According to TBM: Tunnel Business Magazine, the tunnel system will be broken into 4 projects consisting of tunnels from 15 to 23-ft diameter tunnels and will include approximately 17 vertical shafts and various diversion structures. The tunnels will be approximately 100-ft deep, primarily constructed in soft ground. They will most likely be constructed by earth-pressure balance TBM’s.
The map below shows the alignment of the tunnels and the separation of the four projects based on a figure in TBM. The green lines are the NE Boundary Branch Tunnels, the purple line is the NE Boundary Tunnel, the red line is the Anacostia River Tunnel and the yellow line is the Blue Plains Tunnel. The circular dots are the vertical drop shafts.
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Download the DCWASA Tunnel Projects KML file for viewing in Google Earth. After a figure in TBM: Tunnel Business Magazine.