MACOSH FactSheet

Guidelines for Safe Entry and Cleaning of Vessel Sewage Tanks 



Introduction and Purpose

Sewage systems on vessels are known as Marine Sanitation Devices (MSDs)
or Collection, Holding and Transfer Tanks (CHTs). Sewage tank cleaning
is required for routine surveys and inspections, surface preservation,
equipment modification, repairs and maintenance. 

Entry and cleaning of sewage tanks, piping and components are high-risk
operations and they present unique hazards which can lead to injuries
and illnesses to unprotected workers.  (29 CFR 1915.13)

Workers are often exposed to dangerous atmospheres during tank opening
and venting; manual pumping and stripping; breaking or dismantling of
components and piping; pressure-washing, mucking, and scaling.          
  (29 CFR 1915.11 (b), 1915.12)

A dangerous atmosphere is an atmosphere that may expose workers to the
risk of death, incapacitation, injury, chronic or acute illness, or
impairment of ability to escape unaided from a confined space or
enclosed space.  (29 CFR 1915.11 (b))

The purpose of this document is to help prevent exposure of workers to
the known and unknown dangers associated with sewage during tank
opening, entry, cleaning and related operations.  (29 CFR 1915.97 (a),
(c))

Special emphasis is made on good hygiene practices, proper use of
personal protective equipment and safe confined space entry procedures. 
(29 CFR 1915.97 (b))

Applicability 

These guidelines are applicable to the entry, cleaning and handling of
treated or un-treated sewage and gray water tanks; MSD and CHT systems.

Other related components include piping; aeration, vacuum, settling and
treatment tanks and apparatuses; sewage-contaminated water tanks or
waste oil tanks, bilges, or sumps; valves, pumps, grinders, macerators,
and other contaminated equipment.

What is Sewage and Gray Water?

Sewage or “black water” includes wastes from urinals, toilets, any
wastes contaminated by human excrement; effluent solution, suspension
including body wastes and other sanitary wastes.

“Gray water” includes waste waters, uncontaminated by human
excrement from drains, sinks, sculleries, drinking fountains, showers,
washing water, food wastes, laundry waste, etc.   



A “cleaned and sanitized” sewage tank.

Common Health Hazards in Tanks

Atmospheric hazards include oxygen-deficiency; flammable and toxic gases
such as methane and hydrogen sulfide. These gases are detectable only by
properly calibrated instruments.     (29 CFR 1915.12)

Methane gas is colorless, odorless and tasteless, but highly flammable
and is considered an asphyxiant. 

Hydrogen sulfide is also colorless, but highly odorous, flammable and
extremely toxic to humans and animals. At approximately 100–150 ppm,
the olfactory nerve is paralyzed after a few inhalations. Shortly, the
sense of smell disappears, giving a false sense that the harmful gas has
vacated.

Biological hazards may include bacteria, viruses, protozoa, parasitic
worms, fungi, pathogens, and other infectious microorganisms that can
cause illnesses such as hepatitis, typhoid fever, dysentery and cholera.
Inhalation or ingestion of contaminated mists may result in serious
illnesses.

Physical hazards include slips,  trips and falls due to slippery and
sloping surfaces; punctures and cuts from sharp edges; limited access
and egress; corroded ladder rungs; obstructions by piping and
structures. (29 CFR 1915.91)

Mechanical hazards include unsecured equipment; rotating machinery;
uncontrollable leaks and isolation of waste streams. Often times–not
all piping can be positively shut, blocked or blanked effectively due to
aging or structural design.

Chemical hazards include sewage treatment agents containing ammonium
compounds, formaldehyde, chlorine products, sodium hydroxide,
odor-control and sewage-biodegrading enzymes, sanitizers, biocides,
cleaning or bleaching agents, pharmaceutical drugs; hormones and heavy
metals.

Other hazards may include electrical devices, energized equipment,
inadequate ventilation and poor visibility.

Control Measures Prior to Tank Opening or Pipe Breaking

Assess and review CHT or MSD systems, components and piping.

Perform job-site safety and health analyses and be aware of all
associated risks and hazards. Inform all workers involved. (29 CFR
1915.3 (a))

Post warning signs and labels.     (29 CFR 1915.16)

Follow confined space entry testing and permitting procedures.

Use appropriate tools and operating procedures, gas detectors,  PPE and
respirators.

Install and use adequate exhaust ventilation devices, ducting, lighting
and tank-cleaning equipment.

Cover and isolate all work areas with disposable plastic sheeting to
prevent possible contamination.

Strategically place drip pans at pumps, joints, disconnected piping,
tank’s manhole, clean-outs, drops, etc.   

Secure all toilets, urinals, drains, pumps, and sewage treatment
systems.

Isolate, close, secure, divert, de-energize, lockout and tag-out all
valves, piping and associated equipment.

Flush tanks and piping systems; pump and drain all residual products.

Chlorinate or sanitize the tanks and piping systems when applicable. 

Check for residual pressure or vacuum affects of tanks and piping.

