Approval, Exhaust Gas Monitoring, and Safety Requirements for the Use of Diesel-Powered Equipment in Underground Coal Mines

SUMMARY: This final rule establishes new requirements for the approval

of diesel engines and other components used in underground coal mines;

requirements for monitoring of gaseous diesel exhaust emissions by coal

mine operators; and safety standards for the use of diesel-powered

equipment in underground coal mines. The final rule is derived in part

from existing MSHA regulations, and provides protection against

explosion, fire, and other safety and health hazards related to the use

of diesel-powered equipment in underground coal mines. The final rule

also amends certain equipment safety standards in part 75 previously

applicable only to electric-powered equipment to apply to diesel-

powered equipment. The new standards are consistent with advances in

mining technology, address hazards not covered by existing standards,

and impose minimal additional paperwork requirements.

EFFECTIVE DATES: This regulation is effective April 25, 1997, except

for subparts E and F of part 7, the removal of part 31, the amendments

to part 36, and Sec. 75.1907 which are effective November 25, 1996.

Incorporations by reference were approved by the Director of the

Federal Register as of April 25, 1997.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office

of Standards, Regulations, and Variances, Mine Safety and Health

Administration, 4015 Wilson Boulevard, Arlington, VA 22203-1984. Ms.

Silvey can be reached at [email protected] (Internet E-mail), 703-235-

1910 (voice), or 703-235-5551 (facsimile).

SUPPLEMENTARY INFORMATION:

I. Background

Coal mine operators began to introduce diesel-powered equipment

into underground mines in the early 1970's. The number of diesel units

operating in underground coal mines has increased from approximately

150 in 1974 to over 2,900 units operating in 173 mines in 1995. MSHA

projects that the number of diesel units operating in underground coal

mines could increase to approximately 4,000 in 250 underground coal

mines by the year 2000.

Although diesel-powered equipment does not have the inherent

electrocution hazard of electric-powered equipment, it nonetheless

presents a number of safety and health risks. By introducing an

internal combustion engine into an environment where explosive levels

of methane can be present, diesel-powered equipment brings with it

risks of fire or explosion. Diesel engines also have high temperature

exhaust components which, in the presence of coal and other

combustibles in the underground mine environment, present a fire

hazard. The handling and storage of diesel fuel underground also

present potentially serious fire hazards. Finally, diesel engines

produce exhaust gases containing carbon monoxide, oxides of nitrogen,

and particulate matter, presenting potentially serious health risks to

miners.

Before publication of this final rule, MSHA's regulations contained

limited safety and health and machine approval requirements that

specifically addressed the use of diesel-powered equipment in

underground coal mines. In the 1980's, the increase of the numbers of

this equipment in underground coal mines, coupled with the health and

safety risks associated with its use, highlighted the need for a

regulatory approach specifically tailored to diesel-powered equipment

operated in underground coal mines.

In response to this need, the Secretary of Labor convened a Federal

advisory committee in 1987 to evaluate and make recommendations for the

safe and healthful use of diesel-powered equipment in underground coal

mines. The Diesel Advisory Committee addressed approval issues--

covering equipment design and performance; use issues--addressing the

safe use of diesel equipment in the mine environment; and health

issues--concerning the evaluation and control of health hazards

associated with diesel equipment. In July 1988, the Committee issued a

report of its recommendations entitled ``Report of the Mine Safety and

Health Advisory Committee on Standards and Regulations for Diesel-

Powered Equipment in Underground Coal Mines''. In its report the

Committee concluded that MSHA should develop regulations to govern the

approval and use of diesel-powered equipment in underground coal mines,

and identified a number of specific areas to be addressed.

On October 4, 1989, the Mine Safety and Health Administration

published a Notice of Proposed Rulemaking in the Federal Register [54

FR 40950] that included criteria for the approval of diesel engines and

other related equipment; addressed exposure limits, monitoring, and

recordkeeping requirements for certain diesel emissions; and provided

corresponding safety standards for the use of diesel-powered equipment

in underground coal mines, including the safe storage and transport of

diesel fuel, and the training of persons performing work on diesel

equipment. On the same day, MSHA also published an Advance Notice of

Proposed Rulemaking [54 FR 40996] soliciting comment on the approach

and scope of an MSHA approval program for diesel machines. MSHA held

four public hearings on the proposed rule: in Salt Lake City, Utah;

Pittsburgh, Pennsylvania; Chicago, Illinois; and Birmingham, Alabama.

This final rule, which includes specifications for the approval of

diesel engines as well as provisions for the safe and healthful use of

such equipment in underground coal mines, is derived from the data,

information, and public comments compiled during the rulemaking

process. The final rule, like the proposal, takes an integrated

approach to the control of diesel safety and health hazards, requiring

clean-burning engines on diesel-powered machines, maintained by persons

who have been adequately trained for the task. Sufficient ventilating

air is required where diesel-powered equipment is operated to control

the potential health hazards of diesel exhaust. Sampling every shift

confirms the effectiveness of the mine ventilation system in addressing

these hazards.

Part 7 Equipment Approval

MSHA regulations require the Agency's approval of the design of

electrical equipment to be used in the production areas of underground

coal mines. This equipment must be designed to eliminate fire and

explosion hazards. MSHA's approval program has been very successful in

reducing the number of fires, explosions and other hazards associated

with electric-powered equipment. The final rule establishes a similar

approach for diesel-powered equipment used in areas of underground coal

mines where permissible (explosion-proof) electric equipment is

required, ensuring the same level of safety in mines where diesel-

powered equipment is used.

[[Page 55413]]

The permissibility requirements for diesel-powered equipment used

in gassy non-coal mines in MSHA's part 36 regulations have been in

place for a number of years. Although specific regulations did not

exist for diesel-powered equipment operated in underground coal mines,

MSHA has used the ventilation plan approval process to require the use

of permissible diesel-powered equipment, approved under part 36, in

those areas of underground coal mines where permissible electric

equipment is required. However, mine ventilation plans have generally

only addressed fire and explosion protection for equipment operating

near the point of coal extraction (inby), and other locations where

methane may be present, and have not addressed other possible safety

hazards associated with the use of diesel-powered equipment in other

(outby) areas. Additionally, mine ventilation plans have not dealt with

such important concerns as the storage and handling of diesel fuel and

regular maintenance of diesel equipment.

The final rule requires that only approved engines be used in

diesel-powered equipment in underground coal mines, and establishes

approval requirements for diesel engines to be used in both permissible

areas (inby) and nonpermissible areas (outby) under part 7, subpart E.

The subpart E approval requirements are modeled after existing approval

requirements in part 36 for engines used in gassy non-coal mines.

Certain other safety features, such as flame arresters, spark

arresters, and water scrubbers, must be added to the engines used in

permissible areas to ensure that they can be operated safely in the

coal mine environment. An engine in combination with these safety

features is termed a diesel power package. A separate approval was

established in the final rule for the power package because the power

package manufacturer is normally a company other than the engine

manufacturer and controls the assembly of the power package. In

addition, approval requirements for power packages under part 7,

subpart F, are incorporated into machines approved under existing part

36. This is similar to the approach taken for electrical equipment

where explosion-proof components are incorporated into machines

approved under part 18.

In order to protect miners from harmful contaminants emitted from

diesel engines, the approval requirements in the final rule contain

test procedures and limits on the concentrations of carbon monoxide and

oxides of nitrogen. Based on commenters' recommendations, the final

rule requires that the same test cycle be used for testing both the

gaseous and particulate emissions. In response to commenters'

recommendations, the final rule is based on ISO 8178, an international

consensus standard, which establishes a common test cycle for the

measurement of gaseous and particulate emissions. All equipment testing

under part 7 is intended to be conducted at test sites other than MSHA

facilities, such as manufacturers' laboratories, independent testing

laboratories, or other government or university laboratories.

Part 70 Exhaust Gas Monitoring.

The final rule addresses the monitoring and control of gaseous

diesel exhaust emissions. The final rule requires area sampling as part

of the onshift examination during every work shift. These monitoring

provisions will ensure, in a reliable and systematic manner, that

miners will be protected from exposure to harmful levels of gaseous

contaminants.

The final rule requires that mine operators take representative

samples of carbon monoxide and nitrogen dioxide in strategic locations

to determine concentrations of these contaminants in miners'

workplaces. The sampling locations are based on knowledge of the

specific operation of diesel equipment underground and the behavior of

gaseous emissions generated by these machines. Samples exceeding an

action level of 50 percent of the threshold limit values

(TLV) for carbon monoxide and nitrogen dioxide trigger

corrective action by the mine operator.

Part 75 Safety Requirements

The final rule specifies minimum ventilating air quantities in

areas where diesel equipment is operated, and requires that the

quantities be incorporated into the mine operator's approved mine

ventilation plan. As part of the equipment approval process in part 7

of the final rule, diesel engines used underground are tested for

gaseous and particulate emissions. The required minimum ventilating air

quantity is determined based on the results of these emission tests and

is included on the approval plate for each unit of diesel-powered

equipment. The approval plate quantity of ventilating air is the air

quantity needed to dilute the exhaust gases to their permissible

exposure limits. This air quantity should be used in ventilation system

design by the mine operator and in the evaluation and approval of

minimum air quantities in ventilation plans by MSHA.

Under the final rule individual units of diesel equipment must be

ventilated, as a general rule, with the air quantity specified on the

equipment's approval name plate. The quantity of air required in areas

where multiple units of equipment are operated is based on a simple

addition of approval plate air quantities. The final rule also allows

for adjustments in air quantities for multiple units of equipment, if

sampling of contaminants indicates that lesser air quantities will

result in dilution to the necessary levels. In addition, the final rule

establishes specific locations where air quantities must be measured.

Under the final rule, low sulfur fuel must be used to operate

diesel-powered equipment underground. Low sulfur fuel, which is readily

available and widely used throughout the United States, will lower

gaseous and particulate emissions, helping to protect miners from

exposure to harmful diesel exhaust contaminants. In addition, the final

rule prohibits the use of flammable liquids as additives in diesel fuel

used underground and requires that only additives registered with the

Environmental Protection Agency in accordance with 40 CFR Part 79 be

used in diesel-powered equipment.

The use of diesel fuel underground can present risks to miners'

safety, because the spilling of fuel on hot surfaces or electric

components, or the inadvertent ignition of stored diesel fuel, can

result in fire. Additionally, a fire started with a combustible

material other than diesel fuel that then spreads to diesel fuel stored

underground could be catastrophic. Diesel fuel handling and storage are

addressed in the final rule by specific requirements for diesel fuel

storage and the transportation of fuel from one location to another.

New design, installation, and maintenance requirements are

established under the final rule for fire suppression systems installed

on diesel-powered equipment and fuel transportation units. The

requirements in the final rule address the risk of fire on diesel-

powered equipment caused by, for example, hot exhaust components,

dragging brakes, and shorted electrical components igniting diesel

fuel, hydraulic fluid, brake fluid, lube oil, and other combustible

materials. The final rule also requires that automatic fire-suppression

systems be listed or approved by a nationally recognized independent

testing laboratory.

The final rule recognizes that regular maintenance of diesel-

powered equipment is essential. Inadequate equipment maintenance can

result in the creation of a fire or explosion

[[Page 55414]]

hazard, and the levels of harmful gaseous and particulate components in

diesel exhaust can rise when equipment is not adequately maintained. In

response, the final rule requires diesel-powered equipment to be

examined on the same weekly basis as electric equipment. The rule

specifically requires that air filters be changed and scrubbers be

flushed regularly, and that weekly gaseous emission tests be conducted

on certain diesel equipment while the engine is operating. The final

rule also requires that persons performing certain work on diesel-

powered equipment be qualified. Commenters agreed that requiring

diesel-powered equipment to be maintained in approved condition is

necessary to ensure that features installed to reduce the risk of fire,

explosion, and harmful emissions are operating properly. The final rule

does not adopt the proposal that MSHA approve the training plans used

for qualification. Under the final rule, training to establish

qualification for persons performing maintenance may be obtained

through the equipment manufacturer, community colleges, training

schools, or other training providers.

Amendments to Existing Part 75 Requirements

The final rule amends certain existing MSHA regulations in part 75

by extending their applicability to diesel-powered equipment. The final

rule requires that certain types of diesel-powered equipment be

equipped with methane monitors to detect dangerous levels of methane,

and also with cabs or canopies to protect miners from roof falls.

Additionally, the final rule clarifies that accumulation of coal dust

and other combustible materials is prohibited on diesel-powered

equipment. These safety features have been proven to save miners'

lives.

II. Discussion of the Final Rule

A. General Discussion

Recordkeeping Requirements in the Final Rule

Recordkeeping requirements in the final rule are found in

Secs. 7.83 and 7.97, Application requirements; Secs. 7.90 and 7.105,

Approval marking; Secs. 7.108, Power package checklist; Sec. 75.363,

Hazardous condition; posting, correcting and recording; Sec. 75.371

(r), (kk), (ll), (mm), (nn), (oo), and (pp), Mine ventilation plan,

contents; Sec. 75.1901(a), Diesel fuel requirements;

Sec. 75.1904(b)(4)(i), Underground diesel fuel tanks and safety cans;

Sec. 75.1911(i) and (j), Fire suppression systems for diesel-powered

equipment and fuel transportation units; Sec. 75.1912(h) and (i), Fire

suppression systems for permanent underground diesel fuel storage

facilities; Sec. 75.1914 (f)(1), (f)(2), (g)(5), (h)(1) and (h)(2),

Maintenance of diesel-powered equipment; Sec. 75.1915(a), (b)(5),

(c)(1), and (c)(2), Training and qualification of persons working on

diesel-powered equipment.

The paperwork burden imposed on manufacturers by the final rule

totals 558, which is an increase of 790 burden hours for the transfer

of hours from part 36 approval requirements, and a decrease of 232

hours for the removal of parts 31 and 32. In the first year the final

rule is in effect, the burden hours on mine operators will be 56,258,

of which large and small mine operators will incur 54,774 and 1,484

hours, respectively. After the first year, the burden hours to mine

operators will be 52,228, of which large and small mine operators will

incur 50,949 and 1,279 hours, respectively.

In the first year that the final rule is in effect, the total new

paperwork burden hours to mine operators and manufacturers will be

56,816 [56,258 + (790-232)]. After the first year, the total new

paperwork burden hours to mine operators and manufacturers will be

52,786 [52,228 + (790-232)].

MSHA solicited comments regarding the burden estimates or any other

aspect of the collection of information in the proposed rule. Proposed

paperwork requirements were submitted to the Office of Management and

Budget (OMB) for review in accordance with section 3504(h) of the

Paperwork Reduction Act of 1980 (PRA 80). Comments by OMB were filed

under comment numbers 1219-0111, 1219-0112, and 1219-0114. Control

number 1219-0100 was approved for proposed paperwork burden hours

required by part 7.

When proposed in 1989, the information collection requirements in

the diesel equipment regulations were calculated under PRA 80. The

final rule calculations are done in compliance with the Paperwork

Reduction Act of 1995 (PRA 95). Generally, changes in the final rule

burden hour and cost estimates from the proposed requirements result

from the revision necessitated by PRA 95. When the change represents a

regulatory change, it is so noted in the discussion of the appropriate

section within the preamble. For details on the calculation of

paperwork hours and costs see ``VII, Paperwork Reduction Act of 1995''

in the Regulatory Impact Analysis, which may be accessed electronically

or may be requested from MSHA's Office of Standards, Regulations, and

Variances.

