MSHA Final Rule

Sealing of Abandoned Areas [05/22/2007]

Volume 72, Number 98, Page 28795-28817

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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 75



Sealing of Abandoned Areas; Final Rule


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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 75

RIN 1219-AB52

 
Sealing of Abandoned Areas

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

ACTION: Emergency temporary standard; Notice of public hearings; Notice 
of close of comment period.

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SUMMARY: The Mine Safety and Health Administration (MSHA) is issuing an 
emergency temporary standard (ETS) under section 101(b) of the Federal 
Mine Safety and Health Act of 1977 in response to the grave danger that 
miners face when underground seals separating abandoned areas from 
active workings fail. MSHA has concluded from its investigations of 
mine explosions that occurred and other recent reports, that additional 
immediate action is necessary to protect miners. This ETS includes 
requirements to strengthen the design, the construction, the 
maintenance, and the repair of seals, as well as requirements for 
sampling and controlling atmospheres behind seals. It also increases 
the level of overpressure for new seals, thus implementing the 
requirements of the Mine Improvement and New Emergency Response (MINER) 
Act of 2006.

DATES: This emergency temporary standard is effective May 22, 2007. 
This standard must be replaced with a final rule within 9 months. MSHA 
will hold public hearings on July 10, 2007, July 12, 2007, July 17, 
2007 and July 19, 2007 at the locations listed in the Public Hearings 
section below under the SUPPLEMENTARY INFORMATION section of this 
document. If individuals or organizations wish to make an oral 
presentation for the record, the Mine Safety and Health Administration 
(MSHA) is asking that you submit your request at least 5 days prior to 
the hearing dates. The comment period will close on July 6, 2007.

ADDRESSES: Comments must be clearly identified and may be submitted by 
any of the following methods:
    (1) Federal Rulemaking Portal: http://www.regulations.gov. Follow 

the instructions for submitting comments.
    (2) Electronic mail: zzMSHA-Comments@dol.gov. Include ``RIN 1219-
AB52'' in the subject line of the message.
    (3) Telefax: (202) 693-9441. Include ``RIN 1219-AB52'' in the 
subject.
    (4) Regular Mail: MSHA, Office of Standards, Regulations, and 
Variances, 1100 Wilson Blvd., Room 2350, Arlington, Virginia 22209-
3939.
    (5) Hand Delivery or Courier: MSHA, Office of Standards, 
Regulations, and Variances, 1100 Wilson Blvd., Room 2350, Arlington, 
Virginia 22209-3939. Sign in at the receptionist's desk on the 21st 
floor.
    Docket: Comments can be accessed electronically at http://www.msha.gov 

under the ``Rules and Regs'' link. MSHA will post all comments on the 
Internet without change, including any personal information provided. 
Comments may also be reviewed at the Office of Standards, Regulations, 
and Variances, 1100 Wilson Blvd., Room 2350, Arlington, Virginia.
    MSHA maintains a listserve that enables subscribers to receive e-
mail notification when rulemaking documents are published in the 
Federal Register. To subscribe to the listserve, go to http://www.msha.gov/subscriptions/subscribe.aspx
.

    Information Collection Requirements: Comments concerning the 
information collection requirements must be clearly identified as such 
and sent to both the Office of Management and Budget (OMB) and MSHA as 
follows:
    (1) OMB: All comments must be sent by mail addressed to the Office 
of Information and Regulatory Affairs, Office of Management and Budget, 
New Executive Office Building, 725 17th Street, NW., Washington, DC 
20503, Attn: Desk Officer for MSHA; and
    (2) MSHA: Comments must be clearly identified by RIN 1219-AB46 as 
comments on the information collection requirements and transmitted 
either electronically to zzMSHA-Comments@dol.gov, by facsimile to (202) 
693-9441, or by regular mail, hand delivery, or courier to MSHA, Office 
of Standards, Regulations, and Variances, 1100 Wilson Blvd., Room 2350, 
Arlington, Virginia 22209-3939.
    Hearings: Locations of the public hearings are in the SUPPLEMENTARY 
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office 
of Standards, Regulations, and Variances, MSHA, 1100 Wilson Blvd, Room 
2350, Arlington, Virginia 22209-3939, silvey.patricia@dol.gov (e-mail), 
(202) 693-9440 (voice), or (202) 693-9441. (telefax).

SUPPLEMENTARY INFORMATION: The outline of this ETS is as follows:

I. Public Hearings
II. Introduction
III. Basis for the Emergency Temporary Standard
    A. Regulatory Authority
    B. Grave Danger
IV. Discussion of the Emergency Temporary Standard
    A. Background
    B. General Discussion
    C. Section-by-Section Analysis
V. Executive Order 12866
    A. Population-at-Risk
    B. Benefits
    C. Compliance Costs
VI. Feasibility
    A. Technological Feasibility
    B. Economic Feasibility
VII. Regulatory Flexibility Act and Small Business Regulatory 
Enforcement Fairness Act (SBREFA)
    A. Definition of a Small Mine
    B. Factual Basis for Certification
VIII. Paperwork Reduction Act of 1995
    A. Summary
    B. Details
IX. Other Regulatory Considerations
X. References
XI. Emergency Temporary Standard--Regulatory text

I. Public Hearings

    MSHA will hold four public hearings on the ETS. The public hearings 
will begin at 9 a.m. and end after the last speaker speaks, and in any 
event not later than 5 p.m., on the following dates at the locations 
indicated:

------------------------------------------------------------------------
             Date                       Location              Phone
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July 10, 2007.................  Lakeview Golf Resort        800-624-8300
                                 and Spa, One Lakeview
                                 Drive, Morgantown, WV
                                 26508.
July 12, 2007.................  Crowne Plaza Hotel,         859-255-4281
                                 1375 South Broadway,
                                 Lexington, KY 40504.
July 17, 2007.................  Embassy Suites Denver,      303-696-6644
                                 7525 East Hampden
                                 Avenue, Denver, CO
                                 80231.
July 19, 2007.................  Sheraton Birmingham         205-324-5000
                                 Hotel, 2101 Richard
                                 Arrington Jr.
                                 Boulevard North,
                                 Birmingham, AL 35203.
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    The hearings will begin with an opening statement from MSHA, 
followed by an opportunity for members of the public to make oral 
presentations. You do not have to make a written request to speak. 
Speakers will speak in the order that they sign in. Any unallotted time 
will be made available for persons making same-day requests.

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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 or 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. A verbatim transcript of the 
proceedings will be prepared and made a part of the rulemaking record. 
Copies of the transcript will be available to the public. The 
transcript will also be available on MSHA's Home Page at http://www.msha.gov
, under Statutory and Regulatory Information.

    MSHA will accept post-hearing written comments and other 
appropriate data for the record from any interested party, including 
those not presenting oral statements. Written comments will be included 
in the rulemaking record.

II. Introduction

    This ETS is issued under section 101(b) of the Federal Mine Safety 
and Health Act of 1977 (Mine Act) as amended by the Mine Improvement 
and New Emergency Response Act of 2006 (MINER Act), 30 U.S.C. 811(b). 
The ETS establishes or revises standards in part 75--subpart D--
Ventilation. These new standards strengthen the design, construction, 
maintenance, and repair of seals and monitoring and control of 
atmospheres behind seals in order to reduce the risk of seal failure 
and the risk of explosions in abandoned areas of underground coal 
mines.
    In accordance with section 101(b)(3) of the Mine Act, an Emergency 
Temporary Standard (ETS) serves as both a final rule with immediate 
effect and a proposed rule to establish a final rule through the notice 
and comment process. Therefore, the final rule may differ from an ETS 
just as any final rule may differ from a proposed rule. The Mine Act 
states that the ETS is a temporary standard and must be superseded by a 
final rule within nine months. The Legislative History of the Mine Act 
reinforces the statutory language regarding the ETS serving as a 
proposed rule ``so that all views can be carefully considered in 
connection with the issuance of a permanent standard.'' S. Rept. 181, 
95th Cong., 1st Sess. 24 (1977).
    The preamble discusses specific provisions that may be included in 
the final rule and MSHA solicits comments on these provisions.

III. Basis for the Emergency Temporary Standard

A. Regulatory Authority

    Section 101(b) of the Mine Act provides that:
    1. The Secretary shall provide, without regard to the requirements 
of chapter 5, title 5, United States Code, for an emergency temporary 
mandatory health or safety standard to take immediate effect upon 
publication in the Federal Register if [s]he determines (A) that miners 
are exposed to grave danger from exposure to substances or agents 
determined to be toxic or physically harmful, or to other hazards, and 
(B) that such emergency standard is necessary to protect miners from 
such danger.
    2. A temporary mandatory health or safety standard shall be 
effective until superseded by a mandatory standard promulgated in 
accordance with the procedures prescribed in paragraph (3) of this 
subsection.
    3. Upon publication of such standard in the Federal Register, the 
Secretary shall commence a proceeding in accord with section 101(a) 
[involving notice and comment], and the standards as published shall 
also serve as a proposed rule for the proceeding. The Secretary shall 
promulgate a mandatory health or safety standard under this paragraph 
no later than nine months after publication of the emergency temporary 
standard as provided in paragraph (2).
    An ETS is an extraordinary measure provided by the Mine Act to 
enable MSHA ``to react quickly to grave dangers that threaten miners 
before those dangers manifest themselves in serious or fatal injuries 
or illnesses.'' S. Rept. 181, 95th Cong., 1st Sess. 23 (1977). 
Additionally, ``* * * once the Secretary has identified a grave danger 
that threatens miners the Committee expects the Secretary to issue an 
emergency temporary standard as quickly as possible, not necessarily 
waiting until [she] can investigate how well that grave danger is being 
managed or controlled in particular mines.'' Senate Report at 24. An 
ETS takes effect upon publication in the Federal Register, and is a 
fully enforceable standard.
    To assure the comprehensive protection of miners, the ETS authority 
applies to all types of grave dangers without qualification. The 
legislative history of the Mine Act emphasizes that ``to exclude any 
kind of grave danger would contradict the basic purpose of emergency 
temporary standards protecting miners from grave dangers.'' S. Rept. 
181, 95th Cong., 1st Sess., 24 (1977). The ETS authority thus covers 
dangers arising from exposure to toxic or physically harmful substances 
or agents and to ``other hazards.'' It applies to dangers longstanding 
or novel, to dangers that ``result from conditions whose harmful 
potential has just been discovered'' or to which large numbers of 
miners are ``newly exposed.'' Id.
    A record of fatalities or serious injuries is not necessary before 
an ETS can be issued because ``[d]isasters, fatalities, and 
disabilities are the very thing this provision is designed to 
prevent.'' Id. at 23. At the same time, the legislative history of the 
Mine Act is clear that an ETS is not limited to new dangers in the 
mining industry: ``That a danger has gone unremedied should not be a 
bar to issuing an emergency standard. Indeed, if such is the case the 
need for prompt action is that much more pressing.'' Id. at 24.
    When issuing an ETS, MSHA is ``not required to prove the existence 
of grave danger as a matter of record evidence prior to taking 
action.'' Id. The legislative history expressly recognizes ``the need 
to act quickly where, in the judgment of the Secretary, a grave danger 
to miners exists.'' Id. The ETS is a critical statutory tool that MSHA 
can use to take immediate action to prevent the loss of life in the 
mines. MSHA accordingly has employed an ETS previously to order 
``hands-on'' training for miners in the use of self-contained self-
rescue (SCSR) devices 52 FR 24373 (June 30, 1987), to order certain 
training and mine evacuation procedures for underground coal mines 67 
FR 76658 (December 12, 2002) and to order new accident notification 
timeframes, provide new safety equipment, training and drills in mine 
emergency evacuations 71 FR 12252, (March 9, 2006).

B. Grave Danger

    Based on MSHA's accident investigation reports of the Sago and 
Darby mine explosions,\1\ the National Institute for Occupational 
Safety and Health's (NIOSH) reports on explosion testing and modeling, 
MSHA's in-mine seal evaluations, and review of technical literature, 
MSHA has determined that new comprehensive standards for seal design 
approval, strength and installation approval, construction, maintenance 
and repair, sampling and monitoring, training and recordkeeping

[[Page 28798]]

are necessary to immediately protect miners from hazards of sealed 
areas.
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    \1\ MSHA Report of Investigation/Mine Explosion, Sago Mine, 
January 2, 2006 and MSHA Report of Investigation/Mine Explosion, 
Darby Mine Number 1, May 20, 2006. These reports can be found on 
MSHA's Web site at: http://www.msha.gov.

