Underground Construction (29 CFR 1926.800)

Clipped end connections are connection
material on the end of a structural member
which has a notch at the bottom and/or top
to allow the bolt(s) of the first member
placed on the opposite side of the central

member to remain in place. The notch(es)
fits around the nut or bolt head of the opposing member to allow the second member to
be bolted up without removing the bolt(s)
holding the first member.

Staggered connections are connection material on a structural member in which all of
the bolt holes in the common member web
are not shared by the two incoming members
in the final connection. The extra hole in the
column web allows the erector to maintain
at least a one bolt connection at all times
while making the double connection.

Subpart S—Underground Construction,
Caissons,
Cofferdams and Compressed
Air
AUTHORITY: Sec. 107, Contract Work Hours
and Safety Standards Act (40 U.S.C. 333);
secs. 4, 6, and 8 of the Occupational Safety
and Health Act of 1970 (29 U.S.C. 653, 655, 657);

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ER18JA01.025

29 CFR Ch. XVII (7–1–07 Edition)

ER18JA01.024

Pt. 1926, Subpt. R, App. H

Occupational Safety and Health Admin., Labor
Secretary of Labor’s Orders 12–71 (36 FR
8754), 8–76 (41 FR 25059), 9–83 (48 FR 35736), 1–
90 (55 FR 9033), or 6–96 (62 FR 111), as applicable.

§ 1926.800 Underground construction.
(a) Scope and application. (1) This section applies to the construction of underground tunnels, shafts, chambers,
and passageways. This section also applies to cut-and-cover excavations
which are both physically connected to
ongoing underground construction operations within the scope of this section, and covered in such a manner as
to create conditions characteristic of
underground construction.
(2) This section does not apply to the
following:
(i) Excavation and trenching operations covered by subpart P of this
part, such as foundation operations for
above-ground structures that are not
physically connected to underground
construction operations, and surface
excavation; nor
(ii) Underground electrical transmission and distribution lines, as addressed in subpart V of this part.
(b) Access and egress. (1) The employer
shall provide and maintain safe means
of access and egress to all work stations.
(2) The employer shall provide access
and egress in such a manner that employees are protected from being
struck by excavators, haulage machines, trains and other mobile equipment.
(3) The employer shall control access
to all openings to prevent unauthorized
entry underground. Unused chutes,
manways, or other openings shall be
tightly covered, bulkheaded, or fenced
off, and shall be posted with warning
signs indicating ‘‘Keep Out’’ or similar
language. Completed or unused sections of the underground facility shall
be barricaded.
(c) Check-in/check-out. The employer
shall maintain a check-in/check-out
procedure that will ensure that aboveground personnel can determine an accurate count of the number of persons
underground in the event of an emergency. However, this procedure is not
required when the construction of underground
facilities
designed
for
human occupancy has been sufficiently
completed so that the permanent envi-

§ 1926.800

ronmental controls are effective, and
when the remaining construction activity will not cause any environmental hazard or structural failure
within the facilities.
(d) Safety instruction. All employees
shall be instructed in the recognition
and avoidance of hazards associated
with underground construction activities including, where appropriate, the
following subjects:
(1) Air monitoring;
(2) Ventilation;
(3) Illumination;
(4) Communications;
(5) Flood control;
(6) Mechanical equipment;
(7) Personal protective equipment;
(8) Explosives;
(9) Fire prevention and protection;
and
(10) Emergency procedures, including
evacuation plans and check-in/checkout systems.
(e) Notification. (1) Oncoming shifts
shall be informed of any hazardous occurrences or conditions that have affected or might affect employee safety,
including liberation of gas, equipment
failures, earth or rock slides, cave-ins,
floodings, fires or explosions.
(2) The employer shall establish and
maintain direct communications for
coordination of activities with other
employers whose operations at the jobsite affect or may affect the safety of
employees underground.
(f) Communications. (1) When natural
unassisted voice communication is ineffective, a power-assisted means of
voice communication shall be used to
provide communication between the
work face, the bottom of the shaft, and
the surface.
(2) Two effective means of communication, at least one of which shall be
voice communication, shall be provided
in all shafts which are being developed
or used either for personnel access or
for hoisting. Additional requirements
for hoist operator communication are
contained in paragraph (t)(3)(xiv) of
this section.
(3) Powered communication systems
shall operate on an independent power
supply, and shall be installed so that
the use of or disruption of any one

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§ 1926.800

29 CFR Ch. XVII (7–1–07 Edition)

phone or signal location will not disrupt the operation of the system from
any other location.
(4) Communication systems shall be
tested upon initial entry of each shift
to the underground, and as often as
necessary at later times, to ensure that
they are in working order.
(5) Any employee working alone underground in a hazardous location, who
is both out of the range of natural unassisted voice communication and not
under observation by other persons,
shall be provided with an effective
means of obtaining assistance in an
emergency.
(g) Emergency provisions—(1) Hoisting
capability. When a shaft is used as a
means of egress, the employer shall
make advance arrangements for powerassisted hoisting capability to be readily available in an emergency, unless
the regular hoisting means can continue to function in the event of an
electrical power failure at the jobsite.
Such hoisting means shall be designed
so that the load hoist drum is powered
in both directions of rotation and so
that the brake is automatically applied
upon power release or failure.
(2) Self-rescuers. The employer must
provide self-rescuers approved by the
National Institute for Occupational
Safety and Health under 42 CFR part
84. The respirators must be immediately available to all employees at
work stations in underground areas
where employees might be trapped by
smoke or gas. The selection, issuance,
use, and care of respirators must be in
accordance with 29 CFR 1926.103.
(3) Designated person. At least one
designated person shall be on duty
above ground whenever any employee
is working underground. This designated person shall be responsible for
securing immediate aid and keeping an
accurate count of employees underground in case of emergency. The designated person must not be so busy
with other responsibilities that the
counting function is encumbered.
(4) Emergency lighting. Each employee
underground shall have an acceptable
portable hand lamp or cap lamp in his
or her work area for emergency use,
unless natural light or an emergency
lighting system provides adequate illumination for escape.

