Despite tough site constraints, a project team achieved concrete placement rates of up to 300 cubic yards per hour for the floor and roof slabs of a 208-foot-diameter, 30-foot-tall concrete clearwell for Semper Water Treatment Plant, Westminster, Colo. Because post-tensioning of each slab needed to begin within 32 hours of concrete placement, all the concrete for each slab had to be placed within five hours to ensure fairly uniform compressive strengths. STRATEGIC PUMP LOCATIONS Clearwell construction required a total of 3,200 cubic yards of concrete, including 750 cubic yards for the floor slab and 1,050 cubic yards for the roof slab. Four concrete pumps--two 52-meter and two 42-meter models--were used for each placement, allowing crews to achieve the high output rates. The pumps were strategically placed around the site perimeter, so each machine could reach a quadrant of the work area without requiring relocation. An on-site dispatcher communicated by radio to field representatives stationed at each pump to route ready-mix trucks to pumps that needed more concrete.