Information is to be recorded, maintained for the period specified,

and made accessible, upon request, to authorized representatives of the

Secretary and to miners' representatives. Records are to be stored in a

manner that is secure and not susceptible to alteration, to preserve

the integrity of records for review by interested parties. This may be

done traditionally, by recording in a book, or electronically by

computer.

Examples of books that MSHA considers to be secure and not

susceptible to alteration include, but are not limited to, record books

that are currently approved by state mine safety agencies, and

permanently bound books. Examples of books that would not be considered

secure include loose-leaf binders and spiral notebooks.

Recognizing the trend of electronic storage and retrieval of

information through computers to be an increasingly common business

practice, MSHA permits the use of electronically stored records,

provided that they are secure and not susceptible to alteration, that

they are able to capture the information and signatures required, and

that information is accessible to authorized representatives of the

Secretary and miners' representatives. ``Secure'' is intended to mean

unalterable or unable to be modified. An example of acceptable storage

would be a ``write once, read many'' drive. Electronic records meeting

these criteria are practical and as reliable as traditional records.

Although the final rule does not require backing up the data, some

means is necessary to ensure that the condition and existence of

electronically stored information is not compromised or lost.

The 1995 Paperwork Reduction Act mandates agencies to encourage the

use of electronic submission of responses to minimize the burden of the

collection of information on respondents. Likewise, one of the major

objectives of Executive Order No. 12866 is to make the regulatory

process more accessible and open to the public as a means to reduce the

duplication of information between agencies. Elsewhere in this

preamble, MSHA announces the electronic availability of its rulemaking

documents with access instructions. The mining community and other

interested parties are encouraged to access on-line material as needed.

B. Section-by-Section Discussion

The following section-by-section portion of the preamble discusses

each provision affected. The text of the final

[[Page 55415]]

rule is included at the end of the document.

General Discussion of Diesel Equipment Approvals and Safety

Requirements

One of the three major areas addressed by the Diesel Advisory

Committee was the approval of diesel-powered equipment. Historically,

MSHA and its predecessor agencies have approved equipment intended for

use in areas of mines where methane and other substances pose the

danger of a fire or explosion. Through the approval process, equipment

is evaluated against technical requirements which, when met, will

render the equipment safe for its intended use in the mine environment.

In part as a result of this process, the approved equipment used in

mines in the United States is recognized as among the safest in the

world.

The Advisory Committee recommended that diesel-powered equipment

for use in underground mines be subject to MSHA approval in much the

same way that electrical equipment has been regulated. Under existing

standards, electrical equipment operated in the area of extraction and

in return airways of underground coal mines and gassy metal and

nonmetal mines, where methane may accumulate, must be approved as

permissible (explosion-proof). Electrical equipment operated elsewhere

in these mines is not required to be permissible, but is subject to

certain safety requirements to protect against fire, shock, and other

hazards of operation. The Advisory Committee further recommended:

Only diesel-powered equipment currently considered

permissible should be permitted to continue to operate in areas of coal

mines where permissible electrical equipment is required.

Separate specifications should be developed for diesel-

powered equipment used in areas where permissible equipment is required

and elsewhere.

An approval program for diesel-powered equipment and

portable, attended equipment should be established. This program should

identify those equipment design features most readily addressed by the

equipment manufacturers.

A time schedule should be developed to allow for

conversion of outby equipment presently in use through retrofits,

replacement, or additional interim safety features to meet the

applicable new requirements.

Equipment newly introduced underground after a fixed date

should meet the new standards.

Current safety requirements including those that are

applicable to electric equipment should apply to diesel equipment as

appropriate.

Only approved diesel engines should be used in underground

equipment and the approval requirements should include measurements of

exhaust gas pollutants and determination of a nameplate airflow

quantity. Measurement of particulate generation should also be included

in the engine approval process.

In the proposed rule, MSHA outlined three new subparts for existing

part 7, which set approval requirements for diesel engines and power

packages to be used in underground coal mines. The Agency also gave

notice of its intention to develop approval requirements for fully

assembled diesel-powered machines under a proposed subpart H for

permissible equipment and subpart I for large outby equipment.

Requirements for a limited class of light-duty equipment and stationary

unattended equipment were proposed in part 75. A special class of

equipment consisting of ambulances and fire fighting equipment was

proposed that could be used in emergency situations as part of the

mine's evacuation plan. The proposal also included provisions to permit

fire prevention features in lieu of surface temperature controls for

diesel locomotives.

Currently, MSHA approves diesel equipment under 30 CFR Part 36 for

use in ``gassy noncoal mines''. In underground coal mines, ventilation

plans specify the use of diesel-powered equipment approved as

permissible under part 36 in areas where permissible electric equipment

is required. In addition to the equipment approval under part 36, MSHA

regulations address the approval of diesel mine locomotives in 30 CFR

Part 31, and of mobile diesel-powered equipment for noncoal mines in 30

CFR Part 32. The proposal suggested that parts 31, 32, and 36 could be

revised or revoked, and solicited comment. Some commenters favored

retaining all of the existing diesel approval regulations since they

still could have some application for equipment used in metal and

nonmetal mines. Commenters generally agreed that the proposed rules for

part 7 should supersede any applicability these existing approval

regulations have for diesel engines used in underground coal mines.

The final rule for part 7 governs the approval of diesel engines

intended for use in underground coal mines. As recommended by the

Advisory Committee and as set forth in the proposed rule, the final

rule requires that all diesel engines used in underground coal mines be

approved.

Part 7 was originally promulgated in 1988 to establish application

procedures and requirements for MSHA approval of certain products for

use in underground mines, with testing conducted by the applicant or a

third party. Traditionally, MSHA's role in approving products for

safety emphasized testing by the Agency. Under part 7, testing is

performed by the applicant or by a third party selected by the

applicant, with MSHA maintaining the right to observe product testing.

This approach has permitted MSHA to focus on its product audit function

and keep pace with technological improvements in mining products.

As originally promulgated, part 7 applied to only two types of

products: brattice cloth and ventilation tubing under subpart B, and

battery assemblies under subpart C. Subsequently, three additional

subparts were developed covering multiple-shot blasting units; electric

motor assemblies; and electric cables, signaling cables, and cable

splice kits. As designed, part 7 expedites the approval process, while

providing greater assurance that the products are manufactured in

accordance with safety specifications.

The final rule for part 7 is organized into two subparts--E and F.

Subpart E sets diesel engine performance and exhaust emission

requirements. As more fully discussed elsewhere in the preamble,

subpart E creates two classes of engine approvals--one for Category A

engines and one for Category B engines. Engines intended for use where

permissible electric equipment is required in underground coal mines

must have a Category A approval; engines for use elsewhere in

underground coal mines must meet the requirements for Category B

engines.

Subpart F of the final rule sets standards for safe design of

diesel engines with respect to both fire and explosion hazards. The

final rule establishes requirements for approval of diesel ``power

packages'' on engines intended to be used where electric equipment is

required to be permissible under existing standards. The term ``power

packages'' refers to an approved engine and those components added to

the engine, such as flame arresters, which prevent the ignition of

methane, and surface temperature controls, which prevent the ignition

of accumulations of combustible materials and combustible liquids.

Permissible equipment is designed to be explosion-proof.

Subpart G of the proposed rule would have established requirements

for diesel

[[Page 55416]]

power packages intended for use in areas of underground coal mines

where permissible electrical equipment is not required. As this

equipment is not designed to be operated in a potentially explosive

methane environment, the proposed rule would not have required these

power packages to have explosion-proof features. However, these diesel

engines do present fire hazards which must be controlled. Under the

proposal, subpart G would have set standards for surface temperatures,

exhaust cooling, and safety system controls. As discussed more fully

below, the final rule does not retain subpart G, but addresses these

hazards through new requirements in part 75.

The proposed rule, responding to a recommendation of the Advisory

Committee, also established a category of ``limited class of light-duty

diesel-powered equipment.'' This category included machines with light-

duty cycles, such as pickup trucks and personnel carriers. This

equipment, while light-duty as compared to production equipment, can,

nevertheless, present a fire hazard. For this ``limited class'' of

diesel-powered equipment, instead of requiring surface temperature

controls, the proposal set standards for fire prevention features that

would prevent fuel, hydraulic fluid, and lubricants from coming into

contact with hot engine surfaces. Features such as special fuel system

protection, fire suppression systems, safe electrical systems, and

engine compartment sensors that shut down the engine in the event of

overheating were specified in the proposal for additional fire

protection. Other necessary safety features, such as braking systems,

were also addressed by the proposal. As recommended by the Advisory

Committee, these requirements were not made part of the approval

process described above, but were set forth in the proposal as safety

standards for underground coal mines, appearing in 30 CFR Part 75.

The final rule retains many of the provisions of the ``limited

class'' concept in the proposal, but broadens the scope of the

equipment subject to these requirements to include all equipment not

required to be permissible (outby equipment). This change eliminates

the need for formal approval of outby equipment, and simplifies the

final rule. This aspect of the final rule, and the diesel-powered

equipment approval requirements, are discussed in detail under the

section-by-section analysis which follows.

In the proposed rule MSHA notified the public of its intentions to

develop two new approval regulations. Subpart H would have established

requirements for the approval of fully assembled permissible diesel-

powered equipment, and subpart I would have established approval

requirements for fully assembled nonpermissible diesel-powered

equipment. These sections would have included machine features

currently required by part 36 for permissible equipment and similar

features, described above, for ``limited class'' equipment. These

subparts would have required the incorporation of appropriate power

packages as described in proposed subparts F and G.

In the advance notice of proposed rulemaking, which accompanied the

proposed rule, MSHA requested comments on this regulatory approach.

Commenters objected to a formal approval program for nonpermissible

equipment, but supported the incorporation of machine safety features

in the use requirements specified in part 75. Commenters also supported

the need for continuing the approval program for permissible equipment.

In response to these comments, the final rule retains part 36 as

the basis for the approval program for permissible diesel-powered

equipment and adopts the machine safety features specified for the

limited class of light-duty equipment in the proposal for all

nonpermissible equipment. Subparts H and I are not further developed.

Instead, the final rule adopts the fire prevention features specified

for limited class equipment for all nonpermissible equipment.

Additionally, the final rule enhances the fire prevention features that

now apply to all nonpermissible equipment. This approach eliminates the

need for subpart G of the proposal dealing with power packages for

outby equipment.

The final rule makes certain revisions to part 36 to update and

make these existing requirements more flexible. The final rule revises

part 36 to remove references to ``gassy noncoal mines and tunnels'',

thus making these existing regulations applicable to equipment intended

for use in coal as well as in metal and nonmetal mines. In addition,

part 36 is amended to afford equipment manufacturers the option of

incorporating in equipment submitted for approval either a part 7,

subpart F power package, or engine and safety component systems that

meet the existing requirements of part 36. Under the final rule, part

36-approved equipment with a part 7, subpart F power package will be

suitable for use in underground coal mines where permissible electrical

equipment is required. Part 36 equipment with engine and safety

component systems certified under part 36 will continue to be

recognized for use in metal and nonmetal mines where permissible

equipment is required.

These changes are responsive to commenters who recommended that

part 36 continue to be utilized for approving diesel-powered equipment.

The final rule revisions to part 36 also retain, as recommended by

commenters, a distinction between approval requirements for equipment

used in coal mines and approval requirements for metal and nonmetal

mining equipment.

The final rule revokes parts 31 and 32. MSHA previously identified

these regulations for elimination in its response to the President's

March 4, 1995, Regulatory Reform Initiative. Parts 31 and 32 are

outdated and, with the final rule changes to parts 7 and 36, are

obsolete. Only nine approvals have been issued under part 31 since its

inception, and none have been issued since 1977. No other MSHA

standards require part 31-approved equipment, and diesel mine

locomotive manufacturers have submitted approval applications under

part 36 for locomotives intended to be used where permissible equipment

is required. With the revocation of part 31, diesel mine locomotive

manufacturers may continue to acquire equipment approvals under part

36.

The part 32 approval requirements for mobile diesel-powered

equipment used in noncoal mines are likewise unnecessary. No MSHA

regulation requires the use of part 32 equipment, and no part 32

machine approval has been issued since 1981. Part 32 engine

certifications have continued to be issued by MSHA, however, and some

state and federal agencies' regulations make reference to part 32.

State and federal agencies that reference part 32 are directed to look

to part 7, subpart E, which contains engine requirements, and to

Secs. 75.1909 and 75.1910, which contain the requirements for other

machine features. Together, these final standards cover the

requirements previously found under part 32. These new sections of the

final rule will continue to accommodate those government agencies that

reference MSHA approval or certification regulations.

Likewise, manufacturers seeking part 32 engine approvals will be

able to acquire the requisite engine approval through the new part 7,

subpart E. Existing part 32 engine approvals continue to be valid.

A significant issue for the Advisory Committee and in the proposal

was the schedule set for compliance with the new standards for diesel-

powered equipment. The Advisory Committee

[[Page 55417]]

recommended that MSHA require diesel equipment newly introduced

underground to meet the new standards after a certain date. The

Committee further recommended that MSHA set a schedule for existing

diesel equipment to meet any new requirements.

The proposal called for the part 7 approval requirements to be

effective 60 days after publication of the final rule. The schedule for

requiring in-mine use of diesel equipment meeting the new requirements

was set by proposed Sec. 75.1907. Under these provisions, the new

requirements would have been met over a schedule ranging from six

months to five years after the effective date of the final rule.

The final rule follows the approach of the proposal, setting

effective dates for the new approval requirements, as well as the

schedule for requiring in-mine use of diesel-powered equipment which

meets the new requirements. In response to the comments and as a result

of not adopting proposed subparts G, H, and I, the final rule sets a

compliance schedule ranging from 60 days to three years after

publication of the final rule. In order to facilitate implementation of

the final rule, MSHA will begin accepting approval applications under

revised parts 7 and 36 immediately. In addition, MSHA will continue

power package testing until the Agency determines that a competitive

capacity exists in the private sector. At that time, MSHA will

discontinue power package testing and rely solely on the part 7 testing

provisions.

Subpart E Overview

Subpart E of the final rule is new and amends existing part 7. As

an amendment to these existing regulations, the general administrative

provisions of subpart A of part 7 apply to the new subpart E

application requirements.

Subpart E establishes engine performance and exhaust emission

requirements for MSHA approval of diesel engines for use in underground

coal mines. As discussed elsewhere in this preamble, diesel engines for

use in metal and nonmetal mines are approved under part 36.

The final rule, like the proposal, creates two classes of engine

approvals--Category A and B--for diesel engines to be used in

underground coal mines. Several commenters objected to the proposed

approval of diesel engines for use in outby areas, noting that outby

electrical equipment is not subject to approval under existing

standards. However, other commenters stated, and the Diesel Advisory

Committee acknowledged, that all diesel engines in underground coal

mines should meet certain safety and performance specifications. In its

report the Advisory Committee suggested that, depending on equipment

location and use, different requirements would be appropriate for

diesel engines. One commenter to the proposal recommended that all

diesel engines be approved as permissible.

For underground coal mines, MSHA believes that clean-burning

engines are critically important. Unlike electrical equipment, diesel

engines emit exhaust which contains toxic gases that can be harmful to

miners. Inappropriately designed engines can pollute the mine

atmosphere excessively, elevating toxic gases to levels that cannot be

controlled with normal ventilation practices.

To achieve the objective of clean-burning, appropriately designed

engines in mines, the final rule sets performance standards for all

diesel engines, whether they are operated in the face area or outby.

