Crews get a reprieve from the scorching sun as they work underground at the foot of the tunnel in North Beach.
Not labeled for reuse. All rights reserved.
Crews get a reprieve from the scorching sun as they work underground at the foot of the tunnel in North Beach.
Not labeled for reuse. All rights reserved.
The soon-to-be Central Subway tunnel is now a 1.5-mile trackless tube of wires and lighting.
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Matthew Fowler, project manager for design
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Tunnel boring machine "Mom Chung" sits patiently at the northern mouth of the tunnel she created, waiting to be dismantled.
Not labeled for reuse. All rights reserved.
Tunnel boring machine "Mom Chung" sits patiently at the northern mouth of the tunnel she created, waiting to be dismantled.
Not labeled for reuse. All rights reserved.
Tunnel boring machine "Mom Chung" sits patiently at the northern mouth of the tunnel she created, waiting to be dismantled.
Not labeled for reuse. All rights reserved.
Crews get a reprieve from the scorching sun as they work underground at the foot of the tunnel in North Beach.
Not labeled for reuse. All rights reserved.
Mom Chung, pictured here, is identical to partner boring machine Big Alma.
Not labeled for reuse. All rights reserved.
Photographer Karl Nielsen went underground for a final peek at Big Alma and Mom Chung, the tunnel boring machines named in honor of iconic figures from San Francisco. The massive machines have completed their nearly year-long journeys carving out tunnels underneath a notoriously congested corridor in the city. The tunnels will carry the extension of the Muni Metro T Third Line from SOMA to Union Square and Chinatown when the Central Subway goes live in 2019, making travel much smoother and swifter between some of the city's most vibrant neighborhoods.