[Federal Register Volume 64, Number 109 (Tuesday, June 8, 1999)]
[Rules and Regulations]
[Pages 30417-30434]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-14220]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 136

[FRL-6354-3]
RIN 2040-AD07


Guidelines Establishing Test Procedures for the Analysis of 
Pollutants; Measurement of Mercury in Water (EPA Method 1631, Revision 
B); Final Rule

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This final regulation amends the ``Guidelines Establishing 
Test Procedures for the Analysis of Pollutants'' under section 304(h) 
of the Clean Water Act by adding EPA Method 1631, Revision B: Mercury 
in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic 
Fluorescence Spectrometry. EPA Method 1631 measures mercury at the low 
levels associated with ambient water quality criteria (WQC). EPA has 
promulgated WQC for mercury at 12 parts-per-trillion (ppt) in the 
National Toxics Rule, and published a criterion for mercury at 1.3 ppt 
in the Water Quality Guidance for the Great Lakes System. The version 
of Method 1631 promulgated today includes changes to the method based 
on public comments at proposal (63 FR 28867, May 26, 1998). These 
changes increase measurement reliability at WQC levels. EPA recommends 
the use of clean sampling and laboratory techniques in conjunction with 
EPA Method 1631 to preclude contamination

[[Page 30418]]

at the low ppt levels necessary for mercury determinations. EPA has 
published guidance documents on sampling and clean rooms for trace 
metals, including mercury.

EFFECTIVE DATE: This regulation is effective July 8, 1999. For judicial 
review purposes, this final rule is promulgated as of 1:00 p.m. Eastern 
Standard Time on June 22, 1999 in accordance with 40 CFR 23.7.
    The incorporation by reference of EPA Method 1631 is approved by 
the Director of the Federal Register July 8, 1999.

ADDRESSES: Copies of the public comments received, EPA responses, and 
all other supporting documents (including references included in this 
notice) are available for review at the U.S. Environmental Protection 
Agency, Water Docket, 401 M Street SW, Washington, DC 20460. For access 
to docket materials, call 202/260-3027 on Monday through Friday, 
excluding Federal holidays, between 9 a.m. and 3:30 p.m. Eastern 
Standard Time for an appointment.
    Copies of EPA Method 1631 are available from the National Technical 
Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 
22161, (703) 605-6000 or (800) 553-6847. The NTIS publication number is 
PB99-131989.
    An electronic version of EPA Method 1631 also is available via the 
Internet at http://www.epa.gov/OST/Methods.

FOR FURTHER INFORMATION CONTACT: For information regarding EPA Method 
1631 contact Maria Gomez-Taylor, Ph.D., Engineering and Analysis 
Division (4303), USEPA Office of Science and Technology, 401 M Street, 
SW, Washington, DC 20460; or call 202/260-1639.

SUPPLEMENTARY INFORMATION:

Potentially Regulated Entities

    EPA Regions, as well as States, Territories and Tribes authorized 
to implement the National Pollutant Discharge Elimination System 
(NPDES) program, issue permits that comply with the technology-based 
and water quality-based requirements of the Clean Water Act. In doing 
so, the NPDES permitting authority, including authorized States, 
Territories, and Tribes, make a number of discretionary choices 
associated with permit writing, including the selection of pollutants 
to be measured and, in many cases, limited in permits. If EPA has 
``approved'' standardized testing procedures (i.e., promulgated through 
rulemaking) for a given pollutant, the NPDES permit must include one of 
the approved testing procedures or an approved alternate test 
procedure. Regulatory entities may, at their discretion, require use of 
this method in their permits. Therefore, entities with NPDES permits 
could be affected by the standardization of testing procedures in this 
rulemaking, because NPDES permits may incorporate the testing 
procedures in today's rulemaking. In addition, when a State, Territory, 
or authorized Tribe provides certification of federal licenses under 
Clean Water Act section 401, States, Territories and Tribes are 
directed to use the standardized testing procedures. Categories and 
entities that may ultimately be affected include:

------------------------------------------------------------------------
                                             Examples of potentially
                Category                        regulated entities
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Regional, State and Territorial          States, Territories, and Tribes
 Governments and Indian Tribes.           authorized to administer the
                                          NPDES permitting program;
                                          States, Territories, and
                                          Tribes providing certification
                                          under Clean Water Act section
                                          401; Governmental NPDES
                                          permittees.
Industry...............................  Industrial NPDES permittees.
Municipalities.........................  Publicly-owned treatment works
                                          with NPDES permits.
------------------------------------------------------------------------

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

Outline of Preamble

I. Authority
II. Background
III. Summary of Final Rule
    A. Introduction
    B. Summary of EPA Method 1631
    C. Sample Contamination
    D. Quality Control
    E. Performance-Based Measurement System
IV. Changes to EPA Method 1631 Since Proposal
    A. Holding Time Change
    B. Performance Criteria Change
    C. Reporting Requirements Changes
    1. Reporting of data that failed to meet QC acceptance criteria
    2. Reporting of blank results
    3. Reporting laboratory-specific MDLs and MLs
D. Other Changes and Improvements
    1. Changes to method implementation
    2. Corrections to method
    3. Clarifying statements
    4. Additions to health and safety monitoring and waste 
management
V. Public Participation and Response to Comments
    1. Support for EPA Method 1631
    2. Practicality and cost
    3. EPA Method 1631 represents a significant regulatory action
    4. Regulatory implications
    5. Retention of approved methods and approval of additional 
methods
    6. Application to wastewater matrices
    7. Detection and quantitation
    8. Clean techniques
    9. Corrections to statements in proposal
    10. Quality control
    11. Blanks and contamination
    12. Validation study
    13. Technical details of EPA Method 1631
    14. Miscellaneous
VI. Regulatory Requirements
    A. Executive Order 12866
    B. Unfunded Mandates Reform Act
    C. Regulatory Flexibility Act
    D. Paperwork Reduction Act
    E. Submission to Congress and the General Accounting Office
    F. National Technology Transfer and Advancement Act
    G. Executive Order 13045
    H. Executive Order 12875
    I. Executive Order 13084

I. Authority

    Today's regulation is being promulgated pursuant to the authority 
of sections 301, 304(h), and 501(a) of the Clean Water Act (CWA), 33 
U.S.C. 1314(h), 1361(a) (the ``Act''). Section 301 of the Act prohibits 
the discharge of any pollutant into navigable waters unless the 
discharge complies with a National Pollutant Discharge Elimination 
System (NPDES) permit issued under section 402 of the Act. Section 
304(h) of the Act requires the Administrator of the EPA to ``promulgate 
guidelines establishing test procedures for the analysis of pollutants 
that shall include the factors which must be provided in any 
certification pursuant to section 401 of this Act or permit 
applications pursuant to section 402 of this Act.'' Section 501(a) of 
the Act authorizes the Administrator to

[[Page 30419]]

``prescribe such regulations as are necessary to carry out his function 
under this Act.'' EPA publishes CWA analytical method regulations at 40 
CFR part 136. The Administrator also has made these test procedures 
applicable to monitoring and reporting of NPDES permits (40 CFR part 
122, Secs. 122.21, 122.41, 122.44, and 123.25), and implementation of 
the pretreatment standards issued under section 307 of the Act (40 CFR 
part 403, Secs. 403.10 and 402.12).

II. Background

    The details of EPA Method 1631 and its use in mercury 
determinations were given at proposal on May 26, 1998 (63 FR 28867). On 
March 5, 1999, EPA published a notice of data availability (NODA) with 
results from additional studies of municipal and industrial effluents 
using EPA Method 1631 (64 FR 10596). EPA conducted the additional 
studies in order to better respond to comments received on the May 26, 
1998 proposal.

III. Summary of Final Rule

A. Introduction

    Today's action makes available at 40 CFR part 136 an additional 
test procedure for measurement of mercury in aqueous samples. This 
rulemaking does not repeal any of the currently approved methods that 
measure mercury. For an NPDES permit, the permitting authority should 
decide the appropriate method based on the circumstances of the 
particular water sample measured. Use of EPA Method 1631 may be 
specified by the permitting authority when a permit is modified or 
reissued.
    EPA does not intend for Method 1631 to be a de facto replacement 
for Method 245.1 or any of the other existing EPA-approved methods for 
measurement of mercury. EPA intends that permit writers specify the use 
of Method 1631 when measurement at very low levels is required, for 
example, to determine compliance with water quality-based effluent 
limitations duly established at very low levels.

B. Summary of EPA Method 1631

    EPA Method 1631 has four procedural components: sample 
pretreatment; purge and trap; desorption; and detection by atomic 
fluorescence. In the sample pretreatment step, bromine monochloride 
(BrCl) is added to the sample to oxidize all forms of mercury to 
Hg(II). After oxidation, the sample is sequentially prereduced with 
NH2OHHCl to destroy free 
halogens, then reduced with SnCl2 
to convert Hg(II) to volatile Hg(0). The Hg(0) is purged from the 
aqueous solution with nitrogen onto a gold-coated sand trap. The 
trapped mercury is thermally desorbed from the gold trap into a flowing 
gas stream into the cell of a cold-vapor atomic fluorescence 
spectrometer. Quality is assured through calibration and testing of the 
oxidation, purging, and detection systems.

C. Sample Contamination

    Trace levels of metals are ubiquitous in the environment. 
Therefore, the determination of trace metals at the levels of interest 
for water quality criteria necessitates the use of clean sample 
handling techniques to avoid ``false positive'' test results due to 
contamination in the course of sample collection, handling, or 
analysis. EPA has distributed several guidance documents that are 
designed to ensure that data results from the measurement of metals in 
aqueous test samples accurately reflect actual environmental levels. 
The guidance documents include: Method 1669: Sampling Ambient Water for 
Trace Metals at EPA Water Quality Criteria Levels (Sampling Guidance), 
EPA-821-R-96-001, July 1996; Guidance on Establishing Trace Metals 
Clean Rooms in Existing Facilities, EPA-821-B-96-001, January 1996; and 
Guidance on Documentation and Evaluation of Trace Metals Data Collected 
for Clean Water Act Compliance Monitoring, EPA-821-B-96-004, July 1996. 
The most serious problem faced by laboratories conducting metals 
analyses at these very low levels is the potential for sample 
contamination during sample collection and handling. Sample 
contamination with mercury is particularly difficult to control because 
of its ubiquity in the environment. For example, commonly used 
polyethylene sample containers are unacceptable for sample storage 
because atmospheric mercury may diffuse through the walls of the 
container causing sample contamination. The Sampling Guidance details 
rigorous sample handling and quality control (QC) procedures to assure 
that reliable data are obtained for mercury at the levels of interest 
for water quality criteria. EPA recommends that the procedures 
described in the Sampling Guidance be followed when performing low 
level, trace metals analyses and has incorporated certain essential 
elements of the Guidance in the method.

D. Quality Control

    EPA Method 1631 contains all of the standardized QC tests proposed 
in EPA's streamlining initiative (62 FR 14976, March 28, 1997) and used 
in test procedures in 40 CFR part 136, appendix A. Today's rule 
requires an initial demonstration of laboratory capability which 
consists of: (1) A method detection limit (MDL) study to demonstrate 
that the laboratory is able to achieve the MDL and minimum level of 
quantification (ML) specified in EPA Method 1631; and (2) an initial 
precision and recovery (IPR) test, consisting of analyses of four 
reagent water samples spiked with mercury, to demonstrate the 
laboratory's ability to generate acceptable precision and recovery.
    Today's rule also requires ongoing QC tests for each analytical 
batch, (i.e., a set of 20 samples or less pretreated at the same time):
     Verification of calibration of the purge and trap and 
atomic fluorescence systems to assure that instrument response has not 
deviated significantly from the instrument response obtained during 
calibration.
     Analysis of a matrix spike (MS) and matrix spike duplicate 
(MSD) to demonstrate method accuracy and precision and to monitor 
matrix interferences.
     Analysis of reagent and bubbler blanks to demonstrate 
freedom from contamination.
     Analysis of a quality control sample (QCS) and ongoing 
precision and recovery (OPR) samples to demonstrate that the method 
remains under control.
    EPA Method 1631 contains QC acceptance criteria for all QC tests. 
Compliance with these criteria will allow a data user to evaluate the 
quality of the results. These QC acceptance criteria will increase the 
reliability of results and provide a means for laboratories and data 
users to monitor analytical performance, thereby providing a basis for 
sound, defensible data.

