3 votes

Geysers Road Bridge


Geysers Rd

Looking SE

Photo taken by Craig Philpott in September 2009


BH Photo #145900

Street Views 


Highway sign says, "Built 1909, relocated 1937"

A Group History 

Written by John C Stutz

This span is a ~130’ through Pratt mainline railroad bridge of circa 1880, one of at least six that were recycled to minor rail lines in Sonoma and Marin Counties circa 1905-10. A CalTrans bridge report for one of these mentions drawings with the initials “G, H & S A”, suggesting the Galveston, Harrisburg & San Antonio railroad, the Southern Pacific’s subsidiary in Texas. I believe these bridges represent original spans from the SP’s Sunset Route, dating from 1877-83. Similar spans were cascaded down to many of the SP’s branch lines on the West Coast, and to associated private lines like the Diamond & Caldor, in the same time frame, all part of SP’s Harriman era upgrading.

Of these six, one was sold to the Gualala lumber mill and erected on steel cylinder piers at their logging railroad’s crossing of the North fork of the Gualala river. As of 2018 it still stands on those piers, albeit raised about 6’ to clear floods, on the Gualala 501 Rd. On the Northwestern Pacific’s narrow gauge line along Tomales Bay to Duncan Mills and Cazadero, two spans replaced the Howe Trusses at the mouth of Keys Creek in 1906. The steel cylinder piers remain, adjacent to highway 1, two miles south of Tomales. In 1930, as the narrow gauge was lifted, one was re-erectd over Lagunitas Creek and Sir Francis Drake Blvd., in what is now Samuel P. Taylor State Park. That one was long since replaced by a modern bridge for the Cross Marin trail. The remaining three were used on the NWP’s standard gauge Russian River branch, replacing the washed out second crossing of the Russian River near Northwood, above Monte Rio, in 1909. That branch was abandoned in 1935. Several of its bridges were recycled for highway use, the Northwood spans among them. Two were erected on the Stewart Point – Skaggs Spring Road, at the Gualala River and Haupt Creek crossings, and one on the Cloverdale – Geysers Road over Big Sulphur Creek. The Gualala R. span was replaced circa 1995, while the remaining pair are still visible in Google Satellite View as of 2018/03.

These are typical examples of Phoenix patent bridges built by Clark, Reeves & Co. of the Phoenix Bridge Works. The patented feature involves the columns (posts or compression members), wrought iron tubes assembled from segments riveted together along radial flanges. This makes an extremely efficient post, in terms of strength to weight ratio, but one lacking in facility for lateral connections to bracing elements. The Phoenix column was widely used in the 1870’s and 80’s, in both bridges and buildings, but had been superseded by 1900. For further information, see Thomas R. Winpenny’s history of the Phoenix Bridge Co., “Without Fitting, Filing, or Chipping”.


Pratt Through truss bridge over Big Sulphur Creek on Geysers Road
Sonoma County, California
Open to traffic
Future prospects
Slated for "seismic replacement" upon funds becoming available. Bridge will be bypassed and abandoned.
Built 1909; rehabilitated 1970
- Phoenix Iron Works of Phoenixville, Pennsylvania
Pin Connected Pratt Through truss with Phoenix columns
Length of largest span: 129.9 ft.
Total length: 149.0 ft.
Deck width: 13.1 ft.
Vertical clearance above deck: 21.3 ft.
Eligible for the National Register of Historic Places
Approximate latitude, longitude
+38.82355, -122.88342   (decimal degrees)
38°49'25" N, 122°53'00" W   (degrees°minutes'seconds")
Approximate UTM coordinates
10/510119/4297203 (zone/easting/northing)
Quadrangle map:
Average daily traffic (as of 2008)
Inventory numbers
CA 20C-5 (California bridge number)
BH 11612 (Bridgehunter.com ID)
Inspection report (as of July 2017)
Overall condition: Fair
Superstructure condition rating: Fair (5 out of 9)
Substructure condition rating: Fair (5 out of 9)
Deck condition rating: Good (7 out of 9)
Sufficiency rating: 50.3 (out of 100)
View more at BridgeReports.com

Update Log 

  • March 6, 2018: Essay added by John C Stutz
  • July 21, 2017: New Street View added by Clark Vance
  • July 20, 2017: New video from Craig Philpott
  • September 22, 2015: Updated by Luke: Added categories "Relocated", "Pin-connected", "Phoenix columns", "Phoenix Iron Works", "Rail-to-road"
  • July 2, 2013: Updated by Nathan Holth: New information from county: Bridge to be bypassed and abandoned.
  • June 13, 2013: Updated by Nathan Holth: This bridge is now doomed.
  • March 6, 2012: New photos from Craig Philpott
  • May 15, 2010: New Street View added by Craig Philpott
  • March 22, 2010: Updated by Craig Philpott: refined design description
  • March 1, 2010: Updated by Craig Philpott: Amended design
  • February 19, 2010: Updated by Craig Philpott: Corrected design
  • September 7, 2009: New photos from Craig Philpott

Related Bridges 



Geysers Road Bridge
Posted January 21, 2019, by Daniel

https://find.sonomalibrary.org/client/en_US/default/search/d... that has a 1966 photo where the bridge looks lower than it is now. Given that there some realignment on that road in the late 60s (there are multiple sites along it with bridge abutments and piers, with the road now downslope from them, topos seem to change in the late 60s), I wonder if they raised it somewhat at the same time.

