EPA's Vessel General Permit and Small Vessel General

increased levels of suspended sediment by increasing filtration rates, increasing the proportion of
filtered material that is rejected, and increasing the selection efficiency for organic matter.
Excess sediment smothers benthic organisms and the surface layer of the benthos can be heavily
impacted and altered. Increased turbidity associated with suspended sediments can reduce
primary productivity of algae as well as growth and reproduction of submerged vegetation (Jha,
2003). In addition, once in the system, resuspension and deposition can “recycle” sediments so
that they exert water column and benthic effects repeatedly over time and in multiple locations.
A review of effects thresholds described in studies published between 1969 and 2001 supports
EPAs conclusion that TSS discharges authorized by the VGPs alone would not result in adverse
effects (Rowe et al. 2003). While TSS loading from the many land based sources are orders of
magnitude larger than that from vessels, vessel discharges pose yet another incremental source to
those land based loadings. The RQ for vessel associated TSS loading in freshwater
environments is 3 orders of magnitude lower than the threshold for a risk conclusion of “remote”
(RQ=0.1). The RQ for eastuarine/marine environments is higher, but still ~ an order of
magnitude below the threshold for a risk conclusion of “remote” (RQ=0.1). NMFS concludes
that TSS contributions from vessels are therefore not expected to tip the balance between neutral
and harmful levels of TSS in waters where our species occur.
VOCs and SVOCS
The toxicity of oil and grease measured as SGT-HEM to aquatic and aquatic-dependent animals
is most often attributed to the water-soluble monocyclic aromatic hydrocarbons or MAHs
(benzene, toluene, ethylbenzene, and xylene, otherwise known as BTEX), and the polycyclic
aromatic hydrocarbons or PAHs (McGrath and DiToro, 2009). EPA’s study of cruise ship
graywater found a total of 17 different volatile and semi-volatile organic compounds in at least
10 percent of samples, for which the most significant rates and levels of detection were
phthalates, phenol, and tetrachloroethylene. EPA also found elevated pththalates (bis(2ethylhexyl)phthalate)
in a few bilgewater and stern tube packing gland effluent samples, as well
as benzene in bilgewater (USEPA 2010b).
EPA stated that for many of the VOCs and SVOCs, there are no definitive chronic toxicity test
data available for aquatic organisms, as well as no data to support selection of response
thresholds based on growth or reproduction. NMFS concurs with EPA regarding the availability
of response thresholds for the many VOC and SVOC substances detected in vessel discharges.
Those organics for which EPA conducted quantitative analysis include PAH and MAH
compounds, bis(2-ethylhexyl) phthalate and 2,4,6-trichlorophenol. The MAH compounds like
benzene are low-molecular-weight compounds that usually do not persist in the environment
because they are volatile and highly biodegradable. Conversely, the PAH compounds
(particularly those with four or more carbon rings) are high-molecular-weight compounds that
are less volatile and degrade more slowly, and thus, persist in the aquatic environment. The
services are supplementing EPAs assessment of VOCs and SVOCS to include nonylphenol and
octylphenol ethoxylates due to the greater toxicity and environmental persistence the degradate
nonylphenol (NP).
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