The emission test requirements for Category A and B engines are the

same, except that Category A engines are tested with methane injected

into the intake system. Equipment operating at or near the point of

coal extraction and in return air courses may encounter concentrations

of methane gas, which is liberated during mining. Testing an engine

with methane injected in its intake simulates operation of the engine

in these areas of coal mines. Operation in methane atmospheres causes

an increase in exhaust emissions, which requires higher ventilation

rates.

Under the final rule, diesel equipment used in areas where

permissible electrical equipment is required by existing standards

incorporate fire and explosion prevention features provided by a power

package. Such a power package must include a Category A engine and

components added to the engine to prevent the ignition of methane and

accumulations of combustibles. Power packages intended for use with

Category A diesel engines must be approved under part 7, subpart F of

the final rule.

Current safety standards require that intake air courses in areas

away from or outby the mining face be maintained free of explosive

concentrations of methane. Engines used on equipment operated in these

outby areas must have a Category B approval under the final rule.

Engines approved under Category B are emission tested without the

injection of methane into the engine's intake system.

The proposed technical requirements for diesel engines addressed

the control of gaseous exhaust emissions and quantification of the

engines' particulate matter generation. The proposed rule also set

specifications for the equipment used and the standard laboratory test

conditions for determining gaseous and particulate output for diesel

engines. The proposed requirements for measuring gaseous emissions were

derived from now-removed part 32 and existing part 36, and the proposed

requirements for measuring diesel particulate were based on the

Environmental Protection Agency's requirements published in 40 CFR Part

86. In addition, the proposal specified the engine operating parameters

as well as a method to calculate the ventilation rate and particulate

index for the engine.

Engine manufacturers do not manufacture engines specifically for

mining. Typically, ``off-road'', heavy-duty diesel engines are utilized

in mining equipment. Over-the-road utility vehicles and smaller general

industry equipment are also used in mines. At the time of the proposed

rule, the only certification test specifications designed for engines

used in mining were the MSHA engine certification standards in now-

removed part 32 and in existing part 36.

In the proposal, MSHA used its rules in now-removed part 32 and

existing part 36 for the steady-state test for gaseous diesel exhaust

emission. The test equipment specified in the proposal for diesel

exhaust particulate measurement was modeled after the transient test

equipment required in 40 CFR Part 86, subpart N.

Commenters to the proposal stated that a correlation should not be

made between MSHA's proposed rule and then-current EPA testing, because

the proposal used a test with specific points in a ``steady state'',

while EPA used a ``transient test.'' Commenters also recommended using

the same test cycle for both gaseous and particulate matter. In

addition, commenters generally recommended comparability of testing for

similar types of tests and indicated a desire to use international

standards whenever possible.

The International Organization for Standardization (ISO) has

prepared ``ISO 8178 Reciprocating Internal Combustion Engines--Exhaust

Emission Measurement'', which includes test specifications for off-road

diesel engines. The ISO is a recognized international standard-setting

body. Equipment manufacturers, as well as other standard-setting

bodies, make reference to and adopt the standards developed by the ISO.

[[Page 55418]]

ISO 8178 is an international test standard for measuring off-road

diesel engine emissions. It contains a detailed description of the test

equipment requirements and standard procedures for conducting a steady-

state test to determine both gaseous and particulate emissions. The ISO

8178 procedures also specify an 8-point test cycle for measuring both

gaseous and particulate emissions. ISO 8178 does not set emission

limits.

The final rule is based on the ISO 8178 ``Reciprocating Combustion

Engines--Exhaust Emission Measurement'', part 1 test procedures that

apply to gaseous and particulate emission testing for diesel engines.

This change from the proposal is responsive to commenters' concerns

about correlating the proposed rule and EPA diesel engine tests, and

simplifies the test procedures. For example, under the final rule the

gaseous emission tests are reduced to 8 test points from 39 test points

under the proposal. The particulate emission tests are also reduced

from 10 to 8 test points. In addition, the final rule permits the tests

for exhaust gaseous and particulate emission tests to be performed

concurrently following the same test cycle, rather than independently

following different cycles. A number of minor changes are made in

Secs. 7.86, 7.87, 7.88, and 7.89 of the final rule, so that the tests

performed under these sections conform to the ISO 8178 requirements.

Substantive changes to these sections are discussed in this overview

and in the section-by-section discussion that follows.

The final rule adds one requirement to the ISO 8178 test

procedures. Section 7.89(a)(5)(iii) requires that 1.0 percent of

methane be added to the intake air for testing Category A engines. This

addition to the ISO 8178 procedure should present no technical

difficulties for manufacturers or third-party laboratories. MSHA,

however, will provide technical assistance for setting up this aspect

of the test procedure upon request. The final rule also requires a test

to determine the maximum fuel-to-air ratio, and specifies requirements

for determining the gaseous ventilation rate and particulate index for

diesel engines.

Basing the final rule on an international consensus standard

enables diesel engine manufacturers to test with a single set of

procedures common to both the United States and foreign markets. Also,

existing test facilities established to perform tests to these

international standards can be used to perform the tests prescribed by

this final rule. In addition, use of the ISO 8178 test procedures leads

to better comparability with international testing practices, and

provides a more competitive posture for American products in foreign

markets. Many off-road engine manufacturers are already complying with

EPA and California Air Resources Board (CARB) requirements, which

include testing in accordance with ISO 8178 procedures.

One commenter to the proposal objected to permitting engine

manufacturers or third-party laboratories to test diesel engines for

conformance to approval standards, questioning the objectivity of such

an approach. MSHA experience over eight years with manufacturers and

third- party laboratory testing under existing part 7 and the Agency's

program for off-site testing (POST) of diesel engines confirms that

non-MSHA testing is performed competently and produces reliable

results. In addition, MSHA will initially witness all tests conducted

by manufacturers and third parties to ensure continued reliability of

test results. In all cases, MSHA will accept only results of tests

performed by manufacturers or third-party laboratories which have the

capability to competently perform the required tests with properly

calibrated instrumentation.

Section 7.81 Purpose and effective date. The part 7, subpart E

approval requirements are effective November 25, 1996. MSHA will begin

accepting applications under subpart E immediately, but will complete

any in-house part 32 applications, or evaluate such applications under

the new part 7, subpart E, at the applicant's choice. As discussed

elsewhere in this preamble, the requirements for the use of approved

diesel engines in underground coal mines are effective in 3 years.

Commenters to the proposal generally supported the approval

requirements of subpart E for diesel-powered equipment to be used in

underground coal mines. Several commenters suggested, however, that a

phase-in period, up to three years, be established. According to these

commenters, manufacturers would use the phase-in period to gain

experience with the new test procedures, become familiar with new

engine approval application procedures, and re-evaluate their existing

approvals.

The final rule does not incorporate a phase-in period for diesel

engine approvals. Diesel engine manufacturers and third-party testing

facilities are familiar with the ISO 8178 test procedures on which the

final rule is based, and have the capability to perform these tests in

their laboratories with minor changes. In fact, two engine

manufacturers and a testing laboratory have tested diesel engines for

MSHA approval using the ISO 8178 procedure.

With this diesel engine testing experience and capability already

present in the marketplace, MSHA finds no reason to provide an extended

phase-in period for the approval standards for diesel-powered

equipment, and anticipates that manufacturers and third-party testing

laboratories can immediately begin testing engines under subpart E.

Section 7.82 Definitions. In addition to the existing definitions

in Sec. 7.2, Sec. 7.82 of the final rule sets out and clarifies the key

terms which apply in subpart E. Commenters generally agreed with the

proposed definitions, which were derived from definitions developed for

ISO 8178 and the Society of Automotive Engineers (SAE) Recommended

Practice J177.

No comments were received on the proposed definitions for

``Category A engines'', ``Category B engines'', ``corrosion-resistant

material'', ``diesel engine'', ``exhaust emission'', ``percent load'',

and ``steady-state condition''. These terms and their proposed

definitions are adopted in the final rule.

The definitions of the terms ``rated speed'' and ``intermediate

speed'' in the proposed rule have been modified in the final rule in

response to a commenter who recommended that MSHA's definitions of

these terms conform to definitions contained in internationally

accepted standards. The definitions of these terms in the final rule

are conformed to the definitions in ISO 8178.

The term ``peak torque speed'' in the proposed rule has been

changed to ``maximum torque speed'' in the final rule to conform with

ISO 8178. Both terms convey the same meaning.

One commenter objected to the definition of ``diesel particulate

matter'' as ``any material, with the exception of water, which is

collected on a filter passed by an air diluted exhaust stream.''

According to this commenter the proposed definition was vague and too

dependent on the filter used and method of sampling. The final rule

does not include the proposed definition, adopting instead the

definition for diesel particulates contained in ISO 8178. The ISO

definition is more specific, providing that diesel particulates are

``any material collected on a specified filter media after diluting

diesel exhaust gases with clean filtered air at a temperature less than

or equal to 325 K (52 deg. C) as measured at a point immediately

upstream of the primary filter. This is primarily carbon, condensed

hydrocarbons, and sulphates

[[Page 55419]]

and associated water.'' In addition, the filter and sampling methods,

which are well detailed in ISO 8178, are included in the final rule.

The objective of this definition is to facilitate accurate, repeatable

tests for the diesel particulate matter in an engine's exhaust. Other

definitions may be more appropriate for addressing health effects.

The same commenter also objected to the proposed definition of

``total oxides of nitrogen'' as focusing only on nitric oxide and

nitrogen dioxide. The commenter suggested revisions to these

definitions and offered definitions for several other terms used in the

proposed rule, including ``gaseous ventilation'', ``particulate

index'', ``threshold limit value'', ``permissible exposure limit'' and

``recommended exposure limit.'' According to the commenter, these terms

were not used consistently in the proposal. The final rule does not

adopt these suggested changes. Many of these terms have accepted

meanings that are well known. However, changes throughout the final

rule have been made to be sure the terms are used consistently and

appropriately.

The proposed definition of rated horsepower is revised in the final

rule to conform with current procedures for evaluating engines under

existing part 36. This change will help define an engine's power output

as it is related to performance testing. A definition for the term

``operational range'' is added to also conform with current procedures

for evaluating engines under existing part 36.

Section 7.83 Application requirements. The proposed application

requirements were derived from now-removed part 32 and existing part 36

and are largely unchanged in the final rule. The application procedures

are designed to provide sufficient information to demonstrate

compliance with the technical requirements of subpart E, and form the

basis for approval of diesel engines.

The final rule adopts the proposal to permit applicants to submit

composite drawings in lieu of individual drawings. This approach

reduces paperwork and affords applicants flexibility in the preparation

of their drawings.

The final rule also provides for certain information to be

submitted after approval testing. This information includes the

ventilation rate and particulate index for the engine, and the fuel

deration chart, which provides guidance for how to adjust approved

engines to compensate for altitude.

Like existing part 7 and other MSHA approval standards, the

documentation formulated in the application process forms the basis for

MSHA's approval. Approved diesel engines must be manufactured in

accordance with the specifications contained in the approval and, once

put into service, approved engines must be maintained and operated

within the parameters set in the MSHA approval.

In general, commenters concurred with the proposed application

requirements. One commenter suggested that a description of the design

features which promote efficiency and control over production of toxic

emissions specifically include fuel injection timing. MSHA agrees that

specifications for the fuel injection system of diesel engines and the

fuel injection timing are key in controlling exhaust emissions. The

proposal included a requirement that the fuel injection system be

detailed in approval applications. However, a requirement specifying

the fuel injection timing was not included in the proposed rule.

The final rule adopts the proposed requirement for a description of

the fuel injection system, and adopts in paragraph (b)(6) the

suggestion that fuel injection timing also be specified. This

information had been required in now-removed part 32 and is required

for part 36 engine approvals and to help ensure accurate measurement of

the engine's emissions during the tests and proper maintenance of the

engine's fuel injection timing.

Although the Agency allows electronic record storage in other areas

of this regulation, electronic computer submission of part 7 approval

applications is not yet available. MSHA's Approval and Certification

Center is developing a means for computer submission, and at present

has pilot programs to facilitate the use of electronic reporting.

However, the system is in the formative stage and is not yet available

for public use.

The paperwork hours in the approval application, including test

requirements, are assigned OMB control number 1219-0100.

Section 7.84 Technical requirements. This section of the final rule

sets the specific technical requirements for Category A and Category B

diesel engines. The objective of this aspect of the final rule is to

set standards which, when met, will produce clean-burning diesel

engines that are safe and appropriate for use in the confined

environment of underground coal mines.

Like the proposal, the final rule's requirements for the gaseous

emissions of diesel engines are based on appropriate sections of

existing part 36 approval regulations for diesel engines. Experience

confirms that compliance with these regulations, which address fuel

injection adjustments and fuel-to-air ratios, produces engines that

operate without excessive gaseous emissions that can be harmful to

miners.

One commenter to the proposal suggested that the fuel injection

system on approved diesel engines be required to be fixed and sealed so

that it could not be changed. According to the commenter, sealing the

system would prevent unauthorized changes.

The final rule does not adopt this suggested change, as adjustments

to diesel engine fuel injection systems are necessary for maintenance

and to compensate for altitude. Adjustments such as these permit the

fuel-to-air ratio for diesel engines to be maintained at a level which

minimizes exhaust emissions.

The final rule does, however, adopt the proposed security

requirements to prevent unauthorized fuel injection system adjustments.

Fuel injection system adjustments are required to be changeable only

after breaking a seal, or by altering the injection system's design.

For example, a shim may be added or removed to change the fuel pump's

performance. These parts are supplied by engine manufacturers and must

be used in accordance with the engine's approval. For engines with

electronic fuel injectors, specialized computer interface equipment is

used to adjust the computer programming sequence. The programming

sequence must be installed by the engine manufacturer and is listed

with the engine approval documentation. After adjustments are made in a

fuel injection system, any seal removed must be replaced. Failure to

follow these procedures for adjusting a fuel injection system would

result in the engine no longer being in approved condition. Under

Sec. 75.1914(a) of the final rule, diesel engines used in underground

coal mines are required to be maintained in approved condition.

Consistent with a recommendation of the Diesel Advisory Committee,

the technical requirements for diesel engines also include undiluted

exhaust limits for carbon monoxide and oxides of nitrogen, both of

which have toxic properties which can be harmful to miners. The limits

set for these gases, which are determined when the engine is operated

at its maximum fuel-to-air ratio, are derived from existing

Sec. 36.26(b) and now-removed Sec. 32.4(f). As noted in the proposal,

applying these exhaust gas limits to diesel engines for use in outby

areas is new.

One commenter questioned why the proposal set the same undiluted

exhaust gas limits for Category A and B engines, except that the carbon

monoxide limit

[[Page 55420]]

was 0.30 percent for Category A engines, while the carbon monoxide

limit for Category B engines was set at 0.25 percent. This aspect of

the proposal, which is adopted without change in the final rule,

recognizes a difference in the test procedure between Category A and B

engines. As noted above, Category A engines must be designed to operate

safely in face areas and return air courses where methane may be

present. Thus, Category A engine testing is performed with 1.0 percent

methane injected into the intake air. The methane acts as additional

fuel in the engine, which affects the fuel-to-air ratio. This change in

fuel-to-air ratio increases emission levels, especially carbon monoxide

and oxides of nitrogen. Thus, the final rule technical requirements

permit a slightly elevated carbon monoxide level for Category A engines

during testing so as to avoid imposing an unnecessarily strict test

requirement for this class of diesel engines. The ventilating air

requirement, however, is based on the actual emissions measured during

testing.