E. Performance Based Measurement System

    On March 28, 1997, EPA proposed a rule (62 FR 14976) to streamline 
approval procedures and use of analytic methods in water programs 
through implementation of a performance-based approach to environmental 
measurements. On October 7, 1997, EPA published a document of the 
Agency's intent to implement a Performance Based Measurement System 
(PBMS) in all media programs to the extent feasible (62 FR 52098). 
EPA's water program offices are developing plans to implement PBMS. EPA 
anticipates that the final rule to implement PBMS in water programs 
will be published in 1999 based on the March 28, 1997

[[Page 30420]]

proposed rule. Consistent with Agency PBMS implementation plans, EPA 
Method 1631 incorporates QA and QC acceptance criteria to serve as a 
basis for assessment of method performance. When PBMS is in place, EPA 
Method 1631 would serve as a reference method for demonstrating 
equivalency when modifications are made.
    EPA Method 1631 also employs a performance-based approach to the 
sample preparation and trapping systems. Analysts are allowed to modify 
the sample preparation and trapping aspects of the method provided all 
the specified performance criteria are demonstrated and documented. The 
method also allows the use of alternate reagents and hardware provided 
that the analyst demonstrates equivalent or superior performance and 
meets all QC acceptance criteria.
    Demonstrating equivalency involves two sets of tests, one set with 
reference standards and the other with the sample matrix. The 
equivalency procedures include performance of the IPR test using 
reference standards to demonstrate that the results produced with the 
modified procedure would meet or exceed the QC acceptance criteria in 
EPA Method 1631. In addition, if the detection limit would be affected 
by a modification, performance of an MDL study is required to 
demonstrate that the modified procedure could achieve an MDL less than 
or equal to the MDL in EPA Method 1631 or, for those instances in which 
the regulatory compliance limit is greater than the ML in the method, 
one-third the regulatory compliance limit. For a discussion of these 
levels, see EPA Method 1631 or the March 28, 1997 proposed rule at 62 
FR 14976.

IV. Changes to EPA Method 1631 Since Proposal

    The Agency has revised EPA Method 1631, Revision A based on 
comments received on the proposal (63 FR 28868, May 26, 1998) and the 
NODA (64 FR 10596; March 5, 1999). The significant modifications in EPA 
Method 1631, Revision B are the change of the sample holding time (from 
6 months to 28 days), the change of the MS/MSD performance criteria 
(for recovery from 75-125 percent to 71-125 percent recovery), and a 
change in reporting requirements.

A. Holding Time Change

    EPA proposed the 6 month holding time for preserved aqueous samples 
to be analyzed by EPA Method 1631. Because the 6 month holding time was 
not evaluated in the method validation study supporting the proposal, 
EPA requested data that would support the 6 month holding time. Data 
were not available. Therefore, in the version of EPA Method 1631 being 
approved for use today, EPA has set the holding time to 28 days, the 
prescribed holding time listed in Table II at 40 CFR part 136.

B. Performance Criteria Change

    The MS/MSD recovery limits in the proposed version of EPA Method 
1631 were 75-125 percent. The interlaboratory method validation study 
produced MS/MSD limits of 71-119 percent. In response to comments on 
the proposal, EPA acknowledges that the lower limit produced in the 
interlaboratory study is more appropriate and has changed this limit to 
71 percent in the version of EPA Method 1631 approved for use today.

C. Reporting Requirements Change

1. Reporting of Data That Failed To Meet QC Acceptance Criteria
    In order to clarify the Agency's intent regarding data that do not 
meet the method QC acceptance criteria or that indicate the analytical 
system is not in control, EPA has adopted suggestions from commenters 
that these data should not be reported or otherwise used for permitting 
or regulatory compliance purposes. This modification addresses concerns 
that regulated entities could be adversely affected by data not meeting 
performance criteria, for example, via compliance monitoring. EPA also 
has added a statement to section 13.2 of the method that any decision 
not to report data from an analytical system that is out of control 
does not provide relief from a permit's underlying requirement to 
submit timely reports.
2. Reporting of Blank Results
    In today's rule, EPA has expanded reporting of blank results to 
include reagent blanks and field blanks so that a regulatory authority 
may consider field blank contamination in any compliance determination. 
To facilitate assessment of the presence and extent of contamination, 
the Agency has revised EPA Method 1631 to require reporting of the 
mercury concentration in field blanks as well as in reagent blanks. 
Today's rule, however, does not require blank subtraction. Regulatory 
authorities or other data users may subtract the concentration of 
mercury in field blanks or reagent blanks if subtraction is warranted 
on a case-by-case basis. Today's rule does nothing, however, to 
preclude the reporting of blank-subtracted results in addition to the 
separate reporting of results from samples and from blanks.
3. Reporting Laboratory-Specific MDLS and MLS
    EPA has removed the option for laboratories to calculate their own 
lower MDLs and MLs in the version of EPA Method 1631 being approved for 
use today. EPA believes this will avoid confusion and preclude lower 
MDLs and MLs from being used for NPDES permitting or regulatory 
compliance determinations.

D. Other Changes and Improvements

1. Changes To Method Implementation
    Minor technical improvements were made to EPA Method 1631 to 
clarify method implementation. Changes and improvements include:
     Revision to sections 7.9, 7.10 and 10.1.1.2 to include two 
working standards (0.10 ng/mL and 10.0 ng/mL) in order to correct 
inaccurate standard concentration levels.
     Language changes in sections 4.4.1 and 9.3.4.1 to address 
iodide interferences that have been identified and assessed since 
proposal. This modification required the addition of a reference 
supporting the handling of iodide interferences. The additional 
reference has been added to EPA Method 1631 as Reference 10.
     Revisions to sections 9.4.2.2 and 11.1.1.2 to include a 
requirement that a reagent blank include the same amount of reagent as 
the sample being analyzed.
     Revisions to section 11.1.1.2 to include recommendations 
to assure that complete oxidation has occurred.
     Where appropriate, the word ``analyst'' was changed to 
``laboratory'' to acknowledge that various sections of EPA Method 1631 
may be performed by different analysts in the same laboratory.
2. Corrections To Method
    Minor changes were made to correct typographical and information 
errors. Nearly all of the corrections are the result of comments and 
include:
     In section 9.1.2.1, ``less than'' was changed to ``less 
than or equal to.'' A method modification must achieve an MDL ``less 
than or equal to'' one-third the compliance limit or the MDL.
     In section 12.4.1, > 0.2 ng/L has been corrected to < 0.2 
ng/L.
     In Table 2, (s) has been corrected to RSD for precision.
     In Table 1, the lowest ambient water quality criterion has 
been corrected from 1.8 ng/L (human health criterion) to 1.3 ng/L 
(wildlife criterion).

[[Page 30421]]

The lowest WQC for the Great Lakes is 1.3 ng/L, the criterion for 
wildlife protection (see Table 4 to 40 CFR part 132).
     In section 4.2, Reference 5 has been changed to Reference 
9, which is a paper discussing contamination of samples by dental work 
containing mercury amalgam fittings.
     References 10 through 20 in the proposed version of EPA 
Method 1631 have been changed to References 11 through 21 in the final 
version to include the addition of a new Reference 10 addressing 
handling of samples containing iodide interferences.
3. Clarifying Statements
    As a result of comments:
     In section 4.3.8.5, a statement was added to clarify that 
reagents can be a source of contamination.
     Sections 4.3.8.2 and 5.3 were modified to clarify the 
meaning of ``high'' concentration of mercury and to caution that 
samples containing mercury concentrations greater than 100 ng/L should 
be diluted prior to bringing them into the clean room or laboratory 
dedicated to processing trace metals samples and that samples 
containing
 g/L concentrations of mercury should be treated as hazardous.
4. Additions To Health and Safety Monitoring and Waste Management
    Today's version of EPA Method 1631 includes two additions made to 
address and clarify health and safety monitoring and waste management.
     In section 5.2, EPA added a recommendation that personal 
hygiene monitoring should be performed using Occupational Safety and 
Health Administration (OSHA) or National Institute of Occupational 
Safety and Health (NIOSH) approved personal hygiene monitoring methods.
     In section 15.1, a reference was added to address waste 
management techniques: Environmental Management Guide for Small 
Laboratories (EPA 233-B-98-001). None of the changes or improvements to 
the Method discussed above warrant re-proposal because these changes 
merely respond to public comment to clarify, correct minor errors, or 
otherwise improve the Method. None of these changes impair method 
performance or reliability.

V. Public Participation and Response to Comments

    The Agency proposed EPA Method 1631 (``Method 1631''; or ``the 
Method'') on May 26, 1998 (63 FR 28867). The comment period closed on 
July 27, 1998. In addition to providing notice of the Method, the 
proposal also solicited information and data that might be relevant to 
the Agency's decisionmaking. EPA both received information and data and 
developed additional data confirming the proposal. EPA issued a notice 
of data availability (NODA) and request for comment on these data (64 
FR 10596; March 5, 1999). The NODA comment period closed on April 5, 
1999. During the NODA comment period, EPA again solicited additional 
data and information on EPA Method 1631.
    EPA received more than 500 detailed comments from approximately 30 
commenters. Comments ranged from praise and support for EPA Method 1631 
to concern about the possible setting of compliance limits at the MDL 
or ML and suggestions for improving the technical details of the 
method. EPA appreciates the constructive comments and suggestions and 
believes that today's version of EPA Method 1631 will provide reliable 
data for compliance monitoring. A summary of the significant comments 
is presented below, followed by EPA's response. See the Docket for a 
complete summary of the detailed comments and more extensive responses.
    A significant report received during the comment period was 
provided by the Department of Environmental Protection (DEP) in the 
State of Maine titled: ``Mercury in Wastewater: Discharges to the 
Waters of the State'' (the ``Maine Report''). The Maine Report gives 
details and results of analysis of 104 ambient water samples and more 
than 150 wastewater samples (primarily effluents) using the proposed 
version of EPA Method 1631. The Maine Report is exemplary in that it 
allowed Maine's DEP to assess the presence and concentration of mercury 
Statewide, and will allow the State of Maine to focus its resources on 
problem areas within the State. The Maine Report is also significant 
because it provided a comprehensive ``real world'' assessment of the 
measurement capability of EPA Method 1631. The Maine Report 
demonstrates that EPA Method 1631 can be applied successfully to 
determination of mercury in a wide variety of effluents and ambient 
waters. Of particular interest is that, of 104 ambient water samples 
tested, no sample contained mercury at a concentration greater than 7 
ng/L. Of the more than 100 effluent samples tested, only one contained 
mercury above the 200 ng/L level that previously approved methods for 
mercury could have measured. EPA has placed a copy of the Maine Report 
in the Docket for today's final rule. EPA recommends that all persons 
interested in making reliable mercury measurements in ambient water and 
discharges read the Maine Report. EPA publicly thanks the State of 
Maine and particularly the Department of Environmental Protection for 
its contribution. Comments and responses are organized and presented by 
subject area.
1. Support for EPA Method 1631
    Comment: Commenters strongly support the need to reliably measure 
mercury levels in ambient waters. The method is technically sound and 
the chemistry behind the method is superb. The Agency should move 
aggressively to implement this method. Permitting authorities and 
others should take the necessary steps to see its adoption and use. EPA 
Method 1631 will: (1) Allow gathering of the type of information 
crucial to understanding mercury in the environment; (2) allow better 
analytical information on the levels of mercury in various waters to 
help decide if and where source reduction efforts would be most 
effective; (3) allow facilities to better assess actual discharges and 
progress in reducing mercury in effluents; (4) allow permitting 
authorities to establish appropriate limits based on ecological or 
human health endpoints, rather than being limited by the less-sensitive 
analytical techniques routinely utilized; (5) allow agencies to better 
monitor response of ambient waters to mercury reduction initiatives; 
(6) be useful for situations in which an authority or facility believes 
that results obtained with currently approved methods do not reflect 
actual levels because of contamination during sample collection, 
handling, and analysis; and (7) allow the State of Wisconsin to meet 
the recommendations of the ``Wisconsin Strategy for Regulating Mercury 
in Wastewater.'' The Wisconsin strategy recommends development of 
better analytical capability to adequately quantify the level of 
mercury at effluent levels that have the potential to cause 
environmental degradation.
    Response: EPA appreciates the support and, in particular, the 
recognition that a method for measuring mercury at ambient water 
quality criteria levels is overdue, that the method is based on sound 
science, and that EPA Method 1631 will protect dischargers from false 
reports that mercury is present in an effluent when, in fact, 
inadequate sampling and laboratory procedures accounted for the mercury 
measured in the sample.

