Flashpoint #2
A Marine Chemist Association Newsletter
“Sewage Hazards”
FOR INFORMATIONAL PURPOSES ONLY. DOES NOT SUPERSEDE ANY FEDERAL, STATE, LOCAL
REGULATIONS OR EXISTING COMPANY PROCEDURES.
Summary
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Sewage poses unique exposure hazards to shipyard employees
Atmospheric hazards such as hydrogen sulfide, oxygen deficiency, and flammable gases
are compounded by the potential biological hazards present in all sewage tanks and
sewage piping systems.
The OSHA Maritime Standard, 29 CFR 1915 Subpart B, “Confined and Enclosed and
Other Dangerous Atmospheres, does not specifically address biological hazards
associated with sewage. It does however cover the atmospheric hazards (oxygen,
flammability and toxicity) but a case can be made that Marine Chemists and Employers
are expected to consider the biological hazards as potential toxic exposures.
Marine Chemists and Employers are faced with a dilemma because there are no real time
measurement devices nor are there exposure limits for the biological hazards present in
sewage, however, there are recognized hazards such as hepatitis, typhoid fever, dysentery
and cholera
Efforts should be taken to reduce the biological hazards associated with sewage.
Marine Chemists will typically use the “Enter with Restrictions” standard safety
designation based on their visual inspection and will proscribe PPE and other controls
because they recognize the potential for a biological hazard to exist but have no real time
monitoring equipment or exposure concentration guidelines to evaluate the hazard.
A biological hazard is assumed to be present and precautions are stipulated based on the
Marine Chemist’s professional judgment.
Sewage Hazards in the Maritime Industry
There are several issues the Marine Chemist
faces when dealing with entry into sewage
tanks and/or work on sewage piping
systems. Marine Chemists agree that some
precautions should be taken to reduce the
potential biological hazards associated with
sewage and other wastes but accurately and
consistently proscribing those precautions is
difficult for the following reasons:
Issue #1
Using the standard safety designation “Enter
with Restrictions” has historically meant
that the chemist:
 Has determined atmospheric
concentrations for a contaminant in a
space
 Compared them to either regulatory
(OSHA) or recommended (ACGIH)
exposure limits, and
 Prescribed specific engineering or
administrative controls or PPE.
There are no real time tests or exposure
limits for biological hazards. Without this
information it is difficult for a chemist to
specify PPE or administrative controls.
Issue #2
Using an indicator (marker) such as coliform
to make an assessment for other biological
hazards is not feasible
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There is no real time coliform test nor is
there exposure criteria for coliform
Coliform tests require contact with the
surface of a space. This impacts the
validity and accuracy of the test as one
cannot presume that the contamination is
consistent throughout, nor that the
sample is representative of the space.
Coliform testing does not provide a valid
representation of other biological
hazards. No single test can be used as a
marker.
Issue #3
Various methods of disinfection (chlorine,
NaOH, steam, UV, ozone) all pose the same
problem. Absent a test to determine safe
concentrations of a contaminant, it is
difficult for a Marine Chemist to
scientifically evaluate the effectiveness of
the cleaning method. At best these methods
are of disinfection are effective of surface
contamination only and contamination
below the surface may not be adequately
treated. Disinfection should be viewed as a
method to reduce, not eliminate, biological
hazards.
Issue #4
The atmospheric requirements for
“Atmosphere Safe For Workers” in NFPA
306 may be met during initial opening of a
tank or pipeline or shortly after ventilation
Sewage Hazards in the Maritime Industry
has been applied. However, once the
residues are disrupted atmospheric hazards
such as hydrogen sulfide and methane are
easily re-created. Most chemists would insist
that cleaning be performed to reduce this
potential. It is also apparent to chemists that
the “Enter with Restrictions” designation
more appropriately protects employees who
are cleaning dirty sewage tanks. However,
when the cleaning is complete the chemist is
left with the decision of how to remove the
restrictions absent some quantitative
measurement to evaluate the effectiveness of
the cleaning operation. Many chemists
choose to use “Enter with Restrictions” even
after the cleaning is complete. The PPE
requirements placed on the certificate are
due to the absence of exposure data, the
inability to evaluate the hazard and the
results of the chemist’s visual inspection. It
really comes down to whether the chemist
feels a biological hazard exists – in other
words professional judgment.
