's 
IRIS database (EPA provided notice of these nine criteria in the NTR 
for inclusion in future State triennial reviews. See 57 FR 60848, 
60890).
    The matrix contains aquatic life criteria for 30 priority 
pollutants. These are divided into freshwater criteria (Column B) and 
saltwater criteria (Column C). These columns are further divided into 
acute and chronic criteria. The aquatic life criteria are considered by 
EPA to be protective when applied under the conditions described in the 
section 304(a) criteria documents and in the TSD. For example, water 
body uses should be protected if the criteria are not exceeded, on 
average, once every three year period. It should be noted that the 
criteria maximum concentrations (the acute criteria) are short-term 
concentrations and that the criteria continuous concentrations (the 
chronic criteria) are four-day averages. It should also be noted that 
for certain metals, the actual criteria are equations which are 
included as footnotes to the matrix. The toxicity of these metals is 
water hardness dependent and may be adjusted. The values shown in the 
table are illustrative only, based on a hardness expressed as calcium 
carbonate of 100 mg/l. Finally, the criterion for pentachlorophenol is 
pH dependent. The equation is the actual criterion and is included as a 
footnote. The value shown in the matrix is for a pH of 7.8.
    Several of the freshwater aquatic life criteria are incorporated 
into the matrix in the format used in the 1980 criteria methodology 
which uses a final acute value instead of a continuous maximum 
concentration. This distinction is noted in footnote g of the table.
    Proposed 40 CFR 131.38(c) would establish the applicability of the 
criteria to the State of California. Proposed 40 CFR 131.38(d) is 
described in Section F of this preamble.
    EPA's purpose today is to propose the numeric toxics criteria 
necessary for California to meet the requirements of the CWA. In order 
for such criteria to achieve their intended purpose, the implementation 
scheme must be such that the final results protect aquatic life and 
public health. In Section E of this preamble, a discussion focuses on 
the factors in EPA's assessment of criteria for carcinogens. For 
example, fish and shellfish consumption rates, bioaccumulation factors, 
and cancer potency slopes are discussed. When any one of these factors 
is changed, the others must also be evaluated so that, on balance, 
resulting criteria are adequately protective.
    Once an appropriate numeric criterion is selected for either 
aquatic life or human health protection, this facilitates the 
calculation of water quality-based effluent limits and/or total maximum 
daily loads (TMDLs) for that chemical. EPA has included in this rule 
appropriate implementation factors necessary to maintain the level of 
protection intended. These factors are included in subsection (c) of 
the proposed rule.
    For example, in order to do steady state waste load allocation 
analyses, most states have low flow values for streams and rivers which 
establish flow rates for various purposes. These low flow values become 
design flows for sizing treatment plants and developing water quality-
based effluent limits and/or TMDLs. Historically, these design flows 
were selected for the purposes of waste load allocation analyses which 
focused on instream dissolved oxygen concentrations and protection of 
aquatic life. With the publication of the 1985 TSD, EPA introduced 
hydrologically and biologically based analyses for the protection of 
aquatic life and human health. (These concepts have been expanded 
subsequently in EPA's Technical Guidance Manual for Performing 
Wasteload Allocations, Book 6, Design Conditions, U.S. EPA, 1986 . 
These new developments are included in Appendix D of the revised TSD. 
The discussion here is greatly simplified and is provided to support 
EPA's decision to promulgate design flows for instream flows and 
thereby maintain the intended stringency of the criteria for priority 
toxic pollutants.) EPA recommended either of two methods for 
calculating acceptable low flows, the

[[Page 42183]]

traditional hydrologic method developed by the U.S. Geological Survey 
and a biological based method developed by EPA. Other methods for 
evaluating the instream flow record may be available; use of these 
methods may result in TMDLs and/or water quality-based effluent 
limitations which adequately protect human health and/or aquatic life. 
The results of either of these two methods, or an equally protective 
alternative method, may be used.
    The State of California may adopt specific design flows for streams 
and rivers to protect designated uses against the effects of toxics. 
Generally, in other states, these have followed the guidance in the 
TSD. However, EPA believes it is essential to state that the criteria 
will apply at specified design flows for steady state analyses in 
today's rule so that, where California has not yet adopted any such 
design flows, the criteria proposed today would be implemented 
appropriately. The TSD also recommends the use of three dynamic models 
to perform wasteload allocations. Dynamic wasteload models do not 
generally use specific steady state design flows but accomplish the 
same effect by factoring in the probability of occurrence of stream 
flows based on the historical flow record. For simplicity, only steady 
state conditions will be discussed here. Clearly, if the criteria were 
implemented using design flows that are too high, the resulting toxics 
controls would not be fully effective, because the resulting ambient 
concentrations would exceed EPA's criteria.
    In the case of aquatic life, assuming exceedences occur more 
frequently than once in 3 years on the average, exceedences would 
result in diminished vitality of stream ecosystems characterized by the 
loss of desired species. Numeric water quality criteria should apply at 
all flows that are equal to or greater than flows specified below. The 
low flow values are:

Aquatic Life
    acute criteria (CMC)  1 Q 10 or 1 B 3
    chronic criteria (CCC)  7 Q 10 or 4 B 3

Human Health
    non-carcinogens  30 Q 5
    carcinogens  harmonic mean flow

Where:

1 Q 10 is the lowest one day flow with an average recurrence frequency 
of once in 10 years determined hydrologically;
1 B 3 is biologically based and indicates an allowable exceedence of 
once every 3 years. It is determined by EPA's computerized method 
(DFLOW model);
7 Q 10 is the lowest average 7 consecutive day low flow with an average 
recurrence frequency of once in 10 years determined hydrologically;
4 B 3 is biologically based and indicates an allowable exceedence for 4 
consecutive days once every 3 years. It is determined by EPA's 
computerized method (DFLOW model);
30 Q 5 is the lowest average 30 consecutive day low flow with an 
average recurrence frequency of once in 5 years determined 
hydrologically; and the harmonic mean flow is a long term mean flow 
value calculated by dividing the number of daily flows analyzed by the 
sum of the reciprocals of those daily flows.

    EPA is proposing that the harmonic mean flow be applied with human 
health criteria for carcinogens. The harmonic mean is a standard 
calculated statistical value. EPA's model for human health effects 
assumes that such effects occur because of a long-term exposure to low 
concentration of a toxic pollutant, for example, two liters of water 
per day for seventy years. To estimate the concentrations of the toxic 
pollutant in those two liters per day by withdrawal from streams with a 
high daily variation in flow, EPA believes the harmonic mean flow is 
the correct statistic to use in computing such design flows rather than 
other averaging techniques. (For a description of harmonic means see 
``Design Stream Flows Based on Harmonic Means,'' Lewis A. Rossman, Jr. 
of Hydraulics Engineering, Vol. 116, No. 7, July, 1990.) Hydrologic 
assessment methods other than the hydrologically-based and 
biologically-based methods may prove effective in applying water 
quality criteria in specific receiving water settings.
    All waters, whether or not suitable for such hydrologic 
calculations but included in this rule (including lakes, estuaries, and 
marine waters), would be required to attain the criteria proposed 
today. Such attainment would be required to occur at the end of the 
discharge pipe, unless the State authorizes mixing zones. EPA has 
approved mixing zone provisions in Regional Water Quality Control Board 
Basin Plans. Where the State intends to authorize a mixing zone, the 
criteria would apply at the locations allowed by the mixing zone. For 
example, the chronic criteria (CCC) would apply at the defined boundary 
of the chronic mixing zone. Discussion of and guidance on these factors 
are included in the revised TSD in Chapter 4.
    EPA is aware that the criteria proposed today for some of the 
priority toxic pollutants are at concentrations less than EPA's current 
analytical detection limits. Analytical detection limits have never 
been an acceptable basis for setting water quality criteria since they 
are not related to actual environmental impacts. The environmental 
impact of a pollutant is based on a scientific determination, not a 
measuring technique which is subject to change. Setting the criteria at 
levels that reflect adequate protection tends to be a forcing mechanism 
to improve analytical detection methods. See 1985 Guidelines, page 21. 
As the methods improve, limits closer to the actual criteria necessary 
to protect aquatic life and human health became measurable. The Agency 
does not believe it is appropriate to propose or promulgate criteria 
that are not sufficiently protective.
    EPA does believe, however, that the use of analytical detection 
limits are appropriate for determining compliance with National 
Pollutant Discharge Elimination System (NPDES) permit limits. This view 
of the role of detection limits was articulated in guidance for 
translating dioxin criteria into NPDES permit limits, which is the 
principal method used for water quality standards enforcement. See 
``Strategy for the Regulation of Discharges of PHDDs and PHDFs from 
Pulp and Paper Mills to Waters of the U.S.'' Memorandum from the 
Assistant Administrator for Water to the Regional Water Management 
Division Directors, May 21, 1990. This guidance presents a model for 
addressing toxic pollutants which have criteria less than current 
detection limits. This guidance is equally applicable to other priority 
toxic pollutants with criteria less than current detection limits. The 
guidance explains that standard analytical methods may be used for 
purposes of determining compliance with permit limits, but not for 
purposes of establishing water quality criteria or permit limits. Under 
the CWA, analytical methods are appropriately used in connection with 
NPDES permit limit compliance determinations. Because of the function 
of water quality criteria, EPA has not considered the sensitivity of 
analytical methods in deriving the criteria proposed today.
    EPA has proposed 40 CFR 131.38(c)(3) to determine when freshwater 
or saltwater aquatic life criteria apply. This provision incorporates a 
time parameter to better

