Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Mines, 53280-53293 [05-17802]

Agencies

• DEPARTMENT OF LABOR
• Mine Safety and Health Administration

[Federal Register Volume 70, Number 172 (Wednesday, September 7, 2005)]
[Proposed Rules]
[Pages 53280-53293]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-17802]



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Part III





Department of Labor





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Mine Safety and Health Administration



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30 CFR Part 57



Diesel Particulate Matter Exposure of Underground Metal and Nonmetal 
Mines; Proposed Rule

Federal Register / Vol. 70, No. 172 / Wednesday, September 7, 2005 / 
Proposed Rules

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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 57

RIN 1219-AB29


Diesel Particulate Matter Exposure of Underground Metal and 
Nonmetal Mines

AGENCY: Mine Safety and Health Administration (MSHA), Labor.

ACTION: Proposed rule; notice of public hearings; close of comment 
period; request for data.

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SUMMARY: We propose to revise the January 20, 2006 effective date of 
the existing diesel particulate matter (DPM) final concentration limit 
of 160 micrograms of total carbon (TC) per cubic meter of air 
(160TC[mu]g/m3) in the 2001 final rule ``Diesel 
Particulate Matter Exposure of Underground Metal and Nonmetal Miners,'' 
published in the Federal Register on January 19, 2001 (66 FR 5706). We 
are considering staggered effective dates for implementation of the 
final DPM limit, phased-in over a multi-year period, primarily based on 
feasibility issues that have surfaced since promulgation of the 2001 
final rule. We also propose to delete the existing provision that 
restricts newer mines from applying for an extension of time for 
meeting the final concentration limit. In addition we are seeking 
specific comments and data on an appropriate conversion factor for the 
final DPM limit, technological implementation issues, and the costs and 
benefits of this rule. Finally, in this proposed rule, we are 
interested in comments on the appropriateness of including in a final 
rule a provision for medical evaluation of miners required to wear 
respiratory protection and transfer of miners who have been determined 
by a medical professional to be unable to wear a respirator. Specific 
questions regarding these issues are discussed within the appropriate 
sections in the preamble. These questions are italicized for ease of 
the reader.

DATES: Public hearing dates and locations are discussed in the 
SUPPLEMENTARY INFORMATION section below. If you wish to make an oral 
presentation for the record, we ask that you submit your request at 
least 5 days prior to the hearing dates. Comments and other appropriate 
data for the record must be received by close of business on October 
14, 2005.

ADDRESSES: (1) To submit comments, please include RIN: 1219-AB29 in the 
subject line of the message and send them to us at either of the 
following addresses.
    Federal e-Rulemaking portal: Go to https://www.regulations.gov and 
follow the online instructions for submitting comments.
    E-mail: zzMSHA-comments@dol.gov. If you are unable to submit 
comments electronically, please identify them by RIN: 1219-AB29 and 
send them to us by any of the following methods.
    Fax: (202) 693-9441.
    Mail, hand delivery, or courier: MSHA, Office of Standards, 
Regulations, and Variances, 1100 Wilson Blvd., Rm. 2350, Arlington, VA 
22209-3939.
    (2) We will post all comments on the Internet without change, 
including any personal information they may contain. You may access the 
rulemaking docket via the Internet at https://www.msha.gov/regsinfo.htm 
or in person at MSHA's public reading room at 1100 Wilson Blvd., Rm. 
2349, Arlington, VA.
    (3) To receive an e-mail notification when we publish rulemaking 
documents in the Federal Register, subscribe to our list serve at 
https://www.msha.gov/subscriptions/subscribe.aspx.

FOR FURTHER INFORMATION CONTACT: For information contact Rebecca J. 
Smith, Acting Director of the Office of Standards, Regulations, and 
Variances, MSHA, 1100 Wilson Blvd., Arlington, Virginia 22209-3939. Ms. 
Smith can be reached at (202) 693-9440.

SUPPLEMENTARY INFORMATION:

Outline of Preamble

    This outline will assist the mining community in finding 
information in this preamble.

I. Public Hearings
II. Rulemaking Background
    A. First Partial Settlement Agreement
    B. Second Partial Settlement Agreement
III. Rulemaking History
    A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim 
and Final Concentration Limits
    B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit
    C. Final Rule Revising the Interim Concentration Limit
IV. Technological Feasibility
    A. Introduction
    B. Background
    C. Remaining Technological Feasibility Issues
V. Complexity of Developing an Appropriate Conversion Factor for the 
Final Concentration Limit
VI. Economic Feasibility
VII. Section 101(a)(9) of the Mine Act
VIII. Section-by-Section Analysis
    A. Section 57.5060(b)
    B. Effect of Eliminating Sec.  57.5060(c)(3)(i)
IX. Medical Evaluation and Transfer
X. Regulatory Impact Analysis
    A. Executive Order 12866
    B. Costs
    C. Benefits
XI. Regulatory Flexibility Act Certification
XII. Paperwork Reduction Act
XIII. Other Regulatory Considerations
XIV. Proposed DPM Rule Text

I. Public Hearings

    We will hold three public hearings on the proposed rule. The public 
hearings will be begin at 9 a.m., and will be held on the following 
dates and locations:

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             Date                      Location              Phone
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September 26, 2005............  Little America Hotel,     (801) 363-6781
                                 500 South Main
                                 Street, Salt Lake
                                 City, UT 84101.
September 28, 2005............  Clarion Hotel Sports      (816) 737-0200
                                 Complex, 9103 E.
                                 39th Street, Kansas
                                 City, MO 64133.
September 30, 2005............  Marriott Louisville       (800) 228-9290
                                 Downtown, 280 West
                                 Jefferson Street,
                                 Louisville, KY 40202.
------------------------------------------------------------------------

    If you wish to make an oral presentation for the record, we ask 
that you submit your request at least 5 days prior to the hearing 
dates. However, you do not have to make a written request to speak. Any 
unallotted time will be made available for persons making same-day 
requests.
    The hearings will begin with an opening statement from MSHA, 
followed by an opportunity for members of the public to make oral 
presentations to a panel. Speakers will speak in the order that they 
sign in. At the discretion of the presiding official, the time 
allocated to speakers for their presentation may be limited. Speakers 
and other attendees may also present information to the MSHA panel for 
inclusion in the rulemaking record.
    The hearings will be conducted in an informal manner. The hearing 
panel may ask questions of speakers. Although formal rules of evidence 
and cross examination will not apply, the presiding official may 
exercise discretion to ensure the orderly progress of the hearing and 
may exclude irrelevant or unduly repetitious material and questions.

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    A verbatim transcript of the proceedings will be included in the 
rulemaking record. Copies of this transcript will be available to the 
public, and can be viewed at https://www.msha.gov.
    We will accept post-hearing written comments and other appropriate 
data for the record from any interested party, including those not 
presenting oral statements, through close of business on October 14, 
2005.

