HYDRAULIC DESIGN OF STORMWATER PUMPING STATIONS: THE EFFECT OF STORAGE

In the design of stormwater pumping stations, skillful design can reduce both the initial cost and operating costs. The initial cost can be reduced by providing storage to reduce the peak pump rate. Savings can be achieved by reducing the size of the pump, the pump motor, piping, and valves, and substantial savings can accrue if the number of pumps is reduced. Most electrical utilities assess a fixed charge for the electrical capacity that the utility must maintain to provide service. Because horsepower is directly proportional to the pumping rate, any reduction in the pumping rate will be reflected in the fixed charge. By providing storage to reduce the peak pumping rate, operating costs can be considerably reduced. The effect of storage can be evaluated by using a mass curve routing procedure. This design procedure combines three independent components--the inflow hydrograph, the stage-storage relationship, and the stage-discharge relationship. The mass curve routing procedure identifies the amount of storage required to reduce the peak rate of flow to the fixed discharge rate. Design guidance is also provided for estimating the amount of storage required to accomplish a given reduction, and formulas are provided for calculating the volume of storage basins. (Author)