Membrane Floor

A highly reinforced, membrane, concrete floor with a slight upward slope to the center of the tank is typically poured in a minimum number of pours. DYK recommends monolithic placement of the floor when possible. However, when the floor cannot be cast monolithically, each floor joint incorporates a waterstop and only galvanized or epoxy coated bars are allowed to span the joint.

Often in wastewater tanks the floor will slope to the center making a conical hopper bottom. This facilitates collection and removal of sediment at the center sump.

Connection of Floor, Wall, and Roof

To provide an unrestrained connection and to reduce bending moments induced by hydrostatic, thermal, backfill and seismic forces on the tank wall, the roof and floor are separated from the corewall by neoprene bearing pads.

This "free-sliding" connection at the wall base and wall top enhances the seismic performance of the tank by allowing the floor, wall and roof to act independently of each other. A continuous PVC bulb waterstop between the floor and wall assures full liquid tightness of the joint.

Circular Cast-in-Place Concrete Walls

Wall forms are carefully curved to the radius of the tank. The cast-in-place concrete corewall is cast continuously full height and in equal circumferential sections, usually about 40 ft in width.

Vertical prestressing tendons are cast inside the wall to provide compression that counteracts the effects of differential dryness and thermal loads. To expedite construction, the walls and columns are completed concurrently.

Flat Slab or Free-Span Concrete Dome Roofs

A concrete, two-way, flat slab roof with a slight upward slope to the tank's center is cast in the minimum number of pours, similar to the floor. A grid of equally spaced round columns supports the flat roof. Free-span concrete or aluminum dome roofs can also be used. Use of a dome roof will eliminate all the interior columns, as the dome is entirely supported by the tank wall.