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Tunnel Dewatering Pump Station and Enhanced Clarification Facility

Tunnel Dewatering Pump Station

Project Completion

50

Two key components of DC Water’s Nitrogen Removal/Wet-Weather Program include the Tunnel Dewatering Pump Station (TDPS) and Enhanced Clarification Facility (ECF).

This project starts where the massive DC Clean Rivers Project tunnels end at Blue Plains. In 2018, when the Blue Plains Tunnel is brought online, the Tunnel Dewatering Pump Station (TDPS) and Enhanced Clarification Facility (ECF) will accept the millions of gallons of combined sewage that previously flowed into the District's waterways during heavy rain storms. That flow will now receive treatment.

Principal components include:

■    Complete treatment for up to 555 mgd for the first four hours during combined sewer system conditions or wet weather event, and 511 mgd thereafter.
■    A 225 mgd ECF is being constructed to treat captured wet-weather flows from the tunnel in addition to providing a higher level of treatment.
■    A new Tunnel Dewatering Pump Station equal to the capacity of the ECF with sufficient capacity to dewater the tunnel system.

The TDPS will pump the collected combined sewer overflows (CSOs) from the Blue Plains tunnel to the ECF for treatment. The ECF process will consist of fine screening, grit removal, and a ballasted flocculation process, followed by disinfection and dechlorination prior to discharge to the Potomac River or to secondary treatment.

Notice to Proceed was issued in August 2014 and the project will be completed in 2018.