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Structural Issues• Rock Fall - Fall of rock blocks of major
dimensions. The different mechanisms involved are wedge or planar failure..
• Collapse Heading collapse - failure of the heading / lining failure .
• Daylight Collapse Heading collapse - lining failure of the heading that reaches the surface creating a crater.
• Excessive Deformation - Excessive deformations inside the tunnel or at the surface. This can occur for example due to deficient design, construction defects and/or due to particular type of terrains such as swelling and squeezing ground, which had not been predicted.
• Flooding - Comprises cases where the tunnel was invaded by large quantities of underground water.
• Rock Burst - Spalling Overstressing of massive or intact brittle rock, i.e. the stresses developed in the ground exceed the local strength of the material. It can cause spalling or in the worst cases sudden and violent failure of the rock mass
• Portal failure - Particular locations of a tunnel, where there is a lower
• Shaft failure - resistance of ground mass and/ or concentration of stresses.
• Other - Other types of collapse that include slope failures, etc
Structural Failures
Rock Fall
• Rock fall blocking the TBM at the Covao tunnel in 2006 (Madeira Island, Portugal)
Collapse
• The large collapse occurred in front of the face and stopped the cutter head rotation, creating a cavern more than 10 m high over the TBM.
• This was an example of a full collapse of the face.
Collapse• Wienerwald Austria• In this case, ground water
led to de-compaction and bulking of the sandstone, which caused the shear strength to decrease.
• From this it follows that the strength of rock was very low and ground pressure loaded the temporary shotcrete shell, which was not designed for that kind of high loading.
• Therefore the shotcrete shell spalled off and the lattice girder was deformed.
Daylight Collapse
• These are collapses that reach the surface creating a crater.
• Munich Metro in 1994• No deaths
Daylight Collapse• Sao Paulo Brazil 2007• 7 deaths• Open face tunnelling is cheap. • New Austrian Tunnelling
Method (NATM) is much less expensive than a soft ground TBM, but much less safe
• A combination of explosives and mechanical excavation techniques were being used.
• 'The top heading of the failed tunnel was fully excavated in rock.
• There was approximately 6m of rock above the tunnel,
• Support consisted of steel arch girders at 800mm centres, and 350mm thick steel fibre reinforced sprayed concrete.
• 'The vertical displacements measured at the tunnel crown were in the range of 3mm when the top heading excavation was completed.
• Two to three days before the accident, the rate of those displacements increased, and they reached 15mm to 20mm.
Daylight Collapse • 2003: Shanghai's underground Pearl
Line, China• $80 million• The accident occurred in a cross
passage between the two parallel tunnel tubes that had already been driven using earth-pressure-balance TBMs.
• Shortly before the cross passage broke through, at a depth of about 35 m, massive inrushes of material and water occurred, which the tunnel crew was not able to bring under control and which resulted in a large scale subsidence at the
Daylight Collapse• South Korean city of Taegu on
22 January 2001• Failure of a diaphragm wall.• Part of a station excavation pit
caved in, burying a bus, killing three passengers and damaging neighboring buildings.
• The accident was caused by a load not considered in the design phases and due to unforeseen soil conditions.
• $24 million
Flooding• It is during the construction
of underwater tunnels that largest scale floodings have occurred.
• The ground under rivers, channels and bays is normally weak and under high water pressure and therefore extreme safety measures and efficient protection against water inflow are normally required.
Flooding• Seikan tunnel is a 53.85 km long
railway tunnel in Japan• 1963-1976• Four floods • 23 deaths• Leaks and soft rock• TBM not practical due to the various
types of soils. • Drill and pound.• A great majority of the tunnel crosses
heavily fissured rock (9 large shear zones). The sea and underground water penetrate into these zones and the maximum water pressure is about 25 MPa
Flooding
• Lausanne, Switzerland• A huge amount of soil
and water (1400m3) displaced into the tunnel and caused extensive damage
Rockburst/Spalling• This type of event is
caused by the overstressing of massive or intact brittle rock, i.e. the stresses developed in the ground exceed the local strength of the material.
