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.