II. Rulemaking Background

    On January 19, 2001 we published a final rule addressing the health 
hazards to underground metal and nonmetal miners from exposure to 
diesel particulate matter (DPM) (66 FR 5706). The rule established new 
health standards for these miners by requiring, among other things, use 
of engineering and work practice controls to reduce DPM to prescribed 
limits. It set an interim and final DPM concentration limit in the 
underground metal and nonmetal mining environment with staggered 
effective dates for implementation of the concentration limits. The 
interim concentration limit of 400TC [mu]g/m3 was 
to become effective on July 20, 2002. The final concentration limit of 
160TC [mu]g/m3 is scheduled to become effective 
January 20, 2006. In the 2001 final rule, we projected that the mining 
industry would meet the final concentration limit in their mines 
through the use of diesel particulate filtration devices, ventilation 
changes, and the turnover of equipment and engines to less polluting 
models (66 FR 5713, 5888).
    Several mining trade associations and individual mine operators 
challenged the final rule and the United Steelworkers of America (USWA) 
intervened in the case, which is now pending in the United States Court 
of Appeals for the District of Columbia Circuit. The parties agreed to 
resolve their differences through settlement negotiations with us and 
we delayed the effective date of certain provisions of the standard.

A. First Partial Settlement Agreement

    On July 5, 2001, as a result of an agreement reached in settlement 
negotiations, we published two notices in the Federal Register. One 
notice (66 FR 35518) delayed the effective date of Sec.  57.5066(b) 
related to tagging requirements in the maintenance standard. The second 
notice (66 FR 35521) proposed a rule to make limited revisions to Sec.  
57.5066(b) and added a new paragraph to Sec.  57.5067(b) ``Engines'' 
regarding the definition of the term ``introduced.'' We published the 
final rule on February 27, 2002 (67 FR 9180).

B. Second Partial Settlement Agreement

    Settlement negotiations continued on the remaining unresolved 
issues in the litigation, and on July 15, 2002, the parties finalized a 
written agreement (67 FR 47296, 47297). Under the agreement, the 
interim concentration limit of 400TC [mu]g/m3 
became effective on July 20, 2002, without further legal challenge. We 
afforded mine operators one year to develop and implement good-faith 
compliance strategies to meet the interim concentration limit, and we 
agreed to provide compliance assistance during this one-year period. We 
also agreed to propose rulemaking on several other disputed provisions 
of the 2001 final rule. The legal challenge to the rule was stayed 
pending completion of the additional rulemakings.
    On July 20, 2003, we began full enforcement of the interim 
concentration limit of 400TC [mu]g/m3. Our 
enforcement policy was also based on the terms of the second partial 
settlement agreement and includes the use of elemental carbon (EC) as 
an analyte to ensure that a citation based on the 400 TC concentration 
limit is valid and not the result of interferences (67 FR 47298). The 
policy was discussed with the DPM litigants and stakeholders on July 
17, 2003.

III. Rulemaking History

A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim and 
Final Concentration Limits

    On September 25, 2002, we published an Advance Notice of Proposed 
Rulemaking (ANPRM) (67 FR 60199). We noted in the ANPRM that the scope 
of the rulemaking was limited to the terms of the Second Partial 
Settlement Agreement and posed a series of questions to the mining 
community related to the 2001 final rule. We also stated our intent to 
propose a rule to revise the surrogate for the interim and final 
concentration limits and to propose a DPM control scheme similar to 
that included in our longstanding hierarchy of controls scheme used in 
our air quality standards (30 CFR 56/57.5001-.5006) for metal and 
nonmetal mines. In addition, we stated that we would consider 
technological and economic feasibility for the underground metal and 
nonmetal mining industry to comply with revised interim and final DPM 
limits. We determined at that time that some mine operators had begun 
to implement control technology on their underground diesel-powered 
equipment. Therefore, we requested relevant information on current 
experiences with availability of control technology, installation of 
control technology, effectiveness of control technology to reduce DPM 
levels, and cost implications of compliance with the 2001 final rule.

B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit

    In response to our publication of the ANPRM, some commenters 
recommended that we propose separate rulemakings for revising the 
interim and final concentration limits to give us an opportunity to 
gather further information to establish a final DPM limit, particularly 
regarding feasibility. In the subsequent notice of proposed rulemaking 
(NPRM) published on August 14, 2003 (68 FR 48668), we concurred with 
these commenters and notified the public in the NPRM that we would 
propose a separate rulemaking to amend the existing final concentration 
limit of 160TC [mu]g/m3. We also requested 
comments on an appropriate final DPM limit and solicited additional 
information on feasibility. The proposed rule also addressed the 
interim concentration limit by proposing a comparable PEL of 308 [mu]g/
m3 based on the EC surrogate and included a number of other 
provisions.

C. Final Rule Revising the Interim Concentration Limit

    We published the final rule revising the interim concentration 
limit on June 6, 2005 (70 FR 32868). This rule changed the interim 
concentration limit of 400 [mu]g/m\3\ measured by TC to a comparable 
PEL of 308 [mu]g/m\3\ measured by EC. The rule requires our 
longstanding hierarchy of controls that is used for our other exposure-
based health standards at metal and nonmetal mines, but retains the 
prohibition on rotation of miners for compliance. Furthermore, the 
rule, among other things, requires us to consider economic as well as 
technological feasibility in determining if operators qualify for an 
extension of time in which to meet the final DPM limit, and deletes the 
requirement for a control plan.
    Currently, the following provisions of the DPM standard are 
effective: Sec.  57.5060(a), establishing the interim PEL of 308 
micrograms of EC per cubic meter of air which is comparable in effect 
to 400 micrograms of TC per cubic meter of air; Sec.  57.5060(d), 
Addressing control requirements; Sec.  57.5060(e), Prohibiting rotation 
of miners for compliance with the DPM standard; Sec.  57.5061, 
Compliance determinations; Sec.  57.5065, Fueling practices; Sec.  
57.5066,

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Maintenance standards; Sec.  57.5067, Engines; Sec.  57.5070, Miner 
training; Sec.  57.5071, Exposure monitoring; and, Sec.  57.5075, 
Diesel particulate records.