• It can cause spalling or in the worst cases sudden and violent failure of the rock mass
Excessive Deformation• These are cases where
excessive deformations occur inside the tunnel or at the surface but an actual total collapse does not happen.
• This can occur for example due to deficient design, construction defects and/or due to particular type of terrains such as swelling and squeezing ground, which had not been predicted.
Excessive Deformation• Rotarelle to San Vittore tunnel,
Italy 1991• After 650m of excavation,
enormous ground pressures caused cracking of the shotcrete, buckling of the steel arches after a few hours, and deformations of 200 mm in 24h and 400 mm after 12 days
• The deformations were caused by swelling clay filling of the rock.
Excessive Deformation
• Squeezing is characterized large time-dependent convergence during tunnel excavation.
• Failure of the support system.
• Inadequate support for such ground conditions.
1999: Bolu Tunnel, TurkeyAn earthquake caused the collapse of a section of the Bolu tunnel, part of the Anatolian highway, even though the tunnel had been designed to withstand earthquakes. $115 million loss
1908-1913
• Lotschberg tunnel • Switzerland• Use of timber supports
after collapse killed 25 in 1908
Hawks Nest WV• 1930s• A simple diversion tunnel for
the New River in West Virginia • After workers discovered silica
in the rock they were told to mine it as a by-product of tunnel construction, however, they were never given any masks or protective gear.
• Hundreds of workers developed silicosis due to the long-term exposure of silica dust in their lungs.
New York City Third Water Tunnel
• The largest infrastructure project in New York state history is currently tunneling below New Yorker's feet to provide a third connection to the upstate water supply
St. Gotthard Road Tunnel, 1969-1980
• At the time it was completed, this 10-mile tunnel in Switzerland was the longest road tunnel in the world.
• Tragically, 19 people died working on the tunnel—which was created to connect central Switzerland with Milan, Italy through the Alps, providing a faster and safer year-round alternative to the winding Gotthard Pass.
Big Dig Ceiling Collapse• July 10, 2006• Concrete ceiling panel and debris
weighing 26 tons fell in Boston's Fort Point Channel Tunnel
• The panel fell on a car killing a passenger and injuring the driver.
• The collapse of the ceiling structure began with the simultaneous creep-type failure of several anchors embedded in epoxy in the tunnel's roof slab.
• Each of the panel's intersecting connection points consists of several individual bolts anchored into the roof slab concrete.
• The failure of a group of anchors set off a chain reaction which caused other adjacent connection groups to creep then fail
Big Dig Ceiling Collapse
• Not only were the bolts too short, but the epoxy used to glue the bolts into the concrete was not up to standard.
Big Dig Ceiling Collapse
• Major cause of the collapse to "epoxy creep“
• On August 8, 2007, a Suffolk County Grand Jury indicted epoxy company Powers Fasteners, Inc., on one charge of involuntary manslaughter, with the maximum penalty in Massachusetts being a fine of one thousand dollars.[10]
• The epoxy used in the D Street portal that failed cost $1287.60. The cost to redesign, inspect, and repair all of the tunnels after the collapse was $54 million.[1
2004: Circle Line, Singapore• Collapse of a construction
pit resulted in the death of four workers plus the collapse of an adjoining highway.
• It eventually was found that the most apparent cause of the collapse was that the retaining wall could not handle the stress of holding up the tunnel, forcing it to give way.
1994: Heathrow Express Link• London• Three tunnels forming part of the
Heathrow Express Link, connecting central London and Heathrow Airport, caved in and took several buildings with them.
• $141 million• According to the HSE, a chain of events
led directly to the collapse. • This included a failure to check
substandard construction over a period of some three months, pressure grouting that damaged the tunnel plus inadequately executed repairs some two months before the collapse.
1994/95: Metro• Taipei, Taiwan• When the Metro was being built in
Taiwan in the 1990s, several serious tunnel collapses occurred, causing major property damage to adjacent buildings as well as serious liability losses.
