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 efficiency there was 62%, and some qualified observers expressed a conviction that Blue Plains had never consistently functioned at much over 50%--in other words, it had been returning to the estuary unassimilated organic materials equivalent to the raw discharges of a population of roughly 500,000 to 700,000 people each day. Nor do these figures include a great deal of sludge that has been flushed on into the river when digesters have failed to function properly, or the plant's frequently inadequate use of chlorination against bacterial pollution and odors. Since the same 1957 conference required of the other metropolitan jurisdictions only that they do equally as well as the main plant in quality of treatment, they have clearly not been obligated to superhuman effort. [Illustration] Criticism of Blue Plains is in part criticism of ourselves. Because of the distinctive relationship between the District and the Federal Government, the District's treatment plant is in a sense a Federal installation, funded through Congress and with more direct links to Federal water quality agencies than any other big municipal plant in the country. The number of people the plant serves has, of course, increased greatly in the past ten years. It may have been, as has been claimed, somewhat underdesigned to begin with, and it undoubtedly needs expansion now. Yet a rather substantial improvement in the quality of treatment there in quite recent months, mainly under the stimulus of this planning effort and the present surge of interest in the Potomac, indicates that had emphasis on low operating costs been subjugated to pride in results, the present plant could long ago have been made to function reasonably well and the estuary would have had to cope with a much lighter load of wastes.