«Leaders Guide Trenching and Shoring Safety - Competent Person The manual for Excavations Trenching and Shoring is produced in Adobe Acrobat. The ...»
Trenching and Shoring Safety
- Competent Person
Trenching and Shoring Safety
- Competent Person
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Table of Contents What Makes a “Competent Person?”
The Competent Person Must:
CAVE-IN STORIES AND TRAGEDIES
Compliance Officer Protects Employees from Trench Collapse
Employees Removed from Excavation Site Minutes before Collapse
Far to Close for Comfort
Laguna Beach Man Killed in Trench Cave-In
OTHER CAUSES OF DEATHS
Surface Encumbrance Assessment –
Utility Locations –
Access and Egress
Manufacturer’s Tabulated Data
Examples of Safe Work Practices
Methods to Keep Equipment a Safe Distance from the Edge of an Excavation
Oxygen deficient atmospheres:
Examples of Confined Spaces
Conditions for a Confined Space
Confined Space Defined
Daily Minimum Inspections
TRENCHING AND EXCAVATION COMPETENT PERSON CHECKLIST
Excavation Safety: Daily Inspection Checklist
Four Soil Types as Defined by OSHA
TYPE A SOILS
TYPE B SOILS
TYPE C SOILS
Layered Geological Strata
Water Content of Soil
Weight of Soil
Previously Disturbed Soil
Thumb Penetration Test:
Using the Penetrometer:
Sedimentation or Olive Jar Test:
List of Figures Figure 1 Graphic of Ladder for Access and Egress of Trenches
Figure 2 Examples of Flagging Instructions
Figure 3 Manufacturer's Tabulated Data for Shoring Equipment
Figure 4 Construction Equipment
Figure 5 Barricade for Keeping Construction Equipment a Safe Distance from Trenches........... 30 Figure 6 Examples of Handheld Air Monitoring Instruments
Figure 7 Water Removal Pump
Figure 8 Walkway equipped with standard guardrails to allow employees to cross excavations or trenches
Figure 9 Diagram Illustrating Tension Cracks
Figure 10 Graphic Illustration Sliding or Sluffing
Figure 11 Graphic Illustrating Toppling
Figure 12 Graphic Illustrating Subsidence and Bulging
Figure 13 Graphic Illustrating Heaving or Squeezing
Figure 14 Graphic Illustrating Boiling
Figure 15 Pocket Penetrometer
Figure 16 Diagram Illustrating Sloping and Benching with the Four Types of Soils
Figure 17 Diagram Illustrating Simple Slope Type A
Figure 18 Diagram Illustrating Benching
Figure 19 Diagram Illustrating a combination of Sloping and Benching
Figure 20 Diagram Illustrating a Simple Slope in Type C Soil
Figure 21 Components of a Shoring System Illustrating Sheeting, Posts, Wales, and Struts........ 58 Figure 22 Illustration of Timbers being used as Typical Shores
Figure 23 Illustrations of Aluminum Hydraulic Shoring
Figure 24 Illustration of a Screw Jack
Figure 25 Diagram of a Trench Shield
List of Tables Table 1 More Examples of Confined Spaces
Table 2 Competent Person Checklist for Trenching and Shoring
Table 3 Evacuation Safety: Daily Inspection Checklist
Table 4 Soil Categories for Strength Characteristics, Physical Makeup and Maximum Allowable Slopt.... 53 Table 5 Maximum Allowable Slopes
ADJACENT STRUCTURE STABILITY refers to the stability of the foundation(s) of adjacent structures whose location may create surcharges, changes in soil conditions, or other disruptions that have the potential to extend into the failure zone of the excavation or trench.
COMPETENT PERSON is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate or control these hazards and conditions.
CONFINED SPACE is a space that, by design and/or configuration, has limited openings for entry and exit, unfavorable natural ventilation, may contain or produce hazardous substances, and is not intended for continuous employee occupancy.
EXCAVATION An Excavation is any man-made cut, cavity, trench, or depression in an earth surface that is formed by earth removal. A Trench is a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth of a trench is greater than its width, and the width (measured at the bottom) is not greater than 15 ft (4.6 m). If a form or other structure installed or constructed in an excavation reduces the distance between the form and the side of the excavation to 15 ft (4.6 m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.
HAZARDOUS ATMOSPHERE is an atmosphere that by reason of being explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen-deficient, toxic, or otherwise harmful may cause death, illness, or injury to persons exposed to it.
INGRESS AND EGRESS mean "entry" and "exit," respectively. In trenching and excavation operations, they refer to the provision of safe means for employees to enter or exit an excavation or trench.
PROTECTIVE SYSTEM refers to a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, and from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.
REGISTERED PROFESSIONAL ENGINEER is a person who is registered as a professional engineer in the state where the work is to be performed. However, a professional engineer who is registered in any state is deemed to be a "registered professional engineer" within the meaning of Subpart P when approving designs for "manufactured protective systems" or "tabulated data" to be used in interstate commerce.
SUPPORT SYSTEM refers to structures such as underpinning, bracing, and shoring that provide support to an adjacent structure or underground installation or to the sides of an excavation or trench.