[[Page 42184]]

define the critical condition. The structure of the paragraph is to 
establish applicable rules and to allow for site-specific exceptions 
where the rules are not consistent with actual field conditions. 
Because a distinct separation generally does not exist between 
freshwater and saltwater aquatic communities, EPA is establishing the 
following: (1) The freshwater criteria apply at salinities of 1 part 
per thousand and below at locations where this occurs 95% or more of 
the time; (2) saltwater criteria apply at salinities of 10 parts per 
thousand and above at locations where this occurs 95% more of the time; 
and (3) at salinities between 1 and 10 parts per thousand the more 
stringent of the two apply unless EPA approves the application of the 
freshwater or saltwater criteria based on an appropriate biological 
assessment. The percentiles included here were selected to minimize the 
chance of overlap, that is, one site meeting both criteria. 
Determination of these percentiles can be done by any reasonable means 
such as interpolation between points with measured data or by the 
application of calibrated and verified mathematical models (or 
hydraulic models). It is not EPA's intent to require actual data 
collection at particular locations.
    In the brackish water transition zones of estuaries with varying 
salinities, there generally will be a mix of freshwater and saltwater 
species. Generally, therefore, it is reasonable for the more stringent 
of the freshwater or saltwater criteria to apply. In evaluating 
appropriate data supporting the alternative set of criteria, EPA will 
focus on the species composition as its preferred method. This 
assignment of criteria for fresh, brackish and salt waters was 
developed in consultation with EPA's research laboratories at Duluth, 
Minnesota and Narragansett, Rhode Island. The Agency believes such an 
approach is consistent with field experience.
    Subsection (d) lists the designated water and use classifications 
for which the proposed criteria apply. The criteria are applied to the 
beneficial use designations adopted by the State of California; EPA has 
not promulgated any new use classifications in this rule.
    Exceedence Frequency: In a water quality criterion for aquatic 
life, EPA recommends an allowable frequency for excursions of the 
criteria. See 1985 Guidelines, pages 11-13. This allowable frequency 
provides an appropriate period of time during which the aquatic 
community can recover from the effect of an excursion and then function 
normally for a period of time before the next excursion. An excursion 
is defined as an occurrence of when the average concentration over the 
duration of the averaging period is above the CCC or the CMC. As 
ecological communities are naturally subjected to a series of stresses, 
the allowable frequency of pollutant stress may be set at a value that 
does not significantly increase the frequency or severity of all 
stresses combined. See also TSD, Appendix D. In addition, providing an 
allowable frequency for exceeding the criterion recognizes that it is 
not generally possible to assure that criteria are never exceeded. 
(TSD, page 36.)
    Based on the available data, EPA is proposing that the acute 
criterion for a pollutant be exceeded no more than once in three years 
on the average. EPA is also proposing that the chronic criterion for a 
pollutant be exceeded no more than once in three years on the average. 
EPA acknowledges that the State may develop allowable frequencies that 
differ from these allowable frequencies, so long as they are 
scientifically supportable, but believes that these allowable 
frequencies are protective of the designated uses.
    The use of aquatic life criteria for developing water quality-based 
effluent limits in permits requires the permitting official to use an 
appropriate wasteload allocation model. (TSD, Appendix D-6.) As 
discussed above, there are generally two methods for determining design 
flows, the hydrologically-based method and the biologically-based 
method.
    The biologically-based method directly uses the averaging periods 
and frequencies specified in the aquatic life criteria for determining 
design flows. (TSD, Appendix. D-8.) Because the biologically-based 
method calculates the design flow directly from the duration and 
allowable frequency, it most accurately provides the allowed number of 
excursions. The hydrologically based method applies the CMC at a design 
flow equal to or equivalent to the 1Q10 design flow (i.e., the lowest 
one-day flow with a recurrence frequency of one year in ten years), and 
applies the CCC at the 7Q10 design flow (i.e., the lowest seven day 
flow with a recurrence frequency of one year in ten years).
    EPA established a three year allowable frequency in the NTR. In 
settlement of the litigation on the NTR, EPA stated that it was in the 
midst of conducting, sponsoring, or planning research aimed at 
addressing scientific issues related to the basis for and application 
of water quality criteria and mentioned the issue of allowable 
frequency. 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. To that end, EPA is reevaluating issues raised about 
allowable frequency as part of its work in revising the 1985 
Guidelines.
    In addition, EPA received public comment on the allowable frequency 
incorporated into the amendments to the NTR. These comments argued that 
a once every three years on the average excursion frequency for 4-day 
average concentrations, or a 7Q10 design flow for chronic criteria, was 
unnecessarily restrictive. For chronic criteria, commenters noted that 
EPA has approved use of a 30Q3 design 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.
    EPA recognizes that additional data concerning (a) the probable 
frequency of lethal events for an assemblage of taxa covering a range 
of sensitivities to pollutants, (b) the probable frequency of sublethal 
effects for such taxa, (c) the differing effects of lethal and 
sublethal events in reducing populations of such taxa, and (d) the time 
needed to replace organisms lost as a result of toxicity, may lead to 
further refinement of the allowable frequency value. Due to lack of 
available resources, EPA has not yet completed this work. Until this 
work is complete, EPA believes that the three year allowable frequency 
represents a value in the reasonable range for this parameter.

3. Implementation

    Once the applicable designated uses and water quality criteria for 
a water body are determined, under the National Pollutant Discharge 
Elimination System (NPDES) program, discharges to the water body must 
be characterized and the permitting authority must determine the need 
for permit limits. If a discharge causes, has the reasonable potential 
to cause, or contributes to an excursion of a numeric or narrative 
water quality criteria, the permitting authority must develop permit 
limits as necessary to meet water quality standards. These permit 
limits are water quality-based effluent limitations or WQBELs. The 
terms ``cause,'' ``reasonable potential to cause,'' and ``contribute 
to'' are the terms in the NPDES regulations for conditions under which 
water quality-based permit limits are required. See 40 CFR 
122.44(d)(1).
    Total Maximum Daily Loads (TMDLs): If a water quality problem is 
identified, a wasteload allocation (WLA) based on an existing total 
maximum daily load

[[Page 42185]]

(TMDL) may be established. A TMDL is the sum of the individual WLAs for 
point sources and load allocations (LA) for nonpoint sources of 
pollution and natural background sources, tributaries, or adjacent 
segments. WLAs represent that portion of a TMDL that is allocated to 
existing and future point sources so that surface water quality is 
protected at all flow conditions.
    The TMDL process uses water quality analyses to predict water 
quality conditions and pollutant concentrations. Point source and 
nonpoint source allocations are established so that predicted receiving 
water concentrations do not exceed water quality standards. TMDLs and 
WLAs/LAs should be established at levels necessary to attain and 
maintain the applicable narrative and numerical water quality 
standards, with seasonal variations and a margin of safety that takes 
into account any lack of knowledge concerning the relationship between 
point and nonpoint source loadings and water quality.
    The CWA under section 303(d), requires the establishment of TMDLs 
for stream segments listed as ``water quality limited'' pursuant to 
section 303(d). In such segments, water quality does not meet 
applicable water quality standards and/or is not expected to meet 
applicable water quality standards. A TMDL includes a determination of 
the amount of a pollutant, or property of a pollutant, from point, 
nonpoint, and natural background sources, including a margin of safety, 
that may be discharged to a water-quality limited water body.
    During California's recent set of Task Force meetings concerning 
the readoption of statewide water quality control plans, the Permitting 
Task Force made several recommendations concerning the TMDL process. 
Since the TMDL process can be significantly labor and data intensive, a 
recommendation was made to create collaborative efforts to establish 
TMDLs on water quality limited water bodies. This collaborative effort 
by dischargers, the State, EPA, and other stakeholders, could 
distribute work and associated costs between the interested parties, as 
well as shorten the overall time necessary to complete the analyses. 
Another recommendation was to allow innovative alternatives to 
traditional ``pounds per day'' TMDLs. EPA supports these Task Force 
recommendations for the State of California.
    Within the TMDL framework, EPA encourages innovative approaches 
such as effluent trading as a method to attain and/or maintain water 
quality standards. Effluent trading allows sources that can control 
pollutants beyond compliance with current requirements to sell or trade 
credits for its excess reduction to another source unable to control 
its own pollutants as effectively or as efficiently. The goal of an 
effluent trading program is to achieve similar or improved 
environmental results in a more cost-effective manner than under 
current regulatory structures. EPA's most current policy on effluent 
trading is summarized in the ``Policy Statement for Effluent Trading in 
Watersheds'' which was issued in January of 1996 and which reiterates 
President Clinton's commitment to effluent trading as expressed in the 
March 16, 1995 report on ``Reinventing Environmental Regulation.'' The 
Policy states that ``EPA will work cooperatively with key stakeholders 
to find sensible, innovative ways to meet water quality standards 
quicker and at less cost than traditional approaches alone.'' The 
policy outlines several different types of trades that may take place. 
These trades include but are not limited to the following: (1) Intra-
plant trading between outfalls within one facility; (2) pretreatment 
trading between indirect industrial point sources that discharge to a 
POTW; (3) point to point source trading, point to nonpoint source 
trading, and nonpoint to nonpoint source trading.
    Interim Permit Limits: The State's Permitting Task Force also 
discussed at length the issue of interim numeric permit limits when a 
TMDL/WLA/LA or other special study is underway but not completed. The 
Task Force made several recommendations regarding how to determine 
these interim limits. The Task Force recommended that interim numeric 
limits be calculated based on past performance and future uncertainty. 
Past performance and future uncertainty can be considered as factors in 
determining interim permit limits; however, permitting authorities may 
consider other factors, particularly factors concerning the water 
quality of the receiving water body and the overall goal to attain the 
water quality standard. The Task Force also recommended that a specific 
method be followed in determining interim limits and ``trigger'' 
concentrations above which corrective action would be necessary. EPA 
supports innovative ideas such as these, however, the State as the 
permitting authority has broad discretion in determining how interim 
permit limits should be ascertained in different situations. EPA 
supports the State's consideration of stakeholder Task Force 
recommendations to help deal with these controversial and complex 
issues.
    Mixing Zones: Another important issue discussed during the State's 
Task Force meetings was the issue of mixing zones. A mixing zone is a 
limited area or volume of water where initial dilution of a discharge 
takes place and where water quality standards can be exceeded. Mixing 
zones have been applied in the water quality standards program since 
its inception. The present water quality standards regulation allows 
states to adopt acute and chronic mixing zones as a matter of state 
discretion, so long as the state's mixing zone protects the designated 
uses.
    A mixing zone should be established to ensure that the zone will 
not impair the integrity of the water body as a whole, the zone will 
not cause lethality to passing organisms, and, considering likely 
pathways of exposure, that there are no significant human health risks. 
For application of two-number aquatic life criteria, as proposed in 
this rule, there may be up to two types of mixing zones. In the zone 
immediately surrounding the outfall, neither the acute nor the chronic 
criterion is met. The acute criterion is met at the edge of this zone. 
In the next mixing zone, the acute, but not the chronic, criterion is 
met. The chronic criterion is met at the edge of the second mixing 
zone. However, since both aquatic life and human health criteria are 
proposed in today's rule, the State may establish independent mixing 
zone policies for each. For any particular pollutant from any 
particular discharge, the magnitude, frequency, duration and mixing 
zone associated with each of the type of criteria may determine which 
one most limits the allowable discharge.
    Several California Regional Water Quality Control Boards have 
adopted mixing zone provisions in their respective Basin Plans. These 
mixing zone provisions can be applied to discharges to water bodies to 
which water quality standards based on the criteria contained in this 
proposed rule will apply when these criteria are promulgated final.
    Variances: Another important procedure to assist the State in 
effectively implementing water quality standards in the NPDES program 
is the water quality standard variance procedure. The State may adopt a 
statewide policy (or Regional Boards may adopt Basin-wide policies) to 
allow for water quality standard variances to individual dischargers. 
The variance policy would allow the State or Regional Board to grant a 
variance to an individual permittee from a water quality standard which 
is the basis of a water quality-based effluent limitation in a permit. 
The variance would allow the permittee time to achieve reasonable 
progress towards attaining a specific