• $41 million• Difficult geology, with fractured rock
and massive inflows of water, countless cave-ins, mud and rock slides caused by massive inflows of groundwater.
• Eleven people were killed in the accidents.
1999: Tunnel in Hull• England• During one of the tunnel drives
for a 6.5 mile underground sewer in Hull, England, a deformation in the floor of the tunnel shell led to flooding of the tunnel and subsidence at the surface, resulting in substantial damage to buildings, roads and utility lines.
• Machines and the tunnel were abandoned.
• $55 million
XIAN Subway• 2013 China• At least two are dead after an
accident at a subway construction site in Xi’an, Shaanxi province this morning.
• At around 2:40 am, a tunnel caved in as nine workers were in the midst of building Line 3.
• Four have been rescued, but of the five that were buried, two have been found dead while the other three are still missing
Dec 2014
• Vietnam• Rescuers have created a
16 cm-wide access hole to the location where 12 workers have been trapped inside a collapsed tunnel section at a hydropower plant in the Central Highlands province of Lam Dong
They may have assumed that the dry season had come and it was safe to dig, but this year the rainy season lasted too long. With heavy rains making the foundation weak, sinkages occurred in the tunnel. And given the Central Highlands’ geological formations, digging up a big rock may lead to the whole tunnel’s collapse.
2000• Dulles Airport• One dead• At the time of the accident, about
700 ft of the approximately 40 ft wide by 16 ft tall tunnel had been excavated.
• Employee #1 was using a shotcrete hose to spray the side walls at the tunnel's earthen face when the top and side of the tunnel collapsed.
• In the week before the tunnel gave way, there were three partial collapses, each increasing in severity
July 2015
• A construction worker who was killed when a winch he was operating broke loose from its anchor at a tunneling site in the High Desert has been identified as David Padilla, 38, of Pahrump, Nevada.
February 2015
• Seattle WA• WSDOT now says five
workers were installing rebar for a concrete wall at the tunnel’s north portal work zone.
• The wall of rebar gave way, injuring four of the five workers.
• Drill and Blast Method • – Method of rock cavern
excavation with the use of • explosives. • Most suitable for hard rock
with complex layout • and geometry • Unique hazards due to need
for blasting • Work is carried out in a
cyclic manner
Tunnel Cycle
• Uncertainty in the nature and variability of ground conditions (rock quality, ground water, gas, etc) -
• need for adequate site investigations prior to and
• vigilance during tunnelling • Confined space of tunnel
environment (limited • access, escape, air quality control) • Difficulty in communications (sound
and signal • barriers) • Work in compressed air (soft ground)
Emergencies• Ground collapse (need we
say more?) • Support failure • Flooding • Gas explosion • Oxygen deficiency • Fire (encountering
inflammable gas) • Accidents : moving plants • Plant and power failure • Stoppages
Blasting Issues• Falling from heights or falling
on level (tripping/slipping) • Materials falling from height
or from stacks or vehicles • Burial by fall of material
(rock collapse or stacking collapse)
• Flooding or inrush of water • Machinery related (cranes,
excavators, etc)
• Vehicles (excavators, dump trucks)
• Electrical installations • Fire and explosions (gas
and explosives) • Air pollution (oxygen
deficiency, toxic fumes & radon gas)
Blasting
• Blasting a “way of life” in hard rock tunnelling
• Fly rock • Airblast and ground
shock • Toxic fumes • Accidental explosions
Charging
• Shot firer will check final charged face before leaving
Charging
• Signs to warn and cordon off personnel from charged face
Pre Blasting• Responsibilities of Shot-
firer• – Connecting the explosive
charges • – Final checking before
blasting • – Work with Tunnel
Foremen & Safety Supervisor to ensure adequate safety measures are taken.
