DC Water presented a giant tunnel-boring machine that will help the authority to minimize the amount of raw sewage spilling into rivers and basements during overflows. Photo courtesy DC Water.
The District of Columbia Water and Sewer Authority (DC Water) presented a giant tunnel-boring machine (TBM) that will help the authority to minimize the amount of raw sewage spilling into rivers and basements during overflows caused by rainstorms, with the aim of improving the water quality of the area.
The machine, called Lady Bird, was shown for the first time at the Blue Plains Advanced Wastewater Treatment Plant. The enormous piece of machinery is longer than a football field and weighs more than 1300 tons. Its cutter head, which will be performing the most important task of digging through the clay, spans 26 feet in diameter. Its purpose is to make a four-mile tunnel which starts from two deep shafts at Blue Plains, tunneling 24,200 linear feet up the Potomac River and to the Anacostia River, creating a metro-sized tunnel, which will be in operation by 2018.
However, this is not all. This tunnel will be a part of a much bigger, 12.8-mile tunnel that will serve as a huge holding tank where rainstorm water will be stored. The entire Clean Rivers Project is expected to cost about $2.6 billion and is set to be completed by 2022. DC Water has set a target to reduce sewer overflows by 96 percent by 2025, as part of a 2005 consent decree related to a federal environmental lawsuit, the authority explained in a press release. Although the cost of the project seems huge, the technology is actually $600 million cheaper than any of the alternatives.
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Sewage spills and rainstorm overflows are not uncommon in the District of Columbia, mostly because of the old and overused pipes that can hardly cope with the amount of water. The problem comes from the fact that, similar to many other older cities, about one-third of the District's sewer pipes also carry rainwater runoff. Once the large tunnel has been finished, the mix of rainwater and sewage will be held there and will later be released to flow downhill to the treatment facility after the storm has passed. According to George S Hawkins, DC Water's general manager, the tunnel will be able to capture and store the entire amount of water. The project is the biggest improvement in water quality in the Anacostia, Potomac and Rock Creek area in decades, he added.
The District of Columbia Mayor Vincent C Gray commented that the Sustainable DC Plan revealed earlier this year is going to make the District 'the healthiest, greenest, most livable city in the nation'. The Clean Rivers Project will be at the heart of long-term sustainability for the region and will make the local waterways healthier and cleaner, while also addressing sewer issues stemming from a century of development, he added.
DC Water claimed that the Clean Rivers Project will benefit from the 12.8-mile tunnel, which will provide higher quality water to neighborhoods such as Bloomingdale and LeDroit Park, which have suffered from sewage overflows into basements for many years.