Transcript Trenching_1.ppt

TRENCHING AND SHORING SAFETY
CORPORATE SAFETY TRAINING
29 CFR 1926.650-653
WELCOME
COURSE OBJECTIVES
 Introduce The Trenching & Shoring Safety Program
 Establish The Programs Role.
 Discuss the components of an effective program.
 Introduce ideas to help develop an effective program.
 Introduce Basic Skills in the Recognition & Control of
Trenching & Shoring Hazards.
APPLICABLE REGULATIONS
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29 CFR 1926.650
29 CFR 1926.651
29 CFR 1926.652
29 CFR 1926.653
- General Protection Requirements
- Specific Excavation Requirements
- Specific Trenching Requirements
- Definitions
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Appendix - A
Appendix - B
Appendix - C
Appendix - D
- Excavations
- Sloping and Benching
- Timber Shoring for Trenches
- Aluminum Hydraulic Shoring
BASIS FOR THE REGULATIONS
 Hundreds of workers killed annually from cave-ins
 Thousand of workers injured annually from cave-ins
 Fatality rate for trenching is twice the level for general
construction
PURPOSE OF THE PROGRAM
REASONS TO MAINTAIN AN EFFECTIVE PROGRAM:
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Peace of mind
Reduced liability
Increased productivity
Reduced lost man-hours
Improved employee morale
Reduced or eliminated fines
Improved health of employees
Reduced injury and illness rates
Lower workers’ compensation costs
Because it’s the right thing to do!!!!!!
MECHANISM OF DEATH
 Asphyxiation
 Each time a breath is exhaled the weight of the
load restricts inhalation of the next breath. Slow
suffocation usually follows unless rescue is
immediate.
DYNAMIC SITE CONDITIONS
 CAVE-INS RESULT FROM:
 Vibrations
 Adjacent Structures
 Freezing and Thawing
 The Weight of the Soil Itself
 Addition or Removal of Water
 Reduction in Frictional and Cohesive Capacities of Soil
HOW MUCH DOES SOIL WEIGH?
DEPENDING ON THE DENSITY AND WATER CONTENT:
 One cubic yard weighs
- 3000lbs or more
 One cubic foot weighs
- 100lbs or more
3 FEET
1 FOOT
3000lbs or more
100lbs or more
HOW DO MOST DEATHS OCCUR?
 Instantaneously
 Trenches 5 to 15 deep
 With absolutely no warning
 In seemingly safe conditions
 With workers in a bent or lying position
SITE EVALUATION
BEFORE YOU BEGIN EXCAVATION:
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The site must be assessed
Potential hazards must be determined
Known hazards reduced or eliminated
Emergency procedures established
Periodic inspection intervals determined
Utility locations must be staked or marked
BASIC SAFETY REQUIREMENTS
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Conduct inspections before each work shift
Do not travel under elevated loads
Do not work over unprotected employees
Wear proper personal protective equipment
Provide walkways or bridges over trenches
Provide trench exits within 25 feet of workers in
trenches more than four feet deep
 Ensure spoilage is at least 2 ft. from trench edges
EMERGENCY PROCEDURES
 Immediately call 911, or the Emergency Response Team
 Report: - Exact Location
- Number of Victims
- Nature of Emergency
- Trench Measurements
- Special Hazards
 Keep all life-support and dewatering systems operating
 Clear workers away from the excavation
 Shut down heavy equipment
 Be prepared to meet and brief rescue personnel
EMERGENCY PROCEDURES
Continued
 What not to do: - Don’t Panic!
- Control would-be rescuers
- Don’t sacrifice anyone else
- Never attempt to dig someone out
using motorized equipment
 Remember - Your actions could save a life!
FOOT AND VEHICLE TRAFFIC
ACCIDENT PREVENTION METHODS:
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Warn and reroute public traffic
Post signs, barricades and flagmen
Mandate use of reflective vests
Warn site traffic with stoplogs etc.
Install protective supports systems
SURFACE ENCUMBRANCES
MUST BE:
 Removed
 Relocated
 Supported to protect site personnel
EXAMPLES INCLUDE:
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Fencing
Posts
Telephone
Cable
Electrical Access Boxes
UNDERGROUND INSTALLATIONS
 Utility lines must be located before excavating begins
 Utility companies or owners must be contacted:
-- Response times must be considered
-- Advised of the proposed work
-- Questioned concerning underground installations
need to be answered
UNDERGROUND INSTALLATIONS
Continued
 If no response is given within 24 hours* work can
cautiously proceed *(local timeframes may vary)
 Underground installations must be determined by
safe and acceptable means
 Excavated underground installations must be
protected
 Never under estimate hazards associated with
underground utilities!!!
