[Federal Register Volume 60, Number 86 (Thursday, May 4, 1995)]
[Rules and Regulations]
[Pages 22229-22237]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-10148]



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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[WH-FRL-5196-1]


Water Quality Standards; Establishment of Numeric Criteria for 
Priority Toxic Pollutants; States' Compliance--Revision of Metals 
Criteria

AGENCY: Environmental Protection Agency (EPA).

ACTION: Interim final rule, notice of data availability and request for 
comments.

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SUMMARY: EPA is promulgating new aquatic life metals criteria for nine 
States, Puerto Rico, and the District of Columbia, that are subject to 
EPA's 1992 National Toxics Rule (``NTR''). These new metals criteria 
reflect EPA's current policy for setting water quality criteria for 
metals. This interim final rule establishes metals criteria that are 
protective of aquatic life and approximate, better than the 1992 
criteria, the biologically available fraction of water borne metals to 
aquatic organisms. Use of the new metals criteria will allow permitting 
authorities in the nine States, Puerto Rico and the District of 
Columbia, to establish effluent limitations based on the new metals 
criteria rather than the 1992 criteria which EPA now considers to be 
more stringent than may be necessary to protect designated uses for 
aquatic life. The interim final rule will be in effect while EPA 
considers public comments and develops a final rule. This rule 
terminates the Administrative Stay published elsewhere in this issue of 
the Federal Register.

DATES: This interim final rule is effective April 15, 1995. Comments on 
the interim final rule and other data noticed in this preamble will be 
accepted until July 3, 1995.

ADDRESSES: An original and 3 copies of all comments and references on 
the interim final rule and data should be addressed to: Revision of the 
National Toxics Rule-Dissolved Metals Criteria, Comment Clerk; Water 
Docket (MC-4101), U.S. Environmental Protection Agency, 401 M Street 
SW., Washington, DC 20460. The administrative record for this 
rulemaking is available for review and copying at the Environmental 
Protection Agency, Office of Water Docket, 401 M Street SW, Washington 
DC, 20460, Room L102, on weekdays during EPA's normal business hours of 
8 a.m. until 4:30 p.m. For access to the Docket materials, call (202) 
260-3027 between 9:00a.m.-3:30p.m., for an appointment. A reasonable 
fee will be charged for photocopies.

FOR FURTHER INFORMATION CONTACT: Timothy J. Kasten, telephone 202-260-
5994.

SUPPLEMENTARY INFORMATION:

A. General Background

1. Regulatory Background

    In the NTR, EPA promulgated numeric water quality criteria for 12 
States, Puerto Rico, and the District of Columbia, that failed to 
comply fully with Section 303(c)(2)(B) of the Clean Water Act. (57 FR 
60848, December 22, 1992 codified in the Code of Federal Regulations at 
40 CFR 131.36).<SUP>1 Those criteria became the legally enforceable 
water quality standards in the named States, Puerto Rico, and the 
District of Columbia, for all purposes and programs under the Clean 
Water Act on February 5, 1993. Included among the water quality 
criteria promulgated in the NTR were numeric criteria for the 
protection of aquatic life for 11 metals: arsenic, cadmium, chromium 
(III), chromium (VI), copper, lead, mercury, nickel, selenium, silver, 
and zinc.

    \1\In the NTR, EPA determined compliance with Section 
303(c)(2)(B) based on the status of State compliance as of 1991, the 
date of the proposed rulemaking, and then took into account EPA 
approval actions between the proposed and final rulemaking for those 
States included in the proposed rule. EPA acknowledges that, due to 
subsequent State actions to delete or otherwise modify toxics 
criteria (e.g., see Table 1, 57 FR 60856, December 22, 1992), all 
States and Territories currently may not be in full compliance with 
Section 303(c)(2)(B).
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    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.
2. Policy on Aquatic Life Metals Criteria

    At the time of the NTR promulgation, Agency policy was to express 
metals criteria, as recommended in its Section 304(a) criteria 
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.<SUP>2 
[[Page 22230]] Because the NTR was to cover a substantial number of 
water bodies of varying water quality, EPA selected what it considered 
the simplest, more conservative approach and the approach reflected in 
its criteria documents, to implement the metals criteria, namely the 
total recoverable method. Accordingly, the metals criteria promulgated 
in the NTR were expressed as total recoverable metals, although EPA 
also provided for site-specific criteria development.<SUP>3

    \2\Interim Guidance on Interpretation and Implementation of 
Aquatic Life Criteria for Metals, U.S. EPA, May 1992. (Notice of 
availability published at 57 FR 24041, June 5, 1992.)
    \3\See Interim Guidance on the Determination and Use of Water-
Effect Ratios for Metals, February 1994, EPA 823-B-94-001.
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    Thereafter, EPA continued to work with States and other interested 
parties on the issue of metals bioavailability and toxicity. EPA held a 
workshop of invited experts on this issue; the results of the 
consultations were published at 58 FR 32131, June 8, 1993. As a result 
of these 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 (``Metals Policy''). (The complete October 1, 1993 memorandum 
can be obtained from EPA's Office of Water Resource Center (202) 260-
7786 or the Office of Water Docket.) 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 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. (See Section 510, 
Federal Water Pollution Control Act, Public Law 100-4, 33 U.S.C. 466 
et seq.)

    The adoption of the Metals Policy did not change the Agency's 
position that the existing total recoverable criteria published under 
Section 304(a) of the Clean Water Act continue to be scientifically 
defensible. EPA developed the total recoverable criteria using high-
quality analytical data and are still scientifically defensible 
criteria. When developing and adopting its own standards, a State, in 
making its risk management decision, may wish to consider sediment, 
food chain effects and other fate-related issues and decide to adopt 
total recoverable or dissolved metals criteria.
    In general, EPA continues to conduct research on metals toxicity to 
further refine the criteria and their implementation. However, the aim 
of both the Clean Water Act and EPA policy is that a more effective way 
of incorporating new science into the water quality program is for the 
States to promulgate their own standards and implementation policies. 
The States can then make appropriate updates, rather than relying on 
Federal promulgations such as today's rule.