[[Page 30422]]

2. Practicality and Cost
Impractical and Costly
    Comment: The required use of EPA Method 1631 would impose an 
economic burden on industry, would force purchase of expensive new 
equipment, and would require a significant increase in operating 
expenses. The cost of a Class 100 clean room is $50,000-$200,000. The 
analytical equipment will cost $10,000-$45,000. Fluoropolymer bottles 
will cost an estimated $7,200. The bottle cleaning protocol would 
require dedicated laboratory space and staff. Additional cost will be 
incurred for training.
    Response: Not every facility will need to create a clean room and 
bottle cleaning capacity, because commercial laboratories are available 
and can supply clean bottles. In a study conducted by Ford Motor 
Company, the cost per sample analysis was in the range of $50-$80. 
EPA's experience is that costs per sample typically range between $50 
to $110. EPA does not believe that this cost is unreasonable. If a 
facility desires to establish a laboratory for analysis using EPA 
Method 1631, however, EPA has provided guidance for establishment of 
``clean spaces'' that will minimize costs in establishing a ``clean'' 
facility (see References 6 and 7 in Method 1631).
Lack of Laboratory Capability
    Comment: Relatively few laboratories nationwide currently have the 
expertise and infrastructure to conduct analysis using this Method.
    Response: Not every laboratory will need to establish the 
capability to conduct EPA Method 1631. Analytical costs are likely to 
decrease as demand for and use of the Method increases. Today more than 
ever, laboratories and other businesses respond rapidly to new business 
opportunities. Therefore, the Agency anticipates that capacity will 
develop rapidly as the demand increases for analyses by EPA Method 
1631.
Sampling With EPA Method 1669
    Comment: Required use of the radical field sampling procedures in 
EPA Sampling Method 1669 to support EPA Method 1631 would significantly 
increase cost and staff necessary to sample for mercury analysis alone. 
One additional sampling person (for clean hands/dirty hands) and 
ultraclean sampling protocols will cost approximately $34,000.
    Response: Once sampling personnel become familiar with the ``clean 
hands/dirty hands'' technique and procedures recommended in EPA Methods 
1631 and 1669, sampling for mercury can proceed quickly and 
efficiently. EPA does not believe that full-time sampling personnel 
will be needed. EPA anticipates that samples may need to be collected 
monthly, quarterly, or yearly, depending on the facility and whether 
mercury is measured at levels of concern. Therefore, the actual 
incremental cost for collection of samples using the techniques 
suggested in EPA Method 1669 will be small.
3. EPA Method 1631 Represents a Significant Regulatory Action
Significant Regulatory Action Under Executive Order 12866
    Comment: The proposed rule is a ``Significant Regulatory Action'' 
under Executive Order 12866 (58 FR 51735, Oct. 4, 1993).
    Response: It has been determined that this rule is a significant 
regulatory action and was, therefore, reviewed by the Office of 
Management and Budget (OMB).
Cost Increase Stated in Great Lakes Guidance
    Comment: EPA acknowledged in Table 5-13 of Assessment of Compliance 
Costs Resulting from Implementation of the Final Great Lakes Water 
Quality Guidance (the ``Assessment Document'') that the annual cost 
could increase by $569.8 million if future MDLs became 10 times lower 
and could increase by $882.5 million if future MDLs became 100 times 
lower. EPA Method 1631 lists an MDL 1000 times lower. This rule should 
be subject to OMB review.
    Response: The estimated compliance cost increases in the Assessment 
Document referred to future MDLs for all toxic pollutants (not just 
mercury) assuming MDLs might be used as compliance limits (and the MDL 
used for compliance evaluation). The Assessment Document states that 
the minimum level (ML), not the MDL, should be used for compliance 
evaluation when the WQBEL is below the detection or quantitation limit 
of the most sensitive analytical method. Today's rule implicates 
neither of these limits (MDL nor ML) because EPA Method 1631 allows 
reliable measurements below the lowest ambient water quality criterion 
(1.3 ng/L) in the final Great Lakes Water Quality Guidance. The 
Assessment Document presumed that costs would increase if dischargers 
were required to meet discharge requirements at the lower MDLs, not 
that it would cost these amounts if EPA allowed use of another method 
for the measurement of mercury. In any event, EPA evaluated compliance 
costs in the Great Lakes rulemaking because it would result in 
establishment of standards of compliance. Today's rule does not set 
standards of compliance, only standards of measurement and analysis. 
This rule is considered a significant regulatory action and was, 
therefore, reviewed by OMB.
Unfunded Mandates Reform Act
    Comment: The Unfunded Mandates Reform Act (UMRA; 25 U.S.C. 1531, 
Subchapter II), requires assessment of the effects of regulatory 
actions on the private sector and preparation of a statement containing 
qualitative/quantitative cost-benefit analysis if costs are expected to 
exceed $100 million. EPA should perform the cost and benefit 
assessments because existing permits require the use of the most 
sensitive test procedure.
    Response: EPA acknowledges that some permits may require the 
permittee to use the most sensitive test procedure available at the 
time of permit issuance, for example, when the limit is below detection 
of approved methods. Today's rulemaking does not automatically change 
permits issued prior to today. The only costs associated with today's 
rule are analytical costs, not compliance costs. Today's rule is not 
subject to the requirements of sections 202 and 205 of UMRA because it 
does not contain a Federal mandate that could result in expenditures of 
$100 million or more for State, local, and tribal governments, in the 
aggregate, or the private sector in any one year. EPA estimates the 
incremental analytical costs associated with the use of EPA Method 1631 
instead of another approved method for mercury to be less than $2.6 
million per year. EPA believes that this rule does not impose any 
regulatory requirements that might significantly or uniquely affect 
small governments because the rule approves an additional test 
procedure for the measurement of mercury that might be regulated by 
some other action (e.g., a permit that implements a State-adopted water 
quality standard).
Regulatory Flexibility Analysis
    Comment: The Regulatory Flexibility Act (RFA) requires description 
of impact of regulatory actions on small entities. EPA is incorrect in 
stating that the rule will not have a significant economic impact on 
small facilities. Commenters request that the rule be subject to OMB 
review and a regulatory flexibility analysis.
    Response: In section VI.C. of the proposal, pursuant to section 
605(b) of

[[Page 30423]]

the Regulatory Flexibility Act, 5 U.S.C. 605(b), the Administrator 
certified that this rule will not have a significant economic impact on 
a substantial number of small entities. This regulation approves an 
additional test procedure (analytical method) for the measurement of 
mercury which may be required in the implementation of the CWA (e.g., 
issuance of permits and/or establishment of WQS). EPA Method 1631 is 
not a de facto replacement for EPA Method 245.1 or any of the other 
existing EPA-approved methods. EPA anticipates that permit writers will 
only require the use of EPA Method 1631 if there is a need to assess 
effluents or ambient water at the low levels EPA Method 1631 can 
measure or after a determination that a discharge causes, has a 
reasonable potential to cause, or contribute to an excursion from a 
water quality criterion for mercury. EPA further anticipates that the 
incremental analytical costs that may potentially be incurred by any 
small entity with low mercury limits will be at most $600 per year, 
assuming monthly monitoring.
4. Regulatory implications
Support for Use in Permitting
    Comment: EPA should require immediate implementation of the new 
method and should require States to begin requiring it for NPDES 
compliance as soon as possible.
    Response: Today's rule authorizes use of EPA Method 1631 but does 
not require its use for compliance monitoring or any other uses. The 
Agency developed EPA Method 1631 to enable reliable measurement of 
water samples at the levels established in water quality criteria. 
Consequently, EPA expects that when the measurement sensitivity of EPA 
Method 1631 is necessary to assess and implement water quality controls 
(including compliance monitoring), EPA Method 1631 will be used. If and 
when other methods for measuring mercury at these low levels are 
promulgated in 40 CFR part 136 or are approved under the procedures at 
40 CFR 136.4 and 136.5, the permitting authority would have discretion 
to determine which method is most appropriate under the circumstances.
    States that are authorized to administer the NPDES program must 
require use of 40 CFR part 136 methods. EPA recognizes that States may 
need to follow State procedures to adopt changes to 40 CFR part 136 
before they can require use of a newly promulgated method and allows 
States a reasonable time to accomplish this. See 40 CFR 123.62(e). EPA 
regulations do not require that permits be reopened to include a new 
analytical method. Instead, the permitting authority may have the 
opportunity to reopen the permit or to wait until the permit is 
reissued to include a new or more sensitive analytical method. See 40 
CFR 122.62(a)(2).
Best Available Sensitivity
    Comment: EPA failed to acknowledge that many existing permits 
require the permittee to use the test method with the lowest detection 
level.
    Response: EPA recommends that EPA Method 1631 be used only for 
situations in which mercury may be known or thought to be the cause of 
an environmental or human health problem, or for investigations 
directed at determining whether a problem exists, in the same way that 
EPA recommends that other test methods be used. EPA Method 1631 is 
being made available for use when it is necessary to measure mercury 
concentrations at low levels. As previously explained, existing permit 
requirements to use the most sensitive method available may only 
incorporate the most sensitive method at the time the requirement was 
imposed, not methods adopted in the future.
Reporting vs. Use of Data
    Comment: EPA Method 1631 states that results need not be reported 
for regulatory compliance purposes if the results do not satisfy QC 
acceptance criteria. The Inter-Industry Analytical Group (IIAG) 
suggests that EPA change the phrase to read: ``. . . may not be 
reported or otherwise used for permitting or regulatory compliance 
purposes.'' IIAG also requests that EPA clarify that results from tests 
performed with an analytical system that is not in control also should 
not be reported or otherwise used for permitting or regulatory 
compliance purposes.
    Response: EPA has adopted IIAG's suggested wording, and changed 
relevant text in EPA Method 1631 accordingly. The wording changes 
clarify the Agency's intent that data that fail to meet the Method's QC 
acceptance criteria are not reliable measurements of mercury.
Iodide Interference
    Comment: The Inter-Industry Analytical Group (IIAG) comments that 
EPA fails to give adequate consideration to interferences and cites, as 
an example, an iodide interference problem encountered by GPU Nuclear 
Co. (GPU) using EPA Method 245.1. GPU attributes this interference to 
formation of a stable complex of iodide and mercury that prevents 
reduction of mercury to its elemental form with the stannous chloride 
(SnCl2) reductant. (SnCl2 also is used in EPA 
Method 1631). GPU has overcome the problem by addition of a small 
amount of sodium tetrahydroborate to aid in reduction of mercury.
    Response: EPA did not claim that EPA Method 245.1 was free from 
test interference. The claim was made concerning EPA Method 1631. EPA 
Method 1631 uses different chemistry than EPA Method 245.1. In EPA 
Method 1631, mercury is oxidized to Hg(II) with bromine monochloride, 
pre-reduced with ammonium hydroxide hydrochloride 
(NH2OHHCl) to destroy free halogens, then reduced 
with SnCl2. The NH2OHHCl likely plays 
the same role as the sodium tetrahydroborate in GPU's procedure. EPA 
has now received a report that high concentrations of iodide (>40 mg/L) 
can interfere in the determination of mercury using EPA Method 1631. 
These high concentrations can occur in in-process streams and 
influents, but normally would not be encountered in treated effluents. 
To allow for the possibility that high concentrations of iodide, 
however, and the possibility that other substances could interfere in 
the determination of mercury using EPA Method 1631, today's version of 
EPA Method 1631 acknowledges that test interference remain a slight 
possibility.
Variability and Regulatory Decisions
    Comment: The Inter-Industry Analytical Group (IIAG) comments that 
EPA's QC acceptance criteria and other variability must be taken into 
account in regulatory decisions. IIAG cites the QC acceptance criteria 
for the matrix spike and matrix spike duplicate (MS/MSD) in EPA Method 
1631 and questions EPA's rationale for determining that such a wide 
range of performance is acceptable, given the harsh regulatory 
consequences associated with excursion of permit limitations. IIAG 
states that EPA must explain why such variability is acceptable and how 
regulators are required to account for that variability in their 
permitting and/or compliance decisions.
    Response: EPA disagrees that QC acceptance criteria are ``wide.'' 
These criteria are consistent with, or narrower than, other methods for 
measuring pollutants at these levels (see for example the QC acceptance 
criteria for EPA Methods 608 and 1613 at 40 CFR part 136, appendix A). 
The QC acceptance criteria recognize the variability expected to occur 
among laboratories. The EPA developed the criteria from multiple, 
single-laboratory

