Pump stations are essential for delivering water and removing waste for communities, but effectively designing and implementing them poses several challenges. The engineer must not only understand the demands on the current system, but also anticipate future needs to avoid designing a facility that quickly becomes redundant or obsolete. Pump station renovations must not disrupt existing water and sewer services, and new force main construction has to carefully navigate the grid of other utilities so as not to interrupt electricity, gas, or communications services. WithersRavenel understands the complexities of pump stations, and has completed several renovations and new builds that illustrate the delicate balance that must be achieved in the design.
New pump stations are typically constructed to serve an area of new development, and they are often designed with only nominal consideration for expansion or future nearby developments, which means that in a fast-growing area an adequately sized pump station is quickly rendered under-sized by the addition of a new neighborhood or retail plaza.
WithersRavenel worked with multiple developers to design the Basal Creek, Northwest Regional, and Farmhouse pump stations so that they would easily accommodate future build-out of the sewer basin as well as eliminate other existing up-stream pump stations. In the case of the Basal Creek facility, the design anticipated the need for and eventual construction of a school, which has since been built and is well-served by the pump station.
The Town of Fuquay-Varina has three water booster pump stations: one that receives water from the Cape Fear River Basin via Harnett County, one that receives water from the Neuse River Basin from the City of Raleigh and one along Highway 42 that receives water from the Neuse River Basin via Johnston County.
After technical evaluation of the existing pumps at the Highway 42 facility and hydraulic modeling of the larger water system, WithersRavenel recommended specific upgrades to increase pumping capacity, which has several benefits to the Town. During peak flow periods, demand is better distributed between the three pump stations, reducing overall operational costs. Each pump station can better balance when the pumps cycle on and off—cycling too frequently or not frequently enough causes extra wear on the pumps over time—which means maintenance costs are also reduced.
Finally, because the Town is in the uncommon position of receiving water from two different river basins, it must be diligent in making sure that the quantity of water that comes from each for drinking eventually returns as treated wastewater. In this instance, the limit for interbasin transfers, or water removed from one river basin and discharged in the other, is 2 million gallons per day. By increasing the capacity of the Highway 42 water booster station pumps, the Town has greater flexibility in deciding where its water will come from, and can adjust its intake from each source based on its ability to replenish the supply.
In the 30+ years since these three facilities were constructed, pump station design has changed dramatically. The underground steel “can” layout that was used three decades ago is difficult—even dangerous—to maintain, requiring a technician certified to work in confined spaces and prepared to deal with wet conditions and potentially hazardous gas build-up.
WithersRavenel worked with the Town to modernize these facilities, taking advantage of the existing infrastructure to save money rather than building entirely new facilities elsewhere. New above-grade suction lift pump stations were installed over the existing wet wells; this design is safer and easier to maintain because a regular technician can access the pumps without going underground. Upgraded electrical control panels and backup generators increased pump station efficiency from about 100 GPM to approximately 200-300 GPM, in addition to being easier to service.
This regional sewer pump station was originally designed to direct wastewater to the Terrible Creek Wastewater Treatment Plant in northern Fuquay-Varina. In order to extend the capacity of the Terrible Creek facility by several years while continuing to promote regional growth, particularly in the popular northern part of Town where the plant is located, the Town approached WithersRavenel for alternatives for redirecting wastewater to the Harnett County Wastewater Treatment Plant.
After considering the presence of local wetlands and endangered species, stream classification requirements, buffer impacts, and other permitting criteria, WithersRavenel recommended adding an adjacent wet well with a 300 GPM simplex VFD pump to the existing pump station site. Under this configuration, the new pump discharges existing average daily flow to a previously abandoned force main that was placed back into service to discharge to the Kenneth Branch Interceptor and ultimately the Harnett County Wastewater Treatment Plant; during existing peak flow periods and as basin build-out continues, all excess flow is directed back to the original 1260 GPM pumps that discharge to the Terrible Creek facility.
Not only does this facility renovation extend the life of the Terrible Creek Wastewater Treatment Plant, it also ties into the same effort as the Highway 42 water booster pump station renovation to manage interbasin transfers. With greater control over both the water source and the sewer collection system, the Town of Fuquay-Varina can provide for its citizens while protecting the environment.