(5) Rescue teams. (i) On jobsites where
25 or more employees work underground at one time, the employer shall
provide (or make arrangements in advance with locally available rescue
services to provide) at least two 5-person rescue teams, one on the jobsite or
within one-half hour travel time from
the entry point, and the other within 2
hours travel time.
(ii) On jobsites where less than 25 employees work underground at one time,
the employer shall provide (or make
arrangements in advance with locally
available rescue services to provide) at
least one 5-person rescue team to be either on the jobsite or within one-half
hour travel time from the entry point.
(iii) Rescue team members shall be
qualified in rescue procedures, the use
and limitations of breathing apparatus,
and the use of firefighting equipment.
Qualifications shall be reviewed not
less than annually.
(iv) On jobsites where flammable or
noxious gases are encountered or anticipated in hazardous quantities, rescue team members shall practice donning and using self-contained breathing
apparatus monthly.
(v) The employer shall ensure that
rescue teams are familiar with conditions at the jobsite.
(h) Hazardous classifications—(1) Potentially gassy operations. Underground
construction operations shall be classified as potentially gassy if either:
(i) Air monitoring discloses 10 percent or more of the lower explosive
limit for methane or other flammable
gases measured at 12 inches (304.8 mm)
±0.25 inch (6.35 mm) from the roof, face,
floor or walls in any underground work
area for more than a 24-hour period; or
(ii) The history of the geographical
area or geological formation indicates
that 10 percent or more of the lower explosive limit for methane or other
flammable gases is likely to be encountered in such underground operations.
(2) Gassy operations. Underground
construction operations shall be classified as gassy if:
(i) Air monitoring discloses 10 percent or more of the lower explosive
limit for methane or other flammable
gases measured at 12 inches (304.8 mm)
±0.25 inch (6.35 mm) from the roof, face,

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Occupational Safety and Health Admin., Labor
floor or walls in any underground work
area for three consecutive days; or
(ii) There has been an ignition of
methane or of other flammable gases
emanating from the strata that indicates the presence of such gases; or
(iii) The underground construction
operation is both connected to an underground work area which is currently classified as gassy and is also
subject to a continuous course of air
containing the flammable gas concentration.
(3) Declassification to potentially gassy
operations. Underground construction
gassy operations may be declassified to
Potentially Gassy when air monitoring
results remain under 10 percent of the
lower explosive limit for methane or
other flammable gases for three consecutive days.
(i) Gassy operations-additional requirements. (1) Only acceptable equipment,
maintained in suitable condition, shall
be used in gassy operations.
(2) Mobile diesel-powered equipment
used in gassy operations shall be either
approved in accordance with the requirements of 30 CFR part 36 (formerly
Schedule 31) by MSHA, or shall be demonstrated by the employer to be fully
equivalent to such MSHA-approved
equipment, and shall be operated in accordance with that part.
(3) Each entrance to a gassy operation shall be prominently posted with
signs notifying all entrants of the
gassy classification.
(4) Smoking shall be prohibited in all
gassy operations and the employer
shall be responsible for collecting all
personal sources of ignition, such as
matches and lighters, from all persons
entering a gassy operation.
(5) A fire watch as described in
§ 1926.352(e) shall be maintained when
hot work is performed.
(6) Once an operation has met the criteria in paragraph (h)(2) warranting
classification as gassy, all operations
in the affected area, except the following, shall be discontinued until the
operation either is in compliance with
all of the gassy operation requirements
or has been declassified in accordance
with paragraph (h)(3) of this section:
(i) Operations related to the control
of the gas concentration;

§ 1926.800

(ii) Installation of new equipment, or
conversion of existing equipment, to
comply with this paragraph (i); and
(iii) Installation of above-ground controls for reversing the air flow.
(j) Air quality and monitoring—(1) General. Air quality limits and control requirements for construction are found
in § 1926.55, except as modified by this
section.
(i)(A) The employer shall assign a
competent person who shall perform all
air monitoring required by this section.
(B) Where this paragraph requires
monitoring of airborne contaminants
‘‘as often as necessary,’’ the competent
person shall make a reasonable determination as to which substances to
monitor and how frequently to monitor, considering at least the following
factors:
(1) Location of jobsite: Proximity to
fuel tanks, sewers, gas lines, old landfills, coal deposits, and swamps;
(2) Geology: Geological studies of the
jobsite, particularly involving the soil
type and its permeability;
(3) History: Presence of air contaminants in nearby jobsites, changes in
levels of substances monitored on the
prior shift; and
(4) Work practices and jobsite conditions: The use of diesel engines, use of
explosives, use of fuel gas, volume and
flow of ventilation, visible atmospheric
conditions, decompression of the atmosphere, welding, cutting and hot
work, and employees’ physical reactions to working underground.
(ii)(A) The atmosphere in all underground work areas shall be tested as
often as necessary to assure that the
atmosphere at normal atmospheric
pressure contains at least 19.5 percent
oxygen and no more than 22 percent oxygen.
(B) Tests for oxygen content shall be
made before tests for air contaminants.
(iii)(A) The atmosphere in all underground work areas shall be tested
quantitatively for carbon monoxide, nitrogen dioxide, hydrogen sulfide, and
other toxic gases, dusts, vapors, mists,
and fumes as often as necessary to ensure that the permissible exposure limits prescribed in § 1926.55 are not exceeded.