3. Litigation and Settlement of NTR Metals Issues

    A number of parties brought lawsuits challenging the NTR metals 
criteria. See American Forest and Paper Ass'n, Inc. et al. v. 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. After 
careful consideration of the issue, 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 partial settlement 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. That 
stay is published in a separate notice in today's Federal Register. The 
stay is intended to be in effect only until EPA takes action to amend 
the NTR by promulgating new metals criteria based on dissolved metal. 
With today's interim final rule, EPA is promulgating new metals 
criteria for those metals listed in the stay based on dissolved metal 
and therefore this action will supersede the administrative stay.

B. Today's Interim Final Rule

    EPA's action today revises the NTR that established numeric aquatic 
life metals criteria for 9 States, Puerto Rico and the District of 
Columbia (Table 1). (Of the 12 NTR States, aquatic life metals criteria 
were only promulgated for nine.) The numeric criteria in today's rule 
reflect the Office of Water's current policy with respect to metals. 
This action promulgates dissolved metals criteria for those total 
recoverable metals criteria subject to the Agency's administrative 
stay.

       Table 1.--States Subject to the Revised Metals Criteria\1\       
                                                                        
                                                                        
Alaska                                                                  
Arkansas                                                                
California                                                              
Idaho                                                                   
Kansas                                                                  
Michigan                                                                
New Jersey                                                              
Vermont                                                                 
Washington                                                              
District of Columbia                                                    
Puerto Rico                                                             
\1\Today's interim final rule may have differing applicability for each 
  of the States in this table depending on the State's individual       
  compliance with Section 303(c)(2)(B) of the Clean Water Act. See 40   
  CFR 131.36(d) for State applicability.                                

C. Conversion Factors: Total Recoverable to Dissolved Metal

    Because EPA's Section 304(a) criteria are expressed as total 
recoverable metal, to express the criteria as dissolved, application of 
a conversion factor is necessary to account for the particulate metal 
present 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 has refined the procedures used to develop freshwater 
conversion factors for aquatic life criteria. EPA made new conversion 
factors available for public comment in the context of EPA's Proposed 
Guidance for the Great Lakes System on August 30, 1994, at 59 FR 44678.
    EPA has also conducted saltwater laboratory simulation tests for 
the development of conversion factors for saltwater metals criteria. 
The saltwater simulation tests were conducted using the same 
methodology as the freshwater tests with minor modifications, necessary 
to account for saltwater. The saltwater test results are being made 
available with today's rule. The conversion factors in this rule and 
other technical reports referenced herein, supersede the conversion 
factors presented in Attachment #2 of the Metals Policy.
    Total recoverable to dissolved metal conversion factors were 
attached to the partial settlement agreement in the form of a draft 
guidance entitled, Guidance to States Subject to the National Toxics 
Rule For Setting NPDES Limits During the Stay of the Metals Criteria. 
(The partial settlement agreement is available from the Water Docket.) 
The draft guidance used data that were available through December 21, 
1994. The [[Page 22231]] conversion factors presented in today's rule 
reflect the best science available to EPA at the time of promulgation 
and contain minor modifications from those in the attachment to the 
February 15 partial settlement agreement. For each metal specific 
conversion factor, the changes between the draft guidance and today's 
rule are less than 10%. EPA has determined these changes to be minor.

1. Freshwater Criteria Conversion Factors

    The final freshwater conversion factors used in today's rule are 
contained in: ``Derivation of Conversion Factors for the Calculation of 
Dissolved Freshwater Aquatic Life Criteria for Metals'' (U.S. EPA, 
1995), available from the Water Docket and are presented in Table 2 
below. 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.
    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. Table 2 presents the hardness-dependent conversion factors 
for cadmium and lead. The hardness-dependent conversion factor for lead 
was included in the August 30, 1994 Notice of Availability (59 FR 
44678). In today's action, EPA is specifically requesting comment on 
the use of hardness-dependent conversion factor for cadmium.

  Table 2.--Freshwater Criteria Conversion Factors for Dissolved Metals 
------------------------------------------------------------------------
                                                     Conversion factors<SUP>a
                       Metal                       ---------------------
                                                      Acute     Chronic 
------------------------------------------------------------------------
Arsenic...........................................      1.000      1.000
Cadmium<SUP>b..........................................      0.944      0.909
Chromium (III)....................................      0.316      0.860
Chromium(VI)......................................      0.982      0.962
Copper............................................      0.960      0.960
Lead<SUP>b.............................................      0.791      0.791
Mercury...........................................      <SUP>c0.85       <SUP>dN/A
Nickel............................................      0.998      0.997
Silver............................................      <SUP>c0.85       <SUP>eN/A
Zinc..............................................      0.978     0.986 
------------------------------------------------------------------------
<SUP>aThe conversion factors are given to three decimal places because they  
  are intermediate values in the calculation of dissolved criteria.     
<SUP>bConversion factors are hardness-dependent. The values shown are with a 
  hardness of 100 mg/L as calcium carbonate (CaCO<INF>3). Conversion factors 
  (CF) for any hardness can be calculated 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)]          
                                                                        
<SUP>cConversion factor from: Office of Water Policy and Technical Guidance  
  on Interpretation and Implementation of Aquatic Life Metals Criteria, 
  October 1, 1993. Factors were expressed to two decimal places.        
<SUP>dCCC for mercury cannot be converted to dissolved, because it is based  
  on mercury residues in aquatic organisms rather than toxicity.        
<SUP>eNot applicable, EPA has not published final chronic criteria values for
  silver.                                                               

2. Saltwater Criteria Conversion Factors

    Acute saltwater conversion factors are being made available through 
today's rule. The data and the acute criteria conversion factors for 
saltwater are contained in: ``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 from the Water Docket. Saltwater chronic conversion factors 
have not been developed separately and therefore are not available for 
today's rule. Based on close similarities between the 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 will apply. The 
saltwater conversion factors are presented in Table 3 below. Saltwater 
simulation tests were not completed for mercury or silver, therefore 
the conversion factors from the Metals Policy will continue to apply.

