Why Manhole Maintenance Matters More Than You Think
Most people rarely give much thought to manholes, but they play an essential role in keeping urban life running smoothly. With around 20 million manholes spread across the U.S., each serving as a critical access point for utilities like water, electricity, and gas, maintaining these structures is vital to the functionality of our cities. Unfortunately, many manholes are neglected during routine maintenance, leading to significant degradation. Studies show that nearly 20% of manholes in the U.S. are over 30 years old, with more than 3 million requiring urgent repairs or complete replacement due to structural issues.
In Pima County, Arizona, a case study highlighted the consequences of poor maintenance. Twenty-one manholes built in the 1940s had previously been lined with a competitor’s cementitious material, which eventually failed. Over time, this lining eroded, losing its grip on the underlying structure and shedding fragments into the sewage flow. This posed a serious risk to the county's wastewater treatment system. To address the problem, the county decided to remove the damaged liner, reinforce the manholes, and protect them from corrosive gases like hydrogen sulfide.
The rehabilitation project proved both efficient and cost-effective. HJ3’s carbon fiber solution saved the county a staggering 80% compared to the cost of replacing all 21 manholes. What’s more, the repair work was completed without any road closures, saving countless hours of downtime and preventing the unnecessary waste of nearly 62,000 gallons of water typically required to produce new manholes.
The process began by carefully grinding down the eroded lining. Next, the team resurfaced the concrete with Quick-Set grout and sealed all cracks using a low-viscosity polymer. HJ3’s CarbonSeal™ carbon fiber was then applied to strengthen the structure, followed by a protective vinyl ester topcoat to shield against future erosion caused by hydrogen sulfide gas.
This approach not only extended the lifespan of the manholes but also ensured the safety and reliability of the entire sewer system. The success of this project underscores the importance of proactive maintenance for infrastructure that often goes unnoticed—until it fails.
The failed cementitious liner that was originally installed in 1996.
HJ3’s CarbonSeal™ being applied to the interior of the manholes.
The final vinyl ester topcoat protects the manholes from hydrogen sulfide gas and future wear.
By investing in solutions like HJ3’s carbon fiber system, municipalities can avoid costly replacements while ensuring their infrastructure remains resilient and functional. It’s a small step that yields big returns—not just for Pima County but for communities everywhere.