[[Page 42186]]

water quality-based effluent limitation, without violating CWA section 
402(a)(1) which requires that NPDES permittees meet all applicable 
water quality standards.
    A permittee applying for a variance may not be a new or 
recommencing discharger. The water quality standard variance applies 
only to the permittee requesting the variance and only to the pollutant 
or pollutants specified in the variance. A variance does not effect the 
corresponding water quality standard for the water body receiving the 
discharge. Variances are designed to preserve the underlying water 
quality standard over the long term, while providing flexibility to 
individual dischargers in complying with permit limits based on the 
standards. When a variance is granted, the discharger is assured 
compliance during the term of a variance, as long as all variance 
conditions are met.
    A State-adopted variance policy will be approved by the EPA if it 
is consistent with the substantive requirements set out at 40 CFR Part 
131 for removing a designated use. Specifically, the State's policy 
must require the inclusion of a demonstration that a water quality 
standard is unattainable, based on one or more of the following 
grounds:
    1. Naturally occurring pollutant concentrations prevent the 
attainment of the water quality standard;
    2. Natural, ephemeral, intermittent or low flow conditions or water 
levels prevent the attainment of the water quality standard, unless 
these conditions may be compensated for by the discharge of sufficient 
volume of effluent to enable the standard to be met without violating 
State water conservation requirements;
    3. Human-caused conditions or sources of pollution prevent the 
attainment of the water quality standard and cannot be remedied, or 
would cause more environmental damage to correct than to leave in 
place;
    4. Dams, diversions or other types of hydrologic modifications 
preclude the attainment of a water quality standard, and it is not 
feasible to restore the water body to its original condition or to 
operate such modification in a way that would result in the attainment 
of the standard;
    5. Physical conditions related to the natural features of the water 
body, such as the lack of a proper substrate cover, flow, depth, pools, 
riffles, and the like, unrelated to chemical water quality, preclude 
attainment of the water quality standard; or
    6. Controls more stringent than those required by CWA sections 
301(b) and 306 would result in substantial and widespread economic and 
social impact.
    EPA will approve a State policy providing for variances if the 
policy includes the following provisions:
    1. The State will include each individual variance as part of its 
water quality standard or water quality plan;
    2. The variance will include documentation that treatment more 
advanced than that required by CWA section 301(b) and 306 has been 
carefully considered, and that alternative effluent control strategies 
have been evaluated;
    3. The underlying, more stringent criterion will be maintained and 
will be binding on all other dischargers;
    4. The discharger who will be given a variance for one particular 
constituent will be required to meet the applicable criteria for other 
constituents;
    5. The variance will be granted for a specific period of time and 
must be rejustified upon expiration, but at least every three years;
    6. Reasonable progress will be made towards meeting the underlying 
standards;
    7. The variance will not likely jeopardize the continued existence 
of any threatened or endangered species listed under Section 4 of the 
Endangered Species Act or result in the destruction or adverse 
modification of such species' critical habitat; and
    8. The variance will be subjected to public notice, comment, and 
hearing. See CWA section 303(c)(1) and 40 CFR 131.20. The public notice 
should contain a clear description of the impact of the variance upon 
achieving the water quality standard in the water body.
    Once a variance has been approved by the State, it must be 
submitted to EPA for approval. If this proposed rule is still in 
effect, as with the State adoption of site-specific criteria, EPA would 
have to undertake rulemaking to make the necessary changes to this 
rule. Further guidance on variance policies is provided in EPA's 1994 
Water Quality Standards Handbook, Chapters 2 and 5 (EPA 823-B-94-005a, 
August 1994).
    EPA, however, cautions California and the public that promulgation 
of this federal rule removes most of the flexibility available to the 
State for modifying its standards on a discharger-specific or stream-
specific basis. For example, variances and site-specific criteria 
development are actions sometimes adopted by states. These are optional 
policies under terms of the federal water quality standards regulation. 
Except for the water-effect ratio procedure for certain metals, EPA has 
not incorporated either optional policy, in general, in this proposed 
rulemaking, that is, EPA has not generally authorized State 
modifications of federal water quality standards. Each of these types 
of modifications will, in general, require federal rulemaking on a 
case-by-case basis to change the federal rule. Because of the time 
consuming nature of reviewing such requests, limited federal resources, 
and the need for the Agency to move into other priority program areas 
in establishing environmental controls, EPA alerts California and the 
public that a prompt Agency response is unlikely. The best course of 
action, if such provisions are desired, is for the State to adopt its 
own standards and take advantage, if it so chooses, of the flexibility 
offered by these optional provisions.

4. Wet Weather Flows

    Questions have already arisen concerning the applicability of these 
proposed criteria to discharges from wet weather point sources. A wet 
weather point source means any discernible confined and discrete 
conveyance from which pollutants are, or may be, discharged as the 
result of a wet weather event. For purposes of this discussion, 
discharges from wet weather point sources shall include only: 
discharges of storm water from a municipal separate storm sewer as 
defined at 40 CFR 122.26(b)(8); storm water discharge associated with 
industrial activity as defined at 40 CFR 122.26(b)(14); discharges of 
storm water and sanitary wastewaters (domestic, commercial, and 
industrial) from a combined sewer overflow; or any storm water 
discharge for which a permit is required under section 402(p) of the 
CWA. A storm water discharge associated with industrial activity which 
is mixed with process wastewater is not considered a wet weather point 
source.
    National Pollutant Discharge Elimination System (NPDES) permits for 
wet weather point source discharges must include limits necessary to 
implement applicable water quality standards, through application of 
water quality-based effluent limitations or WQBELs. Section 
301(b)(1)(C) of the CWA, 33 U.S.C. 1311(b)(1)(C); see also Memorandum 
of E. Donald Elliot, Assistant Administrator and General Counsel, to 
Nancy J. Marvel, Region 9, dated January 9, 1991. When this rulemaking 
is complete, these criteria will be used to determine water quality 
standards in California and will therefore be the basis of WQBELs in 
NPDES permits for wet weather point sources. However, EPA recognizes 
that it is commonly infeasible to express

[[Page 42187]]

WQBELs as numeric limits for wet weather discharges and that in such 
cases best management practices (``BMPs'') may serve as WQBELs. See, 
e.g., NRDC v. Costle, 568 F. 2d 1369, 1380 (D.C. Cir. 1977) (``when 
numeric effluent limitations are infeasible, EPA may issue permits with 
conditions designed to reduce the level of effluent discharges to 
acceptable levels.''); NRDC v. U.S. EPA, 822 F. 2d 104, 122 (D.C. Cir. 
1987) (``* * * Congress has seen fit to empower EPA to prescribe as 
wide a range of permit conditions as the agency deems appropriate in 
order to assure compliance with applicable effluent limits.''). It is 
therefore anticipated that WQBELs, including those necessary to meet 
the criteria set forth in this proposed rule, will be expressed as BMPs 
in wet weather discharges' NPDES permits, when the permitting authority 
determines that it is infeasible to express WQBELS as numeric limits.

5. Schedules of Compliance

    A compliance schedule refers to an enforceable sequence of interim 
requirements in a permit leading to ultimate compliance with water 
quality-based effluent limitations or WQBELs in accordance with the 
CWA. The proposed authorizing compliance schedule provision authorizes, 
but does not require, the permit issuing authority in the State of 
California to include such compliance schedules in permits under 
appropriate circumstances. The State of California is authorized to 
administer the National Pollutant Discharge Elimination System (NPDES) 
program and may exercise its discretion when deciding if a compliance 
schedule is justified because of the technical or financial (or other) 
infeasibility of immediate compliance.
    This authorizing compliance schedule provision is included in the 
proposed rule because of the potential for existing dischargers to have 
new or more stringent effluent limitations, under the final rule, for 
which immediate compliance would not be possible or practicable.
    New and Existing Dischargers: The proposed provision allows 
compliance schedules only for an ``existing discharger'' which is 
defined as any discharger which is not a ``new California discharger.'' 
A ``new California discharger'' includes ``any building, structure, 
facility, or installation from which there is, or may be, a `discharge 
of pollutants', the construction of which commenced after the effective 
date of this regulation.'' These definitions are modelled after the 
existing 40 CFR 122.2 definitions for parallel terms, but with a cut-
off date modified to reflect this rule. Only ``new California 
dischargers'' are required to comply immediately upon commencement of 
discharge with effluent limitations derived from the criteria in this 
rule.
    For ``existing dischargers'' whose permits were reissued or 
modified to contain new or more stringent limitations based upon 
certain water quality requirements, the permit could allow up to five 
years to comply with such limitations. The provision applies to new or 
more stringent effluent limitations based on the criteria in this EPA 
rule.
    EPA has included ``increasing dischargers'' within the category of 
``existing dischargers'' since ``increasing dischargers'' are existing 
facilities with a change--an increase--in their discharge. Such 
facilities may include those with seasonal variations. ``Increasing 
dischargers'' will already have treatment systems in place for their 
current discharge, thus, they have less opportunity than a new 
discharger does to design and build a new treatment system which will 
meet new water quality-based requirements for their changed discharge. 
Allowing existing facilities with an increasing discharge a compliance 
schedule will avoid placing the discharger at a competitive 
disadvantage vis-a-vis other existing dischargers who are eligible for 
compliance schedules.
    The proposed rule does not prohibit the use of a short-term ``shake 
down period'' for new California dischargers as is provided for new 
sources or new dischargers in 40 CFR 122.29(d)(4). These regulations 
require that the owner or operator of (1) a new source; (2) a new 
discharger (as defined in 40 CFR 122.2) which commenced discharge after 
August 13, 1979; or (3) a recommencing discharger shall install and 
implement all pollution control equipment to meet the conditions of the 
permit before discharging. The facility must also meet all permit 
conditions in the shortest feasible time (not to exceed 90 days). This 
shake-down period is not a compliance schedule. This approach may be 
used to address violations which may occur during a new facility's 
start-up, especially where permit limits are water quality-based and 
biological treatment is involved.
    The burden of proof to show the necessity of a compliance schedule 
is on the discharger, and the discharger must request approval from the 
permit issuing authority for a schedule of compliance. The discharger 
should submit a description of the minimum required actions or 
evaluations that must be undertaken in order to comply with the new or 
more restrictive discharge limits. Dates of completion for the required 
actions or evaluations should be included, and the proposed schedule 
should reflect the shortest practicable time to complete all minimum 
required actions.
    Duration of Compliance Schedules: EPA believes that compliance 
schedules of three years or less will be sufficient to allow facilities 
to make the changes necessary to meet new or more restrictive discharge 
requirements in most cases. Such compliance periods are consistent with 
analogous provisions of the CWA including sections 301(b)(2) and 
304(l). For example, section 301(b)(2)(C)--(F) of the Act provides that 
various technology-based effluent limitations shall be complied with as 
expeditiously as possible but no later than three years after effluent 
limitations are promulgated. Similarly, section 304(l) provides that 
sources shall comply with individual control strategies (water-quality 
based requirements) within three years.
    However, the Agency also recognizes the concerns of dischargers 
regarding the amount of time and resources in some cases that may be 
needed for implementing certain new or complex state-of-the-art 
treatment technologies and other pollution prevention programs. The 
Agency recognizes that evaluation, design and implementation of 
facility-wide comprehensive pollution prevention control strategies 
involving product substitution, process line changes, new piping, 
revised waste handling, etc. may require more than three years at large 
facilities. In addition, EPA is aware that the technical and 
administrative process of modifying and implementing revised 
requirements for numerous industrial users at publicly owned treatment 
works, as well as planning, budgeting, and undertaking significant new 
construction to change treatment processes at a municipal treatment 
works, may require more than three years.
    Therefore, the proposed rule provides that compliance schedules may 
provide for up to five years to meet new or more stringent effluent 
limitations in those limited circumstances where the permittee can 
demonstrate to the permit authority that such an extended schedule is 
warranted. EPA emphasizes its belief that in most situations less than 
three years will be required; EPA believes that permit authorities 
should consider shorter compliance schedules wherever possible or 
alternatively, not allow compliance schedules where unnecessary. This 
provision should not

