Yazoo City, Miss. │ 7 │ 84.1│ 75 Oak Park, Illinois. │ 26 │ 100 │ 70 Portsmouth, Va. │ 75 │ 8.1│ 65 New Orleans, La. │ 360 │ 99.7│ 60 Rockford, Ill. │ 53 │ 93.0│ 55 Fort Dodge, Ia. │ 20 │ 96.0│ 50 Manchester, Vt. │ 1.5│ 69.0│ 45 Woonsocket, R. I. │ 47.5│ 95.6│ 35 ───────────────────────────────────┴───────────┴───────────┴─────────── Attempts have been made to express the rate of sewage flow in different units other than in gallons per capita per day. A unit in terms of gallons per square foot of floor area tributary has been suggested for commercial and industrial districts. It has not been generally adopted. The rates of flow in New York City as reported in this unit by W. S. McGrane are given in Table 11. The most successful way to predict the flow from commercial or industrial districts is to study the character of the district’s activities and to base the prediction on the quantity of water demanded by the commerce and industry of the district affected. =25. Fluctuations in Rate of Sewage Flow.=—The rate of flow of sewage from any district varies with the season of the year, the day of the week, and the hour of the day. The maximum and minimum rates of sewage flow are the controlling factors in the design of sewers. The sewers must be of sufficient capacity to carry the maximum load which may be put upon them, and they must be on such a grade that deposits will not occur during periods of minimum flow. The maximum and minimum rates of flow are usually expressed as percentages of the average rate of flow. TABLE 8 SEWAGE FLOW FROM DIFFERENT CLASSES OF DISTRICTS Arranged from data by Kenneth Allen in Municipal Engineer’s Journal, Feb., 1918.