The District of Columbia Water and Sewer Authority (DC Water) is implementing its Long Term Control Plan (LTCP) for the District's combined sewer system, entitled the DC Clean Rivers Project (DCCRP). The DCCRP consists of a system of tunnels and diversion sewers for the Anacostia River, Rock Creek, and the Potomac River, the purpose of which is to capture combined sewer flow for treatment in DC Water's Blue Plains Advanced Wastewater Treatment Plant. The projects are projected to provide a reduction in combined sewer overflow (CSO) volume of 96% on a system-wide basis and 98% for the Anacostia River. As such, the projects are greatly beneficial both for the environment and District residents. While the major component of the DCCRP includes deep storage tunnels, there will also be thousands of linear feet of new diversion sewers needed to convey flows to the deep tunnels. These diversion sewers will range from 48 to 108 inches in diameter (1.2 to 2.7 m) and will be constructed in mainly urban areas in no less than four separate construction contracts. Trenchless technology of one form or another will be required in each of these contracts. This paper will present a summary of the trenchless components of the planned diversion sewers. Ground conditions along the trenchless alignments will range from soft organic soils to stiff clay and, as is typical of most all urban environments, there are significant risks for both man-made and natural obstructions. Expected trenchless methods include conventional pipe jacking, microtunneling, and small-diameter soft ground tunneling. Items to be discussed in the paper include criteria used to determine limits of trenchless construction as well the evaluation processes that were employed to determine appropriate trenchless methods and the status of the work.
展开▼