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    Underground coal mines are dynamic work environments in which the 
working conditions can change rapidly. Caved, mined-out areas may 
contain coal dust and accumulated gas which can be ignited by rock 
falls, lightning, and in some instances, fires started by spontaneous 
combustion. Seals are used to isolate and contain this environment of 
the active workings of the mine. Adequate seals are crucial to prevent 
an explosion from propagating to the outby side of the seal where 
miners work or travel. Seals must therefore be designed to withstand 
elevated pressures and contain explosions by preventing potentially 
explosive or toxic gasses from migrating into the active working areas 
of underground coal mines. Miners rely on seals to protect them from 
the hazardous and sometimes explosive environments within the sealed 
area.
    The existing safety standards for construction of solid-concrete 
block seals adopt specific construction criteria. Existing requirements 
addressing construction of seals using equivalent alternative materials 
and methods were established, as an interim measure, in MSHA's Program 
Information Bulletin No. P06-16, ``Use of Alternative Seal Methods and 
Materials Pursuant to 30 CFR 75.335(a)(2)),'' issued on July 19, 2006 
(July 2006 PIB). Under the July 2006 PIB, MSHA increased the strength 
requirements for new alternative seals to reliably withstand an 
overpressure of at least 50 pounds per square inch gauge (psig) in the 
conditions in which they will be installed as demonstrated by well-
defined and certified engineering designs. An alternative seal design 
could also be approved based on actual test results validating the 
psig. All seal construction must be approved by the District Manager in 
the mine's ventilation plan. To be considered for approval, mine 
operators must have a professional engineer (PE) who is knowledgeable 
in structural engineering to certify seal designs and supporting data. 
In addition, the proposed ventilation plan must provide that a senior 
mine management official (such as mine manager, superintendent, etc.) 
certify that the construction, installation, and materials used were in 
accordance with the mine's approved ventilation plan. Furthermore, the 
July 2006 PIB requires an assessment of the atmosphere behind existing 
alternative seals to determine the potential for an explosion and to 
assess seal integrity. The July 2006 PIB requires the operator to take 
remedial actions which may include inerting the sealed atmosphere, 
increasing the capacity of the existing seal to withstand at least 50 
psig overpressure, constructing an additional alternative seal having 
this capacity, or constructing a solid-concrete seal. Finally, the July 
2006 PIB requires that high risk seals, (such as if failure could 
adversely affect miners' safety) and seals with a poor performance 
history will require additional actions to better protect miners, 
including periodic monitoring of the atmosphere behind the seals.
    MSHA determined in the Sago accident that even though the seals 
were not constructed as approved in the ventilation plan, they still 
could withstand an explosion overpressure of 21 psi. In the Agency's 
root cause analysis of the Sago accident, MSHA found that: (1) The 
seals were not capable of withstanding the forces generated by the 
explosion; (2) The atmosphere in the sealed area was not monitored and 
it contained explosive methane/air mixtures; (3) Lightning was the most 
likely ignition source for the explosion with the energy transferring 
onto an abandoned pump cable in the sealed area and providing an 
ignition source for the explosion. MSHA found that the explosive forces 
generated behind the sealed area in the Sago accident were at least 93 
psi.
    In the Darby accident, MSHA found that the seals were improperly 
constructed and had an inadequate pressure rating. MSHA also concluded 
that the use of an oxygen acetylene cutting torch to cut a metal strap 
outby a seal was the most likely ignition source. MSHA further 
concluded that when seals are improperly constructed, they present a 
hazard to miners, even when ignition sources are located outby the 
seal.
    When seals are improperly constructed and maintained, air may leak 
excessively through the seals, which may result in explosive conditions 
inby the seals. The air leakage causes increased levels of hazardous 
conditions whereby introduction of ignition sources could cause an 
explosion. Air leakage from the sealed area to active working areas 
could also contaminate the atmospheres, resulting in miners being 
exposed to potential explosions or toxic gasses.
    In addition, the ETS requires that insulated cables and metallic 
objects through or across seals be removed from the area to be sealed, 
and prohibits welding, cutting or soldering with an arc or flame within 
150 feet of a seal. The July 2006 PIB's interim action has serious 
limitations in that it fails to provide comprehensive protection for 
miners from the dangers of explosions in sealed areas: it only permits 
testing as one method of demonstrating seal strength; it does not 
address explosion forces generated behind a sealed area that are 
greater than 50 psi; it requires only a one-time assessment of the 
atmosphere behind the seal rather than a sampling plan approved by MSHA 
as required under the ETS; although the July 2006 PIB states that 
periodic monitoring of sealed areas may be required for high risk seals 
(such as if failure could adversely affect miners' safety), a periodic 
monitoring frequency was not specified in the July 2006 PIB; the July 
2006 PIB does not address the hazard of welding, cutting, and soldering 
with an arc or flame in close proximity to a seal. Therefore, hazards 
in existing sealed areas present a grave danger to miners.
    The Secretary has therefore determined that miners are exposed to 
grave danger if existing and new seals are not properly constructed, 
maintained, monitored, and repaired in accordance with this ETS.
    In addition, for the above-stated reasons under the Administrative 
Procedure Act (APA), 5 U.S.C. 553(b)(B) and (d)(3), MSHA finds good 
cause exists to dispense with notice and comment and make the ETS 
effective immediately. To delay the effective date of the ETS is 
contrary to the public interest because any delay in the ETS effective 
date further exposes miners to grave danger from inadequately designed, 
constructed, maintained, and repaired seals.

IV. Discussion of the Emergency Temporary Standard

A. Background

    In the Federal Coal Mine Health and Safety Act of 1969 (Coal Act), 
the predecessor to the existing Mine Act, Congress first recognized 
that mine operators must seal abandoned and isolated areas of 
underground coal mines for the protection of miners' safety:

    In the case of mines opened on or after the operative date of 
this title, or in the case of areas developed on or after such date 
in mines opened prior to such date, the mining system shall be 
designed, in accordance with a plan and revisions thereof approved 
by the Secretary and adopted by the operator, so that, as each set 
of cross entries, room entries, or panel entries of the mine are 
abandoned, they can be isolated from active workings of the mine 
with explosion-proof bulkheads.

Pub. L. 91-173 (Dec. 1969) Section 303(2)(3)).
    In the conference report filed in the House, the statement of the 
managers on

[[Page 28799]]

the part of the House stated, regarding the requirement that an 
abandoned area of a mine either be ventilated or sealed that:

    [t]he determination of which method [(ventilated or sealed)] is 
appropriate and the safest at any mine is up to the Secretary or 
[her] inspector to make, after taking into consideration the 
conditions of the mine, particularly its history of methane and 
other explosive gases. The objective is that [s]he require the means 
that will provide the greatest degree of safety in each case. * * * 
When sealing is required, such sealing shall be made in an approved 
manner so as to isolate with explosion-proof bulkheads such areas 
from the active working of the mine.
    Under the conference substitute, paragraph (3) of section 303(z) 
provides that, in the case of mines opened on or after the operative 
date of this title, or in the case of areas developed on or after 
such date in mines opened prior to such date, the mining system 
shall be designed, in accordance with a plan and revisions thereof 
approved by the Secretary and adopted by the operator, so that, as 
each set of cross entries, room entries, or panel entries of the 
mine are abandoned, they can be isolated from active workings of the 
mine with explosion-proof bulkheads approved by the Secretary or his 
inspector.
    The managers expect the Secretary to take the lead in improving 
technology in this area of controlling methane accumulations in gob 
areas and to improve upon this important section 303(z).

Conf. Rep. No. 91-761, 91Fst Cong. 1st Sess., 82 (Dec. 16, 1969) 
(statement of the managers on part of the House) (emphasis added).
    The Mine Act interim mandatory standards required seals to be 
``made in an approved manner so as to isolate with explosion-proof 
bulkheads such areas from the active workings of the mine.'' 30 U.S.C. 
863(z)(2).
    On May 15, 1992, as part of a comprehensive revision of its 
regulations for ventilation of underground coal mines, MSHA published 
standards for construction of seals in Sec.  75.335 of the ventilation 
standards. The standard requires seals to be constructed of solid 
concrete blocks at least six inches by eight inches by sixteen inches, 
but allows seals to be constructed using alternative methods and 
materials, provided, among other things, that the seal is capable of 
withstanding a horizontal static pressure of 20 psi. MSHA based this 
threshold on a U.S. Bureau of Mines 1971 report entitled ``Explosion-
Proof Bulkheads--Present Practices.''
    A number of manufacturers developed materials, such as cementitious 
foams and glass-fiber material, which were tested and subsequently 
deemed suitable for use in alternative seals and marketed under various 
trade names. MSHA required the manufacturers to have full-scale seals 
be subjected to explosion testing at NIOSH's Lake Lynn Experimental 
Mine (Lake Lynn). MSHA then intended for mine operators to construct 
seals as constructed and tested at Lake Lynn.
    On January 2, 2006, an explosion at the Sago Mine in Upshur County, 
West Virginia caused the death of twelve miners. Later that year, on 
May 20, 2006, an explosion at the Darby Mine No. 1 in Harlan County, 
Kentucky, caused the death of five miners. Common to both of these 
accidents was the failure of the seals in the mine. The failed seals in 
both mines were constructed with the same approved alternative material 
for a 20 psi seal. None of the failed seals were constructed in the 
same manner as they were constructed at Lake Lynn. Therefore, MSHA 
issued a moratorium on alternative methods and materials for 
construction of new seals (Program Information Bulletin (PIB) No. P06-
11, June 1, 2006, reissued on June 12, 2006 as PIB No. P06-12.).
    Following these underground coal mine disasters in 2006, Congress 
passed and the President signed the MINER Act. Section 10 of the MINER 
Act requires that the Secretary issue mandatory health and safety 
standards for seals of abandoned areas no later than December 15, 2007. 
It also requires the Secretary to revise the current standard to 
increase the 20 psi standard for alternative seals.
    Seal failures at the Sago Mine and Darby No. 1 Mine in 2006 raised 
awareness of the problems with seal construction and the design 
criterion of a 20-psi static horizontal pressure. MSHA continued its 
investigation of these and other failures of alternative seals, and 
conducted in-mine evaluations of existing alternative seals. It also 
reviewed the history of seals in the United States and other countries. 
Presently, most coal producing countries have coal mine seal 
requirements that are in excess of a 20-psi overpressure. As a result 
of MSHA's continued investigations and in-mine evaluations, MSHA 
increased the strength of alternative seals to 50 psi and addressed a 
number of other issues related to the construction and the 
effectiveness of current alternative and solid concrete block seals in 
Program Information Bulletin No. P06-16, ``Use of Alternative Seal 
Methods and Materials Pursuant to 30 CFR 75.335(a)(2)),'' issued on 
July 19, 2006 (July 2006 PIB).
    On February 8, 2007, NIOSH issued a draft report, ``Explosion 
Pressure Design Criteria for New Seals in U.S. Coal Mines'' (2007 NIOSH 
Draft Report). The draft report states that ``mine seals and their 
related systems such as the monitoring, inertization and ventilation 
systems require the highest level of engineering and quality assurance. 
Successful implementation of the seal design criteria and 
recommendations in this report should reduce the risk of seal failure 
due to explosions in abandoned areas of underground coal mines.'' (2007 
NIOSH Draft Report at 40). In the executive summary of the draft 
report, NIOSH makes recommendations for formulating seal design 
criteria.

