Subpart S Underground Construction, Caissons, Cofferdams,

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Subpart SUnderground Construction, Caissons,
Cofferdams, Compressed Air
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Provide and Maintain a safe means of access and
egress to all work stations
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Know the number of personnel underground at all
times
Access to underground sites is to be controlled.
(check in/check out)
1, 2, 3, 4,
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Underground Construction
Can you hear me now?
Can you hear me now?

• When natural unassisted voice communications are
  not feasible, use power assisted voice
  communications.

Huh!!
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Underground Construction

• Powered communications systems shall operate on
  an independent power supply and the disruption of
  function of one phone shall not impact others.

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Underground Construction

• At least one person must be on duty above ground
  when there is anyone working below ground.

At least 1 person topside
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Underground Construction

• If there is no emergency lighting system to
  provide adequate illumination for escape
  underground.

Darn
or
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Rescue Teams
Minimum of 5 persons on a rescue team
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If 25 or more workers are underground
The first rescue team should be able to be on
site within 30 minutes. The second rescue team
to be able to be on site within 2 hours.
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If less than 25 workers are underground
A 5-person rescue must be able to be on site
within 30 minutes.
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Underground Construction

• Maintain a fire watch when hot work is performed.

Collect lighters, matches and other ignition
sources
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Test the air underground
Oxygen Content between 19.5 and 22
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Underground Construction

• A competent person shall be responsible for air
  monitoring.
• Test for
• carbon monoxide,
• oxygen deficiency,
• methane,
• hydrogen sulfide.

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Underground Construction
200 cfm per worker
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How much diesel fuel can be stored underground?
Only enough to be consumed within 24 hours
Diesel Fuel
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Storage of Fuel Combustibles
100 feet
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How much fuel gas and oxygen cylinders can be
stored underground?
Only enough to be consumed within 24 hours
Cylinders
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Cars for hauling on over 1 grade
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Cars for hauling on over 1 grade
Restrain with a Safety Chain or other Connector
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Underground Construction

• A competent person shall determine the adequacy
  of rock bolts.

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Underground Construction

• Cofferdams shall have a means of controlled
  flooding to prevent damage from overtopping by
  high waters.

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Underground Construction
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Cut and Cover

• Alternate to conventional tunneling

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Underground Construction

• Pressure chambers shall have the pressure
  increased slowly for workers (3 psig the first
  minute). Then increase the pressure to 7 psig.
  The increase will be coupled with close
  monitoring of worker reaction (esp. discomfort)
  to the pressure. The practical limit for workers
  is 50 psig.

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Underground Construction

• Bulkheads - airtight structure separating the
  working chamber from free air or from another
  chamber under lesser pressure.

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Underground Construction

• Man lock - chamber through which workers pass to
  go from one air pressure to another.
• Working chamber - space under pressure in which
  work is performed.

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Underground Construction

• Depressurize - process of going from a
  pressurized area to one with a lower pressure.
• Decant - emergency procedure of removing a worker
  quickly from the work area to atmospheric
  pressure, placing them in a high pressure
  container.

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Underground Construction

• One atmosphere equals 14.7 psi
• Working under pressure causes changes in the
  blood stream. When returning to one atmosphere,
  do it slowly.

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Demolition

• When dropping materials more than 20 feet from
  the exterior of a building, use an enclosed chute
  (1926.252)
• On demolition sites it can be dropped through
  floor openings, but place guard rails out at
  least 6 feet back from the projected edge.

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Demolition

• Chutes at an angle of 45 degrees or steeper must
  be fully enclosed.
• Openings shall not exceed 48 inches in height and
  this opening must be closed when the chute is not
  being used.
• A bumper at the opening to the chute is needed to
  prevent wheelbarrows from falling in.

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Demolition

• Holes cut into the floor to dispose of materials
  shall not be larger than 25 percent of the total
  floor area.

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Demolition

• If a section of wall is not laterally braced, it
  cannot be higher than one story.
• All walls must be left in stable condition at the
  end of the day.

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Demolition

• When access to portions of a structure must be
  created, use no less than 2 thick materials and
  no narrower than 18

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Demolition

• Storage of waste materials on floors shall not
  exceed the design loads of the floors

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Demolition

• When steel and masonry is encountered, the
  masonry can be removed independent of the steel.
  If the steel structure is sound, the masonry
  removal can proceed downward.

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Blasting

• Blasters cannot be substance abusers
• Account for all explosives at all times

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Blasting
Stemming
Burden
Face
Toe
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Blasting

• Proper precautions must be taken when removing
  rock near overhead power lines

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Blasting

• Blasts shall be ignited with an electric blasting
  machine or properly designed electric power
  source.

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Blasting

• Buildings for mixing explosives shall be
  noncombustible or sheet metal on wood studs.
• Building floors are to be concrete or other
  nonabsorbent materials
• Fuel oil storage to be separate

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Blasting

• Tamp explosives only with wood rods or plastic
  tamping poles
• Tamp lightly

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Blasting

• No drilling once the explosives are in nearby
  holes
• Dont leave explosives unattended near the blast
  site

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Blasting

• Serial and Parallel Blasting

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Ladders

• Use a double wide if more than 25 workers will
  use the ladder for access.

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Ladders

• On long stairways use a landing every 12 feet.