IV. Technological Feasibility

A. Introduction

    When we promulgated the 2001 final rule, we determined that control 
technologies would be available by January 20, 2006 to reduce DPM 
concentrations to 160TC [mu]g/m\3\ micrograms in all types 
of underground metal and nonmetal mines. In the 2001 final rule, we 
established a new compliance scheme for these mine operators to 
implement that was distinguishable from that of our other exposure-
based health standards by requiring that miners' exposures be reduced 
to a full-shift equivalent environmental or concentration limit where 
miners work or travel. Historically, our metal and nonmetal exposure-
based health standards have been based on a miner's full-shift personal 
exposure and required that mine operators reduce miners' exposures to 
hazardous chemical substances by establishing a hierarchy of controls 
utilizing feasible engineering and administrative controls supplemented 
by respiratory protection, if necessary. Since, we were regulating DPM 
for the first time we needed a tool to help us to determine whether the 
mining industry was capable of meeting the interim and final 
concentration limits of the 2001 final rule using a combination of 
engineering and work practice controls. We also needed a compliance 
assistance tool to help mine operators with selection of feasible 
controls from technology unfamiliar to the mining industry. 
Consequently, we developed the Estimator.
    The Estimator mathematically calculates the effect of any 
combination of engineering and ventilation controls on existing DPM 
concentrations in a given production area of a mine. This model is in 
the form of a spreadsheet template that permits instant display of 
outcomes as inputs are altered. Depending on the amount and type of 
equipment an operator uses, mining companies could use the Estimator to 
evaluate the effectiveness of these controls prior to purchasing and 
installing such controls. We encouraged mine operators to use this tool 
to assist them in making their decisions regarding the appropriate 
controls for their mines in meeting the 2001 concentration limits.
    In the preamble to the 2001 final rule, we included data from our 
studies where we evaluated emissions generated by diesel powered 
equipment in several diverse underground mining operations which 
included an underground limestone mine, an underground salt mine, and 
an underground gold mine. In each mine, we concluded that the necessary 
combination of controls was available to reduce DPM concentrations well 
below the final concentration limit. Based on these studies, we 
concluded that engineering and work practice controls were available to 
reduce DPM concentrations in all underground metal and nonmetal mines 
to the required limits. We also distributed to the mining community our 
publication of ``Practical Ways to Control Exposure to Diesel Exhaust 
in Mining--a Toolbox'' which addresses various categories of available 
DPM controls. These categories of controls include use of low emission 
engines, low sulfur fuel, aftertreatment devices, ventilation, enclosed 
cabs, engine maintenance, work practices and training, fleet 
management, and respiratory protective equipment (66 FR 5712-13). 
Furthermore, we also examined information regarding types of engines 
and equipment found in underground metal and nonmetal mines along with 
their various ventilation systems and concluded that the 2001 final 
rule was technologically feasible for the mining industry (66 FR 5889).
    We also concluded that the 2001 final rule was economically 
feasible but recognized the broad impact of the rule on the underground 
metal and nonmetal sector of the mining industry. We estimated that the 
annual cost of the 2001 final rule for these mines would be $25.1 
million. The cost for an average underground metal and nonmetal mine 
was projected to be approximately $128,000 annually primarily for 
investment in equipment to meet the interim and final concentration 
limits. In reaching our cost estimates, we anticipated that the interim 
concentration limit would be met primarily with the use of diesel 
particulate filters (DPFs), environmental cabs, and ventilation; and 
the final concentration limit would be met with expanded use of DPFs, 
ventilation, and turnover in equipment to less polluting models (66 FR 
5713, 5888).
    We included a provision in the 2001 final rule to allow an 
additional two years for mines experiencing difficulty in reducing DPM 
levels to the final concentration limit due to technological 
constraints (66 FR 5861). The June 6, 2005, final rule on the interim 
limit subsequently revised the extension requirement to provide one 
year, renewable, extensions to comply with the final limit, based on 
economic or technological infeasibility, but continues to prohibit 
newer mines from applying for extensions (70 FR 32966).
    Following promulgation of the 2001 final rule, we agreed to engage 
in a joint MSHA/industry 31-Mine Study to, among other things, assess 
the technological and economic feasibility of underground metal and 
nonmetal mine operators to achieve compliance with the interim and 
final DPM concentration limits. Feasibility at each of the 31 mines was 
determined using the Estimator. The analyses were based on the highest 
DPM sample result obtained at each mine and all major DPM emission 
sources at each mine plus spare equipment. On January 6, 2003, we 
issued our final report entitled, ``MSHA'S Report on Data Collected 
during a Joint MSHA/Industry Study of DPM Levels in Underground Metal 
and Nonmetal Mines.'' With regard to feasibility of compliance with 
both the interim and final concentration limits, we concluded in the 
study that it may be both technologically and economically feasible for 
metal and nonmetal underground mines to comply with the 2001 rule. At 
that time, however, we acknowledged our limited in-mine documentation 
on implementation of DPM control technology with issues such as 
retrofitting and regeneration of filters. Consequently, we committed to 
continue to consult with the National Institute for Occupational Safety 
and Health, industry and labor representatives on the availability of 
practical mine worthy filter technology. NIOSH peer reviewed our final 
report of the 31-Mine Study (70 FR 32870-73).
    Furthermore, by letter to MSHA dated June 25, 2003, NIOSH stated 
that:

    Operators will need to make informed decisions regarding filter 
selection, retrofitting, engine and equipment deployment, operation, 
and maintenance, and specifically work through issues such as in-use 
efficiencies, secondary emissions, engine backpressure, DPF 
regeneration, DPF reliability and durability. NIOSH is of the 
opinion that these issues can be solved if the informed decisions 
mentioned above are made. (70 FR 32923)

    In the 2005 rulemaking on the interim limit, we revised our 
approach to reducing DPM levels by establishing our longstanding 
hierarchy of controls used for regulating our other exposure-based 
health standards at metal and nonmetal mines. Also, we changed the 
concentration limit to a permissible exposure limit whereby we measure 
a miner's personal exposure. The Estimator became less significant from 
our perspective in demonstrating feasibility since the 2005 rulemaking

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record included more extensive evidence on the ability of the mining 
industry to meet the interim limit in 2005. Specifically, our 
rulemaking record included: our final report on the 31-Mine Study; 
NIOSH's peer review of the 31-Mine Study; results from our baseline 
sampling at mines covered under the DPM standard; results of our 
comprehensive compliance assistance work at mining operations with 
implementation issues affecting feasibility; NIOSH's conclusions on the 
performance of the SKC sampler and the availability of technology for 
control of DPM; NIOSH's Diesel Emissions Workshops in 2003 in 
Cincinnati and Salt Lake City; the Filter Selection Guide posted on the 
MSHA and NIOSH web sites; MSHA's final report on DPM filter efficiency; 
NIOSH's report titled, ``Review of Technology Available to the 
Underground Mining Industry for Control of Diesel Emissions'; and, the 
NIOSH Phase I Isozone study titled, ``The Effectiveness of Selected 
Technologies in Controlling Diesel Emissions in an Underground Mine--
Isolated Zone Study at Stillwater Mining Company's Nye Mine,'' all of 
which were developed following promulgation of the 2001 DPM final rule 
(70 FR 32916).
    To attain the interim DPM limit, mine operators are required to 
install, use, and maintain engineering and administrative controls to 
the extent feasible. When these controls do not reduce a miner's 
exposure to the DPM limit, controls are infeasible, or controls do not 
produce significant reductions in DPM exposures, operators must 
continue to use all feasible engineering and administrative controls 
and supplement them with respiratory protection. When respiratory 
protection is required under the final standard, mine operators must 
establish a respiratory protection program that meets the specified 
requirements. At this time, we believe that this compliance approach 
coupled with the time-frame for complying with the phased-in limits 
provides mine operators with maximum flexibility in compliance. We 
believe that this current compliance approach which incorporates the 
industrial hygiene concept of a hierarchy of controls scheme for 
implementing DPM controls would result in feasibility of compliance 
with each of the phased-in limits contained in this proposal. However, 
we continue to acknowledge that compliance difficulties may be 
encountered at some mines due to implementation issues and the cost of 
purchasing and installing certain types of controls.
1. MSHA's 2001 Assumptions Regarding Compliance With the Final 
Concentration Limit
    The assumptions that we used in 2001 in support of our cost 
estimates included:

