The wastewater lift station of an urban municipality is old. Pumps are nearing the end of their usefulness, the controls need modernization and the access hatch needs to be replaced. Yet the concrete wet well is robust and solid.
Should the entire station be demolished and rebuilt? Not necessarily. The better question is whether the current infrastructure can support a modern pumping system without compromising the reliability, accessibility to maintenance and capacity.
Image credit: romtecutilities.com
A carefully engineered pump station retrofit can preserve valuable infrastructure while replacing components that no longer meet operational requirements.
Start with the Structures That Nobody wants to replace.
It’s expensive and difficult to change the wet well since it is submerged in the ground, connected to piping and is essential for the collection of wastewater.
The retention of a concrete structure that is still serviceable can make it easier to dig and build.
The loss of space around the access hatch might cause problems with this decision. Romtec Utilities says that wet well hatches are usually replaced as part of retrofits. Instead of gluing a hatch to cement that is deteriorating replacing the whole top layer might be a more reliable option. This will allow for greater access to the structure and extend its usefulness, without having to replace the entire structure as well.
A More Powerful Pump Changes the Engineering
Imagine that a residential area has seen a significant increase in population from the time of the first lift station installation. The existing pumps might not be able with the growing flow of wastewater.
An upgrade to the pumping station could include higher horsepower pumps, however the choice of equipment cannot be made independently of the surrounding system. Pumps with greater power may require adjustments to elbows for discharge, piping valves, electrical controllers and other elements.
Engineers also need to evaluate the system’s hydraulic requirements including the head of flow and total dynamic head. Installing a larger pump without evaluating the situation may cause more issues than it resolves. Planning for future capacity during the initial design stage can make later expansion considerably easier.
Check that the waste water is moving during construction
Retrofitting a pump station for wastewater presents a unique challenge, which isn’t faced by other projects. The station may have to be operational for the duration of construction.
Contractors continue to work and wastewater continues to come in. Depending on the project an interim bypass pumping system may be required to maintain operation while the existing equipment is removed and new components are put in place.
Romtec Utilities embraced this challenging task in the Federal Law Enforcement Training Center, Brunswick, Georgia.
The project involved replacing two old wastewater lift stations and ensuring the operation at the facility. Site-specific engineering packages, bypass pumping techniques allowed for the existing station footprints and operational requirements. This example shows the importance of taking time to think about the sequence of construction before installing.
If replacing is the only option
Not every station is suited to be renovated. Sewer lift stations may need to be replaced if they have a severely damaged wet well, or have a low capacity for structural strength.
In making a final decision, it is crucial to look at the structural condition of the structure, its compatibility with equipment, its accessibility to construction, the continuity of services as well as long-term requirements. Romtec Utilities begins retrofit and replacement projects by determining which components will be left and which require replacement.
The company then develops engineering solutions that are specific to the location, initial plans and budget estimates. Prefabricated parts are also helpful to organize installation and reduce the number of on-site requirements.
The Project isn’t Complete until the Pumps Start
The modernized lift station should be able to function as a system. Before returning a lift-station to normal operation, initial testing, commissioning, as well as verification of equipment are required to ensure that all pumps, control systems, and the related equipment function in accordance with the specifications.
Operator training, as well as operation and maintenance manuals are equally important. Maintenance staff must understand the new equipment, operating procedure, and documentation before taking responsibility for the station.
A successful retrofit helps preserve the value of infrastructure and addresses the shortcomings which led to the need for modernization.
Municipalities and owners of facilities must consider more than just immediate repairs. The most successful projects integrate the latest equipment with the existing structures. They ensure essential services during construction and prepare the pumping systems to run for many years.
