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Major shafts are constructed along the alignment. |
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PB specified special construction techniques for the shafts. |
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The Swan Island CSO Pump Station's wet well and pump inlets. |
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A Vast Underground Network
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Major shafts are constructed along the alignment, including the Swan Island CSO Pump Station, a 220-million-gallon-per-day combined sewage pump facility. PB specified special construction techniques for the shafts—including diaphragm wall or ground freezing applications—and made provisions to address shaft stability throughout the process. Connecting the city's existing sewer system to the new tunnel, the five shafts will serve a variety of functions:
Collect flows from existing sewer lines and outfalls with combined stormwater and sewage;
Provide surge storage capacity;
Provide for venting of air from the tunnel; and
Provide equipment and personnel access.
All shafts combine functions and requirements, serving as the final shafts while being used temporarily during construction for machine maintenance and retrieval of the TBMs.
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