The city of Madison regularly checks the water quality at swimming beaches located on area lakes. The concentration of fecal coliforms, in number of colony forming units per 100ml of water, was measured each day for 15 days during the summer at one beach: 180, 1600, 90, 140, 50, 260, 725, 90, 380, 110, 19, 60, 20, 340, 80