Manholes are access points in streets, sidewalks, or other public areas that provide access to underground utility systems, such as sewers, storm drains, and electrical, gas, or water lines.
They are typically circular or rectangular openings in the ground, covered by a heavy metal lid that can be removed to provide access to the utility system below.
Purpose of manholes
Access and Maintenance: One of the primary purposes of this type of structure is to provide access to underground utility systems for maintenance, inspection, and repair. Workers can use manholes to reach pipes, cables, and other components that are buried underground.
Inspection and Cleaning: It allows workers to inspect and clean underground infrastructure, helping to prevent blockages, leaks, and other issues. They also provide a way to monitor the condition of utility systems over time and identify potential problems before they become serious.
Stormwater Management: Some manholes are designed to manage stormwater runoff, allowing water to enter the storm drain system and preventing flooding on streets and other public areas.
Types of manholes
- Shallow Manhole: It is typically less than 1.5 meters (5 feet) deep. These are often used for systems with shallow pipelines, such as stormwater or small sewage systems.
- Normal Manhole: A normal manhole is typically between 1.5 to 3 meters (5 to 10 feet) deep. These are commonly used for sewage, stormwater, gas, water, and other utility systems.
- Deep Manhole: A deep manhole is typically deeper than 3 meters (10 feet). These are used for systems with deep pipelines, such as large-diameter sewage or water pipelines.
Materials used in the construction of manholes
- Concrete
- Steel
- Brick
- Fibreglass
- Plastic
- Cast Iron
Concrete: Concrete is the most common material used in the construction of manholes. It is durable, strong, and resistant to corrosion, making it ideal for use in underground utility systems.
Steel: Steel is a strong and durable material that is used for manholes in areas where there is a risk of corrosion or damage from chemicals. It is often coated with materials that resist corrosion.
Brick: Brick is a traditional material that is still used in some older sewer and stormwater systems. It is strong and durable and can be used to create custom designs.
Fiberglass: Fiberglass is a lightweight, corrosion-resistant material that is used for manholes in areas where there is a risk of damage from chemicals, such as in wastewater treatment plants.
Plastic: Plastic manholes are becoming increasingly popular because they are lightweight, easy to install, and resistant to corrosion. They are often made of high-density polyethylene (HDPE) or polypropylene.
Cast Iron: Cast iron manholes are sometimes used in older systems, although they are less common today. They are durable and resistant to corrosion but are heavier and more difficult to install than other materials.
Location of the Manholes
The location of manholes is an important consideration in the design and installation of underground utility systems. Here are some general guidelines for the location of manholes:
1. Accessibility: It should be located in areas that are easily accessible for maintenance and repair. They should be located in areas where vehicles can safely and easily access them, and should be positioned to avoid obstructing traffic or pedestrian flow.
2. Slope and Elevation: It should be located at the low points in the pipeline system to allow for gravity flow of the wastewater or other materials. They should also be installed at appropriate elevations to ensure proper flow rates.
3. Changes in Direction and Gradient: It should be located at changes in direction or gradient in the pipeline system. This can help prevent blockages and ensure that the flow of wastewater or other materials is not impeded.
4. Junctions and Intersections: It should be located at pipeline junctions and intersections to allow for easy inspection and maintenance of these areas.
5. Proximity to Structures: It should be located at a safe distance from other structures, such as buildings, walls, or retaining structures. This can help prevent damage to these structures and ensure the safety of workers and the public.
Maintenance Of Manhole
Here are some important maintenance practices for manholes:
1. Regular Inspections: It should be inspected regularly to check for any damage or signs of wear and tear. This can help identify potential problems early and prevent more serious issues from developing.
2. Cleaning: It should be cleaned regularly to remove debris and sediment that can accumulate over time. This can help prevent blockages and ensure that the flow of sewage or other materials is not impeded.
3. Repairs: Any damage to this structure, such as cracks or leaks, should be repaired promptly to prevent further damage and to ensure continued functionality.
4. Odor Control: It can sometimes produce unpleasant odors, especially in hot weather. Proper odor control measures, such as using odor-reducing chemicals or installing ventilation systems, can help mitigate this issue.
5. Safety Measures: It can be dangerous, particularly when they are being opened for maintenance or repairs. Proper safety measures, such as barricades and safety equipment, should be used to prevent accidents and ensure the safety of workers.
6. Record Keeping: Keeping accurate records of manhole inspections, maintenance, and repairs can help identify patterns and potential issues over time, and can also help ensure compliance with local regulations.
