The St. Mary's River watershed is located in St. Mary's County
in Southern Maryland (see Fig. 1). No point sources pollute its
waters and historically its only threat has been run off from
local farms and occasional storm runoff. However, over the
last few years with the expansion of the county's largest
employer, the Patuxent River Naval Air Station, development
and associated impervious surfaces and runoff have become
an increasing threat to water quality. Beginning in the late
1990s, the Naval Air Station began to dramatically increase the
number of people it employs