A logical approach to this problem is to take
steps to reduce the potential contamination
and to use the “Enter with Restriction” or
“Atmosphere Safe for Workers”
designations but to specify common sense
protective measures on the certificate. These
measures may include protective clothing,
gloves, boots or a simple note stating that
good personal hygiene (washing up) should
be used upon leaving the contaminated
space.
Sewage Hazards in the Maritime Industry
A Logical Approach to Certification of Sewage Tanks and/or Sewage Systems
Flush, Disinfect and Clean
Initial Flush of the Piping System and/or the Tank with Water
System - this can be accomplished by flushing urinals and toilets several times
Tanks – fill with water and drain as appropriate
Disinfection - will help reduce the amount of atmospheric contamination
Add a disinfectant to the piping system and tank
Allow the disinfectant to remain in the system/tank for an appropriate time period
Flush the Piping System and the Tank with Water – Remove the Disinfectant
Flush the piping system/tank to remove the disinfectant
Open the System or Tank
Exhaust ventilation on site
Monitoring equipment on site
Open the piping systems or tank slowly
Be prepared for spillage
Test the Atmosphere
Test the atmosphere in the piping system or tank.
Chemist’s Visual Inspection
Perform a visual inspection of the piping system or tank and re-flush or mechanically
clean as necessary.
Initial Entry by Personnel for Mechanical Cleaning
It is recommended that an “Enter with Restrictions” certificate be issued for this initial
entry proscribing appropriate protective clothing and possibly respiratory protection
based on the outcome of the visual inspection. The certificate should recommend good
personal hygiene practices.
Certification
If you chose to issue an “Enter with Restriction” standard safety designation
Specify PPE required to enter the tank IAW NFPA 306
Recommend adding a note to the certificate about good personal hygiene
If you chose to issue an “Atmosphere Safe for Workers” standard safety designation
Recommend adding a note to the certificate on good personal hygiene
Safety Alert: Deadly Hydrogen Sulfide and Shipyard Sewage
Shipyard employers and employees must be fully aware of the hazards and dangers of sewage systems on ships
and at shipyard shore facilities. In recent years there have been several fatal accidents where up to four workers
were killed while working on a sewage system. The principal cause of these worker deaths was the inhalation of
hydrogen sulfide (H2S) gas, which can be generated by sewage. H2S gas smells like “rotten eggs” and, when
inhaled, can render a worker unconscious in seconds and kill them. With proper training and procedures,
employers can prevent accidents involving H2S gas from sewage systems. (Note: On Navy and Coast Guard
vessels, the term “Collection, Holding and Transfer system” (CHT system) is commonly used for sewage
systems.) For more information about H 2S, please review the Hydrogen Sulfide Quick Card at www.osha.gov.
BEFORE OPENING OR OTHERWISE BREAKING INTO A
SEWAGE HANDLING SYSTEM, TAKE PRECAUTIONS:
SUPERVISION & MANAGEMENT:
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Consult with shipyard safety personnel before assigning work on sewage systems. They should be
aware of and ready to help deal with these hazards.
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Ensure you and your workforce have carefully reviewed and understand the position, function, condition
and use of all piping, valves, and back-flow prevention associated with the sewage system. (In vessel
repair situations, discuss and review the intended work with the vessel's engineering staff or ship
superintendent if available.)
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Verify that the system has been chlorinated or otherwise sanitized to kill potentially infectious waste.
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Verify that the system has been emptied, flushed with clean water and discharged to appropriate sewage
disposal.
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Verify that the system is isolated (using positive mechanical means) from shore-based sewage disposal
systems, and that back-flow prevention, such as check valves and vacuum breakers, is in place and
functioning. (Remember, a vessel or pier-side tank connected to shore-side sewage discharge lines is
usually downhill from the sewage treatment plant it is discharging to. Failure of isolation may result in the
shore-side system's sewage flowing to the pier or into the ship!)
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Ensure that your shipyard competent person, a marine chemist or industrial hygienist are available to
inspect and test the atmosphere of the piping or space before it is broken into. This will help verify how
effective the flushing was.
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Investigate whether the system piping flows through sealed and otherwise inaccessible spaces, and have
those spaces inspected and tested before work begins on the system. (Corroded and failed piping may
allow the accumulation of dangerous sewage gases in connected sealed spaces.)