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§ 1926.800

29 CFR Ch. XVII (7–1–07 Edition)

(B) The atmosphere in all underground work areas shall be tested
quantitatively for methane and other
flammable gases as often as necessary
to determine:
(1) Whether action is to be taken
under paragraphs (j)(1)(vii), (viii), and
(ix), of this section; and
(2) Whether an operation is to be
classified potentially gassy or gassy
under paragraph (h) of this section.
(C) If diesel-engine or gasoline-engine
driven ventilating fans or compressors
are used, an initial test shall be made
of the inlet air of the fan or compressor, with the engines operating, to
ensure that the air supply is not contaminated by engine exhaust.
(D) Testing shall be performed as
often as necessary to ensure that the
ventilation requirements of paragraph
(k) of this section are met.
(iv) When rapid excavation machines
are used, a continuous flammable gas
monitor shall be operated at the face
with the sensor(s) placed as high and
close to the front of the machine’s cutter head as practicable.
(v)(A) Whenever air monitoring indicates the presence of 5 ppm or more of
hydrogen sulfide, a test shall be conducted in the affected underground
work area(s), at least at the beginning
and midpoint of each shift, until the
concentration of hydrogen sulfide has
been less than 5 ppm for 3 consecutive
days.
(B) Whenever hydrogen sulfide is detected in an amount exceeding 10 ppm,
a continuous sampling and indicating
hydrogen sulfide monitor shall be used
to monitor the affected work area.
(C) Employees shall be informed
when a concentration of 10 ppm hydrogen sulfide is exceeded.
(D) The continuous sampling and indicating hydrogen sulfide monitor shall
be designed, installed, and maintained
to provide a visual and aural alarm
when the hydrogen sulfide concentration reaches 20 ppm to signal that additional measures, such as respirator use,
increased ventilation, or evacuation,
might be necessary to maintain hydrogen sulfide exposure below the permissible exposure limit.
(vi) When the competent person determines, on the basis of air monitoring results or other information,

that air contaminants may be present
in sufficient quantity to be dangerous
to life, the employer shall:
(A) Prominently post a notice at all
entrances to the underground jobsite
to inform all entrants of the hazardous
condition; and
(B) Ensure that the necessary precautions are taken.
(vii) Whenever five percent or more
of the lower explosive limit for methane or other flammable gases is detected in any underground work area(s)
or in the air return, steps shall be
taken to increase ventilation air volume or otherwise control the gas concentration, unless the employer is operating in accordance with the potentially gassy or gassy operation requirements. Such additional ventilation
controls may be discontinued when gas
concentrations are reduced below five
percent of the lower explosive limit,
but shall be reinstituted whenever the
five percent level is exceeded.
(viii) Whenever 10 percent or more of
the lower explosive limit for methane
or other flammable gases is detected in
the vicinity of welding, cutting, or
other hot work, such work shall be suspended until the concentration of such
flammable gas is reduced to less than
10 percent of the lower explosive limit.
(ix) Whenever 20 percent or more of
the lower explosive limit for methane
or other flammable gases is detected in
any underground work area(s) or in the
air return:
(A) All employees, except those necessary to eliminate the hazard, shall be
immediately withdrawn to a safe location above ground; and
(B) Electrical power, except for acceptable pumping and ventilation
equipment, shall be cut off to the area
endangered by the flammable gas until
the concentration of such gas is reduced to less than 20 percent of the
lower explosive limit.
(2) Additional monitoring for potentially
gassy and gassy operations. Operations
which meet the criteria for potentially
gassy and gassy operations set forth in
paragraph (h) of this section shall be
subject to the additional monitoring
requirements of this paragraph.
(i) A test for oxygen content shall be
conducted in the affected underground

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Occupational Safety and Health Admin., Labor
work areas and work areas immediately adjacent to such areas at least
at the beginning and midpoint of each
shift.
(ii) When using rapid excavation machines, continuous automatic flammable gas monitoring equipment shall
be used to monitor the air at the heading, on the rib, and in the return air
duct. The continuous monitor shall signal the heading, and shut down electric
power in the affected underground
work area, except for acceptable pumping and ventilation equipment, when 20
percent or more of the lower explosive
limit for methane or other flammable
gases is encountered.
(iii) A manual flammable gas monitor shall be used as needed, but at
least at the beginning and midpoint of
each shift, to ensure that the limits
prescribed in paragraphs (h) and (j) are
not exceeded. In addition, a manual
electrical shut down control shall be
provided near the heading.
(iv) Local gas tests shall be made
prior to and continuously during any
welding, cutting, or other hot work.
(v) In underground operations driven
by drill-and-blast methods, the air in
the affected area shall be tested for
flammable gas prior to re-entry after
blasting, and continuously when employees are working underground.
(3) Recordkeeping. A record of all air
quality tests shall be maintained above
ground at the worksite and be made
available to the Secretary of Labor
upon request. The record shall include
the location, date, time, substance and
amount monitored. Records of exposures to toxic substances shall be retained in accordance with § 1910.33 of
this chapter. All other air quality test
records shall be retained until completion of the project.
(k) Ventilation. (1)(i) Fresh air shall
be supplied to all underground work
areas in sufficient quantities to prevent dangerous or harmful accumulation of dusts, fumes, mists, vapors or
gases.
(ii) Mechanical ventilation shall be
provided in all underground work areas
except when the employer can demonstrate that natural ventilation provides the necessary air quality through
sufficient air volume and air flow.

§ 1926.800

(2) A minimum of 200 cubic feet (5.7
m3) of fresh air per minute shall be supplied for each employee underground.
(3) The linear velocity of air flow in
the tunnel bore, in shafts, and in all
other underground work areas shall be
at least 30 feet (9.15 m) per minute
where blasting or rock drilling is conducted, or where other conditions likely to produce dust, fumes, mists, vapors, or gases in harmful or explosive
quantities are present.
(4) The direction of mechanical air
flow shall be reversible.
(5) Following blasting, ventilation
systems shall exhaust smoke and
fumes to the outside atmosphere before
work is resumed in affected areas.
(6) Ventilation doors shall be designed and installed so that they remain closed when in use, regardless of
the direction of the air flow.
(7) When ventilation has been reduced to the extent that hazardous levels of methane or flammable gas may
have accumulated, a competent person
shall test all affected areas after ventilation has been restored and shall determine whether the atmosphere is
within flammable limits before any
power, other than for acceptable equipment, is restored or work is resumed.
(8) Whenever the ventilation system
has been shut down with all employees
out of the underground area, only competent persons authorized to test for
air contaminants shall be allowed underground until the ventilation has
been restored and all affected areas
have been tested for air contaminants
and declared safe.
(9) When drilling rock or concrete,
appropriate dust control measures
shall be taken to maintain dust levels
within limits set in § 1926.55. Such
measures may include, but are not limited to, wet drilling, the use of vacuum
collectors, and water mix spray systems.
(10)(i) Internal combustion engines,
except diesel-powered engines on mobile equipment, are prohibited underground.
(ii) Mobile diesel-powered equipment
used underground in atmospheres other
than gassy operations shall be either
approved by MSHA in accordance with