[[Page 30424]]

data and verified the data in the interlaboratory study. The Agency 
used the laboratory data to develop the QC acceptance criteria in 
today's rule.
    Regarding accounting for variability in permitting and compliance 
decisions, EPA's technology-based rules do account for analytical 
variability because measurement variability is a component of the 
overall variability encountered to develop the rule (including field 
measurement). Therefore, no additional allowance for analytical 
variability is appropriate. For water quality uses, accommodation for 
the effect of analytical variability is less routinized. In the 
Technical Support Document (TSD) for Water Quality-based Toxics Control 
(EPA/505/2-90-001), EPA noted that accounting for analytical 
variability in establishing permitting requirements can result on the 
one hand, in failure to be adequately protective of the wasteload 
allocation or, on the other hand, to be overly conservative. Therefore, 
EPA recommended against any additional allowance for analytical 
variability. However, EPA currently is developing guidance on 
accounting for analytical variability in permitting in the context of 
the whole effluent toxicity program. When finalized, that guidance may 
provide the basis for revising the position taken in the TSD with 
respect to accounting for analytical variability in general.
5. Retention of Approved Methods and Approval of Additional Methods
Support as Additional Method, With Qualification
    Comment: Commenters support approval of EPA Method 1631 if it is an 
addition to the list of approved methods and not a replacement for 
existing methods, especially if a laboratory can demonstrate that it 
can achieve low ng/L detection limits (including needed sensitivity) 
with one of the presently approved methods.
    Response: Today's rule approves EPA Method 1631 as an additional 
method that can be used when measurement of mercury at water quality 
criteria levels is needed. EPA doubts that a laboratory can achieve the 
low levels (including needed sensitivity) with one of the presently 
approved methods. Typically, the MDL of a method should be an order of 
magnitude (factor of 10) below the level desired for measurement (e.g., 
a regulatory compliance limit, or any water quality criterion) so that 
contamination can be detected and the effects of contamination 
evaluated. If the detection limit is at or near the level desired for 
measurement, it would be difficult to determine if the presence of the 
substance is real or is attributable to contamination. The capabilities 
of EPA Method 1631 enable such an evaluation.
Support Continued Use of Approved Methods
    Comment: EPA should continue to allow the use of other approved 
methods. Withdrawal of existing methods (EPA 245.1, 245.5, Standard 
Method 3112B, ASTM D3223-91, USGS I-3462-85, and AOAC-International 
977.2) would be disastrous. There would be serious adverse economic 
ramifications if EPA Methods 245.1 and 245.2 are withdrawn. EPA Method 
1631 should not be imposed on the private sector as the sole method. 
The option of using less sensitive methods should remain where EPA 
Method 1631 sensitivity is not needed.
    Response: Based on comments received and the points made in those 
comments, today's rule allows continued use of the presently approved 
methods for determination of mercury when those methods achieve the 
desired measurement objective.
Performance-Based Measurement System
    Comment: The performance-based measurement system (PBMS) as applied 
in proposal allows for sample preparation and trapping modifications, 
but does not allow for use of atomic absorption. EPA should accept 
application of PBMS for a different absorbance technique when it can 
achieve needed sensitivity.
    Response: EPA proposed to implement PBMS in its water measurement 
programs (62 FR 14975, March 28, 1997) but has not yet promulgated a 
final PBMS rule. EPA anticipates that the final rule will allow use of 
alternate determinative techniques such as atomic absorption. Until a 
final rule is promulgated, however, methods approved at 40 CFR part 136 
must be used according to their terms. Approval of the use of alternate 
procedures, such as alternate determinative techniques, can be 
requested through the alternate test procedure provisions described at 
40 CFR 136.4 and 136.5.
6. Application to Wastewater Matrices
Inapplicable to Effluent
    Comment: EPA Method 1631 is not applicable to the determination of 
mercury in effluents. The Method should contain a statement that it is 
not intended for the determination of concentrations normally found in 
industrial discharges. Language in an earlier version of EPA Method 
1631 (January 1996) stated that ``this method is not intended for 
determination of metals at concentrations normally found in treated and 
untreated discharges from industrial facilities.''
    Response: When the Agency first began development of EPA Method 
1631, the method description contained the statement that it was 
applicable to ambient monitoring but that it was not intended for 
application to industrial discharges. Since then, however, in studies 
of POTWs along the Great Lakes, in the interlaboratory validation 
study, and in other recent studies (Results of Method 1631 Application 
to Effluent Matrices (March 1999) and Application of Method 1631 to 
Industrial and Municipal Effluents (December 1998)), EPA has found that 
mercury could be reliably measured at low levels in municipal and 
industrial discharges. For this reason, and because some States 
requested EPA support to develop the method for measurement of 
municipal and industrial discharges, the Agency expanded EPA Method 
1631 to cover wastewaters. The statement regarding restricted use of 
EPA Method 1631 was deleted from the January 1996 version.
Testing One Effluent Is Inadequate
    Comment: Testing one effluent at one level by a few laboratories is 
not an appropriate inter-laboratory study for general NPDES 
application.
    Response: The Agency validated EPA Method 1631 on one filtered and 
one unfiltered wastewater matrix in the interlaboratory validation 
study. Subsequently the Agency gathered additional effluent data in 
response to comments regarding the method's applicability to 
wastewaters generally. EPA made these data available in a notice of 
data availability on March 5, 1999 (64 FR 10596). These data 
demonstrate that EPA Method 1631 is applicable for measurement of 
municipal and industrial effluents.
7. Detection and Quantitation
MDL Is Flawed
    Comment: Several commenters state that Agency estimates of 
detection and quantitation in EPA Method 1631 are flawed. The estimates 
cannot be achieved in real world use. The estimates are scientifically 
unsound. The estimates are neither realistic nor reproducible. The 
estimates use an inappropriate multiplication factor. They overestimate 
the certainty associated with measurements. The estimates are not 
representative of expected performance by qualified laboratories. They 
are not a valid statistical basis for predicting laboratory

[[Page 30425]]

performance. The estimates were based on spikes into reagent water 
instead of wastewaters. The estimates do not consider effluent 
characteristics. The estimates are based on a protocol that has never 
been subjected to peer review and public comment. The estimates do not 
reflect the performance capability of laboratories that will be 
performing compliance monitoring.
    Response: EPA disagrees that the MDLs and MLs in EPA Method 1631 
were developed inappropriately. EPA Method 1631 employs the method 
detection limit (MDL) (see 40 CFR part 136, appendix B). The MDL is 
defined as the minimum concentration of a substance that can be 
measured and reported with 99% confidence that the analyte 
concentration is greater than zero and is determined from analysis of a 
sample in a given matrix containing the analyte. The MDL procedure is 
not designed to control ``false positives'' or ``false negatives,'' 
allow for repetitive testing, or predict laboratory performance. 
However, since the variability of the blank is expected to be 
approximately equal to the variability at the MDL, measurement results 
greater than the MDL are unlikely to be obtained when measuring samples 
that do not contain the substance of interest. In effect, the MDL can 
be used to control the rate of ``false positives.'' Reagent water is 
the matrix used for determining the MDL performance measure of a method 
because (1) reagent water is available to all laboratories, (2) reagent 
water allows determination of the lowest concentration of a substance 
that can be detected absent matrix interferences, and (3) there is no 
matrix that represents all wastewater matrices. Application of the MDL 
procedure to particular methods has been subject to peer review and 
public comment with every MDL that EPA publishes in nearly every 
chemical-specific method proposed in the Federal Register since 1984. 
The MDL procedure has widespread acceptance and use throughout the 
analytical community. No other detection or quantitation limit 
procedure or concept has achieved this level of acceptance and use.
    EPA Method 1631 incorporates the concept of a minimum level of 
quantitation (ML), which is the lowest level at which an analytical 
system is expected to give a recognizable signal and acceptable 
calibration point. In 1994, EPA revised its use of the ML concept to 10 
times the standard deviation associated with the MDL in order to be 
more consistent with the limit of quantitation (LOQ) of the American 
Chemical Society (ACS). The LOQ is based on a standard deviation of 
replicate measurements on a blank, which is expected to be 
approximately equal to the standard deviation of replicate measurements 
at the MDL. Therefore, EPA expects the ML to be approximately equal to 
the LOQ. Because the MDL is established at 3.14 times the standard 
deviation associated with the MDL and the ML is 10 time the standard 
deviation associated with the MDL, the multiplier between the MDL and 
ML is 3.18. EPA believes that this multiplier is consistent with other 
multipliers selected for the purpose of quantitation and that this 
multiplier is therefore appropriate. Readers are referred to the 
response to comments document in the Docket for today's rulemaking for 
a more detailed response.
    EPA plans to continue to examine the issues of detection and 
quantitation. The Agency initiated a study recently to examine the 
effects of error from various analytical systems on detection and 
quantitation, and plans to involve the public in the application of the 
data being gathered to develop an improved approach, if such an 
approach is found to exist.
Use of the MDL/ML Concepts Violate Administrative Procedure Act
    Comment: Commenters opposed EPA's proposed detection and 
quantitation levels because EPA did not provide the opportunity for 
review and comment on the basis for the proposed decisions. EPA's 
proposal neither describes the origin of the MDL nor explains why the 
Agency believes that it is an acceptable basis for developing detection 
levels for use in compliance determinations.
    Response: The MDL concept origin is an article published in the 
peer-reviewed scientific literature in 1981 (Environmental Science and 
Technology 15 1426-1435). The MDL procedure has been used in EPA's 
various environmental programs since it was published at 40 CFR Part 
136, Appendix B in 1984. The MDL procedure is accepted and used by 
nearly all organizations making environmental measurements. Recently, 
EPA has undertaken data gathering that should allow re-examination of 
detection and quantitation limits. When this study is complete, EPA 
will decide if the MDL and ML continue to be appropriate or if other 
concepts are appropriate for EPA's scientific and regulatory purposes. 
EPA has involved, and will continue to involve, stakeholders in this 
process and in EPA's final decision. Until other detection and 
quantitation limit concepts are shown to be more appropriate, EPA will 
continue to use the MDL and ML for the reasons stated at the beginning 
of this response, in other responses, and in other rules.
MDL Violates A 1985 Judicial Settlement
    Comment: A commenter noted that, in a judicial settlement in 1985, 
EPA agreed that the MDL procedure published at 40 CFR part 136, 
appendix B, was intended to apply exclusively to the subset of the test 
methods that the Agency published at 40 CFR part 136, appendix A, in 
1984. Thus, the commenter argues that, if EPA uses the MDL procedure 
for the purpose of deriving a detection level for EPA Method 1631, the 
Agency must provide the public an opportunity to review and comment on 
that decision. As justification for use of the MDL, EPA gave the 
reasons that (1) laboratories that participated in the EPA Method 1631 
study were able to calculate an MDL at least as low as that achieved in 
an earlier study, and (2) the MDL is well below the lowest water 
quality criterion (WQC) in the National Toxics Rule and listed in the 
final water quality guidance for the Great Lakes System. The commenter 
argues that these reasons may be desirable but that they are irrelevant 
for determining an appropriate detection level. The commenter argues 
that EPA must first confirm that good laboratories can achieve that 
level.
    Response: The commenter is correct that, in 1985, EPA agreed in a 
settlement that the MDL procedure at 40 CFR part 136, appendix B, was 
applicable to the 40 CFR part 136, appendix A methods only. The 
settlement, however, did not restrict future application of the MDL 
procedure, nor did it restrict any person's right to challenge the 
Agency's reliance on the MDL procedure in any future rulemaking. EPA 
provided the opportunity for comment on use of the MDL in EPA Method 
1631. EPA believes that the interlaboratory validation study of EPA 
Method 1631 confirms that good laboratories can achieve the detection 
and quantitation levels that EPA established for EPA Method 1631.
Effluent Study Offers No Support for the MDL Performance Measure in EPA 
Method 1631
    Comment: If the intent of EPA's effluent study was to determine 
whether MDL calculations are influenced by the sample matrix, EPA 
should have used a matrix more representative of real world samples 
rather than the City of Eugene's POTW effluent. The mercury level in 
the City's effluent was lower than in any

