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Knowledge

Safety Training

TrenchTech offers a complete review of OSHA construction training requirements with special emphasis on excavation training requirements. TrenchTech's Safety Training is available as a special program, conducted upon request. Training is available in the following areas.

OSHA requires any job site where trench shoring is being installed or removed to be monitored by a competent person. This person should be familiar with the requirements of the OSHA standard 1926 subpart P (Excavations).

TrenchTech, Inc. provides a comprehensive competent person awareness course consisting of classroom instruction as well as hands-on experience for all attendees.

The course consists of instruction in the following areas:

Soil Classification

  • Classify the soil based on its properties and site conditions, utilizing visual and manual tests.
  • Classify the soil as stable rock Type A, Type B, Type C-60, or Type C.
  • Demonstrate manual testing methods, including pocket penetrometer, shear torvane, thumb penetration test, and more.

Soil Mechanics:

  • Learn to identify existing and predictable conditions that may affect the stability of the excavation.
  • Stress the importance of locating underground utilities and installations.
  • Review methods for protecting and supporting underground utilities and installations.
  • Cover the methods and requirements for contacting all utility companies before proceeding with excavation work.
  • Factors such as weather, moisture, surcharge loads, and other possible influences on the excavation will be discussed.

Requirements of the Standard:

  • Emphasis on becoming familiar with CFR-1926 subpart P, the OSHA standard pertaining to excavation safety.
  • Attendees with be familiarized with:
    • Scope and application
    • General requirements
    • All definitions
  • Subject matter to consist of, but not limited to:
    • Access and egress
    • Hazardous atmospheres
    • Stairways, ramps and ladders
    • Protection from vehicular traffic
  • Options for Shoring Excavations
    • Shielding
    • Shoring
    • Sloping
    • Timbers

OSHA Requirements

  • OSHA 29 CFR Part 1926.650 - .652 Subpart P-Excavations
  • OSHA's excavation standard contains many different requirements as well as several appendices that can be confusing at first glance. The following information summarizes the main requirements to help contractors prepare the job site for OSHA inspections.
  • Prior to digging, the contractor shall locate and identify all underground utilities such as sewer, telephone, fuel, electric, water lines, etc. that may be encountered during the excavation.
  • The contractor must designate a competent or qualified person to assess the excavation and determine that it is safe for project personnel to enter and work.
  • All surface encumbrances such as signs, trees, fences, poles, sidewalks, etc. that create a hazard to employees must be removed or supported during the excavation.
  • All excavating must maintain a minimum of 10 ft. from overhead power lines rated 50 kV or less, with 0.4 in. of clearance added for every kV over 50.
  • Support systems shall be provided to ensure the stability of adjacent structures endangered by excavation operations.
  • If excavation is over 5 ft. deep, a protective system such as trench shield shall be used to prevent a cave-in.
  • The contractor must provide a safe means of entering or exiting any excavation over 4 ft. deep.
  • A means of egress from a trench such as a ladder, ramp, or stairway shall be located within 25 ft. of workers.
  • In excavations over 4 ft. in depth, the potential for the accumulation of hazardous gases or vapors must be realized.
  • Shielding systems shall be installed and removed in a manner that protects employees from cave-ins, structural collapses, or from being struck by members of the support system.
  • Shielding systems shall be installed in a manner to restrict lateral or other hazardous movement of the shield in the event of a sudden collapse.
  • The bottom of the shielding system can not be positioned higher than 2 ft. above the bottom of the excavation.
  • Shielding systems and their components shall not be subjected to loads which they are not designed to withstand.
  • Shielding systems and their components shall be securely connected to prevent predictable failures.
  • The removed spoil shall not be stockpiled closer than 2 ft. from the excavation's edge.
  • Backfilling shall progress together with the removal of support systems from the excavations.
  • Any excavation left unattended must be barricaded, fenced or otherwise protected against accidental entry by pedestrians.
  • Employees exposed to vehicular traffic must wear high-visibility vests, and the excavation must be protected from traffic.
  • If employees must cross over an open excavation, a safe means of getting across the trench must be provided so that the employees do not have to jump.
  • No workers shall enter or work in excavations where standing water is visible unless adequate protection is used.
  • No employee shall be permitted underneath loads handled by lifting or digging equipment.
  • If the competent person finds evidence of a hazardous situation that may result in a cave-in, protective system failure, a hazardous atmosphere, or other hazardous conditions; exposed employees shall be removed from the hazardous area until the necessary precautions have been taken to ensure safety.

Compare Shoring Methods

Sloping

  • Time consuming
  • Damaging to surroundings
  • Increases costs due to additional backfilling and compaction time, replacement
  • Danger of collapse

Timbers

  • Extremely time consuming
  • Labor intensive
  • Limited reuse of materials
  • Fluctuating timber prices
  • Men may have to get into trench before secure

Lagging/Steel Sheeting

  • Time consuming
  • Labor and machine intensive
  • High material cost
  • Most expensive shoring method per sq. ft.