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§ 1926.800

29 CFR Ch. XVII (7–1–07 Edition)

the provisions of 30 CFR part 32 (formerly Schedule 24), or shall be demonstrated by the employer to be fully
equivalent to such MSHA-approved
equipment, and shall be operated in accordance with that part. (Each brake
horsepower of a diesel engine requires
at least 100 cubic feet (28.32 m3) of air
per minute for suitable operation in addition to the air requirements for personnel. Some engines may require a
greater amount of air to ensure that
the allowable levels of carbon monoxide, nitric oxide, and nitrogen dioxide are not exceeded.)
(11) Potentially gassy or gassy operations shall have ventilation systems
installed which shall:
(i) Be constructed of fire-resistant
materials; and
(ii) Have acceptable electrical systems, including fan motors.
(12) Gassy operations shall be provided with controls located above
ground for reversing the air flow of
ventilation systems.
(13) In potentially gassy or gassy operations, wherever mine-type ventilation systems using an offset main fan
installed on the surface are used, they
shall be equipped with explosion-doors
or a weak-wall having an area at least
equivalent to the cross-sectional area
of the airway.
(l) Illumination. (1) Illumination requirements applicable to underground
construction operations are found in
Table D–3 of § 1926.56 of this part.
(2) Only acceptable portable lighting
equipment shall be used within 50 feet
(15.24 m) of any underground heading
during explosives handling.
(m) Fire prevention and control. Fire
prevention and protection requirements applicable to underground construction operations are found in subpart F of this part, except as modified
by the following additional standards.
(1) Open flames and fires are prohibited in all underground construction
operations except as permitted for
welding, cutting and other hot work
operations in paragraph (n) of this section.
(2) (i) Smoking may be allowed only
in areas free of fire and explosion hazards.
(ii) Readily visible signs prohibiting
smoking and open flames shall be post-

ed in areas having fire or explosion
hazards.
(3) The employer may store underground no more than a 24-hour supply
of diesel fuel for the underground
equipment used at the worksite.
(4) The piping of diesel fuel from the
surface to an underground location is
permitted only if:
(i) Diesel fuel is contained at the surface in a tank whose maximum capacity is no more than the amount of fuel
required to supply for a 24-hour period
the equipment serviced by the underground fueling station; and
(ii) The surface tank is connected to
the underground fueling station by an
acceptable pipe or hose system that is
controlled at the surface by a valve,
and at the shaft bottom by a hose nozzle; and
(iii) The pipe is empty at all times
except when transferring diesel fuel
from the surface tank to a piece of
equipment in use underground; and
(iv) Hoisting operations in the shaft
are suspended during refueling operations if the supply piping in the shaft
is not protected from damage.
(5)(i) Gasoline shall not be carried,
stored, or used underground.
(ii) Acetylene, liquefied petroleum
gas, and Methylacetylene Propadiene
Stabilized gas may be used underground only for welding, cutting and
other hot work, and only in accordance
with subpart J of this part, and paragraphs (j), (k), (m), and (n) of this section.
(6) Oil, grease, and diesel fuel stored
underground shall be kept in tightly
sealed containers in fire-resistant areas
at least 300 feet (91.44 m) from underground explosive magazines, and at
least 100 feet (30.48 m) from shaft stations and steeply inclined passageways.
Storage areas shall be positioned or
diked so that the contents of ruptured
or overturned containers will not flow
from the storage area.
(7) Flammable or combustible materials shall not be stored above ground
within 100 feet (30.48 m) of any access
opening to any underground operation.
Where this is not feasible because of
space limitations at the jobsite, such
materials may be located within the
100-foot limit, provided that:

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Occupational Safety and Health Admin., Labor
(i) They are located as far as practicable from the opening; and
(ii) Either a fire-resistant barrier of
not less than one-hour rating is placed
between the stored material and the
opening, or additional precautions are
taken which will protect the materials
from ignition sources.
(8) Fire-resistant hydraulic fluids
shall be used in hydraulically-actuated
underground machinery and equipment
unless such equipment is protected by
a fire suppression system or by multipurpose fire extinguisher(s) rated at of
sufficient capacity for the type and size
of hydraulic equipment involved, but
rated at least 4A:40B:C.
(9)(i) Electrical installations in underground areas where oil, grease, or
diesel fuel are stored shall be used only
for lighting fixtures.
(ii) Lighting fixtures in storage
areas, or within 25 feet (7.62 m) of underground areas where oil, grease, or
diesel fuel are stored, shall be approved
for Class I, Division 2 locations, in accordance with subpart K of this part.
(10) Leaks and spills of flammable or
combustible fluids shall be cleaned up
immediately.
(11) A fire extinguisher of at least
4A:40B:C rating or other equivalent extinguishing means shall be provided at
the head pulley and at the tail pulley
of underground belt conveyors.
(12) Any structure located underground or within 100 feet (30.48 m) of an
opening to the underground shall be
constructed of material having a fireresistance rating of at least one hour.
(n) Welding, cutting, and other hot
work. In addition to the requirements
of subpart J of this part, the following
requirements shall apply to underground welding, cutting, and other hot
work.
(1) No more than the amount of fuel
gas and oxygen cylinders necessary to
perform welding, cutting, or other hot
work during the next 24-hour period
shall be permitted underground.
(2) Noncombustible barriers shall be
installed below welding, cutting, or
other hot work being done in or over a
shaft or raise.
(o) Ground support—(1) Portal areas.
Portal openings and access areas shall
be guarded by shoring, fencing, head
walls, shotcreting or other equivalent

