FACE 84-13: Two Confined Space Fatalities During Construction of a Sewer Line
Introduction
At approximately 3:26 p.m. on March 8, 1984, a city fire
department received a report that a man was down at a sewer
construction site. When the firemen arrived on the scene, they
learned that two workers were down in the newly constructed
sewer. One worker was an employee of the company contracted to
construct the sewer. The other worker was a state inspector with
the State Department of Transportation. The two workers were
removed from the sewer and pronounced dead at the scene.
Subsequent autopsy indicated cause of death to be carbon monoxide
(CO) poisoning. As a result of the rescue effort, 30 firemen and
8 construction workers were treated for CO intoxication and/or
exhaustion.
Synopsis of Events
In the process of constructing the interstate highway, the
contractor had to construct several thousand feet of sanitary
sewer line composed of 66 inch ID by 16 feet long sections of
concrete pipe. This new line had to tie into an existing line.
The upstream portion of the existing line would be abandoned
after completion of the new line. (Figure)
Figure.
The existing line had to be kept in service during construction.
A by-pass line had to be built around the connection point of the
new and existing lines. This was done by tapping a 30 inch
by-pass line into the existing line, upstream of the connection
point, and tying the by-pass line into a newly constructed
manhole (No. 1) at the connection point. In order to keep sewage
from entering the construction area of the connection point, the
pipe was diked by sand bags several feet upstream of Manhole No.
1. The dike was left in place for approximately 1 month while the
contractor continued to lay pipe.
During this time, sewage seeped/flowed past the dike and extended
approximately 480 feet (30 sections) into the newly constructed
line. This sewage had to be removed before the contractor could
proceed with grouting the pipe joints.
The contractor replaced the sand bag dike with a steel plug to
eliminate further seepage. A gasoline engine driven pump was
placed upstream of the plug so that the existing sewage could be
removed from the pipe. The pumping procedure required a laborer
to enter the new line at Manhole No. 2, walk downstream
approximately 1,200 feet to the pump, fuel the gasoline engine,
start it and exit back through Manhole No. 2. This procedure was
performed on a 3-day cycle. At no time was the atmosphere in the
pipe tested prior to entry, nor was there mechanical ventilation
to remove air contaminants.
This procedure was not removing the sewage quickly enough and it
was decided to increase this cycle to three times per day. On
March 8, 1984, at 8:30 a.m., the labor foreman and one worker
(his son) followed the procedure of starting the pump.
Around 3 p.m. on the same day, the same two workers returned to
Manhole No. 2 to repeat the procedure of refueling the pump.
However, Manhole No. 2 had been covered with plywood and framed
over in order to have concrete poured the following day. So the
two had to enter the pipe from the point of construction. Each
carried a flashlight and the worker carried a can of gasoline.
They began walking the 3,000-foot distance to the pump. After
passing Manhole No. 3, they took a short break and proceeded past
Manhole No. 2 toward the pump. Approximately 750 feet past
Manhole No. 2, the two came to the board used to mark the water
line. While the foreman was moving the board and counting the
pipe length to determine how far the water had receded, the
worker went on ahead to fuel the pump and start it. After
noticing haze in the sewer, the foreman told the worker to keep
talking so he could tell if anything was wrong. Shortly the
foreman heard the worker attempt to start the pump four times and
then say "I feel dizzy." The foreman ordered the worker
out of the pipe. The worker started to leave, dropping his
flashlight and stumbling in his unsuccessful attempt. By the time
the foreman reached the worker, the worker was down and
unresponsive. After failing to carry the worker out, he propped
him up out of the water and told him he was going for help. The
foreman walked, crawled, and stumbled 3,000 feet to the outside
to report the worker was down near the pump. The only ill effect
experienced by the foreman was a severe headache.
Seven workers went into the pipe in an attempt to remove the
downed worker. At the same time the state inspector got into his
truck and drove to Manhole No. 2, where he removed the plywood
cover and entered the sewer. The state inspector proceeded
towards the area where the worker had been reported down. The
underground superintendent also entered the sewer at Manhole No.
2 but exited after 2 or 3 minutes. Six of the seven workers who
entered the pipe at the portal exited at Manhole No. 2. The
seventh man reached the worker but was unable to remove him. The
company safety director entered the sewer at Manhole No. 2 and
reported passing the seventh worker and reaching the deceased.
Shortly after 3:30 p.m., the seventh worker and the safety
director exited the sewer Manhole No. 2.
At this time three firemen arrived at the scene and entered
Manhole No. 2. The firemen were equipped with 30-minute
self-contained breathing apparatus (SCBA). In addition to the
bulkiness of the SCBA, they were hampered by the curved and slick
inner surface of the sewer. Initially, the firemen were told the
victims were down approximately 150 feet into the sewer. However,
they had to travel 500 to 600 feet to reach the victims. As their
air supply decreased, the firemen placed one SCBA on the victim
(the state inspector) who was still breathing, and resorted to
buddy breathing to exit. The state inspector was removed through
Manhole No. 2 at approximately 4 p.m. He was pronounced dead at
the scene. Subsequent autopsy indicated his carboxyhemoglobin
level was 50 percent and his pO2 was 0 percent. The laborer was
removed through Manhole No. 2 at 5 p.m. He was also pronounced
dead at the scene. His carboxyhemoglobin level was 56 percent and
pO2 level was not available.
