Lady Bird was christened with DC tap water ready for her mission to tunnel more than 6.4km along the Potomac at a depth of approximately 30m. The machine is more than 120m long and weighs more than 1300t.
It will dig the Blue Plains Tunnel, which is a portion of DC Water’s clean river project to significantly reduce combined sewer overflows (CSOs) and improve water quality in the District of Columbia.
As in many older cities, about one-third of the District has a combined sewer system. CSOs occur during heavy rain when the mixture of sewage and stormwater cannot be contained in the sewer pipes and overflows to the nearest water body.
DC Water’s plan to significantly reduce CSOs to the Anacostia River is to build massive underground tunnels that will store the combined sewage and runoff during intense rainstorms and then slowly release it when the system has the capacity to treat it.
DC Water’s TBM was named after Claudia Alta ‘Lady Bird’ Johnson, wife of Lyndon B Johnson. When her husband became president in 1964 she made it her mission to preserve and protect the environment.
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