The DC Water Board of Directors recently approved one of the largest contracts in the Authority’s history, for the design and construction of facilities that will reduce nitrogen discharge to the Potomac River and Chesapeake Bay as well as bring relief from combined sewer overflows (CSOs) to the District’s waterways.

It is a design-build contract, a type growing in popularity for its ability to save time and money and create greater cooperation between contractor and owner. A Joint Venture of PC Construction and CDM Smith (PC/CDM Joint Venture) won the contract, estimated at nearly $215 million, based on a proposal that received the highest technical score and was the lowest cost.

When DC Water’s new permit limits for 2015 were first announced, DC Water analyzed possible solutions for lowering nitrogen to the required levels. The first proposal called for adding more nitrogen removal at Blue Plains and would have meant stacking treatment tanks on top of the existing ones. Instead, this innovative solution stores flow in the CSO tunnels so that even during peak flow (during wet weather) the flows can receive treatment. This design saved roughly $500 million.

The tunnel dewatering pump station is a complex pumping facility that will be built into the shaft that currently serves as an entrance to the tunneling process. It will be the equivalent of a 10-story building, built downwards underground, for the purpose of lifting the tons of combined sewage that will be conveyed in the tunnels after rainstorms up to surface level for treatment.

The contract also includes an enhanced clarification facility to treat up to 225 million gallons per day of excess flow during rainstorm events. The flow then can either be sent to secondary treatment or discharged to the Potomac.

DC Water Board of Directors Chairman Allen Y. Lew commented, “Right now there are several billion dollars in construction projects underway at the Blue Plains Advanced Wastewater Treatment Plant, and the most costly are federally mandated. These costs are borne mostly by our ratepayers; therefore, we continue to seek measures to lessen the rate increases. Supporting creative solutions and negotiating competitive contracts go a long way in achieving that mission.”

“We are pleased to work with PC/CDM Joint Venture on this important component of our wet weather plan,” said DC Water General Manager George S. Hawkins. “And we are proud of the innovative solutions we continue to put in place. The projects that make up the wet weather plan achieve both nitrogen reduction and CSO abatement to improve the health of our waterways. By combining separate goals into related projects, we will save hundreds of millions of dollars.”

"Our joint venture is excited to work with DC Water on this unique project in our nation’s capital," said Kevin McCarthy, president of PC Construction . “We look forward to being part of this massive project to protect the environment.”

For decades, DC Water has been a pacesetter in restoring the Potomac River and Chesapeake Bay by improving performance and treatment capabilities at the Blue Plains Advanced Wastewater Treatment Plant. Blue Plains has successfully achieved nitrogen removal since 1999 and was the first to achieve the Chesapeake Bay Agreement goal of 40 percent nitrogen reduction. The current projects further reduce nitrogen levels to the limits of technology.

For more information on CSO reduction, please view DC Water’s informational cartoon about the Clean Rivers Project, “A Drop’s Life." Additional information is available at http://www.dcwater.com/cleanrivers.