  Table 3.--Saltwater Criteria Conversion Factors for Dissolved Metals  
------------------------------------------------------------------------
                                                              Conversion
                            Metal                              factors<SUP>a 
------------------------------------------------------------------------
Arsenic.....................................................      1.000 
Cadmium.....................................................      0.994 
Chromium (III)..............................................        (<SUP>d) 
Chromium (VI)...............................................      0.993 
Copper......................................................       0.83 
Lead........................................................      0.951 
Mercury.....................................................     <SUP>bc0.85 
Nickel......................................................      0.990 
Selenium....................................................      0.998 
Silver......................................................      <SUP>b0.85 
Zinc........................................................     0.946  
------------------------------------------------------------------------
<SUP>aConversion factors on this table were calculated for acute criteria    
  only. Conversion factors for chronic criteria are not currently       
  available. In the absence of chronic conversion factors saltwater     
  acute conversion factors are used.                                    
<SUP>bConversion factor from: Office of Water Policy and Technical Guidance  
  on Interpretation and Implementation of Aquatic Life Metals Criteria, 
  October 1, 1993. Factors were expressed to two decimal places.        
<SUP>cCCC for mercury cannot be converted to dissolved, because it is based  
  on mercury residues in aquatic organisms rather than toxicity.        
<SUP>dNo saltwater criteria.                                                 

D. Applicability Requirements for Metals Criteria

    Through today's action, EPA is also requesting comments on the 
applicability requirements in 40 CFR 131.36(c) as they apply to the 
metals criteria. In particular, EPA is requesting comments on 
Sec. 131.36(c)(4)(i) regarding the calculation of hardness-dependent 
freshwater metals criteria. Section 131.36(c)(4)(i) describes the 
minimum and maximum hardness values (25 mg/L and 400 mg/L as 
CaCO<INF>3, respectively) to be used when calculating hardness-
dependent freshwater metals criteria. This requirement is not changed 
by today's interim final rule, however EPA is requesting comment on an 
alternative approach. Most of the data used to develop these hardness 
formulas were in the hardness range of 25 mg/L to 400 mg/L as 
CaCO<INF>3. The formulas are therefore most accurate in this range. 
Using a hardness of 25 mg/L for calculating criteria, when the actual 
ambient hardness is less than 25 mg/L, could result in criteria that 
are under-protective of aquatic life. EPA is therefore requesting 
comments on the use of the actual ambient hardness for calculating 
criteria when the hardness is below 25 mg/L as CaCO<INF>3.
    Most freshwaters of the U.S. have an ambient hardness of less than 
400 mg/L as CaCO<INF>3. Using 400 mg/L to calculate criteria, for 
waters with an ambient hardness of greater than 400 mg/L, may result in 
over-protective criteria because at a hardness above 400 mg/L, other 
confounding factors, which may cause this hardness, can also affect the 
toxicity. EPA is requesting comment on an approach that would make two 
options available for calculating metals criteria for waters with a 
hardness of greater than 400 mg/L as CaCO<INF>3: Option 1--use 400 mg/L 
as CaCO<INF>3 for the criteria calculation or, Option 2--use the actual 
hardness and require the use of the water-effect ratio to modify the 
final criteria value to more accurately reflect ambient conditions. 
(EPA notes that in the NTR States, the use of the water-effect ratio is 
assigned a value of 1.0, unless otherwise specified by the permitting 
authority. See 40 CFR 131.36(c)(4)(iii).) [[Page 22232]] 

E. Calculation of Dissolved Metals Criteria

    Metals criteria values in 40 CFR 131.36(b)(1), as amended today, 
are now shown as dissolved metal. These criteria have been calculated 
in one of two ways. For freshwater metals criteria that are hardness-
dependent (denoted by footnote ``e'' in the matrix), the dissolved 
metal criteria value must be calculated separately for each hardness 
using the table at Sec. 131.36(b)(2), as amended today. The hardness-
dependent freshwater criteria values presented in the matrix at 
Sec. 131.36(b)(1) have been calculated using a hardness of 100 mg/L 
CaCO<INF>3 for comparative purposes only. Saltwater metals criteria and 
freshwater criteria that are not hardness-dependent (criteria denoted 
by footnote ``m'' in the matrix) are calculated by taking the total 
recoverable criteria values (from EPA National Ambient Water Quality 
Criteria Documents) before rounding, and multiplying them by the 
appropriate conversion factors from Table 2 or 3 of Section C of this 
preamble. (The total recoverable criteria values are shown to four 
figures, where available, because they are intermediate values in the 
calculation of dissolved metals criteria.) The final dissolved metals 
criteria values, as they appear in the matrix at Sec. 131.36(b)(1), are 
rounded to two significant figures. Tables 4a and 4b below, summarize 
the conversions for saltwater criteria and freshwater criteria that are 
not hardness-dependent.
    EPA notes that if a non-NTR State adopts standards, or an NTR State 
adopts its own standards (for subsequent withdrawal from the NTR), it 
may prefer a more conservative approach and adopt total recoverable 
metals criteria. In doing so, the State may use EPA's total recoverable 
criteria from Tables 4a and 4b (rounded to two significant figures) or, 
for hardness-dependent freshwater criteria, omit the conversion factor 
from the formula presented in Sec. 131.36(b)(2).
    Tables 4a and 4b use the following abbreviations and formulas for 
calculating dissolved metals criteria (CMC and CCC are defined in 40 
CFR 131.36(b)(1), footnote d):