Geysers Road Bridge
Posted January 13, 2019, by Daniel

These were present on some but not all of the round tension members (the bridge has some round and some rectangular tension members). While some were at midpoints, one weren't (the one I took a picture of). Then again, on one of them one side of the brace was no longer attached, so it's possible that they were all originally ad midpoints.

I didn't think to look at whether Haupt Creek or Gualala have any round tension members. I have a picture of the repair on Haupt Creek and it's rectangular. The other photos I took aren't good enough for me to determine if any of the tension members are round.

I also noticed 2 locations on this road where there used to be bridges parallel to the road, with foundations still present and the road now downhill of the foundations. I'm curious as to what went on there. The region sees a lot of ground motion, to the point that there were I think 8 sections that are now gravel (some of which are paved, with a centerline, on both sides of the gravel), I wonder if they decided it was cheaper to move it rather than maintain the old bridges.

I'm also a little surprised that none of the 3 have any posted weight limits. I'm not sure if you could get a typical semi to this one, as there are some very significant angle breaks on the road and I'd be afraid of high centering, but Skaggs Springs you absolutely could.

Geysers Road Bridge
Posted January 13, 2019, by Art S. (asuckewer [at] knite [dot] com)

My guess (based on engineering logic but not experience) is that its some sort of rig to tune the bridge or a way to reduce the resonance for seismic activity protection.

The bridge seems to have lost much of its original detail so some of the original mechanisms to adjust the tuning/loading of the tension members may not function and this could be a patch. If the tension members are pushed apart, it may help in keeping the tension evenly distributed between the two members (the looser rod will bow out more than the tight one) if the adjustment devices no longer work.

Also, by connecting the tension members at their midpoint, the resonance frequency is increased and the amplitude is reduced (the seismic reason).


Art S.

Geysers Road Bridge
Posted January 13, 2019, by Daniel

Any guesses as to what these are for? They were on a few braces, in different locations.

Geysers Road Bridge
Posted September 22, 2015, by Daniel (danielaketchum [at] gmail [dot] com)

This article states that Hauser Bridge is from the same original location. This seems unlikely, as Hauser is a Bailey Bridge built in the late 40s and this was probably 1870s or 1880s. John Charles Stutz says that Geysers Road Bridge is from the same project, and that makes sense. I don't know where the pre-1984 South Fork Gualala River Bridge was - is this around 3.4mi by road West, also on Stewarts Point Skaggs Springs Road?

Geysers, Haupt Creek & North Fk Guauala Road Bridges
Posted February 11, 2014, by John Charles Stutz (john [dot] c [dot] stutz [at] nasa [dot] gov)

The Geysers Road, the Haupt Creek bridge, and the pre-1984 South Fork Guauala River bridge, are all typical 1870's era railroad bridges. Cal Trans documents mention drawings initialled GH&SA RR, suggesting the Southern Pacific's Texas subsidiary, and these spans are typical of those installed by the SP during initial construction of the Sunset and Oregon routes.

The 1909 build date quoted for the Geysers span, is actually when these spans were recycled to the NWP RR's Russian River branch, and installed above Monte Rio as a 3-span crossing. In the same time frame, similar spans were re-erected on the former NPCRR at Tomalas Estuary and Papermill Creek, and the Guauala RR's crossing of the North Fork. The later span still stands on the circa 1910 steel cylindrical piers, but was raised clear of the flood plain circa 1940.

Geysers Road Bridge
Posted June 27, 2012, by Gail Johnson (gailjohnson [at] vom [dot] com)

I am wondering if you are aware that the Sonoma County Dept of Transportation has this bridge slated for seismic replacement along with Lambert Road Bridge, Watmaugh Road Bridge,and Chalk Hill Road Bridge. Any information you can supply as an argument against this would be helpful.

Geysers Road Bridge
Posted September 7, 2009, by Anthony Dillon (spansaver [at] hotmail [dot] com)

I agree Robert....those do look like Phoenix Columns. Perhaps the bridge was relocated twice!

Geysers Road Bridge
Posted September 7, 2009, by Robert Elder (robertelder1 [at] gmail [dot] com)

It appears that this bridge is constructed from columns, making it look much older then 1909.