Pre Blasting
• Safety vehicle will clear tunnel pre blasting
Pre Blasting
• Ample warning (E.g. sirens) outside the caverns
Blasting
Flying rock and airblast
Blasting
Use of rubber-tire mats and concrete blocks to minimize rock throw during blasting open areas
Blasting• keep away from area • switch off ventilation completely
before firing • switch on ventilation at full
capacity after blasting • evacuate team or provide
shelter(containers or niches)
Misfires• Should there be no initiation
of explosives, minimum • re-entry time must not be
less than 30 mins. • – After initiation, minimum
retry time must not be less than 15mins (after ventilation)
• – Blast inspection team shall enter tunnel with appropriate breathing apparatus.
Explosives Storage• Licensed magazine to store
detonators and booster charges in temp cavern on site
• Reduced transport hazards to public
• Guards may be necessary
Explosives Storage
• Mechanized charging minimizes human exposure at drilling face
After Blasting
• Ventilation • Gas/dust monitoring • Minimum entry time
after blasting (with ventilation)
Radon• Naturally occurring in rock
and soil • Radon and radon daughters
are radioactive and can cause adverse health effects (lung cancer)
• Is released by exposed surface, blasted rock, groundwater, from outside air
• Conditions improve with proper ventilation
Mucking Out• Hazards• Being struck or crushed • Falling Material • Dust and Noise • Tripping and falling
• Protection • Do not enter into loading area • Keep running surface in good
condition • Do not overload dumper • Good lighting in work area
Scaling• Hazards • Rock fall • Collapse as result from
instability of exposed rock surface
• Protection • Use machine for rock scaling • Do not enter danger zone
before scaling is completed • Lighting adequately
Manual Scaling• Hazards • Rock fall • Falling from heights • Being crushed
• Protection • Only work from a safe
area • Use working platforms • Light the area adequately
Rock Supports
• The Boomer E2 C drilling out rock support in Argentina
Rock Bolts
• Hazards • Falling from heights • Noise Protection • Use working platforms • Use eye and hearing protection
Shotcreting
• Hazards • Falling from heights • Rebound & dust • Chemical additives Protection • Use working baskets • Use protective clothing • Use shotcrete robot where possible • Wear protective hardhat for
shotcreting • Wear respiratory protection
Shotcreting Robots
• Hazards • Being crushed • Rebound & dust • Burst of concrete hose
• Protection • Do not enter danger zone • Separation distance between nozzle
& wall • Wear shotcrete protective helmet • Wear respiratory protection • Wet mix with alkali free additive to
reduce dust & air pollution
Monitoring
• An essential element of managing and controlling those risks is Monitoring and Observation during all stages of tunnel construction
2013• Sunol CA• On August 22, 2013, Employee
#1, was working on a pipeline project.
• A piece of cement grout approximately 1.5 feet by 1.5 feet by 6 feet long fell out of the tunnel face approximately 3 feet above the invert.
• The cement pinned Employee #1's leg against a roadheader.
• Employee #1 sustained bruising/contusions/abrasions.
2013• On June 17, 2013, an employee was working as a heavy equipment
mechanic for a bridge, tunnel, and highway construction firm. • He was on a segment build deck, assembling a tunnel boring machine. • He fell off the deck, falling a distance of 10 feet.
He sustained a strain or sprain in his left ankle
2012
• Boulder City NV• On June 11, 2012, Employee #1was
part of a swing shift crew excavating a tunnel.
• The TBM had been excavating in closed mode
• Closed mode excavation involves the pressurization of the cutterhead and face of the TBM to support the ground and/or control excessive groundwater inflows.
• The position of the TBM found it excavating through a large vertical fault zone that later became the Detachment Fault.
• The grout being injected in the annular space was being pumped in at approximately 14 bars.
• The swing shift had begun work and was preparing to erect a ring segment set; Ring #135.
• The first segment was successfully installed in the tunnel crown (top of the tunnel).
• The crew then began to install the second segment, which was to be placed in front of the keystone of Ring #134.
• Three hydraulic rams, including one abutting the keystone of Ring #134, were slowly retracted.
• Almost as soon as the retraction began, a loud pop was heard.
• The keystone for Ring #134 had shifted forward approximately 4 inches.
• The come-a-long did not hold the forces exerted, and the gears were stripped out.