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When uncertain and until the system is proven to have no hazard potential, post a safety watch at the
opening of the space who can summon rescue.
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On systems that are enclosed and aboard vessels, ensure that the system-containing space is supplied
with exhaust (negative pressure) mechanical ventilation before breaking into the system. Ensure the
discharge of the ventilation is to the weather-air and away from the vessel.
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Ensure there is an easy and unobstructed escape path for employees if sewage is released into the work
area.
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Train and require that your employees evacuate the work area immediately if they smell sewage, if they
sense anything unusual, or if unexpected amounts of liquid begin to enter the space from the system!
Hydrogen sulfide smells terrible (like “rotten eggs”) but will quickly disable worker's sense of smell, make
them dizzy, unconscious, and then kill them!
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Train and require that when employees must evacuate such a space, they must NEVER RE-ENTER until
a shipyard competent person, a marine chemist or industrial hygienist tests the atmosphere and certifies
that the work area is safe to enter.
ASSIGNED AND AFFECTED WORKERS:
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Follow direction of shipyard safety personnel when opening or working on a sewage system.
They will help you do it safely.
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Ensure you have carefully reviewed and understand the position, function, condition and use of
all piping, valves and back-flow prevention associated with the sewage system. Get answers to
your questions about these systems - they are potentially very dangerous. (In a vessel repair
situation, discuss and review the intended work with the vessel's engineering staff or ship
superintendent if available.)
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Verify that the system has been emptied, flushed with clean water and discharged to appropriate
sewage disposal.
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Verify that the system has been chlorinated or otherwise sanitized to kill potentially infectious
waste.
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Verify employer has isolated the sewage system.
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Ensure that your shipyard competent person, a marine chemist or industrial hygienist has
inspected and tested the atmosphere of the piping or space before you break into it. This will
help verify how effective the flushing was.
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If the system piping flows through sealed and otherwise inaccessible spaces, make sure those
spaces have been inspected and tested before breaking into the system. (Corroded and failed
piping may allow the accumulation of sewage and dangerous gases in connected sealed spaces.)
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Until the system is proven to have no hazard potential, check that a safety watch is posted at the
opening of the space who can summon rescue.
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On systems that are enclosed and aboard vessels, ensure that the space you are in is supplied
with exhaust (negative pressure) mechanical ventilation before breaking into the system. Ensure
the discharge of the ventilation is to the weather-air and away from the vessel.
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Ensure there is an easy and unobstructed path you can use to escape if sewage is released into
the work area.
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Evacuate the work area immediately if you smell sewage, if you sense anything unusual, or if
unexpected amounts of liquid begin to enter the space from the system! Hydrogen sulfide smells
terrible (like “rotten eggs”) but will quickly disable your sense of smell, make you dizzy,
unconscious, and then kill you!
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When a space has been evacuated, NEVER RE-ENTER until a shipyard competent person, a
marine chemist or industrial hygienist tests the atmosphere and certifies that the work area is safe
to enter. Talk to the tester and read their posted report before re-entering the space.
Through OSHA’s Alliance Program, this Safety Alert was developed through the American Industrial Hygiene
Association, the American Shipbuilding Association, the National Shipbuilding Research Program and the
Shipbuilders Council of America Alliances for informational purposes only. It does not necessarily reflect the
official views of OSHA or the U.S. Department of Labor.
Question and Answer Page
Question: Is sewage hazardous?
Answer: There is no doubt that the
atmospheric hazards associated with
sewage can be deadly. Exposure to
hydrogen sulfide in particular has caused
several recent deaths in the maritime
industry. The biological hazards, on the
other hand, are much more difficult to
quantify and there are a variety of
opinions as to the degree of hazard.
Question: How do you deal with an
unknown such as biological
contamination?
Answer: It is always better to air on the
side of safety and take precautions that
can help minimize the risk. If you’re not
sure why not wear PPE and apply good
personal hygiene to eliminate the
potential.
Question: What can be done to address
the deadly hazard associated with
hydrogen sulfide?
Answer: Proper planning and
engineering controls are critical.
Utilizing experienced individuals to set
up the job site, having proper ventilation,
lock out tag out, flushing, disinfection
and being prepared for the unexpected
are all crucial to performing work on a
sewage system or tank.