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538 Chapter 14 Design of Sewer Systems
training session on the use of air respirators since his employment began with the public
works department.
The employer did not ensure that the following sewer plug manufacturer’s recommen-
dations were adhered to during the installation of the plug: (a) The pipe be cleaned out
prior to insertion of the plug, (b) the plug be installed with a backup system (i.e., gate
valve), (c) the plug be anchored in place, and (d) the plug be checked to ensure proper in-
flation to 30 psi (208.2 kPa).
The National Institute for Occupational Safety and Health (NIOSH) investigator con-
cluded that, in order to prevent future similar occurrences, employers and employees must:

1. Follow sewer plug manufacturer recommendations on the installation and use of
inflatable sewer plugs.
2. Develop, implement, and enforce specific confined space entry procedures.
3. Ensure that appropriate rescue equipment is utilized during confined space entry.
4. Ensure that appropriate personal protective equipment is properly worn.
5. Consider installing self-priming wet well sewer pumps. Properly installed, a self-
priming sewer pump would prevent an air-lock whenever the wet well is manually
pumped out below the level of the pump intake. In this incident, if the pumps in the
sewage lift station had been self-priming, they could have been immediately acti-
vated, possibly preventing the fatality that resulted.

14.16.2 Sewer Worker Dies When Inflatable Sewer Plug Bursts in Washington, D.C.

A sewer maintenance worker died while working inside a sewer gate chamber. An inflatable
sewer plug downstream from the victim was overinflated and burst, allowing sewage to flood
the chamber. The worker was part of a 10-man sewer maintenance crew assigned to divert the
flow of sewage in a branched, 6-ft-diameter (1.83-m-diameter) sewer main. The crew lowered
an inflatable sewer plug into a diversion gate chamber and anchored it several feet into the right
leg of the sewer main. An air line, connected to an air compressor at the surface, was attached
to an air valve on the inflatable sewer plug. The victim, who was operating the compressor, left
it running unattended and entered the gate chamber to inspect the sewer plug. Within a few min-
utes the plug burst, forcing water and air into the chamber, fatally injuring the worker.
The rescue squad from the city emergency medical service (EMS) was notified and ar-
rived at the site in 5 minutes. After a 40-minute search, EMS personnel discovered the
body of the victim submerged under the sewage flow, against the bar screen of a sewage
pumping station approximately 200 yards (183 m) downstream from the gate chamber.
EMS personnel noted that the victim was dead at the scene.
The employer involved is a municipal utility with 1,100 public works employees.
Approximately 200 of the employees are sewer maintenance workers and wastewater treatment
plant operators. The victim had been employed by the municipality for 23 years as a sewer
maintenance worker. The public works department has a full-time safety and health manager
and a full-time safety and health specialist. A safety policy exists, but no confined space entry
procedures for sewer maintenance workers. However, the victim and other sewer maintenance
workers had participated in a 2-hr training session on confined space safety within the past year.
NIOSH investigators concluded that, in order to prevent future similar occurrences,
employers should:
1. Use slide gates instead of, or in conjunction with, inflatable sewer plugs. Slide
gates provide a more positive method for diverting/controlling the flow of sewage
for maintenance purposes, and should be utilized where possible.