CMC--Criterion Maximum Concentration
CCC--Criterion Continuous Concentration
CF--Conversion Factor

    Formulas for Calculating Dissolved Metals Criteria:

CMC<INF>dissolved = CMC<INF>total recoverable  x  Acute CF
CCC<INF>dissolved = CCC<INF>total recoverable  x  Chronic CF

         Table 4a.--Calculation of Freshwater Dissolved Metals Criteria That are Not Hardness-Dependent         
----------------------------------------------------------------------------------------------------------------
                                 Total Recoverable Metals     Conversion factors\2\         Dissolved metals    
                                Criteria\1\ (<greek-m>g/L) ---------------------------        criteria\3\       
             METAL             ----------------------------                           --------------------------
                                     CMC           CCC          Acute       Chronic         CMC          CCC    
----------------------------------------------------------------------------------------------------------------
Arsenic.......................       359.1        188.9            1.000        1.000         360            190
Chromium(VI)..................        15.74        10.80           0.982        0.962          15             10
Mercury.......................         2.428        0.0122         0.85           N/A           2.1         N/A 
----------------------------------------------------------------------------------------------------------------
\1\From EPA National Ambient Water Quality Criteria Documents.                                                  
\2\From Table 2.                                                                                                
\3\Final dissolved metals criteria have been rounded to two significant figures.                                


                          Table 4b.--Calculation of Saltwater Dissolved Metals Criteria                         
----------------------------------------------------------------------------------------------------------------
                               Total recoverable metals      Conversion factors\2\         Dissolved metals     
                              criteria\1\ (<greek-m>g/L) ----------------------------         criteria\3\       
            Metal            ----------------------------                            ---------------------------
                                   CMC           CCC          Acute        Chronic         CMC           CCC    
----------------------------------------------------------------------------------------------------------------
Arsenic.....................        68.55        36.05           1.000         1.000          69            36  
Cadmium.....................        42.54         9.345          0.994         0.994          42             9.3
Chromium (III)..............    N/A\4\       N/A\4\         N/A\4\        N/A\4\          N/A\4\        N/A\4\  
Chromium (VI)...............      1079           49.86           0.993         0.993        1100            50  
Copper......................         2.916        2.916          0.83          0.83            2.4           2.4
Lead........................       217.16         8.468          0.951         0.951         210             8.1
Mercury.....................         2.062         .0250         0.85     N/A\5\               1.8      N/A\5\  
Nickel......................        74.60         8.293          0.990         0.990          74             8.2
Selenium....................       293.8         70.69           0.998         0.998         290            71  
Silver......................         2.3     N/A\4\              0.85     N/A\4\               1.9      N/A\4\  
Zinc........................        95.10        86.14           0.946         0.946          90           81   
----------------------------------------------------------------------------------------------------------------
\1\From EPA National Ambient Water Quality Criteria Documents.                                                  
\2\From Table 3.                                                                                                
\3\Final dissolved metals criteria have been rounded to two significant figures.                                
\4\Not applicable, national criteria not available.                                                             
\5\The CCC for mercury is expressed as total recoverable.                                                       

F. Site-Specific Criteria Modifications

    EPA has issued guidance (Water Quality Standards Handbook, Second 
Edition-1993, EPA-823-B-93-002 and update #1, EPA-823-B-94-006, August 
1994, at page 3-38 and Appendix L), describing three site-specific 
criteria development methodologies: recalculation procedure, indicator 
species procedure (also known as the water-effect ratio (WER)) and 
resident species procedure. Only the first two of these have been 
widely used.
    In the NTR, EPA identified the WER as the method for optional site-
specific criteria development for certain metals. On February 22, 1994, 
EPA issued Interim Guidance on the Determination and Use of 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 [[Page 22233]] appropriate, EPA strongly 
encourages the application of the WER on a watershed or waterbody basis 
as opposed to application on a discharger-by-discharger basis. This 
approach is technically sound, an efficient use of resources, and 
allowable for permitting authorities under the NTR.
    EPA's endorsement of the use of the WER is not affected by today's 
rule. As noted in the NTR at 57 FR 60879, 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 rule, 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, Appendix D, 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 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.
    Because WERs for dissolved criteria generally are little affected 
by particulate concentrations, those WERS also may often exhibit less 
time variability than WERs for total recoverable criteria. 
Consequently, WER-adjusted dissolved criteria may have somewhat greater 
certainty than WER-adjusted total recoverable criteria.
    EPA expects the use of WERs for dissolved criteria to provide the 
same level of protection as the use of WERs for total recoverable 
criteria in the NTR. However, the increased reliability of the 
dissolved criteria prior to WER adjustment (compared to the total 
recoverable criteria unadjusted) will reduce the need for site-specific 
WER determinations.

G. Technical Guidance

    EPA continues to urge the States affected by this rule to adopt 
their own standards and negate the need for Federal action. Should a 
State choose to adopt dissolved criteria, EPA recommends use of the 
Metals Policy, its attachments (as updated herein) and other guidance 
referenced in this preamble for implementation of dissolved metals 
criteria. Attachments to the Metals Policy include: guidance on dynamic 
modeling and translators (Attachment #3), and clean analytical 
techniques and monitoring (Attachment #4). Additional guidance on clean 
and ultra-clean techniques is available and under development (see 
discussion below). EPA will continue to update implementation guidance 
as needed in the future.

