1 vote

Sunol Aqueduct (Flume Bridge)


Partial Elevation

Elevation of the north side of the stucture.

Photo courtesy of TY Lin International


BH Photo #165951


Designed as part of the water system to provide water to the San Francisco peninsula in the early 1900's. The system was owned by the Spring Valley Water Company until control was purchased by the San Francisco Water Department. Construction of the Hetch Hetchy Aqueduct made this system obsolete and led to its eventual abandonment. The site is currently closed to the public.


Abandoned open-spandrel arch bridge
Alameda County, California
Future prospects
Possible restoration of the structure and inclusion into the East Bay Parks district trail system.
Built between 1920-1925 by the Spring Valley Water Company
Open spandrel reinforced concrete arch carrying an 8' x 6' water channel.
Total length: 118.0 ft.
Deck width: 8.0 ft.
Also called
Niles Canyon Aqueduct
Secret Sidewalk
Approximate latitude, longitude
+37.58694, -121.95883   (decimal degrees)
37°35'13" N, 121°57'32" W   (degrees°minutes'seconds")
Approximate UTM coordinates
10/591923/4160496 (zone/easting/northing)
Quadrangle map:
Inventory number
BH 45324 (Bridgehunter.com ID)

Update Log 

  • October 21, 2010: Updated by Eric Root: added to Aqueduct category
  • May 20, 2010: Added by Kevin Pope



Sunol Aqueduct (Flume Bridge)
Posted September 2, 2018, by Don Morrison

The old aquaduct AKA "the secret sidewalk" is being demolished. No word on the bridge's fate, but it will likely be demolished with the aquaduct.


Sunol Aqueduct (Flume Bridge)
Posted May 20, 2010, by Todd D. Walker (mrwalk08 [at] aol [dot] com)

Good idea there. Many historic bridges are badly in need of paintjobs. Why don't we have convicts in the system, which may include the lunatic vandals, be put into bridge repainting crews to save bridges and possibly taxpayer dollars to replace bridges, if feasable. Nathan, you got me going...

Sunol Aqueduct (Flume Bridge)
Posted May 20, 2010, by Nathan Holth (form3 [at] historicbridges [dot] org)

If they like painting things so much, why don't we make these people do a proper painting of those many historic bridges in the country that need it?

Sunol Aqueduct (Flume Bridge)
Posted May 20, 2010, by Todd D. Walker (mrwalk08 [at] aol [dot] com)

Look what we have here. Another example of stupidity.

Idiots with their spraycans passing as artists. I wonder how much fun those fools will have "cleaning" the stuff they deface as punishment. Again, punks with spraypaint and historic bridges DON'T mix!