    (a) Fifty percent of the fleet will have new engines (these new 
engines do not impact cost of the rule) * * * Moreover, due to EPA 
[Environmental Protection Agency] regulations which will limit DPM 
emissions from engines used in surface construction, surface mining, 
and over-the-road trucks (the major markets for heavy duty diesel 
engines), the market for low tech ``dirtier'' engines will dry up * 
* * (b) one hundred percent of the production equipment and about 
fifty percent of the support equipment will be equipped with 
filters; (c) about thirty percent of all equipment will need to be 
equipped with environmentally controlled cabs; (d) twenty three 
percent of the mines would need new ventilation systems (fans and 
motors); (e) forty percent of the mines will need new motors on 
these fans; and (f) thirty two percent of the mines will need major 
ventilation upgrades (66 FR 5889-90).

    Furthermore, we concluded that it would not be feasible to require 
this sector, as a whole, to lower DPM concentrations further, or to 
implement the required controls more swiftly (66 FR 5888).
2. Reasons Why the 2001 Assumptions Are Now Being Questioned.
    During the 4\1/2\ years since the 2001 final rule was promulgated, 
the mining industry and MSHA have gained considerable experience with 
the implementation, use, and cost of DPM control technology. Miners' 
DPM exposures have also have declined significantly from a mean of 
808DPM [mu]g/m\3\ (646TC [mu]g/m\3\ [mu]g/m\3\ 
equivalent) prior to the implementation of the standard, to a mean of 
233TC [mu]g/m\3\ based on current enforcement sampling. The 
industry, however, is encountering economic and technological 
feasibility issues with DPM controls as they strive to reduce levels 
below the interim limit. When we established the 2001 final limit, we 
were expecting some mine operators to encounter difficulties 
implementing control technology because the rule was technology 
forcing. We projected that by this time, practical and effective filter 
technology would be available that could be retrofitted onto most 
underground diesel powered equipment. However, as a result of our 
compliance assistance efforts and through our enforcement of the 
interim limit, we have become aware that this assumption may not be 
valid. The applications, engineering and related technological 
implementation issues that we believed would have been easily solved by 
now are more complex and extensive than previously thought.
    Although DPF systems have been proven to be highly effective in 
reducing elemental carbon, mines are currently experiencing problems 
with selection and implementation of DPF systems for complying with the 
interim limit. Since the final limit will require mines to install more 
DPF systems, these selection and implementation problems will extend 
over a large portion of the mining industry. At this time we believe 
that solutions to the problems of selection and implementation have not 
proceeded as quickly as anticipated since promulgation of the 2001 
final rule and many mines will not be able to achieve the final limit 
by January 20, 2006. Some of the implementation and operational 
difficulties encountered with the controls are discussed in the 
sections below.
    We seek additional information regarding technological difficulties 
and whether they will increase the cost to comply with the final 
concentration limit above that estimated in the 2001 final rule. We are 
particularly interested in whether mine operators have attempted to 
institute DPF systems that are impractical or have failed to work for 
their mining operations. We wish to know what types and sizes of DPFs 
have been evaluated, what types of equipment have been fitted with 
DPFs, what types and horsepower of engines were installed on the 
equipment, details concerning monitoring of equipment exhaust 
temperatures prior to specifying a DPF for a given application, whether 
DPF installations include a provision for backpressure monitoring, DPF 
maintenance intervals, DPF life, the results of any DPF failure mode 
analysis, DPM reductions obtained, and any other data related to in-
mine experiences with DPFs on underground metal and nonmetal mining 
equipment.
    We believe that wider use of alternative fuels and filter 
technology can make the 160TC [mu]g/m\3\ final limit 
feasible if a staggered phase-in approach is adopted. By lowering the 
exposure limit in intervals over five years beginning in January 2007, 
market forces should have sufficient time and incentive to adjust to 
the new standard. Specifically, a reliable alternative fuel 
distribution system should induce mine operators to adopt this 
relatively low-cost method to achieve compliance. The development and 
distribution of alternative fuels is also encouraged by existing tax 
credits. We believe that regional distribution networks are

[[Page 53284]]

beginning to emerge. We seek data on alternative fuel distribution 
systems.
    Retrofit options for self-cleaning filters should increase as the 
filter manufacturers become assured of a reliable market for the 
devices. Use of newer equipment with cleaner engines will also increase 
as older equipment is retired from service. We anticipate that this 
staggered approach will provide the needed time to resolve these 
logistical and operational issues, and consequently, may not increase 
our 2001 projection of the cost of compliance with the rule. During 
this phase-in, we will continue to work with the Diesel Partnership 
(discussed below) and the mining industry to address the DPF selection 
and implementation problems and identify effective solutions for the 
diverse metal and nonmetal mining environment.
    Additionally, we request comments on the percentage of diesel 
equipment, by mine size, in metal and nonmetal mines that currently 
have newer, low DPM emitting engines such as EPA Tier I and Tier 2 
compliant engines. Our 2001 cost estimates were based, in part, on the 
assumption that by the effective date of the final limit, 50% of the 
diesel equipment fleet would have new engines (66 FR 5889). We are 
interested in whether our 2001 assumption was accurate. If the 
percentage is lower than originally estimated, it may require the 
industry to rely even more heavily on filters and other types of 
controls at added costs. Relying on DPFs to be installed on older, 
higher DPM emitting engines may also introduce additional 
implementation issues since DPF manufacturers normally do not recommend 
adding DPFs to older engines. Although we recognize various types of 
controls that mine operators could use to reduce miner exposure to DPM, 
we believe that turnover in equipment to less polluting models and the 
use of DPFs would be the primary method of achieving compliance with 
the final DPM limit.
    We also recognize promising advances in alternative fuel technology 
since the 2001 final rule was promulgated. These fuels can be extremely 
effective in reducing DPM emissions. Additionally, the fuels would be 
in tune with recent U.S. initiatives towards greater energy 
independence. On October 22, 2004, President Bush signed into law a 50-
cent-per-gallon tax credit for producers of bio-diesel. He also 
extended federal tax credits for ethanol through 2007 as part of H.R. 
4520, also known as the American Jobs Creation Act of 2004 (Pub. L. 
108-357).
    Currently, however, logistical problems exist with the distribution 
of these fuels to remote mining areas, and the effect of these fuels on 
power output and operation at high altitude needs to be addressed more 
fully.
    Although MSHA, industry, and the Diesel Partnership are actively 
working to address these concerns, additional time may be needed to 
find effective solutions for the implementation of DPM controls.