[[Page 30426]]

of the other effluents used in EPA's study.
    Response: Step 3(b) of the MDL procedure at 40 CFR part 136, 
appendix B requires that the measured level of analyte be less than 
five times the MDL. The MDL in EPA Method 1631 is 0.2 ng/L. Five times 
the MDL is 1.0 ng/L and therefore the concentration of mercury in the 
MDL study needed to be in the range of 0.2 to 1.0 ng/L. The measured 
level of mercury in the City of Eugene's POTW effluent was 0.56 and 
0.72 ng/L, based on data collected prior to the MDL study. Therefore, 
the mercury concentration of the City's sample was in the appropriate 
range for the MDL study.
    8. Clean techniques
Clean Techniques Should Be Required
    Comment: The rule should require clean sampling, handling, and 
analysis when EPA Method 1631 is used and the Agency should develop a 
comprehensive database on the level of contamination that may arise. A 
commenter provided a list of sections in EPA Method 1631 that allow 
discretion but that the commenter believes must be made mandatory to 
assure reliable and reproducible results, for example, if government 
inspectors measure the same sample effluents. The commenter argues that 
EPA must explain its rationale for deciding that certain clean 
techniques are mandatory and to justify its decision that other 
techniques are not mandatory and, therefore, can be left to the 
discretion of enforcement officials. The only exception to required use 
of clean techniques should be that permittees should have complete 
discretion as to the use of such techniques because the failure to use 
such techniques can only result in mercury results higher than the 
level actually present in an effluent.
    Response: During the development of EPA Method 1631, the Agency 
found some researchers using very extensive measures for clean 
sampling, including the wearing of clean room caps, suits, booties, and 
shoulder-length gloves in addition to hand-length gloves. On the other 
hand, EPA found other researchers wearing shorts, tee shirts, and hand-
length gloves only. Because the Agency sought to maximize the 
flexibility of capable personnel, EPA provided the Sampling Guidance 
(EPA Method 1669) to indicate measures to prevent and preclude 
contamination. The sampling guidance is not mandatory for use with EPA 
Method 1631 because some permittees and sampling teams are capable of 
reliable sample collection without the measures detailed in the 
guidance. The rigor of clean sample collection techniques is determined 
by the required measurement objective or regulatory level (i.e., the 
lower the desired level, the more critical is the adherence to rigorous 
clean sampling protocols). Those elements of clean sampling, handling, 
and analysis that the Agency believes are necessary to assure reliable 
and reproducible results have been incorporated into EPA Method 1631. 
For example, the use of clean gloves by all sampling personnel and the 
use of metal-free apparatus are requirements specified in the method. 
In addition, the QC requirements in the method are designed to detect 
potential contamination that may arise in the field, during transport, 
or in the laboratory.
    Regarding development of a comprehensive database, the Agency does 
not see the need to develop a database on the level of contamination 
that may arise. In both EPA Method 1631 and the Sampling Guidance (EPA 
Method 1669), EPA is very explicit that contamination is a concern and, 
consequently, the Agency provided appropriate measures to minimize 
contamination.
    EPA includes a number of mandatory steps in a method when it 
believes those steps are necessary to provide reliable analytical 
results. If EPA were to justify every discretionary aspect of a method 
(indicated by the words ``should,'' or ``may,'' and other words 
denoting suggestions) for every method or guidance document that the 
Agency develops, method and document development would grind to a halt. 
Parametric studies of every variable that could possibly influence the 
outcome of a method or use of a document would become cost-prohibitive. 
The list of discretionary techniques in EPA Method 1631 that the 
commenter suggests should be evaluated would require 20 parametric 
studies.
Clean Techniques Should Not Be Required
    Comment: Clean techniques should not be required. There is no 
documentation in the record that clean field blanks and clean samples 
can be collected. This casts doubt on the ability of laboratories and 
permittees to use this method in day-to-day activities designed to meet 
Clean Water Act requirements. Clean techniques are an unnecessary 
expense because detection levels this low are not needed for personal 
or environmental protection. EPA Method 1631 is able to detect such low 
levels that sample collection and analysis must occur in pristine 
environments to prevent false positives.
    Response: Clean techniques are not required but are recommended for 
low level mercury measurements associated with WQ criteria. EPA 
cautions, however, that contamination has been identified as a 
potential problem in collecting samples for mercury prior to the advent 
of clean techniques. Use of these techniques, as detailed in the 
sampling guidance (EPA Method 1669) and in the technical literature 
(see references 2-9 of EPA Method 1631), has allowed collection of 
samples free of contamination at ng/L levels. EPA urges use of clean 
techniques, as appropriate, to preclude contamination. As stated 
earlier, those elements of clean sampling, handling, and analysis that 
the Agency believes are necessary to assure reliable and reproducible 
results have been incorporated into EPA Method 1631.
    Although EPA agrees that clean techniques should not be (and are 
not) required, EPA disagrees with the commenters assertion that the 
record contains no documentation that clean field blanks and clean 
samples can be collected. The EPA Method 1631 Interlaboratory Study 
included the collection of field samples for use in the study, and 
results from background and QC analyses demonstrated the ability to 
collect clean field blanks and samples. Following proposal of the 
method, EPA also collected additional effluent data and made those 
data, including QC results, available in the Docket and through a 
notice of data availability (64 FR 10596). These data provide further 
demonstration that clean field blanks and clean samples can be 
collected.
9. Corrections to statements in proposal
Holding Time
    Comment: Proposed EPA Method 1631 lists a holding time of 6 months. 
EPA used a period of only one month, however, to evaluate the stability 
of the samples. Please provide the basis for the large variation in 
holding times between EPA Method 1631 (6 months), EPA Method 245.1 (28 
days), and draft EPA Method 245.7 (72 hours). EPA must have data to 
support the specified maximum holding time and will need to change 
holding time in CFR if EPA Method 1631 is approved.
    Response: EPA specified the maximum holding time at 6 months in the 
proposed version of EPA Method 1631 based on statements by a number of 
laboratories involved in development of EPA Method 1631 that samples 
could be held for this period. EPA requested data that would support 
the 6 month holding time. Data were not forthcoming. Therefore, in 
today's

[[Page 30427]]

version of Method 1631, EPA has specified a maximum holding time of 28 
days, consistent with Table II at 40 CFR part 136.
Lowest Water Quality Criterion
    Comment: The lowest water quality criterion (WQC) for the Great 
Lakes Water Quality Guidance is not 1.8 ng/L. It is 1.3 ng/L, the 
criterion for wildlife protection (see Table 4 to 40 CFR part 132). 
Waters of the United States frequently exceed these levels even where 
there is no direct industrial or municipal discharge.
    Response: EPA stands corrected. EPA recognizes that waters of the 
United States can exceed Great Lakes WQC levels, even where there is no 
industrial or municipal discharge. That possibility, however, does not 
affect the substance of today's rule.
10. Quality Control
Excessive quality ControL
    Comment: The quality control (QC) in EPA Method 1631 is excessive, 
unreasonable, far more rigorous than in currently approved methods, and 
demonstrates the inappropriateness of this method for general 
application.
    Response: The QC in EPA Method 1631 is consistent with the other 40 
CFR part 136, appendix A methods and consistent with requirements for 
other environmental analytical chemistry methods. EPA believes that the 
QC requirements are necessary to ensure the reliability of data results 
and that these requirements are not onerous.
Insufficient Quality Control
    Comment: Without addition of more comprehensive QC for background, 
mercury determinations at low ppt levels are subject to unknown and 
unacceptable bias and imprecision. Additional validation and 
modification to the QA/QC are necessary for the method to realize its 
potential of being a rugged method capable of providing reliable 
quantification of mercury at sub-ng/L concentrations.
    Response: Bubbler blanks, reagent blanks, and method blanks serve 
as checks on contamination. The MDL performance capacity of Method 1631 
is 0.2 ng/L. This MDL enables detection of contamination at sub-ng/L 
concentrations, should such contamination occur. A discharger or 
laboratory is not precluded from performing additional QC if it 
desires.
Method Performance
    Comment: A commenter argues that EPA must assure that the 
irreducible performance limitations inherent in all methods will not 
act to penalize persons for lawful conduct. EPA cannot provide such 
assurances absent adequate performance data, which can only be derived 
from properly conducted method validation studies. If EPA determines 
that a test method has been adequately validated, EPA must publish 
performance characteristics along with the method.
    Response: EPA conducted a validation study on EPA Method 1631. 
Published method performance characteristics associated with the Method 
include: (1) A method detection limit (MDL) and minimum level of 
quantitation (ML) in Table 1, (2) quality control (QC) acceptance 
criteria in Table 2, and (3) precision and recovery data for six sample 
types in Table 3. These data more than adequately support the adequacy 
of the Agency's validation of EPA Method 1631.
11. Blanks and Contamination
Reagent Blanks
    Comment: Reagent blanks also should be subtracted from sampling 
results. Otherwise, inaccurate, high results will be reported.
    Response: Section 12.4 in EPA Method 1631 asks for separate 
reporting of results for samples and blanks, unless otherwise requested 
or required by a regulatory authority or in a permit. The reason for 
separate reporting is so that a regulatory authority can assess if 
results for samples are attributable to contamination and the extent to 
which contamination is affecting the measurement. There is no 
prohibition in EPA Method 1631 against reporting blank-subtracted 
results, provided, of course that results for blanks and samples are 
reported separately.
Bubbler and Reagent Blanks Inadequate
    Comment: Bubbler blanks and reagent blanks only demonstrate that 
the analytical system is uncontaminated. Analysis of field or equipment 
blanks should not be used to demonstrate laboratory capabilities.
    Response: EPA agrees that bubbler blanks and reagent blanks are 
used to demonstrate that the analytical system is uncontaminated. EPA 
disagrees that field blanks or equipment blanks should not be used to 
demonstrate laboratory capabilities. The laboratory is responsible for 
determining and reporting field contamination and for demonstrating 
that equipment blanks are free from contamination. Section 9.4 of EPA 
Method 1631 also contains a statement ``it is suggested that additional 
blanks be analyzed as necessary to pinpoint sources of contamination 
in, and external to, the laboratory.'' Both field and laboratory 
contamination sources may affect the analytical results.
Blank Subtraction
    Comment: It should be acceptable to subtract field blank results in 
addition to reagent and bubbler blanks. EPA must require correction for 
reagent blanks.
    Response: EPA has revised section 12.4 of the method to ask for 
reporting the concentration of mercury in field blanks but has not 
required blank subtraction so that a regulatory authority can assess if 
results for samples are attributable to contamination and the extent to 
which contamination is affecting the measurement. A regulatory 
authority or other data user may subtract the concentration of mercury 
in field blanks or reagent blanks if it believes this subtraction is 
appropriate. Today's rule does not preclude the reporting of blank-
subtracted results provided that results for samples and blanks are 
reported separately.
Sample-Specific Reagent Concentrations
    Comment: The reagent blank does not address sample-specific 
variation in reagent concentrations. Section 11.1.1.2 states that 
sewage effluent will require high levels of bromine monochloride 
(BrCl). The increased requirement for BrCl for samples high in organic 
materials could increase the background contribution if the BrCl 
contains trace amounts of mercury. This could lead to a high bias for 
mercury in samples that require high levels of BrCl. EPA Method 1631 
states that BrCl cannot be purified (section 9.4.2.3).
    Response: EPA agrees and has added the requirement that whatever 
concentration or amount of reagent that is added to the sample must 
also be added to the reagent blank in order to identify the reagent as 
a potential source of contamination. Regarding the statement in EPA 
Method 1631 that BrCl cannot be purified, EPA believes that this 
statement is true. BrCl, however, is made in the laboratory from 
several reagents that can be obtained in highly purified form. The 
resulting BrCl will then be very pure.
12. Validation Study
Insufficient Validation
    Comment: Insufficient method validation has been provided to 
justify method use for routine NPDES purposes.
    Response: The validation steps performed with EPA Method 1631 are

