Skunk River Bridge
In April 1876 the Story County Board of Supervisors directed County Clerk S.J. Shearer to advertise for three iron bridges over the South South Skunk River. One would span the river at Soper's Mill north of Ames, the second would be located in Grant Township, and the third would span the Skunk River just east of the small town of Cambridge, in Union Township. By far the longest of the three, this last bridge consisted of an 80-foot wrought iron truss supported by cylinder piers over the river's channel, with a 200-foot timber pile approach. The contract to fabricate and erect the three spans was awarded in June to the King Iron Bridge and Manufacturing Company of Cleveland, Ohio.
King apparently completed the three bridges later that year, but in September 1877 the Cambridge Bridge already required repairs. The truss's deck and stone substructure needed occasional repairs in subsequent years, the most serious of which was a partial reconstruction of the crumbling stone abutments in 1899. By the mid-1910s the Cambridge Bridge was no longer sufficient to carry traffic at this crossing. In 1916 the county hired the Ben Cole & Sons Construction Company of Ames to replace the bridge and to move the old truss to a new crossing of the South Skunk River southeast of Ames. Here it was combined with an ISHC-standard pony truss on a new concrete substructure. Coincidentally, this reconstruction cost of $6,600 - the same amount as the original bridge had cost to build in 1876. The bridge carried extremely light traffic at this remote location until about 1990, when the road was vacated and the bridge abandoned in place.
The South Skunk River Bridge employs a classic Warren truss configuration, with a web that relies on simple triangulation for its rigidity. "The term Warren truss girder was originally applied only to the particular case of the Triangle truss in which the web triangles are all equilateral; but later writers generally use the name for any triangular truss, noted bridge engineer J.A.L. Waddell wrote in his 1916 treatise Bridge Engineering. "As there is no special advantage in making the web triangles equilateral, there does not appear to be any good raison d'etre for the use of the true Warren type." In a state dominated by bowstrings and Pratt trusses in the 1870s and early 1880s, relatively few Warren trusses were built. Only a handful survives to the present, of which the Skunk River Bridge is the oldest. Built during the county's formative years by the nation's most prolific bridge fabricator, it is an important early transportation related resource [adapted from Fraser 1992].
- Warren through truss bridge over Skunk River on (Vacated) 255th Street (Ken Maril Road) in Ames
- Ames, Story County, Iowa
- Built 1876; moved here 1916; rehabilitated 1974; abandoned 1990
- - Ben Cole & Sons Construction Co. of Ames, Iowa (Movers)
- Cambria Steel Co. of Johnstown, Pennsylvania (Iron/Steel Manufacturer)
- Iowa State Highway Commission of Ames, Iowa (Pony Truss Designer)
- King Iron Bridge & Manufacturing Co. of Cleveland, Ohio [also known as King Bridge Co.]
- Pinned Warren through truss
Riveted Warren pony truss
Length of largest span: 80.1 ft.
Total length: 163.1 ft.
Deck width: 15.7 ft.
Vertical clearance above deck: 13.5 ft.
Posted to the National Register of Historic Places on May 15, 1998
- Also called
- 250th Street Bridge
Old Cambridge Bridge
- Approximate latitude, longitude
- +41.98656, -93.58749 (decimal degrees)
41°59'12" N, 93°35'15" W (degrees°minutes'seconds")
- Approximate UTM coordinates
- 15/451335/4648451 (zone/easting/northing)
- Quadrangle map:
- Land survey
- T. 83 N., R. 24 W., Sec. 24
- Average daily traffic (as of 2011)
- Inventory numbers
- IA 314920 (Iowa bridge number)
NRHP 98000484 (National Register of Historic Places reference number)
BH 14441 (Bridgehunter.com ID)
- Inspection report (as of January 2017)
- Overall condition: Poor
Superstructure condition rating: Imminent Failure (1 out of 9)
Substructure condition rating: Imminent Failure (1 out of 9)
Deck condition rating: Imminent Failure (1 out of 9)
Sufficiency rating: 20.6 (out of 100)
View more at BridgeReports.com
- November 2, 2021: New photos from Mitch N.
- June 6, 2019: Updated by Luke: Noted failed relocation in 2001-2
- October 17, 2016: Updated by Dana and Kay Klein: South Skunk
- August 22, 2015: Updated by Luke: Merged photographs posted to the forum by Sam Hamilton.
- February 2, 2015: New photos from Lee Smith
- September 30, 2014: New photos from Kevin Skow
- November 20, 2013: Updated by Luke Harden: Noted that the ISHC designed the pony truss
- November 14, 2012: Photo imported by Luke Harden
- November 10, 2012: Updated by Luke Harden: Added Cambria Steel Co. in builder's section
- March 7, 2012: Photo imported by Luke Harden
- February 28, 2012: Photo imported by Luke Harden
- January 25, 2012: Updated by Luke Harden: Added categories "Relocated", "Pin-connected", "Iowa State Highway Commission", "Wrought iron", "Riveted"
- November 30, 2011: Photo imported by Luke Harden
- August 31, 2011: Updated by Luke Harden: Edited description
- August 31, 2011: New photos from Jason Smith
- June 3, 2011: Updated by Luke Harden: Added photograph and integrated history of the bridge article
- May 27, 2011: Updated by Tony Dillon: This is indeed a pinned Warren truss
- March 27, 2011: Updated by Anthony Dillon: Added truss type
- March 27, 2011: New photos from Bill Eichelberger
- Bill Eichelberger
- Tony Dillon - spansaver [at] hotmail [dot] com
- Jason Smith - flensburg [dot] bridgehunter [dot] av [at] googlemail [dot] com
- Kevin Skow - weatherbum [at] hotmail [dot] com
- Lee Smith - ljsmith_32 [at] hotmail [dot] com
- Dana and Kay Klein