Projects : Redesign of Power Plant Cooling Water Intake Canal

D’Appolonia, a Dynamic Power Technologies Group company, developed designs to rehabilitate a cooling water intake canal at a 700-MW fossil fuel power plant in Austin, Texas. Severe structural distress had occurred in the canal floor due to expansive clays underlying the 420-foot-long, 160-foot-wide by 27-foot-deep structure. Vertical displacements of 12 inches occurred at columns supporting the canal roof and in excess of 24 inches occurred between the columns.

Asian clam infestation in the canal had caused significant impact to the condensers and piping systems of the power plant. Low flow velocities and absence of predators within the intake canal created favorable conditions for clam habitation, growth, and reproduction. Juvenile clams drawn through the screens into the canal grew to adult size and commonly lodged in condensers and firewater lines. Their presence caused unscheduled outages and necessitated frequent maintenance and semi-annual canal cleaning.

Remedial concepts evaluated to control the clams and remedy structural distress included reconfiguring the intake canal to increase flow velocities, and biological, chemical and physical methods to control the clams. Comparisons of alternatives were made considering construction, maintenance, operating costs, and lost production during the outage for repair work.

The selected remedial concept involved installation of side-by-side, 11-foot-diameter concrete pipes in the abandoned canal and connecting new inlet and outlet transition structures at the existing screening and pump intake structures. This eliminated all distressed structures and controlled the clams, as higher water velocities were achieved throughout the system, thus prevent settling of juvenile clams. D’Appolonia designed new 28-foot-high reinforced concrete transition structures and 11-foot-diameter intake pipes. The construction work included demolition of existing canal structures and relocation of two, 24-inch diameter gas lines and a high voltage transmission line crossing the canal.

D’Appolonia provided full-time construction engineering services throughout the $3M rehabilitation project. One unit was available for operation within four weeks of shutdown and the second unit was available within nine weeks.