§ 1926.800

protection to ensure safe access of employees and equipment. Adjacent areas
shall be scaled or otherwise secured to
prevent loose soil, rock, or fractured
materials from endangering the portal
and access area.
(2) Subsidence areas. The employer
shall ensure ground stability in hazardous subsidence areas by shoring, by
filling in, or by erecting barricades and
posting warning signs to prevent entry.
(3) Underground areas. (i)(A) A competent person shall inspect the roof,
face, and walls of the work area at the
start of each shift and as often as necessary to determine ground stability.
(B) Competent persons conducting
such inspections shall be protected
from loose ground by location, ground
support or equivalent means.
(ii)
Ground
conditions
along
haulageways and travelways shall be
inspected as frequently as necessary to
ensure safe passage.
(iii) Loose ground that might be hazardous to employees shall be taken
down, scaled or supported.
(iv) (A) Torque wrenches shall be
used wherever bolts that depend on
torsionally applied force are used for
ground support.
(B) A competent person shall determine whether rock bolts meet the necessary torque, and shall determine the
testing frequency in light of the bolt
system, ground conditions and the distance from vibration sources.
(v) Suitable protection shall be provided for employees exposed to the hazard of loose ground while installing
ground support systems.
(vi) Support sets shall be installed so
that the bottoms have sufficient anchorage to prevent ground pressures
from dislodging the support base of the
sets. Lateral bracing (collar bracing,
tie rods, or spreaders) shall be provided
between immediately adjacent sets to
ensure added stability.
(vii) Damaged or dislodged ground
supports that create a hazardous condition shall be promptly repaired or replaced. When replacing supports, the
new supports shall be installed before
the damaged supports are removed.
(viii) A shield or other type of support shall be used to maintain a safe
travelway for employees working in

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§ 1926.800

29 CFR Ch. XVII (7–1–07 Edition)

dead-end areas ahead of any support replacement operation.
(4) Shafts. (i) Shafts and wells over 5
feet (1.53 m) in depth that employees
must enter shall be supported by a
steel casing, concrete pipe, timber,
solid rock or other suitable material.
(ii) (A) The full depth of the shaft
shall be supported by casing or bracing
except where the shaft penetrates into
solid rock having characteristics that
will not change as a result of exposure.
Where the shaft passes through earth
into solid rock, or through solid rock
into earth, and where there is potential
for shear, the casing or bracing shall
extend at least 5 feet (1.53 m) into the
solid rock. When the shaft terminates
in solid rock, the casing or bracing
shall extend to the end of the shaft or
5 feet (1.53 m) into the solid rock,
whichever is less.
(B) The casing or bracing shall extend 42 inches (1.07 m) plus or minus 3
inches (8 cm) above ground level, except that the minimum casing height
may be reduced to 12 inches (0.3 m),
provided that a standard railing is installed; that the ground adjacent to the
top of the shaft is sloped away from the
shaft collar to prevent entry of liquids;
and that effective barriers are used to
prevent mobile equipment operating
near the shaft from jumping over the 12
inch (0.3 m) barrier.
(iii) After blasting operations in
shafts, a competent person shall determine if the walls, ladders, timbers,
blocking, or wedges have loosened. If
so, necessary repairs shall be made before employees other than those assigned to make the repairs are allowed
in or below the affected areas.
(p) Blasting. This paragraph applies in
addition to the requirements for blasting and explosives operations, including handling of misfires, which are
found in subpart U of this part.
(1) Blasting wires shall be kept clear
of electrical lines, pipes, rails, and
other conductive material, excluding
earth, to prevent explosives initiation
or employee exposure to electric current.
(2) Following blasting, an employee
shall not enter a work area until the
air quality meets the requirements of
paragraph (j) of this section.

(q) Drilling. (1) A competent person
shall inspect all drilling and associated
equipment prior to each use. Equipment defects affecting safety shall be
corrected before the equipment is used.
(2) The drilling area shall be inspected for hazards before the drilling
operation is started.
(3) Employees shall not be allowed on
a drill mast while the drill bit is in operation or the drill machine is being
moved.
(4) When a drill machine is being
moved from one drilling area to another, drill steel, tools, and other
equipment shall be secured and the
mast shall be placed in a safe position.
(5) Receptacles or racks shall be provided for storing drill steel located on
jumbos.
(6) Employees working below jumbo
decks shall be warned whenever drilling is about to begin.
(7) Drills on columns shall be anchored firmly before starting drilling,
and shall be retightened as necessary
thereafter.
(8) (i) The employer shall provide mechanical means on the top deck of a
jumbo for lifing unwieldy or heavy material.
(ii) When jumbo decks are over 10
feet (3.05 m) in height, the employer
shall install stairs wide enough for two
persons.
(iii) Jumbo decks more than 10 feet
(3.05 m) in height shall be equipped
with guardrails on all open sides, excluding access openings of platforms,
unless an adjacent surface provides
equivalent fall protection.
(iv) (A) Only employees assisting the
operator shall be allowed to ride on
jumbos, unless the jumbo meets the requirements of paragraph (r)(6)(ii) of
this section.
(B) Jumbos shall be chocked to prevent movement while employees are
working on them.
(v) (A) Walking and working surfaces
of jumbos shall be maintained to prevent the hazards of slipping, tripping
and falling.
(B) Jumbo decks and stair treads
shall be designed to be slip-resistent
and secured to prevent accidental displacement.

