Cascading River Outfall Structure for Cooling‐Water Discharge System

An innovative cascading spillway was selected to replace a reinforced concrete slab/discharge pipe river outfall structure, which required frequent maintenance and subsequently collapsed as a result of scouring and piping action of cooling water discharging from a power plant. The cascading design was adopted because the structure is located on the bank of the Mississippi River, which has an annual fluctuation of water levels as much as 45 ft (13.73 m). To facilitate the construction of the spillway, low‐water duration of the river dictated the method of construction and materials to be used. As a result, a cascading steel sheet piles cellular structure, forming a series of stepped basins, was adopted with concrete used as the base of the basin. The new, practically maintenance‐free, stable structure was completed within a two‐month period and resulted in a substantial savings as compared to the replacement cost of the collapsed structure.