• This shift permitted grout and other materials such as rocks to escape the annulus at a pressure of approximately 14 bars (200 psi).
• Employee #1 was standing in front of the area where the gap developed.
• He was struck and killed by the moving grout and rocks
TBM Closed Mode
2011• Webster NY• Employee #1, a locomotive
operator, was moving muck buckets and equipment to the head section of a tunnel.
• When the operator reached the end of the tunnel, the locomotive failed to stop and Employee #1 was crushed between the locomotive and the conveyor on the tunnel boring machine.
• Employee #1 was killed.
2011• Woodland CA• Employee #2, a laborer, noticed a hole
in a material chute in the No. 196 tunnel conveyor system.
• Employee #1 was joined by Employee #2 in the reclaim tunnel to schedule and plan a repair operation.
• As the two Employees exited the tunnel and walked away from the overhead No. 196 Conveyor, a 10 pound rock fell off the conveyor striking Employee #1 in the head and Employee #2 in the back, knocking both employees to the ground.
• Employee #1 was knocked unconscious and landed on top of Employee #2.
2009• Kermit, WV • Employee #1 was engaged in the
preparations for raising the height of a tunnel liner.
• Employee #1 bored several holes for taking core samples and pictures were taken.
• Employee #1 entered the tunnel through the west portal entrance, with his excavator equipped with a hoe ram.
• After reaching the necessary work station, Employee #1 began hammering out the center part of the tunnel's liner to remove it.
• About 30 minutes following the start of work, a section of the roof fell, crushing and killing Employee #1.
2009• Alexandria VA• Employee #1 was working in a
subway tunnel for the Washington Metropolitan Area Transit Authority.
• A train passed by the location where Employee #1 was standing.
• Coworkers reported that they heard a noise and then the train stopped.
• When the coworkers found Employee #1, it was apparent that he had been struck by the train and suffered trauma to his head and one leg.
2009• Cartersville GA• Employee #1 was packing straw
around the east end of the tunnel plate.
• The top, unprotected end of the tunnel collapsed and buried Employee #1's head and neck in mud on top of the tunnel plate.
• Coworkers attempted to rescue Employee #1; however, they were unsuccessful and he was pronounced dead at the site.
2008• Employees #1 though #5, were repairing the floor of the south bypass conduit water tunnel located under Lake Las Vegas in Henderson, Nevada.
• The tunnel was two miles long and seven feet in diameter.
• They were preparing to pour concrete on the tunnel floor.
• Two workers activated the ventilation fan from outside.
• Concrete was carried in eight buggy carts pulled by bobcat.
• Behind them, the mechanic and Project Superintendent followed on a propane-operated golf cart.
• Around 10:00 a.m., these employees arrived at the work location and found that the mechanical ventilation fan had been shut down.
• Several unsuccessful attempts were made to start the fan.
• The Project Superintendent and foreman decided that work would continue, after measuring the natural air flow using a handheld Mini Thermo-Anemometer by Extech Instrument.
• At 11:15 a.m., the foreman radioed from inside tunnel that employees were experiencing difficulty breathing, chest pains, and fatigue.
• The project superintendent sent golf carts and removed all employees from the tunnel about 12:16 p.m.
• Employees #1 through #5 were treated for asphyxia and carbon monoxide poisoning at University Medical Center (UMC) in Las Vegas and St. Rose De Lima in Henderson
2007• Houston TX• Employee and five coworkers were
working attempting to install a 60-in. by 10-ft by 0.5-in. steel pipe casing for the 42-in. regional main water line.
• The site was comprised of a 60-ft by 40-ft shaft which led down to a tunnel, which had already pushed the 60-in. steel pipe approximately 120-130-ft laterally under the Cypress Creek.
• The employee was cleaning the excess dirt from the 60-in. pipe as the pipe was hydraulically pushed inside.
• A breach occurred, immediately filling the tunnel and the shaft with water.
• All of the coworkers were able to escape except the employee.
2005• Minneapolis MN• At approximately 7:00 a.m. on
September 6, 2005, Employee #1 entered the work area on the fifth floor of the project.
