When the City of Hibbing set out to rehabilitate two trickling filter tanks built in 1938, they faced a challenge familiar to many northern wastewater facilities: aging concrete, harsh freeze-thaw cycles, and the growing impracticality of replacing critical treatment assets.
Hibbing’s trickling filter tanks are 80 feet in diameter and 9 feet tall and have endured nearly a century of northern Minnesota weather. Situated partially above ground, the concrete structures were repeatedly exposed to extreme freeze-thaw cycles, causing widespread cracking and deterioration.
To make matters more challenging, these tanks were originally coated with coal tar, a standard material used in the 1950s before environmental and health regulations phased it out in the late ’90s and early 2000s. Over the years, the coal tar deteriorated, peeled, and trapped moisture against the concrete, accelerating decay.
Replacing both tanks would have required significant downtime, which was something the City simply couldn’t afford. Hibbing needed a solution that would restore the structures without taking the plant offline for years.
Summit Infrastructure, an OBIC-certified installer with a service territory of Wisconsin and Minnesota, became involved after learning Hibbing had already received a bid from another contractor to complete just one tank. After meeting the wastewater operator at the Minnesota Rural Water Conference, Summit offered a better solution that included a complete rehabilitation of both tanks
for just over the cost the city was quoted for one. This approach not only saved the city substantial funds but also provided a fully streamlined, timely rehab solution.
After removing the failed coal tar coating using hydro-blasting (with support from Midwest Infrastructure), Summit selected the OBIC Armor Multi-Layer System for its:
• Superior chemical resistance
• High-density closed-cell foam for added structural enhancement
• 400% elongation to flex with the concrete during freeze-thaw cycles
• SWAT analysis approval, making it ideal for wastewater environments
In northern Minnesota’s climate, flexibility matters. Rigid epoxies often crack under thermal movement, but OBIC’s polyurea system withstands extreme conditions, making it the long-term solution Hibbing needed.
Though temperatures were a primary concern, Summit also managed several technical challenges inside the enclosed dome, while keeping the project moving safely and on schedule:
• Achieving the correct Concrete Surface Profile (CSP)
• Maintaining airflow and moisture control using industrial fans
• Removing and reinstalling filter media to coat several feet below grade
• Working efficiently in a confined space with aging concrete
What the city expected would take two years was completed by Summit in just two weeks. The City of Hibbing was thrilled, not only with the speed of the work but the quality of the finished product. With both tanks restored, the community now has reliable, long-term infrastructure without the cost or downtime of full replacement.
Summit’s work in Hibbing demonstrates their core philosophy to relentlessly protect infrastructure using the highest quality products and the highest installation standards.
Their team prides itself on:
• Delivering durable, sustainable rehab solutions
• Minimizing environmental and operational disruption
• Partnering with trusted certified installers when needed
• Tackling tough projects in tough environments
• Bringing cost-effective solutions to rural and northern communities
With OBIC’s advanced lining systems and Summit Infrastructure’s expertise, the City of Hibbing now has trickling filter tanks designed to perform for future generations, without the risks and costs associated with full replacement.
Learn more about Summit Infrastructure’s service offering or contact OBIC to learn more about becoming an installer.