B. General Discussion

    Existing Sec.  75.334(a) requires that inactive areas of 
underground coal mines be ventilated or sealed. Most inactive areas are 
sealed because of ground control, ventilation issues, and the long-term 
costs of maintaining ventilation and roof support in inactive areas. 
Seals are also installed to withstand overpressures resulting from 
explosions in inactive areas and to prevent the potentially explosive 
methane/air mixtures from migrating to the working areas.
    A methane/air mixture becomes explosive when 5 percent to 15 
percent methane is present with at least a 12 percent oxygen 
concentration. If an ignition source is available, then an explosion 
can occur and create high overpressures. The homogeneity of the 
methane/air mixture contributes to its explosiveness. The homogeneity 
of the methane/air mixture can vary depending on the elevation and the 
methane liberation of the sealed area and outside factors such as the 
current temperature and barometric pressure. The speed of an explosion 
and the physical characteristics of a sealed area can increase the 
force of the explosion such that detonations and significant pressure 
piling are possible.
    In order to address mine conditions that influence the magnitude of 
overpressures in explosions, seals need to be designed and constructed 
properly and then inspected on a periodic basis and properly maintained 
to ensure their reliability. The 2007 NIOSH Draft Report states as 
follows:

    NIOSH engineers examined seal design criteria and practices used 
in the U.S., Europe and Australia and then classified seals into 
their various applications. Next, NIOSH engineers considered various 
kinds of explosive atmospheres that can accumulate within sealed 
areas and used simple gas explosion models to estimate worst case 
explosion pressures that could impact seals. Three design pressure 
pulses (pressure-time curves) were developed for the dynamic 
structural analysis of new seals under the conditions in which those 
seals may be used: unmonitored seals where there is a

[[Page 28800]]

possibility of methane-air detonation behind the seal; Unmonitored 
seals with little likelihood of detonation; and monitored seals 
where the amount of potentially explosive methane-air is strictly 
limited and controlled. These design pressure pulses apply to new 
seal design and construction.
    For the first condition, an unmonitored seal with the 
possibility of detonation, the recommended design pulse rises to 4.4 
MPa (640 psi) and then falls to the 800 kPa (120 psi) constant 
volume explosion overpressure. For unmonitored seals without the 
possibility of detonation, a less severe design pulse that simply 
rises to the 800 kPa (120 psi) constant volume explosion 
overpressure, but without the initial spike, may be employed. For 
monitored seals, engineers can use a 345 kPa (50 psi) design pulse 
if monitoring can assure (1) that the maximum length of explosive 
mix behind a seal does not exceed 5 m (15 ft) and (2) that the 
volume of explosive mix does not exceed 40% of the total sealed 
volume. Use of this 345 kPa (50 psi) design pulse requires 
monitoring and active management of the sealed area atmosphere.

    Based on MSHA's accident investigation reports of Sago and Darby 
mine explosions, NIOSH reports on explosion testing and modeling, 
MSHA's in-mine seal evaluations, and review of technical literature, 
MSHA identified a number of issues pertinent to the construction and 
efficacy of current alternative and solid concrete block seals.

C. Section-by-Section Analysis

1. Sec. 75.335 Seals Requirements

    The ETS increases seal strength requirements for construction of 
new seals and, where necessary, establishes new requirements for 
monitoring and inerting atmospheres of sealed areas. New Sec.  
75.335(a) provides that seals constructed in underground coal mines 
after May 22, 2007 must be designed, constructed and maintained in 
accordance with MSHA approval of a mine operator's design application 
and installation procedures incorporated in the ventilation plan.
    The ETS establishes a three-tiered approach for overpressure 
loading criteria applicable to new seals: (1) 50 psi overpressure; (2) 
120 psi overpressure; and (3) an overpressure greater than 120 psi. For 
purposes of this ETS, MSHA intends that overpressure be any pressure 
exerted by the forces of an explosion that is above normal atmospheric 
pressure. In developing these overpressure loading criteria, MSHA 
relied upon the 2007 NIOSH Draft Report, the Agency's safety and health 
experience with respect to seals and underground mining conditions and 
investigations, and accepted scientific and engineering principles.
    Under the ETS, if a mine operator monitors and maintains the 
atmosphere in these areas inert, new Sec.  75.335(a)(1) requires a seal 
design to withstand at least 50 psi overpressure. If a mine operator 
does not monitor and maintain atmospheres in these areas inert, new 
Sec.  75.335(a)(2) requires a seal design to withstand at least 120 psi 
overpressure. A seal design that will withstand an overpressure greater 
than 120 psi is required under new Sec.  75.335(a)(3) when the mine 
operator does not monitor and maintain the atmosphere within sealed 
areas inert and when: (1) The atmosphere in the area is likely to 
contain homogeneous mixtures of methane between 4.5 percent and 17.0 
percent, and oxygen exceeding 17.0 percent throughout the entire sealed 
area; (2) or pressure piling is likely due to opening restrictions near 
the proposed seal area; or (3) other conditions are encountered, such 
as the likelihood of a detonation in the proposed seal area. Where the 
conditions in Sec.  75.335(a)(3) are likely to occur, the mine operator 
must revise the ventilation plan required by existing Sec.  75.370 to 
address the appropriate seal strength.
    The ETS does not require mine operators to upgrade seals 
constructed prior to May 22, 2007. However, new Sec.  75.335(b) 
enhances the protection afforded miners under the previous standard by 
requiring, among other things, that atmospheres in the sealed areas be 
monitored and inerted. If a mine operator does not monitor and inert 
the atmosphere in an existing sealed area, the strength of the seals 
must be increased to 120 psi or greater.
a. Sec. 75.335(a)
    New paragraph (a)(1) requires that seals be constructed to 
withstand 50 psi overpressure. However, mine operators who construct 
these seals must monitor the atmosphere behind the seals and maintain 
them inert. Mine operators are currently required to construct seals 
that will withstand 50 psi overpressure under the July 2006 PIB. In 
addition, the July 2006 PIB required mine operators to assess 
atmospheres behind alternative seals and take remedial action where 
necessary. The 2007 NIOSH Draft Report also recommends a 50 psi 
overpressure for monitored and managed atmospheres behind sealed areas. 
Monitoring sealed areas allows the mine operator to know the 
composition of potentially hazardous gases in sealed areas. Use of a 50 
psi overpressure seal requires the mine operator to maintain an inert 
atmosphere in the sealed area since explosions cannot occur within 
inert atmospheres.
    MSHA believes that in mines that liberate significant volumes of 
methane, the atmosphere in sealed areas will become inert naturally. In 
mines that produce very small volumes of methane, the atmosphere in 
sealed areas may never approach explosive methane/air mixtures of 5 
percent. However, some mines may need to actively inert the atmosphere 
in the sealed area. To inert, an inert gas such as nitrogen or carbon 
dioxide may be injected into the sealed area through boreholes or pipes 
extending through the seals. The gas may be obtained from a bulk plant 
and trucked to the mine site and pumped into the sealed area through a 
borehole or pipe into the seal. It also may be produced at the mine 
using a nitrogen generator, Tomlinson Boiler, or other inertization 
device. This process is commonly used in underground coal mines in the 
United States during firefighting activities and in other countries 
where spontaneous combustion is common. MSHA is interested in receiving 
comments regarding: (1) The economic and technological feasibility of 
monitoring and inerting sealed atmospheres; and (2) methods of inerting 
sealed atmospheres.
    New paragraph (a)(2) requires 120 psi overpressure if the sealed 
atmosphere is not monitored and maintained inert except as provided in 
new paragraph (a)(3). This provision allows mine operators to install 
seals that withstand 120 psi overpressure if they do not choose to 
monitor and inert the sealed atmosphere. In MSHA's experience, the 
overwhelming majority of underground coal mine explosions are typically 
deflagrations. A deflagration occurs when the flame of an explosion 
propagates through unburned fuel at a velocity below the speed of 
sound. The faster the flame travels, the higher the pressures become. 
Maximum pressures in a deflagration involving methane or coal dust are 
limited to approximately 120 psi without the occurrence of detonation 
or significant pressure piling. MSHA accident reports during the past 
30 years do not reference an underground coal mine explosion in the 
United States that generated an overpressure of greater than 120 psi 
except in the rare instance when detonation occurred.
    New paragraph (a)(3) also addresses overpressures resulting from 
pressure piling and detonations. Methane is explosive between 5 percent 
and 15 percent and requires at least 12 percent oxygen to ignite. 
(NIOSH 2006, IC 9486) When ignited, an explosion can occur. To account 
for correction factors of

[[Page 28801]]

methane detection equipment and potential contamination of the samples, 
the ETS requires that methane concentrations between 4.5 percent and 
17.0 percent shall be used to determine an explosive atmosphere. If 
ignited, large volumes of homogeneous explosive methane/air mixtures in 
a sealed area can generate high explosion overpressures. The 
homogeneity of methane/air mixtures in a sealed area is affected by a 
number of factors such as elevation, temperature, methane liberation, 
and barometric pressure. Based on Agency experience, MSHA anticipates 
that there will be few mines that have homogeneous explosive methane/
air mixtures throughout the entire area to be sealed. Commenters are 
encouraged to submit information, with supporting documentation, 
regarding the number of mines that may have homogeneous explosive 
methane/air mixtures throughout the entire area to be sealed.
    MSHA believes that detonations and significant pressure piling may 
occur under certain situations. Detonations in underground coal mines 
are rare. A detonation occurs when the flame of an explosion propagates 
through the unburned fuel at a velocity exceeding the speed of sound 
(1129 feet per second). Pressures resulting from a detonation involving 
methane or coal dust can exceed 250 psi. Pressure piling occurs when 
the atmosphere ahead of the flame front is compressed prior to the 
arrival of the flame. When the flame burns through this compressed 
mixture, an increase in the explosion pressure occurs. Thus, if this 
mixture is compressed to 45 psi prior to the flame arriving, the 
resulting explosion pressure could exceed 300 psi. Pressure piling can 
occur when the physical configuration through which the explosion will 
propagate inhibits the flow of gases for pressure equalization, such as 
decreasing the number of entries, decreasing the size of the entries, 
or obstructing the entry.
    The ETS does not specify a seal strength under paragraph (a)(3). 
Under this provision, the mine operator would submit a strength 
requirement based on mine-specific conditions that are likely to result 
in pressure piling or detonation in the sealed area. The mine operator 
must first recommend the seal strength in the ventilation plan. MSHA 
expects that mine operators will submit a thorough engineering analysis 
conducted by a person knowledgeable in explosions and explosion 
overpressures, based on the conditions in the mine. After the seal 
strength is approved by the District Manager, the process in Sec.  
73.336 will apply. MSHA expects that in these few instances, the 
District Manager and the Office of Technical Support will coordinate 
MSHA activities related to the approval process. MSHA believes that 
most mine operators who encounter homogenous explosive methane/air 
mixtures and pressure piling in the entire sealed area will monitor and 
inert the atmosphere in sealed areas. Although the recommended maximum 
seal strength in the 2007 NIOSH Draft Report is 640 psi, MSHA has no 
empirical or other data, at this time, demonstrating that mine 
conditions exist that will necessitate seals stronger than 120 psi. 
MSHA requests comments from the mining community on the appropriateness 
of the strategy in this ETS for addressing seal strength greater than 
120 psi.
    In the ETS, MSHA considered a performance-based approach to the 
strength requirement for seals. However, MSHA included specific numbers 
for the strength of seals in the ETS as the agency believes this 
represents a more appropriate approach. MSHA specifically solicits 
comments on the Agency's approach to the strength requirement for 
seals.
    MSHA is also interested in receiving comments on the 
appropriateness of the three-tiered approach to seal strength in the 
ETS. If commenters believe a different regulatory approach should be 
developed for the final rule the Agency would like commenters to 
provide: (1) The details for such a strategy, (2) rationale for such a 
strategy; and (3) feasibility of using such strategy. The Agency 
particularly seeks the views of the mining community regarding whether 
there are other effective alternatives to the requirements in the ETS 
with respect to providing the most appropriate and protective action 
for miners exposed to hazards of existing sealed areas. Commenters 
should provide supporting data, and specific alternatives, including 
information on technological and cost implications.
    Most existing seals were constructed to withstand a static 
horizontal pressure of 20 psi. MSHA also considered requiring mine 
operators to remove existing seals and replace them with seals that 
withstand at least 50 psi. Currently, the Agency believes that 
replacing existing seals is impractical, and in some instances, may 
create safety hazards. In addition, these existing seals must be 
monitored and the atmospheres behind them must be maintained inert. The 
atmosphere inby and outby the seals near the roof, ribs, or floor 
adjacent to the seal may contain low oxygen and/or explosive methane/
air mixtures that are highly hazardous to miners' safety. In addition, 
the conditions inby the seals, such as bad roofs, roof falls, and water 
accumulations, may prevent the mine operator from making changes to 
provide adequate ventilation inby the seals. MSHA seeks comments on the 
feasibility of including in the final rule a requirement that existing 
seals be removed and replaced with a higher strength seal.
    Another regulatory option that MSHA considered is whether to 
require mine operators to build new seals outby existing seals. In some 
cases, this may not be feasible because the seals may have been 
constructed too close to the outby corner of the pillar so that there 
is insufficient space to build new seals in the same pillar; and there 
may not be an additional open entry outby the existing seals allowing 
for construction of new seals.
    MSHA also considered whether to require mine operators to reinforce 
existing seals. The Agency is concerned with the feasibility of this 
option and whether such a requirement could expose miners to greater 
hazards as discussed earlier in this preamble. MSHA, however, will 
continue to explore technological advances addressing feasible and safe 
methods to reinforce existing seals in underground coal mines. 
Commenters are encouraged to submit information and supporting data 
regarding new technologies to reinforce seal strength.
    Existing Sec.  75.335(a) included minimum specifications for seals 
constructed of solid concrete blocks after November 15, 1992. Also, 
existing Sec.  75.335 (a)(2) allowed mine operators to use alternative 
construction methods or materials to construct a seal provided the seal 
could withstand a static horizontal pressure of 20 psi (subsequently 
increased to 50 psi in the July 2006 PIB). In addition, the method of 
installation and material used had to be approved by the District 
Manager under MSHA's ventilation plan procedures in Sec.  75.370 based 
on a 1971 report entitled ``Explosion-Proof Bulkheads--Present 
Practices,'' issued by the former U.S. Bureau of Mines. According to 
that report, when a sealed atmosphere has adequate incombustible 
material and minimum coal dust accumulations, it is doubtful that 
pressures exceeding 20 psi could occur very far from the origin of the 
explosion. The primary disadvantage of this level of explosion 
protection is that current evidence establishes that explosions of coal 
dust or methane can generate explosion pressures of 120 psi, without 
detonation or pressure piling.
    Previous Sec.  75.335(a)(2) also included measures to prevent 
exposed timber

