EPA's Vessel General Permit and Small Vessel General

Graywater and Graywater Mixed with Sewage. Graywater volumes depend primarily on the
type of vessel and the number of passengers and crew onboard (Table 18). For example, cruise
ships generate more graywater than cargo ships since they have many more passengers and crew.
Further, cruise ships also generate higher graywater volumes per capita than cargo ships because
passengers and crew on these vessels use galleys and accommodations (sinks and showers) to a
greater extent than crew on cargo ships. Estimated graywater generation rates reported in
response to EPA’s 2004 cruise ship survey ranged from 36 to 119 gallons/day/person, with an
average of 67 gallons/day/person (USEPA 2008) for large cruise ships. Finland’s Ministry of the
Environment estimated cruise ship grey water generation at 120 liters per day (32
gallons/day/person) (BMEPC 2007). During EPA’s 2004 Alaskan cruise ship sampling
program, graywater generation on one ship was 45 gallons/day/person (USEPA, 2006).
Table 18. Estimated Graywater Discharge Rates Used in EPAs BE.
Vessel Type
Number of
Passengers
and Crewa
Estimated Graywater
Discharge Rate d
gal/day m3/day
Barges 4 61e 0.23
Cargo/Bulk Carriers 25 1,125 4.2
Commercial Fishing Vessels 29 1,305 4.9
Large Cruise Ships 3,455 155,475 588
Medium Cruise Ships 315 14,175 53.6
Large Ferries 559 25,155 95.2
Oil and Gas Tankers 22 990 3.7
Passenger Vessels (tour boats, water taxis, etc.) 282b 12,690 48
Utility Vessels (tug boats, off-shore vessels,
6c 1 270
etc.)
a) Number of crew and passengers from EPA’s NOI Report (USEPA, 2011e) unless otherwise specified.
b) Average number of passengers and crew calculated based on information gathered from both personnel
communication with operators and web site marketing data for tour boats, dinner cruise vessels, wedding party
boats, whale watching tours, and shuttle service vessels. Vessels do not provide overnight accommodations.
c) Based on personal contact with AEP River Operations.
d) Based on a graywater generation rate of 45 gallons per person per day (USEPA, Sampling Episode Report
for Holland America Veendam, Sampling Episode 6503) Washington, DC (USEPA. 2006).
e) Average flow adjusted based on an estimated 33.8% of barges are manned and would therefore generate
graywater (USEPA, 2011e, Section 2.2.1.5 and Figure 2.1-1)
Graywater can contain high levels of pathogens, nutrients, soaps and detergents, and organics.
EPA analyzed the risk of this discharge in its BE due to the high number of vessels discharging,
the large volume and frequency of discharges, along with the potentially high risk posed by the
concentration and types of pollutant discharged. EPA estimated concentrations of graywater
pollutants based on data for the vessel types examined in the Report to Congress (Table 19).
Contaminants identified in graywater include metals oil and grease and nutrients.
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