EPA's Vessel General Permit and Small Vessel General

Table 23. Decision Process for those Vessel Discharges Not Evaluated in EPA's BE.
Vessel Discharge Description Number of
Vessels
Discharging
Firemain Systems Firemain systems are found on a large number of vessels and draw in water
through the sea chest to supply water for fire hose stations and sprinkler
systems. Systems are activated during testing or during an actual fire. Small
Well Deck
Discharges
Aqueous Film
Forming Foam
(AFFF)
amounts of metals may be added to the fire water from vessel piping system.
The welldeck is a floodable platform used for launching or loading small
satellite vessels, vehicles, and cargo from select vessels. Welldeck discharges
may include water from precipitation, welldeck and storage area washdowns,
equipment and engine washdowns, and leaks and spills from stored machinery.
Potential constituents of welldeck discharges include fresh water, distilled
water, firemain water, graywater, air-conditioning condensate, sea-salt
residues, paint chips, wood splinters, dirt, sand, organic debris and marine
organisms, oil, grease, fuel, detergents, combustion by-products, and lumber
treatment chemicals.
Firefighting agent added to fire suppression systems on some vessels to create
foam. Used infrequently (annually or semi-annually) to test equipment for
maintenance, certification, or training. Constituents include fluorosurfactants
and/or fluoroproteins.
Freshwater Layup Freshwater layup is generated when a vessel is pier side or in port for more
than a few days, the main steam plant is shut down, and the condensers do not
circulate. A freshwater layup includes replacing the seawater in the system
with potable or surrounding freshwater (e.g., lake water). Freshwater layup
discharges can be as large as 6,000 gallons per evolution and can contain
residual saltwater, freshwater, tap water, and possibly metals leached from the
Gas Turbine
Water Wash
pipes or machinery.
Gas turbines are used for propulsion and electricity generation on some
vessels. Occasionally, they must be cleaned to remove byproducts that can
Discharge
Volume
and
Frequency
High Low Low
Low High Low
Amount and
Types of
Pollutants
Present in the
Discharge
Low Low Potentially
High
Low Low Low
Low Low Potentially
High
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