[[Page 28802]]

seals from quickly failing in a fire or other mine emergency. New 
construction of timber seals must meet the requirements set forth in 
this ETS.
b. Sec. 75.335(b) Sampling and Monitoring Requirements
    ETS Sec.  75.335(b) establishes new sampling and monitoring 
requirements for sealed areas. This provision requires that on the 
effective date of this ETS, a certified person, as defined under 
existing Sec.  75.100, must immediately monitor atmospheres in all 
existing sealed areas when seals are outgassing, such as when the 
barometric pressure in the sealed area exceeds the pressure on the 
outby side of the sealed area. MSHA intends for mine operators to 
establish a baseline analysis over a 14-day sampling period, as 
specified under Sec.  75.335(b)(5)(iii), followed by weekly sampling 
under paragraph (b)(1) of this section. While sampling is being 
conducted, mine operators must train certified persons in sampling 
procedures and develop a sampling protocol to be included in the 
ventilation plan and submitted to the District Manager for approval.
    This provision also requires that for seals constructed prior to 
May 22, 2007 and seals designed for 50 psi overpressure according to 
ETS Sec.  75.335(a)(1), mine operators shall develop and follow a 
protocol to monitor methane and oxygen concentrations and to maintain 
an inert atmosphere in sealed areas. The protocol shall be approved in 
the ventilation plan. The sampling protocol must ensure that an inert 
atmosphere behind the seal area is maintained. An explosion will not 
occur in an inert atmosphere. The July 2006 PIB and this ETS require 
mine operators to conduct an atmospheric assessment behind existing 
alternative seals to determine the potential for an explosion and 
assess seal integrity. This ETS requirement enhances protection of 
miners working in the active portions of the mine adjacent to sealed 
areas where existing seals were installed prior to this ETS. In 
addition, this provision protects the miner where 50 psi seals will be 
installed under this rule. MSHA recognizes that conditions in mines may 
vary and mine operators can more appropriately address their specific 
conditions in the ventilation plan. During 2006, MSHA inspected 
existing seals. The inspections revealed that some mine operators were 
not adhering to their approved ventilation plan for seal installation 
and construction. The ETS emphasizes the importance of sampling sealed 
atmospheres to ensure that they remain inert.
    ETS Sec.  75.335(b)(1) requires that a trained certified person 
sample atmospheres of sealed areas weekly when the barometric pressure 
is decreasing or the seal is outgassing. Because the information 
obtained during sampling of a sealed area is critical to the safety of 
miners, the ETS requires sampling to be conducted by a certified 
person. At least one sample shall be taken at each set of seals. If a 
seal is ingassing, such as when the barometric pressure outside the 
sealed area exceeds the pressure on the inby side of the sealed area 
during the weekly examinations, the ETS requires that a sample shall be 
collected during the next weekly examination to determine if the seal 
will outgas. If the seal is ingassing during the second consecutive 
weekly examination, the operator shall examine that seal daily until 
the seal is outgassing, unless the seal does not outgas. In this 
circumstance, an alternative protocol must be developed to effectively 
evaluate the atmosphere in the sealed area and submitted to the 
District Manager for approval. Although the ETS does not specify the 
length of time that the seal must be examined to determine if it will 
outgas, MSHA intends to require mine operators to develop the 
alternative protocol within a reasonable timeframe. The District 
Manager may approve different sampling frequencies and locations in the 
ventilation plan or approve the use of atmospheric monitoring systems 
in lieu of weekly sampling. The mine operator shall revise the protocol 
in the ventilation plan if repeated sampling indicates that a seal is 
not likely to outgas.
    MSHA expects that the certified person will conduct sampling 
required under the ETS as part of the examinations of seals required in 
existing Sec.  75.360 and Sec.  75.364 and base the time of these 
examinations on the barometric conditions to the extent possible. All 
seals and the strata around them will leak air, resulting in an air 
exchange near the seal during barometric changes. MSHA does not expect 
the air leakage to significantly impact the atmosphere in a large 
portion of the sealed area, but it may affect the atmosphere at a 
sampling location when the seal is ingassing. Therefore, it is 
important that samples be representative of the atmospheric conditions 
in the larger portion of the sealed area, rather than just the area 
immediately inby the seal.
    The certified person must take at least one sample at each set of 
seals during the weekly examination. Each newly constructed seal must 
be equipped with two sampling pipes. In accordance with the ETS, MSHA 
expects that most mines will need to take only one sample from a seal 
in each set of seals. However, the number of seals that need to be 
sampled will be determined from the results of the 14-day sampling 
period specified in paragraph (b)(5)(iii) of this section.
    If the seal is ingassing during the examination, the certified 
person must attempt to take a sample during the next weekly 
examination. After a second attempt is made and the seal is still 
ingassing, attempts must be made daily until the seal outgasses. If 
repeated sampling indicates that a seal is not likely to outgas, then 
the mine operator must submit an alternative protocol to the District 
Manager. The alternative protocol must address a means to effectively 
evaluate the atmosphere in the sealed area. The alternate protocol may 
address various means such as: (1) The use of a borehole or previously 
installed sampling line to obtain samples, (2) pressure balancing of 
the ventilation system to make the seals outgas, or (3) the use of 
inert gas injection.
    The District Manager may approve different sampling frequencies and 
locations in the ventilation plan. This is intended to address those 
instances when the atmosphere in the sealed area is unstable, close to 
the explosive range, or subject to other hazardous conditions, such as 
a history of spontaneous combustion, which make it necessary to sample 
at a greater frequency. However, a less frequent sampling strategy may 
be approved in the ventilation plan if the atmosphere in the sealed 
area is stable and not at all close to explosive range. For example, 
the oxygen must be significantly below 10 percent, and methane far less 
than 3 percent or far greater than 20 percent.
    Sampling requirements also addresses instances when an adequate 
evaluation of the atmosphere in the sealed area cannot be obtained with 
the sampling pipes located 15 feet inby the seal and into the center of 
the first connecting crosscut inby the seal. In some sealed areas, the 
District Manager may find it necessary to require in the ventilation 
plan that samples be obtained at additional locations to determine that 
the atmosphere is inert. Additional samples may need to be taken at 
mines with sealed areas that are very large, have multiple sets of 
seals, connect with another mine, have flooded areas, have capped 
shafts, or in other circumstances which may cause samples of the 
atmosphere taken near the seals not to be representative of the entire 
sealed area.
    The ETS also allows the use of an Atmospheric Monitoring System 
(AMS)

[[Page 28803]]

in lieu of a person physically taking samples on a weekly basis. The 
use of AMS is discussed more fully under paragraph (b)(5)(vi) of this 
section.
    MSHA believes that the sampling strategy in this ETS will yield 
results that reflect a reasonable representation of the atmosphere in a 
sealed area. MSHA is requesting comments addressing the sampling 
approach in this ETS. The agency is particularly interested in comments 
concerning sampling, and the sampling frequency, including sampling 
only when a seal is outgassing. The Agency requests comments on whether 
another sampling approach is more appropriate for a final rule, such as 
when the seal is ingassing. MSHA also requests comments, information, 
and experiences of the mining community concerning sampling sealed 
areas.
    Paragraph (b)(2) requires that certified persons shall be trained 
in sampling procedures included in the protocol at paragraph (b)(5) of 
this section prior to conducting sampling. This requirement would 
ensure that certified persons conducting the sampling have the training 
necessary to use the sampling devices and knowledge of the sampling 
protocol requirements in the mine's ventilation plan.
    This training shall be conducted by persons with knowledge of the 
requirements in paragraph (b)(5) of this section. Training may be 
conducted by a variety of people, including a manufacturer's 
representative, ventilation engineer or a certified person at the mine. 
MSHA expects the operator to utilize appropriate people to conduct the 
training.
    At a minimum, this training should include:
    1. Relevant information in the mine's ventilation plan;
    2. Sampling procedures including equipment and methods to be used;
    3. Location of sampling points and sampling pipes;
    4. The baseline analysis of oxygen and methane concentrations in a 
sealed area over a 14-sampling day period;
    5. Frequency of sampling for each set of seals;
    6. Recording procedures required in paragraph (b)(6) of this 
section;
    7. Sampling frequency in the mine's ventilation plan, if an AMS is 
used; and
    8. General information concerning mine gases present in sealed 
areas.
    Training should include specific actions to take in implementing 
the operator's ``action plan'' when methane concentrations are at one 
of three different ranges and oxygen concentrations are 10.0 percent or 
greater.
    MSHA recognizes that the amount of time required to train a 
certified person will vary. For this reason, MSHA is not specifying a 
minimum amount of time for training, but instead a requirement that is 
performance-oriented. MSHA anticipates that mine operators will adjust 
the time required for this training based on the complexity of sampling 
procedures, sampling protocol, and existing knowledge and skill level 
of the certified person. MSHA also expects operators will include 
``hands-on'' training during this session to assure that the certified 
person demonstrates the necessary skills and abilities to perform the 
tasks. Hands-on training would mean that a certified person 
demonstrates to the trainer the necessary skills and abilities to 
perform the testing for oxygen and methane. Hands-on training includes 
practical application of the type of sampling equipment and the methods 
to be used at the mine. Examples of this type of training include 
calibration of sampling equipment, setup of equipment, and recognition 
of the proper functioning of equipment.
    All certified persons shall receive refresher training annually to 
ensure that they maintain the competence necessary to effectively 
perform the requirements in paragraph (b)(5) of this section. Annual 
retraining shall be required within 12 months of the person receiving 
initial or annual training. For example, a certified person receiving 
initial training in May 2007 is expected to complete annual retraining 
no later than the end of May 2008. The month that the refresher 
training is completed establishes the anniversary month for the next 
annual retraining. This is consistent with other MSHA training 
requirements.
    This ETS also requires mine operators to certify the date and 
content of the training provided to the certified person. Operators are 
required to retain these certifications for one year from the time 
training was conducted. This provision is similar to other 
certification requirements in part 75 in which the operator certifies 
by signature and date that training was provided.
    ETS Sec.  75.335(b)(3) states that the atmosphere in the sealed 
area is considered inert when any of the following conditions occur:
    (1) The oxygen concentration is less than 10.0 percent;
    (2) The methane concentration is less than 3.0 percent; or
    (3) The methane concentration is greater than 20.0 percent.
    This ETS provision is consistent with MSHA guidance published in 
the July 2006 PIB. The explosive range of methane is 5 to 15 percent 
when the oxygen level is 12 percent or more (IC 9486, 2007 NIOSH Draft 
Report). To allow for the inaccuracy of methane and oxygen detection 
equipment and potential contamination of the samples, oxygen less than 
10.0 percent, methane concentration less than 3.0 percent and methane 
concentration greater than 20.0 percent were used to determine an inert 
atmosphere.
    ETS Sec.  75.335(b)(4) requires that when oxygen concentrations are 
10.0 percent or greater and methane concentrations are from 3.0 percent 
to 20.0 percent in a sealed area, the mine operator shall take two 
additional gas samples at one hour intervals. If the two additional gas 
samples are from 3.0 percent to 20.0 percent methane and oxygen is 10.0 
percent or greater, then the mine operator shall initiate actions 
required in ETS Sec.  75.335(b)(4)(i) or (ii). The ranges for methane 
and oxygen in this paragraph include a margin of safety, account for 
errors in instrumentation or sampling methods (NIOSH IC 9486), and 
allow the mine operator to obtain confirming samples before 
implementing the actions outlined in (b)(4)(i) and (b)(4)(ii). However, 
because the atmosphere in the sealed area is critical to the safety of 
miners, the ETS requires that samples be taken at one-hour intervals 
under Sec.  75.335(b)(4).
    Paragraphs (b)(4)(i) and (b)(4)(ii) of the ETS require the mine 
operator to implement the action plan specified in the protocol or to 
withdraw all persons from the affected area when the specified 
concentrations are encountered. Historically, when methane levels 
reached 4.5 percent in active areas of mines, miners were withdrawn 
from the areas that were dangerous due to high concentrations of 
methane. However, withdrawal of miners is not required if, under 
paragraph (b)(4)(i), the operator chooses to implement the action plan 
to address the actions to be taken by mine operators when the specified 
concentrations in Sec.  75.335(b)(4) are reached; these concentrations 
provide a margin of safety. However, the action plan must be approved 
in the mine's ventilation plan and must provide protection to miners 
equivalent to withdrawal under paragraph (b)(4)(ii). MSHA requests 
comments on this approach and whether it provides adequate protection 
for miners. Commenters are encouraged to submit specific language, with 
supporting data for MSHA to consider for development of a final rule.
    ETS Sec.  75.335(b)(5) establishes the elements that must be 
addressed in a mine operator's sampling protocol and