ACCESS AND EGRESS
STRUCTURAL RAMPS:
 USED ONLY BY PEOPLE
 DESIGNED BY A “COMPETENT PERSON”
 EGRESS REQUIRED EVERY 25 FEET (LATERAL) > = 4FT
TRENCH SAFETY
TRENCHES MORE THAN 5 FEET:
 Require shoring
 Or must have a stabilized slope
IN HAZARDOUS SOIL CONDITIONS:
 Trenches under 5 feet need protection
HAZARDOUS ATMOSPHERES
 TESTING AND
CONTROLS:
 Oxygen deficiency
 Flammable
atmospheres
 Testing
 EMERGENCY RESCUE
EQUIPMENT:
 Availability
 Lifelines
BACK-UP
FALL PROTECTION
TIE-OFF POINT
WINCH
SAFELINE
TRIPOD
SAFELINE
HAZARDS & WATER ACCUMULATION
 Adequate Precautions Must Be Taken When
Working in Accumulated Water
 Controlling Water and Water Removal Must Be
Monitored by a Competent Person
 Ditches, Dikes or Comparable Means Should Be
Used to Prevent Surface Water From Entering
Excavations
WEATHER FACTORS
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Don’t under estimate the effects weather can have
Weather can have a drastic effect on the site
Daily (or hourly) site inspections must be made
Consider protection from:
 Lightning
 Flooding
 Erosion
 High winds
 Hot or Cold Temperatures
STABILITY OF ADJACENT STRUCTURES
 When stability is endangered
support systems must be used.
 Excavation below the base of a
foundation will not be permitted
when it poses a hazard except
when:
– A support system is provided
– The excavation is in stable rock
– A registered professional has approved the site or
deemed the situation will not pose a hazard
SITE INSPECTIONS
 Daily inspections must be made by a competent
person of:
 Excavations
 Adjacent areas
 Protective systems
 When evidence is found of a hazardous condition, the
exposed employees must be Immediately removed
from the area.
FALL PROTECTION
 Guardrails must be provided for crossing over
excavations
 Barriers must be provided for remotely located
excavations
SOIL CLASSIFICATION SYSTEM
 TYPE A SOILS
- Clay
- Silty Clay
- Sandy Clay
- Clay Loam
 TYPE B SOILS
- Granular Cohesionless Soils (Silt Loam)
 TYPE C SOILS
- Gravel
- Sand
- Loamy Sand
SOIL CLASSIFICATION SYSTEM
Continued
 SOIL CLASSIFICATION MUST BE DONE BY A
COMPETENT PERSON:
 VISUAL TEST
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Check entire worksite
Fissured ground
Layered soil
Disturbed earth
Seepage
Vibration
Poor drainage
A
B
C
SOIL CLASSIFICATION SYSTEM
Continued
 MANUAL TEST
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Plasticity
Dry Strength
Thumb penetration
Pocket penetrameter
Hand operated shear vane
A
B
C
 WARNING: One soil inspection and classification may not be
enough. Outside disturbances during excavation may change
even the best soil classification. Inspect the soil after any
change in conditions.
TYPE A SOILS
 Are cohesive soils with an unconfined,
compressive strength of 1.5 t/sf.
