When the owners of Toad’s Cove, a gas station and convenience store in Trempealeau, Wis., decided to add a car wash to their business, they quickly realized having only a septic system and no sewer made the project difficult. They needed to choose a car wash system that did not place dirty or clean water in the septic system and reduced the amount of fresh water used. The solution was investing in an AQUA BIO Technologies water restoration system that allowed them to recycle and reuse 90 to 95% of their wash water. This was accomplished with several large precast concrete settlement and treatment tanks that were supplied by Crest Precast.
Steve Mader, owner of Crest Precast, said each tank measured 8 feet by 8 feet. They were manufactured using 7,500-psi concrete and a standard utility box mold, which eliminated the need for metal wall ties. A 10,000-gallon holding tank was also manufactured to provide an emergency water supply if needed.
“What we do is cast the floor slab with protruding rebar and waterstops,” Mader said. “Next, we set the box mold over the rebar cage with proper rubber boots and pour the vaults in a seamless box, making sure they are watertight.”
The interior of the settlement tanks have a standard precast sand trap with a perforated steel baffle to stop floating debris from entering the recycling tank. Mader added that all vaults are fully accessible for maintenance with a 3-foot-by-3-foot hatch door and that a Penetron admixture was added to the mix design to provide additional watertightness.
According to Tom Gibney, president of AQUA BIO Technologies, precast is the preferred material for manufacturing the tanks. The bio chamber, which is where aerobic bacteria remove the wash chemicals, can have variable heights and widths to accommodate the form the precaster has available, but the depth needs to be precise.
“Precast is the perfect choice for this project,” Mader said. “They are placed below ground, fairly deep and are indestructible from the added pressure from side loadings and building footings.”