A mobile (rolling) scaffold is mounted on casters.
It is constructed of a tubular-metal section of
scaffolding or is made of components. designed
specifically for a particular purpose (fig. 4-31).
The following are safety rules that pertain to
Inspect all equipment before use.
Inspect erected scaffolds regularly to ensure they
are being maintained in a safe condition.
Provide adequate sills for scaffold posts and use
Plumb and level scaffolds as erection proceeds,
so the branches fit without having to be forced.
Fasten all braces securely.
Use and install scaffolding accessories
according to the procedure recommended by the
manufacturer. Do not alter accessories in the
Do not ride on rolling scaffolds.
Remove all types of material and items of
equipment from the platform before attempting
to move a scaffold.
Figure 4-31.Aluminum ladder scaffold.
Q16. Banks or sides of a trench of what height must be
shored or sloped?
LEARNING OBJECTIVE: Understand
wastewater component application and
wastewater system installation.
A wastewater system is a group of sewer pipes and
pumps designed to convey domestic and industrial
wastes and to transport them to a wastewater treatment
plant (fig. 4-32). The wastewater system starts in a
house or building that conveys wastewater, known as
a house sewer, into a lateral sewer pipe. The sewer
main receives wastes from two or more laterals. The
trunk sewer is a large pipe that receives the flow from
laterals and mains. When gravity flow is no longer
practical or possible, a lift station is used to pump
wastewater to a higher level. A forced main (pressure
main) carries the discharge from the lift station to the
main or trunk sewer. From here, the wastewater flows
by gravity to an interceptor sewer, connecting into the
wastewater treatment plant. An outfall sewer is a pipe
that carries the treatment plant effluent to the point of
A wastewater system safeguards the public health
by preventing communicable diseases from getting
into groundwater or drinking water systems. The
wastewater system carries the raw wastewater to the
treatment plant quickly for treatment. The wastewater
system should only be carrying domestic and
industrial wastes. Infiltration (leakage or seepage of
water from a storm or groundwater into a sewer)
should be controlled to the lowest practical limit. Good
monitoring and maintenance are required to control
infiltration. Too much infiltration overloads both the
wastewater system and the treatment plant. The end
result is not enough detention time and a washout of
As a Utilitiesman, you may be involved in
construction of a wastewater system and in
maintenance, repair, or minor replacement of sewers.
The joints and seals used for each type and size of pipe
are important. Leaks and breaks often occur at the
joints; therefore, with fewer joints and proper seals,
leaks can be reduced. The pipe chosen for the
wastewater system should be based on the type of
waste, the kind of soil, the estimated flow, and the
weight of the backfill.