2022 Manitoba Workplace Safety and Health Act and Regulation

26.15(3) Subsection (2) applies to frozen ground, but does not apply to apply
to an open excavation that is cut in solid rock or other equally stable
material.
26.15(4) An employer who requires or permits a worker to enter an open
excavation that has a depth of more than 3 m must ensure that
(a) a support structure or an alternative method for stabilizing the
walls has been designed and certified by a professional engineer
for the excavation; and
(b) as applicable, the support structure or alternative method is
constructed, installed, used, maintained and dismantled in
accordance with specifications provided by the professional
engineer.
26.15(5) An employer who is subject to subsection (4) must ensure that
(a) the professional engineer’s specifications for the support
structure or alternative method for stabilizing the walls specify
(i) its size and specifications, including the type and grade of
materials used in its construction, and
(ii) the loads and types of soil conditions for which it is
designed;
(b) the structure or alternative method is inspected and certified by
a professional engineer before a worker begins working in the
excavation.
M.R. 147/2010
Trenches
26.16(1) An employer who requires or permits a worker to enter a trench that
has a depth of 1.5 m or less must ensure that a support structure
is installed in it, but only if there is a danger of cave-in, collapse
or material sliding or rolling into the trench due to soil or work
conditions at the construction project site.

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Workplace Safety And Health Regulation
238
26.16(2) An employer who requires or permits a worker to enter a trench that
has a depth of more than 1.5 m but not more than 4.5 m must ensure
that
(a) shoring that is constructed of components that meet the
minimum requirements for the applicable soil conditions set out
in the Schedule to this Part is installed; or
(b) an alternative that is designed and certified by a professional
engineer is used for stabilizing the walls of the trench.