[[Page 30428]]

the same as EPA has performed with many other methods. The Agency 
validated EPA Method 1631 first in multiple single-laboratory studies 
and then further validated the method in an interlaboratory study. EPA 
followed ASTM Practice D 2777 in the interlaboratory validation study 
design. Some members of the ASTM Committee D-19 on water reviewed the 
interlaboratory study plan and contributed to the study. In response to 
commenters concerned about the application of EPA Method 1631 to NPDES 
effluents, EPA gathered data on application of EPA Method 1631 to 
effluents and made these data available to commenters for review prior 
to today's final rule (64 FR 10596).
Validation Under Routine Conditions
    Comment: Validation data results were not obtained under normal, 
routine analytical operations. EPA Method 1631 should not be 
promulgated until it is validated using commercial laboratories able to 
sample and analyze waste streams using ultra-clean techniques. The fact 
that EPA Method 1631 has been subjected to the required validation 
studies alone does not ensure that it is ready for widespread 
application.
    Response: Commercial laboratories were included in the 
interlaboratory method validation study and all laboratories involved 
in the study perform mercury analyses routinely using the techniques in 
EPA Method 1631. It is not necessary for commercial laboratories 
involved in the analysis of samples for mercury to be able to sample 
waste streams, although some do. All laboratories involved in the 
interlaboratory study analyze waste streams and all of the laboratories 
involved in the study determined their respective detection limits. EPA 
believes that the fact that EPA Method 1631 has been subjected to the 
required validation ensures that it is ready for widespread 
application. Over time, commercial laboratories will develop capacity 
to conduct EPA Method 1631 just as they have for other, previously 
approved test methods.
Additional Interlaboratory Studies
    Comment: EPA's intralaboratory (i.e., within laboratory) studies 
reported in the Docket with the NODA failed to evaluate the matrix 
issue in a ``real-world'' interlaboratory context. EPA did not assess 
interlaboratory precision and bias in studies included with the NODA. 
EPA's data are insufficient to characterize precision and bias of 
mercury measurements in industrial effluents. Although the study 
included analysis of mercury samples by multiple laboratories, none of 
the samples was split between laboratories. The studies should have 
been designed to determine interlaboratory and multi-matrix precision, 
accuracy, and sensitivity of EPA Method 1631.
    Response: Assessing interlaboratory precision and bias was not an 
objective of the additional studies. EPA assessed interlaboratory 
precision in the interlaboratory validation study and published 
performance data for the interlaboratory validation study in the report 
that was included in the Docket at proposal. In comments on EPA's 
proposal of EPA Method 1631 on May 26, 1998 (63 FR 28867), commenters 
expressed concern that only one municipal secondary effluent had been 
analyzed to determine precision and bias and that no industrial 
wastewater samples were analyzed. They argued that it was unreasonable 
for EPA to adopt a method with no data on the applicability to a wide 
variety of wastewater matrices. In response to those concerns, the 
Agency applied EPA Method 1631 to a wide variety of wastewater 
matrices, including industrial wastewater samples. EPA gathered data 
generated from the analyses of several different types of effluent 
samples in order to determine whether the results from that study meet 
the quality control (QC) acceptance criteria from the proposed method. 
EPA developed the QC acceptance criteria as a means of assuring the 
appropriate levels of precision and bias. Re-evaluation of precision 
and bias would be unnecessary if the QC acceptance criteria remained 
appropriate.
    The commenters claim that EPA Method 1631 was validated 
inadequately because EPA did not conduct interlaboratory method 
validation studies on a wide variety of wastewater matrices containing 
naturally occurring mercury levels near the ML of EPA Method 1631. EPA 
disagrees. The ASTM guidelines recommend the use of reagent water as a 
reference matrix in at least one environmental sample matrix other than 
the reference matrix. EPA included a municipal effluent in the 
interlaboratory validation study. It would be impractical to use a wide 
variety of wastewater matrices with natural concentration near the ML 
of EPA Method 1631 because the levels in the sample are unknown prior 
to analysis. EPA followed ASTM and AOAC guidelines for the 
interlaboratory method validation study conducted prior to proposal. 
EPA believes that the Agency has fully addressed commenters' requests 
for additional data on the application of EPA Method 1631 to 
wastewaters. Commenters that have requested that EPA conduct extensive 
interlaboratory studies were involved in, and had the opportunity to 
contribute to, EPA's interlaboratory method validation study at the 
time it was conducted. These commenters chose not to contribute to a 
more extensive study or conduct studies on their own.
    EPA reiterates that the main objective in conducting the additional 
studies was to demonstrate that effluent samples containing mercury at 
or near the ambient water quality criteria levels given in the National 
Toxics Rule (40 CFR 131.36) and in the Water Quality Guidance for the 
Great Lakes System (40 CFR part 132) could be analyzed with little or 
no difficulty. Data included in the Docket with the NODA and data 
provided by the State of Maine demonstrate that these measurements can 
be made reliably, claims from commenters about interlaboratory 
variability, precision, accuracy, and sensitivity notwithstanding.
Insufficient Concentrations
    Comment: A commenter argued that EPA failed to validate EPA Method 
1631 at a sufficient number of concentrations. The commenter cites a 
report prepared by the Electric Power Research Institute (EPRI) in 
which consultants to EPRI cite ASTM Practice D 2777-96 as the need to 
validate the method using samples spiked at multiple levels.
    Response: EPRI and EPA collaborated on the study design for the EPA 
Method 1631 interlaboratory validation study. EPA shared data from the 
study with EPRI's consultants immediately after these data were 
verified and validated. The consultants acknowledge the collaboration 
in the attachment to the comment. At the outset of the study, EPA and 
EPRI agreed on the limitations of the study, including that there were 
insufficient resources to test every matrix at multiple levels. In the 
study, EPA validated EPA Method 1631 at multiple levels in reagent 
water and in freshwater collected near Port Washington, Wisconsin. To 
support today's final rule, EPA has gathered additional data on a 
variety of complex effluents using EPA Method 1631 and evaluated them 
at the low concentration levels of interest (i.e., low parts per 
trillion). These data represent the application of the Method to ``real 
world'' effluent samples. The data results demonstrate that Method 1631 
can be successfully applied to effluents because all of the matrix 
spike and

[[Page 30429]]

matrix spike duplicate (MS/MSD) recoveries were within the QC 
acceptance criteria in EPA Method 1631, with the exception of two 
samples that were spiked at inappropriate levels.
EPA Did Not Follow Voluntary Consensus Standards Bodies (VCSB) 
Procedures
    Comment: A commenter claims that EPA failed to use available 
standards and practices from VCSBs to design its method validation 
study as required by the National Technology Transfer and Advancement 
Act (NTTAA) and Office of Management and Budget (OMB) Circular A-119. 
The commenter asserts that NTTAA makes no distinction between technical 
standards that are themselves scientific tests (i.e., analytical 
methods) and standards used in the evaluation of the effectiveness and 
reliability (i.e., validation) of those tests. The commenter states 
that EPA claims to have complied with NTTAA by developing a new mercury 
method that had not yet been developed by a VCSB and that EPA 
incorrectly claims to have followed VCSB standards for the design and 
conduct of its validation study.
    Response: EPA agrees that NTTAA and OMB Circular A-119 require 
federal agencies to consider available VCSB standards and practices. 
NTTAA requires federal agencies to consult with VCSBs and other 
organizations when such participation is in the public interest and is 
compatible with agency missions, authorities, priorities, and budget 
resources. If compliance with the requirement to use VCSB standards and 
practices is inconsistent with applicable law or otherwise impractical, 
a federal agency may elect to develop technical standards not developed 
or adopted by VCSBs if the head of the agency or department transmits 
to OMB an explanation of the reasons for using other standards.
    EPA disagrees with the commenter's statement that we failed to use 
available standards and practices from VCSBs to design its method 
validation study. EPA designed the interlaboratory study with 
participation by the Electric Power Research Institute (EPRI) and its 
consultants. Individuals in EPRI are members of ASTM Committee D-19 on 
water. Committee D-19 developed Practice D 2777. The Agency followed 
Practice D 2777 in the study design. Practice D 2777 requires the use 
of at least one representative (``reference'') sample matrix which is 
the same for all laboratories and recommends the use of at least one 
environmental sample matrix. Reagent water is recommended as the 
reference sample matrix. In a memorandum attached to the comment, the 
only statement suggesting that EPA did not follow Practice D 2777 in 
the study design is a statement that Practice D 2777 requires Youden 
pairs at a minimum of three concentrations per matrix. EPA included 
four concentration pairs in reagent water (and an unspiked pair), four 
concentration pairs for freshwater, and one concentration pair each for 
marine (one pair filtered and one pair unfiltered) and for a municipal 
effluent (one pair filtered and one pair unfiltered). EPA believes that 
the design of its validation study follows ASTM Practice 2777-96. EPRI 
members were aware of the resource limitations of the study and agreed 
that the design's limited number of Youden pairs and blind duplicate 
samples would not negate the usefulness of study results.
Performance Data Are Inadequate and Misleading
    Comment: A commenter argues that EPA's performance information is 
inadequate and misleading because it fails to include regression 
equations. Stakeholders need a means to predict how EPA Method 1631 
will perform at any particular level within its working range. EPA has 
provided regression equations in other methods. EPA inexplicably 
departed from this practice. The commenter further argues that EPA's 
performance information is inadequate and misleading because the EPA 
Method 1631 acceptance criteria are inconsistent with study results. 
For example, test data can be used if the initial precision and 
recovery falls within the range of 79-121 percent which is broader than 
the capability (86-113 percent) demonstrated by the EPA Method 1631 
interlaboratory study. EPA must explain the difference in the final 
rule, if only to avoid confusion in the interpretation of EPA Method 
1631 data.
    Response: EPA disagrees that the performance information is 
inadequate and misleading. As EPA has stated elsewhere in these 
responses, EPA has no knowledge of use of regression equations in the 
interpretation of data by dischargers or others. Regression equations 
are redundant with QC acceptance criteria. Regression equations can be 
used to calculate expected method performance at a given concentration. 
The expected performance can, in turn, be used to determine if a 
laboratory's performance is equivalent to the performance of 
laboratories in the interlaboratory study. On the other hand, 
laboratories that practice a method that contains QC acceptance 
criteria recognize these criteria as absolute standards of performance 
within which the method must operate. Calculating another standard of 
performance, as the commenter suggests, would be redundant. Further, 
because the QC acceptance criteria are an absolute standard, 
laboratories can be held accountable. If they fail to meet this 
standard, corrective action would be required followed by reanalysis of 
samples after the QC acceptance criteria are met. Standards of 
performance derived from regression equations do not ensure this 
result.
    The difference between the QC acceptance criteria listed in 
proposed EPA Method 1631 and in Table 11 of the interlaboratory study 
report are attributable to EPA's decision to not tighten the acceptance 
criteria from the draft method published in 1995 (EPA 821-R-96-027). 
EPA is concerned that any method that is iteratively tested may result 
in ever tightening QC acceptance criteria because succeeding data 
gathered with the method will likely fall within these criteria. EPA 
therefore retained the QC acceptance criteria from the draft method in 
the version of EPA Method 1631 proposed. In contrast, EPA has widened 
the QC acceptance criteria for the matrix spike and matrix spike 
duplicate (MS/MSD) between the proposed version and today's version. 
The reason for this widening is that the data gathered in the 
interlaboratory study demonstrated that the QC acceptance criteria for 
the MS/MSD were too restrictive. Making certain QC acceptance criteria 
unreasonably restrictive is onerous upon laboratories, especially new 
laboratories beginning to practice a method. Therefore, for EPA Method 
1631, the Agency decided not to tighten the QC acceptance criteria for 
the IPR and OPR, and loosened the QC acceptance criteria for the MS/
MSD.
Mercury Forms and Species
    Comment: Mercury exists in many forms and states. The 
interlaboratory validation study failed to consider molecular diversity 
of mercury.
    Response: EPA Method 1631 determines total mercury. The oxidation 
step in EPA Method 1631 oxidizes all commonly occurring forms and 
species to Hg(II) which is subsequently reduced to volatile Hg(0) so 
that it can be purged from solution and determined.
13. Technical details of EPA Method 1631
UV Oxidation
    Comment: EPA must study and validate EPA Method 1631 with UV

