EPA's Vessel General Permit and Small Vessel General

esponse follows a “one hit” model which accounts for the possibility, although low likelihood,
that even a single pathogen could cause infection, with the likelihood of infection increasing with
increasing exposure intensity (EPA/USDA 2012).
EPA’s qualitative assessment described an investigation of graywater discharges from cruise
ships which reported enterococci standards for marine water bathing were exceeded 66 percent
of the time and fecal coliform standards for harvesting shellfish were exceeded over 80 percent
of the time (USEPA 2008). Graywater pathogen data provided in the Report to Congress were
several orders of magnitude greater than the screening benchmark for marine water bathing by
humans (USEPA 2010b). In its BE, EPA noted that sewage-associated pathogens are generally
not considered to be harmful to fish or reptiles, stating:
“EPA is not aware of any outbreak of pathogenic disease among aquatic or aquaticdependent
species from vessel discharges. Fish and shellfish are known vectors of
pathogens resulting in human impacts when consumed, but appear to be largely
unaffected themselves. Since it is currently not possible to separate infections in aquatic
and aquatic-dependent animals due to [human] or any other pathogens contributed from
vessel discharges versus infection from existing natural background conditions within a
waterbody, and since it is highly improbable that any infection could occur at the levels
detected in vessel discharges, EPA discounts any risk to pathogens in the BE to the listed
species for which the analysis applies”
NMFS is supplementing EPA’s qualitative assessment of sewage indicator species because the
BE did not acknowledge that human sewage has been identified as the likely source for the strain
of Serratia marcescens which caused outbreaks of white pox disease in threatened elkhorn coral
in the Caribbean (Sutherland et al. 2010) or that marine mammals can host and become infected
by bacterial pathogens associated with sewage (Grillo 2001, Thompson et al. 2005, Venn-
Watson et al. 2010). While EPA concluded that infection is highly improbable at levels detected
in vessel discharges, we must note that EPAs modeling assumed complete mixing of discharges,
and did not address more intense exposures within mixing zones created by potentially large
volume discharges such as graywater. A report by the Alaska Department of Environmental
Conservation evaluating the impact of cruise ship wastewater discharge on Alaska waters
indicates that, although offshore wastewater sources would likely be much smaller in magnitude
than on shore sources, they can represent a more direct and undiluted exposure (ADEC 2002).
We focus the discussion on sewage pathogen indicator levels in graywater because graywater
accounts for greater than 96% of sewage pathogen indicator load in vessels authorized to
discharge under the VGPs, with sewage pathogen indicator loadings through deckwash at 2%,
bilgewater at 1% and, for fishing vessels, fish hold effluent at 2% and fish hold cleaning effluent
at