Rehabilitating degraded manholes for long-term protection— even in harsh conditions

By Andrew Gonnella

Manholes frequently experience degradation and cracking. Corrosive chemicals and gasses, extreme temperatures, and shifting earth and water presence all take a toll on manhole integrity. Initially, the preferred solution may appear to be to replace the damaged section, rather than risking the ability of rehabilitated materials to withstand the most aggressive environments.

However, strategies exist to successfully smooth and seal finishes and provide structural support to resist corrosive liquids, infiltration and inflow, and freezing weather and thaws. Rehabilitation is typically faster and thus less disruptive than full replacement – assuming the rehabilitated components are reliable. A turnkey manhole rehabilitation solution can ensure that all issues within a manhole are repaired, preventing continued leaks and corrosion.

Rehabilitation starts with the application of products such as grouts, patching materials and cementitious mortars to stop leaks, fill voids and enhance structural integrity. Once a durable foundation has been provided, the next step is the introduction of a 100 percent solid epoxy coating specifically formulated for long-term protection and structural stability for wastewater infrastructure subjected to high levels of corrosion and abrasion.

Used for both interior and exterior pipe lining, a solid epoxy coating such as Structure Guard® provides a smooth finish, resists chemical degradation, repairs and prevents cracking, restores structural integrity and cures quickly to enhance flow and reduce downtime. These benefits are vital for reliable manhole rehabilitation regardless of location. The strengthened foundation complements the epoxy lining, ensuring a complete repair solution. This approach has led to successful rehabilitations in a wide variety of locations.

Enhancing corrosion protection when faced with H2S

In a routine inspection, an Arizona Public Works Department found that 10 sanitary sewer manholes suffered from excessive corrosion from years of H2S gas exposure. Over time, H2S gas had migrated between the liner and walls and slowly degraded the structure of the pipe.

Although the degradation was extreme, a full replacement was unnecessary. The compromised manholes were repaired with a 100 percent solid epoxy coating, rather than polyurethane. The 10 manholes were cleaned, prepped and lined with the epoxy, which was applied to a 250 mils thickness to provide maximum protection against corrosion and leakage. 

The project took two weeks to complete with minimal community disruption. Residents experienced just four hours of system downtime each day. Correcting the issue saved the city thousands of dollars and avoided the time and inconvenience associated with digging up and replacing the damaged manholes.

Stopping corrosion, infiltration, and inflow over the long term

The Ak-Chin Indian Community of the Maricopa Indian Reservation in Arizona had several pre-cast concrete sanitary sewer manholes that were suffering from inflow, infiltration, and severe H2S damage. Without intervention, they would continue to deteriorate and ultimately fail. 

To avoid the cost and disruption of replacing the manholes, a comprehensive three-step rehabilitation approach was utilized. First, leaks were addressed with a polyurethane chemical grout and a rapid-setting, patching water stop material. Second, a structural cementitious mortar was applied and cured to bolster the foundation. Finally, a 100 percent solid epoxy was added to further protect the manholes from corrosion and leaks. Once fully cured, the new corrosion- and leak-proof lining added more than 50 years of design life to each manhole.

Withstanding harsh winters

Extremely cold, harsh winters in South Adams County, Colorado, caused multiple manholes to suffer severe deterioration, infiltration and inflow. Without repairs, the inflow and infiltration would continue to affect the system and ultimately increase the cost of wastewater treatment. If the manholes were not structurally restored, the risk of collapse, sinkholes, and emergency repairs would significantly increase.

The extensive damage required multi-step corrective action, made more challenging by extremely cold weather during the installation phase. To address the loss of structural integrity, the manholes were first lined with a cementitious mortar known for its structural restoration properties. A 100 percent solid epoxy was then applied at a thickness of 125 mils for added corrosion protection. The resulting adhesion levels exceeded expectations, providing clean and smooth finished manholes despite the weather conditions during installation.

Preventing infiltration of diesel fuel

A train yard in Michigan experienced a diesel fuel spill that required immediate attention. To keep the fuel from flowing to the nearby river, a contractor was hired to assess and re-line the storm drainage system. After experiencing initial challenges with the application of a cementitious liner by a subcontractor, the contractor sought a different approach to address the leaking manholes and catch basins.

A 100 percent solid epoxy offering exceptional bond strength and long-term chemical and corrosion resistance was recommended to address and eliminate the potential environmental hazard. To plug the leaking voids and cracks, a fast-setting water stop product was also required. The issues with the original approach were addressed and the job was completed in just one week. Once finished, the newly lined manholes and catch basins were tested for infiltration and exfiltration. In each case, they exceeded testing standards.

Rehabilitation often the preferable choice

When paired with other repair solutions, a 100 percent solid epoxy such as StructureGuard delivers enhanced capabilities and longer-lasting effects. Its compatibility with other materials, including Quadex® grouts, and repair solutions makes it a preferred choice for the rehabilitation of pump stations, treatment plants and wastewater infrastructure elements that are subjected to high levels of corrosion and abrasion in both municipal and industrial applications. 

Selecting manhole rehabilitation and repair rather than replacement provides asset owners reduced costs and a significant reduction of project time while minimizing disruption to the surrounding community. By using an effective, long-lasting product that can withstand a range of harsh conditions and elevate the performance of other materials, asset owners and installers can benefit from simplified expenses, logistics and project schedules while achieving greater performance.

Andrew Gonnella is President, Products Division for Vortex Companies. In this role, he oversees the development and expansion of Vortex’s existing product line, identifies new products and develops new distribution channels. He holds a Bachelor of Arts degree from University of Maryland College Park and a Master of Business Administration from University of Maryland Robert H. Smith School of Business.