Winner: Sustainable

In 2024 and 2025, Vanguard Renewables constructed a Digester Tank (3 million gallons), Hydrolysis Tank (330,000 gallons), and Digestate Storage Lagoon (395 feet long by 255 feet wide by 26 feet deep and 12 million gallons) in River Falls.

Even though this project was located on the Peterson Farm, this infrastructure primarily processes food waste from industrial facilities that would otherwise go into landfills.  It then creates renewable natural gas, which is put into the natural gas grid.

The three structures consisted of approximately 3,500 cubic yards of concrete and 291 tons of reinforcing steel.  Due to the aggressive chemical nature, the concrete for the digester included an integral crystalline waterproofing admixture to increase its durability.

This was crucial during leak testing, as the admixture sealed any weeps or hairline cracks that would’ve allowed water to pass, preventing the need for repairs.

Other challenges included sandy subsurface soils drawing water from the 0.42 water cementitious concrete and winter conditions during the placement of the digester.  Lastly, the structures are all constructed in compliance with ACI 350.