1. Total Maximum Daily Loads (TMDLs) and National Pollutant Discharge 
Elimination System (NPDES) Permits

    EPA's NPDES regulations require that limits for metals in permits 
be stated as total recoverable in most cases {see 40 CFR 
Sec. 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 Clean Water Act. 
This is because the chemical conditions in ambient waters frequently 
differ substantially from those in the effluent and there is no 
assurance that effluent particulate metal would not dissolve after 
discharge. The NPDES permit regulations do not require that State 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. 
Both the TMDL and NPDES permit use of water quality criteria in NTR 
States now require the ability to translate between dissolved metal in 
ambient waters and total recoverable metal in effluents. In addition to 
the guidance on dynamic modeling and translators attached to the Metals 
Policy, EPA's Interim Guidance on the Determination and Use of Water-
Effect Ratios for Metals, February 1994, EPA 823-B-94-001 (pages 116 
and 128-130), presents an effluent-specific approach for calculating a 
total recoverable metal permit limit from a dissolved metal criterion. 
EPA is expecting to complete additional guidance on translators in 
1995.

2. Monitoring

a. Use of Clean Sampling and Analytical Techniques
    In assessing waterbodies to determine the potential for toxicity 
problems due to metals, the quality of the data used is an important 
issue. Depending on the concentration of metal present, the use of 
``clean'' and ``ultra-clean'' techniques for sampling and analysis may 
be critical to accurate data for implementation of aquatic life 
criteria for metals.
    ``Clean'' techniques refer to those requirements (or practices for 
sample collection and handling) necessary to produce reliable 
analytical data in the microgram per liter (<greek-m>g/L) or part per 
billion (ppb) range. ``Ultra-clean'' techniques refer to those 
requirements or practices necessary to produce reliable analytical data 
in the nanogram per liter (ng/L) or part per trillion (ppt) range. 
Because typical concentrations of metals in surface waters and 
effluents vary from one metal to another, the effect of contamination 
on the quality of metals monitoring data varies appreciably.
    EPA has developed protocols on the use of clean techniques in 
coordination with the United States Geological Survey (USGS). The 
guidance, entitled Method 1669: Sampling Ambient Water for 
Determination of Trace Metals at EPA Water Quality Criteria Levels is 
available from the Office of Water Resource Center as part of the Trace 
Metals Package. Draft protocols for ultra-clean techniques will be 
available in late calendar year 1995.

H. Saltwater Copper Criteria

    The saltwater copper criteria in today's interim final rule are 2.4 
<greek-m>g/L dissolved copper for both CMC and CCC based on conversion 
of 2.9 <greek-m>g/L for both the CMC and CCC from total recoverable to 
dissolved metal. New data collected from a study for the New York/New 
Jersey Harbor indicate the potential need to revise the copper criteria 
document to reflect a change in the saltwater CMC and CCC aquatic life 
values. A comprehensive literature search was conducted and toxicity 
test data for seven new species were added to the database for the 
saltwater copper criteria. EPA believes these new data have national 
implications and indicate the national criteria may be more accurate at 
a CMC of 4.8 <greek-m>g/L dissolved and a CCC of 3.1 <greek-m>g/L 
dissolved. In today's rulemaking, EPA is noticing the availability of 
data to support these [[Page 22234]] potential changes in the national 
saltwater copper criteria and solicits 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 or Water Docket. Based on those comments, the saltwater 
copper criteria in this interim final rule may be revised in the final 
rule to reflect these new data.

I. Procedural Requirements

    Section 553 of the Administrative Procedure Act provides that when 
an agency, for good cause, finds that notice and public procedure are 
impracticable, unnecessary or contrary to the public interest, it may 
first issue a rule without providing notice and an opportunity to 
comment. EPA has concluded that there is good cause to issue this 
interim final rule without notice and comment and to make the rule 
effective immediately.
    In 1987, Congress amended the Clean Water Act to provide that 
States must adopt numeric criteria to control the discharge of toxic 
pollutants. Before this requirement was enacted, few States had adopted 
numeric criteria for toxic pollutants and had to rely on ``narrative'' 
criteria (e.g., ``free from toxics in toxic amounts'') to set discharge 
limits for such pollutants. Congress, expressing concern over the 
calculation of discharge limitations for toxics without numeric 
criteria, required States to adopt numeric, pollutant-specific criteria 
for toxic pollutants (56 FR 58423-58424, Nov. 19, 1991).
    Following promulgation of the NTR, EPA continued to evaluate 
available information on metals. EPA held a public meeting of experts 
in which a recommendation was made to express the ambient water 
criteria as dissolved metal. This recommendation and others, were 
noticed for public comment at 58 FR 32131, June 8, 1993. It is EPA's 
judgment that aquatic life criteria for metals, when expressed as 
dissolved metal provide a more accurate measurement of metals 
bioavailability to organisms in the water column than when expressed as 
total recoverable metal. Thus, in some situations, the total 
recoverable metals criteria in the NTR may result in permit limits that 
are more stringent than if the criteria were expressed in a dissolved 
form. As a result, in these situations, permitting authorities in the 
NTR States may be imposing more stringent (and potentially more costly) 
effluent limitations on their dischargers than will be required to meet 
the new dissolved metals aquatic life criteria put in place today.
    EPA considered the impacts of a stay of the current metals criteria 
while it undertook a standard rulemaking (i.e., proposed rule followed 
by a final) to revise the aquatic life metals criteria to express them 
in a dissolved form. However, during the effective period of the stay 
(the interim between proposal and final rule), permitting authorities 
for the NTR States would generally need to use the States' narrative 
criteria (e.g., free from toxics in toxic amounts) to develop permit 
limits for the discharge of toxics. Because the Congressional directive 
is clear that States must have numeric criteria for toxic pollutants, 
EPA rejected this approach in favor of an interim final rule.
    By today's action the Agency upholds the intent of 
Sec. 303(c)(2)(B) of the Clean Water Act and avoids the need for 
permitting authorities to rely on narrative criteria to develop permit 
limits. Further, this interim final rule is a temporary measure. The 
Agency notes that considerable public comment has already been obtained 
on the Metals Policy and the specific criteria being issued in this 
interim final rule. EPA held a meeting with invited experts in January 
1993 in Annapolis, Maryland to further elicit comment on the use of 
dissolved metals for developing national metals criteria. The Agency 
solicited comments on the recommendations made by presenters at that 
meeting in the Federal Register on July 9, 1993 (58 FR 32131). The 
Metals Policy issued in October 1993 has received wide-spread 
distribution and informal response from many interested parties. In 
August 1994, EPA issued a Federal Register notice indicating that the 
Agency was considering the use of the Metals Policy to develop metals 
criteria in the Great Lakes Initiative (59 FR 44678, August 30, 1994) 
and comments were received on this issue. Today's action has the 
additional benefit of the comments received from the August 1994 notice 
on the Great Lakes Initiative.
    EPA therefore concludes that public comment on this interim measure 
is unnecessary because ample comment has already been received on the 
numeric dissolved metals criteria and additional comment is being 
solicited and will be considered before a final rule is issued. 
Further, a public comment process before adopting the new metals 
criteria is contrary to the public interest because: 1) the current 
metals criteria place a potentially unnecessary regulatory burden on 
dischargers in the States covered by this rule, without necessarily 
providing additional protection to aquatic life in the water column and 
2) it is in the public interest for the States to have numeric criteria 
protective of aquatic life.
    Because of the potential adverse effect on public interest noted 
above, the Agency has determined there is good cause for making this 
regulation effective immediately.
J. Regulatory Assessment Requirements