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Occupational Safety and Health Admin., Labor
(9) Scaling bars shall be available at
scaling operations and shall be maintained in good condition at all times.
Blunted or severely worn bars shall not
be used.
(10) (i) Blasting holes shall not be
drilled through blasted rock (muck) or
water.
(ii) Employees in a shaft shall be protected either by location or by suitable
barrier(s) if powered mechanical loading equipment is used to remove muck
containing unfired explosives.
(11) A caution sign reading ‘‘Buried
Line,’’ or similar wording shall be posted where air lines are buried or otherwise hidden by water or debris.
(r) Haulage. (1)(i) A competent person
shall inspect haulage equipment before
each shift.
(ii) Equipment defects affecting safety and health shall be corrected before
the equipment is used.
(2) Powered mobile haulage equipment shall have suitable means of stopping.
(3)(i) Power mobile haulage equipment, including trains, shall have audible warning devices to warn employees
to stay clear. The operator shall sound
the warning device before moving the
equipment and whenever necessary
during travel.
(ii) The operator shall assure that
lights which are visible to employees
at both ends of any mobile equipment,
including a train, are turned on whenever the equipment is operating.
(4) In those cabs where glazing is
used, the glass shall be safety glass, or
its equivalent, and shall be maintained
and cleaned so that vision is not obstructed.
(5) Anti-roll back devices or brakes
shall be installed on inclined conveyor
drive units to prevent conveyors from
inadvertently running in reverse.
(6)(i) (A) Employees shall not be permitted to ride a power-driven chain,
belt, or bucket conveyor unless the
conveyor is specifically designed for
the transportation of persons.
(B) Endless belt-type manlifts are
prohibited in underground construction.
(C) General requirements also applicable to underground construction for
use of conveyors in construction are
found in § 1926.555 of this part.

§ 1926.800

(ii) No employee shall ride haulage
equipment unless it is equipped with
seating for each passenger and protects
passengers from being struck, crushed,
or caught between other equipment or
surfaces. Members of train crews may
ride on a locomotive if it is equipped
with handholds and nonslip steps or
footboards. Requirements applicable to
Underground Construction for motor
vehicle transportation of employees
are found in § 1926.601 of this part.
(7) Powered mobile haulage equipment, including trains, shall not be left
unattended unless the master switch or
motor is turned off; operating controls
are in neutral or park position; and the
brakes are set, or equivalent precautions are taken to prevent rolling.
(8) Whenever rails serve as a return
for a trolley circuit, both rails shall be
bonded at every joint and crossbonded
every 200 feet (60.96 m).
(9) When dumping cars by hand, the
car dumps shall have tiedown chains,
bumper blocks, or other locking or
holding devices to prevent the cars
from overturning.
(10) Rocker-bottom or bottom-dump
cars shall be equipped with positive
locking devices to prevent unintended
dumping.
(11) Equipment to be hauled shall be
loaded and secured to prevent sliding
or dislodgement.
(12)(i) Mobile equipment, including
rail-mounted equipment, shall be
stopped for manual connecting or service work.
(ii) Employees shall not reach between moving cars during coupling operations.
(iii) Couplings shall not be aligned,
shifted or cleaned on moving cars or locomotives.
(13)(i) Safety chains or other connections shall be used in addition to couplers to connect man cars or powder
cars whenever the locomotive is uphill
of the cars.
(ii) When the grade exceeds one percent and there is a potential for runaway cars, safety chains or other connections shall be used in addition to
couplers to connect haulage cars or, as
an alternative, the locomotive must be
downhill of the train.

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29 CFR Ch. XVII (7–1–07 Edition)

(iii) Such safety chains or other connections shall be capable of maintaining connection between cars in the
event of either coupler disconnect, failure or breakage.
(14) Parked rail equipment shall be
chocked, blocked, or have brakes set to
prevent inadvertent movement.
(15) Berms, bumper blocks, safety
hooks, or equivalent means shall be
provided to prevent overtravel and
overturning of haulage equipment at
dumping locations.
(16) Bumper blocks or equivalent
stopping devices shall be provided at
all track dead ends.
(17)(i) Only small handtools, lunch
pails or similar small items may be
transported with employees in mancars, or on top of a locomotive.
(ii) When small hand tools or other
small items are carried on top of a locomotive, the top shall be designed or
modified to retain them while traveling.
(18)(i) Where switching facilities are
available, occupied personnel-cars shall
be pulled, not pushed. If personnel-cars
must be pushed and visibility of the
track ahead is hampered, then a qualified person shall be stationed in the
lead car to give signals to the locomotive operator.
(ii) Crew trips shall consist of personnel-loads only.
(s) Electrical safety. This paragraph
applies in addition to the general requirements for electrical safety which
are found in subpart K of this part.
(1) Electric power lines shall be insulated or located away from water lines,
telephone lines, air lines, or other conductive materials so that a damaged
circuit will not energize the other systems.
(2) Lighting circuits shall be located
so that movement of personnel or
equipment will not damage the circuits
or disrupt service.
(3) Oil-filled transformers shall not
be used underground unless they are located in a fire-resistant enclosure suitably vented to the outside and surrounded by a dike to retain the contents of the transformers in the event
of rupture.
(t) Hoisting unique to underground construction. Except as modified by this
paragraph (t), the following provisions