If feasible, use a gas detector to test for atmospheric contaminants
inside the tank through sample ports.

Cautiously and deliberately proceed to remove bolts and nuts of manholes
and piping--being alert to any immediately change of conditions and be
prepared to take evasive actions.

As soon as the piping is broken or the tank is opened, apply or insert
ducting to begin exhaust ventilation. Pipe all exhausts down wind,
overboard or away from people.                              (29 CFR 1915
Subparts B, D)

	Ventilation blower and ducting



While staying outside of the tank, continue to test the atmosphere
inside the tank remotely for safe conditions. 

With proper PPE, clothing and respiratory protection, cautiously enter
the tank for internal inspections prior to commencing tank cleaning
operations.

It is recommended that a NFPA Certified Marine Chemist or Shipyard
Competent Person be present when breaching the sewage system, tank or
piping.

Atmospheric Testing Requirements for Confined Space Entry & Hot Work

No tank entry or cleaning is permitted if atmospheric conditions are
found to be IDLH (Immediately Dangerous to Life or Health).

IDLH means an atmosphere that poses an immediate threat to life or that
is likely to result in acute or immediate severe health effects. (29 CFR
1915.11)

	Test for oxygen, combustible gases and hydrogen sulfide prior to
opening tank and entering



Test and confirm the oxygen levels in the tank and around the work
places are maintained at 20.9% by volume.

Test and confirm the combustible gases are maintained at 0% LEL.

Test and confirm the hydrogen sulfide gas is maintained at 0 ppm.

A Shipyard Competent Person or a NFPA Certified Marine Chemist is
required to test all confined spaces, including sewage tanks, prior to
entry for cleaning. (29 CFR 1915.7, 1915.13)

Sewage tanks and all piping must be tested and visually inspected prior
to any hot work activity. (29 CFR 1915.14) 

Respiratory Protection

Wear full-face, supplied-air respirators, with escape-pack, for entry
and cleaning inside a large sewage tank.

Wear full-face, organic vapor/acid gas/HEPA cartridge respirators for
cleaning from outside of a small tank.

Respirator selection should be based on airborne levels of contaminants.
(29 CFR 1915.154)

Personal Protective Equipment (PPE)

Wear full-body, encapsulating suits outside of liners to protect all
exposed skin, in addition to using rubber boots, gloves, hard hats and
eye protection.   (29 CFR 1915 Subpart I)

Have extra flashlights and two-way radios readied for communication.

Set up first-aid kit, eye-wash and flushing station, neutralizing
solutions, and decontamination equipment.         (29 CFR 1915.153)

	A worker with proper protective equipment for sewage tank entry and
cleaning





Decontamination after Tank Cleaning

Shower or wash face, arms, hands and legs with soap using lots of water.

Disinfect equipment with Betadyne or equivalent and wash contaminated
spaces, decks, bulkheads with detergent, sanitizer, or bleach (29 CFR
1915.152 (d))

Dispose off or re-wash rubber boots, gloves, eye goggles, face shields
and respirators with disinfectant.  (29 CFR 1915.152 (e)(v))

Bag contaminated clothing and wash separately. 

Don’t walk into other spaces with contaminated clothing.

Tank Cleaning Procedures

Perform initial cleaning and any additional pumping or stripping through
the opened manhole access.

Pressure-wash, pump-out, evacuate and remove all loose materials.

Manually scrape muck, scale and bag up all hardened/calcified deposits.

Perform secondary pressure-wash and evacuate any remaining products
before sanitizing all surfaces with bleach or sanitizer.

Perform final rinses, squeegee, evacuation, wipe and dry operations.

Sewage Disposal

Dispose of sewage and contaminated liquids, sludge, solids and all tank
cleaning wastes at local or State approved treatment facilities only.

Immunization

Stay current on routine vaccinations such as influenza and tetanus.
Consult with your physician regarding the need for Hepatitis A
vaccination. (NIOSH/CDC)

Minimum Training Requirements (29 CFR 1915.12 (d)

At a minimum, employees should receive training in the following areas: 

Confined Space Entry Procedures;

 Hazard Awareness; 

Atmospheric Testing; 

Calibration of  Gas Detectors; 

Proper Use of PPE and Respiratory Protection; 

Respirator Selection and Fit-testing; 

Tank Cleaning Procedures; 

Ventilation and Engineering Controls; 

Emergency and Evacuation Procedures; and

HAZMAT or HAZWOPER

Regulations / References / Literature

OSHA’s PELs, 29 CFR 1915.1000 and 29 CFR 1915 Subpart B, D.

www.osha.gov/SLTC/etools/shipyard/index.html

ACGIH’s TLVs

NIOSH/CDC’s RELs

NAVSEA Standard Items 009-88; Navy NSTM 593 “Pollution Control”

USCG 33 CFR Part 159 “MSD”

Marine Chemists Association

http://www.nfpa.org/assets/files/pdf/mcdir.pdf

www.aiha.org



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Exhibit 13

