Page 32 - Trench and Excavation

Important Trench Numbers

15 inches - Minimum trench width where fall protection on a crossover bridge would be
required. Trench required to be 6 feet deep or more
18 inches - Support or shield system must extend at least 18 inches above the toe of a sloped
system
18 inches - Maximum distance from top hydraulic cylinder to top of the trench in a vertical
aluminum shoring system
2 feet - Maximum depth that an excavation can extend below the protective system (if the
system is designed for the entire depth)
2 feet - Recommended minimum distance between the floor of the trench and the
groundwater table
2 feet - Minimum width between forms and excavation wall for residential foundation
excavation to be exempted from Trenching Regulations
2 feet - Surcharge loads must be kept at least 2 feet from the edge of the trench
2 feet - Maximum distance between floor of the trench and the bottom of an aluminum
upright in a vertical aluminum shoring system
2 feet - Maximum distance between the upper aluminum waler and the top of the trench in
a horizontal aluminum shoring system
2 feet - When vertical spacing of cross-braces is 4 feet, place the to cross-brace no more
than 2 feet from the top of the trench
2.5 feet - When vertical spacing of cross-braces is 5 feet, place the to cross-brace no more
than 2.5 feet from the top of the trench
2.5 feet - Maximum distance between bottom cross-brace and trench floor if uprights are not
imbedded or a mudsill is not used
3 feet - Maximum distance between bottom cross-brace and trench floor if uprights are
imbedded
3 feet - Ladders must extend at least 3 feet above the top of the trench
3.5 feet - Maximum distance between bottom cross-brace and trench floor if a mudsill is
used
3.5 feet - All excavations 8 feet or less in depth in TYPE A soil which have unsupported
vertically sided lower portions shall have a maximum vertical side of 3.5 feet and
a maximum allowable slope of 3/4H: 1V
3.5 feet - All excavations more than 8 feet, but less than 12 feet in depth in TYPE A soil
which have unsupported vertically sided lower portions shall have a maximum
vertical side of 3.5 feet and have a maximum allowable slope of 1H: 1H
4 feet - Trenches 4 or more feet are required to have a means of egress every 25 feet
4 feet - Trenches 4 feet or more must have atmosphere tested if a hazardous atmosphere
potential exists
4 feet - Maximum height of bottom step for benched systems for TYPE A Soil
4 feet - Maximum height of all benched steps in benched system for TYPE B Soils
4 feet - Maximum distance between the bottom hydraulic cylinder and the floor of the
trench in a vertical aluminum shoring system
4 feet - Maximum distance between the lower aluminum waler and the floor of the trench
in a horizontal aluminum shoring system
5 feet - Trenches 5 feet or more in depth must have protective system
5 feet - Maximum height of upper steps in benched system for TYPE A soil

Trench & Excavation
Competent Person Training P3 Safety Solutions LLC
Page 32