The final rule also defines procedures to establish the ventilating

air quantities necessary to maintain the gaseous emissions of diesel

engines within existing required ambient limits. Emissions from both

Category A and Category B engines are diluted to the same ambient

levels when their ventilating air requirements are calculated. Like the

proposal and consistent with the recommendations of the Diesel Advisory

Committee, the final rule addresses this issue by requiring that a

ventilation rate be set for each engine model. Under the final rule,

this ventilation rate must appear on the engine's approval plate. The

ventilation rate, calculated under Sec. 7.88 of the final rule,

indicates the amount of air necessary to dilute carbon dioxide, carbon

monoxide, nitric oxide, and nitrogen dioxide to within allowable

levels. For consistency, the levels specified in the final rule are

those set by existing Sec. 75.322. These exposure standards are based

on the 1972 threshold limit values set by the American Conference of

Governmental Industrial Hygienists (ACGIH) and have applied to

underground coal mines for nearly 25 years. This aspect of the final

rule comports with the recommendation of the Diesel Advisory Committee

that gaseous diesel exhaust components not be treated differently from

contaminants generated by other mining sources. The final rule does not

adopt updated exposure standards at this time because this issue

remains in the rulemaking process for Air Quality standards.

The exposure levels adopted by the final rule for purposes of

calculating the ventilation rate for an engine will lead to lower

required air quantities for ventilating subpart E-approved engines, as

compared to engines approved under now-superseded part 36. This is

because engines previously approved under part 36 were required to

dilute oxides of nitrogen and carbon dioxide to levels lower than

currently specified by the threshold limit values (TLV's) in

Sec. 75.322. The ventilation rates set for engines under the final rule

will be more precisely related to current exposure standards. In

addition, Sec. 75.325(g) of the final rule revises the percentage of

the approval plate air quantity that is required when multiple units of

diesel equipment operate in the same air current. Finally, as discussed

elsewhere, the final rule is designed to produce an integrated system

of controls to protect miners from overexposure to harmful diesel

emissions.

Commenters generally accepted the value and purpose of setting a

ventilation rate for each diesel engine model. Knowledge of the

ventilation rate needed to control gaseous emissions to safe levels

will allow comparison of the efficiency and ventilation demands of

different engine models, and facilitate evaluation of their general

ventilation needs during use. One commenter, however, urged that the

gaseous ventilation rate for control of diesel engine exhaust gases not

be part of the approval process. According to this commenter, existing

ventilation and air quality standards are adequate.

The final rule adopts the requirements for determining the

ventilation rate necessary to dilute diesel engine exhaust

contaminants. Ventilation systems provide different quantities of air

at different locations in the mine. Knowing the ventilating air

quantities needed for diesel-powered equipment will allow the mine

operator to make informed decisions about equipment selection and

utilization and mine ventilation.

Other commenters, who acknowledged the purpose of establishing

ventilation rates for approved diesel engines, recommended for the sake

of clarity that the levels set for the gases be specified in the final

rule. In the proposal, MSHA had set these levels by reference to the

time weighted average (TWA) concentrations for the gases. The final

rule adopts this suggestion and the levels for carbon dioxide, carbon

monoxide, nitric oxide and nitrogen dioxide are specified in the final

rule. The levels in the final rule are identical to the levels in

existing Sec. 75.322, and MSHA intends that the levels in the final

rule conform with any levels that may ultimately be updated.

Specifically, if any of the levels for any of these contaminants are

revised as part of MSHA's Air Quality rulemaking, MSHA intends to

conform the levels in this section to any revised levels.

The proposed requirement for fuel deration received no comments.

The purpose of this requirement, which is adopted without change from

the proposal, is to ensure that the fuel-to-air ratio does not increase

due to the lower density of air at higher altitudes. Not correcting the

maximum fuel delivery on the engine for higher altitude operation

results in increased emission levels. The fuel injection rate

established during the approval may be required to be reduced when the

engine is used at a higher altitude.

Implementing a recommendation of the Diesel Advisory Committee, the

proposed rule also called for a particulate index to be set for

approved diesel engines. The particulate index specifies the quantity

of air needed to dilute the particulate generated by the engine to 1

milligram of diesel particulate matter per cubic meter of air. The

control of particulate matter in diesel engine exhaust was a

significant issue for the Advisory Committee. The Committee concluded

that whole diesel exhaust represents a probable risk for causing human

lung cancer, and recommended that MSHA develop a regulatory scheme to

monitor and control diesel particulate underground. The Committee did

not recommend an exposure level, but did urge that consideration be

given to what level of exposure to diesel particulate presents a health

risk to miners. MSHA is currently developing regulations, separate from

this rule, to address this issue.

The Diesel Advisory Committee also recommended that a particulate

index be set for engines so that the mining industry and MSHA could

compare the particulate levels generated by different engines in terms

of a ventilating air quantity. For example, if the particulate indices

for diesel engines of the same horsepower were established as 7,500

cubic feet of air per minute (cfm) and 12,000 cfm respectively, an

equipment manufacturer, mine operator, and MSHA personnel could use

this information, along with consideration of the type of machine the

engines would power and the area of the mine in which it would be used,

to make certain decisions. For example, a mine operator could use this

information when choosing an engine to roughly estimate an engine's

contribution of diesel particulate to the mine's total respirable

[[Page 55421]]

dust. MSHA would use this information when evaluating mine dust control

plans. Equipment manufacturers can use the particulate index to design

and install exhaust after-treatments.

The final rule retains the proposed requirement for a particulate

index to be set for approved diesel engines. Unlike the ventilation

rate set for each engine, the particulate index value will not appear

on the engine's approval plate. The particulate index, calculated under

Sec. 7.89 of the final rule, indicates what air quantity is necessary

to dilute the diesel particulate in the engine exhaust to 1 milligram

of diesel particulate matter per cubic meter of air. This information

will be available to the mining industry from the engine manufacturer

and MSHA.

Some commenters to the proposal objected to the use of a

particulate index to establish required ventilation air quantities for

diesel engines. These commenters noted that a diesel particulate

permissible exposure level has not yet been set and maintained that

suitable monitoring technology is not available for widespread field

use. These commenters also urged that control of diesel particulate in

underground mines be accomplished through a combination of measures,

including fuel requirements, equipment design, and controls such as

ventilation and equipment maintenance. The commenters recommended that

the particulate index not be part of the engine ventilation rate, and

concluded that such an index should be viewed as a guideline providing

useful information about diesel engines. The commenters further

suggested that additional evaluation be undertaken to determine

appropriate procedures for setting a particulate index.

The overall approach of the final rule is to control diesel

emissions in the underground mine environment through various

established methods, including those suggested by commenters. The

information provided by the particulate index is part of the multi-

level approach recommended by the Diesel Advisory Committee.

As explained above, the particulate index value determined for a

diesel engine is intended to provide useful information about diesel

engines, as the commenters suggested. In addition, the particulate

index value does not appear on the equipment's approval plate and

therefore is not considered in setting the engine's required

ventilation rate.

Section 7.85 Critical characteristics. Critical characteristics,

which are specified for all part 7-approved products, are those

features or specifications which, because of their importance to proper

operation of the equipment, must be inspected or tested on each unit

manufactured. The proposal called for inspecting or testing each diesel

engine to verify that the fuel rate is set to altitude, and the fuel

injection pump adjustment is sealed, if applicable. No comments were

received on this aspect of the proposal, and the final rule adopts the

proposal without substantive change. Instead of requiring the fuel rate

to be set to altitude, the final rule specifies that the fuel rate be

properly set.

As discussed elsewhere in this preamble, the rate of fuel delivery

to a diesel engine significantly affects its gaseous and particulate

emission. As noted earlier, correct adjustment of the fuel injection

pump is essential to the efficient operation of diesel engines.

Inspecting or testing the proposed critical characteristics for

diesel engines approved under part 7, subpart E reasonably ensures that

the performance and emission characteristics of production engines will

be equivalent to those of the engine tested for approval. As a result,

miners are protected against harmful exposure to diesel emissions.

No comments were received on this aspect of the proposal, which is

adopted by the final rule, with the change noted above.

Section 7.86 Test equipment and specifications. This section

adopts the measurement and evaluation methods for emissions from diesel

engines as described in ISO 8178-1. The final rule describes the

apparatus, or test cell, required for testing diesel engine

performance, and sets the specifications for operating this testing

equipment to perform steady-state tests for both gaseous and

particulate emissions.

The major components of a test cell are a dynamometer with engine

operating controls, and gaseous and particulate emission measurement

systems. This test cell is used to perform the test required by

Secs. 7.87, 7.88, and 7.89 of the final rule. Most engine testing

laboratories today have the equipment and meet the specifications

called for by ISO 8178-1 and the final rule.

The final rule's test cell requirements are substantially the same

as the proposed requirements, except that the specifications for the

testing apparatus and test conditions are revised to conform with ISO

8178-1. Commenters to the proposal did not direct attention to these

requirements, but did express concern about correlating the proposed

rule test requirements and Environmental Protection Agency diesel

engine tests, and recommended that the MSHA procedures conform to

internationally accepted test procedures. The adoption of the ISO 8178-

1 provisions eliminates this issue and is responsive to commenters'

concerns.

Like the proposal, the final rule also sets specifications for the

fuel to be used during testing of diesel engines. The proposed rule

would have required No. 2D diesel fuel with certain properties. A

uniform test fuel is important to obtaining repeatable test results and

test data that can be compared. Commenters did not direct their

attention to this aspect of the proposal, except that they generally

encouraged adoption of international standards to the extent possible.

The final rule revises the proposed requirements for diesel engine

test fuel to conform with the fuel requirements in Sec. 75.1901.

Section 75.1901 of the final rule specifies the use of diesel fuel

containing no more than 0.05 percent sulfur. Under this section, diesel

fuel used for engine testing must also be low in sulfur content. In

addition, the properties specified for test fuel conform with the test

fuel EPA requires for testing diesel engines that use low sulfur fuel.

Thus, the final rule will not require testing laboratories to acquire

special fuel to comply with the final rule.

The final rule also adopts the proposal that Category A engines,

which are intended for operation in areas of mines where concentrations

of methane gas could be encountered, be tested with 1.0 percent of

methane added to the engine's intake air. As noted above, this addition

to the ISO 8178 test procedure adopted by the final rule should present

no technical difficulties for manufacturers or third-party

laboratories. MSHA, however, will provide technical assistance for

setting up this aspect of the test procedure upon request.

Metering in 1.0 percent of methane to the intake air of Category A

engines replicates a foreseeable operating condition in underground

mines. In addition, methane gas acts as a fuel when it is aspirated

into a diesel engine, increasing its output of carbon monoxide and

oxides of nitrogen. These emission effects need to be accounted for in

determining the gaseous ventilation rate for Category A engines.

Section 7.87 Test to determine the maximum fuel-to-air ratio. As

noted earlier, the tests prescribed by this section are performed using

the test cell meeting the requirements of Sec. 7.86. Determining the

maximum fuel-to-air ratio for diesel engines is essential to

controlling harmful diesel engine emissions. Too rich a fuel and air

[[Page 55422]]

mixture produces engine exhaust with elevated levels of carbon monoxide

and oxides of nitrogen.

Under this section, engines are required to be operated at several

speed/torque conditions to determine the concentrations of carbon

monoxide and the oxides of nitrogen. Acceptable performance is achieved

when the levels of these exhaust gases do not exceed the limits set by

Sec. 7.84(b) of the final rule throughout the operational range of the

engine.

Commenters did not address the proposed test to determine the

maximum fuel-to-air ratio for diesel engines. The final rule adopts the

proposal without change.

Section 7.88 Test to determine the gaseous ventilation rate. The

test to determine the gaseous ventilation rate for a diesel engine is

required by the final rule to be performed using the test cell required

by Sec. 7.86. This test may be performed together with the test to

determine the particulate index required by Sec. 7.89.

The test required by this section measures the undiluted exhaust

gas concentrations of carbon monoxide, carbon dioxide, nitric oxide,

and nitrogen dioxide in the exhaust. These constituent gases of diesel

engine exhaust are potentially harmful to miners in the confined

environment of underground mines.

In accordance with Sec. 7.86, exhaust gas measurements must be made

at 8 specified points while the engine is operated at each rated speed

and horsepower requested by the approval applicant. For Category A

engines, 1.0 percent methane is added to the engine's intake, as

discussed above.

Like the proposal, the final rule specifies the calculations to be

performed using the results obtained from the test procedure. These

calculations produce a gaseous ventilation rate for the diesel engine.

As discussed above, the ventilation rate indicates the amount of

ventilating air necessary to dilute carbon monoxide, carbon dioxide,

nitric oxide and nitrogen dioxide to within permitted levels. The

ventilation rate for each approved Category A or B diesel engine will

appear on the engine's approval plate. Knowledge of the ventilation

rate needed to control gaseous emissions to safe levels will allow

comparison of the efficiency and ventilation demands of different

engine models, and their general ventilation needs during use can be

evaluated.

As discussed above, commenters generally accepted the value and

purpose of setting a ventilation rate for each diesel engine model. One

commenter urged that the ventilation rate not be part of the approval

process, while others supported the approach taken in the proposed and

final rules. These commenters, however, suggested that the levels for

the exhaust gases be stated in the final rule. The final rule adopts

this suggestion in Sec. 7.84(c).

Section 7.89 Test to determine the particulate index. Like the

other engine tests prescribed by the final rule, the test to determine

the particulate index for an engine is required by the final rule to be

performed using the test cell required by Sec. 7.86. As noted above,

this test may be performed concurrently with the test to determine an

engine's gaseous ventilation rate required by Sec. 7.88.

The test required by this section measures the amount of

particulate in the engine's exhaust when it is operated at eight

specified operating conditions. For Category A engines, 1.0 percent

methane is added to the engine's intake, as discussed above.

The proposed rule would have required that the particulate index be

determined using a different set of test points than those used to

determine the gaseous ventilation rate. The particulate index tests

were based on a cycle of 10 test points. In response to commenters'

suggestions that the particulate and gaseous emissions tests be

conducted using the same test cycle and internationally accepted test

procedures, the final rule adopts the same ISO 8178-4, 8-point test

cycle for both the particulate and gaseous emissions tests.

The Diesel Advisory Committee observed that whole diesel exhaust

represents a probable risk for causing human lung cancer. While

proposing no specific exposure level, the Diesel Advisory Committee

recommended control of diesel particulate in engines used underground

through a combination of measures, including equipment design.

Like the proposal, the final rule does not set a particulate limit

for engines. Instead, the final rule specifies the calculations to be

performed using the results obtained from the test procedures in this

section. From the calculations, a particulate index is derived. As

discussed above, the particulate index for an engine does not appear on

its MSHA approval plate. This information will be available, however,

from MSHA and the engine manufacturer.

Section 7.90 Approval markings. This section requires that each

approved diesel engine be identified with a permanent approval plate

containing certain information. Approval markings to identify equipment

appropriate for use in mining have been used for more than 85 years,

and are routinely relied upon by users of mining equipment as well as

state and federal inspection authorities.

The information required to be displayed on diesel engine approval

plates includes the MSHA-assigned approval number, together with the

engine's model number, ventilation rate, rated power, high idle

setting, and the altitude above which the engine must be derated.

Including these specifications on diesel engine approval plates gives

engine users convenient, immediate access to information important to

proper maintenance and operation of diesel engines.

