Expansion in the city of Madison, Wisconsin brought about the need for an upgrade to the Nine Springs Wastewater Treatment Plant. The city hired the consulting firm of Applied Technologies of Brookfield, Wisconsin to develop a design for the expansion. The expansion required two Acid Digester Tanks to complete the process. After researching the available alternatives, Applied Technologies decided to specify an AWWA D110 Type III prestressed concrete storage tank because of its durability and negligible maintenance requirements. Preload was chosen as the preferred firm to design and construct the storage tanks.
The tanks feature a 24″ thick sloped (2V:12H) conical floor, cast-in-place concrete baffle wall ribs attached to the interior precast concrete tank wall, and required that the 3-story pump house be connected to the exterior wall of each tank. Preload designed and built flexible connections between the pump house and the tanks to accommodate both differential settlement between the pump house and the tank structure and movement of the tank wall during filling and emptying of the tanks. The tanks also feature architectural treatment which was chosen by Applied Technologies and the architect to match the pump house structure.