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
Discharge detection, navigation, and ranging equipment on large vessels. Discharges
occasionally occur when the water must be drained for maintenance or repair
or from the exterior of the sonar dome. Although not subject to the VGP but
similar in operation to VGP vessels regarding this discharge, sonar dome
discharge volumes on naval vessels can range from 300 gallons per event up to
74,000 gallons per event. Pollutant levels are expected to be low due to the ban
Underwater Ship
Husbandry
Discharges
Chain Locker
Effluent
on the use of tributyl tin.
Underwater ship husbandry is grooming, maintenance, and repair activities of
hulls or hull appendages performed while the vessel is located in the water.
Underwater ship husbandry discharges can contain aquatic organisms and
residue such as rust and biocide from AFC. Underwater ship husbandry is
typically performed only when excessive biological growth is causing vessel
drag and excessive fuel consumption outside of regular dry dock inspections.
Chain locker effluent is water that drips from the anchor chain and anchor
during anchor retrieval. Discharge volumes are small and chain locker effluent
is expected to contain zinc, rust, paint, grease, and any constituents from the
firemain water. The small volume of chain locker effluent results in small mass
loadings and provides opportunity for the transfer of non-indigenous species.
Discharge
Volume
and
Frequency
Amount and
Types of
Pollutants
Present in the
Discharge
Low Low Potentially
High
High Low Low
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