[[Page 42188]]

be considered a default compliance schedule duration for existing 
facilities.
    In instances where dischargers wish to conduct toxicological 
studies, analyze results, and adopt and implement new or revised water 
quality-based effluent limitations, EPA believes that five years is 
sufficient time within which to complete this process.
    Under this proposal, where a schedule of compliance exceeds one 
year, interim requirements are to be specified and interim progress 
reports are to be submitted at least annually to the permit issuing 
authority, in at least one-year time intervals.
    The proposed rule allows all compliance schedules to extend up to a 
maximum duration of five years, which is the maximum term of any NPDES 
permit. See 40 CFR 122.46. The discharger's opportunity to obtain a 
compliance schedule occurs when the existing permit for that discharge 
is issued, reissued or modified, whichever is sooner. Such compliance 
schedules, however, cannot be extended to any indefinite point of time 
in the future because no final compliance date for WQBELs based upon 
this rule shall be more than ten years from the effective date of the 
rule. Thus, delays in reissuing expired permits (including those which 
continue in effect under applicable NPDES regulations) cannot 
indefinitely extend the period of time during which a compliance 
schedule is in effect. Ten years allows for inclusion of the single 
maximum five-year compliance schedule in a permit which is reissued 
five years after the effective date of this rule (having been 
previously issued without WQBELS using today's proposed criteria on the 
eve of the effective date of this rule).
    EPA recognizes that where a permit is modified during the permit 
term, and the permittee needs the full five years to comply, the five-
year schedule may extend beyond the term of the modified permit. In 
such cases, the rule allows for the modified permit to contain a 
compliance schedule with an interim limit by the end of the permit 
term. When the permit is reissued, the permit authority may extend the 
compliance schedule in the next permit, provided that, taking into 
account the amount of time allowed under the previous permit, the 
entire compliance schedule shall not exceed five years. Final permit 
limits and compliance dates will be included in the record for the 
permit. Final compliance dates must occur within five years from the 
date of permit issuance, reissuance, or modification, unless additional 
or less time is provided for by law.
    Antibacksliding: EPA wishes to address the potential concern over 
antibacksliding where revised permit limits based on new information 
are the result of the completion of additional studies. The Agency's 
interpretation of the CWA is that the antibacksliding requirements of 
section 402(o) of the CWA do not apply to revisions to effluent 
limitations made before the scheduled date of compliance for those 
limitations.
    State Compliance Schedule Provisions: EPA supports the State in 
adopting a statewide provision independent of or as part of the current 
effort to readopt statewide water quality control plans, or in adopting 
individual basin-wide compliance schedule provisions through its nine 
Regional Water Quality Control Boards (RWQCBs). The State and RWQCBs 
have broad discretion to adopt a provision, including discretion on 
reasonable lengths of time for final compliance with WQBELs. EPA 
recognizes that practical time frames within which to set interim goals 
may be necessary to achieve meaningful, long-term improvements in water 
quality in California.
    At this time, at least one RWQCB has adopted an authorizing 
compliance schedule provision as an amendment to its Basin Plan during 
its last triennial review process. If EPA includes an authorizing 
compliance schedule provision in the final rule, any appropriately 
adopted Basin Plan amendment concerning a compliance schedule provision 
would also be effective for the Basin.

G. Executive Order (E.O.) 12866, Regulatory Planning and Review

    Under Executive Order 12866, [58 FR 51,735 (October 4, 1993)] the 
Agency must determine whether the regulatory action is ``significant'' 
and therefore subject to Office of Management and Budget (OMB) review 
and the requirements of the Executive Order. The Order defines 
``significant regulatory action'' as one that is likely to result in a 
rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    It has been determined that this rule is not a ``significant 
regulatory action'' under the terms of Executive Order (E.O.) 12866 and 
is therefore not subject to OMB review. The proposed rule establishes 
ambient water quality criteria which, by themselves, do not directly 
impose economic impacts. When these criteria are combined with the 
State-adopted designated uses for inland surface waters, enclosed bays 
and estuaries, water quality standards will be created. EPA 
acknowledges that there may be a cost to some dischargers for complying 
with new water quality standards after those standards are translated 
into specific National Pollutant Discharge Elimination System (NPDES) 
permit limits by the State. Consistent with the intent of E.O. 12866, 
EPA prepared an Economic Analysis (EA). Since the State has significant 
flexibility and discretion in how it chooses to implement standards 
within the NPDES permit program, the EA by necessity includes many 
assumptions about how the State will implement the water quality 
standards. These assumptions are based on a combination of EPA guidance 
and current permit conditions for the facilities examined in this 
analysis. (This is appropriate because if the State does not adopt 
statewide implementation provisions, the rule-based water quality 
standards would be implemented using existing State basin plan 
provisions, and EPA regulations and guidance.) A more precise measure 
of costs and benefits may not be known until the State adopts its 
implementation provisions. To account for the uncertainty of these 
assumptions, this analysis estimates a wide range of costs and 
benefits. By completing the EA, EPA intends to inform the public about 
how entities might be affected by implementation of rule-based water 
quality standards in the NPDES permit program.

1. Baselines

    In order to estimate the costs and benefits, an appropriate 
baseline must be established. The baseline is the starting point for 
measuring incremental costs and benefits of a proposed regulation. The 
baseline is established by assessing what would occur in the absence of 
the proposed regulation. EPA estimated the incremental costs and 
benefits of potential State implementation of water quality standards 
based on the criteria

[[Page 42189]]

contained in today's proposed rule using two different models which 
used different baselines.
    The first model used a baseline that results in no incremental 
impacts. This baseline assumes that, in the absence of this rule, the 
State would, pursuant to the NPDES regulations, 40 CFR 122.44(d)(iv), 
rely on the Regional Board narrative standards to establish numeric 
water quality-based effluent limits in permits. These limits could be 
based on the latest EPA 304(a) criteria--the same information upon 
which today's proposed criteria are based, or supplemented where 
necessary by other relevant information. Under this scenario, no 
impacts would be attributed permit limits based on implementation of 
water quality standards using the criteria contained in today's 
proposed rule, since the analysis presumes that the State, in the 
absence of this rule, would implement effluent limits that are as 
stringent as those that would be implemented using water quality 
standards based on today's proposed criteria.
    The baseline used in the second model assumes that in the absence 
of the rule, current permit requirements and current effluent 
concentrations would continue into the future. This model generally 
uses a baseline of current permit limits to develop a high scenario 
cost estimate and a baseline of current effluent concentrations to 
develop a low scenario cost estimate. Using this second model, EPA 
estimated a range of potential costs that would result from State 
implementation of this rule's water quality criteria in NPDES permits. 
The costs and benefits sections that follow summarize the methodology 
and results of the analysis using this baseline.

2. Costs

    Under the second model, EPA assessed the estimated compliance costs 
that facilities may incur to meet permit limits based on the criteria 
in today's proposed rule. The analysis focused on direct compliance 
costs such as capital costs and operation and maintenance costs (O&M) 
for end-of-pipe pollution control, indirect source controls, pollution 
prevention, monitoring, and costs of pursuing alternative methods of 
compliance.
    The population of facilities with NPDES permits that discharge into 
California's enclosed bays, estuaries and inland surface waters 
includes 184 major dischargers and 1,057 minor dischargers. Of the 184 
major facilities, 128 are publicly owned treatment works (POTWs) and 56 
are industrial facilities. Approximately 2,144 indirect dischargers 
designated as significant industrial users discharge wastewater to 
those POTWs. For the direct dischargers, EPA used a three-phased 
process to select a sample of facilities to represent California 
dischargers potentially affected by the State's implementation of 
permit limits based on the criteria contained in this rule.
    The first phase consisted of choosing three case study areas for 
which data was thought to exist. The three case studies with a total of 
5 facilities included: the South San Francisco Bay (the San Jose/Santa 
Clara Water Pollution Control Plant and Sunnyvale Water Pollution 
Control Plant); the Sacramento River (the Sacramento Regional 
Wastewater Treatment Plant); and the Santa Ana River (the City of 
Riverside Water Quality Control Plant and the City of Colton Municipal 
Wastewater Treatment Facility). The second phase consisted of selecting 
five additional major industrial dischargers to complement the case-
study POTWs.
    The third and last selection phase involved selecting 10 additional 
facilities to improve the basis for extrapolating the costs of the 
selected sample facilities to the entire population of potentially 
affected dischargers. The additional 10 facilities were selected such 
that the group examined: (1) Was divided between major POTWs and major 
industrial discharger categories in proportion to the numbers of 
facilities in the State; (2) gave greater proportionate representation 
to major facilities than minor facilities based on a presumption that 
the majority of compliance costs would be incurred by major facilities; 
(3) gave a proportionate representation to each of four principal 
conventional treatment processes typically used by facilities in 
specified industries in California; and (4) was representative of the 
proportionate facilities located within the different California 
Regional Water Quality Control Boards. Within these constraints, 
facilities were selected at random to complete the sample.
    For those facilities that were projected to exceed permit limits 
based on the proposed criteria, EPA estimated the incremental costs of 
compliance. Using a decision matrix or flow chart, costs were developed 
for two different scenarios--a ``low-end'' cost scenario and a ``high-
end'' cost scenario--to account for a range of regulatory flexibility 
available to the State when implementing permit limits based on the 
proposed water quality criteria. The assumptions for baseline loadings 
also vary over the two scenarios. The low-end scenario generally 
assumed that facilities were discharging at the maximum effluent 
concentrations taken from actual monitoring data, while the high-end 
scenario generally assumed that facilities were discharging at their 
current effluent limits. The decision matrix specified assumptions used 
for selection of control options, such as optimization of existing 
treatment processes and operations, in-plant pollutant minimization and 
prevention, and end-of-pipe treatment.
    Under this second baseline, where California is not presumed to 
implement narrative criteria pursuant to 40 CFR 122.44(d) in all 
permits, the annualized potential costs that direct and indirect 
dischargers may incur as a result of State implementation of permit 
limits based on water quality standards using today's proposed criteria 
are estimated to be between $15 million and $87 million. EPA believes 
that the costs incurred as a result of State implementation of these 
permit limits will approach the low-end of the cost range. Costs are 
unlikely to reach the high-end of the range because State authorities 
are likely to choose implementation options that provide some degree of 
flexibility or relief to point source dischargers. Furthermore, cost 
estimates for both scenarios, but especially for the high-end scenario, 
may be overstated because the analysis tended to use conservative 
assumptions in calculating these permit limits and in establishing 
baseline loadings. The baseline loadings for the high-end were based on 
current effluent limits rather than actual pollutant discharge data. 
Most facilities discharge pollutants in concentrations well below 
current effluent limits.
    Under the low-end cost scenario, major industrial facilities and 
POTWs incur about 65 percent of the potential costs, and indirect 
dischargers incur about 35 percent of the potential costs. Among the 
direct dischargers, two categories incur the majority of potential 
costs: POTWs (67 percent), and Chemical/Petroleum Products (18 
percent). The two highest average cost categories are Metals and 
Transportation Equipment ($57,000 per year) and POTWs ($27,000 per 
year). About 20 percent of the low-end costs are associated with 
pollution prevention activities, while 70 percent are associated with 
pursuing alternative methods of compliance under the regulations.
    Under the high-end cost scenario, major industrial facilities and 
POTWs incur about 96 percent of the potential costs, and indirect 
dischargers incur about 4 percent of the potential costs. Among the 
direct dischargers, three categories incur the majority of potential