B. Background

1. Diversity of Underground Mines Affected By the Final DPM 
Concentration Limit
    The metal and nonmetal mining industry has 177 underground mines 
that use numerous pieces of diesel powered equipment, widely 
distributed throughout each mining operation. These mines employ an 
array of mining technologies to produce commodities including metals 
such as lead, zinc, platinum, gold, silver, etc. Also, there are 
different types of nonmetal mines that produce stone products such as 
limestone, dolomite, sandstone, and marble. Other underground nonmetal 
mines produce clay, potash, trona, soda ash, and salt. Not only do 
these mines vary in the commodities that they produce, but they also 
use different mine designs and mining techniques such as room and 
pillar mining and stope mining. Some of these mines are large, complex 
multilevel mines, while others are small adit-type mines. Ventilation 
levels in these mines also vary widely. Many limestone mines have only 
natural ventilation with variable air movement, whereas trona mines 
have high ventilation rates to dilute and remove methane gas released 
in the mining process. There are also deep metal mines with multiple 
levels that have far less ventilation than that found in underground 
trona mines. Furthermore, many metal and nonmetal mines are located in 
remote areas of the country, at high altitudes, or are subject to 
extremely hot or cold environments. Considering these factors as a 
whole, we have found that there is no single solution to control 
technology that would be effective for all metal and nonmetal mines in 
significantly reducing current DPM levels to or below the final DPM 
concentration limit of 160TC micrograms.
2. Work of the M/NM Diesel Partnership (the Partnership)
    Since promulgation of the January 2001 final rule, we have worked 
with a Partnership that is composed of representatives from the 
National Institute for Occupational Safety and Health (NIOSH), industry 
trade associations, and organized labor. We are not a member of the 
Partnership because of our ongoing DPM rulemaking activities. The 
primary purpose of the Partnership is to identify technologically and 
economically feasible controls using existing and available technology 
that can be retrofitted onto existing diesel powered equipment in 
underground metal and nonmetal mines to reduce diesel particulate 
matter emissions to, or below, our interim and final limits.
    The Partnership has been actively involved with NIOSH in its work 
on diesel particulate control technology including its isolated zone 
studies at the Stillwater Mine in Montana. NIOSH has published the 
following reports of its work with the Partnership: ``The Effectiveness 
of Selected Technologies in Controlling Diesel Emissions in an 
Underground Mine--Isolated Zone Study at Stillwater Mining Company's 
Nye Mine (Phase I Study);'' ``An Evaluation of the Effects of Diesel 
Particulate Filter Systems on Air Quality and Personal Exposure of 
Miners at Stillwater Mining Case Study: Production Zone (Phase II 
Study);'' and, ``The Effectiveness of Reformulated Fuels and 
Aftertreatment Technologies in Controlling Diesel Emissions (Phase 
III--A Study in an Isolated Zone at Stillwater Mining Company's Nye 
Mine August 31-September 11, 2004).'' NIOSH stated in its conclusion to 
the Phase III study that:

    This study did not address the important critical path of 
economic and technical aspects relating to implementation of the 
studied technologies into underground mines. The successful 
implementation of control technologies is predicated on addressing 
issues which are relatively unique to each mine and even to 
individual applications within a given mine. Most of these technical 
and operational issues could be investigated through a series of 
long-term field studies where control technologies would be wisely 
selected and optimized for the applications, performance of the 
technologies would be continuously monitored and the effects of the 
controls on concentrations of diesel pollutants in the mine air 
would be periodically assessed. The findings of such studies would 
allow operators to make informed decisions regarding the selection, 
optimization and implementation of control technologies for its 
applications and maximize the benefits of using those technologies. 
It is recommended that these studies be designed and undertaken 
under the leadership of the Metal/Nonmetal Diesel Partnership.

    On-going NIOSH diesel research related to the Partnership includes 
a contract that the NIOSH Pittsburgh Research Laboratory issued to 
Johnson

[[Page 53285]]

Matthey Catalyst to develop a system to control nitrogen dioxide 
(NO2) emissions from diesel-powered underground mining 
vehicles equipped with the Johnson Matthey's Continuously Regenerating 
Trap (CRT[supreg]) system. This system promotes regeneration at lower 
temperatures and is widely used in urban bus applications. If the 
results of laboratory evaluations show that a system is suitable for 
use in underground mining, NIOSH would continue studying this control 
technology with a long-term field evaluation in an underground mine.

