MD: A Preview Inside What Will be the Purple Line’s Tunnel

Sept. 6, 2018
While excavation only began in June, a machine has already dug about 350 feet — one-third of the way into the Purple Line tunnel. Read more about progress on the project in Silver Spring.

While excavation only began in June, a machine has already dug about 350 feet, one-third of the way into the tunnel — from Arliss Street under Flower Avenue, to Wayne Avenue in Silver Spring. The machine has what looks almost like a double drill bit that spins its teeth on the front of what otherwise looks like a yellow backhoe. 

The machine works 4 feet at a time on each eight-hour shift, with workers putting up rebar and spraying special concrete behind it to hold the tunnel in place. That makes for progress of 12 feet each day.

An engineer was keeping a close eye on the work Wednesday as she surveyed the direction of the tunnel, the amount of concrete being used and the form of the materials framing the tunnel wall.

Read the complete article at https://wtop.com/dc-transit/2018/09/get-a-preview-inside-what-will-be-the-purple-lines-tunnel/slide/1/