Combined effects of mechanical availability and storage capacity in pumping station risk assessment

Pump failure is defined as the inability of the pump to pump at design capacity. In an urban drainage system failing pumps may result in sewer overflow and flooding. However, the system failure may be due to an unexpected rainfall event exceeding the overall design capacity of the pumps, or to the failure of one or more pumps being the inflow to the pumping station less than the design capacity. Here we propose a model that incorporates two stochastic models for (a) the storm water discharge and (b) the complex system functioning, into a tool for the storm water sewer reliability assessment. In our schematic stormwater sewer system a pipe network with storage capacity transfers water to the pumping station, and the pumping station discharges the incoming flow to a water body at higher level thanks to the interplay of a number of pumping units. The model may be used to evaluate the reliability of different design solution in order to define the design criteria that maximize the system service and minimize the realization costs.