[[Page 28804]]

actions to be taken when sampling results indicate that the atmosphere 
behind the sealed area is not inert. Paragraph (b)(5)(i) requires that 
the mine operator specify sampling procedures, including the type of 
equipment and methods to be used by the mine operator for the sampling 
program. MSHA believes most mine operators will use hand-held methane 
and oxygen detection equipment that they currently have at the mine 
site. Other operators may need to purchase detectors capable of 
measuring high levels of methane. Although the mine operator may 
collect samples in containers to be analyzed by a gas chromatograph, 
the operator must specify in the protocol when the sample will be 
analyzed and the procedures that will be followed when the sample 
results indicate action levels are reached. The methods to be used 
should include the physical connections to the sample pipes as well as 
the length of time the detector or pump should be operated to collect 
the sample. The length of time will be dependent on the length of the 
sampling pipes.
    ETS Sec.  75.335(b)(5)(ii) requires that the mine operator specify 
in the sampling protocol the location of sampling points used for the 
sealed area in a set of seals. The sampling points should be identified 
on a mine map, or the operator should have a narrative description of 
the location of the sampling points that can be readily identified on a 
mine map.
    ETS Sec.  75.335(b)(5)(iii) requires that the mine operator specify 
procedures in the protocol to establish a baseline analysis of oxygen 
and methane concentrations at each sampling point over a 14-day 
sampling period. For existing seals, the mine operator must begin this 
sampling upon the effective date of this rule. For newly constructed 
seals, the mine operator must begin this sampling upon completion of 
the seal construction.
    The baseline shall be established after the atmosphere in the 
sealed area is inert or the trend reaches equilibrium. These samples 
would be taken by approved hand-held gas detectors or equipment that 
collects samples in containers to be analyzed by gas chromatograph. 
These samples need to be collected over a consecutive 14-day sampling 
cycle to establish a baseline for a future sampling cycle at each 
sampling point. Samples need only be taken when the seals are 
outgassing during the baseline period to ensure samples are 
representative of the larger area inby the seals. If the seals are not 
outgassing during any of the days of sampling, the baseline sampling 
period needs to be extended until 14 samples are taken. Once a baseline 
is established, the seals need to be sampled at least weekly. MSHA is 
requesting comments on this sampling approach. The agency is 
particularly interested in comments concerning the establishment of a 
baseline, including sampling only when a seal is outgassing and whether 
it is appropriate to sample the atmosphere in sealed areas during 
ingassing. MSHA also requests comments, information, and experiences 
with sampling sealed areas, including data, analytical information, 
establishment of equilibrium, and trends.
    ETS Sec.  75.335(b)(5)(iv) establishes the frequency of sampling at 
each seal or set of seals. Once a baseline is established, the seals 
must be sampled at least weekly while the seals are outgassing. Weekly 
examinations under existing Sec.  75.364 cannot exceed a 7-day 
interval. Mine operators may conduct sampling required under this ETS 
in conjunction with weekly examinations under existing Sec.  75.364. 
Depending on the location and the results of sampling, MSHA may require 
that seals or sets of seals be sampled at different sampling intervals. 
Additionally, there may be circumstances where seals or sets of seals 
within a single sealed area, have a different sampling frequency.
    ETS Sec.  75.335(b)(5)(v) requires that the mine operator specify 
size and conditions of the sealed area. Some mine-specific conditions 
inby the sealed area may include the type of mining, the presence of 
pillared areas, the average mining height, the occurrence of bottom 
mining, any entry restrictions near the seals, the size of the sealed 
area and the number of seals in each set of seals. This information is 
important to determine the appropriate seal strength.
    ETS Sec.  75.335(b)(5)(vi) requires that the protocol address an 
atmospheric monitoring system (AMS) to monitor sealed areas, where 
applicable. MSHA may approve use of an AMS to monitor methane and 
oxygen levels and pressure differentials across the seals in lieu of a 
person physically taking or collecting methane samples. The AMS 
consists of sensors to monitor methane and oxygen levels in the sealed 
area and the pressure differential across the seal.
    ETS Sec.  75.335(b)(5)(vii) requires that the protocol include an 
action plan addressing hazards presented and actions taken when gas 
samples indicate oxygen concentrations of 10.0 percent or greater for 
each of the following ranges of methane concentrations: (1) 3.0 percent 
or greater but less than 4.5 percent; (2) 4.5 percent or greater but 
less than 17.0 percent; and (3) 17.0 percent to 20 percent. MSHA 
expects the action plan to address the risk to miners based on the 
location of seals, the locations of escapeways, the size and nature of 
the sealed area, potential impact of seal failure on the mine 
ventilation system, and the exposure to miners to any potential seal 
failures. MSHA may require additional sampling when methane ranges are 
between 3.0 and up to 4.5 percent and from over 17.0 percent to 20 
percent, as well as possible changes to the ventilation system, or the 
addition of inert gas to the sealed area. A methane range between 4.5 
and 17.0 percent and an oxygen level greater than 10 percent requires 
the mine operator to follow the action plan set forth in the protocol 
in the ventilation plan or to evacuate miners from the affected area of 
the mine. If miners must be withdrawn, the only persons who may remain 
in the affected area are those persons referred to in section 104(c) of 
the Mine Act.
    ETS Sec.  75.335(b)(6) requires that the certified person promptly 
record each sample result from sealed areas, including the location of 
sampling points, and oxygen and methane concentrations. The results of 
oxygen and methane samples must be recorded as the percentage of oxygen 
and methane measured by the certified person. Also, the ETS requires, 
where applicable, that the certified person promptly record monitoring 
results from AMS systems.
    If sampling and monitoring results indicate the presence of a 
hazardous condition to miners, the certified person must record the 
hazardous condition found in accordance with existing Sec.  75.363 
(Hazardous conditions; posting, correcting and recording). Also Sec.  
75.335(b)(6) requires that hazardous conditions be corrected 
immediately or the area must be posted. In addition, records of 
hazardous conditions must be reviewed and countersigned by the mine 
foreman, or equivalent mine official, by the end of the mine foreman's 
or equivalent mine officials next regularly scheduled working shift.
    ETS Sec.  75.335(b)(7) requires that the mine operator retain 
sampling records at the mine for at least one year from the date of 
sampling. A one year retention period permits the mine operator to 
track trends or changes. The one year retention period is consistent 
with existing Sec. Sec.  75.360 and 75.364.
c. Sec. 75.335(c) Welding
    ETS Sec.  75.335(c) prohibits the use of open flames or arc 
associated with welding, cutting, and soldering activities within 150 
feet of a seal. MSHA intends to apply this

[[Page 28805]]

requirement to seals when their construction has been completed. The 
use of an oxygen acetylene cutting torch to cut a metal strap at a seal 
was the most likely ignition source in the Darby Mine No. 1 explosion 
in 2006. Although the metal strap should have been removed before the 
seal was constructed, the event underscores the importance of the 
potential dangers when working near seals, and emphasizes the dangers 
of using open flames near a seal. A methane enriched atmosphere can 
leak through the seal or surrounding strata into the active area of the 
mine. The methane may accumulate and form a methane layer outby the 
seal. If ignited, a flame can propagate into the sealed area. The 150-
foot limit is consistent with an existing requirement in Sec.  
75.1002(a)(1) that non-permissible equipment be excluded within 150 
feet of pillar workings or longwall faces. In determining the 150-foot 
distance, MSHA provides guidance in MSHA's Program Policy Manual 
(Volume V-Coal Mines February 2003, Release V-33) which states that the 
150-foot distance shall be measured by following the shortest distance 
that air can travel (tight string distance) through crosscuts, entries 
or other openings. MHSA does not believe that this requirement will 
present significant practical or technical problems for the underground 
coal mining industry. MSHA is requesting comments from the mining 
community on the appropriateness of the ETS requirement regarding open 
flames associated with welding, cutting and soldering activities within 
150 feet of a seal and the feasibility of this requirement. MSHA 
suggests that commenters provide specific rationale in support of their 
position, and include alternatives, if applicable.
d. Sec. 75.335(d) Sampling Pipes
    ETS Sec.  75.335(d) revises previous Sec.  75.335(b) and requires 
each newly constructed seal to have at least two sampling pipes. One 
sampling pipe must extend into the sealed area approximately 15 feet as 
required by previous Sec.  75.335(b). This provision of the ETS is 
based upon sampling procedures recommended in the 1979 MSHA study, 
``Interpreting the State of a Mine Fire.'' The study shows that in 
sampling situations involving fires behind sealed areas, sampling pipes 
should extend at approximately 15 feet toward the fire. This distance 
also applied to atmospheric sampling in sealed areas for non-fire 
situations. The area directly inby a seal is more likely to be affected 
by ingassing during normal barometric changes.
    Under this provision, the second sampling pipe must extend into the 
first connecting crosscut inby each seal and to the center of the first 
connecting crosscut in the middle of the intersection. MSHA has 
included this new provision in the ETS so that the operator can obtain 
a representative sample of the sealed area. The Agency believes that 
sampling points within the first connecting crosscut will provide a 
more representative sample of the sealed area because this atmosphere 
is less likely to be affected by ingassing. The District Manager may 
require more than two sampling locations in the ventilation plan under 
Sec.  75.335(b)(1).
    ETS Sec.  75.335(d) requires that each sampling pipe be equipped 
with a shut-off valve and an appropriate fitting for taking atmospheric 
samples behind the seals. A tapered fitting, for example, may be 
connected at the tip of the sampling pipe to easily accommodate a 
flexible tube attached to a gas analyzer.
    The ETS allows for other types of sampling methods that may be used 
to monitor sealed atmospheres. ETS Sec.  75.335(b) allows a mine 
operator to use an atmospheric (gas) monitoring system when 
appropriate. Although MSHA no longer requires that sampling pipes be 
installed with the sampling end of the pipe to be about 12 inches from 
the roof and in the centerline of the entry, the most appropriate 
placement of the sampling end of the pipe should be about 12 inches 
from the roof. The ETS affords flexibility to mine operators for the 
placement of the sampling end to allow more accurate sampling 
strategies to better protect miners. Therefore, the ETS requires that 
the location of sampling points be specified in the protocol provided 
under ETS Sec.  75.335(b)(5). MSHA requests comments regarding the 
appropriate number and location of sampling pipes for a final rule.
e. Sec. 75.335(e) Water Drainage Systems
    ETS Sec.  75.335(e) requires that a corrosion-resistant, water 
drainage system be installed in the seal at the lowest elevation within 
the set of seals. Water accumulations can affect the integrity of seals 
since they are not designed to impound water. Previous Sec.  
75.335(c)(2) required each water drainage pipe to have a water trap 
outby the seal. MSHA required the water trap to prevent the exchange of 
air through the seal and propagation of an explosion. New seal designs 
under the ETS, however, must meet performance requirements for a 
drainage system which prevents the exchange of air and the accumulation 
and impoundment of mine water inby the seals. The ETS also allows for 
use of new and innovative designs. MSHA has determined that the ETS 
provision enhances the level of protection afforded under the previous 
standard. ETS Sec.  75.336(a)(1)(i) requires that drainage system 
designs be approved by MSHA, and ETS Sec.  75.336(b)(3)(iii)(I) 
requires estimation of the volume of water flow in the ventilation 
plan. Depending on the size and mine floor elevations of the sealed 
area, it may be necessary for more than one seal in a set of seals to 
contain a water drainage pipe. These provisions provide flexibility and 
additional oversight by MSHA to help ensure safe and effective water 
drainage systems to protect miners from seal failure due to water 
impoundment. The ETS prohibits seals from impounding water.
    MSHA requests comments from the mining community on the ETS 
requirement for water drainage systems for seals, including effective 
alternatives for a final rule.

