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Why is Manhole Rehabilitation Important

When considering the rehabilitation of sewer infrastructure, it’s important to not forget the manholes. Manhole rehabilitation is one of the most cost-effective aspects of rehabilitating a sewer system.

 

Manhole Rehab is Crucial in Today’s Sewer Infrastructure

When considering the rehabilitation of sewer infrastructure, it’s important to not forget the manholes. Manhole rehabilitation is one of the most cost effective aspects of rehabilitating a sewer system. In general, rehabilitation is divided in three categories; mainlines, laterals and manholes.

 

Mainlines

Mainlines are typically the first area that are inspected and eventually rehabilitated. Sometimes the inspections are driven by reacting to issues that happen in the mainline pipe such as backups and overflows. These issues trigger the owner to inspect the problem areas which will typically end up being rehabilitated.

 

Laterals

An owner may also choose a more proactive approach and set up certain basins to be scheduled to inspect and assess. The rehabilitation for these areas may be able to be planned out and put on yearly rehab contracts.

 

Manholes

The same goes for the manholes. Some manholes are inspected as a result of deteriorated pavement near the manhole or sink holes or sunken areas that are indicators that the manholes are in need of rehabilitation. An owner may also choose to set up a proactive manhole inspection program. This approach may result in finding problems early before they affect their surroundings.

 

When to Consider Manhole Rehabilitation

Manhole rehabilitation should be considered when the manhole experiences one or more of the following;

  1. inflow and/or infiltration (I&I)
  2. corrosion
  3. structural issues

 

1. Inflow/Infiltration

Inflow and/or infiltration is the biggest reason that manholes are rehabilitated. Inflow is water that enters the manholes during a rain and shortly after the rain subsides. Inflow enters in the easy pathways into the manhole such as vent holes in the cover, poor or deteriorated chimneys.

Infiltration is water that enters the manhole about 20 minutes after the rain has stopped. Infiltration takes a harder path to enter the manhole such as percolating through the ground to find a way to enter around a pipe or a joint. The excess water that enters the sewer system can be eliminated with proper rehabilitation methods.

It’s important to remove the water since treating excess water is expensive over time. Rehabbing the manholes can save hundreds of thousands of dollars over the lifespan of a sewer.

 

2. Corrosion

Since the majority of manholes are made of masonry construction or precast concrete they are susceptible to microbially induced corrosion (MIC). Corrosion is caused by bacteria that consume sulfides and metabolize sulfuric acid which corrodes concrete and the mortar in between bricks

If left alone the manhole could collapse and cause major sewer backups and disruption on the street level. Proper rehabilitation methods can stop corrosion and prevent further deterioration.

 

3. Structural Issues

Over time manholes may develop structural issues for a variety of reasons such as traffic loading, subterranean movement, freeze thaw, corrosion, and I&I. These conditions if not resolved can result in severe problems with the manholes.

Soil around the manhole may feed into the fractures and joints and deteriorated sections and cause large voids under pavement which can result in large sinkholes that in some cases are large enough to fit cars into.

Manhole rehabilitation can structurally enhance the manhole and prevent these problems from happening.

 

Summary

Overall developing a program to inspect, assess and rehabilitate manholes will save money and prevent dangerous situations within the sewer infrastructure.

 

To learn more about manhole rehab, sign up for a FREE educational session by going to the following link here.

 

If you have any questions about anything CIPP, or NASSCO training, our helpful team will be happy to answer any of your questions.

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