C. Remaining Technological Feasibility Issues

    In January 2001, we concluded that technology existed to sample 
accurately for DPM with a TC method and to bring DPM levels to the 160 
TC level by January 2006 (66 FR at 5889). We further concluded that if 
any particular mine found unforeseen technological barriers to meeting 
the January 2006 deadline, it could apply for an extension of up to two 
additional years to comply with the 160 limit (66 FR at 5889). Our 
discussion of technological feasibility in support of the interim PEL 
of 308EC [mu]g/m\3\ in the June 6, 2005 final rule concluded 
that it was technologically feasible to reduce underground miners' 
exposures to the interim PEL by using available engineering control 
technology and various administrative control methods. In fact, our 
testing at Kennecott Minerals Green's Creek Mine showed that ceramic 
diesel particulate filters (DPFs) were capable of reducing diesel 
exposures by 95%. However, we acknowledged that compliance difficulties 
may be encountered at some mines due to implementation issues and the 
cost of purchasing and installing certain types of controls. 
Specifically, implementation issues may adversely affect the 
feasibility of using DPFs to reduce exposures despite the results 
reported in NIOSH's Phase I Isozone Study.
    Our experience since January 2001 has raised questions on 
technological feasibility for the mining industry as a whole, rather 
than for a small number of individual mines, to meet the 160 TC 
concentration limit by January 20, 2006. When we conducted our baseline 
sampling in 2002 and 2003, we found that over 75% of the underground 
mines covered by the 2001 final rule have levels that would exceed the 
final concentration limit of 160TC micrograms. Our current 
enforcement data indicate that approximately 65% of the underground 
mines covered by the 2001 final rule have levels that would exceed the 
final concentration limit. Although exposures have decreased with 
implementation of controls and enforcement of the interim concentration 
limit, we have tentatively concluded that the 160TC 
microgram final concentration limit presents a significant challenge to 
a substantial number of underground mine operators and compliance may 
not be feasible by January 2006. That conclusion is supported by our 
current enforcement sampling results that indicate that many mining 
operations have exposures above the 160TC concentration 
limit, and availability of effective control technology that will 
reduce exposures to the final limit is speculative at this time. 
Moreover, comments from industry trade associations and individual mine 
operators in the post-January 2001 rulemakings recommended that we 
repeal the 160 limit as technologically infeasible. Organized labor, on 
the other hand, has recommended that a limit below 160 is 
technologically feasible. We request comments on whether compliance is 
technologically feasible by January 2006 and the appropriateness of a 
multi-year phase-in of the final limit. We also request comments and 
data on when the technology will be feasible. Specific technological 
implementation issues are discussed in more detail in the following 
subsections C.1 through C.4.
    We also request comments on whether compliance difficulties may 
lead to another problem by requiring a large number of miners to wear 
respirators until feasible controls are fully implemented. We have 
never had a standard that resulted in a significant percentage of the 
workforce being required to wear respiratory protection, and we are 
concerned about the impact on worker acceptance of the rule and about 
mine operators' ability to remain productive. We are interested in 
public comment on how many miners would need to wear respirators to 
comply with the 2001 final limit and proposed multi-year phase-in of 
the final limit, and whether in each case they would need to wear 
respirators for their entire work shift, whether this amount of 
respirator usage is practical, and any other comments or observations 
concerning this issue.
1. Implementation of Available DPFs
    We continue to project that many mine operators will have to use 
DPFs to reduce DPM levels to the final concentration limit. The mining 
industry maintains that while some operators are using DPFs to control 
miners' exposures to the interim PEL, it is infeasible for them to 
further reduce miners' exposures through expanded use of DPFs.
    While passive DPF regeneration systems are preferred over active 
regeneration systems, many pieces of mining equipment do not have duty 
cycles that will consistently support passive regeneration. Passive 
regeneration is the process where the exhaust gas temperature produced 
by the engine is sufficient to burn off the collected DPM on the DPF. 
Passive regeneration is normally preferred because a DPF can be 
installed on a machine, and the operator does not have to be concerned 
with removing the DPF on a routine schedule that may occur at the end 
of every shift. However, passive regeneration does require the machine 
operator to monitor the engine's exhaust gas backpressure. As the DPF 
loads up with DPM, the inability of the exhaust gas to burn off the DPM 
allows the backpressure to increase. Increasing the backpressure above 
the manufacturer's specifications can cause engine and DPF damage. We 
request information on the number of currently installed passive 
regeneration DPF filters. Also, we are interested in the methods used 
by the industry to match a passive regeneration DPF to a machine. 
However, we are aware that two identical machines operating in two 
different mines may not both be able to use passive regeneration. We 
would be interested in comments about practical experience with these 
implementation issues.
    If passive regeneration is infeasible, active regeneration is an 
alternative. Active regeneration depends on an external heat source for 
burning off the DPM. Mine operators have informed us that some mining 
operations cannot utilize active regeneration due to physical size of 
filters, machine down time, or the cost associated with underground 
regeneration stations required for DPF regeneration. We request that 
commenters submit information from the mines that are utilizing active 
regeneration including data regarding the benefits and the 
practicability of active regenerating filters.
    Engine emissions and exhaust flows also affect the size of the DPF 
that needs to be installed. Both of these factors can affect both 
passive and active regeneration. If the DPF is undersized for a 
particular application due to high DPM emissions or high exhaust flows, 
a passive or active DPF system may not make it through the entire shift 
before it must be taken out of service for regeneration because of the 
high backpressure.

[[Page 53286]]

