Metropolitan Water Reclamation District said other cities are emulating their
Deep Tunnel solution to keep sewage out of the local waterways. Here is one of them.
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asce
Washington DC is spending $3b to handle their combined sewer overflows by Mar 23, 2030.
As of Nov 2023, the 23' (7m) purple tunnel is built, and $819m has been awarded to build the 18' (5.5m) yellow tunnel.
The tunnels are just 80' (24m) to 100' (30m) deep so they encounter a variety of geographic conditions. [Chicago dug their tunnels 300' (91m) deep so that all of their tunnels are through solid rock.] The northern part of the tunnel is mostly in hard rock, and the southern part is in soft ground conditions. Consequently, they are using two different Tunnel Boring Machines (TBMs). The rock TBM is a hybrid that can operate in open and slurry modes. The southern one is "a hybrid version of an earth pressure balance and slurry mode TBM known as a variable density TBM." It "will be used to tunnel initially through rock and then soft ground." |
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cbnahalmarcleanrivers
Another challenge for the Potomac River Tunnel is that the big drop shafts to support the TBMs are in urban areas with "sensitive" buildings nearby. [I think sensitive means old historic buildings.] |
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dcwater
Blasting began in May 2025 to build the West Potomac Park Shaft that will be used to launch the TBMs. The northern one is named Mary and will be constructed in the fall of 2025, and the southern one is named Emily and will be constructed in 2026. |
Deane Lindley
posted eight photos with the comment: "Local 77 members working with CBNA-Halmar at the Potomac River Tunnel."
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[I think the green thing on the top of the piling is a vibrator that is used to drive the pile into the ground.] |
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