[[Page 42190]]

costs--POTWs (70 percent), Chemical/Petroleum Products (18 percent), 
and Metals and Transportation Equipment (8 percent). The average annual 
per plant cost for different industry categories ranges from zero to 
$816,000. The two highest average cost categories under the second 
baseline are Metals and Transportation Equipment ($816,000 per year) 
and Chemical/Petroleum Products ($678,000 per year). The shift in 
proportion of potential costs between direct and indirect dischargers 
is due to the assumption that more direct dischargers will use end-of-
pipe treatment under the high-end scenario. Thus, a smaller proportion 
of indirect dischargers (10 percent) are impacted under the high-end 
scenario, since municipalities would add end-of-pipe treatment which 
would reduce the need for controls from indirect discharges. About 90 
percent of the costs are for capital and operating costs for wastewater 
treatment while about 10 percent of the high-end costs are associated 
with pollution prevention activities.
    Cost-Effectiveness: Cost-effectiveness is estimated in terms of the 
cost of reducing the loadings of toxic pollutants from point sources. 
The cost-effectiveness is derived by dividing the annual costs of 
implementing permit limits based on water quality standards using 
today's proposed criteria by the toxicity-weighted pounds (pound-
equivalents) of pollutants removed. Pound-equivalents are calculated by 
multiplying pounds of each pollutant removed by the toxic weight (based 
on the toxicity of copper) for that pollutant.
    Based on this analysis, State implementation of permit limits based 
on today's proposed criteria would be responsible for the reduction of 
about 630,000 to 7 million toxic pound-equivalents per year, or 18 to 
30 percent of the toxic-weighted baseline for the low- and high-end 
scenarios, respectively. The cost-effectiveness of the scenarios ranges 
from $8 to $12 per pound-equivalent.

3. Benefits

    The benefits analysis is intended to provide insight into both the 
types and potential magnitude of the economic benefits expected as a 
result of implementation of water quality standards based on today's 
proposed criteria. To the extent feasible, empirical estimates of the 
potential magnitude of the benefits are developed and then compared to 
the estimated costs of implementing water quality standards based on 
today's proposed criteria.
    To perform a benefits analysis, the types or categories of benefits 
that apply need to be defined. EPA relied on a set of benefits 
categories that typically applies to changes in the water resource 
environment. Benefits were categorized as either use benefits or 
passive (nonuse) benefits depending on whether or not they involve some 
source of direct use of, or contact with, the resource. The most 
prominent use benefit categories are those related to recreational 
fishing, boating, and swimming. Another use benefit category of 
significance is human health risk reduction. Human health risk 
reductions can be realized through actions that reduce human exposure 
to contaminants such as exposure through the consumption of fish 
containing elevated levels of pollutants. Passive use benefits are 
those improvements in environmental quality that are valued by 
individuals apart from any use of the resource in question.
    Benefits estimates were derived in this study using an approach in 
which benefits of discrete large-scale changes in water quality beyond 
present day conditions were estimated wherever feasible. A share of 
those benefits was then apportioned to implementation of water quality 
standards based on today's proposed criteria. The apportionment 
estimate was based on a three-stage process:
    First, EPA assessed current total loadings from all sources that 
are contributing to the toxics-related water quality problems observed 
in the State. This defines the overall magnitude of loadings. Second, 
the share of total loadings that are attributable to sources that would 
be controlled through implementation of water quality standards based 
on today's proposed criteria was estimated. Since this analysis was 
designed to focus only on those controls imposed on point sources, this 
stage of the process entailed estimating the portion of total loadings 
originating from point sources. Third, the percentage reduction in 
loadings expected due to implementation of today's proposed criteria 
was estimated and then multiplied by the share of point source loadings 
to calculate the portion of benefits that could be attributed to 
implementation of water quality standards based on today's proposed 
criteria.
    Total monetized annual benefits were estimated in the range of $1.5 
to $51.7 million. By category, annual benefits were $0.0 to $5.3 
million for avoided cancer risk, $0.6 to $10.1 million for recreational 
angling, and $0.9 to $36.3 million for passive use benefits.
    There are numerous categories of potential or likely benefits that 
have been omitted from the quantified and monetized benefit estimates. 
In terms of potential magnitudes of benefit, the following are likely 
to be significant contributors to the underestimation of the monetized 
values presented above:
    <bullet> Improvements in water-related (in-stream and near stream) 
recreation apart from fishing. The omission of potential motorized and 
nonmotorized boating, swimming, picnicking, and related in-stream and 
stream-side recreational activities from the benefits estimates could 
contribute to an appreciable underestimation of total benefits. Such 
recreational activities have been shown in empirical research to be 
highly valued, and even modest changes in participation and or user 
values could lead to sizable benefits statewide. Some of these 
activities can be closely associated with water quality attributes 
(notably, swimming). Other recreational activities may be less directly 
related to the water quality improvements, but might nonetheless 
increase due to their association with fishing, swimming, or other 
activities in which the participants might engage.
    <bullet> Improvements in consumptive and nonconsumptive land-based 
recreation, such as hunting and wildlife observation. Improvements in 
aquatic habitats may lead (via food chain and related ecologic benefit 
mechanisms) to healthier, larger, and more diverse populations of avian 
and terrestrial species, such as waterfowl, eagles, and otters. 
Improvements in the populations for these species could manifest as 
improved hunting and wildlife viewing opportunities, which might in 
turn increase participation and user day values for such activities. 
Although the scope of the benefits analysis has not allowed a 
quantitative assessment of these values at either baseline or post-rule 
conditions, it is conceivable that these benefits could be appreciable.
    <bullet> Improvements in human health resulting from reduction of 
non-cancer risk. EPA estimated that implementation of water quality 
standards based on the proposed criteria would result in a reduction of 
mercury concentrations in fish tissue and, thus, a reduction in the 
hazard from consumption of mercury contaminated fish. However, EPA was 
unable to monetize benefits due to reduced non-cancer health effects.
    <bullet> Human health benefits for saltwater anglers outside of San 
Francisco Bay were not estimated. The number of saltwater anglers 
outside of San Francisco Bay is estimated to be 673,000 (based on 
Huppert, 1989, and U.S. FWS, 1993). The omission of other saltwater 
anglers may cause human health benefits to be underestimated.

[[Page 42191]]

H. Executive Order 12875, Enhancing the Intergovernmental 
Partnership

    In compliance with Executive Order (E.O.) 12875 (58 FR 58093, 
October 28, 1993), EPA has involved the State and local governments in 
the development of this rule. In addition to the significant 
participation by State and local governments, several specific 
activities have been carried out. These include:
    (1) In early August 1995, EPA published and distributed to 
approximately 4,000 recipients, a four-page newsletter to notify 
California stakeholders that EPA would be proposing criteria for 
priority toxic pollutants, and to invite interested parties to a public 
meeting in late August 1995. The extensive distribution list came from 
the State's interested stakeholder list developed for its readoption of 
water quality control plans.
    (2) On August 24, 1995, EPA held two public meetings (one on the 
morning and one in the afternoon) to discuss the EPA' s promulgation 
with stakeholders and to answer any specific concerns. EPA announced 
that it would meet with any stakeholder group independently to discuss 
their group's concerns.
    (3) Since approximately December of 1993, EPA has been holding 
public Focus Group Meetings with the discharger community and the State 
to inform them of EPA's progress on the rulemaking and to learn about 
the State's progress on the readoption of its statewide water quality 
control plans. Over the last three and one-half years, EPA has held 
over 12 meetings.
    (4) In October of 1995, EPA and the State met with several leaders 
of the California's environmental community to discuss EPA's process 
and progress on its promulgation project and the State's process and 
progress on its readoption of statewide water quality control plans.
    (5) In December of 1994 and in March of 1996, EPA participated in 
the State's public meetings for its readoption of statewide plans. At 
each meeting, EPA gave a short update on its progress of promulgating 
toxic criteria and then answered specific questions from interested 
parties.
    (6) From April to October of 1995, EPA participated extensively in 
all eight of the State's Stakeholder Task Force groups which met 
monthly to discuss the State's readoption of statewide water quality 
control plans. When appropriate, EPA discussed its promulgation project 
and answered stakeholder questions concerning it.
    EPA plans to continue this extensive outreach to its stakeholder 
groups. Contact the person listed under the FOR FURTHER INFORMATION 
CONTACT section at the beginning of this preamble for more information.