Commenters directed little attention to this aspect of the

proposal, which is adopted without change in the final rule. Commenters

who objected to setting a ventilation rate for diesel engines as part

of the approval process repeated this concern with respect to the

requirement for the ventilation rate to appear on engine approval

plates. As discussed above, setting a gaseous ventilation rate for

diesel engines comports with the recommendations of the Diesel Advisory

Committee and provides diesel equipment users with information

important to protecting miners. Knowledge of the rate of ventilation

needed to control the gaseous exhaust emissions of a diesel engine

facilitates comparison of the efficiency and ventilation demands of

different engine models.

The other information required by the final rule to appear on an

engine's approval plate likewise provides engine users needed data. The

high idle setting informs maintenance personnel of the engine speed

appropriate for conducting several of the tests to be performed as part

of the engine's permissibility checklist. Together, an engine's

approval number, model number, and its rated power and speed facilitate

use of the manufacturer's maintenance procedures. The maintenance

procedures, along with the altitude above which the engine must be

derated, specify the adjustments which must be made to ensure that an

engine continues to operate in approved condition.

Burden hours required to make and mount MSHA approval plates are

assigned OMB control number 1219-0100.

Section 7.91 Post-approval product audit. This section

incorporates the standard audit requirement for part 7-approved

equipment, specifying that approval holders must make a diesel engine

available for audit by MSHA, at no cost to the Agency. The obligation

to

[[Page 55423]]

supply an engine for audit under this section arises only upon request

by MSHA, and is limited to no more frequently than once a year, except

for cause. Under existing Sec. 7.8(b), the approval holder may observe

any tests conducted under the audit.

Post-approval audits are a critical part of MSHA's quality control

program for approved equipment. By inspecting and testing an engine for

continuing compliance with its approval specifications, potential

problems can be detected and confidence in the approval process is

maintained. Since the inception of post-approval product audits under

part 7, MSHA has detected numerous discrepancies, which have been

effectively corrected.

Commenters directed no attention to this aspect of the proposal,

which is adopted without change from the proposal.

Section 7.92 New technology. This section is designed to

facilitate the introduction of new technology or new applications of

existing technology. It allows MSHA to approve a diesel engine that

incorporates technology for which the requirements of subpart E are not

applicable, provided that MSHA determines the engine is as safe as one

which meets the requirements of subpart E. To make this determination,

MSHA develops appropriate technical requirements and test procedures

when novel designs are submitted for approval. Experience with this

provision under existing regulations has shown that new innovations can

be effectively evaluated and made available for use in a prompt

fashion, thus serving the best interests of miners' safety and health.

Commenters supported this aspect of the proposal, stressing that

research and technological improvements in diesel engines can be

expected. The final rule adopts the proposal without change.

Subpart F Overview

Subpart F of the final rule amends existing part 7, which specifies

testing by the approval applicant or a third party. As an amendment to

the existing regulations, the general administrative provisions of

subpart A of part 7 apply to these new subpart F application

requirements.

Subpart F establishes design and performance requirements for MSHA

approval of ``diesel power packages'' for use in areas of underground

coal mines where permissible electrical equipment is required by

existing safety standards. A ``diesel power package'' is a diesel

engine, together with the attached safety components, such as flame

arresters, spark arresters, surface temperature controls, shut down

systems, and the exhaust cooling system that make a diesel engine

explosion-proof and reduce the engine's surface temperature to a safe

level. Like the proposal, the final rule requirements for diesel power

packages are largely derived from existing MSHA approval regulations in

part 36, which apply to diesel engines for use in gassy underground

mines. The final rule is also consistent with current MSHA practices

for coal mines using diesel-powered equipment and with the

recommendations of the Diesel Advisory Committee. The Advisory

Committee specifically recommended an approval program for diesel power

packages.

Commenters generally accepted the proposal for MSHA approval of

diesel power packages, recognizing the need for diesel-powered

equipment used in underground coal mines to meet critical

specifications and to be properly tested for safe operation in a

potentially explosive atmosphere. Some commenters directed their

attention to the effective date of subpart F, expressing concern about

the availability of commercial testing facilities. For the reasons

discussed below, the final rule does not adopt an extended phase-in

period. However, accommodations are made in the final rule to simplify

the implementation of testing in the private sector, and MSHA will

continue to perform diesel power package testing to subpart F

specifications for up to 3 years, pending the development of private

sector resources.

Other commenters recommended that diesel engine exhaust after-

treatment devices, such as particulate filters or catalytic converters,

be required as part of diesel power packages. These commenters also

suggested that the ventilation rate and particulate index set under

Secs. 7.88 and 7.89 of the final rule credit the use of such devices.

The final rule responds to these comments in part. Under the MSHA

approval program in subpart E, MSHA will evaluate exhaust gas and

particulate controls, provided these devices are integral to the engine

design and are part of normal production engines. The effectiveness of

such controls will also be considered in setting the engine's

ventilation rate and particulate index. This approach will ensure that

the controls are compatible with the engine and are effective. MSHA has

already approved, under existing regulations, engines which incorporate

techniques such as electronic fuel injection systems. Exhaust after-

treatment devices that are not part of an engine's design and

production have been developed which can reduce the particulate matter

in diesel engine exhaust. Also, catalytic converters are available

which can be added to engines to reduce the levels of some harmful

gaseous emissions. MSHA encourages the use of these devices, and under

existing regulations has approved, as safe, several power packages that

utilize catalytic converters and particulate filters. However, under

the final rule MSHA will not evaluate the effectiveness of these

exhaust after-treatment devices. Exhaust after-treatment devices

encompass a wide range of concepts that have demonstrated varying

degrees of effectiveness and reliability. The evaluation of these types

of after-treatment devices is beyond the scope of a part 7 approval

program.

For the same reasons, the final rule does not adopt a commenter's

suggestion that the particulate index for an engine be adjusted to

reflect the use of a diesel particulate filter. Also, the particulate

index for an engine is intended to be used by manufacturers and mine

operators as an aid for, among other things, selecting appropriate

after-treatment devices such as particulate filters. Therefore, under

the final rule the particulate index for an engine will indicate the

particulate contained in the raw engine exhaust.

Other aspects of the final rule will, however, recognize exhaust

after-treatment controls. The positive effects of catalytic converters

in lowering levels of harmful exhaust gases may be considered under

Sec. 75.325(i) for reducing the quantity of ventilating air required

where multiple pieces of diesel-powered equipment are in use. Also,

particulate filters can be effective in maintaining compliance with the

respirable dust standard set by existing Sec. 70.100.

During the course of this rulemaking, the question has been raised

as to whether the final rule should require that some or all diesel

engines be equipped with particulate filters. As noted above, MSHA

encourages the use of such filters and other emission controls.

However, the proposed rule did not raise this issue and MSHA received

only limited comment regarding the appropriate role of diesel

particulate filters. The final rule, therefore, does not require the

use of these filters. However, MSHA is currently developing a proposed

rule to address control of miners' exposure to diesel particulate. This

rulemaking will afford an opportunity to fully develop this issue.

Other commenters suggested that diesel engine cooling system

[[Page 55424]]

components, such as radiators, not be included as part of the approval

of diesel power packages so as to permit changes in cooling system

components to be made in the field without affecting the engine's

approval. The final rule does not adopt this suggestion. The inter-

relationship of the components in the cooling system of a diesel engine

is critically important to controlling power package surface

temperatures, which, when elevated, can lead to a fire. Consequently,

the engine cooling system components must be considered an integral

part of a diesel power package. This aspect of the final rule does not

prohibit field radiator changes, provided that the inter-relationship

of the engine's cooling system components is maintained in approved

condition.

A number of minor changes are made in Secs. 7.97, 7.98, 7.100,

7.101, 7.102, and 7.103 of the final rule to clarify the requirements

of these sections. Substantive changes to these sections are discussed

in the section-by-section discussion which follows.

Section 7.95 Purpose and effective date. The final rule's part 7,

subpart F approval requirements apply to diesel power packages intended

for equipment used in areas of underground coal mines where this

equipment is required to be permissible. The design, performance and

testing requirements of this section are effective November 25, 1996.

MSHA will begin accepting applications under new subpart F immediately.

To accommodate all interests, the Agency also will complete any in-

house part 36 safety component certification applications, or evaluate

such applications under new subpart F, at the applicant's choice. As

noted elsewhere in this preamble, the requirements for approved diesel

power packages in equipment used in underground coal mines become

effective in 3 years.

As noted above, several commenters urged that an extended phase-in

period of several years be included in the final rule. According to the

commenters, a phase-in period is needed to allow for the development of

competent third- party testing facilities, particularly with respect to

explosion-proof testing. Other commenters suggested that subpart F be

made effective immediately, so as to accelerate conformance to the new

requirements for the benefit of miners' safety.

A number of the final rule's test requirements can be performed

effectively with inexpensive, simple test equipment or facilities, or

with the power package installed in the mining equipment. For example,

the static pressure test required by Sec. 7.104 to evaluate the

structural integrity of power package components can be performed using

currently available hand pump devices. Likewise, explosion-proof

testing can be performed in inexpensive test chambers of relatively

simple design.

Nonetheless, MSHA recognizes that some testing capabilities are not

immediately available in the private sector, such as surface

temperature testing and exhaust gas cooling efficiency testing with

methane gas injection in the intake air. To facilitate the approval of

power packages and accommodate the needs of applicants, MSHA may be

consulted for simple alternative procedures which can be used to

provide the same results. In addition, MSHA will perform the tests

required by subpart F for diesel power package approval at its Approval

and Certification Center upon request by applicants. MSHA anticipates

providing these test services, for the fees set in accordance with 30

CFR Part 5, for up to 3 years, or until private sector testing

capability is available. MSHA reserves the right to determine when

competent private sector testing capability is available and to

discontinue MSHA testing.

Section 7.96 Definitions. In addition to the existing definitions

in Secs. 7.2 and 7.82, this section of the final rule sets out and

clarifies the key terms used in subpart F.

Commenters did not direct specific attention to this aspect of the

proposal. The final rule adopts the proposed definitions, with five

exceptions, adds two terms and definitions, and deletes three

definitions from the proposal which now appear in subpart E. These

changes are intended to add flexibility to the final rule and respond

to confusion among some commenters with respect to the substantive

requirements of subpart F.

The definition for ``exhaust conditioner'' has been revised to

remove the words ``corrosion-resistant.'' The requirement for the

exhaust conditioner to be made of corrosion-resistant material is

adopted from the proposal in Sec. 7.98(s)(4)(i). The definitions for

``exhaust system'' and ``intake system'' are revised to include the

phrase ``but is not limited to'', to recognize the use of components

not otherwise mentioned in the definitions for these terms. The term

``explosive mixture'' has been changed to ``flammable mixture'' to

conform with part 36, and the definition for this term has been

modified with the non-substantive change of removing the word

``violently.'' The definition for ``fastening'' has been modified for

the sake of clarity to remove the words ``device such as'' when

referring to bolts, screws, or studs. The term ``high idle speed/no

load'' has been revised to ``high idle speed.'' This is another non-

substantive change, since ``no load'' is specified in the definition of

the term. New definitions for ``dry exhaust conditioner'' and ``wet

exhaust conditioner'' are added to the final rule to more clearly

differentiate between the requirements for these systems. Under the

final rule, a dry exhaust conditioner is defined as a device which

cools exhaust gases without direct contact with water, such as a heat

exchanger. A wet exhaust conditioner is defined as a system which cools

exhaust gases through direct contact with water. Minor changes to the

definitions for ``step (rabbet) joint'' and ``threaded joint'' have

been made for the sake of clarity. The terms ``corrosion-resistant

material,'' ``idle speed/no load,'' and ``rated speed'' and their

definitions are deleted from subpart F. These terms are common to both

subparts E and F, and have already been defined in subpart E. Section

7.96 has been modified to incorporate the definitions of subpart E,

Sec. 7.82.

Section 7.97 Application requirements. This section is derived

from existing part 36 and requires that an application for approval of

a diesel power package contain sufficient information to document

compliance with the technical requirements of the final rule. The list

of information specified for inclusion in the approval application,

which is revised from the proposal in response to commenters and to

fully identify the engine and the fan blade material, is intended to

help applicants supply the data necessary for a prompt evaluation. The

final rule permits applicants to submit composite drawings. This

approach reduces paperwork, affords applicants flexibility in the

preparations of their drawings, and has proven to be effective in other

MSHA approval programs.

Like existing part 7 and other MSHA approval standards, the

documentation formulated in the application process under Sec. 7.97

forms the basis for MSHA's approval of a diesel power package. Approved

diesel power packages must be manufactured in accordance with the

specifications contained in the approval and, once put into service,

approved power packages must be maintained and operated within the

parameters set in the MSHA approval.

The paperwork hours in the approval application, including test

requirements, are assigned OMB control number 1219-0100.

Section 7.98 Technical requirements. This section of the final

rule sets specific technical requirements

[[Page 55425]]

for diesel power packages. Diesel power packages are intended for use

with Category A engines so that they can be operated safely and not

create a fire or explosion hazard. Consistent with the Advisory

Committee's recommendation that permissible diesel equipment be

required in areas of underground coal mines where permissible electric

equipment is required, the final rule's technical specifications

introduce many of the safety features currently required for

permissible electric-powered equipment.

Like the proposal, the final rule is derived largely from existing

technical requirements in part 36 for diesel-powered equipment intended

for use in gassy non-coal mines. The final rule also addresses the

hazard of combustible coal dust by specifying a maximum surface

temperature of 302 deg.F (150 deg.C). This is the same technical

requirement applied to permissible electric-powered equipment. Other

aspects of the final rule set specifications necessary to control

engine surface temperatures, sparking, and the passage of flame from

the exhaust system or components to the external atmosphere. Any of

these conditions could ignite an explosion or fire in the underground

coal mine environment.

Commenters generally accepted the proposed technical requirements,

which, as noted above, are based on long-standing regulations which

have been proven effective and workable. Commenters did, however, raise

several issues.

Some commenters sought wider tolerances for explosion-proof

enclosures in diesel power packages, citing experience in the United

States and Europe. These commenters directed their attention to the

proposed specifications for joints in engine exhaust systems, and

suggested that MSHA review the proposed specification of 0.004 inches

for maximum clearance for joints all in one plane.

The final rule retains this specification, which has proven to be

effective for decades. Commenters offered no basis for the

recommendation for a wider tolerance.

Other commenters suggested that electric starting devices for

diesel engines be prohibited. The proposed rule recognized the

conventional use of hydraulic, pneumatic or other mechanically actuated

starting mechanisms, but also retained the flexibility to evaluate

other means of starting under Sec. 7.107 of the rule concerning new

technology. This aspect of the proposal differs from the existing part

36 regulations from which this proposal was derived.

The final rule is intended to serve as a flexible set of

regulations that will continue to be workable over a period of years.

Throughout the final rule MSHA has adopted the more current practices

and, where appropriate, provides that alternatives may be developed

which are safe and effective. With this in mind, the final rule does

not expressly prohibit the use of electric starting devices for diesel

engines, adopting the proposal to permit MSHA to evaluate other

starting mechanisms. Such alternatives are subject to evaluation under

Sec. 7.107 and must be found by MSHA to be as safe as the pneumatic and

hydraulic starting mechanisms presently in use.

Some commenters asked for clarification of proposed paragraph (i)

with respect to the safety shutdown system required for diesel power

packages. The safety shutdown system is required to automatically shut

off the fuel supply and stop the engine in response to certain

dangerous engine conditions. MSHA intended in the proposal, and the

final rule clarifies, that the shutdown system must respond to both

high exhaust temperature and low water level in the engine's exhaust

conditioner. Either of these conditions can rapidly lead to a fire or

explosion hazard.