• Employee #1 was walking through tunnel forms to prepare the forms for a concrete pour.
• As Employee #1 walked toward the end of the form inspecting his work, he stepped through a floor hole and fell approximately 45 ft to his death.
2000• Chanilly VA• The 27 ft deep passenger walkway
tunnel was being constructed from one terminal to another.
• At the time of the accident, about 700 ft of the approximately 40 ft wide by 16 ft tall tunnel had been excavated.
• Employee #1 was using a shotcrete hose to spray the side walls at the tunnel's earthen face when the top and side of the tunnel collapsed.
• Fire and emergency services were called but they were unable to rescue Employee #1.
1988• Milwaukee WI• Methane gas was detected in a 40-
foot-deep tunnel that was under construction.
• The mining machine was automatically shut down, and all the employees were evacuated.
• Ten minutes later, three employees entered the area to determine if the atmosphere in the tunnel was safe for reentry.
• An explosive mixture of methane gas had developed in the air.
• Apparently, the grout pump ignited the gas and caused an explosion.
• The three employees were badly burned, and they died of asphyxiation due to overexposure to carbon monoxide.
OSHA Specific Requirements
• Check-in/check-out. • The employer shall maintain a
check-in/check-out procedure that will ensure that above-ground 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 environmental controls are effective, and when the remaining construction activity will not cause any environmental hazard or structural failure within the facilities.
1926.800(c)
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:
• Air monitoring:• Ventilation:• Illumination:• Communications:• Flood control:• Mechanical equipment:• Personal protective equipment:• Explosives:• Fire prevention and protection: and• Emergency procedures, including evacuation
plans and check- in/check-out systems.
1926.800(d)
Emergency Provisions
• Hoisting capability. • When a shaft is used as a means of
egress, the employer shall make advance arrangements for power-assisted 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.
1926.800(g)(1)
Emergency Provisions
• 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.
1926.800(g)(2)
Emergency Provisions
• 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 that the counting function is encumbered.
1926.800(g)(3)
Emergency Provisions
• 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.
1926.800(g)(4)
Emergency Provisions
• Rescue teams. • 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.
1926.800(g)(5)(ii)
Hazardous Classifications
• Potentially gassy operations. • Underground construction operations shall
be classified as potentially gassy if either:• 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) to + or - 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
• 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.
1926.800(h)(1)
Air Quality and Monitoring.• 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 monitor, considering at least the following factors:
• Location of jobsite: Proximity to fuel tanks, sewers, gas lines, old landfills, coal deposits, and swamps;
• Geology: • History: Presence of air contaminants in
nearby jobsites, changes in levels of substances monitored on the prior shift; and
• 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.
1926.800(j)(1)(i)(B)
Air Quality and Monitoring.
• 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 1926.33 of this chapter.
• All other air quality test records shall be retained until completion of the project.
1926.800(j)(3)
Ventilation• 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.
• 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.
• A minimum of 200 cubic feet of fresh air per minute shall be supplied for each employee underground.
1926.800(k)(1)
Fire Control
• Flammable or combustible materials shall not be stored above ground within 100 feet (30.48m) 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:
• They are located as far as practicable from the opening; and
• 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.
1926.800(m)(7)
Fire Control
• 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.
1926.800(m)(9)
Portal Areas
• Competent persons conducting such inspections shall be protected from loose ground by location, ground support or equivalent means
1926.800(o)(3)
Portal Areas
• Suitable protection shall be provided for employees exposed to the hazard of loose ground while installing ground support systems.
1926.800(o)(3)
OSHA Citations
• Fall Protection
OSHA Citations
• Fall Protection
OSHA Citations
• Ladder
OSHA Citations
• Unapproved rigging
OSHA Citations
• Ladder
OSHA Citations
• Fall Protection
OSHA Citations
• Lighting
OSHA Citations
• Fall
OSHA Citations
• Rigging • no capacity marked
OSHA Citations
• GHS• Spill Control
OSHA Citations
• Fall
OSHA Citations
• Homemade drum carrier
