UV CIPP Scales Up for Large-Diameter Culverts

Across the nation, thousands of large-diameter culverts installed decades ago now sit beneath highways, railways, and other critical roadways. Many were built from corrugated metal or early concrete systems that are reaching or exceeding their design life.

Large-diameter culverts are among the most challenging drainage assets to address. Their size, location beneath critical infrastructure, and role in preventing roadway overtopping make full replacement costly and disruptive. In addition, excavation often requires extended closures, traffic control, embankment disturbance, and environmental permitting — factors that can outweigh direct construction costs. Trenchless rehabilitation avoids these risks and minimizes disruption.

UV CIPP Demo

Last November, ProKASRO USA conducted a first-of-its-kind demonstration to rehab an 84-in. diameter corrugated steel pipe using ultraviolet light cured-in-place pipe (UV CIPP) technology. The demonstration was held at HammerHead Trenchless in Lake Mills, Wisconsin. It validated the feasibility, efficiency, and constructability of UV CIPP at this scale.

Prior to this project, UV CIPP had been successfully applied to smaller culverts. However, the absence of larger liners limited its use. For this demonstration, a new UV system was used to cure an 11.8-mm thick liner constructed by IMPREG USA. After resin impregnation, the liner weighed 7,700 lbs. The liner can be customized to meet project-specific structural demands.

To accommodate the liner and curing requirements, 70-in. aluminum packer cans were designed and fabricated. The UV system used a triple jumbo core containing 18 lamps, each rated at 2,000 watts, delivering a combined output of 36,000 watts. The liner was installed and cured in a 60-ft pipe segment at 0.8 feet per minute. This resulted in a total lamp run time of about 65 minutes from start to finish. Typically, field installations allow additional time for inspection and cleaning prior to lining.

The demonstration confirmed that UV-curing provides a consistent, controlled cure across the full circumference of a large-diameter liner. This is essential for predictable structural performance.

Successful Completion

The successful demonstration of this 84-in. diameter pipe confirmed several critical benefits of UV CIPP for large-diameter applications:

• Efficiency: Rapid curing significantly reduces installation time compared to full replacement and many alternative rehabilitation or heat-cure CIPP methods.
• Cost-Effective: Avoiding excavation, traffic control, embankment restoration, and long cure times substantially lowers total project cost, particularly when indirect impacts are considered.
• Smaller Footprint & Safer Worksite: Minimal equipment and staging reduce site congestion, safety risks, and disturbance to surrounding infrastructure.
• Environmental Advantages: Trenchless installation, lower energy use, no discharge of cure water, and shorter construction duration minimize impacts to soils, waterways, and sensitive habitats.
• Structural Reliability: Controlled UV-cure ensures uniform material properties, critical for large-diameter, high-consequence culverts.

This demonstration confirms that UV-cured CIPP is a viable, efficient, and cost-competitive solution for rehabilitating culverts up to 84 in. in diameter. Infrastructure owners now have a proven method to restore structural integrity. They can do so while avoiding the disruption, risk, and environmental impacts associated with full replacement.

As agencies face aging infrastructure, increasing storm intensity, and constrained budgets, large-diameter UV CIPP offers a practical path forward. It preserves critical drainage assets with a smaller construction footprint, reduced environmental impact, and faster return to service. This case study demonstrates that UV-cured CIPP is no longer limited by size. It is positioned to play a central role in the future of large-diameter culvert rehabilitation.

Steve Wierzchowski is a NASSCO member and a senior manager with Pro KASRO USA / HammerHead. Trenchless.

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