 Clues that soil is not type A:
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If it is fissured
If it is subject to vibration
If it has been previously disturbed
If the soil is part of a sloped, layered system
If the material is subject to other factors that would require
it to be classified as a less than stable material
A
B
C
TYPE B SOILS
 Are cohesive soils with an unconfined
compressive strength greater than 0.5 t/sf
 Types include angular gravel, silt, silt loam,
sandy loam and silty clay loam
 Previously disturbed soils except those
which would be classified as type C
 Dry rock that is not stable
A
B
C
TYPE C SOILS
 Are cohesive soil with an unconfined
compressive strength of .5 t/sf
 Are granular soils including gravel, sand, and
loamy sand
 Submerged soil or soil from which water is
seeping
 Submerged rock that is not stable
A
B
C
REQUIREMENTS FOR PROTECTIVE
SYSTEMS
 Each employee must be protected from cave-ins
by an adequately designed system. Exceptions
are:
Excavations made in stable rock
Excavations less than 5 feet
 Protective systems must have the capacity to
resist all loads that are expected to be applied to
the system
REQUIREMENTS FOR PROTECTIVE
SYSTEMS Continued
 DESIGN OF BENCHING AND SLOPING SYSTEMS:
– OPTION 1 - Allowable configurations and slopes
– OPTION 2 - Determination of slopes and configurations
using 29 CFR 1926.652
– OPTION 3 - Designs using other tabulated data
– OPTION 4 - Design by a registered professional engineer
MATERIALS AND EQUIPMENT
 Must be free from damage or defects that might
impair proper function
 Must be used and maintained in a manner that is
consistent with the recommendations of the
manufacturer
 Must be examined by a competent person if damage
occurs
INSTALLATION AND REMOVAL
OF SUPPORT
 GENERAL REQUIREMENTS
 Support systems must be securely connected
 Support systems must be installed and removed in a
manner that protects from collapse
 Support systems must not be subjected to loads
exceeding design specifications
INSTALLATION AND REMOVAL
OF SUPPORT Continued
 GENERAL REQUIREMENTS
 Additional precautions must be taken to ensure safety
before temporary removal begins
 Removal must begin at the bottom of the excavation
 Backfilling must progress together with the removal of
support systems from excavations
SLOPING AND BENCHING SYSTEMS
 EMPLOYEES MUST NOT BE PERMITTED TO WORK:
 On the faces of sloped or benched excavations
 At levels above other employees except when
employees at the lower levels are adequately
protected from the hazard of falling, rolling or sliding
material or equipment
SLOPING AND BENCHING SYSTEMS
Continued
 TEMPORARY SPOIL PILES:
2 FEET MINIMUM
SLOPING AND BENCHING SYSTEMS
Continued
 SLOPING GENERAL REQUIREMENTS
 Various slope angles are allowed by OSHA
 Appendix B to 1926 Subpart P must be consulted
 Evacuate the excavation if walls show signs of distress
 If soil conditions change, re-inspect.
SLOPING AND BENCHING SYSTEMS
Continued
 BENCHING GENERAL REQUIREMENTS
 Various slope angles are allowed by OSHA
 Appendix B to 1926 Subpart P must be consulted
 Evacuate the excavation if walls show signs of distress
 If soil conditions change, re-inspect.
SLOPING AND BENCHING SYSTEMS
Continued
90 Degrees
53 Degrees
Maximum
STABLE ROCK
TYPE A
45 Degrees
Maximum
34 Degrees
Maximum
TYPE B
TYPE C
BENCHING EXAMPLE
TYPE A SOILS
20
FEET
MAX
1
3/4
SLOPING EXAMPLE
TYPE B SOILS
20
FEET
MAX
1
1
SHORING SYSTEMS
JACKS/CROSSBRACES
SHEETING
WALES
SHORING
SYSTEMS
Continued
 GENERAL
 Shoring provides a framework to work in
 Shoring uses wales crossbraces and uprights
 Shoring supports excavation walls
 OSHA TABLES PROVIDE SHORING DATA
 Soil type must be known
 Depth and width of the excavation must be known
 You must be familiar with the OSHA Tables
SHORING
SYSTEMS
Continued
 REMOVAL
 Remove shoring from the bottom up
 Pull sheeting out from above
 Backfill immediately after removal of support system
JACKS/CROSSBRACES
SHEETING
WALES
SHORING
SYSTEMS
Continued
PNEUMATIC/
HYDRAULIC
JACKS
SCREW
JACK
SHIELD SYSTEMS
 GENERAL
 Shield systems must project at least 18 inches above the
lowest point where the excavation face begins to slope
At Least 18 Inches
SHIELD SYSTEMS
Continued
 GENERAL
 Shield systems must not be subjected to loads exceeding
those which the system was designed to withstand
 Shields must be installed to restrict hazardous movement
 Employees must be protected from the hazard of cave-ins
when entering or exiting the areas protected by shields
 Employees must not be allowed in shields when shields are
being installed, removed, or moved vertically
SHIELD SYSTEMS
Continued
COMMON TRENCH SHIELD
SHIELD SYSTEMS
Continued
 Systems may be connected
 Systems may be stacked
 Configuration must by consistent
with the recommendations of the
manufacturer
 Must be examined by a competent
person if damage occurs
TIPS FOR USING CONTRACTORS
 REMEMBER, YOU CONTROL YOUR SITE!
 REVIEW THEIR PROCEDURES WITH THEM BEFORE
STARTING THE JOB!
 DETERMINE THEIR SAFETY PERFORMANCE RECORD!
 DETERMINE WHO IS IN CHARGE OF THEIR PEOPLE!
 DETERMINE HOW THEY WILL AFFECT YOUR EMPLOYEES!