Shielding (Trench Boxes)

  • Pulled along through trench for increased productivity
  • Stackable for deep cuts
  • Many sizes available for various applications
  • Heavy duty steel construction

Shoring (Aluminum Hydraulics)

  • Extremely fast, efficient method
  • Excellent tool in stable soils
  • Few shores can accommodate many applications
  • Extensions can be field installed to increase sizes

Let TrenchTech Help You Prevent Cost Over Runs on Utility Jobs.
Items having high potential for cost over runs are:

  • Excessive excavation due to trench sloping
  • Trucking excavated material from the job site
  • Importing specified trench backfill material
  • Excessive crew "down time" due to waiting for bedding stone or repair of damaged existing utility
  • Roadway and lawn restoration
  • Pipe testing and leak repair
  • Documenting sewer and lead locations

Excessive Excavation Cuts into Profits
Unnecessary excavation due to sloping results in:

  • Higher trucking costs for removing excavated material
  • Higher cost of importing backfill
  • Higher street and lawn restoration
  • More excavator cycles per cut
  • Higher crew costs due to increased time of waiting for excavator to cut sloped trench
  • Lower pipe production
  • Possible liquidated damages due to inefficiency

The High Cost of Restoration

Street and lawn restoration costs for projects in cities and subdivisions can be higher than the cost of laying the pipe. The proper use of trench shields eliminates unnecessary excavation, reducing the damage to streets, lawns, sidewalks, and existing utilities.

Shoring Size Guide

How to Size Trench Shoring

The following information is useful for determining the proper trench shielding for your projects.

How to determine the depth of cut:

  • Slope must start 18" or 1.5' below the top of the shield.

How to determine the width of a trench shield:

  • Trench shield width is determined by O.D. of the pipe or the O.D. of the excavator bucket.
  • Allow 6" of clearance on each side of pipe bell.
  • Shield should be a minimum of 12" wider than the excavator bucket O.D.

How to determine the length of a trench shield:

  • Inside length clearance of pipe is approximately 2' less than the overall length of the shield.
  • Shield must be 2' to 4' longer than the pipe.

How to determine the machine life capacity:

  • 1.5 times the shield weight at 20' radius at grade.

Calculating Depth Ratings

  • PSF ratings and depths are based on short-term exposure with excavation open for 24 hours or less.

Lateral pressure per foot of depth:

  • 1200 / 25 = 48 ft.
  • 1200 / 45 = 27 ft.
  • 1200 / 60 = 20 ft.

Soil Definitions:

  • Apparent cohesion
  • Cemented soil
  • Layered soil
  • Plastic
  • Saturated soil
  • Submerged soil

No soil is Type A if:

  • It is fissured
  • It is subject to vibration
  • It has been previously disturbed
  • It is part of a sloped, layered system which dips into the excavation on a slope of 4 horizontal to 1 vertical [4H:1V] or greater
  • It is subject to other factors requiring classification as less stable.

Type B Soil:

  • Cohesive soil with unconfined compressive strength greater than .5 tsf but less than 1.5 tsf
  • Granular cohesionless soils, e.g., gravel, silt, silt loam, sandy loam
  • Type A fissured or subject to vibration
  • Unstable dry rock
  • It is part of a sloped, layered system which dips into the excavation on a slope less steep than [4H:1V], but only if the material would otherwise be classified as type B

Type C Soil:

  • Cohesive soils with unconfined compressive strength of 0.5 tsf or less
  • Granular soils including gravel, sand, and loamy sand
  • Submerged soil or soil from which water is freely seeping
  • Submerged rock that is not stable
  • It is part of a sloped, layered system which slopes into an excavation at an angle of 4H:1V or steeper

Pre-Excavation Checklist

Exposure to Falling Loads:
  • Are employees prohibited from standing underneath loads handled by lifting or digging equipment?
Protection of Employees from Loose Rock, Soil, or Equipment:
  • Are employees protected from falling rock, soil, or equipment by placing these materials a minimum of 2 ft. from the edge of the excavation or behind a retaining device?
Fall Protection:
  • Are standard guardrails provided on walkways and bridges that cross over 6 ft. and wider excavations?
    Are all excavations that are accessible to the public adequately barricaded or covered when unattended?
Inspections:
  • Are daily inspections of excavations being preformed by a competent person?
    Are inspections being performed by a competent person after every rainstorm or other hazard-increasing occurrence?
  • Are employees removed from the excavation if a competent person finds evidence of a situation that could result in a possible cave-in, protective system failure, hazardous atmosphere, or other hazardous conditions?
Shielding or Shoring:
  • Have all shielding, shoring, or other protective systems been designed by a registered professional engineer and accompanied by tabulated data from the manufacturer?
  • Are shielding, shoring, and other protective systems checked each day to detect movement and possible failure?
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