1. Unfunded Mandates Reform Act of 1995

    Section 201 of the Unfunded Mandates Reform Act of 1995 (``Unfunded 
Mandates Act''), signed into law on March 22, 1995, requires each 
Agency, unless prohibited by law, to assess the effects of Federal 
regulation on State, local and tribal governments and the private 
sector under section 202 of the Act. EPA must prepare a written 
statement to accompany any rules where the estimated costs to State, 
local and tribal governments, in the aggregate, or to the private 
sector will be $100 million or more in any one year. Under section 205, 
for rules that require a written statement under section 202, EPA must 
select the most cost-effective and least burdensome alternative that 
achieves the objective of such a rule and that is consistent with 
statutory requirements. Also, for such rules, section 203 requires EPA 
to establish a plan for informing and advising any small governments 
that may be significantly and uniquely affected by the rule.
    EPA estimates that the costs to State, local, and tribal 
governments, or to the private sector, from today's interim final rule 
will not be $100 million or more. EPA has determined that this rule 
should reduce current regulatory requirements imposed by the NTR. By 
promulgating the metals criteria in the NTR as dissolved metals, rather 
than total recoverable, EPA is reducing potential costs to discharge 
permittees and other parties subject to the water quality criteria. 
Therefore, an unfunded mandates statement pursuant to section 202 is 
not necessary.
    While an unfunded mandates statement is not necessary for this 
rule, EPA notes that it has previously considered the costs and 
benefits of promulgating Federal water quality criteria when the Agency 
issued the NTR in 1992. See 57 FR 60903-60909 (December 22, 1992). That 
analysis would continue to be relevant with respect to this issue of 
costs and benefits arising from Federal promulgation of criteria for 
states. Of course, to the extent today's interim final rule is putting 
in place less burdensome [[Page 22235]] requirements than the 1992 
rule, the Agency is reducing any potential costs. It is important to 
note that the Federal criteria in today's rule, as the Federal criteria 
in the 1992 rule, only impose requirements until the States adopt, and 
EPA approves, criteria meeting the requirements of section 303(c)(2)(B) 
of the Clean Water Act. EPA continues to work with the States to assist 
them in adopting their own criteria thereby enabling EPA to withdraw 
the Federal criteria.
    While section 205 of the Unfunded Mandates Act is not applicable to 
today's rule because the rule does not require a written statement 
under section 202, the Agency does believe that today's rule is 
consistent with the intent of section 205. Section 205 directs agencies 
to consider regulatory alternatives and to select the least costly, 
most cost-effective or least burdensome alternative that achieves the 
objectives of the rule. EPA's decision to promulgate metals criteria 
expressed as dissolved rather than total recoverable represents the 
Agency's selection of the least costly, most cost-effective and least 
burdensome alternative for setting metals criteria. The Agency 
addressed this issue in detail in the development of the Great Lakes 
Water Quality Guidance, promulgated on March 13, 1995 (60 FR 15366, 
March 23, 1995). For today's rule the Agency was obligated pursuant to 
section 303 to promulgate water quality criteria for states not in 
compliance with section 303(c)(2)(B). Today's rule achieves that 
objective consistent with the intent of section 205.
    Finally, because today's rule relieves a regulatory requirement, 
EPA does not believe that the rule will establish requirements that 
might significantly or uniquely affect small governments within the 
meaning of section 203. However, the Agency is committed to working 
with affected small governments by providing notice of requirements 
that might potentially affect them, enable them to provide meaningful 
and timely input, and to inform, educate and advise small governments 
on compliance with any requirements. With respect to today's interim 
final rule, representatives of State and local governments participated 
in the development of, and provided comments to the Office of Water's 
current metals policy. The Agency recognizes the importance of 
soliciting the input of small governments and will be available to work 
with them to address any issues related to compliance with today's 
rule.