    While some of the mining industry has made improvements by 
replacing older engines with newer engines in order to reduce DPM 
emissions, we believe this has occurred mostly for the larger 
horsepower engines, greater than 150 hp. Smaller engines normally found 
in the support equipment have not had DPM reductions equivalent to the 
larger engines. Since we estimated that 50% of the support equipment 
would probably need DPFs for compliance with the final limit (66 FR 
5889-90), the higher DPM emissions from the engines used in support 
equipment can further complicate the impact on compliance. The mining 
industry has stated that it needs additional time to further evaluate 
the proper sizing of DPF systems for both passive and active 
regeneration.
    We seek further comment regarding these technological 
implementation issues as they affect feasibility of compliance with the 
final concentration limit including the practicality of available DPM 
control technology. We request that the mining community specifically 
address issues surrounding off-board regeneration: back pressure build 
up; frequency of the necessity to clean DPFs; the difficulty of 
placement of regeneration stations; and information on the extent to 
which diesel powered equipment accommodates a retrofit of the DPF.
2. Benefits of On-Board Regeneration
    a. ArvinMeritor[supreg] System. The ArvinMeritor[supreg] system, 
which utilizes active regeneration of the DPF, offers great potential 
for underground mines in further reducing DPM exposures. The 
ArvinMeritor[supreg] system utilizes an on-board fuel burner system to 
regenerate DPFs. This system actively regenerates the filter media 
during normal equipment operations by causing the fuel to ignite the 
burner and thereby increase the exhaust temperature in the filter 
system. Consequently, this system does not require the host vehicle to 
travel to a regeneration station to regenerate the DPF. The condition 
of the DPF is monitored via sensors. While this product was 
successfully evaluated at Stillwater's Nye Mine, we have recently 
learned that the manufacturer has decided to concentrate on working 
with Original Equipment Manufacturers (OEMs) where they would be 
selling 50 units or more to one customer rather than selling one or two 
units per customer.
    b. Johnson Matthey's CRT[supreg] System for DPM reduction (Johnson 
Matthey). As stated above, passive regeneration works by using the 
exhaust gas generated by the engine to burn the DPM. Normally, DPF 
manufacturers utilize catalyst technology to lower the temperature 
needed for successful passive regeneration. By lowering the exhaust gas 
temperature needed for passive regeneration, a broader range of 
machines will have the necessary duty cycle to generate the exhaust gas 
temperature needed to burn the DPM. However, when a platinum coating is 
used as the catalyst, it can also increase the nitrogen dioxide 
(NO2) emissions from the engine exhaust. In mines with low 
ventilation rates, the increased NO2 emissions can also 
result in increased NO2 exposures to potentially dangerous 
levels for miners. We discuss this issue in the final rule on the 
interim PEL (70 FR 32924-26). Therefore, other methods for passive 
regeneration are being developed to resolve these issues.
    In 2004, the NIOSH Pittsburgh Research Laboratory issued a contract 
to Johnson Matthey to develop a system that can regenerate at lower 
exhaust gas temperatures and control NO2 emissions. The 
system is based on Johnson Matthey's CRT[supreg] system and promotes 
regeneration at lower temperatures. Such DPFs are widely used in urban 
bus applications and are capable of passively regenerating DPFs at the 
temperatures commonly seen in the exhausts of underground mining 
equipment (above 250 [deg]C for at least 40% of the operation time).
    The laboratory evaluation of the systems is being executed under 
NIOSH contract by the Center for Diesel Research (CDR) at the 
University of Minnesota. The objective is to examine performance and 
suitability of the systems relative to heavy-duty diesel engines in 
underground mining applications, with specific focus on the 
effectiveness of controlling NO2. If the results of 
laboratory evaluations show that the system is suitable for use in 
underground applications, NIOSH would continue to study this promising 
control with a long-term field evaluation in an underground mine 
environment. We request comments from the mining community regarding 
the foreseeable utility of these and other new control technologies for 
reducing DPM levels in underground metal and nonmetal mines.
3. Operators' Limited Access to Alternative Fuels and Ultra Low-Sulphur 
Fuels
    During our compliance assistance efforts, we observed mines with 
several applications of alternative fuels, including water emulsion 
fuels and bio-diesel fuels both of which are EPA approved fuels. We 
subsequently tested these alternative fuels to determine if they could 
decrease tailpipe DPM emissions. In each application the change to an 
alternative fuel had a positive impact on reducing engine emissions and 
miners' exposures to DPM. In some cases, reductions of 50 to 80+ 
percent were measured. While we found notable benefits, the use of 
alternative fuels can also cause equipment operation issues for mine 
operators. These operational issues have included initial clogging of 
the fuel filters when bio-diesel is used, reduction of horsepower with 
the use of water emulsion fuels, and management of proper fueling of 
the correct fuel into specific machines. While these operational issues 
could be overcome, each mine has to work through implementation issues 
on a case-by-case basis.
    The most common problem with alternative fuels is lack of 
geographic proximity of most mines to a fuel distributor. Fuel 
distribution centers tend to be near large cities. As a result, 
alternative fuels need to be transported to mine sites, in some cases 
significantly increasing costs. Fuel manufacturers are building 
distribution centers near mining areas to reduce the transportation 
costs, but these centers will take some additional time to complete. 
Limited distribution is also a feasibility issue for metal and nonmetal 
mine operators who seek to obtain ultra low sulfur fuel. However, as 
discussed elsewhere in this preamble, the commercial availability of 
ultra low sulfur fuel will increase during 2006 and beyond when on-
highway vehicles in the United States will be required by the EPA to 
use only this type of diesel fuel.
    a. Water Emulsion Fuels. Water emulsion fuels, such as PuriNox, are 
blends of diesel fuels and water. The water is held in suspension with 
a surfactant. The water in the fuel reduces the engine combustion 
temperature resulting in reduced NO2 and reduced DPM 
emissions. However, the added water also reduces the engine's 
horsepower. While the per gallon price of the water emulsion fuel is 
the same as standard fuel, we are aware of increases in engine 
consumption of these fuels by as much as 15 percent. However, continued 
increased use in mines is currently limited due to lack of fuel 
availability in most mining regions. Manufacturers of this fuel must 
install centralized blender facilities in order to make the fuel more 
available and economically feasible for use by the metal and nonmetal 
mining industry.
    Some fuel system issues have also been observed with some engines 
using water emulsion fuels. One issue appears

[[Page 53287]]

to be with the use of very efficient water separators used on engine 
fuel systems to remove water from the fuel lines. A very efficient 
water separator will actually remove the water from the emulsion, thus 
affecting the engine's performance. An engine manufacturer that has 
experienced this with its engines has recommended replacing the more 
efficient water separator with a less efficient one.
    Another issue identified by some mine operators is that some small 
machines cannot run, or run poorly, on this fuel. We are not aware of 
any testing that has been done to prove or disprove this. This may or 
may not be due to less complex fuel systems that cannot handle a change 
in fuel properties. We request any information that would help a mine 
operator determine if certain machines in a fleet cannot run 
efficiently on this type of fuel.
    Since water emulsion fuels have been associated with horsepower 
loss, mines will have to determine through their own in-mine test if 
their machines can continue to operate efficiently even with the power 
loss. Some situations where the power loss could affect a machine's 
productivity occur at multilevel underground mines at high altitudes. 
Also, mines that require the use of permissible engines with pre-
chamber combustion, such as the metal and nonmetal gassy mines, may 
need to determine any additional effects on these types of engines. 
These mines may need additional time to assess the impact of the 
elevation and grade on power loss. We request comments on the mining 
industry's experience with using water emulsion fuels to reduce DPM 
exposures.
    b. Bio-Diesel Fuels. While bio-diesel fuels are more readily 
available than water emulsion fuels, there has not been a consistent 
supply or standard cost of the fuel. Both costs and demand for these 
fuels in the mining industry have been related primarily to tax credits 
available for using the fuel. With current tax credits, bio-diesel can 
be an attractive fuel alternative for the mining industry. However, we 
have observed maintenance issues with application of bio-diesel fuels 
similar to those associated with water emulsion fuels. Particularly, 
bio-diesel functions as a solvent and cleans the fuel system. This 
results in increased clogging and replacement of fuel filters. It may 
take the mining industry some additional time to assess the impact of 
the increased maintenance on a mining operation.
    The other issue related to the use of bio-diesel fuel is the 
percent of soy oil in the mixture. While any blend is available, B20 is 
a 20 percent blend, and B50 is a 50 percent blend, etc., we note that 
significant DPM reductions are not realized unless the bio-diesel blend 
exceeds 20 percent. We request comments on the mining industry's 
experience with using bio-diesel fuels to reduce DPM exposures.
4. Installation of Environmental Cabs
    Environmental cabs are a proven means to reduce worker exposure to 
DPM. While much of the construction-type equipment used in underground 
stone mines comes equipped with environmental cabs, the cabs on 
specialty mining equipment used in underground hard rock mining are 
less common, particularly in mines with narrow drifts or low seam 
heights. As mine operators realize the benefits of cabs, more and more 
pieces of equipment are being purchased or retrofitted with 
environmental cabs. These cabs provide protection for workers not only 
from diesel particulate but also from noise and dust.
    Many mines have begun a retrofit program, but may require 
additional time to design and retrofit specialty mining equipment with 
environmental cabs. We request comments on the mining industry's 
experience with using environmental cabs to reduce DPM exposures.