In addition, the final rule has been revised from the proposal to

cover other safety system shutdowns that may be installed by the

applicant. Section 75.342 requires methane monitors on some permissible

equipment, and the final rule requires permissible equipment to be

provided with a fire suppression system meeting the requirements of

Sec. 75.1911. Both of these standards specify that the diesel engine

must shut down when either an elevated level of methane is encountered

or when the fire suppression system is actuated. This requirement will

most likely be satisfied by a connection to the safety shutdown system.

The technical requirements of this rule now cover these additional

sensors.

Another commenter suggested that the safety shutdown system include

automatic brake lock-up to prevent diesel-powered equipment from

rolling. This aspect of a machine's safety is evaluated under the

existing requirements of part 36 and is not part of a diesel power-

package approval. Thus, the final rule does not adopt this suggestion.

The final rule adopts clarifying revisions in addition to changes

made in response to commenters. In several instances more precise

language is adopted to differentiate between requirements for wet and

dry exhaust conditioner systems. Proposed Sec. 7.98(d) has been revised

in the final rule to refer to ``nonmetallic rotating parts'' instead of

``fans'', to conform with other MSHA regulations. Paragraph (p)(2)(ix)

has been revised to require that the minimum thread engagement of

fastenings must meet the requirements of the explosion tests in

Sec. 7.104. This is a correction. This change conforms to paragraph

(p)(2)(viii), which requires both tests for acceptance of a minimum

thread engagement of fastenings less than \3/8\ inch. In addition,

paragraph (q)(7) of the final rule does not retain the proposed

requirement that a ``minimum of four fastenings'' be used for

explosion-proof joints. MSHA's experience shows that flange designs

with fewer than four fastenings have proven to be effective. Paragraph

(r)(5) has been revised to note that the opening for connection of a

gage to measure the intake vacuum must be closed by a plug or other

suitable device that is sealed or locked in place except when in use.

This language conforms to the language of part 36, and closing of this

opening is necessary to perform certain tests in this subpart.

Paragraph (s)(1) has been revised to require that the flame arrester

prevent the discharge of glowing particles, conforming it to the

requirement in part 36. Finally, paragraph (s)(5) has been revised to

note that the opening for connection of a gage to measure the

backpressure must be closed by a plug or other suitable device that is

sealed or locked in place except when in use. This language also

conforms to part 36, and is needed to perform some of the tests under

this subpart.

Section 7.99 Critical characteristics. Critical characteristics,

which are specified for all part 7-approved products, are those

features or specifications which, because of their importance to proper

operation of the equipment, must be inspected or tested on each unit

manufactured. The proposal focused on power package features essential

to preventing fires and explosions in the underground coal mine

environment, such as flame-arresting path clearances and the explosion-

proof integrity of the power package. Commenters did not direct their

attention to this aspect of the proposal, which is adopted without

change in the final rule.

Section 7.100 Explosion tests. This section describes the tests to

be performed on diesel power packages to ascertain whether they are

explosion-proof, as specified by the technical

[[Page 55426]]

requirements in Sec. 7.98. Like the proposal, the final rule is derived

from existing Sec. 36.46. Using an explosive mixture of natural gas and

air, or methane and air, the tests prescribed by the final rule

determine the power package's integrity in the event of an explosion

inside the intake or exhaust system. This could be caused by an engine

backfire during starting or ingestion of methane into the engine while

it is running. The prescribed tests determine whether flame arresters

and joints are capable of preventing propagation of the internal

explosion to the surrounding atmosphere. These tests also determine the

lowest water level in the exhaust conditioner that will act effectively

as a flame arrester, and the peak explosion pressures generated in each

segment of the intake and exhaust system. Excessive pressures may be an

indication of a design flaw.

Commenters did not raise issues regarding the proposed explosion

tests. However, the final rule includes one change from the proposal to

better ensure the ability of a diesel power package to withstand an

internal explosion, and another change to revise the speeds at which

dynamic tests are to be conducted. The final rule also includes non-

substantive changes for clarification and to conform the final rule

with existing MSHA regulations.

Paragraphs (a)(2) (v) and (vi) of the final rule specify an

internal peak pressure of 110 psig instead of the proposed 125 psig,

during power package explosion-proof testing. Excessive internal

pressures during explosion-proof testing indicate the potential for

failure of the diesel power package in use, with potentially

catastrophic results in the underground coal mine environment. Lowering

the peak pressure expected during explosion-proof testing recognizes

that diesel power package designs differ and that it is difficult to

select the optimum location for pressure measurements. When pressures

greater than 110 psig are measured during testing, the final rule

specifies redesign of the system to reduce the pressure or more

rigorous testing to verify the integrity of the system. Due to the

critical nature of this test, MSHA has adopted the same approach in its

explosion-proof test requirements for electric motors. The final rule

conforms these like requirements.

Paragraph (a)(2)(vii) of the final rule requires that dynamic tests

be conducted at two speeds--1800200 RPM and

1000200 RPM--instead of at rated speed and 50 percent of

rated speed specified in the proposal. The speeds set by the final rule

correspond to the speeds at which dynamic tests are performed

successfully at MSHA facilities. Also some test facilities may not be

capable of performing tests at the rated speed called for by the

proposal. This change is also reflected in paragraphs (a)(3)(iii) (A)

and (B).

For clarification, the final rule also adopts more precise language

to identify requirements which apply to wet exhaust conditioners,

distinguishing them from dry systems. The final rule also defines

natural gas that may be used in explosion-proof testing in a manner

that better recognizes the variables in the make-up of the hydrocarbons

found in natural gas. As a result, the final rule affords greater

flexibility for manufacturers and testing laboratories.

Section 7.101 Surface temperature tests. This section describes

the tests necessary to ascertain that diesel power packages will not

create a fire hazard in underground coal mines due to coal dust or

other combustible materials contacting hot surfaces. Like the proposal,

the final rule is derived from Sec. 36.48, and sets a maximum external

surface temperature of 302 deg.F (150 deg.C). The test protocol

simulates the operation of a diesel power package under heavy use

conditions. A note has been added to this section to alert the

applicant that this test may be done simultaneously with the exhaust

gas cooling efficiency test described in Sec. 7.102 of the final rule.

Commenters did not direct their attention to this aspect of the

proposal. The final rule is unchanged from the proposal, except for a

non-substantive clarifying change regarding wet exhaust conditioners

and the elimination of the reference to the use of natural gas. A

reference to natural gas, which consists primarily of methane, is

redundant. Instead, the final rule specifies the percentage of methane

to be added to the intake. Elimination of the reference to natural gas

also conforms this section to similar tests, which also determine

engine performance and which only specify methane, in subpart E of part

7.

Section 7.102 Exhaust gas cooling efficiency test. This section

describes the test procedures for measuring the temperature of the

exhaust gas at the discharge point from the exhaust conditioner.

Acceptable performance under this test is exhaust gases that do not

exceed 170 deg.F (76 deg.C) for power packages with a wet exhaust

conditioner, and 302 deg.F (150 deg.C) for a dry system. The proposed

and final rules are derived from existing Sec. 36.47 and address the

hazard of hot exhaust gases creating a fire or explosion hazard.

Commenters raised only one issue concerning this aspect of the

proposal, suggesting clarification of the different performance

requirements for wet and dry exhaust conditioners. The final rule

adopts this suggestion.

Section 7.103 Safety system controls test. This section is derived

from Sec. 36.47 and describes tests to evaluate the performance of the

safety shutdown systems required for diesel power packages. As

discussed above, these systems automatically shut down a diesel engine

in response to potentially dangerous conditions, such as overheating.

The tests prescribed introduce failure modes, such as loss of engine

coolant, and initiate the safety system. Acceptable performance is

achieved when the safety system automatically shuts down the engine

before the technical requirements for approval are exceeded.

Commenters recommended that the final rule more clearly delineate

the different requirements for wet and dry exhaust conditioners. The

final rule adopts this suggestion in paragraphs (a)(3), (a)(4), (b)(2),

and (b)(3).

Commenters also suggested that paragraph (a)(7)(ii) be amended to

include a caveat about the surface temperature of a turbocharger not

exceeding 302 deg. F (150 deg. C). This comment is not adopted because

the final rule addresses surface temperature control under Sec. 7.101

and requires that all external surfaces of power packages, including

turbochargers, not exceed 302 deg.F (150 deg. C). Paragraph (b)(7) has

been revised to accept starting mechanisms constructed of nonsparking

materials in addition to starting mechanisms that prevent the

engagement of the starter while the engine is running. This revision

conforms to Sec. 7.98(j)(1), which permits both options under the final

rule, as it would have under the proposal.

Section 7.104 Internal static pressure test. This section

describes tests to determine if the design of the intake and exhaust

system components of diesel power packages is structurally sound. The

prescribed tests specify internally pressurizing each segment of the

intake and exhaust system. The pressure required to be applied is four

times the maximum pressure observed in the tests performed under

Sec. 7.100, or 150 psig (5 psig), whichever is less.

Acceptable performance is based on an assessment of key points in the

intake and exhaust system, such as joints and welds, for evidence of

leakage or damage.

Commenters raised no issues with respect to the proposal. Paragraph

(b)(2)(vi) has been added to limit

[[Page 55427]]

permanent distortion of any planar surface of the diesel power package

to 0.04-inches/linear foot or less. This change conforms this

requirement to the same requirement applied to the explosion tests in

Sec. 7.100(b)(7).

Section 7.105 Approval markings. This section requires that each

approved diesel power package be identified with a permanent approval

plate inscribed with the MSHA approval number. If the power package

includes a wet exhaust conditioner that functions as an exhaust flame

arrester, the final rule requires that the approval plate also indicate

the grade limitation for the power package. This information is

important so that users are aware of the maximum grade on which the

exhaust conditioner will be effective as a flame arrester.

As noted elsewhere in this preamble, approval markings have been

used for more than 85 years, and are routinely relied upon by users of

mining equipment as well as state and federal authorities to identify

equipment appropriate for use in mining.

Another commenter suggested clarification of the proposal with

respect to the grade limitation for certain diesel power packages. The

final rule has been revised in response to this commenter to clarify

that the grade limitation applies to systems which use a wet exhaust

conditioner as a flame arrester. No grade limitation is appropriate for

power packages with a dry exhaust conditioner.

Burden hours required to make and mount MSHA approval plates are

assigned OMB control number 1219-0100.

Section 7.106 Post-approval product audit. This section

incorporates the standard audit requirement for part 7-approved

equipment, specifying that approval holders must make a diesel power

package available for audit by MSHA, at no cost to the Agency. The

obligation to supply a power package under this section arises only

upon request by MSHA, and is limited to no more frequently than one a

year, except for cause. Under existing Sec. 7.8(b), the approval holder

may observe any tests conducted under the audit.

Post-approval audits are a critical part of MSHA's quality control

program for approved equipment. By inspecting and testing a diesel

power package for continuing compliance with the specifications for its

approval potential problems can be detected and confidence in the

approval process is maintained. Since the inception of post-approval

product audits under part 7, MSHA has detected numerous discrepancies

which have been effectively corrected.

Commenters directed no attention to this aspect of the proposal,

which is adopted without change from the proposal.

Section 7.107 New technology. This section is designed to

facilitate the introduction of new technology or new applications of

existing technology. It allows MSHA to approve a diesel power package

that incorporates technology for which the requirements of subpart F

are not applicable, provided that MSHA determines the power package is

as safe as one which meets the requirements of subpart F. To make this

determination, MSHA develops appropriate technical requirements and

test procedures when applications for the approval of novel designs are

submitted. To provide confidence in the adequacy of the design, such

tests may be required to be performed by MSHA. Experience with this

provision under existing regulations has shown that technological

innovations can be effectively evaluated and made available for use in

a prompt fashion, thus serving the best interests of miners' safety and

health. Commenters generally supported this aspect of the proposal, and

the final rule adopts the proposal without change.

Section 7.108 Power package checklist. This section requires that

approved diesel power packages be accompanied by a description of the

features which must be checked and tests that must be performed to

ascertain that the power package is in approved condition. These

instructions, which are developed as part of the approval process, are

intended to aid power package users in keeping this equipment in safe

operating condition.

Commenters did not direct specific attention to this aspect of the

proposal, which is adopted without change in the final rule.

Part 7, Subparts G, H and I

The final rule does not adopt proposed subpart G to part 7, nor

further develops the advance notice of rulemaking published

concurrently with the proposal concerning subparts H and I to part 7.

Subpart G-approved power packages would have been required for

nonpermissible, heavy-duty diesel-powered equipment used in underground

coal mines. Subpart H would have established regulations for the

approval of fully assembled permissible diesel-powered machines, and

subpart I would have set requirements for the approval of fully

assembled nonpermissible, heavy-duty diesel-powered equipment. In lieu

of this approach, the final rule responds to the commenters who urged

that safety and fire protection features for nonpermissible diesel-

powered equipment be addressed in the Agency's part 75 safety standards

for underground coal mines. Existing part 36 is retained by the final

rule and revised to specifically apply to permissible diesel-powered

equipment for use in underground coal mines. Subpart H is not further

developed by the final rule.

In the proposal, subparts G and I were developed as an approach to

several of the Advisory Committee's concerns. In its deliberations, the

Advisory Committee considered the risk of fire on nonpermissible

diesel-powered equipment caused by hot surfaces igniting combustibles

such as hydraulic and lubricating oils, diesel fuel, and coal dust. To

address this hazard, the Committee recommended limiting engine surface

temperatures. Under the proposal, surface temperature controls and

other machine safety features for heavy-duty nonpermissible diesel

equipment would have been addressed in subparts G and I.

The Committee, however, also recognized the difficulty of applying

such controls to all nonpermissible diesel-powered equipment,

especially light-duty, utility equipment. The Advisory Committee,

therefore, recommended that a ``limited class'' of light-duty equipment

be identified for which less complex fire prevention measures would be

required, such as fire suppression systems which shut down the engine,

guarded drive shafts to prevent damage of fuel and hydraulic lines in

the event of a shaft failure, protection of the fuel tank and lines,

and proper design of the electrical system to prevent electrical arcs.

The proposal included these requirements for a ``limited class'' of

light-duty equipment in the part 75 safety standards for underground

coal mines.

The Advisory Committee also examined what additional features

should be included in the approval requirements for completely

assembled units of diesel-powered equipment. The Committee recommended

that MSHA develop an approval program that would emphasize other

equipment safety features which could be readily addressed by equipment

manufacturers. These features included safeguarding of the fuel system,

an exhaust gas dilution system, a fire suppression system, and

appropriate electrical and braking systems. As a completely assembled

machine, the interrelationship of these systems would be evaluated as

part of the approval process contemplated in the proposal under subpart

H.

A number of commenters objected to the approval of nonpermissible

diesel-

[[Page 55428]]

powered equipment. These commenters maintained that such an expansion

of MSHA's approval process would result in regulating diesel-powered

equipment differently than electric-powered equipment without

justification, and would present severe technical and economic

difficulties in meeting certain proposed requirements. The commenters

recommended that the final rule adhere to the long-standing regulatory

approach for electric-powered equipment, which sets performance-

oriented safety requirements for nonpermissible equipment in the

Agency's part 75 safety standards for underground coal mines. According

to the commenters, this approach would be responsive to the hazards

posed by diesel-powered equipment, and provide sufficient flexibility

to facilitate the introduction of new and safer technology.

