Manholes connect underground utilities to the surface and have covers that allow easy access for maintenance. Some lead to underground vaults, while others connect to a series of pipes. Manhole covers are typically round and can provide a pictorial history of the utilities in a city.
A manhole, or maintenance hole, is a pipe that connects underground utilities to the surface. The pipe is large enough to hold a worker’s body and is covered by a top that is flush with the ground and called a manhole cover. Manhole covers can be found connected to water and sewage systems, along with electrical and fiber optic cables. In all cases, manhole covers are located at primary junctions, and sometimes at intervals along the service line, to allow operators easy access to potential problems.
In some cases, a manhole leads into an underground vault, an enlarged room where switching equipment can be found. An underground vault can be accessed on a regular basis to hook up new clients, perform security checks, and ensure other key maintenance is done. Typically, the underground vault will be relatively small, accommodating one worker at a time.
In large underground systems, manhole covers connect to a series of underground pipes, some of which are large enough to walk and move through. Operators can check pipes for blockages, ensure pipes are in good condition, and identify potential problem areas that need maintenance. Navigating this environment requires protective clothing and a good sense of direction, as some sewers have pipes built centuries ago and can be both dirty and disorienting to navigate.
The manhole cover is the visible part of the manhole cover that most people interact with. A manhole cover is typically round, to prevent it from falling into the manhole cover and also to make it easier to reposition it when the job is finished, as it is not necessary to match the corners. Also, the rounded edges are less likely to snag on car and bicycle tires. Typically, when a manhole cover is removed to access the utilities below, a protective barrier is erected to prevent people from falling and so that nothing is inadvertently dropped on the worker underground.
Many cities have manhole covers made by a variety of utility companies, which can provide an interesting pictorial history of the utilities operating in the city, along with the progress of industrial design. The front cover is usually made to look somewhat ornamental and also bears the name of the utility that installs it. The covers may be painted or have ornate patterns, and usually have small holes for a worker to insert a pickaxe, a device designed to lift manhole covers.
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