Romtec Utilities engineers a lot of stormwater pump stations. These systems are used for several different purposes, and before any engineering takes place, it is important to understand the application of the system. So, let’s take a look at applying a pump station to a detention pond system for stormwater.
A detention pond can be thought of in two ways. The first is a pond that takes in stormwater but needs to be pumped to prevent overflow during a stormwater event. The second is a pond that is large enough to “handle the event” and then pumps out at a preset rate afterward.
In the first situation, the wet well will commonly be large in order to accommodate large amounts of stormwater flowing from the detention pond. Pumps for this type of system might also be large in terms of horsepower, or the design could specify more efficient pumps for stormwater like vertical turbine pumps. Here, the design typically would specify duplex or triplex pump configurations (2 or 3 pumps) to allow pumping in multiple cycles. Another approach is to include Variable Frequency Drives (VFDs) to match the unpredictable inflows.
In the second situation, the wet well will typically not be large. Since the pond is sized to contain a stormwater event, the pump station will only need to empty it. The simplest solution is to put in two pumps that will discharge at a known rate to disperse a known volume of water.
In both of these scenarios, the wet well can be configured in rectangular or round precast concrete. To select the size and shape of the wet well, two aspects are important: the size of the total system and the location of the system. Rectangular sumps will typically be used in areas where deep underground excavation is not possible and in systems with numerous in-well components. Round wells are appropriate for the majority of detention pond systems because of their widespread use and familiarity.
In any stormwater system with a detention pond, Romtec Utilities will start by asking which of these two scenarios your project fits in to. With that knowledge, our engineers can design and propose the best practices for engineering a package stormwater pump station.