[[Page 30430]]

oxidation on a range of industrial effluents and sewage samples, 
including ``microbially-rich'' samples. Results of the commenters' 
studies suggest that UV photo-oxidation can increase recoveries in some 
effluents. The use of UV oxidation makes measurement of mercury method-
defined.
    Response: In section 3.1 of EPA Method 1631, the Agency suggests 
use of UV oxidation for microbially-rich samples. EPA has added 
recommendations for determining complete oxidation. These 
recommendations should aid in recovery of mercury from some samples, as 
the commenter suggests. Regarding all interferences not being 
oxidizable, the commenter provided no example of a non-oxidizable 
interference that could occur in wastewaters.
    Regarding the use of UV oxidation making mercury a ``method-defined 
analyte,'' mercury could become method-defined in EPA Method 1631 only 
if it were not recovered reliably from a large number of samples. For 
the few number of samples in which incomplete oxidation can occur to 
make consideration of mercury as ``method-defined,'' the additional 
recommendations should now assure complete oxidation so that mercury 
does not need to be considered ``method-defined.'' Total mercury can be 
determined reliably.
Safety
    Comment: There are safety hazards inherent in the practice of EPA 
Method 1631. The preparation of bromine monochloride (BrCl) is more 
hazardous than preparation of potassium permanganate (KmnO4). A 
significant amount of hot acid is involved in cleaning bottles/
glassware. Laboratory ovens will be destroyed or serve as a source of 
contamination as a result of cleaning bottles that need to sit 
overnight at 60-70  deg.C with HCl. Further clarification and 
explanation is requested on what is required for laboratory personal 
hygiene monitoring.
    Response: Section 5 of EPA Method 1631 is dedicated to safety 
issues, and the sampling guidance (EPA Method 1669) contains additional 
information on safety. Section 7.6 of EPA Method 1631 explicitly states 
that BrCl must be prepared under a hood because copious quantities of 
free halogens are generated. The sampling guidance contains detailed 
procedures for bottle cleaning including suggestions for a heated acid 
vat in which bottles may be cleaned. Use of metal ovens for heating 
acids is not suggested for the reason that the commenter states. EPA 
Method 1631 is performance-based, however, and allows laboratories to 
modify the cleaning protocols so long as the modified protocols are 
capable of yielding uncontaminated equipment blanks.
    Regarding personal hygiene monitoring, EPA has added the statement 
to EPA Method 1631 to recommend that the personal hygiene monitoring be 
performed using Occupational Safety and Health Administration (OSHA) or 
National Institute of Occupational Safety and Health (NIOSH) approved 
personal hygiene monitoring methods.
14. Miscellaneous
Toxicity Limit
    Comment: The fact that EPA has established toxicity limits at 
extremely low levels by a means not based on laboratory analyses does 
not mean that analytical technology can be developed.
    Response: EPA believes that ambient water quality criteria and 
health effects-based limits can best be supported by gathering of data 
at levels represented by these criteria and limits, the means for 
establishing these limits notwithstanding. EPA will continue to strive 
to develop the analytical technology that will allow reliable 
measurements at these levels.
Dissolved Mercury Only
    Comment: EPA should clarify that EPA Method 1631 applies to 
dissolved mercury only. If the total digestion is performed, naturally 
occurring sediments may contribute significant analyte concentrations 
to a result.
    Response: Today's rule approves use of EPA Method 1631 for 
determination of dissolved and total mercury. If a sample contains 
suspended material such as sediment, it is intended that the mercury 
attached to or contained in the sediment be included in the 
measurement.
Ambient Criterion Based on Methyl Mercury
    Comment: The ambient water quality criterion of 12 ng/L for mercury 
is based on methyl mercury. EPA incorrectly implied in the proposal 
that EPA Method 1631 should be used to show compliance with the methyl 
mercury-based 12 ng/L standard, and should remove reference to this 
standard if the method is finalized.
    Response: The criterion continuous concentration (CCC) of 12 ng/L 
is for total recoverable mercury in water (40 CFR 131.36(b)(1)). 
Today's rule approves EPA Method 1631 so that reliable measurements of 
mercury can be made at this level, the basis for the standard 
notwithstanding. Both ``total'' and ``dissolved'' mercury measurements 
can be made with this method.
Grab Samples
    Comment: The commenter requests that EPA provide a note in 40 CFR 
Part 136 that requires only grab samples should be collected when using 
EPA Method 1631 because of potential contamination with compositing 
sampling procedures.
    Response: EPA has not mandated use of grab samples because EPA does 
not wish to discourage use of automated compositing equipment or 
sampling by other means, although EPA cautions that precluding 
contamination using these methods is more difficult than with 
collection of grab samples.
Implementation
    Comment: A commenter argues that the rulemaking for EPA Method 1631 
also must provide an objective and clear description regarding how the 
Method is to be implemented in practice.
    Response: The meaning of the comment is unclear. If the commenter 
means that the details of EPA Method 1631 are inadequate and the 
procedures in EPA Method 1631 need to be developed further, EPA 
believes that the validation study demonstrates that the procedures in 
EPA Method 1631 are more than adequate for implementation of EPA Method 
1631 in practice.
    If the commenter means that EPA must examine the impact of the 
measurements made by the method on the regulatory process, EPA believes 
that this activity is outside the scope of method development, 
validation, and approval. EPA's regulations for water pollution control 
are based on wastewater treatment and water quality considerations as 
required by the Clean Water Act. EPA Method 1631 is simply a tool to 
measure total mercury in aqueous samples.
Personnel Qualifications
    Comment: A commenter argues that EPA should specify the minimum 
qualifications for persons performing EPA Method 1631. Section 4.3.2 of 
EPA Method 1631 states that it is imperative that the procedures be 
carried out by well-trained, experienced personnel.
    Response: Section 1.10 states that EPA Method 1631 ``should be used 
only by analysts who are experienced in the use of CVAFS techniques and 
who are trained thoroughly in the sample handling and instrumental 
techniques described in this Method. Each analyst who uses this Method 
must demonstrate the ability to generate acceptable results using the 
procedure in section 9.2.''

[[Page 30431]]

VI. Regulatory Requirements

A. Executive Order 12866

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), the 
Agency must determine whether a regulatory action is ``significant'' 
and therefore subject to 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.''
    Pursuant to the terms of Executive Order 12866, it has been 
determined that this rule is a ``significant regulatory action.'' As 
such, this action was submitted to OMB for review. OMB made no 
suggestions or recommendations on this rule.

B. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Pub. 
L. 104-4, 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, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' 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 an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA 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 EPA to adopt an alternative other than the least 
costly, most cost-effective or least burdensome alternative if the 
Administrator publishes with the final rule an explanation why that 
alternative was not adopted. Before EPA establishes any regulatory 
requirements that significantly or uniquely may affect small 
governments, including tribal governments, it must have developed under 
section 203 of UMRA, a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory proposals with significant 
federal intergovernmental mandates, and informing, educating, and 
advising small governments on compliance with the regulatory 
requirements.
    Today's final rule does not contain a federal mandate (under the 
regulatory provisions of Title II of the UMRA) for State, local, or 
tribal governments or the private sector that may result in 
expenditures of $100 million or more in any one year. EPA has 
determined that this rule contains no regulatory requirements that 
significantly or uniquely might affect small governments. As discussed 
below under the Regulatory Flexibility Act, the economic impact on 
small entities is anticipated to be small. This rule makes available a 
testing procedure which would be used at the discretion of the 
permitting authority when compliance with State-adopted water quality 
standards necessitates a more sensitive method than those previously 
approved. This rule would impose no enforceable duty on any state, 
local or tribal governments or the private sector, nor would it 
significantly or uniquely affect them. It would not significantly 
affect them because any incremental costs incurred are small and it 
would not uniquely affect them because it would affect all size 
entities based on whether testing for mercury is otherwise required by 
a regulatory authority. Further, monitoring for small entities is 
generally expected to be less frequent than monitoring for larger 
entities. Therefore, today's rule is not subject to the requirements of 
sections 202, 203 and 205 of UMRA.

C. Regulatory Flexibility Act

    Under the Regulatory Flexibility Act (RFA), 5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA), EPA generally is required to conduct a regulatory flexibility 
analysis describing the impact of the regulatory action on small 
entities as part of rulemaking. However, under section 605(b) of the 
RFA, if EPA certifies that the rule will not have a significant 
economic impact on a substantial number of small entities, EPA is not 
required to prepare a regulatory flexibility analysis. Pursuant to 
section 605(b) of the Regulatory Flexibility Act, 5 U.S.C. 605(b), the 
Administrator certifies that this rule will not have a significant 
economic impact on a substantial number of small entities.
    This regulation approves a testing procedure for the measurement of 
mercury which EPA anticipates will be used by regulatory authorities 
when a permit limit has been set below the level of detection of 
previously approved methods. In developing this regulation, EPA 
considered the effects on small entities. Section 601(6) of the RFA 
defines small entity as small business, small governmental 
jurisdiction, and small organization. The small entities that might be 
affected by this rule include small governmental jurisdictions (that 
own POTWs) and small businesses with discharge permits for mercury at 
or below 200 ng/L. Of the 477 entities that we have identified with 
mercury limits at or below 200 ng/L, 143 are businesses, 38 are 
drinking water treatment plants in Puerto Rico, and 296 are POTWs.
    To evaluate the potential impact on small businesses, EPA first 
assumed that all of the 143 businesses were small. EPA assigned to each 
identified facility the approximate average revenue for a small 
business in the SIC code to which that facility belongs. If the 
facility is classified as a ``major'' discharger in the Permit 
Compliance System (PCS), EPA assumed incremental analytical monitoring 
costs of $5,200 per year. This assumption is based upon weekly 
monitoring for mercury at two sample locations using Method 1631, and 
assumes each facility will incur an incremental cost of $50 per sample 
(the high end of the range of incremental costs). If the facility is 
classified as a ``minor'' discharger in PCS, EPA assumed incremental 
analytical monitoring costs of $600 per year. This assumption is based 
upon monthly monitoring for mercury at one sample location using Method 
1631, and again assumes each facility will incur the high end 
incremental cost of $50 per sample. EPA then calculated the ratio of 
costs (using these upper-bound assumptions) to the assigned revenue to 
derive an upper-bound estimate of the impacts. The ratio is above 0.5 
percent for only three facilities--``major'' facilities, which may not 
be small businesses--and in all cases is below 4 percent. On average, 
the impacts were much lower. Specifically, the mean ratio for all of 
the facilities is 0.17 percent and the median ratio is 0.06 percent. 
Although PCS contains limitations data for over 20

[[Page 30432]]

percent of the ``minor'' dischargers, EPA believes that ``minor'' 
dischargers without limitations data in PCS would have a similarly low 
level of impact. No ``minor'' discharger is expected to experience an 
impact of more than 0.5 percent of revenues.
    Small governments are those representing jurisdictions of less than 
50,000 people. The 38 drinking water plants in Puerto Rico are state-
owned and thus are not small governments. To evaluate the impact on 
small POTWs, EPA looked at the potential impacts on two sizes of POTWs 
to represent both ``major'' and ``minor'' dischargers potentially 
affected by the regulation. Based on national estimates from the Census 
of Governments, local governments collect $79.31 per person in sewerage 
charges, which EPA assumed to be the average per capita revenue for 
POTWs from the population that they serve. On average, a POTW has a 
flow of 100 gallons per day for each person that it serves. EPA assumed 
that a POTW serving 1,000 people (having a flow of 100,000 gallons per 
day) would have revenues of $79,310 and incur costs of $600 (using the 
same assumptions as for ``minor'' businesses), which is 0.76 percent of 
its revenue. Similarly, EPA estimated that a POTW serving 10,000 people 
(having a flow of 1 million gallons per day, and thus being a major 
discharger) would have revenue of $793,100 and incur costs of $5,200 
(using the same assumptions as for ``major'' businesses), which is only 
0.66 percent of revenue.
    Based upon these estimates, EPA concludes that this rule will not 
have a significant economic impact on a substantial number of small 
entities.