I. The Unfunded Mandates Reform Act of 1995

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 
establishes requirements for federal agencies to assess the effects of 
their regulatory actions on State, local, and tribal governments and 
the private sector. Under section 202 of the UMRA, a federal agency 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with a ``federal mandate'' that 
may result in expenditures to State, local, and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating any regulation for which a written 
statement is needed, section 205 of the UMRA generally requires the 
agency to identify and consider a reasonable number of regulatory 
alternatives and adopt the least costly, most cost-effective or least 
burdensome alternative that achieves the objectives of the rule. The 
provisions of section 205 do not apply when they are inconsistent with 
applicable law. Moreover, section 205 allows an agency to adopt an 
alternative other than the least costly, most cost-effective or least 
burdensome alternative if the agency's Administrator publishes with the 
final rule an explanation why that alternative was not adopted. Before 
a federal agency establishes any regulatory requirements that may 
significantly or uniquely affect small governments, including tribal 
governments, it must have developed under section 203 of the UMRA a 
small government agency plan. The plan must provide for notifying 
potentially affected small governments, enabling officials of the 
affected small governments to have meaningful and timely input in the 
development of regulatory proposals with significant federal 
intergovernmental mandates, and for informing, educating, and advising 
small governments on compliance with the regulatory requirements. While 
EPA does not believe the rule would significantly or uniquely affect 
small governments, EPA has nevertheless made outreach efforts to small 
governments as is outlined in its small government agency plan.
    EPA has determined that this rule does not contain a federal 
mandate that may result in expenditures by State, local, and tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more in any one year. The proposed rule imposes no direct 
enforceable duties on the State or any local government or on the 
private sector; rather, this rule proposes ambient water quality 
criteria which, when combined with State-adopted designated uses, will 
create water quality standards for those water bodies with adopted 
uses. The State may use these resulting water quality standards in 
implementing its existing water quality control programs. Today's 
proposed rule does not directly regulate or affect any entity and, 
therefore, is not subject to the requirements of sections 202 and 205 
of the UMRA.
    As discussed above, EPA has examined the range of possible indirect 
impacts from State implementation of the rule in the National Pollutant 
Discharge Elimination System (NPDES) permit program. As discussed above 
in Section G, the State has significant flexibility in establishing and 
implementing NPDES permit limits. As a result, the analysis makes many 
assumptions concerning how the State will implement the water quality 
standards in the NPDES permit program. These assumptions are discussed 
in the analysis. The actual effect on any group of stakeholders is 
greatly dependent on the State's implementation.

J. The Regulatory Flexibility Act

    Under the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et seq.), 
federal agencies generally are required to conduct an initial 
regulatory flexibility analysis (IRFA) describing the impact of the 
regulatory action on small entities as part of a proposed rulemaking. 
However, under section 605(b) of the RFA, if the Administrator for the 
agency certifies that the proposed rule will not have a significant 
economic impact on a substantial number of small entities, the agency 
is not required to prepare an IRFA. The Administrator is today 
certifying, pursuant to section 605(b) of the RFA, that this proposed 
rule will not have a significant impact on a substantial number of 
small entities. Therefore, the Agency did not prepare an initial 
regulatory flexibility analysis.
    The RFA requires analysis of the impacts of a rule on the small 
entities subject to the rules' requirements. See United States 
Distribution Companies v. FERC, 88 F.3d 1105, 1170 (D.C. Cir. 1996). 
Today's rule establishes no requirements applicable to small entities, 
and so is not susceptible to regulatory flexibility analysis as 
prescribed by the RFA. (``[N]o [regulatory flexibility] analysis is 
necessary when an agency determines that the rule will not have a 
significant economic impact on a substantial

[[Page 42192]]

number of small entities that are subject to the requirements of the 
rule,'' United Distribution at 1170, quoting Mid-Tex Elec. Co-op v. 
FERC, 773 F.2d 327, 342 (D.C. Cir. 1985) (emphasis added by United 
Distribution court).) The Agency is thus certifying that today's rule 
will not have a significant economic impact on a substantial number of 
small entities, within the meaning of the RFA.
    Under the CWA water quality standards program, states must adopt 
water quality standards for their waters that must be submitted to EPA 
for approval; if the Agency disapproves a state standard and the state 
does not adopt appropriate revisions to address EPA's disapproval, EPA 
must promulgate standards consistent with the statutory requirements. 
EPA has authority to promulgate criteria or standards in any case where 
the Administrator determines that a revised or new standard is 
necessary to meet the requirements of the Act. These state standards 
(or EPA-promulgated standards) are implemented through various water 
quality control programs including the National Pollutant Discharge 
Elimination System (NPDES) program that limits discharges to navigable 
waters except in compliance with an EPA permit or permit issued under 
an approved state program. The CWA requires that all NPDES permits must 
include any limits on discharges that are necessary to meet state water 
quality standards.
    Thus, under the CWA, EPA's promulgation of water quality criteria 
or standards establishes standards that the state implements through 
the NPDES permit process. The state has discretion in deciding how to 
meet the water quality standards and in developing discharge limits as 
needed to meet the standards. While the state's implementation of 
federally-promulgated water quality criteria or standards may result in 
new or revised discharge limits being placed on small entities, the 
criteria or standards themselves do not apply to any discharger, 
including small entities.
    Today's rule, as explained above, does not itself establish any 
requirements that are applicable to small entities. As a result of 
EPA's action here, the State of California will need to ensure that 
permits it issues comply with the water quality standards established 
by the criteria in today's proposed rule. In so doing, the State will 
have a number of discretionary choices associated with permit writing. 
While California's implementation of today's rule may ultimately result 
in some new or revised permit conditions for some dischargers, 
including small entities, EPA's action today does not impose any of 
these as yet unknown requirements on small entities.
    Although the statute does not require EPA to prepare an IRFA when 
it proposes water quality criteria which will establish water quality 
standards for California, EPA has undertaken an analysis equivalent to 
an IRFA. This analysis focuses on State and local implementation 
procedures related to the NPDES permit program. This analysis is 
included in a document entitled, Implementation Analysis of Ambient 
Water Quality Criteria for Priority Toxic Pollutants in California 
which is part of the administrative record for this rulemaking. This 
document looks at the many implementation procedures of the NPDES 
permit program that the State implements to control pollutants from 
point source discharges. The procedures discussed in the document 
include: methods to calculate water quality-based effluent limits; 
mixing zones; site-specific translators for metals criteria; compliance 
schedules; effluent trading; water-effect ratios; variances; designated 
use reclassification; and site-specific criteria. Each of these 
implementation procedures can have an effect on how water quality 
standards, based on the criteria in today's proposed rule, will impact 
NPDES permit holders. Many of these procedures will lessen impacts on 
regulated entities.
    The document also looks at implementation procedures used in the 
pretreatment program to control pollutant discharges from indirect 
dischargers. Indirect dischargers include retail, commercial, and small 
industrial facilities that discharge to publicly owned treatment works 
(POTWs). Local entities have significant flexibility to implement their 
pretreatment programs. These procedures include: methods to calculate 
local limits (allocation of pollutants); methods of pollution 
prevention for various specific sources; pretreatment pollutant 
trading; methods of low cost pollutant reductions; technical assistance 
to move toward or achieve zero-discharge; cost accounting to drive down 
levels of discharges; and a few of the regulatory relief options 
discussed in the direct discharger section, e.g., compliance schedules.
    The discussion illustrates the significant amount of flexibility 
available to the State and local agencies when implementing the NPDES 
permit program and pretreatment program and emphasizes that appropriate 
use of the available implementation tools can greatly affect the impact 
to many direct and indirect dischargers.

K. The Paperwork Reduction Act

    This action requires no new or additional information collection 
subject to the Paperwork Reduction Act, 44 U.S.C. 3501 et seq., and 
therefore no information collection request will be submitted to the 
Office of Management and Budget for review.

L. The Endangered Species Act

    Pursuant to section 7(a) of the Endangered Species Act (ESA), EPA 
is consulting with the U.S. Fish and Wildlife Service (FWS) and the 
U.S. National Marine Fisheries Service (NMFS) concerning EPA's 
rulemaking action for the State of California. EPA has initiated 
informal consultation, and will complete informal and formal, if 
necessary, consultation before final action on the final rule. As a 
result of this consultation, EPA may modify some provisions of this 
proposed rule.
    As part of the ESA process, EPA will submit to FWS and NMFS a 
Biological Evaluation for their review. When submitted, this document 
will become part of the administrative record for this rulemaking. If 
EPA initiates formal consultation, the FWS and NMFS would issue a 
Biological Opinion which may include Reasonable and Prudent 
Alternatives (RPAs). EPA will then make decisions regarding 
implementation of any RPAs. EPA, FWS and NMFS will continue to work 
closely together on this ESA consultation process.

List of Subjects In 40 CFR Part 131

    Environmental protection, Indian-lands, Water pollution control, 
Water quality standard, Toxic pollutant.

    Dated: July 25, 1997.
Carol Browner,
Administrator.
    For the reasons set out in the preamble, part 131 of title 40 of 
the Code of Federal Regulations is proposed to be amended as follows:

PART 131--WATER QUALITY STANDARDS

    1. The authority citation for part 131 continues to read as 
follows:

    Authority: 33 U.S.C. 1251 et seq.

Subpart D--[Amended]

    2. Section 131.38 is added to subpart D to read as follows:


Sec. 131.38  Establishment of Numeric Criteria for Priority Toxic 
Pollutants for the State of California.

    (a) Scope. This section is a general promulgation of criteria for 
priority toxic pollutants in the State of

[[Page 42193]]

California for inland surface waters and enclosed bays and estuaries. 
This section also contains a compliance schedule provision.
    (b)(1) Criteria for Priority Toxic Pollutants in the State of 
California.

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BILLING CODE 6560-50-C

Footnotes:

    a. These criteria have been revised to reflect the Agency q1* or 
RfD, as contained in the Integrated Risk Information System (IRIS) 
as of October 1, 1996. The fish tissue bioconcentration factor (BCF) 
from the 1980 documents was retained in each case.
    b. This letter is not used as a footnote.
    c. These criteria are based on carcinogenicity of 10 (-6) risk.
    d. The Criteria Maximum Concentration (CMC) equals the highest 
concentration of a pollutant to which aquatic life can be

[[Page 42205]]

exposed for a short period of time without deleterious effects. 
Criteria Continuous Concentration (CCC) equals the highest 
concentration of a pollutant to which aquatic life can be exposed 
for an extended period of time (4 days) without deleterious effects. 
ug/l equals micrograms per liter.

    e. These freshwater aquatic life criteria for metals are 
expressed as a function of total hardness (mg/l) in the water body. 
The equations are provided in matrix at paragraph (b)(2) of this 
section. Values displayed above in the matrix correspond to a total 
hardness of 100 mg/l.
    f. 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).
    g. These aquatic life criteria for these compounds 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 as contrasted with a CMC which 
is a short-term average.
    h. These totals simply sum the criteria in each column. For 
aquatic life, there are 30 priority toxic pollutants with some type 
of freshwater or saltwater, acute or chronic criteria. For human 
health, there are 100 priority toxic pollutants with either ``water 
+ organism'' or ``organism only'' criteria. Note that these totals 
count chromium as one pollutant even though EPA has developed 
criteria based on two valence states. In the matrix, EPA has 
assigned numbers 5a and 5b to the criteria for chromium to reflect 
the fact that this list of 126 priority pollutants includes only a 
single listing for chromium.
    i. Criteria for these metals are expressed as a function of the 
water-effect ratio, WER, as defined in paragraph (c) of this 
section. CMC=column B1 or C1 value x WER; CCC=column B2 or C2 
value x WER.
    j. No criteria for protection of human health from consumption 
of aquatic organisms (excluding water) was presented in the 1980 
criteria document or in the 1986 Quality Criteria for Water. 
Nevertheless, sufficient information was presented in the 1980 
document to allow a calculation of a criterion, even though the 
results of such a calculation were not shown in the document.
    k. This criterion for asbestos is the MCL (40 CFR 131.36).
    l. This letter is not used as a footnote.
    m. These freshwater and saltwater criteria for metals are 
expressed in terms of the dissolved fraction of the metal in the 
water column. Criterion values were calculated by using EPA's Clean 
Water Act 304(a) guidance values (described in the total recoverable 
fraction) and then applying the conversion factors.
    n. EPA is not promulgating human health criteria for these 
contaminants. However, permit authorities should address these 
contaminants in NPDES permit actions using the State's existing 
narrative criteria for toxics.
    o. These criteria were promulgated for specific waters in 
California in the National Toxics Rule (``NTR''), codified at 40 CFR 
131.36, December 22, 1992, as amended by May 4, 1995. The specific 
waters to which the NTR criteria apply include: Waters of the State 
defined as bays or estuaries and waters of the State defined as 
inland, i.e., all surface waters of the State not ocean waters. 
These waters specifically include the San Francisco Bay upstream to 
and including Suisun Bay and the Sacramento-San Joaquin Delta.