2. Sec. 75.336 Seal Design Applications and Installation Approval

    The ETS requires that seal design applications and installation 
procedures be approved by MSHA prior to construction. The ETS approval 
requirements for seals are derived from previous Sec.  75.335(a)(2), 
the July 2006 PIB, and Procedure Instruction Letter (PIL) No. I-06-V-
09, ``Procedures for Approval of Alternative Seals,'' issued on August 
21, 2006 (August 2006 PIL) and are consistent with existing 
requirements for approving coal mine impoundments in Sec.  77.216-2. 
Paragraph (a) requires that seal design applications be submitted to 
MSHA's Office of Technical Support for approval. Seal design 
applications must conform to the provisions provided in paragraph 
(a)(1) or (a)(2) which address seal design and installation approval. 
Once a seal design is approved by MSHA, a mine operator may use the 
design in accordance with new provisions in paragraph (b) of this 
section and the requirements of existing ventilation standards in 
Sec. Sec.  75.370, 75.371, and 75.372, which address the submission and 
approval of the ventilation plan.
    Previous Sec. Sec.  75.335(a), (b), and (c) that address design 
parameters of seals are transferred to ETS Sec. Sec.  75.336 (a) and 
(b) and are revised. These previous provisions required mine operators 
to either use a seal constructed of solid concrete blocks or seals 
constructed of alternative methods and materials if approved in the 
mine's ventilation plan. Under the new provisions, a manufacturer or 
mine operator may submit an application for approval

[[Page 28806]]

which can include any seal design. Seal designs specified in previous 
Sec.  75.335 may be submitted to MSHA for approval, provided the 
proposed design meets the strength requirements of ETS Sec.  75.335(a). 
The provisions of ETS Sec.  75.336(a) are derived from the July 2006 
PIB that established criteria to guide the District Managers' approval 
of the use of alternative seals in ventilation plans. These provisions 
are also derived from the August 2006 PIL that established uniform 
procedures for application of MSHA regulations related to review and 
approval of ventilation plans, which include alternative seals 
constructed in underground coal mines after July 19, 2006. Installation 
of seals is required to be approved by the District Manager in the 
ventilation plan in accordance with ETS Sec.  75.336(b).
a. Sec. 75.336(a)(1) Engineering Design Applications
    ETS Sec.  75.336(a)(1), which is derived from the August 2006 PIL, 
sets forth specific requirements that an engineering design application 
must include. The requirements in paragraphs (a)(1)(i) through (iii) 
are new and are based on sound engineering principles. They require 
that a seal design application shall: (1) Address design calculations 
and analyses, (2) include certification by a professional engineer, and 
(3) include a Seal Design Table. The documentation required under this 
paragraph includes design calculations, drawings, and specifications. 
Design calculations are required, since they provide the technical 
basis for developing drawings and specifications and serve as the 
record of the engineering design. Drawings and specifications provide 
detailed information necessary to construct seals, technical 
requirements for a seal, and important information and guidance to be 
followed during seal construction.
    These ETS requirements are consistent with existing approval 
requirements for various mining-related products under subchapter B--
Testing, Evaluation, and Approval of Mining Products for permissibility 
and for approval of impoundment designs under existing Sec.  77.216. 
Existing approval regulations require applicants to submit substantial 
engineering documentation as the basis for approval. The engineering 
documentation provides MSHA with evidence that the design meets 
accepted engineering practices and principles.
    ETS Sec.  75.336(a)(1)(i) requires each engineering design 
application to address essential design parameters. This information is 
required for MSHA to make a thorough assessment of the design 
application to ensure that the seal design will reliably withstand a 
specific overpressure, and to verify that the seal design is certified 
according to ETS Sec.  75.336(a)(1)(ii). MSHA will review the 
application for evidence that each of these design parameters is 
sufficiently addressed.
    The design application should show the placement of gas sampling 
pipes required under Sec.  75.335(b). Also, the application must 
address a water drainage system. The drainage system must be corrosion-
resistant and should not be subject to detrimental environmental 
conditions. The dimensions, material type, and components of the water 
drainage system should be specified. The application should show how 
the water drainage system will prevent both the exchange of air and the 
propagation of an explosion through the water drainage system. Also, 
the application should show how the water drainage system will be able 
to withstand the applicable overpressure in ETS Sec.  75.335(a).
    The design application must address air leakage and should specify 
the method and materials used to minimize air leakage along the 
perimeter of each seal and through any construction joints or cracks 
that could develop. Consistent with previous Sec.  75.335(a)(iv) that 
required that a sealant material should have a flame-spread index of 25 
or less, the mine operator must address the flame-spread index. The 
flame spread index is established through recognized laboratory testing 
such as that designated by ASTM E162-07, ``Surface Flammability of 
Materials Using a Radiant Heat Energy Source'' or equivalent.
    The design application must include appropriate information to 
address fire resistance, such as methods and materials used to provide 
at least one-hour fire resistance. The fire resistance is established 
through recognized laboratory testing. The seal material should not 
fail or allow transfer of sufficient heat while being subjected to a 
fire test incorporating an ASTM E-119-07 time/temperature heat input, 
or equivalent, for one hour.
    A pressure-time curve provides the necessary loading criterion for 
a seal design and must be provided in the seal design application. The 
pressure-time curve provides the reflected overpressure and constant-
volume pressure plotted as a function of a specific time period. 
Pressure-time curves for the 50-psi and 120-psi seal strength 
requirements of ETS Sec.  75.335(a) are provided in the 2007 NIOSH 
Draft Report. Alternative pressure-time curves may be used for designs 
provided the pressure-time curves are submitted to MSHA's Office of 
Technical Support for approval.
    The applicant must document the entry dimensions for which the seal 
design is applicable and the engineering design and analysis. MSHA 
expects the design documentation, the design assumptions, references of 
design standards and guidance, material properties and relevant test 
data, presumptive geotechnical properties and information, geotechnical 
test data used to substantiate presumed geotechnical properties, data 
to address the long-term durability of seal materials, loading 
criteria, design calculations, and the identification of computer 
software used and the computer input and output files with the critical 
design values indicated. The design should also address the factors 
used to account for the variability in material properties, geologic 
conditions, and the quality of construction. For example, the applicant 
must show that an appropriate approach was used to derive the 
geotechnical and material design values. The design should also show 
the methodology and the procedures used to evaluate all potential 
failure modes of the seal and strata. MSHA considers design standards 
and guidance documents as appropriate references, such as Army TM 5-
1300, ``Structures to Resist the Effects of Accidental Explosions,'' 
American Concrete Institute ACI 318-05, ``Building Code Requirements 
for Structural Concrete and Commentary,'' and American Concrete 
Institute ACI 440.2R-02, ``Design and Construction of Externally Bonded 
FRP Systems for Strengthening Concrete Structures.''
    Specifications must be provided in the seal design application to 
define the performance requirements for construction materials and 
equipment used. Test methods and reference to industry standards for 
materials (e.g., American Society for Testing and Materials) that will 
be used in seal construction must also be included in the application. 
For construction materials whose properties and performance are not 
well-researched or well-documented, the applicant would be required to 
provide data substantiating long-term durability and strength.
    Applications must provide construction specifications adequately 
addressing the preparation of the site for seal construction. For 
example, construction specifications must include rock and coal removal 
requirements for the foundation. Specifications for foundations must

[[Page 28807]]

address both the horizontal and vertical surfaces of the mine opening. 
Keys formed in rock and coal to increase the lateral restraint must be 
excavated with equipment that minimizes fracturing and breakout. The 
applicant must also specify the necessary actions to be taken to 
prevent water accumulation in the seal construction area since water 
accumulation could affect material strength. Necessary storage 
conditions for construction materials, such as moisture, heat, or shelf 
life should be specified. Construction specifications should also 
address formwork when a seal construction involves cast-in-place and 
pneumatically-applied materials.
    The application must list provisions that specify quality control 
procedures for construction and include requirements for material 
sampling and testing. Material testing should be conducted by personnel 
certified by professional organizations such as the American Concrete 
Institute and by Nationally-Recognized Testing Laboratories to ensure 
proper quality control testing.
    The seal design should establish the maximum allowable convergence 
a seal may undergo without affecting the structural integrity of the 
seal. The design should also address other physical limitations for a 
seal, such as the time required following construction to achieve the 
specified material strength. For example, the time required for an 
explosive atmosphere to develop in a sealed area must exceed the time 
required for the seal construction material to achieve its specified 
strength. The specified strength of a material must take into account 
variability in strength of the material. The required material strength 
ensures that the installed material strength of the seal exceeds the 
specified design strength.
    The professional engineer designated in ETS Sec.  75.336(a)(1)(ii) 
is responsible for the preparation, signing, dating, sealing, and 
issuing of engineering documents for the design of a seal. Engineering 
decisions and actions that must be made by and must be the 
responsibility of the professional engineer are:
    1. The selection or development of design standards or methods, and 
materials to be used in seal construction;
    2. Development and preparation of the structural analyses and 
design computations, drawings, and specifications;
    3. The selection or development of techniques or methods of testing 
to be used in evaluating materials used either during seal construction 
or following completion of seal construction; and
    4. The development of construction procedures.
    ETS Sec.  75.336(a)(1)(iii) requires that a Seal Design Table that 
discusses characteristics related to mine-specific construction be 
included in the application. These characteristics include the maximum 
entry width and height for which the specific design is applicable, 
specified strength of the seal material, thickness of the seal, and the 
reinforcement and foundation anchorage requirements for the seal. The 
mine operator may provide additional information in the seal design 
application.

                                       Example Concrete Seal Design Table
----------------------------------------------------------------------------------------------------------------
                                               Specified unconfined
Entry dimensions (ft)    Thickness  (ft-in)    compressive strength      Reinforcement           Foundation
                                                      (psi)                                       anchorage
----------------------------------------------------------------------------------------------------------------
                       .....................  .....................  .....................  ....................
----------------------------------------------------------------------------------------------------------------

b. Sec. 75.336(a)(2) Full-Scale Explosion Test Application
    ETS Sec.  75.336(a)(2) provides requirements for seal applications 
that are based on full-scale explosion testing. ETS Sec.  
75.336(a)(2)(i) requires that explosion tests be certified by a 
professional engineer knowledgeable in structural engineering that 
full-scale tests were conducted in accordance with current, prudent 
engineering practices and the results are applicable to an underground 
coal mine. Current, prudent engineering practices should include the 
preparation, signing, dating, certifying and issuing of engineering 
documents for the design of a seal. The decisions and actions that are 
the responsibility of the professional engineer are the same as stated 
above.
    ETS Sec.  75.336(a)(2)(ii) requires that the application include 
technical information related to the methods and materials used during 
a successful full-scale explosion test. The testing should include, at 
a minimum, the following blast loadings: (1) The reflected overpressure 
due to the blast wave of a methane explosion, and (2) the constant-
volume pressure due to the exothermic reaction of the combustion of 
methane. The overpressures stated in ETS Sec.  75.335(a)(1) serve as 
the minimum peak reflected overpressures that a seal should be capable 
of withstanding. Ideally, the seal should be tested to its predicted 
ultimate strength to determine the actual strength of the seal. For 
example, seals should be tested with the face perpendicular to the 
direction of a blast wave and subjected to a reflected overpressure, 
rather than a side-on overpressure. The testing program must address 
projectile impact on the seals.
    ETS Sec.  75.336(a)(2)(ii) requires the applicant to provide 
technical information related to the methods and material used to 
construct and test the seals. The properties and laboratory test data 
of the materials are required. The laboratory test data should be 
provided by personnel certified by professional organizations such as 
the American Concrete Institute and by a Nationally-Recognized Testing 
Laboratory to ensure proper quality control testing. MSHA intends to 
substantiate the design values used in the analysis and the full-scale 
testing of the seals.
    ETS Sec.  75.336(a)(2)(iii) requires that the application include 
proper documentation. Proper documentation includes engineering 
analyses, construction drawings and specifications, and data that 
address seal material, fire resistance and flame-spread index. The 
applicant must establish the materials and materials properties 
required for adequate seal construction. Construction documentation is 
required to ensure that the seals are properly built and reliable, to 
address air leakage, and to verify that the material properties of the 
seal will meet the specified strength criteria.
    ETS Sec.  75.336(a)(2)(iv) requires the application to include an 
engineering analysis addressing differences between actual full-scale 
test support conditions and the range of support conditions that could 
be encountered in an underground coal mine. MSHA recognizes that the 
test site may have different support conditions than an underground 
coal mine. This information must ensure that a tested

[[Page 28808]]

seal design will reliably function as designed in an underground coal 
mine.
    ETS Sec.  75.336(a)(2)(v) requires a Seal Design Table be included 
in the application that discusses characteristics related to mine 
specific seal construction. These characteristics include the maximum 
entry width and height for which the specific design is applicable, 
specified strength of the seal material, thickness of the seal and the 
reinforcement and anchorage requirements for the seal. Additional 
information may be provided at the discretion of the designer.

