This article will discuss manholes, their purpose, different types, as well as what manhole rehabilitation is and why it’s important in today’s world.
What Are Manholes?
For people who walk through their cities and towns during their daily commute, manholes are part of the everyday landscape. What may appear to be a simple, round bump in the road on the surface is actually a door that leads to a largely unknown part of the city that lies beneath. Most people may not be familiar with the elaborate infrastructures on the other side of the manhole cover, but there is so much more to manholes than the bumpy round cover in the pavement.
Manhole Definition
Manholes, which can also be referred to as utility holes, or inspection chambers, are underground structures with openings at street level that provide entry to access utilities like sewers, telephone lines, storm drains, and water systems. Manhole covers can be removed so that trained professionals can enter these underground structures and inspect, clean, repair, and maintain the underground infrastructure. Manholes are found wherever you find buildings. They are located in urban areas where they are typically highly concentrated and also in suburban areas. Less manholes are found in rural areas where there isn’t underground infrastructure.
There are six components of a manhole including:
- cover
- frame
- chimney
- wall
- bench
- channel
These vertical structures come in many different depths and sizes but are universally used to access the underground sewer system. To access the manhole, professionals must first remove the manhole cover, which on rare occasions can be rectangular or square, but are typically round in shape and are typically made from cast iron. Newer plastic materials are starting to be available in the marketplace. Then, they must enter either by way of steps, a ladder, or a winch. Other safety measures should be followed such as a confined space entry permit, air monitoring, and fall protection.
Purpose of Manholes
Manholes were created to serve several different purposes. The first is routine maintenance for different types of public sewer systems; manholes are required to inspect, and clean to identify and prevent obstructions that may occur within the sewer. Sewers may also need to be repaired and these procedures can be performed due in part to the accessibility provided by manholes.
The vented covers atop manholes allow the sewer system to vent, therefore preventing concentrated odors that may be a nuisance. Solid covers are used when there is a chance for water to enter into the vented holes and to contain odors that may be present.
Manholes Depths
Manholes are constructed in depths from just a few feet to over one hundred feet. Shallow manholes are typically at the beginning of a sewer basin and in areas where the sewer can be constructed at shallow depths. The average depth of a manhole in the U.S. is about 9.5 feet. This varies from geographical area. The majority of manholes are circular in shape but some are rectangular or square. Typical construction material is precast concrete for manholes that were built after 1970 and brick construction for manholes built before 1970. Occasionally, there are occurrences where the manholes are exceptionally deep. These are typically installed over major trunk lines that run deep throughout a sewer system.
What is Manhole Rehabilitation?
Even though manholes are hidden beneath the sidewalk and the pavement, they do see a lot of wear and tear. They are an essential part of the sewer system because they provide access points for professionals trained to perform the type of necessary repair work to keep the sewer system running smoothly. Therefore, soil pressure, water pressure, seismic pressure and freeze thaw are the reasons manhole structures deteriorate or completely fail. Naturally, it is only a matter of time before manhole systems need improvements.
Manhole rehabilitation is exactly that; it is the process by which manhole systems are maintained, repaired, and renewed.
Manholes left in disrepair can cause public utilities to fail and can also pose a risk of injury for professionals attempting to repair utility systems. Manhole systems are complex, typically made up of many components from a wide range of materials, all of which will deteriorate on their own over time. Consistent inspection and routine maintenance and repairs will allow manhole systems to last longer and can prevent injury to workers as well as utility system failure.
Manhole rehabilitation can be performed using various techniques depending on which piece of the manhole system is in need of repair. Grouting, cementitious, polymer coating and cured-in-pace are a few of the most commonly utilized methods of manhole rehabilitation. Any combination of these methods may be used to eliminate inflow and infiltration and structurally enhance the manhole.
Prior to beginning any physical work on the manhole system, it’s imperative to perform a thorough inspection so that all necessary work is taken into consideration and can be executed safely through the right techniques, with the right materials for the existing conditions. If the inspection reveals that there are leaks, broken elements, corrosion, or missing parts, those issues must be evaluated to determine the proper rehabilitation methods.
The process of manhole rehabilitation is critical to keeping all public utility systems running smoothly. Even though the work that happens in manholes isn’t always visible doesn’t mean that there aren’t systems in place beneath our feet that make our daily lives safe, efficient, and hygienic. Manhole rehabilitation is the key to maintaining the status quo in our cities and towns. Having an understanding of what happens beneath the surface may change the way people think about those bumpy manhole covers as they pass by during their daily commute.
Closing Thoughts
To learn more about manhole rehabilitation check out the ITCP Training courses we offer.
We also offer free educational sessions on Manhole Rehabilitation for more information on our free educational sessions, visit our web page to learn more.
If you have any questions regarding manholes or manhole rehabilitation, contact our team of experts today.