    Note: This section does not supersede Sec. 131.36 (the NTR, as 
amended), for this criterion.

    p. The CMC = 1/[(f1/CMC1) + (f2/CMC2)] where f1 and f2 are the 
fractions of total selenium that are treated as selenite and 
selenate respectively, and f1 + f2 = 1. CMC1 and CMC2 are the CMCs 
for selenite and selenate, respectively, or 185.9 ug/l and 12.83 ug/
l, respectively. This criterion is in the total recoverable form. A 
criterion of 20 ug/l was promulgated for specific waters in 
California in the NTR, as amended, and was promulgated in the total 
recoverable form. The specific waters to which the NTR criterion 
applies include: Waters of the San Francisco Bay upstream to and 
including Suisun Bay and the Sacramento-San Joaquin Delta; and 
waters of Salt Slough, Mud Slough (north) and the San Joaquin River, 
Sack Dam to the mouth of the Merced River.

    Note: This rule does not supersede Sec. 131.36 (the NTR, as 
amended), for this criterion. The criterion in this section applies 
to additional waters of the United States in the State of California 
by this rulemaking.

    Note also: The State of California adopted and EPA approved a 
site specific criterion for the San Joaquin River, mouth of Merced 
to Vernalis; therefore, this criterion does not apply to these 
waters.

    q. This criterion is in the total recoverable form. This 
criterion was promulgated for specific waters in California in the 
NTR, as amended, and was promulgated in the total recoverable form. 
The specific waters to which the NTR criterion applies include: 
Waters of the San Francisco Bay upstream to and including Suisun Bay 
and the Sacramento-San Joaquin Delta; and waters of Salt Slough, Mud 
Slough (north) and the San Joaquin River, Sack Dam to Vernalis.
    Note: This section does not supersede Sec. 131.36 (the NTR, as 
amended), for this criterion. This criterion applies to additional 
waters of the United States in the State of California by this 
rulemaking.

    Note also: The State of California adopted and EPA approved a 
site-specific criterion for the Grassland Water District, San Luis 
National Wildlife Refuge, and the Los Banos State Wildlife Refuge; 
therefore, this criterion does not apply to these waters.

    r. These criteria were promulgated for specific waters in 
California in the NTR, as amended. The specific waters to which the 
NTR criteria apply include: Waters of the State defined as bays or 
estuaries including the San Francisco Bay upstream to and including 
Suisun Bay and the Sacramento-San Joaquin Delta.

    Note: This section does not supersede Sec. 131.36 (the NTR, as 
amended), for these criteria.

    s. These criteria were promulgated for specific waters in 
California in the NTR, as amended. The specific waters to which the 
NTR criteria apply include: Waters of the Sacramento-San Joaquin 
Delta and waters of the State defined as inland (i.e., all surface 
waters of the State not bays or estuaries or ocean) that include a 
MUN use designation.

    Note: This section does not supersede Sec. 131.36 (the NTR, as 
amended), for these criteria.

    t. These criteria were promulgated for specific waters in 
California in the NTR, as amended. The specific waters to which the 
NTR criteria apply include: Waters of the State defined as bays and 
estuaries including San Francisco Bay upstream to and including 
Suisun Bay and the Sacramento-San Joaquin Delta; and waters of the 
State defined as inland (i.e., all surface waters of the State not 
bays or estuaries or ocean) without a MUN use designation.

    Note: This section does not supersede Sec. 131.36 (the NTR, as 
amended), for these criteria.

    u. PCBs are a class of chemicals which include aroclors 1242, 
1254, 1221, 1232, 1248, 1260, and 1016, CAS numbers 53469219, 
11097691, 11104282, 11141165, 12672296, 11096825, and 12674112, 
respectively. The aquatic life criteria apply to this set of PCBs.
    v. This criterion applies to total PCBs or congener or isomer 
analyses.
    w. This criterion has been recalculated pursuant to the 1995 
Updates: Water Quality Criteria Documents for the Protection of 
Aquatic Life in Ambient Water, Office of Water, EPA-820-B-96-001, 
September 1996. See also Great Lakes Water Quality Initiative 
Criteria Documents for the Protection of Aquatic Life in Ambient 
Water, Office of Water, EPA-80-B-95-004, March 1995, available from 
the Water Resource Center, USEPA, 401 M St. SW., mail code RC 4100, 
Washington, DC 20460.
    x. The State of California has adopted and EPA has approved site 
specific criteria for the Sacramento River (and tributaries) above 
Hamilton City; therefore, these proposed criteria do not apply to 
these waters.

General Notes

    1. This chart lists all of EPA's priority toxic pollutants 
whether or not criteria guidance are available. Blank spaces 
indicate the absence of criteria guidance. Because of variations in 
chemical nomenclature systems, this listing of toxic pollutants does 
not duplicate the listing in Appendix A of 40 CFR Part 423. EPA has 
added the Chemical Abstracts Service (CAS) registry numbers, which 
provide a unique identification for each chemical.
    2. The following chemicals have organoleptic-based criteria 
recommendations that are not included on this chart (for reasons 
which are discussed in the preamble): zinc, 3-methyl-4-chlorophenol.
    3. For purposes of this section, freshwater criteria and 
saltwater criteria apply as specified in paragraph (c)(3) of this 
section.

    (2) Factors for Calculating Metals Criteria:

CMC = WER  x  (Acute Conversion Factor)  x  
(exp{m<INF>A</INF>[ln(hardness)]+b<INF>A</INF>})

[[Page 42206]]

CCC = WER  x  (Chronic Conversion Factor)  x  
(exp{m<INF>C</INF>[ln(hardness)]+b<INF>C</INF>})
    Final CMC and CCC values should be rounded to two significant 
figures.

                                                               Table 1 to Paragraph (b)(2)                                                              
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                      Conversion  factor (CF) for   CF for freshwater chronic      CF for saltwater acute        CF (a) for saltwater   
                Metal                  freshwater acute criteria             criteria                     criteria                 chronic criteria     
--------------------------------------------------------------------------------------------------------------------------------------------------------
Antimony............................  (d)                          (d)                          (d)                          (d)                        
Arsenic.............................  1.000                        1.000                        1.000                        1.000                      
Beryllium...........................  (d)                          (d)                          (d)                          (d)                        
Cadmium (b).........................  0.944                        0.909                        0.994                        0.994                      
Chromium (III)......................  0.316                        0.860                        (d)                          (d)                        
Chromium (VI).......................  0.982                        0.962                        0.993                        0.993                      
Copper..............................  0.960                        0.960                        0.83                         0.83                       
Lead (b)............................  0.791                        0.791                        0.951                        0.951                      
Mercury.............................  0.85                         0.85                         0.85                         0.85                       
Nickel..............................  0.998                        0.997                        0.990                        0.990                      
Selenium............................  (c)                          (c)                          0.998                        0.998                      
Silver..............................  0.85                         (d)                          0.85                         (d)                        
Thallium............................  (d)                          (d)                          (d)                          (d)                        
Zinc................................  0.978                        0.986                        0.946                        0.946                      
--------------------------------------------------------------------------------------------------------------------------------------------------------

Footnotes:

    (a) Conversion Factors for chronic marine criteria are not 
currently available. Conversion Factors for acute marine criteria 
have been used for both acute and chronic marine criteria.
    (b) Conversion Factors for these pollutants are hardness 
dependent. CFs are based on a hardness of 100 mg/l as calcium 
carbonate (CaCO<INF>3</INF>). Other hardness can be used; CFs should 
be recalculated using the following equations:

Cadmium: Acute: CF = 1.136672--[(ln {hardness})(0.041838)]
Chronic: CF = 1.101672--[(ln {hardness})(0.041838)]
Lead: Acute and Chronic: CF = 1.46203--[(ln {hardness})(0.145712)]

    (c) Bioaccumulative compound and inappropriate to adjust to 
percent dissolved.
    (d) EPA has not published an aquatic life criterion value.

    Note: The term ``Conversion Factor'' represents the recommended 
conversion factor for converting a metal criterion expressed as the 
total recoverable fraction in the water column to a criterion 
expressed as the dissolved fraction in the water column. See 
``Office of Water Policy and Technical Guidance on Interpretation 
and Implementation of Aquatic Life Metals Criteria'', October 1, 
1993, by Martha G. Prothro, Acting Assistant Administrator for 
Water, available from the Water Resource Center, USEPA, 401 M St. 
SW., mail code RC 4100, Washington, DC 20460; and Sec. 131.36(b)(1).

                                           Table 2 to Paragraph (b)(2)                                          
----------------------------------------------------------------------------------------------------------------
                          Metal                                m<INF>A            b<INF>A            m<INF>C            b<INF>C     
----------------------------------------------------------------------------------------------------------------
Cadmium.................................................        1.128        -3.6867        0.7852       -2.715 
Copper..................................................        0.9422       -1.700         0.8545       -1.702 
Chromium (III)..........................................        0.8190        3.688         0.8190        1.561 
Lead....................................................        1.273        -1.460         1.273        -4.705 
Nickel..................................................        0.8460        2.255         0.8460        0.0584
Silver..................................................        1.72         -6.52    ............  ............
Zinc....................................................        0.8473        0.884         0.8473        0.884 
----------------------------------------------------------------------------------------------------------------

    Note: The term ``exp'' represents the base e exponential 
function.