D. Paperwork Reduction Act

    This rule contains no information collection requirements. 
Therefore, no information collection request has been submitted to the 
Office of Management and Budget (OMB) for review and approval under the 
Paperwork Reduction Act of 1995, 44 U.S.C. 3501 et seq.

E. Submission to Congress and the General Accounting Office

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this rule and other 
required information to the U.S. Senate, the U.S. House of 
Representatives and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is not a ``major rule'' as defined by 5 U.S.C. 
804(2). This rule will be effective July 8, 1999.

F. National Technology Transfer and Advancement Act

    As noted in the proposed rule, section 12(d) of the National 
Technology Transfer and Advancement Act of 1995 (NTTAA), Pub. L. 104-
113, section 12(d) (15 U.S.C. 272 note) directs EPA to use voluntary 
consensus standards in its regulatory activities unless to do so would 
be inconsistent with applicable law or otherwise impractical. Voluntary 
consensus standards are technical standards (e.g., materials 
specifications, test methods, sampling procedures, business practices) 
that are developed or adopted by voluntary consensus standards bodies. 
The NTTAA directs EPA to provide Congress, through the Office of 
Management and Budget (OMB), explanations when the Agency decides not 
to use available and applicable voluntary consensus standards. This 
rulemaking involves technical standards. Therefore, the Agency 
conducted a search to identify potentially applicable voluntary 
consensus standards. EPA's search of the technical literature revealed 
that there are no consensus methods for determination of mercury at 
these trace levels, although the American Society of Testing and 
Materials (ASTM) potentially is in the process of developing an 
analytical method for the determination of trace levels of mercury. If 
ASTM or another voluntary consensus standard body approves such a 
method and EPA believes that the method is suitable for compliance 
monitoring and other purposes, EPA will promulgate the method in a 
subsequent rule. As mentioned earlier, the Agency followed ASTM's 
Practice D 2777 (a voluntary consensus standard) in the design of EPA's 
interlaboratory method validation study for EPA Method 1631.

G. Executive Order 13045

    Executive Order 13045, ``Protection of Children from Environmental 
Health Risks and Safety Risks,'' (62 FR 19885, April 23, 1997) applies 
to any rule that: (1) Is determined to be ``economically significant'' 
as defined under E.O. 12866, and (2) concerns an environmental health 
or safety risk that EPA has reason to believe may have a 
disproportionate effect on children. If the regulatory action meets 
both criteria, the Agency must evaluate the environmental health or 
safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the Agency. EPA 
interprets E.O. 13045 as applying only to those regulatory actions that 
are based on health or safety risks, such that the analysis required 
under section 5-501 of the Order has the potential to influence the 
regulation. Although it has been determined that this rule is a 
``significant regulatory action'' under E.O. 12866, it is not 
economically significant and, therefore, E.O. 13045 does not apply. In 
addition, this rule does not establish an environmental standard 
intended to mitigate health or safety risks.

H. Executive Order 12875

    Under Executive Order 12875, ``Enhancing the Intergovernmental 
Partnership,'' EPA may not issue a regulation that is not required by 
statute and that creates a mandate upon a State, local or tribal 
government, unless the Federal government provides the funds necessary 
to pay the direct compliance costs incurred by those governments, or 
EPA consults with those governments. If EPA complies by consulting, 
E.O. 12875 requires EPA to provide to the Office of Management and 
Budget a description of the extent of EPA's prior consultation with 
representatives of affected State, local and tribal governments, the 
nature of their concerns, any written communications from the 
governments, and a statement supporting the need to issue the 
regulation. In addition, Executive Order 12875 requires EPA to develop 
an effective process permitting elected officials and other 
representatives of State, local and tribal governments ``to provide 
meaningful and timely input in the development of regulatory proposals 
containing significant unfunded mandates.''
    Today's rule does not create a mandate on State, local or tribal 
governments. States have been particularly supportive of EPA's efforts 
to approve a more sensitive test method for mercury. The rule does not 
impose any enforceable duties on these entities. This rule makes 
available a testing procedure for use when testing is otherwise 
required by a regulatory agency. Accordingly, the requirements of 
section 1(a) of Executive Order 12875 do not apply to this rule.

I. Executive Order 13084

    Under Executive Order 13084, ``Consultation and Coordination with 
Indian Tribal Governments,'' EPA may

[[Page 30433]]

not issue a regulation that is not required by statute, that 
significantly or uniquely affects the communities of Indian tribal 
governments, and that imposes substantial direct compliance costs on 
those communities, unless the Federal government provides the funds 
necessary to pay the direct compliance costs incurred by the tribal 
governments, or EPA consults with those governments. If EPA complies by 
consulting, E.O. 13084 requires EPA to provide to the Office of 
Management and Budget, in a separately identified section of the 
preamble to the rule, a description of the extent of EPA's prior 
consultation with representatives of affected tribal governments, a 
summary of the nature of their concerns, and a statement supporting the 
need to issue the regulation. In addition, Executive Order 13084 
requires EPA to develop an effective process permitting elected and 
other representatives of Indian tribal governments ``to provide 
meaningful and timely input in the development of regulatory policies 
on matters that significantly or uniquely affect their communities.''
    As described under the Regulatory Flexibility Analysis, today's 
rule does not significantly or uniquely affect the communities of 
Indian tribal governments. Further, this rule does not impose 
substantial direct compliance costs on Tribal governments. This rule 
makes available a testing procedure which would be used when testing is 
otherwise required by a regulatory agency to demonstrate compliance 
with water quality-based permit limits for mercury. Accordingly, the 
requirements of section 3(b) of Executive Order 13084 do not apply to 
this rule.

List of Subjects in 40 CFR Part 136

    Environmental protection, Analytical methods, Incorporation by 
reference, Monitoring, Reporting and recordkeeping requirements, Waste 
treatment and disposal, Water pollution control.

    Dated: May 28, 1999.
Carol M. Browner,
Administrator.

    In consideration of the preceding, USEPA amends 40 Code of Federal 
Regulations part 136 as follows:

PART 136--GUIDELINES ESTABLISHING TEST PROCEDURES FOR THE ANALYSIS 
OF POLLUTANTS

    1. The authority citation of 40 CFR part 136 continues to read as 
follows:

    Authority: Secs. 301, 304(h), 307, and 501(a), Pub. L. 95-217, 
Stat. 1566, et seq. (33 U.S.C. 1251, et seq.) (The Federal Water 
Pollution Control Act Amendments of 1972 as amended by the Clean 
Water Act of 1977).

    2. Section 136.3, paragraph (a), Table IB.--List of Approved 
Inorganic Test Procedures, is amended by revising entry 35 to read as 
follows:


Sec. 136.3  Identification of test procedures.

    (a) * * *
* * * * *

                              Table IB--List of Approved Inorganic Test Procedures
----------------------------------------------------------------------------------------------------------------
                                                       Reference (method number or page)
                              ----------------------------------------------------------------------------------
 Parameter, units and method                STD methods 18th
                                 EPA 1,35          ed.              ASTM            USGS \2\           Other
----------------------------------------------------------------------------------------------------------------
 
*                  *                  *                  *                  *                  *
                                                        *
35. Mercury--Total,\4\ mg/L:
    Cold vapor, manual, or...        245.1  3112 B..........  D3223-91........  I-3462-85.......      \3\ 977.22
    Automated................        245.2  ................  ................  ................  ..............
    Oxidation, purge and         \43\ 1631  ................  ................  ................  ..............
     trap, and cold vapor
     atomic fluorescence
     spectrometry (ng/L).
 
*                  *                  *                  *                  *                  *
                                                        *
----------------------------------------------------------------------------------------------------------------
Table 1B Notes:
\1\ ``Methods for Chemical Analysis of Water and Wastes,'' Environmental Protection Agency, Environmental
  Monitoring Systems Laboratory--Cincinnati (EMSL-CI), EPA-600/4-79-020, Revised March 1983 and 1979 where
  applicable.
\2\ Fishman, M.J., et al. ``Methods for Analysis of Inorganic Substances in Water and Fluvial Sediments'', U.S.
  Department of the Interior, Techniques of Water--Resource Investigations of the U.S. Geological Survey,
  Denver, CO, Revised 1989, unless otherwise stated.
\3\ ``Official Methods of Analysis of the Association of Official Analytical Chemists,'' methods manual, 15th
  ed. (1990).
\4\ For the determination of total metals the sample is not filtered before processing. A digestion procedure is
  required to solubilize suspended material and to destroy possible organic-metal complexes. Two digestion
  procedures are given in ``Methods for Chemical Analysis of Water and Wastes, 1979 and 1983.'' One (Section
  4.1.3), is a vigorous digestion using nitric acid. A less vigorous digestion using nitric and hydrochloric
  acids (Section 4.1.4) is preferred; however, the analyst should be cautioned that this mild digestion may not
  suffice for all sample types. Particularly, if a colorimetric procedure is to be employed, it is necessary to
  ensure that all organo-metallic bonds be broken so that the metal is in a reactive state. In those situations,
  the vigorous digestion is to be preferred making certain that at no time does the sample go to dryness.
  Samples containing large amounts of organic materials may also benefit by this vigorous digestion, however,
  vigorous digestion with concentrated nitric acid will convert antimony and tin to insoluble oxides and render
  them unavailable for analysis. Use of ICP/AES as well as determinations for certain elements such as antimony,
  arsenic, the noble metals, mercury, selenium, silver, tin, and titanium require a modified sample digestion
  procedure and in all cases the method write-up should be consulted for specific instructions and/or cautions.
Note to Table IB Note 4: If the digestion procedure for direct aspiration AA included in one of the other
  approved references is different than the above, the EPA procedure must be used. Dissolved metals are defined
  as those constituents which will pass through a 0.45 micron membrane filter. Following filtration of the
  sample, the referenced procedure for total metals must be followed. Sample digestion of the filtrate for
  dissolved metals (or digestion of the original sample solution for total metals) may be omitted for AA (direct
  aspiration or graphite furnace) and ICP analyses, provided the sample solution to be analyzed meets the
  following criteria:
 a. has a low COD (<20),
 b. is visibly transparent with a turbidity measurement of 1 NTU or less,
 c. is colorless with no perceptible odor, and
 d. is of one liquid phase and free of particulate or suspended matter following acidification.
* * * * *
\35\ Precision and recovery statements for the atomic absorption direct aspiration and graphite furnace methods,
  and for the spectrophotometric SDDC method for arsenic are provided in Appendix D of this part titled,
  ``Precision and Recovery Statements for Methods for Measuring Metals.''
* * * * *
\43\ The application of clean techniques described in EPA's draft Method 1669: Sampling Ambient Water for Trace
  Metals at EPA Water Quality Criteria Levels (EPA-821-R-96-011) are recommended to preclude contamination at
  low-level, trace metal determinations.


[[Page 30434]]

    3. Section 136.3 is amended by adding new paragraph (40) to read as 
follows:


Sec. 136.3  Identification of test procedures.

    (a) * * *
    (b) * * *
* * * * *
    (40) USEPA. 1999. Method 1631, Revision B, ``Mercury in Water by 
Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence 
Spectrometry.'' May 1999. Office of Water, U.S. Environmental 
Protection Agency (EPA 821-R-99-005). Available from: National 
Technical Information Service, 5285 Port Royal Road, Springfield, 
Virginia 22161. Publication No. PB99-131989. Cost: $25.50. Table IB, 
Note 43.
* * * * *
[FR Doc. 99-14220 Filed 6-7-99; 8:45 am]
BILLING CODE 6560-50-P