Page 5 - Trench and Excavation

Cohesion- Natural attractive force which holds soil particles together.

Cohesive Soil- A high clay-content soil which does not crumble, can be excavated with vertical
sides, is plastic when wet, and hard when dry, and exhibits high cohesion when saturated or
submerged.
Competent Person- A person who is capable of identifying existing and predictable hazards,
unsanitary conditions, or otherwise harmful conditions in and around an excavation. This person
also has the authority to take corrective action as required.

Confined Space- A space that meets the following criteria: 1) is large enough to enter and
perform assigned work, 2) have limited means of entry and exit, and 3) are not intended for
continuous human occupancy.
Cross-Brace- A horizontal member of a shoring system which extends perpendicularly from wall
to wall and applies compressive force against the trench walls.
Cutback Distance - Horizontal distance from the toe of the slope to the top of sloped trench wall.
Density - The weight of soil per unit of volume, usually in pounds per cubic foot.

Design- A plan, sketch, model, or calculation which communicates the components, shape, and
essence of the excavation plan.

Dike- A raised bank, or structure, designed to prevent the entrance of water.
Distress - A soil condition where a cave-in is imminent, or likely to occur.
Dry Soil- Soil which does not exhibit any visible signs of moisture content.

Egress- The way to get into and out of a trench.
Embankment - Those conditions in which the trench is so wide that the backfill does not affect
the pipe loading or where the trench is covered with fill to above the original ground level.

Entry Permit System- The employers written procedures for preparing and issuing permits for
entry and returning the permit space to service following termination of entry. This system also
designates the individuals who may authorize entry.
Excavation- Any man-made cut cavity, trench, or depression in the earth's surface formed by
earth removal.
Face- The wall of the trench.

Fine- Very small silt and clay particles that contaminate soil samples and change soil
characteristics.
Fissured Soil- Soil material which breaks along a definite plane with minimal effort or soil which
exhibits open cracks.
Granular Soil - Soil with little clay content and, therefore, little cohesive strength. It cannot be
molded when moist, and crumbles when dry. 65% of the particles are distinguishable with the
naked eye.
Gravel- Granular soil where at least one-half of the particles are greater than 2mm in diameter.
Hardpan- A hardened or cemented layer of soil at or below the surface which is impervious to
drainage. It may consist of a layer of clay or cemented material.
Hazardous Atmosphere- An atmosphere which by reason of being explosive, flammable
poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful, may cause
death, illness, or injury.

Trench & Excavation
Competent Person Training P3 Safety Solutions LLC
Page 5