Wet Well Maintenance and Cleaning Essentials

Proper Wet Well Maintenance Contributes to Sewer System Health and Decreases Risk of Sewer Backups and Associated Environmental and Economic Costs

Wet well maintenance is essential. Any number of things can cause a pump to fail resulting in sewer infrastructure damage, sewer backups or a spill into the natural environment. A recent article in Timmins Today, “Grease and Rags Clog Pumps, Raw Sewage Bypassed into Lake”, demonstrates how things can go very wrong with a sewage system and negatively impact the environment.

The need for monitoring and cleaning of pumping stations has increased over the past decade thanks to the introduction of so called "flushable wipes" and other "flushables" that increase the potential for pump plugging or failure. These items are, in fact, not flushable and whole campaigns have been set up to inform people about their damaging effects and associated costs. In addition to the increased use of “flushables”, new construction and cultural diet have contributed to the growing necessity for increased focus on wet well cleaning and maintenance.

5 Steps to Wet Well Maintenance & Cleaning

While there is no set standard when it comes to pumping station design or maintenance schedule, each station specific cleaning and maintenance needs must be assessed in accordance with the flows and sewage characteristics it receives.

There are 5 essential aspects to wet well maintenance and cleaning:

1. Wet Well Maintenance Safety Considerations

The first aspect for any maintenance and cleaning project is to ensure the project is completed in a safe manner. Wet wells are confined spaces and should be treated accordingly:

• Workers should be trained in confined space entry,
• Continuous gas monitoring should be employed,
• Lockout-tagout (LOTO) procedures should be followed, and
• Emergency procedures should be planned, documented and practiced in advance.

As wet wells often maintain flow during the cleaning and maintenance, extra care should be taken with gas monitoring as the gases in a wet well can change rapidly as influent is received from the sewer system.

2. Plan for Wet Well Cleaning and Maintenance

Each pump station has unique characteristics which will need to be accounted for. Some things will affect the maintenance operation, others may affect the safety procedures required. A wet well hazard assessment should be done prior to entry. Many municipalities have hazard assessments done for their pumping stations which should be reviewed with staff prior to well entry. Proper planning will tie into the safety, timing, water, and disposal aspects to ensure that the maintenance and cleanout activities are completed as efficiently and safely as possible.

 3. Timing of Wet Well Cleaning

Flows through a pumping station will vary throughout the day reflecting the hours that people inhabit those areas. In a heavy industrial area, working hours may experience higher flows, whereas a station servicing a residential area will have higher flows earlier in the morning and later in the evening.

Some pumping stations will have multiple wet wells which can be isolated thereby eliminating inflow as a concern. Smaller stations will have only one wet well and maintenance should be scheduled when flows are typically lowest. Most pumping stations have flow monitoring which will assist in determining the optimal times for wet well cleaning and maintenance.

Another timing consideration is the frequency at which stations need to be cleaned. Often a complete cleaning of a wet well is only needed 1-2 times a year. However, weekly or even daily maintenance by operators is needed to clean bar screens and readily accessible debris.

4. Water Considerations

Proper cleaning and maintenance of wet wells requires a water source to break up the debris that has built up in the pump station. Grease, plastics, hair, rags, and grit can collect in the station and require a high-pressure water source to break up, dislodge, and liquify debris for easy removal with a vacuum truck or submersible pump. If onsite water is unavailable, it can be trucked in to complete the project. 

5. Wet Well Cleaning Disposal

Once wet well clean-out debris is removed from the pumping station, it needs to go somewhere. Few wastewater treatment plants can receive the slurry/grit and debris from a pumping station wet well. Additionally, landfills will not accept material that does not pass a slump test (an indicator for overall solids concentration). Usually the material needs to be taken to a drying bed to solidify and then taken to a landfill for disposal. In some cases, it makes sense to process the material onsite, solidifying it for landfill disposal.

To keep sewer systems running optimally, appropriate wet well cleaning and maintenance is crucial. Keeping the five steps to wet well maintenance in mind and ensuring that you have experienced workers performing the job will set you up for success. If you need to further explore your options for wet well maintenance, contact us; we can use our wet well maintenance expertise to customize the right plan of action for your facility.