ustries themselves.

Around the various marinas to be found along metropolitan
shores--several of them Federally owned--sanitary facilities are
generally skimpy, and no regulations govern the discharge of wastes from
boats. Since individual marinas may berth as many as 600 or 700 craft, a
great many of them in daily use during the recreation season and some
inhabited as dwellings the year round, summer conditions that frequently
prevail around these places are not to be described in polite terms.

Less visible at the point of origin though not in its ultimate effects
is the huge organic load that comes to the estuary in the effluent of
local sewage treatment plants, estimated at possibly 300 to 350 million
gallons per day. There are many smaller plants strung out down both
shores of the upper estuary, but four larger ones handle the bulk of
metropolitan sewage. Of these, three--the main plant at Blue Plains in
the District, the Alexandria plant, and the Fairfax County Westgate
plant--furnish secondary treatment, and the fourth, the Arlington County
plant on Four Mile Run, is on the verge of putting new secondary
facilities into operation.

Yet the same problem of plant operation that exists in the upper Basin
also rears its head here. A casual boat ride down the shoreline with a
few excursions up tributary creek-mouths demonstrates that many of the
smaller plants, including a number of Federal ones, are emitting a very
low quality of effluent, and this is borne out by sanitary surveys. The
proliferation of such small plants around cities and elsewhere is a
headache to sanitary authorities, for their very size and numbers create
a probability of trouble. Much effort is going into eliminating them and
channeling the wastes they receive into the larger plants.

But the large plants themselves at this point are a much bigger part of
the problem; on the basis of sheer volume, their contribution to
estuarial pollution dwarfs all others. The Blue Plains plant is by far
the largest of the four, handling wastes from about 1.4 million people
in Washington and outlying areas on both sides of the river. By the
terms of a conference convened in 1957 by the Public Health Service to
investigate the sanitary state of the Potomac at Washington, the
District committed itself to maintain 80% efficiency of treatment at
this plant, which was then brand new. Last year, ten years afterward,
the most generous recent calculation of the effic