Conclusions /Recommendations
Combustible gas measurements, oxygen and carbon monoxide levels
were taken 22 hours later at the incident site by an industrial
hygienist. Oxygen level was 19 percent and concentrations of CO
were 600 ppm. The industrial hygienist estimated that
concentration of CO next to the pump on the day of the incident
was 2000 ppm. An air sample taken the following day revealed
readings of 19 to 20 percent oxygen. Trace amounts of H2S were
also recorded.
Given the industrial hygiene survey results and the toxicologic
findings, the cause of death was determined to be exposure to
high concentrations of CO, a by-product of the gasoline-powered
pump, in an area with no natural ventilation, i.e., a confined
space.
While the following list of recommendations is not exhaustive, it
does cover some of the salient points which, if implemented,
could have prevented this fatal incident:
1. When the existing sewer was activated (passing through Manhole
No. 1), no plans were made to prevent the sewage from flowing
into the newly constructed sewer.
Recommendation: An analysis of the conditions
surrounding the connection at Manhole No. 1 should have generated
several safe alternatives for an effective temporary barrier in
the new sewer which also considered safe atmospheric conditions.
2. A gasoline-powered pump was installed inside the sewer (a
confined space) which was known to have almost no ventilation.
Neither workers nor pump could have operated efficiently in the
sewer. The rich mixture created by depletion of O2 increased the
levels of CO.
Recommendation: The pump should have been located on
the outside of the sewer with a hose running to the sewage via an
access hole or an electric motor driven pump should have been
considered.
3. A static ventilating condition was created when the plug was
installed in the new sewer next to Manhole No. 1.
Recommendation: Since it was necessary for workmen
(either those servicing the pump or those planning to do the
grouting) to enter the sewer, adequate ventilation should have
been provided. If ventilation could not create a safe atmosphere,
the use of SCBA should have been mandatory.
4. Workers were permitted to enter an untested atmosphere of a
confined space.
Recommendation: The atmosphere should have been
tested by a qualified person prior to entry by workers.
5. Both fatal victims lacked experience in working in confined
spaces.
Recommendation: If workers are expected, as part of
their job, to work in confined spaces, they should be given
appropriate training.
6. The established corporate safety procedures for work in
confined spaces was not implemented.
Recommendation: Management, including local
supervisors, should comply with approved corporate policy and
procedures for confined space entry as well as other rules and
regulations approved by the corporate president. The policy and
procedure should include entry into confined spaces for rescue
efforts.
7. Workers were not able to adequately assess their risk of
personal injury of the tasks they were required to perform, much
less the additional hazards associated with rescue efforts.
Recommendations: Management should develop a safe job
procedure for all routine tasks starting with high risk tasks and
specifically establish a policy and procedure regarding rescue
efforts.
Emergency Response Recommendations
As a result of evaluation of the rescue events at the scene and
the actual response by the fire personnel in this emergency, five
recommendations have been made. These recommendations are meant
to help improve overall response and practices in terms of buddy
breathing, training, optimal selection and deployment of long
duration SCBA, and use of short duration ESCBA during rescue
efforts.
1. The fire department should reassess the issue of buddy
breathing in regard to the specific confined space pipe incident.
In view of the actual field actions of fire personnel and the
performance of the SCBA under these conditions, the following
questions are appropriate:
Was previous training provided the firemen adequate or should
training be modified to cope in a more efficient manner in a
future incident?
Should buddy breathing be used at all?
All the information gained from this incident should be explored
and used in arriving at and setting a policy for the use of buddy
breathing.
2. The fire personnel who used buddy breathing during this
incident should share their personal experience with all other
fire personnel in the Department.
These firemen should relate their experiences with training
academy practices. This should be related to the rescue of
civilians as well as other fire personnel and all problems
encountered. This experience sharing will result in increased
awareness of the dangers involved, the appropriate methods or
technique to use in a confined space entry situation, and
recommendations to other fire personnel based on actual field
exposure. Education of fire personnel in the use of buddy
breathing under emergency situations based on actual field
experience gained in this specific incident, should be a
beneficial mode of training.
3. Fire department officials should consider the variety and
types of long duration SCBA available for emergency response
requiring extended rescue time and efforts.
Although one-hour closed-circuit compressed oxygen SCBAs are
available, it may be desirable to use newly approved one-hour
open-circuit, compressed-air SCBAs if the oxygen units are to be
used in a potential fire/flame exposure situation. Also, the
breathing air temperature would be cooler utilizing open-circuit
units vs. the closed-circuit units. The low profile and fit of
the closed-circuit SCBA are advantageous over the large profile
type open-circuit where confined space entry is necessary. Such
consideration of available, alternative units can optimize
selection and availability of specific long duration SCBA, which
can contribute to the efficient and safe use of various types of
respiratory support on a specific application basis.
4. The deployment of long duration SCBA at specific fire fighting
companies in relation to their location within the city is
important.
Consideration should be given to those exposures (confined
spaces, shopping centers, high rises and others) where emergency
response could be required at any time. Identification of such
exposures should assist the department in the strategic
deployment of long duration SCBA in relation to the risks
involved.
5. Consideration should be given to the potential use of short
term ESCBA for rescue purposes.
Use of the various types of ESCBA should be based on expected
emergency situations and conditions found in confined spaces,
structural fires and others. The choice of oxygen vs. air units
should be based on specific rationale to optimize their safe use.
This effort would accomplish refined rescue techniques and
minimize the need for use of buddy breathing in certain dangerous
circumstances, potentially increasing the chance of victim
survival as a result.
NOTE: The fire department that responded to this emergency is one
of the best equipped and trained in the country. As a result of
this preparedness, potential injury and fatalities to their
personnel were avoided.
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