V. Complexity of Developing an Appropriate Conversion Factor for the 
Final Concentration Limit

    The June 6, 2005 rule uses a 1.3 conversion factor to convert the 
interim PEL of 400TC [mu]g/m3 to 308EC 
[mu]g/m3, because EC comprises only a fraction of TC. We 
used a factor of 1.3, to be divided into 400TC [mu]g/
m3, to produce a reasonable estimate of TC without 
interferences. The EC interim limit is based on the median TC to EC 
(TC/EC) ratio of 1.3 that was observed for valid samples in the 31-Mine 
Study and agreed to in the second partial DPM settlement agreement (70 
FR 32944). Enforcement sample results to date have also shown that for 
the 400TC [mu]g/m3 interim limit, 1.3 is the most 
appropriate conversion factor.
    However, we believe at this time that the 1.3 conversion factor may 
not be appropriate to convert the final phased-in TC limits to EC 
because of the variety of DPM controls being adopted by mine operators 
since the 31-Mine Study. Depending on the types of DPM controls being 
installed at the mines, a new conversion factor for EC may be needed. 
Clean engines have more of an impact on reducing OC levels. Alternative 
fuels, ventilation, and work practices seem to lower EC and TC at 
similar rates, while DPF and environmental cabs appear to be more 
effective in reducing EC levels. The actual TC to EC ratio could vary 
from mine to mine, and even from one section in a mine to another, 
based on the mix of controls at a mine. We are seeking to maintain the 
level of protection for miners provided by the final limit promulgated 
by the 2001 final rule, pursuant to Section 101(a)(9) of the Mine Act. 
When considering the feasibility of compliance and sampling 
constraints, we believe that the conversion factor from TC to EC for 
the phased-in final limits should take into account the OC and EC 
ratios so that the OC and EC components together would be equivalent to 
a TC concentration. We are working with NIOSH to develop an appropriate 
conversion factor for converting the TC limits of this rulemaking to EC 
limits. Information provided by NIOSH indicated that the ratio of TC to 
EC in the 31-Mine Study is 1.25 to 1.67 (70 FR 32944). NIOSH's report 
on the Phase I study conducted in May, 2003, shows that the EC 
reduction in the isolated zone with one DPF system was 88% and that two 
other systems gave greater than 96% EC reductions when the measured 
concentrations were normalized by ventilation rate. In the final report 
of the Phase II study, NIOSH indicated that higher EC reductions were 
observed in the field than were obtained in the laboratory for whole 
diesel particulate. The results of these studies, as well as other mine 
studies NIOSH has conducted, help inform us of the EC to TC ratio at 
different DPM concentrations. Measuring only the EC component ensures 
that only diesel particulate material is being measured. However, there 
are no established relationships between the concentration of EC and 
total DPM under various operating conditions. We welcome comments 
regarding the types of data we should request from NIOSH to assist us 
in developing an appropriate conversion factor for converting the TC 
limits of this proposed rule to EC limits.
    We will initiate a separate rulemaking to determine what the 
correct TC to EC conversion factor will be for the phased-in final 
limits. In the meantime, we are interested in receiving comments on 
whether the record supports an EC PEL without regard to any conversion 
factor, the appropriate conversion factor if one is used, and any other 
scientific approaches for converting the existing TC limit to an 
appropriate EC limit. However, if a rulemaking to establish a 
conversion factor is not complete before January 20, 2007, we are 
considering

[[Page 53288]]

using the current 1.3 conversion factor that we used to establish the 
interim DPM PEL of 308 EC micrograms to convert the phased-in final DPM 
TC limits to EC equivalents. As we did with the interim TC limit 
pursuant to the July 2002 settlement, we would use the EC equivalents 
as a check to validate that an overexposure is not the result of 
interferences. We are interested in receiving comments on this approach 
to enforcement of the 2007 PEL, assuming the conversion factor 
rulemaking is not completed before January 20, 2007.

VI. Economic Feasibility

    In January 2001, we estimated that yearly cost of the final rule 
would be about 0.67% of yearly industry revenue, which was less than 
the 1% ``screen'' of costs relative to revenues that we use as a 
presumptive benchmark of economic feasibility (66 FR 5889). In this 
rulemaking to consider a phased-in approach to the final concentration 
limit of 160 TC micrograms, we intend to use the entire rulemaking 
record supporting the 2001 final rule and the new information gathered 
during the recent rulemaking to promulgate the new interim PEL. Our 
data in the rulemaking record established that few underground mines 
would experience severe economic hardship from enforcement of the 
interim PEL. Our subsequent enforcement data have confirmed that the 
interim PEL is economically feasible. In order to gain a more thorough 
rulemaking record, particularly in light of recent technological 
developments, we request comments on the economic feasibility of the 
final concentration limit of 160 TC micrograms and implications of the 
proposed phase-in approach on the economic feasibility.

VII. Section 101(a)(9) of the Mine Act

    Section 101(a)(9) of the Mine Act provides that: ``No mandatory 
health or safety standard promulgated under this title shall reduce the 
protection afforded miners by an existing mandatory health or safety 
standard.'' We interpret this provision of the Mine Act to require that 
all of the health or safety benefits resulting from a new standard be 
at least equivalent to all of the health or safety benefits resulting 
from the existing standard when the two sets of benefits are evaluated 
as a whole. The U.S. Court of Appeals for the D.C. Circuit approved 
such a ``net effects'' application of Section 101(a)(9). Int'l Union, 
UMWA v. Federal Mine Safety and Health Admin., 407 F. 3d 1250, 1256-57 
(DC Cir. 2005).
    We have tentatively concluded at this point that this proposed 
phase-in period of the effective date of existing Sec.  57.5060(b) of 
the 2001 final rule establishing a final DPM concentration limit of 
160TC [mu]g/m3 will not reduce miner protection. 
We are concerned that the final concentration limit may be infeasible 
for the mining industry in January 2006. Feasibility issues with 
respect to operator compliance are discussed above. Also, an additional 
concern is whether an effective sampling strategy exists to enforce the 
final TC concentration limits with TC as the surrogate. Evidence in the 
rulemaking record after January 2001 suggests that, in many cases, 
there is no practical sampling strategy that would adequately remove 
organic carbon interferences that occur when TC is used as the 
surrogate. Furthermore, the DPM settlement agreement does not address 
appropriate enforcement procedures for the final concentration limit. 
We also believe at this time that the 1.3 conversion factor used for 
the final interim limit may not be appropriate for substantially lower 
limits, such as the final TC concentration limit of 160TC 
[mu]g/m3. Thus, we have concluded at this time that it is 
questionable whether the final concentration limit of 160TC 
[mu]g/m3 would provide any more protection for miners than 
the 308EC [mu]g/m3 interim limit. We have the 
burden of proof to confirm that an overexposure to DPM actually 
occurred and the sample result is not due to interferences. If we were 
to enforce the final DPM concentration limit of 160TC [mu]g/
m3, we would need to validate a TC sample result,