In May of 1966 the Federal Water Pollution Control Administration was transferred from the Department of Health, Education, and Welfare to the Department of the Interior, with a good many changes in personnel. A valuable move toward the longrun unity of Federal environmental study and action, this change has meant that the agency's shakedown period in its new surroundings has come during the latter part of our Potomac work, and that some large questions of policy and procedure are only now being answered. Furthermore, the fact that our study has coincided with the inevitably lengthy shaping of the State standards, and with their review and their coordination on specific interstate streams like the Potomac and its main tributaries, has somewhat blurred our view of this most significant legal machinery of all. For it is through these standards and their enforcement that the fundamental action toward a clean Potomac will be taken. The emphasis in formulating them and reviewing them has been on vast improvement, not on a rationalization of existing conditions, and behind them there is going to be legal muscle for enforcement. Erosion and sedimentation, particularly from urban and industrial sources, will be of concern in these State programs, and in fact some Basin States already have powers for use against them that have never been brought fully to bear, but undoubtedly will be with the new impetus. At the Federal level, going programs of the Department of Agriculture--primarily under the Soil Conservation Service but also involving the Forest Service--are the best machinery we have. Their techniques of soil protection and runoff detention have been described earlier, and are often applied in a coordinated way to whole small watersheds. Mainly they are put into practice through the voluntary cooperation of landowners, watershed associations, and local or State governments, stimulated by Federal technical assistance and cost-sharing. * * * * * It was noted earlier that these techniques can also be effective against careless urban land shaping and other new concentrated sources of silt such as strip mines. But in terms of legal machinery, these areas present problems, chief among which is the matter of incentive on the part of those who must cooperate if the programs are to work. In an agricultural watershed, the effect of soil conservation practices and flood control measures on the health and productivity of the land is sharply evident to rural landowners and others in the neighborhood, who all benefit from it and usually are eager to cooperate. But strip mine operators and urban developers and road contractors and such folk seldom have to live personally with the erosion and mud and trouble that may result from the way they move earth and change the landscape. To them, sediment control and respect for the way watersheds work, even with cost-sharing, is likely to loom as simply an extra expense.