By: Contech Engineered Solutions
NCSPA Retention/Detention Project of the Year Winner
When Louisville’s airport needed more parking, the solution wasn’t just more pavement. Behind the scenes, the real MVP was a massive underground corrugated metal detention system designed to manage stormwater without taking up valuable surface space. That innovation helped this project earn top honors as NCSPA’s Retention/Detention Project of the Year.
More Cars, More Asphalt, and a Lot More Water
Back in 2020, the Express Shuttle Parking Lot at Louisville Muhammad Ali International Airport opened with 974 spaces. It didn’t take long for demand to spike. By 2024, airport leaders approved a $5.3 million expansion to add over 1,000 more parking spots. That came with a major challenge: managing runoff from all that new asphalt.
Since there wasn’t room for an above-ground basin, the team needed a reliable underground corrugated metal detention system that could handle large volumes of stormwater efficiently and discreetly.
Solid Design for a Tight Site
Engineers from Foth Infrastructure worked with Contech to develop a customized underground corrugated metal detention system that offered both performance and durability. They installed 6,328 linear feet of 66-inch solid-wall pipe, creating 150,344 cubic feet of underground storage.
Because the system was located near an embankment, a perforated pipe layout with stone backfill was ruled out to avoid infiltration issues. Instead, the team chose solid pipe with flat gaskets, which allowed for tight joints and a watertight design. The system also included 31 stepped rows and 31 bulkheads to maintain stability across the site.
Pretreatment That Keeps Things Clean
One standout feature of this underground corrugated metal detention system is its built-in water quality pretreatment. A Cascade Separator unit was placed upstream to remove sediment, trash, and debris before they reach the main storage area.
This design reduces the need for frequent maintenance by capturing everything in one accessible unit. It’s a smart addition that saves time and ensures long-term performance, especially important in a high-traffic airport setting.
From Falling Behind to Finishing Ahead
Even though the project began with delays, the construction team pulled off an impressive recovery. Flynn Brothers Contracting, working alongside Contech, delivered the underground corrugated metal detention system ahead of schedule.
Crews managed daily deliveries of up to nine truckloads of pipe. They used excavators to position the pipe, skid steers to backfill between rows, and compacted in balanced lifts. To protect the system during installation, they temporarily raised the cover height with a makeshift road that was later returned to grade.
Why This Project Stands Out
In the end, this underground corrugated metal detention system helped the airport meet increasing parking demand while protecting the site from stormwater issues. It was a creative, efficient solution that didn’t require sacrificing surface space or cutting corners on quality.
The Louisville Shuttle Lot project proves how flexible and powerful corrugated steel can be when paired with smart engineering and a trusted team. That’s what made it a standout winner in this year’s NCSPA awards.
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