----------------------------------------------------------------------------------------------------------------
                                               Specified unconfined
   Entry dimensions      Thickness  (ft-in)    compressive strength      Reinforcement      Foundation anchorage
         (ft)                                         (psi)
----------------------------------------------------------------------------------------------------------------
                       .....................  .....................  .....................  ....................
----------------------------------------------------------------------------------------------------------------

c. Sec. 75.336(a)(3)
    ETS Sec.  75.336(a)(3) is consistent with existing Sec.  
77.216(2)(b) and Approval Policy 1009, and specifies that MSHA will 
notify the applicant if additional information or testing is required. 
The applicant must provide this information, arrange for any additional 
or repeat tests related to this additional information, and notify the 
Agency of the location, date, and time of such tests.
d. Sec. 75.336(a)(4)
    The applicant, under ETS Sec.  75.336(a)(4), will be notified by 
MSHA in writing, whether the design is approved or denied. If the 
design is not approved, MSHA will specify, again in writing, the 
deficiencies of the application, or necessary revisions for approval. 
This provision is consistent with existing Sec.  77.216-2 and Approval 
Policy 1009.
e. Sec. 75.336(a)(5)
    ETS Sec.  75.336(a)(5) is consistent with existing Sec.  77 .216-3 
and requires the approval holder to promptly contact MSHA's Office of 
Technical Support, in writing, of all deficiencies, such as design or 
material flaws, when they become aware. MSHA's intent is that 
``promptly'' means the approval holders are expected to contact MSHA as 
soon as they have knowledge that a deficiency exists.
f. Sec. 75.336(b) Mine Specific Application; Seal Design Approval in 
the Ventilation Plan
    The ETS requires the mine operator to use an approved seal design, 
provided the District Manager approves installation of the design in 
the ventilation plan. The requirements in this section are consistent 
with Procedure Instruction Letter No. I06-V-9 (August 2006) that 
established uniform procedures for application to MSHA for approval of 
alternative seals constructed after July 19, 2006.
    ETS Sec.  75.336(b) is new and requires that mine operators use an 
MSHA-approved seal design. The mine ventilation plan that addresses the 
installation of seals must be approved by the District Manager prior to 
the mine operator initiating seal construction in the mine. The Darby 
and Sago mine explosions revealed problems with seal construction. 
MSHA's accident investigation report into both explosions states that 
the seals were constructed without mortar between the joints. MSHA 
determined that overpressure was a problem in both the Sago and Darby 
accidents. Adequate seals are crucial to contain explosions and prevent 
potentially explosive or toxic gasses from migrating into the active 
working areas of underground coal mines. MSHA is requiring that seal 
installation be approved in the ventilation plan to help ensure that 
seals are appropriately installed to effectively protect miners.
    Under ETS Sec.  75.336(b), the mine operator must use an approved 
seal design provided the installation is approved in the ventilation 
plan. These design documents will serve as historical references. Seal 
design applications must provide information that the seal will 
withstand the appropriate overpressure from an explosion in accordance 
with current, prudent engineering practices, design codes and 
guidelines, and the seal strength requirements of ETS Sec.  75.335(a).
    ETS Sec.  75.336(b)(1) requires the mine operator to retain a copy 
of the seal design approval information for as long as the seal is 
needed to serve the purpose for which it was built. MSHA intends to 
review mine operators' seal design approvals at the mine site to 
evaluate and address construction and other installation-related 
issues.
    ETS Sec.  75.336(b)(2) requires the mine operator to designate a 
professional engineer to conduct or have oversight of seal 
installation. The professional engineer is required to certify that the 
site-specific seal design complies with the provisions of paragraph(a) 
of this section. The professional engineer will help ensure that proper 
seal design implementation and related analyses are performed by 
qualified personnel and ensure seals are constructed according to the 
drawings and specifications. A copy of the certification must be 
submitted to the District Manager with the information provided in ETS 
Sec.  75.336(b)(3). The mine operator must keep a copy of the 
certification for as long as the seal is needed to serve the purpose 
for which it was built.
    ETS Sec.  75.336(b)(3) lists specific information that a mine 
operator must address in the ventilation plan. This information will be 
used by the District Manager to evaluate a seal installation and 
determine whether the seal design is appropriate for a particular site. 
Paragraph (b)(3)(i) requires that mine operators include the MSHA 
Technical Support Approval Number of the seal design. Paragraph 
(b)(3)(ii) requires a mine map certified by a professional engineer 
showing the proposed seal location and surrounding areas to be 
submitted.
    ETS Sec.  75.336(b)(3)(iii) requires specific information about the 
mine site. This information may be included on the mine map of the area 
to be sealed. Paragraph (b)(3)(iii)(A) requires that the type of seal 
be included in the ventilation plan. The type of seal must be 
identified by the approval number provided in (b)(3)(i) of this 
paragraph.
    ETS Sec.  75.336(b)(3)(iii)(B) requires mine operators to include 
safety precautions to be taken before seals achieve their specified 
strength. Safety precautions could include withdrawing miners a safe 
distance from the seal installation site or actively inerting the 
sealed area.
    ETS Sec.  75.336(b)(3)(iii)(C) requires that the mine operator 
include methods to address site-specific conditions that may affect the 
strength and applicability of a seal. These conditions could include: 
the mine opening dimensions and an estimate of dimension increases due 
to site preparation, such as the removal of weak roof, floor strata or 
friable coal; consideration of the local geology and mine conditions of 
the seal installation location; and a description of the ground 
conditions, which may include anchorage pull-test information. Other 
factors such as variability in material properties, geotechnical

[[Page 28809]]

properties, geologic conditions, and the quality of construction should 
be considered to ensure that a seal can reliably withstand the 
overpressures. Adverse ground conditions, such as convergence, may be 
unsuitable for certain types of seals. These conditions should be 
addressed and resolved by the professional engineer.
    ETS Sec.  75.336(b)(3)(iii)(D) requires that the mine operator 
specify construction techniques for each type of seal. This could 
include equipment, procedures, materials and general mine safety 
information. This information is required to help ensure that the seal 
is properly constructed.
    ETS Sec.  75.336(b)(3)(iii)(E) requires the mine operator to 
address seal construction site preparation which should include 
localized mine water drainage and foundation preparation as required in 
each seal design. The foundation refers to the horizontal and vertical 
surfaces of the mine opening. Keys or hitches formed in rock and coal 
to increase the lateral restraint should be excavated with equipment 
that minimizes the fracturing and breakout of strata. Strata with open 
joints should be addressed.
    ETS Sec.  75.336(b)(3)(iii)(F) requires the mine operator to 
include the sequence of seal installations. Ventilation controls should 
be managed during seal construction until the final seals are 
installed.
    ETS Sec.  75.336(b)(3)(iii)(G) requires the mine operator to 
provide the projected completion date of each set of seals. Changes in 
ventilation controls may be necessary as seal construction progresses 
and may occur on a daily basis. MSHA intends for seals to be installed 
in a timely manner.
    ETS Sec.  75.336(b)(3)(iii)(H) requires the mine operator to 
specify supplemental roof support to be installed inby and outby each 
seal. Supplemental support provides long-term stability for each seal, 
and it is important that the Agency know the type of support used in 
the sealed area. The competency of the strata surrounding the seal is 
critical to its long-term stability.
    ETS Sec.  75.336(b)(3)(iii)(I) requires the mine operator to 
provide an estimation of the water flow and the dimensions of the water 
drainage system. This information will be used by MSHA to evaluate 
whether the water drainage system is appropriate since seals must not 
impound water.
    ETS Sec.  75.336(b)(3)(iii)(J) requires the mine operator to 
specify the methods used to ventilate the entries outby the seals after 
completion. Ventilation is necessary to control methane which outgasses 
from the sealed area. Information about the ventilation methods will 
help MSHA assess the adequacy of the ventilation plan.
    ETS Sec.  75.336(b)(3)(iii)(K) requires the mine operator to 
specify methods and materials used to maintain each type of seal. Mine 
operators should include information to address minor repair of cracks, 
spalls, and small air leaks through and about the perimeter of each 
seal to control leakage. Roof deterioration, roof falls, and sloughing 
of the coal pillars may adversely affect the overall strength of a seal 
by compromising the structural integrity of the supporting strata.
    ETS Sec.  75.336(b)(3)(iii)(L) requires the mine operator to 
specify methods to address shafts and boreholes within the sealed area. 
The mine operator should specify how and when each borehole will be 
plugged and each shaft will be filled during the sealing process.
    ETS Sec.  75.336(b)(3)(iii)(M) requires the mine operator to 
provide any additional information requested by the MSHA District 
Manager for inclusion in the ventilation plan. This provision will 
ensure that any new developments in technology or any problems related 
to site-specific conditions in sealing may be addressed by the mine 
operator through the ventilation plan.
    MSHA requests comments on the appropriateness of the ventilation 
plan contents and whether additional information should be included. 
Commenters should submit information in support of their positions, 
including data related to projected cost and technological feasibility.

3. Sec. 75.337 Construction and Repair of Seals

    This ETS includes new provision Sec.  75.337 addressing 
requirements for: preparation of the area to be sealed; supervision of 
seal construction and repair; certification that the seal was built in 
accordance with the provisions in ETS Sec.  75.336(b); notification to 
MSHA concerning construction schedules; and training miners and senior 
mine management officials in the construction and repair of seals. 
Repairs addressed by this section are limited to non-structural 
repairs. The scope of these repairs is related to general maintenance 
and includes: Excessive air leakage through and around seals; repair of 
minor cracks; spalling of seal coating; water drainage systems; and 
sampling pipes. This section of the ETS is based on MSHA experience 
with mine ventilation plans under existing Sec. Sec.  75.334, 75.370, 
and 75.371, and regarding worked-out areas and areas where pillars are 
being recovered. MSHA believes these ETS provisions are necessary to 
adequately protect miners' health and safety.
a. Sec. 75.337(a) Site Preparation
    ETS Sec.  75.337(a) requires removal of insulated cables from the 
area to be sealed and removal of metallic objects through or across 
seals. Paragraph (a)(1) requires removal of all insulated cables, 
including hanging, buried, and cables within conduit, from the sealed 
area before seals are built. This requirement is included in the ETS 
because a spark could be developed if a length of insulated cable were 
inductively coupled to an electromagnetic pulse, such as those 
generated by lightning strikes. These sparks can ignite an explosive 
methane/air mixture. After the SAGO explosion, MSHA contracted with 
Sandia Corporation, the operator of Sandia National Laboratories 
(Sandia), to perform modeling and testing to determine if it were 
possible for lightning to cause electrical energy to enter the Sago 
Mine and cause an explosion. Sandia has preliminarily determined that a 
lightning strike could create enough energy in the sealed area to 
ignite methane.
    Typically, as mine operators complete mining activities in an area, 
they recover the more valuable cables and may only leave behind damaged 
or deteriorated cables. MSHA anticipates that the removal of abandoned 
cables will not be a significant burden for mine operators and would 
not adversely affect future mining activities. This requirement would 
improve miners' safety because removal of cables reduces the hazard of 
an explosion caused by an electrical discharge.
    MSHA believes that removal of insulated cables and metallic objects 
through or across seals is feasible and will not involve significant 
technical or practical problems. MSHA solicits comments on these 
measures.
    ETS Sec.  75.337(a)(2) requires metallic objects that pass through 
or across a seal to be removed. Gas sampling pipes and water drainage 
systems required by ETS Sec.  75.335(d) and (e), and form ties approved 
in the seal design provided by ETS Sec.  75.336 are allowed in the 
sealed area.
    Metallic material can provide a conduit for electrical current to 
enter the sealed area and ignite methane/air mixtures. It is necessary 
to limit the use of conductors that may pass around or across seals. 
Screen, straps, rails, channels, and water pipes are typical metallic 
materials that are required to be removed under the ETS. Removal of 
metallic objects through or across seals before they are built will 
reduce the