2. Executive Order 12866

    Under Executive Order 12866 (56 FR 51735, October 4, 1993), the 
Agency must determine whether the regulatory action is ``significant'' 
and therefore subject to all the requirements of the Executive Order 
(i.e., Regulatory Impact Analysis and review by the Office of 
Management and Budget). Under section 3(f), the order defines 
``significant'' as those actions likely to lead to a rule: (1) Having 
an annual effect on the economy of $100 million or more, or adversely 
and materially affecting a sector of the economy, productivity, 
competition, jobs, the environment, public health or safety, or State, 
local, or tribal governments or communities (also known as 
``economically significant''); (2) creating serious inconsistency or 
otherwise interfering with an action taken or planned by another 
agency; (3) materially altering the budgetary impacts of entitlements, 
grants, user fees, or loan programs; or (4) raising novel legal or 
policy issues arising out of legal mandates, the President's 
priorities, or the principles set forth in this order. Pursuant to the 
terms of this order, EPA has determined that this interim final rule 
would not be ``significant''.

3. Presidential Review of the Code of Federal Regulations

    On February 22, 1995, President Clinton announced a review of the 
Code of Federal Regulations by all Federal agencies. The objective of 
the review is to: eliminate obsolete regulations, withdraw outdated or 
superseded regulations, propose modifications to simplify or reduce 
burden, and to identify legislation for needed change. Today's rule, 
revising the NTR, is consistent with the review announced by the 
President. EPA has reviewed the NTR (40 CFR 131.36) and determined that 
the use of dissolved metals criteria in the NTR States, for the metals 
listed in this rule, should reduce potential regulatory burden.

4. Regulatory Flexibility Act

    The Regulatory Flexibility Act (5 U.S.C. 601, et seq., Pub. L. 96-
354) requires EPA to assess whether its regulations create a 
disproportionate effect on small entities. EPA discussed in the NTR 
rulemaking (December 22, 1992, 57 FR 60909), the potential effects of 
the rulemaking on small entities. The Agency concluded that the 
rulemaking would not result in a significant impact on small entities 
and a final regulatory flexibility analysis was not required.
    Because the potential impact on small entities as a result of this 
interim final rule revision will be less burdensome on small entities 
than the original rule, EPA, based on the same factors discussed in the 
previous final rulemaking, continues to conclude this action will not 
result in a significant impact on small entities.

5. Paperwork Reduction Act

    This interim final rule places no information collection activities 
on the affected States and therefore no information collection 
requirement will be submitted to the Office of Management and Budget 
for review in compliance with the Paperwork Reduction Act, 44 U.S.C. 
3501 et seq.
List of Subjects in 40 CFR Part 131

    Environmental Protection, Water pollution control, Water quality 
standards, Toxic pollutants.

    Dated: April 14, 1995.
Carol Browner,
Administrator.
    For the reasons set out in the preamble, title 40, chapter I part 
131 of the Code of Federal Regulations is 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.

    2. Section 131.36 is amended by revising entries 2, 4, 
5a,5b,6,7,8,9,10,11, and 13 of the table at paragraph (b)(1), revising 
footnotes ``e'' and ``l'' adding footnotes ``o'' and ``p'' to the table 
in paragraph (b)(1), removing the ``Note to paragraph (b)(1)'', 
revising paragraph (b)(2) and by revising the first two sentences of 
paragraph (c)(4)(iii) to read as follows:


Sec. 131.36  Toxics criteria for those States not complying with Clean 
Water Act Section 303(c)(2)(B).

* * * * *

[[Page 22236]]

    (b)(1) EPA's Section 304(a) Criteria for Priority Toxic Pollutants.

----------------------------------------------------------------------------------------------------------------
                 A                              B                         C                         D           
----------------------------------------------------------------------------------------------------------------
                                           Freshwater                 Saltwater          Human health (10<SUP>-6 risk
                                   ----------------------------------------------------     for carcinogens)    
                                                                                       -------------------------
                                      Criteria     Criteria     Criteria     Criteria      For consumption of:  
     (#) Compound         CAS N.      Maximum     Continuous    Maximum     Continuous -------------------------
                                    Conc.<SUP>d (ug/  Conc.<SUP>d (ug/  Conc.<SUP>d (ug/  Conc.<SUP>d (ug/    Water &     Organisms 
                                       L) B1        L) B2        L) C1        L) C2      Organisms   only (ug/L)
                                                                                         (ug/L) D1        D2    
----------------------------------------------------------------------------------------------------------------
                                                                                                                
                                                                                                                
 *                  *                  *                  *                  *                  *               
                                                          *                                                     
2 Arsenic............      7440382         <SUP>m360         <SUP>m190          <SUP>m69          <SUP>m36   <SUP>a,b,c0.018             
                                                                                              a,b,c    <SUP>a,b,c0.14
                                                                                                                
 *                  *                  *                  *                  *                  *               
                                                          *                                                     
4 Cadmium............      7440439         <SUP>e3.7         <SUP>e1.0          <SUP>m42         <SUP>m9.3          (<SUP>n)          (<SUP>n)
5a Chromium (III)....     16065831         <SUP>e550         <SUP>e180  <SUP>...........  <SUP>...........          (<SUP>n)          (<SUP>n)
b Chromium (VI)......     18540299          <SUP>m15          <SUP>m10        <SUP>m1100          <SUP>m50          (<SUP>n)          (<SUP>n)
6 Copper.............      7440508          17<SUP>e          11<SUP>e        <SUP>m 2.4        <SUP>m <SUP>2.4  <SUP>..<SUP>.........  <SUP>..<SUP>.........
7 Lead...............      7439921          <SUP>e65         <SUP>e2.5         <SUP>m210         <SUP>m8.1          (<SUP>n)          (<SUP>n)
8 Mercury............      7439976         <SUP>m2.1     <SUP>i,p0.012         <SUP>m1.8     <SUP>i,p0.025         0.14         0.15
9 Nickel.............      7440020        <SUP>e1400         <SUP>e160          <SUP>m74         <SUP>m8.2         <SUP>a610        <SUP>a4600
10 Selenium..........      7782492          <SUP>p20         <SUP>p5.0         <SUP>m290          <SUP>m71          (<SUP>n)          (<SUP>n)
11 Silver............      7440224         <SUP>e3.4         <SUP>m1.9                                                    
                                                                                                                
