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)
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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