EPA's Vessel General Permit and Small Vessel General

Estimates of Exposure Resulting from Discharges Authorized by the VGP and
sVGP
This section summarizes the modeling approach EPA used to estimate exposure of threatened
and endangered species and their critical habitat to VGP-authorized discharges. Greater detail is
provided in section 5 of EPA’s BE. Representative Action Areas (RAAs) were selected by EPA
after consultation with the Services to be used to evaluate the potential exposure and effects of
permitted discharges on listed aquatic and aquatic-dependent species, as well as their designated
critical habitats. The following selection criteria were used to identify the RAAs evaluated in the
BE:
� High density of vessels covered under the VGP and sVGP to capture a reasonable “worst
case” scenario;
� Varying percentages of vessel types present to capture the variability in pollutant loading
rates;
� Selection of RAAs that provide broad coverage of diverse ecosystem types and broad
geographical representation;
� Selection of “special interest” locations with known or expected sensitivities for specific
taxa and their critical habitats (i.e., Pacific coast salmonid populations, sea turtles in Gulf
of Mexico, etc.) and/or specific vulnerabilities (e.g., historic introduction and spread of
ANS in the Great Lakes).
EPA’s NOI Summary Report and EPA’s Report to Congress on Vessel Discharges were used to
identify the top Home/Hailing Ports for each vessel type. For vessels expected to be covered
under the sVGPs (large and small), New York, NY; Houston, TX, and Seattle, WA were
consistently among the top 10 port cities, as well as other ports such New Orleans, LA; Miami,
FL; Los Angeles, CA; Norfolk, VA; Pittsburgh, PA; and St. Louis, MO (to name a few). Among
these port cities, nearly all are representative of estuarine/marine ecosystems, except for inland
port cities such as Jeffersonville (Indiana), Pittsburgh, St. Louis and Cincinnati (top port cities
for barges on large inland rivers). Port cities on a large freshwater lake (Great Lakes) system do
not appear to be among the most heavily trafficked. From this initial list of port cities, EPA
selected seven RAAs for detailed evaluation in the BE that were both ecologically and
geographically diverse and captured several special interest locations identified during
preliminary informal consultation meetings with the Services (Table 24).
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