    (c) Applicability. (1) The criteria in paragraph (b) of this 
section apply to the State's designated uses cited in paragraph (d) of 
this section and apply concurrently with any criteria adopted by the 
State, except when State regulations contain criteria which are more 
stringent for a particular parameter and use, or except as provided in 
footnotes p, q, and x in paragraph (b) of this section.
    (2) The criteria established in this section are subject to the 
State's general rules of applicability in the same way and to the same 
extent as are other Federally-adopted and State-adopted numeric toxics 
criteria when applied to the same use classifications including mixing 
zones, and low flow values below which numeric standards can be 
exceeded in flowing fresh waters.
    (i) For all waters with mixing zone regulations or implementation 
procedures, the criteria apply at the appropriate locations within or 
at the boundary of the mixing zones; otherwise the criteria apply 
throughout the water body including at the point of discharge into the 
water body.
    (ii) The State shall not use a low flow value below which numeric 
standards can be exceeded that is less stringent than the following for 
water suitable for the establishment of low flow return frequencies 
(i.e., streams and rivers):

                              Aquatic Life                              
Acute Criteria (CMC):                    1 Q 10 or 1 B 3                
Chronic Criteria (CCC):                  7 Q 10 or 4 B 3                
                                                                        
                              Human Health                              
Non-carcinogens:                         30 Q 5                         
Carcinogens:                             Harmonic Mean Flow             
                                                                        

Where:

    CMC (Criteria Maximum Concentration) is the water quality 
criteria to protect against acute effects in aquatic life and is the 
highest instream concentration of a priority toxic pollutant 
consisting of a short-term average

[[Page 42207]]

not to be exceeded more than once every three years on the average;
    CCC (Continuous Criteria Concentration) is the water quality 
criteria to protect against chronic effects in aquatic life and is 
the highest in stream concentration of a priority toxic pollutant 
consisting of a 4-day average not to be exceeded more than once 
every three years on the average;
    1 Q 10 is the lowest one day flow with an average recurrence 
frequency of once in 10 years determined hydrologically;
    1 B 3 is biologically based and indicates an allowable 
exceedence of once every 3 years. It is determined by EPA's 
computerized method (DFLOW model);
    7 Q 10 is the lowest average 7 consecutive day low flow with an 
average recurrence frequency of once in 10 years determined 
hydrologically;
    4 B 3 is biologically based and indicates an allowable 
exceedence for 4 consecutive days once every 3 years. It is 
determined by EPA's computerized method (DFLOW model);
    30 Q 5 is the lowest average 30 consecutive day flow with an 
average recurrence frequency of once in 5 years determined 
hydrologically; and the harmonic mean flow is a long term mean flow 
value calculated by dividing the number of daily flows analyzed by 
the sum of the reciprocals of those daily flows.

    (iii) If the State does not have such a low flow value below which 
numeric standards do not apply, then the criteria included in paragraph 
(d) or this section herein apply at all flows.
    (3) The aquatic life criteria in the matrix in paragraph (b) of 
this section apply as follows:
    (i) For waters in which the salinity is equal to or less than 1 
part per thousand 95% or more of the time, the applicable criteria are 
the freshwater criteria in Column B;
    (ii) For waters in which the salinity is equal to or greater than 
10 parts per thousand 95% or more of the time, the applicable criteria 
are the saltwater criteria in Column C except for selenium in the San 
Francisco Bay estuary where the applicable criteria are the freshwater 
criteria in Column B (refer to footnotes p and q in section (b)(1) of 
this section); and
    (iii) For waters in which the salinity is between 1 and 10 parts 
per thousand as defined in paragraphs (c)(3)(i) and (ii) of this 
section, the applicable criteria are the more stringent of the 
freshwater or saltwater criteria. However, the Regional Administrator 
may approve the use of the alternative freshwater or saltwater criteria 
if scientifically defensible information and data demonstrate that on a 
site-specific basis the biology of the water body is dominated by 
freshwater aquatic life and that freshwater criteria are more 
appropriate; or conversely, the biology of the water body is dominated 
by saltwater aquatic life and that saltwater criteria are more 
appropriate.
    (4) Application of metals criteria. (i) For purposes of calculating 
freshwater aquatic life criteria for metals from the equations in 
paragraph (b)(2) of this section, for waters with a hardness of 400 mg/
l or less as calcium carbonate, the actual ambient hardness of the 
surface water shall be used in those equations. For waters with a 
hardness of over 400 mg/l as calcium carbonate, a hardness of 400 mg/l 
as calcium carbonate shall be used with a default Water-Effect Ratio 
(WER) of 1, or the actual hardness of the ambient surface water shall 
be used with a WER. The same provisions apply for calculating the 
metals criteria for the comparisons provided for in paragraph 
(c)(3)(iii) of this section.
    (ii) The hardness values used shall be consistent with the design 
discharge conditions established in paragraph (c)(2) of this section 
for flows and mixing zones.
    (iii) The criteria for metals (compounds #1-#13 in paragraph (b) of 
this section) are expressed as dissolved except where otherwise noted. 
For purposes of calculating aquatic life criteria for metals from the 
equations in footnote i in the criteria matrix in paragraph (b)(1) of 
this section and the equations in paragraph (b)(2) of this section, the 
water effect ratio is generally computed as a specific pollutant's 
acute or chronic toxicity value measured in water from the site covered 
by the standard, divided by the respective acute or chronic toxicity 
value in laboratory dilution water. To use a water effect ratio other 
than the default of 1, the WER must be determined as set forth in 
Interim Guidance on Determination and Use of Water Effect Ratios, U.S. 
EPA Office of Water, EPA-823-B-94-001, February 1994, or alternatively, 
other scientifically defensible methods adopted by the State as part of 
its water quality standards program and approved by EPA. For 
calculation of criteria using site-specific values for both the 
hardness and the water effect ratio, the hardness used in the equations 
in paragraph (b)(2) of this section must be determined as required in 
paragraph (c)(4)(ii) of this section. Water hardness must be calculated 
from the measured calcium and magnesium ions present, and the ratio of 
calcium to magnesium should be approximately the same in standard 
laboratory toxicity testing water as in the site water.
    (d)(1) Except as specified in paragraph (d)(3) of this section, all 
waters assigned any aquatic life or human health use classifications in 
the Water Quality Control Plans for the various Basins of the State 
(``Basin Plans''), as amended, adopted by the California State Water 
Resources Control Board (``SWRCB''), except for ocean waters covered by 
the Water Quality Control Plan for Ocean Waters of California (``Ocean 
Plan'') adopted by the SWRCB with resolution Number 90-27 on March 22, 
1990, are subject to the criteria in paragraph (d)(2) of this section, 
without exception. These criteria apply to waters contained in the 
Basin Plans. More particularly, these criteria apply to waters in the 
Basin Plan chapters specifying water quality objectives (the State 
equivalent of federal water quality criteria) for the toxic pollutants 
identified in paragraph (d)(2) of this section. Although the State has 
adopted several use designations for each of these waters, for purposes 
of this action, the specific standards to be applied in paragraph 
(d)(2) of this section are based on the presence in all waters of some 
aquatic life designation and the presence or absence of the MUN use 
designation (municipal and domestic supply). (See Basin Plans for more 
detailed use definitions.)
    (2) The following criteria from the matrix in paragraph (b)(1) of 
this section apply to the water and use classifications defined in 
paragraph (d)(1) of the section and identified below:

------------------------------------------------------------------------
      Water and use classification             Applicable Criteria      
------------------------------------------------------------------------
All inland waters of the United States   These waters are assigned the  
 or enclosed bays and estuaries that      criteria in:                  
 are waters of the United States that    Columns B1 and B2--all         
 include a MUN use designation.           pollutants                    
                                         Columns C1 and C2--all         
                                          pollutants                    
                                         Column D1--all pollutants      
All inland waters of the United States   These waters are assigned the  
 or enclosed bays and estuaries that      criteria in:                  
 are waters of the United States that    Columns B1 and B2--all         
 do not include a MUN use designation.    pollutants                    
                                         Columns C1 and C2--all         
                                          pollutants                    
                                         Column D2--all pollutants      
------------------------------------------------------------------------


[[Page 42208]]

    (3) Nothing in this section is intended to supersede specific 
criteria, including specific criteria for the San Francisco Bay 
estuary, promulgated for California in Sec. 131.36.
    (4) The human health criteria shall be applied at the State-adopted 
10 (-6) risk level.
    (5) Nothing in this section applies to waters located in Indian 
Country.
    (e) Schedules of Compliance: (1) It is presumed that new and 
existing point source dischargers will promptly comply with any new or 
more restrictive water quality-based effluent limitations (``WQBELs'') 
based on the water quality criteria set forth in this section.
    (2) When a permit issued on or after the effective date of this 
regulation to a new discharger contains a WQBEL based on water quality 
criteria set forth in the section, the permittee shall comply with such 
WQBEL upon the commencement of the discharge. A new discharger is 
defined as any building, structure, facility, or installation from 
which there is or may be a ``discharge of pollutants'' (as defined in 
40 CFR 122.2) to the State of California's inland surface waters or 
enclosed bays and estuaries, the construction of which commenced after 
the effective date of this regulation.
    (3) Where an existing discharger reasonably believes that it will 
be infeasible to promptly comply with a new or more restrictive WQBEL 
based on the water quality criteria set forth in this section, the 
discharger may request approval from the permit issuing authority for a 
schedule of compliance.
    (4) A compliance schedule shall require compliance with WQBELs 
based on water quality criteria set forth in this section as soon as 
possible, taking into account the dischargers technical ability to 
achieve compliance with such WQBEL.
    (5) If the schedule of compliance exceeds one year from the date of 
permit issuance, reissuance or modification, the schedule shall set 
forth interim requirements and dates for their achievement. The dates 
of completion between each requirement may not exceed one year. If the 
time necessary for completion of any requirement is more than one year 
and is not readily divisible into stages for completion, the permit 
shall require, at a minimum, specified dates for annual submission of 
progress reports on the status of interim requirements.
    (6) In no event shall the permit issuing authority approve a 
schedule of compliance for a point source discharge which exceeds five 
years from the date of permit issuance, reissuance, or modification, 
whichever is sooner. Where shorter schedules of compliance are 
prescribed or schedules of compliance are prohibited by law, those 
provisions shall govern.
    (7) If a schedule of compliance exceeds the term of a permit, 
interim permit limits effective during the permit shall be included in 
the permit and addressed in the permit's fact sheet or statement of 
basis. The administrative record for the permit shall reflect final 
permit limits and final compliance dates. Final compliance dates for 
final permit limits, which do not occur during the term of the permit, 
must occur within five years from the date of issuance, reissuance or 
modification of the permit which initiates the compliance schedule. 
Where shorter schedules of compliance are prescribed or schedules of 
compliance are prohibited by law, those provisions shall govern.
    (8) No compliance schedule established in accordance with 
paragraphs (e)(3) through (7) of this section shall allow more than ten 
years from the effective date of this rule to achieve compliance with 
any WQBEL based on the criteria set forth in this section.
[FR Doc. 97-20173 Filed 8-4-97; 8:45 am]
BILLING CODE 6560-50-P