 *                  *                  *                  *                  *                  *               
                                                          *                                                     
13 Zinc..............      7440666         <SUP>e110         <SUP>e100          <SUP>m90          <SUP>m81                          
                                                                                                                
*                  *                  *                  *                  *                  *                
                                                        *                                                       
----------------------------------------------------------------------------------------------------------------
Footnotes:                                                                                                      
a. Criteria revised to reflect current agency q<INF>1* or RfD, as contained in the Integrated Risk Information System
  (IRIS). The fish tissue bioconcentration factor (BCF) from the 1980 criteria documents was retained in all    
  cases.                                                                                                        
b. The criteria refers to the inorganic form only.                                                              
c. Criteria in the matrix based on carcinogenicity (10<SUP>-6 risk). For a risk level of 10<SUP>-5, move the decimal point
  in the matrix value one place to the right.                                                                   
d. Criteria Maximum Concentration (CMC) = the highest concentration of a pollutant to which aquatic life can be 
  exposed for a short period of time (1-hour average) without deleterious effects. Criteria Continuous          
  Concentration (CCC) = 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 = micrograms per liter                     
e. Freshwater aquatic life criteria for these metals are expressed as a function of total hardness (mg/L as     
  CaC0<INF>3), the pollutant's water effect ratio (WER) as defined in Sec. 131.36(c) and multiplied by an appropriate
  dissolved conversion factor as defined in Sec. 131.36(b)(2). For comparative purposes, the values displayed in
  this matrix are shown as dissolved metal and correspond to a total hardness of 100 mg/L and a water effect    
  ratio of 1.0.                                                                                                 
*                  *                  *                  *                  *                  *                
    *                                                                                                           
i. If the CCC for total mercury exceeds 0.012 ug/l more than once in a 3-year period in the ambient water, the  
  edible portion of aquatic species of concern must be analyzed to determine whether the concentration of methyl
  mercury exceeds the FDA action level (1.0 mg/kg). If the FDA action level is exceeded, the State must notify  
  the appropriate EPA Regional Administrator, initiate a revision of its mercury criterion in its water quality 
  standards so as to protect designated uses, and take other appropriate action such as issuance of a fish      
  consumption advisory for the affected area.                                                                   
*                  *                  *                  *                  *                  *                
    *                                                                                                           
l. [Reserved: this letter not used as a footnote].                                                              
m. Criteria for these metals are expressed as a function of the water effect ratio, WER, as defined in 40 CFR   
  131.36 (c).                                                                                                   
                                                                                                                
CMC=column B1 or C1 value x WER                                                                                 
CCC=column B2 or C2 value x WER                                                                                 
n. EPA is not promulgating human health criteria for this contaminant. However, permit authorities should       
  address this contaminant in NPDES permit actions using the State's existing narrative criteria for toxics.    
o. [Reserved: This letter not used as a footnote].                                                              
p. Criterion expressed as total recoverable.                                                                    
*                  *                  *                  *                  *                  *                
    *                                                                                                           

    (2) Factors for Calculating Hardness-Dependent, Freshwater Metals 
Criteria

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

                                                                                                                
[[Page 22237]]
----------------------------------------------------------------------------------------------------------------
                                                                                          Freshwater conversion 
                                                                                                 factors        
               Metal                     m<INF>A           b<INF>A           m<INF>C           b<INF>C     -------------------------
                                                                                           Acute       Chronic  
----------------------------------------------------------------------------------------------------------------
Cadmium...........................        1.128       -3.828       0.7852       -3.490       <SUP>a0.944       <SUP>a0.909
Chromium (III)....................       0.8190        3.688       0.8190        1.561        0.316        0.860
Copper............................       0.9422       -1.464       0.8545       -1.465        0.960        0.960
Lead..............................        1.273       -1.460        1.273       -4.705       <SUP>a0.791       <INF>a0.791
Nickel............................       0.8460       3.3612       0.8460       1.1645        0.998        0.997
Silver............................         1.72        -6.52         <SUP>bN/A         <SUP>bN/A         0.85         <SUP>bN/A
Zinc..............................       0.8473       0.8604       0.8473       0.7614        0.978       0.986 
----------------------------------------------------------------------------------------------------------------
Note to table: The term ``exp'' represents the base e exponential function.                                     
Footnotes to table:                                                                                             
<SUP>aThe freshwater conversion factors (CF) for cadmium and lead are hardness-dependent and can be calculated for   
  any hardness [see limitations in Sec. 131.36(c)(4)] 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)]                                               
                                                                                                                
 <SUP>bNo chronic criteria are available for silver.                                                                 

  (c) * * *
    (4) * * *
    (iii) Except where otherwise noted, the criteria for metals 
(compounds #2, #4-# 11, and #13, in paragraph (b) of this section) are 
expressed as dissolved metal. For purposes of calculating aquatic life 
criteria for metals from the equations in footnote m. in the criteria 
matrix in paragraph (b)(1) of this section and the equations in 
paragraphs (b)(2) of this section, the water-effect ratio is computed 
as a specific pollutant's acute or chronic toxicity values measured in 
water from the site covered by the standard, divided by the respective 
acute or chronic toxicity value in laboratory dilution water. * * *
* * * * *
[FR Doc. 95-10148 Filed 5-3-95; 8:45 am]
BILLING CODE 6560-50-P