Tunnel Dewatering Pumps Make Debut

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Five large tunnel dewatering pumps have been delivered to the Blue Plains Advanced Wastewater Treatment Plant for installation on the Tunnel Dewatering Pump Station and Enhanced Clarification project under construction by the PC Construction/CDM Smith joint venture. Each pump is powered by a 3,000 hp electric motor, each of which are made in Italy and shipped via container ship to the Washington, DC site. The pumps are located at the bottom of a 160-foot deep pump station which is at the end of a large tunnel system running under the nation’s capital.  Excess storm water is diverted into the tunnels, flows down to the pump station and is then pumped up to ground level where it is treated.  Each pump is capable of pumping 58,000 gallons per minute or 83 million gallons per day, lifting the water approximately 140 vertical feet to ground level where it is treated and then flows into the Potomac River.

This $215 million design-build project includes a 500-mgd tunnel dewatering pump station and 225-mgd enhanced clarification facility. The project features a ballasted flocculation clarification process, including ACTIFLO® high-rate clarification process, fine screens, grit removal and disinfection and dechlorination facilities. Work includes the conversion of a deep shaft measuring 132 feet in diameter by 159 feet deep as well as a secondary shaft measuring 76 feet in diameter by 130 feet deep. The construction will allow for future expansion capabilities of the clarification process to 500 mgd.