In contrast, one commenter urged that all diesel-powered equipment

be approved as permissible, without regard to the equipment's use in

the mine. This commenter pointed out that diesel-powered equipment

presents different hazards than electric equipment, inasmuch as it

contains both a fuel source and an ignition source. The commenter

further maintained that permissible diesel-powered equipment receives

better maintenance than nonpermissible equipment, and explosive

accumulations of methane can be encountered anywhere in an underground

coal mine. This commenter noted that since 1969, 10 explosions occurred

in areas where nonpermissible equipment is permitted, and seven of

these explosions were caused by equipment that was not maintained in

permissible condition.

Another commenter agreed that heavy-duty nonpermissible equipment

should have approved engines and power packages to limit harmful

emissions from the engine and protect against the fire hazard presented

by hot engine surfaces. This commenter, however, objected to MSHA

approval of fully assembled nonpermissible machines as contemplated by

subpart I.

MSHA acknowledges that fire prevention and other machine safety

features can be successfully introduced for nonpermissible equipment,

without a formal approval program. This regulatory approach has been

effectively implemented through MSHA's part 75 safety standards for

underground coal mines as they apply to nonpermissible electric-powered

equipment. For example Sec. 75.518 provides fire protection by

requiring electrical system overload protection for nonpermissible

electric-powered machines. Section 75.523-3 provides a machine safety

feature by requiring automatic emergency parking brakes. Setting such

performance-based requirements for nonpermissible equipment maximizes

the flexibility afforded mine operators and manufacturers to minimize

the hazards of this equipment, and facilitates the introduction of new

technology for dealing with these hazards. For example, new heat

insulating materials have been developed since the publication of the

proposed rule, which can be used to control surface temperatures on

diesel-powered equipment.

To adapt this regulatory approach to nonpermissible diesel-powered

equipment, the final rule extends the proposal's safety requirements

for limited class equipment. Under the final rule, nonpermissible

diesel-powered equipment is not required to be approved by MSHA.

Instead, this equipment must comply with the final rule's safety

requirements in Secs. 75.1909 and 75.1910. These standards include

requirements for fire prevention and machine safety features such as

protection of hydraulic, fuel and electrical systems and adequate

brakes and operator controls.

Part 36

Existing part 36, previously known as schedule 31, has been in

effect since 1961. It sets approval requirements and specifications for

diesel-powered equipment used in ``gassy noncoal mines and tunnels''.

The final rule retains these existing regulations as the basis for

approval of diesel-powered equipment and, in lieu of further developing

subpart H, includes amendments which expand part 36 to apply to

equipment used in underground coal mines. Specifically, part 36 is

amended to afford manufacturers the option of incorporating into their

equipment part 7-approved power packages. Diesel-powered equipment with

approved power packages will be suitable for use in areas of

underground coal mines where permissible equipment is required. The

existing part 36 approval requirements for diesel-powered equipment

used in metal and nonmetal mines are unchanged by the final rule. Part

36-approved equipment with certified engines and safety component

systems will continue to be recognized for use in metal and nonmetal

mines where permissible equipment is required. MSHA will issue approval

numbers that differentiate between equipment for use in coal mines and

equipment for use in metal and nonmetal mines. Machines approved under

revised part 36 specifically for use in underground coal mines will be

identified with an MSHA approval number in a new sequence ``36c-''.

This will indicate that the equipment has been approved for use in

underground coal mines. A part 36 MSHA approval number in the sequence

``31-'' will indicate that the equipment has been approved for use in

metal and nonmetal mines.

These changes are responsive to a number of commenters who urged

that the existing part 36 regulations for the approval of diesel-

powered equipment be retained and continue to apply to equipment for

use in metal and nonmetal mines. In addition, the final rule expands

the scope of part 36, eliminating the need for separate approval

regulations for diesel-powered equipment for use in underground coal

mines as contemplated by subpart H in the proposal.

To retain part 36 and include the approval of diesel-powered

equipment for use in underground coal mines, the final rule re-titles

part 36 and eliminates references to ``gassy noncoal mines and

tunnels'' and related definitions. In addition, the application

requirements of Sec. 36.6 and design requirements of Sec. 36.20 are

revised to recognize the use of part 7-approved power packages, which

substitute for Secs. 36.21 through 36.26 (except Secs. 36.25(f) and

36.43 through 36.48).

The final rule also updates part 36 in several respects. Section

36.20, concerning the quality of material, workmanship and design, is

revised to eliminate an outdated reference to Sec. 18.24 of part 18,

schedule 2F. In its place, the final rule requires compliance with

Sec. 7.98 of the final rule, which provides structural and flame path

requirements for explosion-proof enclosures. This aspect of the final

rule reflects long-standing requirements for explosion-proof

components.

The definition of ``low-volatile hydrocarbon (diesel) fuel'' in

Sec. 36.2(i) is deleted by the final rule. This definition is outdated

and potentially confusing in context with Sec. 75.1901 of the final

rule, which specifies requirements for diesel fuel.

C. 30 CFR Part 70 Discussion

Section 70.1900 Exhaust Gas Monitoring

As outlined in the proposal, the Advisory Committee regarded the

health effects of diesel exhaust as a key area of concern. In its final

report, the Advisory Committee focused on two areas--exposure limits

and a sampling strategy to monitor the concentration of diesel exhaust

in miners' work environment.

[[Page 55429]]

The Committee recommended further research to develop information

about diesel particulate exposure levels at which health effects

accrue. The Committee also addressed gaseous diesel exhaust components,

concluding that suitable protection for miners would be achieved by

relying on coal mine air quality standards, either as they currently

exist or may be revised in the future. The Advisory Committee further

concluded that exposure limits for gaseous contaminants of diesel

exhaust should not be unique from the exposure limits set by the same

contaminants generated by other mining sources, such as blasting. The

Committee specifically recommended a periodic sampling strategy for

carbon monoxide, nitric oxide and nitrogen dioxide and sampling for

sulfur dioxide if diesel fuel containing more than 0.25 percent sulfur

is used. In addition, the Advisory Committee recommended a sampling

strategy which utilized return air course samples to trigger personal

exposure sampling. The Advisory Committee's recommendations served as

the basis for the proposed rule.

The proposed rule did not contain a diesel particulate exposure

standard. At the conclusion of their deliberations the Advisory

Committee recommended that the Secretary of Labor set in motion a

mechanism whereby a diesel particulate standard could be set, and that

the Secretary work in concert with the Bureau of Mines (BOM) and the

National Institute for Occupational Safety and Health (NIOSH) to

develop a sampling strategy and a program for its implementation.

Subsequent to those deliberations, MSHA has been working closely with

the BOM and NIOSH to develop methods for measuring diesel particulate

and for the development of criteria for reducing miners' exposure to

diesel particulate. In 1991, MSHA issued an advance notice of proposed

rulemaking seeking additional information for the development of a

rule. MSHA also held three workshops in 1995 that provided a forum for

mine operators, labor unions, trade organizations, engine

manufacturers, fuel producers, exhaust after-treatment manufacturers,

and academia, to present and discuss information about technologies and

approaches that can be utilized to limit the exposure of miners to

diesel particulate. MSHA is currently using the information obtained

from the advance notice of proposed rulemaking and the workshops to

develop a proposed rule for reducing miners' exposure to diesel

particulate.

The proposal generally followed the Advisory Committee

recommendations for sampling and permissible exposure limits. Under the

proposal, samples of carbon monoxide, nitric oxide and nitrogen dioxide

would be taken weekly in the immediate return airways of each split of

air where diesel equipment is used. When sampling results exceeded 50

percent of any permissible exposure limit set by the proposal, personal

exposure monitoring would have been required. If personal exposure

samples showed concentrations which exceeded 75 percent of the

permissible exposure standard, sampling would continue each operational

shift until, with 95 percent confidence, it was established that

exposure was at or below the permissible level.

Commenters to the proposed rule generally accepted the need for

regular sampling to evaluate miners' working conditions for the

presence of potentially harmful gaseous diesel exhaust components. A

number of commenters, however, noted that the proposed rule was too

focused on sampling, and gave inadequate attention to requiring

corrective action.

Some commenters recommended an alternative to sampling in return

air courses. These commenters suggested a personal sampling approach

keyed to the person in each mechanized mining unit likely to experience

the highest diesel exhaust exposure. This ``designated occupation''

would be identified in the mine's ventilation plan. According to the

commenters, this approach would recognize differences in mine

configuration and mining methods.

Some commenters considered the proposed action level for area

samples, set by the proposal at 50 percent of the permissible exposure

limit values for the gaseous emission components being measured, to be

reasonable. One commenter, in support of the action level concept,

noted that sampling in the immediate return air course would measure

the contribution of all diesel equipment on the mining section, thereby

yielding readings that would give reasonable assurance that miners

working on the section were protected.

Other commenters considered the 50 percent action level possibly

too low for mines with naturally occurring ambient levels of carbon

monoxide near the action level. Some of these commenters also foresaw

possible problems at mines operating near the 50 percent action level.

These commenters were concerned that an unnecessarily burdensome cycle

of area sampling followed by personal sampling could result. Commenters

also noted that the 50 percent action level could be raised because the

permissible exposure limits themselves include a safety factor. No

commenters offered data or specific support for a particular action

level.

Commenters also expressed concern about how effectively the

proposed sampling procedures would address variations in the

concentration of diesel exhaust in miners' workplaces. A number of

commenters suggested different strategies with more frequent samples to

better monitor the presence of the gaseous components of diesel

exhaust. Some commenters suggested special sampling to evaluate peak

exposure when, for example, equipment was operated under load. Other

commenters opposed such an approach, citing difficulties in determining

when peak conditions might occur. Another commenter recommended, in

addition to weekly samples in return air courses, weekly personal

samples of each diesel equipment operator, and at the same time samples

for at least two miners working inby all pieces of diesel equipment on

the same split of air. According to this commenter, the suggested

sampling strategy would yield better information about what diesel

exhaust control measure modifications may be needed. Other commenters

noted the dynamic nature of the underground mining environment, which

varies the concentrations of diesel exhaust in miners' workplaces.

These commenters recommended sampling be performed every shift in

miners' work areas to timely detect the onset of elevated levels of

diesel exhaust contaminants.

A number of commenters also noted that, in addition to sampling in

the immediate return air course, attention should be given to the area

of the section loading point. According to these commenters, diesel

exhaust contaminants are often elevated at this location due to high

engine loads at a single stationary point. Commenters also noted the

need to address situations when diesels are used in locations outby the

working faces. According to these commenters, construction projects can

involve significant diesel usage at some mines.

The proposed rule did not specify sampling methods for evaluating

the gaseous components of diesel exhaust. In the preamble discussion to

the proposal, however, MSHA made reference to electrochemical analyzers

and detector tubes as technology that could be used to determine

concentrations of the gases to be measured. Commenters did not suggest

specific sampling methods or object to those mentioned in the preamble

discussion. Some commenters, however, emphasized that the methods

chosen should not be highly technical in

[[Page 55430]]

nature. Several commenters urged that the task of sampling be something

miners generally could perform with proper training.

As discussed elsewhere in this preamble, the final rule as a whole

is designed to lay a foundation for the safe and healthful operation of

diesel equipment in the confined, potentially explosive underground

coal mine environment. To accomplish this objective, the final rule

sets standards for diesel engines, suitable for mining. For the

operation of this equipment, the final rule sets practicable standards

for the use of low sulfur fuel and for adequate ventilation and proper

maintenance of diesel equipment. These standards are intended to work

together as an operating system to create a more healthful and safe

working environment for miners.

Paragraph (a) of the final rule adopts a streamlined sampling

strategy that is keyed to this operating system approach. The

requirements of proposed Sec. 70.1900 have been revised in the final

rule to integrate sampling for gaseous components of diesel exhaust

with existing on-shift workplace examination requirements and to take

advantage of modern sampling instrumentation. The final rule also

incorporates by reference the threshold limit values (TLV's)

adopted by the American Conference of Governmental Industrial

Hygienists (ACGIH). These TLV's are also incorporated by

reference in MSHA's existing standards for exposure limits in

Sec. 75.322. The final rule retains the proposed action level concept

with some modifications responsive to commenters. However, the final

rule does not adopt the proposed requirement that area samples over the

action level trigger personal sampling. Instead, paragraph (c) of the

final rule requires corrective action to be taken immediately to reduce

gaseous diesel exhaust concentrations to or below the action level. The

final rule's sampling requirements are intended to provide a regular

and timely check on how the total operating system of diesel exhaust

control is working, with an emphasis on prompt corrective action.

Although the final rule does not require personal sampling,

existing standards regulate miners' exposure to harmful airborne

contaminants. These standards do not permit miner exposures over the

established TLV's incorporated in this section of the final

rule and in Sec. 75.322. MSHA enforces these standards during mine

inspections through personal and other sampling methods.

Like the proposal, paragraph (a) of the final rule specifies area

samples in the ventilation return airways of each working section where

diesel equipment is used, at a location which represents the

contribution of all diesel equipment on the section. This approach was

recommended by the Advisory Committee, and generally was supported by

the commenters. In response to commenters, the final rule also requires

samples in the area of the section loading point if diesel haulage

equipment is operated on the working section, and at the point inby the

last unit of diesel equipment on the longwall or shortwall face where

mining equipment is being installed or removed. Depending on the mining

system used, these are strategic locations in which to take area

samples to evaluate the overall effectiveness of the control measures

for diesel exhaust.

In addition, the final rule authorizes the MSHA district manager to

specify area samples at other strategic locations on a mine-by-mine

basis in order to accommodate circumstances which can result in

significant concentrations of diesel exhaust. This aspect of the final

rule responds to commenters' concerns about situations which can

involve significant diesel usage in areas outby the working face, such

as construction projects. The paperwork aspect of this provision

results in a minimally increased burden since existing Sec. 75.370 of

this chapter requires that all underground coal mines have ventilation

plans. Although this provision of the final rule is new, proposed

Sec. 75.390(b) would have required that the mine operator include

certain minimum ventilation quantities in the mine's ventilation plan.

Under the proposal, these minimum air quantities would have been

related to the number of diesel-powered units operating and the air

quantity necessary to control gaseous diesel emissions. Thus, this

final rule provision is consistent with proposed Sec. 75.390(b).

Monitoring of gaseous diesel exhaust components during the on-shift

examination required by existing Sec. 75.362 of this chapter makes

checks for diesel exhaust concentrations part of the workplace

examinations which have been historically conducted in the coal mining

industry. On-shift examinations are designed to detect hazards which

can develop during a working shift when normal mining operations are

underway. Such examinations include tests for methane gas accumulations

and oxygen deficiency, and determinations of air direction and

velocity. Tests for diesel exhaust gases can be readily made during the

on-shift examination by the same mine personnel. Currently, multi-gas

detectors are available and in use in a significant number of mines in

the industry which can sample simultaneously and directly read out

results for methane, oxygen, carbon monoxide and nitrogen dioxide.

Making checks of the mine's diesel exhaust control system part of the

existing practice of on-shift examinations minimizes the burden of

compliance with the final rule's sampling requirements. Under the final

rule, special staff and a separate diesel exhaust sampling schedule

should be unnecessary.

Sampling as part of the on-shift examination also increases the

frequency of diesel exhaust concentration monitoring from the proposed

weekly schedule, and responds to commenters who questioned the adequacy

of the proposal in this regard. The final rule's increased frequency of

sampling affords more timely and meaningful information about the

performance of the mine's overall diesel exhaust control system. Diesel

equipment is highly mobile and the mining environment changes rapidly

as mine development progresses. Monitoring each shift alerts the mine

operator to emerging problems with the control of diesel exhaust,

before miners are overexposed to harmful contaminants.

