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I I I I I I I I I I I I I I I I I I I 2.3.3 Peak Demand Design flows for water supply systems are often as large ~s the estimated peak day average usage. Demand fluctuations during the day are generally more economically supplied from storage facilities located near the point of use than from extra capacity in the primary water supply 1 i ne. Desi gni ng a water supply line for less than the peak daily average flow is sometimes cost effective, depending upon the relationships between incremental costs of tennina1 storage near points of use and the costs of incremental pipeline capacity. Consequently, once the average demand rate for a municipality is detennined, the relationship between the average demand, peak demand, and storage must be established to detennine the optimal pipeline design flow rate. In this report, the ratio of the peak period flow rate to the annual average flow rate is referred to as the peaki ng factor. Peaki ng factors must have the peri od defi ned--such as monthly, weekly, daily, or hour1y--to fully indicate the distribution of flow with time. Many standard texts contain estimates of peaking factors. As presented by the American Water Works Association (1952), the peaking factor for the peak daily average flow for typical IJ. S. municipalities has been estimater\ to he in the range of 1.5 to 2. O. Because those estimates were made fr'om r'eco..ds in the northe~stern United States, they are not expected to be directly applicable for a town such as Towaoc. Western cities can reach daily peaking factor's as high as 3.0. The Towaoc water allocation of 1000 af per year equates to a unifonn flow rate of 1. 38 cfs or 620 gpm. Util i zi ng the maximum referenced peaki ng factor of 3.0, the maximum design the range of design flows for the pipeline is between 1.38 cfs and 4.14 cfs. The design flow and design peaking factor are addressed in more detail in Chapter 3. 2-7