[[Page 28810]]

hazard of methane explosions and improve miner safety.
b. Sec. 75.337(b) Supervision of Construction and Repair of Seals
    ETS Sec.  75.337(b) requires a certified person designated by the 
mine operator to directly supervise the seal construction and repair 
process and make appropriate examinations. After the Sago Mine and 
Darby No. 1 Mine explosions, MSHA inspected seals in underground coal 
mines across the country. The Agency has determined that some seals 
were not built correctly. This new provision requires that seal 
construction for all seals built after May 22, 2007 be directly 
supervised by a certified person. Existing Sec.  75.100 defines 
certified person and requires that person to obtain certification from 
the Secretary of Labor or the State in which the coal mine is located. 
A certified person shall directly supervise the construction of each 
seal throughout the construction or repair process. This new provision 
will assure that all activities related to seal construction, repair, 
and examination are performed safely and in accordance with appropriate 
requirements.
    ETS Sec.  75.337(b)(1) requires a certified person to examine each 
seal construction or repair site prior to beginning seal construction 
or repair to ensure that the site conditions are in accordance with the 
approved ventilation plan.
    ETS Sec.  75.337(b)(2) requires a certified person to observe the 
construction or repair process during each shift that construction or 
repair take place. This provision will help ensure construction or 
repairs of seals conform to the approved seal design and site specific 
information provided under Sec.  75.336(b).
    ETS Sec.  75.337(b)(3) requires a certified person to perform an 
examination of each seal or repair to verify that the seal or repair is 
complete. The District Manager may require that each examination 
include an assessment of any supplemental roof support, ventilation of 
the seals, sampling pipes and appropriate fittings, and the water 
drainage system as provided in the ventilation plan under ETS Sec.  
75.336(b).
    ETS Sec.  75.337(b)(4) requires the certified person certify each 
seal construction or repair by initialing the date and time of their 
examination to verify that the required examinations were made.
    ETS Sec.  75.337(b)(5) requires a record be made in a book or a log 
provided for that purpose to affirm that the examinations were 
conducted. The record shall describe any deficiencies in site 
preparation, such as construction, repairs, seal completion, and 
hazardous conditions and any corrections made. The record must be made 
by the certified person conducting the examination when the examiner 
arrives on the surface at the end of the shift. The record shall be 
countersigned by the mine foreman or equivalent mine official. Records 
of the deficiencies and the corrective actions provide valuable safety 
information about seal conditions and sealed areas in the mine and the 
effectiveness of corrective measures.
    The recordkeeping requirement for examination of seals would allow 
MSHA to determine if examinations have been conducted, if results are 
valid, and that deficiencies in site preparation, construction, 
repairs, and seal completion found were corrected. By requiring that a 
record be countersigned, MSHA expects that the mine foreman or 
equivalent mine official must review the record before countersigning. 
This provision makes certain that a mine foreman or equivalent mine 
official is responsible for oversight of seal installation. The 
countersignature shall be made by the end of the mine foreman's or 
equivalent mine official's next regularly scheduled working shift.
    The records of examinations required under ETS Sec.  75.337(b)(5) 
shall be kept at the mine for one year. ETS Sec.  75.338 sets out 
additional seal recordkeeping duration requirements.
c. Sec. 75.337(c) Certification of Construction by Senior Mine 
Management
    ETS Sec.  75.337(c) requires that upon completion of construction 
of each seal, a senior mine management official, such as a mine manager 
or superintendent, certify that the construction, installation, and 
materials used were in accordance with the approved mine ventilation 
plan. This requirement assures that a senior mine management official 
takes responsibility for making sure that seals are constructed in 
accordance with the provisions under ETS Sec.  75.336(b).
d. Sec. 75.337(d) Notification to MSHA
    ETS Sec.  75.337(d)(1) requires the mine operator to notify the 
local MSHA field office between two and fourteen days prior to 
commencement of seal construction. This requirement provides MSHA the 
opportunity to observe seal construction. This is particularly critical 
when a mine operator is installing a new seal design or the mine 
liberates large amounts of methane.
    ETS Sec.  75.337(d)(2) requires the mine operator to notify the 
MSHA District Manager, in writing, within 5 days of completion of each 
set of approved seals. This provision allows the District Manager to be 
informed when all construction is completed. This is a critical time 
period during the construction of seals. It involves the time period 
during which seals are achieving full strength and the atmosphere inby 
the seals may be transitioning into or through a potentially explosive 
methane/air mixture. MSHA may decide to inspect the newly sealed area, 
or sample the atmosphere.
    ETS Sec.  75.337(d)(3) requires the mine operator to submit to the 
MSHA District Manager quality control test results required in ETS 
Sec.  75.336. Material test results shall be sent to MSHA and must 
include all seal testing and tests of seal construction materials.
e. Sec. 75.337(e) Training
    Failure of a seal may result in significant injury, loss of life 
and/or significant economic loss. Based on recent explosion 
investigations, MSHA learned that numerous persons involved in 
constructing seals that failed were not adequately trained. As a 
result, installation, construction, and repair tasks and the level of 
quality control exercised during these activities are critical to 
preventing seal failures and protecting miners.
    Under ETS Sec.  75.337(e), the mine operator is responsible for 
providing training to miners constructing or repairing seals, certified 
persons supervising seal construction, repair, and examinations 
described in (b)(1) of this section, and senior mine management 
officials described in paragraph (c) of this section.
    The training shall address materials and procedures required in the 
approved seal design in the mine's ventilation plan. For example, 
material training could include how to construct reinforced concrete, 
masonry block, gunite, and cementitious foam seals. Additionally, 
training shall include procedures in tasks such as hitching, evacuating 
weak materials, supporting and stabilizing roofs, and installing 
sampling pipes and water drainage systems.
    Training under this paragraph is also required for persons 
repairing seals. In addition to the training required for constructing 
seals, further training may be necessary for repairing a damaged seal. 
This training could include tasks such as patching small cracks, 
sealing leaks, and maintaining water drainage systems.
    MSHA recognizes that the amount of time required for training in 
constructing or repairing seals will vary.

[[Page 28811]]

For this reason, MSHA is not proposing a minimum amount of time for the 
training. MSHA expects mine operators to adjust the time for this 
training based on the complexity of the seal design in the ventilation 
plan, construction or repair procedures, materials used, and existing 
knowledge and skill levels of persons receiving the training. Also, 
changes in the approved seal design or approved ventilation plan will 
require retraining.
    This paragraph also requires mine operators to certify the date 
that training was provided. Operators are required to retain these 
certifications for one year from the time training was conducted. This 
provision is similar to other certification requirements in Part 75 
where the operator certifies by signature and date that training was 
provided.
    MSHA requests comments on the provisions provided in this section. 
In particular, MSHA requests comments concerning the scope and possible 
alternatives to the requirements related to site preparation, 
examinations, and notification provisions.
    4. Sec. 75.338 Seals Records
    ETS Sec.  75.338(a) sets out the recordkeeping duration required 
for records created under ETS Sec. Sec.  75.335, 75.336, and 75.337. 
For the convenience of the mining community, these requirements are 
listed in the table entitled ``Table Sec.  75.338(a) Seal Recordkeeping 
Requirements.'' The table lists the record which must be kept, the 
section requiring the record, and the required retention time.

       Table to Sec.   75.338(a). Seal Recordkeeping Requirements
------------------------------------------------------------------------
            Record                 Section reference     Retention time
------------------------------------------------------------------------
(1) Protocol to monitor         75.335(b).............  Same as
 methane and oxygen and                                  ventilation
 maintain an inert atmosphere.                           plan
                                                         requirements.
(2) Training of certified       75.335(b)(2)..........  1 year.
 persons.
(3) Gas sampling records......  75.335(b)(6)..........  1 year.
(4) Approved seal design......  75.336(b)(1)..........  As long as the
                                                         seal is needed
                                                         to serve the
                                                         purpose for
                                                         which it is
                                                         built.
(5) Certification of            75.336(b)(2)..........  As long as the
 provisions of approved seal                             seal is needed
 design is addressed.                                    to serve the
                                                         purpose for
                                                         which it is
                                                         built.
(6) Record of examinations....  75.337(b)(5)..........  1 year.
(7) Seal construction           75.337(c).............  As long as the
 certification.                                          seal is needed
                                                         to serve the
                                                         purpose for
                                                         which it is
                                                         built.
(8) Certification of training.  75.337(e).............  1 year.
------------------------------------------------------------------------

    ETS Sec.  75.338(b) applies to seal records required to be kept 
under the ETS, except for the certification required under ETS Sec.  
75.337(b)(4) which must be retained at the seal site. Operators must 
retain records at the mine site. The mine operator may retain records 
in a computer system elsewhere, provided they are immediately 
accessible from the mine site by electronic transmission. Records must 
be secure and not subject to alteration.
    ETS Sec.  75.338(c) requires that the operator allow access to any 
record to an authorized representative of the Secretary of Labor, the 
Secretary of Health and Human Services, the authorized representative 
of miners, or other interested parties, upon request. Mine operators 
are to promptly provide access to any record listed in the table in 
paragraph (a) of this section. MSHA expects that an operator show due 
diligence in providing access to required records. Whenever an operator 
ceases to do business, the operator will be required to transfer all 
records required to be maintained by this part to any successor 
operator.

5. Conforming Changes to Other Sections in Part 75

    Existing paragraph (ff) of Sec.  75.371 requires the mine operator 
to provide a description of methods and materials to be used to seal 
worked out areas when they are different from those specified in 
paragraph (a)(1) of Sec.  75.335. The provisions in existing paragraph 
(a) of Sec.  75.335 are revised and moved to paragraph (b) of Sec.  
75.335 and paragraph (b)(3) of Sec.  75.336. Therefore, paragraph (ff) 
is revised to reference sampling requirements provided by paragraph (b) 
of Sec.  75.335 and ventilation plan contents requirements provided by 
paragraph (b)(3) of Sec.  75.336.

V. Executive Order 12866

    Executive Order (E.O.) 12866 (58 FR 51735) as amended by E.O. 13258 
(Amending Executive Order 12866 on Regulatory Planning and Review (67 
FR 9385)) requires regulatory agencies to assess both the costs and 
benefits of regulations. To comply with Executive Order 12866, MSHA has 
prepared a Regulatory Economic Analysis (REA) for the ETS. The REA 
contains supporting data and explanation for the summary materials 
presented in sections V-IX of this preamble, including the covered 
mining industry, costs and benefits, feasibility, small business 
impact, and paperwork. The REA is located on MSHA's Web site at http://www.msha.gov/regsinfo.htm.
 A copy of the REA can be obtained from 

MSHA's Office of Standards, Regulations and Variances. MSHA requests 
comments on all the estimates of costs and benefits presented in this 
ETS and in the REA.
    MSHA has determined that the ETS would not have an annual effect of 
$100 million or more on the economy and, therefore, it is not an 
economically ``significant regulatory action'' pursuant to Sec. 2(f) of 
E.O. 12866.

A. Population-at-Risk

    The ETS applies to all underground coal mines in the United States. 
Based on preliminary MSHA data, there were 670 underground coal mines, 
employing 42,667 miners, operating in the U.S. in 2006. Of these, 372 
underground coal mines use seals. These 372 mines employ 33,684 miners, 
of which 30,095 work underground.

B. Benefits

    To provide a preliminary quantitative estimate of benefits, MSHA 
analyzed the explosions in sealed areas that have taken place since 
1993, and especially studied the two accidents in 2006 where the seals 
failed and fatalities occurred: the Sago mine explosion, where 12 
miners died, and the Darby No. 1 mine explosion, where 5 miners died. 
It is reasonable to assume that if the ETS had been in effect, all 17 
of these miners' lives might have been saved. Fourteen of these lives 
might have been saved by the 2006 ETS and final rule on emergency mine 
evacuation. However, three of the miners that perished in the Sago and 
Darby accidents died

[[Page 28812]]

immediately from the explosion impact. They could not have been saved 
by the emergency mine evacuation rule. For purposes of estimating 
benefits, MSHA attributes the saving of three miners' lives to this ETS 
and splits the remaining 14 lives between this ETS and the 2006 
emergency mine evacuation rule. Hence, MSHA attributes the saving of 10 
lives to this ETS (3 + (14 / 2) = 10).
    MSHA has good data on explosions in sealed areas only since 1993. 
During the period 1993-2006 (14 years) there were 13 explosions in 
sealed areas. However, only 11 of these explosions caused any seal 
damage and thus had the potential to cause