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
Seawater Piping
Biofouling
Elevator Pit
Effluent
at a rate of 17 gallons of brine for every gallon of fresh water produced.
Reverse osmosis units generate approximately 4 gallons of brine for every
gallon of fresh water produced. The three sources of the constituents of brine
discharge are: 1) influent seawater; 2) anti-scaling treatment chemicals; and 3)
the purification plant components, including heat exchangers, casings, pumps,
piping and fittings. The primary constituents of the brine discharge are
identical to those in seawater; however, they are more concentrated due to
volume reduction.
Some vessels that use seawater cooling systems introduce anti-fouling
compounds (e.g., sodium hypochlorite) in their interior piping and component
surfaces to inhibit the growth of fouling organisms. These anti-fouling
compounds are then typically discharged overboard. Most vessels that have
seawater piping systems are expected to use piping materials such as copper to
prevent biofouling rather than injecting high concentrations of anti-fouling
compounds into their piping systems.
Large vessels with multiple decks are equipped with elevators to facilitate the
transportation of maintenance equipment, people, and cargo between decks. A
pit at the bottom of the elevator shaft collects small amounts of liquids and
debris from elevator operations and deck washdown and runoff depending on
the elevator configuration. Water entering the elevator pit can contain
materials that were on the deck, including fuel, hydraulic fluid, lubricating oil,
residual water, and AFFF. The runoff may also contain lubricant applied to the
elevator doors, door tracks, and other moving elevator parts. Residue in the
elevator car from the transport of materials may also be washed into the
elevator pit. The cleaning solvent used during maintenance cleaning
operations, as well as liquid wastes generated by the cleaning process, can also
drain into the elevator pit sump.
Discharge
Volume
and
Frequency
Amount and
Types of
Pollutants
Present in the
Discharge
Low Low Potentially
High
Low Low Potentially
High
Sonar Dome Water is used to maintain the shape and pressure of domes that house sonar Low Low Low
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