Consistent with existing Sec. 75.362 of this chapter, the final

rule also requires sampling to be performed by a certified person

designated by the operator. This aspect of the final rule is generally

consistent with the proposal as it requires that competent persons

perform the sampling, the results of which form the basis for important

decisions about miners' work environments.

Under the final rule, sampling would be required for two gaseous

components of diesel exhaust: carbon monoxide and nitrogen dioxide. The

final rule does not retain the proposal for sampling sulfur dioxide

when diesel fuel containing more than 0.25 percent sulfur is used.

Section 75.1901 of the final rule requires the use of low-sulfur fuel

at all times, rendering this aspect of the proposed rule unnecessary.

The final rule also deletes the proposed requirement for sampling

nitric oxide.

Both carbon monoxide and nitric oxide are produced in significant

quantities when diesel engines operate under load. Elevated carbon

monoxide is also indicative of engine faults such as misadjusted fuel

systems, failure to derate engines for altitude, or dirty air cleaners.

Conditions of use such as prolonged diesel engine idling can also

produce elevated levels of carbon monoxide. Catalytic converters,

designed to remove carbon monoxide

[[Page 55431]]

from the exhaust, work poorly under these conditions due to lower

equipment operating temperatures.

Nitric oxide concentrations generally do not reflect engine faults.

In addition, nitric oxide is readily converted to nitrogen dioxide in

the mine atmosphere, making representative measurement difficult under

the final rule's area sampling strategy. Also, in MSHA's experience the

TLV for carbon monoxide will be exceeded before the

TLV for nitric oxide. Sampling for nitric oxide, therefore,

is not retained in the final rule.

The final rule also requires sampling for nitrogen dioxide.

Nitrogen dioxide is readily detectable and potentially harmful to

miners. The TLV for nitrogen dioxide is 5 parts-per-million

(ceiling), which cannot be exceeded at any time. Therefore, the final

rule adopts the proposed requirement to sample for nitrogen dioxide.

The final rule addresses the collection of carbon monoxide and

nitrogen dioxide samples with performance-based requirements. In

response to commenters, the task of sampling is significantly

simplified. The sampling requirements also emphasize prompt

availability of sample results, consistent with the final rule's

emphasis on corrective action to protect miners from the risk of

overexposure.

Paragraph (b)(1) provides that monitoring of carbon monoxide and

nitrogen dioxide is to be performed in a manner which makes the results

available immediately to the person collecting the samples. This aspect

of the final rule recognizes that direct-readout sampling instruments

are now available that can measure carbon monoxide and nitrogen

dioxide. Use of these hand-held instruments requires no specialized

technical background so that persons may be easily trained to perform

this task. Mine-wide monitoring systems, with properly located sensors,

could also be employed to collect the required carbon monoxide and

nitrogen dioxide samples.

Paragraph (b)(2) of the final rule generally adopts the proposal,

and specifies that samples are to be collected by appropriate

instrumentation that has been maintained and calibrated in accordance

with the manufacturer's recommendations. These provisions establish

sound practices necessary for accurate sample results, while retaining

the flexibility for new instrumentation that may be developed in the

future.

Paragraph (b)(3) requires that samples be collected during periods

that are representative of conditions during normal operations. This

aspect of the final rule is consistent with the proposal and serves the

underlying purpose of the sampling requirements, which is to gauge the

performance of the diesel exhaust control system under normal operating

conditions. Like the proposal, the final rule does not prescribe

special requirements to measure the performance of the diesel exhaust

control system under peak load conditions. As some commenters noted,

determining when peak load conditions occur would be difficult to

predict. In addition, such an approach would increase the complexity of

the final rule unnecessarily.

Regular sampling during on-shift examinations will afford a

realistic picture of the performance of the diesel operating system. To

meet the requirement that samples be taken during periods that are

``representative of conditions during normal operations,'' MSHA intends

that tests for carbon monoxide and nitrogen dioxide be made when

diesel-powered equipment is being used as it typically is in the mining

process. Thus, for example, sampling is appropriate when diesel haulage

equipment is moving coal or diesel-powered roof bolters are installing

bolts.

Some commenters noted the need to monitor exhaust concentrations

during longwall moves with diesel-powered equipment, expressing concern

that moving the component parts of a longwall to a new block of coal

for mining can involve heavy usage of diesel equipment over the course

of multiple shifts. As a result, miners could be exposed to elevated

levels of diesel exhaust gases. The final rule addresses these comments

through the increased frequency of samples to monitor diesel exhaust

gases. On-shift examinations are required under Sec. 75.362 of this

chapter when longwall moves are being performed and, under the final

rule, tests of the concentrations of carbon monoxide and nitrogen

dioxide are required at the point immediately inby the last piece of

diesel equipment on the longwall or shortwall face. If these samples

indicate carbon monoxide and/or nitrogen dioxide concentrations greater

than the action level, immediate corrective action is required. This

approach protects miners through early detection of elevated

concentrations of diesel exhaust gases, and prompt adjustments to the

mine's diesel exhaust controls.

Paragraph (c) of the final rule is modeled after other MSHA

standards for potentially hazardous gases, such as methane, and

requires immediate corrective action when sample results indicate gas

concentrations exceeding the action level. This change in the proposal

is responsive to commenters who pointed out that the proposal gave

inadequate attention to corrective action. The final rule retains the

proposed action level concept tied to the TLV's for carbon

monoxide and nitrogen dioxide. The exposure limits incorporated are

those already incorporated in existing Sec. 75.322 of this chapter.

These exposure standards are based on the 1972 threshold limit values

set by the American Conference of Governmental Industrial Hygienists

(ACGIH) and have applied to underground coal mines for nearly 25 years.

This aspect of the final rule comports with the recommendation of the

Advisory Committee that gaseous diesel exhaust components not be

treated differently from contaminants generated by other mining

sources. The final rule does not adopt updated permissible exposure

standards at this time, as referenced in the proposal, because this

issue remains in the rulemaking process for Air Quality standards.

Under paragraph (c) of the final rule, the action level is set at

50 percent of the TLV's for carbon monoxide and/or nitrogen

dioxide for samples collected in the areas identified in paragraph (a).

As noted in the proposed rule, an action level is used to minimize the

risk that workers will be overexposed. An action level is not a

compliance limit for miners' exposure. Instead, an action level is

intended to provide a timely trigger for reviewing the mine's diesel

exhaust control system. Exceeding an action level under the final rule

is not, by itself, a violation.

The 50 percent action level concept is well-recognized in

industrial hygiene practice as an effective, practical screening tool

for minimizing the risk of workers' overexposure. This approach, based

largely on statistical considerations, was developed by the National

Institute for Occupational Safety and Health (NIOSH) for regulations

promulgated by the Occupational Safety and Health Administration

(OSHA), ``Leidel et al., NIOSH Publication No. 77-173.''. It is

designed to afford a single value trigger for simplicity of application

and to reduce exposure monitoring burdens. ``Patty's Industrial Hygiene

and Toxicology, 1994, p. 528.'' Based on the work of Nelson A. Leidel

and others, the 50 percent action level is considered a reliable

indicator that there is a low probability of worker exposures which

exceed the TLV linked to the action level.

The action level of 50 percent of the TLV's for carbon

monoxide and nitrogen dioxide is well-suited to the

[[Page 55432]]

purposes of this final rule, and will afford miners protection from

overexposure to potentially harmful diesel exhaust emissions. Samples

collected in accordance with paragraph (a) of this section will yield

results showing the concentration of diesel exhaust emissions in key

places under representative conditions on a regular basis. Applying the

50 percent action level to these routine sample results will account

for sources of variability affecting miners' exposure, such as the

diesel activity level, ventilation rates, and duty cycles. The action

level also provides a simple means of evaluating the status of the

mine's overall diesel exhaust control system. As discussed elsewhere,

this operating system approach to the control of diesel exhaust

emissions is a key underpinning of the final rule.

The final rule also permits adjustments to the 50 percent action

level on a mine-by-mine basis. Under Sec. 75.325(j) of the final rule

the MSHA district manager may approve an alternative action level in

the mine's ventilation plan. Ventilation plans are required for all

underground coal mines by existing standards under Sec. 75.370 of this

chapter. Under the final rule, any change in the 50 percent action

level must be based on the results of sampling which demonstrate that

miners' personal exposure will not exceed the applicable TLV.

Thus, a mine operator may show that a 60 percent action level, for

example, is appropriate for the miners working on a section. To do

this, the operator must demonstrate through sampling that miners

working on the section are not overexposed to diesel exhaust gases when

samples in the immediate return air course show that concentrations of

carbon monoxide and/or nitrogen dioxide are maintained at 60 percent of

the TLV. Based on this data, the 50 percent action level

could be revised, with the approval of the district manager. The higher

action level would be made part of the mine's approved ventilation plan

and, thereby, become a compliance requirement at the mine. If, with

experience, the revised action level was shown to be inappropriate,

changes would be made through the mine ventilation plan approval

process. Mine ventilation plans are required by existing standards to

be reviewed at least every six months.

The sampling necessary to demonstrate that the personal exposure of

miners would not exceed the TLV is not specified by the final

rule, recognizing that many approaches can be taken. For approval to

revise an action level, however, MSHA will require clear evidence that

a proposed change in an action level is appropriate. As discussed

above, the purpose of an action level is to trigger a review of the

mine's diesel exhaust control system before miners are overexposed to

harmful gases. As the action level is raised closer to the

TLV, the reliability of the action level as a timely warning

diminishes. Thus, MSHA does not anticipate approval of action levels

that provide a nominal margin of protection.

The final rule does not specify what corrective action is required

when an action level for carbon monoxide and/or nitrogen dioxide is

exceeded. Instead, this determination is to be made by the mine

operator, who is in the best position to implement changes appropriate

to the situation and sufficient to promptly return carbon monoxide and/

or nitrogen dioxide concentrations to or below the applicable action

level. Corrective action may involve addressing ventilation

deficiencies, controlling the number of diesel machines operating in an

area, or correcting engine faults. Elevated levels of carbon monoxide

and/or nitrogen dioxide may indicate that appropriate corrective action

is revision of the mine's ventilation plan. Modifying the mine's

ventilation plan integrates needed controls into the operating system

for the mine.

The final rule does not retain the proposed requirement to conduct

personal sampling when the action level for gaseous diesel exhaust

components is exceeded. Proposed Sec. 70.1901 therefore is not included

in the final rule. While the Advisory Committee recommended a two-

tiered approach of area sampling which could trigger personal sampling,

MSHA believes that the final rule's sampling strategy will better

protect miners. As discussed above, the sampling strategy adopted

focuses on the performance of the mine's control system for diesel

exhaust, rather than measurements of individuals' exposure levels. This

approach safeguards miners from overexposure by frequent testing for

gaseous diesel exhaust components in key areas, and establishing action

levels for initiating corrective action that responds to emerging

problems. In addition, MSHA mine inspections will include regular

checks on miners' exposure to harmful airborne contaminants, including

carbon monoxide and nitrogen dioxide, as part of determining compliance

with the TLV's in Sec. 75.322 of this chapter. MSHA's current

practice is to sample, at least annually, all diesel equipment

occupations on each mechanized mining unit. It is MSHA policy to also

sample half of the diesel equipment occupations in areas outby the

face. As a result, MSHA is confident that miners will be adequately

protected.

The final rule changes also respond to commenters who objected to

the proposed personal monitoring requirements as fostering excessive

sampling. In its guidance comments, the Office of Management and Budget

counseled that the criteria for personal monitoring had the potential

for an unnecessarily burdensome paperwork loop in which a mine would be

required to conduct area sampling one week and personal sampling the

next week. Other commenters also foresaw the potential for a cycle of

area sampling followed by personal sampling, particularly at mines with

naturally occurring high levels of carbon monoxide. These commenters

also objected to the proposal that when personal exposure monitoring

results indicate levels greater than 75 percent of the permissible

exposure limit, such sampling would be required to continue on each

operational shift until compliance was established with 95 percent

confidence. By focusing the final rule's sampling requirements on

monitoring the performance of the mine's diesel exhaust control system

and taking timely corrective action, this potential problem is

eliminated.

The proposed rule recordkeeping requirements were tied to MSHA's

proposed Air Quality standards in Secs. 72.200 (d), (e), (f) and (g) of

this chapter. Commenters objected to the proposal's reference to MSHA's

proposed Air Quality standards concerning exposure monitoring and

referenced the comments they had submitted on those proposed rules.

Under the proposal, the results of miners' personal samples were to be

maintained for 5 years and include personal identification information

as well as data about sampling location, duration, and results. The

proposed requirements also required a record of the corrective action

taken if miners' exposure readings exceeded the permissible limit. In

addition, the proposed rule set requirements for access to miners'

personal exposure records, provided miners or their representatives

with the opportunity to observe monitoring, and called for notification

of miners when samples indicate they have had exposures exceeding the

permissible limit.

In the Air Quality rulemaking, commenters objected to MSHA's

proposal that adjustments to calculations of exposure be made for novel

workshifts when a miner worked longer than eight hours. Commenters also

objected to mine operators having to take corrective action to reduce

[[Page 55433]]

exposures based on one sample showing overexposure. In addition,

commenters objected that it was burdensome to include the mine

operator's corrective action in exposure monitoring records. Other

commenters supported this requirement. These commenters further stated

that the period for record retention should be 30 years for

epidemiological purposes and to be consistent with the Occupational

Safety and Health Administration's general industry requirements.

For the reasons discussed above, the final rule re-focuses sampling

for the gaseous components of diesel exhaust on early detection of

diminishing performance of the mine's diesel exhaust control system. As

a result, personal samples are not required. Certain limited

recordkeeping is, however, necessary to support the final rule's

objective of tracking the performance of the mine's diesel exhaust

control system. To accomplish this objective with the least

recordkeeping burden, paragraph (d) of the final rule revises the

recordkeeping requirements of the proposal, conforming them to the

existing requirements for on-shift examinations. Under the final rule,

a record is required to be made of the results of samples taken under

this section which exceed the applicable action level for carbon

monoxide and/or nitrogen dioxide. Like the proposal, the data to be

recorded under the final rule include the location where the sample was

taken; the concentration of carbon monoxide and/or nitrogen dioxide

measured; and the corrective action taken to reduce the concentration

of carbon monoxide and/or nitrogen dioxide to below the applicable

action level. A record of the instrumentation used, which would have

been required under the proposal, has not been adopted in the final

rule, because this is not essential information under the sampling

scheme of the final rule.

This aspect of the final rule is intended to minimize recordkeeping

by requiring a record only when sample results are over the appropriate

action level. This information is key to an effective monitoring system

and provides essential data for assessing how the mine's diesel exhaust

control system is functioning.

For ease of administration by mine operators, the final rule

specifies that recordkeeping under paragraph (d) follow the same

requirements contained in existing Sec. 75.363 of this chapter. These

standards prescribe the recordkeeping requirements for hazardous

conditions found during a shift, including on-shift examinations.

Section 75.363 of this chapter requires that the record be kept in a

book maintained for the purpose on the surface of the mine, and that

the record be completed by the end of the shift. Section 75.363

requires that the record be made by the certified person who conducted

the examination, or a person designated by the operator. In the latter

case, the certified person must verify the record by the end of the

shift. Records made under Sec. 75.363 also must be countersigned by the

mine foreman or equivalent mine official by the end of the mine

foreman's or equivalent mine official's next regularly scheduled

working shift. These features of Sec. 75.363 emphasize the importance

of mine management using and responding to data about working

conditi

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