of subpart N of this part apply: Requirements for cranes are found in
§ 1926.550 of this part. Paragraph (g) of
§ 1926.550 applies to crane-hoisting of
personnel, except that the limitation
in paragraph (g)(2) does not apply to
the routine access of employees to the
underground via a shaft. Requirements
for material hoists are found in
§ 1926.552 (a) and (b) of this part. Requirements for personnel hoists are
found in the personnel hoist requirements of § 1926.552 (a) and (c) of this
part and in the elevator requirement of
§ 1926.552 (a) and (d) of this part.
(1) General requirements for cranes and
hoists. (i) Materials, tools, and supplies
being raised or lowered, whether within
a cage or otherwise, shall be secured or
stacked in a manner to prevent the
load from shifting, snagging or falling
into the shaft.
(ii) A warning light suitably located
to warn employees at the shaft bottom
and subsurface shaft entrances shall
flash whenever a load is above the
shaft bottom or subsurface entrances,
or the load is being moved in the shaft.
This paragraph does not apply to fully
enclosed hoistways.
(iii) Whenever a hoistway is not fully
enclosed and employees are at the
shaft bottom, conveyances or equipment shall be stopped at least 15 feet
(4.57 m) above the bottom of the shaft
and held there until the signalman at
the bottom of the shaft directs the operator to continue lowering the load,
except that the load may be lowered
without stopping if the load or conveyance is within full view of a bottom
signalman who is in constant voice
communication with the operator.
(iv) (A) Before maintenance, repairs,
or other work is commenced in the
shaft served by a cage, skip, or bucket,
the operator and other employees in
the area shall be informed and given
suitable instructions.
(B) A sign warning that work is being
done in the shaft shall be installed at
the shaft collar, at the operator’s station, and at each underground landing.
(v) Any connection between the
hoisting rope and the cage or skip shall
be compatible with the type of wire
rope used for hoisting.
(vi) Spin-type connections, where
used, shall be maintained in a clean

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Occupational Safety and Health Admin., Labor
condition and protected from foreign
matter that could affect their operation.
(vii) Cage, skip, and load connections
to the hoist rope shall be made so that
the force of the hoist pull, vibration,
misalignment, release of lift force, or
impact will not disengage the connection. Moused or latched open-throat
hooks do not meet this requirement.
(viii) When using wire rope wedge
sockets, means shall be provided to
prevent wedge escapement and to ensure that the wedge is properly seated.
(2) Additional requirements for cranes.
Cranes shall be equipped with a limit
switch to prevent overtravel at the
boom tip. Limit switches are to be used
only to limit travel of loads when operational controls malfunction and shall
not be used as a substitute for other
operational controls.
(3) Additional requirements for hoists.
(i) Hoists shall be designed so that the
load hoist drum is powered in both directions of rotation, and so that brakes
are automatically applied upon power
release or failure.
(ii) Control levers shall be of the
‘‘deadman type’’ which return automatically to their center (neutral) position upon release.
(iii) When a hoist is used for both
personnel hoisting and material hoisting, load and speed ratings for personnel and for materials shall be assigned to the equipment.
(iv) Material hoisting may be performed at speeds higher than the rated
speed for personnel hoisting if the hoist
and components have been designed for
such higher speeds and if shaft conditions permit.
(v) Employees shall not ride on top of
any cage, skip or bucket except when
necessary to perform inspection or
maintenance of the hoisting system, in
which case they shall be protected by a
body belt/harness system to prevent
falling.
(vi) Personnel and materials (other
than small tools and supplies secured
in a manner that will not create a hazards to employees) shall not be hoisted
together in the same conveyance. However, if the operator is protected from
the shifting of materials, then the operator may ride with materials in
cages or skips which are designed to be

§ 1926.800

controlled by an operator within the
cage or skip.
(vii) Line speed shall not exceed the
design limitations of the systems.
(viii) Hoists shall be equipped with
landing level indicators at the operator’s station. Marking of the hoist rope
does not satisfy this requirement.
(ix) Whenever glazing is used in the
hoist house, it shall be safety glass, or
its equivalent, and be free of distortions and obstructions.
(x) A fire extinguisher that is rated
at least 2A:10B:C (multi-purpose, dry
chemical) shall be mounted in each
hoist house.
(xi) Hoist controls shall be arranged
so that the operator can perform all
operating cycle functions and reach the
emergency power cutoff without having to reach beyond the operator’s normal operating position.
(xii) Hoists shall be equipped with
limit switches to prevent overtravel at
the top and bottom of the hoistway.
(xiii) Limit switches are to be used
only to limit travel of loads when operational controls malfunction and shall
not be used as a substitute for other
operational controls.
(xiv) Hoist operators shall be provided with a closed-circuit voice communication system to each landing station, with speaker-microphones so located that the operator can communicate with individual landing stations
during hoist use.
(xv) When sinking shafts 75 feet (22.86
m) or less in depth, cages, skips, and
buckets that may swing, bump, or snag
against shaft sides or other structural
protrusions shall be guided by fenders,
rails, ropes, or a combination of those
means.
(xvi) When sinking shafts more than
75 feet (22.86 m) in depth, all cages,
skips, and buckets shall be rope or railguided to within a rail length from the
sinking operation.
(xvii) Cages, skips, and buckets in all
completed shafts, or in all shafts being
used as completed shafts, shall be rope
or rail-guided for the full length of
their travel.
(xviii) Wire rope used in load lines of
material hoists shall be capable of supporting, without failure, at least five
times the maximum intended load or
the factor recommended by the rope

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§ 1926.800

29 CFR Ch. XVII (7–1–07 Edition)

manufacturer, whichever is greater.
Refer to § 1926.552(c)(14)(iii) of this part
for design factors for wire rope used in
personnel hoists. The design factor
shall be calculated by dividing the
breaking strength of wire rope, as reported in the manufacturer’s rating tables, by the total static load, including
the weight of the wire rope in the shaft
when fully extended.
(xix) A competent person shall visually check all hoisting machinery,
equipment, anchorages, and hoisting
rope at the beginning of each shift and
during hoist use, as necessary.
(xx) Each safety device shall be
checked by a competent person at least
weekly during hoist use to ensure suitable operation and safe condition.
(xxi) In order to ensure suitable operation and safe condition of all functions and safety devices, each hoist assembly shall be inspected and loadtested to 100 percent of its rated capacity: at the time of installation; after
any repairs or alterations affecting its
structural integrity; after the operation of any safety device; and annually when in use. The employer shall
prepare a certification record which includes the date each inspection and
load-test was performed; the signature
of the person who performed the inspection and test; and a serial number
or other identifier for the hoist that
was inspected and tested. The most recent certification record shall be maintained on file until completion of the
project.
(xxii) Before hoisting personnel or
material, the operator shall perform a
test run of any cage or skip whenever
it has been out of service for one complete shift, and whenever the assembly
or components have been repaired or
adjusted.
(xxiii) Unsafe conditions shall be corrected before using the equipment.
(4) Additional requirements for personnel hoists. (i) Hoist drum systems
shall be equipped with at least two
means of stopping the load, each of
which shall be capable of stopping and
holding 150 percent of the hoist’s rated
line pull. A broken-rope safety, safety
catch, or arrestment device is not a
permissible means of stopping under
this paragraph.