SUBSURFACE ENCUMBRANCES include underground utilities, foundations, streams, water tables, transformer vaults, and geological anomalies.
SURCHARGE means an excessive vertical load or weight caused by spoil, overburden, vehicles, equipment, or activities that may affect trench stability.
TABULATED DATA are tables and charts approved by a registered professional engineer and used to design and construct a protective system.
TRENCH A trench refers to a narrow excavation made below the surface of the ground in which the depth is greater than the widthand the width does not exceed 15 feet. Trenching is common in construction and utility work, where underground piping or cables are being installed or repaired.
UNDERGROUND INSTALLATIONS include, but are not limited to, utilities (sewer, telephone, fuel, electric, water, and other product lines), tunnels, shafts, vaults, foundations, and other underground fixtures or equipment that may be encountered during excavation or trenching work.
UNCONFINED COMPRESSIVE STRENGTH is the load per unit area at which soil will fail in compression. This measure can be determined by laboratory testing, or it can be estimated in the field using a pocket penetrometer, by thumb penetration tests, or by other methods.
CEMENTED SOIL Cemented soil. A soil in which the particles are held together by a chemical agent, such a calcium carbonate, such that a hand-size sample cannot be crushed into powder or individual soil particles by finger pressure.
COHESIVE SOIL Clay (fine grained soil), or soil with a high clay content, which has cohesive strength. Cohesive soil does not crumble, can be excavated with vertical side slopes, and is plastic when moist. Cohesive soil is hard to break up when dry, and exhibits significant cohesion when submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay and organic clay.
DRY SOIL Dry soil. Soil that does not exhibit visible signs of moisture content.
FISSURED. A soil material that has a tendency to break along definite planes of fracture with little resistance, or a material that exhibits open cracks, such as tension cracks, in an exposed surface.
GRANULAR SOIL Gravel, sand, or silt (coarse grained soil) with little or no clay content. Granular soil has no cohesive strength.
Some moist granular soils exhibit apparent cohesion. Granular soil cannot be molded when moist and crumbles easily when dry.
LAYERED SYSTEM Layered system. Two or more distinctly different soil or rock types arranged in layers. Micaceous seams or weakened planes in rock or shale are considered layered.
MOIST SOIL. A condition in which a soil looks and feels damp.
Moist cohesive soil can easily be shaped into a ball and rolled into small diameter threads before crumbling. Moist granular soil that contains some cohesive material will exhibit signs of cohesion between particles.
PLASTIC A property of a soil which allows the soil to be deformed or molded without cracking, or appreciable volume change.
SATURATED SOIL A soil in which the voids are filled with water.
Saturation does not require flow. Saturation, or near saturation, is necessary for the proper use of instruments such as a pocket penetrometer or sheer vane.
SOIL CLASSIFICATION SYSTEM Soil classification system. A method of categorizing soil and rock deposits in a hierarchy of Stable Rock, Type A, Type B, and Type C, in decreasing order of stability. The categories are determined based on an analysis of the properties and performance characteristics of the deposits and the environmental conditions of exposure.
STABLE ROCK. Natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed.
SUBMERGED SOIL. Soil which is underwater or is free seeping.
TYPE A SOIL Cohesive soils with an unconfined, compressive strength of 1.5 ton per square foot (tsf) or greater. Examples of cohesive soils are: clay, silty clay, sandy clay, clay loam and, in some cases, silty clay loam and sandy clay loam. Cemented soils such as caliche and hardpan are also considered Type A. However,
no soil is Type A if:
(1) The soil is fissured; or (2) The soil is subject to vibration from heavy traffic, pile driving, or similar effects; or (3) The soil has been previously disturbed; or (4) The soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or (5) The material is subject to other factors that would require it to be classified as a less stable material.
TYPE B SOIL:
(1) Cohesive soil with an unconfined compressive strength greater than 0.5 tsf but less than 1.5 tsf; or (2) Granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and, in some cases, silty clay loam and sandy clay loam.
(3) Previously disturbed soils except those which would otherwise be classed as Type C soil.
(4) Soil that meets the unconfined compressive strength or cementation requirements for Type A, but is fissured or subject to vibration; or (5) Dry rock that is not stable; or (6) Material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical (4H:1V), but only if the material would otherwise be classified as Type B.
TYPE C SOIL:
(1) Cohesive soil with an unconfined compressive strength of 0.5 tsf or less; or (2) Granular soils including gravel, sand, and loamy sand; or (3) Submerged soil or soil from which water is freely seeping; or (4) Submerged rock that is not stable, or (5) Material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical (4H:1V) or steeper.
UNCONFINED COMPRESSIVE STRENGTH. The load per unit area at which a soil will fail in compression. It can be determined by laboratory testing, or estimated in the field using a pocket penetrometer, by thumb penetration tests, and other methods.
WET SOIL. Soil that contains significantly more moisture than moist soil, but in such a range of values that cohesive material will slump or begin to flow when vibrated. Granular material that would exhibit cohesive properties when moist will lose those cohesive properties when wet.
DEFINITIONS THAT ARE NO LONGER APPLICABLE. For avariety of reasons, several terms commonly used in the past are no
longer used in revised Subpart P. These include the following: