DC Water's Rapid Repair of a Waste Water Treatment Plant Piping System

The Blue Plains Advanced Wastewater Treatment Plant owned by District of Columbia Water and Sewer Authority (DC Water) is one of the largest wastewater treatment plants in the world. One particularly critical pipe within the facility is the Nitrification RAS Line, which transports sludge and is located in underground galleries. Through inspection it was identified that eight elbow sections of the 84-in. steel pipeline had significant thinning and were in need of repair during the scheduled 2013 pipeline shutdowns. Four 90-degree elbows and four 45-degree elbows required a structural upgrade, and CFRP was selected as the appropriate structural lining system based on DC Water's previous successful history with this material. The EPA regulates the amount of time this facility can be shut down and dictates that only half the piping can be shut down at one time, so the cleaning, inspection, weld repairs, CFRP and topcoat installation, along with full cure of the repair system had to take place over the course of two five-day shutdown windows. This paper will provide details and owner feedback on the design and construction process undertaken for this unique project.