Water Pollution, 1968: on S. 2525, a bill to amend the Federal Water Pollution Control Act, as amended, to control pollution from vessels within the navigable waters of the United States, April 2, 3, and 4, 1968 and 3206, a bill to amend the Federal Water Pollution Control Act, as amended, relating to the construction of waste treatment works, and to the conduct of Water Pollution Control Research, and for other purposes, April 10, 11, and 23, 1968