(ii) The operator shall remain within
sight and sound of the signals at the
operator’s station.
(iii) All sides of personnel cages shall
be enclosed by one-half inch (12.70 mm)
wire mesh (not less than No. 14 gauge
or equivalent) to a height of not less
than 6 feet (1.83 m). However, when the
cage or skip is being used as a work
platform, its sides may be reduced in
height to 42 inches 1.07 m) when the
conveyance is not in motion.
(iv) All personnel cages shall be provided with positive locking door that
does not open outward.
(v) All personnel cages shall be provided with a protective canopy. The
canopy shall be made of steel plate, at
least 3⁄16-inch (4.763 mm) in thickness,
or material of equivalent strength and
impact resistance. The canopy shall be
sloped to the outside, and so designed
that a section may be readily pushed
upward to afford emergency egress.
The canopy shall cover the top in such
a manner as to protect those inside
from objects falling in the shaft.
(vi) Personnel platforms operating on
guide rails or guide ropes shall be
equipped with broken-rope safety devices, safety catches or arrestment devices that will stop and hold 150 percent of the weight of the personnel
platform and its maximum rated load.
(vii) During sinking operations in
shafts where guides and safeties are
not yet used, the travel speed of the
personnel platform shall not exceed 200
feet (60.96 m) per minute. Governor
controls set for 200 feet (60.96 m) per
minute shall be installed in the control
system and shall be used during personnel hoisting.
(viii) The personnel platform may
travel over the controlled length of the
hoistway at rated speeds up to 600 feet
(182.88 m) per minute during sinking
operations in shafts where guides and
safeties are used.
(ix) The personnel platform may
travel at rated speeds greater than 600
feet (182.88 m) per minute in completed
shafts.
(u) Definitions. ‘‘Accept’’—Any device, equipment, or appliance that is
either approved by MSHA and maintained in permissible condition, or is
listed or labeled for the class and location under subpart K of this part.

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Occupational Safety and Health Admin., Labor
‘‘Rapid Excavation Machine’’—Tunnel
boring
machines,
shields,
roadheaders, or any other similar excavation machine.
[54 FR 23850, June 2, 1989; 58 FR 35311, June
30, 1993, as amended at 61 FR 5510, Feb. 13,
1996; 63 FR 1297, Jan. 8, 1998; 71 FR 16674, Apr.
3, 2006]

§ 1926.801

Caissons.

(a) Wherever, in caisson work in
which compressed air is used, and the
working chamber is less than 11 feet in
length, and when such caissons are at
any time suspended or hung while work
is in progress so that the bottom of the
excavation is more than 9 feet below
the deck of the working chamber, a
shield shall be erected therein for the
protection of the employees.
(b) Shafts shall be subjected to a hydrostatic or air-pressure test, at which
pressure they shall be tight. The shaft
shall be stamped on the outside shell
about 12 inches from each flange to
show the pressure to which they have
been subjected.
(c) Whenever a shaft is used, it shall
be provided, where space permits, with
a safe, proper, and suitable staircase
for its entire length, including landing
platforms, not more than 20 feet apart.
Where this is impracticable, suitable
ladders shall be installed with landing
platforms located about 20 feet apart to
break the climb.
(d) All caissons having a diameter or
side greater than 10 feet shall be provided with a man lock and shaft for the
exclusive use of employees.
(e) In addition to the gauge in the
locks, an accurate gauge shall be maintained on the outer and inner side of
each bulkhead. These gauges shall be
accessible at all times and kept in accurate working order.
(f) In caisson operations where employees are exposed to compressed air
working environments, the requirements contained in § 1926.803 shall be
complied with.
§ 1926.802

Cofferdams.

(a) If overtopping of the cofferdam by
high waters is possible, means shall be
provided for controlled flooding of the
work area.

§ 1926.803

(b) Warning signals for evacuation of
employees in case of emergency shall
be developed and posted.
(c) Cofferdam walkways, bridges, or
ramps with at least two means of rapid
exit shall be provided with guardrails
as specified in subpart M of this part.
(d) Cofferdams located close to navigable shipping channels shall be protected from vessels in transit, where
possible.
§ 1926.803 Compressed air.
(a) General provisions. (1) There shall
be present, at all times, at least one
competent person designated by and
representing the employer, who shall
be familiar with this subpart in all respects, and responsible for full compliance with these and other applicable
subparts.
(2) Every employee shall be instructed in the rules and regulations
which concern his safety or the safety
of others.
(b) Medical attendance, examination,
and regulations. (1) There shall be retained one or more licensed physicians
familiar with and experienced in the
physical requirements and the medical
aspects of compressed air work and the
treatment of decompression illness. He
shall be available at all times while
work is in progress in order to provide
medical supervision of employees employed in compressed air work. He
shall himself be physically qualified
and be willing to enter a pressurized
environment.
(2) No employee shall be permitted to
enter a compressed air environment
until he has been examined by the physician and reported by him to be physically qualified to engage in such work.
(3) In the event an employee is absent
from work for 10 days, or is absent due
to sickness or injury, he shall not resume work until he is reexamined by
the physician, and his physical condition reported, as provided in this paragraph, to be such as to permit him to
work in compressed air.
(4) After an employee has been employed continuously in compressed air
for a period designated by the physician, but not to exceed 1 year, he shall
be reexamined by the physician to determine if he is still physically qualified to engage in compressed air work.

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