Jim Dougherty—conservation chairman for the D.C. Chapter of the Sierra Club, which was involved in litigation that led to the 2005 consent decree—says that, during negotiations, the chapter strongly advocated for low-impact development to be incorporated into the plans. "We are just kind of confused by this," Dougherty says. "Why [have they] waited until now to call for a radical change?"
Meanwhile, work on the other tunnels for the CSO program is well under way. In late July, a 26-ft-dia tunnel-boring machine more than a football field in length began digging its way through the first portion of the Blue Plains tunnel, a four-mile section of the 13-mile Anacostia River tunnel.
Additional Projects
While the DC Water continues to make progress with its plan to reduce CSO pollution, two other projects at Blue Plains continue to move forward.
According to Chris Peot, biosolids manager for DC Water, and Walt Bailey, DC Water's assistant general manager for wastewater treatment, work on a nitrogen reduction project is about 65% complete, and a project to enable the wastewater treatment facility to produce a better class of biosolids is about 55% complete. Much of the structural and exterior work on both projects is finished, "but there is a lot of mechanical and electrical work that needs to be done," Peot says.
Class-A Pressure Cooker
The $209-million biosolids project will use a combination of a new Cambi thermal hydrolysis train with anaerobic digestion to create Class-A biosolids. The highly efficient Cambi system will "cook" the biomass under pressure at high temperatures to break down the sludge, making it easier to digest and be converted into biogas.
The design-build project includes four anaerobic digesters, each with a 3.8-million-gallon capacity; four Cambi treatment trains and a pre-dewatering centrifuge building.
CDM Smith, Cambridge, Mass., is the design engineer on the project. A joint venture of CDM Constructors, a unit of CDM Smith, and PC Construction Co. is building the main process train and its supporting infrastructure.
DC Water says this thermal hydrolysis system is the first to be installed in the U.S., and, when it is operational, it will be the largest in the world. The system, if successful, could serve as a model that other municipalities can learn from and replicate, Peot says.
