EPA's Vessel General Permit and Small Vessel General

Phosphorus
EPA noted in their BE that under natural conditions, freshwater ecosystems generally have low
phosphorous concentrations (< 100 μg/L), but each waterbody is different, and there are
numerous factors which impact how any particular waterbody will respond to excess nutrient
loading, including hydraulic residence time, freshwater inflow, clarity and light attenuation,
geologic substrate, depth, temperature, and degree of physical alterations, such as channelizing.
Additionally, excessive phosphorus and the resulting problems associated with nutrient
enrichment in general are frequently widespread and manifested at a location remote from the
sources, and may not show themselves for some time after significant inputs to the system have
occurred (WERF 2010). Because of the above, EPA chose to use the lowest statewide and/or
site-specific water quality criteria for total phosphorus (10 μg/L) as the basis for CTETA,W in the
analysis.
Since NMFS’ assessment for Ammonia Nitrogen is based on EPA’s exposure analysis, which
assumed that vessel discharges would be completely mixed within the harbor area, acute or short
term exposure of species to pollutants in close proximity to vessels (i.e. within areas of discharge
mixing, is not considered). The uncertainty associate with this assumption is discussed below.
Although, high ammonia concentrations are predicted for discharges (fish hold and fish hold
cleaning effluent) from some vessels, the infrequent occurrence of those vessels (fishing vessels)
in freshwater river RAA harbors (EPA BE) suggest that the likelihood that sensitive listed
species will be exposed, short term, to acutely toxic concentrations of ammonia is low. In
addition, effluent limits and BMPs in the VGP/sVGP for nutrient reduction should further reduce
the chance of hazardous exposures.
EPA estimated that vessel discharges would result in phosphorus concentrations of 0.00594 ug/L
in freshwater environments and 0.543 ug/L in Estuarine/Marine Environments. These values are
well below the most protective phosphorus criteria (at this time). Low expected phosphorus
concentrations along with effluent limits and BMPs required by the VGP/sVGP for nutrient
reduction suggest that vessel discharges will not produce the adverse effects associated with
nutrient enrichment.
Effluent limitations and BMPs in the 2013 VGP and sVGP are expected to reduce/minimize
nutrient loadings from vessel discharges. The Services conclude that adverse effects of nutrient
loading by vessel discharges under the VGPs should not adversely affect listed resources.
Pathogens
The sewage indicator species E. coli, fecal coliform, and enterococcus are typically
nonpathogenic and are used as indicators for the possible presence of disease causing microbes
and protozoans found in the feces of warm blooded animals (USEPA 1986). EPA did not
estimate pathogen loads or select response thresholds for sewage pathogens in its BE. The risks
posed by sewage indicator bacteria for listed resources cannot be quantitatively evaluated due to
the absence of screening benchmarks for protection of fish and wildlife and the absence of
exposure-response data in the literature on the ecological effects of Sewage Pathogen Indicators.
Analysis of pathogen risk to listed resources is further complicated because pathogen exposure–
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