Manhole Rehab by USG: Why and How?

Manholes play a critical role in infrastructure by giving workers access to the systems that are hidden beneath the ground. Just like any structure, over time they can begin to degrade. But why? And what can be done about it? In this article, we’ll discuss some of the reasons that manholes become damaged and how our team at USG can fix them with our Manhole Rehab service.

Problem Signs for Manholes

Manholes may be underground, but they should still be monitored for signs of deterioration. Here are some problem signs that manholes may experience:

• Inflow and Infiltration (I&I): Many manholes begin to experience inflow and infiltration through the walls as grout between bricks degrades. Pre-cast manholes typically leak at barrel section joints and pipe penetrations. I&I can accelerate deterioration and additional groundwater that needs to be treated.
• Exfiltration: Exfiltration is when water or wastewater escapes out of infrastructure in a way that was not intended. This may happen through joints, degraded grout between bricks, missing bricks, cracks, or failed pipe penetrations. The water/wastewater from inside the manhole or the pipes attached to it may escape into soil or groundwater, potentially causing voids to develop and could potentially lead to permit violations if left unattended.
• Cracks Around the Manhole Cover: Cracks in the concrete or asphalt that surrounds the manhole cover could indicate that the structure is experiencing distress below the surface. These cracks may point to voids in the soil that surround the manhole and may be happening because of soil loss caused by infiltration. Additionally, manholes often leak surface water around the frame to the manhole interface if not properly sealed.
• Hydrogen Sulfide (H₂S) Attack: In some sewer systems—especially those with force mains—manholes may be exposed to hydrogen sulfide gas. This gas forms under anaerobic (oxygen-free) conditions and is released when sewage enters an open environment. Over time, hydrogen sulfide can aggressively corrode concrete and metal, leading to structural damage inside the manhole. Left unchecked, it can lead to complete failure of the structure. Even brick manholes are not immune- because the grout holding everything together also gets attacked and eventually fails.

Manhole Assessment

The most important aspect of manhole rehabilitation is to complete an assessment first. USG utilizes a series of assessment techniques based upon the possible problem, budget of system owner, and industry standards. NASSCO Level I assessments are the minimum that should be completed. This identifies just the basics and can be a great place to start. Level II is more in depth, but comes at a significantly higher cost and time investment. Often, our team will blend a Level I and Level II assessment to stretch your budget further without compromising quality. This incorporates the details of a Level II assessment while focusing on rehab needs. Once this has been identified, you can move forward with manhole rehabilitation.

Methods of Manhole Rehab

The useful lifespan of a manhole can be extended when they are maintained and repaired as needed. Once the right assessment has been done, the proper fix can be determined. Some of these fixes include:

• Polyurethane Injection: Polyurethane injection is a method of manhole rehabilitation that can help seal them from leaks and fill voids in the soil that surrounds them. During this kind of repair, testing is conducted to locate leaks and voids. After that, injection holes are drilled around the surface of the manhole, injection rods are placed. Through the rods, polyurethane is injected, moving as a liquid and setting up around the structure as a foam. Depending on what the structure needs, our team may use single or dual component polyurethane. Single components are great for leak sealing, and dual components are great for filling voids in the surrounding soil.
• Cement Lining: Another method to rehabilitate manholes is cement lining. Using high strength fiber reinforced micro-silica cement products, a new surface can be sprayed on the inside of the manhole. Cement Liners may be sprayed or spin-cast to the walls, creating a dense material up to 1 inch thick in single application. This liner also helps seal out I&I, restore structural integrity, and restore structural cross section of the manhole.
• Epoxy Lining with EpoxyTec™: For manholes needing H₂S protection, 100% solid, structural epoxy is a great choice. Once the manhole is prepared after high pressure water blasting, the epoxy is sprayed on the inner walls of the manhole. This product seals and reinforces the structure, and creates a barrier to stop hydrogen sulfide from eating away at the cement. EpoxyTec™ CPP MH also creates an interior barrier that is able to resist hydrostatic pressure from the outside, in the event that infiltration continues after installation is completed. The product is high build and able to be sprayed up to 375 mils in a single coat. Using this method, the manhole can be restored to service within hours of installation. It’s also forgiving enough during application to be able to handle the wet environment of a manhole.
• Composite Systems: A composite system is a unique combination of both cement and epoxy liners. It addresses all the possible needs of a manhole rehabilitation project. First the cement is placed to re-profile the manhole and restore structural integrity, then EpoxyTec™ to ensure long use life and prevent further H₂S attack.

At Utility Services Group, we understand the importance of keeping underground infrastructure in safe, working condition. We also know that the right product of solution can only be selected after careful consideration as to the cause of the failures. Therefore, it is critical to employ trained and certified crews when performing assessment or rehabilitation. All USG assessment crews are MACP NASSCO Certified to aide in structure inspection. Our manhole rehab crews are also E-Can certified, a rigorous training provided by Epoytec™. It ensures proper application and installation of all the Epoxytec™ and Tnemec™ (the Epoxytec™ parent company) products. Whether the issue is groundwater infiltration, hydrogen sulfide attack, or structural damage from surrounding soil loss, our team has the tools and expertise to restore failing manholes without the need for full replacement.
Using non-invasive and trenchless techniques, we help municipalities, facility managers, and utility owners preserve aging infrastructure, minimize environmental impact, and avoid costly emergency repairs. If you’ve noticed signs of deterioration in your manholes—or want to proactively prevent issues before they arise—contact USG to schedule a consultation or learn more about our Manhole Rehab services.