C+S September 2022 Vol. 8 Issue 9 (web)

Manholes frequently experience degradation and cracking. Corrosive chemicals and gasses, extreme temperatures, and shifting earth and wa- ter 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 ag - gressive 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 rehabilita- tion 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 cor- rosion 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 ben- efits 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 rehabili- tations 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 be- tween the liner and walls and slowly degraded the structure of the pipe. Although the degradation was extreme, a full replacement was un- necessary. The compromised manholes were repaired with a 100 per- cent 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 cor- rosion and leakage. Rehabilitating degraded manholes for long-term protection— even in harsh conditions By Andrew Gonnella

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. With- out intervention, they would continue to deteriorate and ultimately fail. To avoid the cost and disruption of replacing the manholes, a com- prehensive 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.



September 2022

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