By: Metal Culverts Inc
Imagine a time when minimum wage was 30 cents an hour, fuel costs were 12 cents a gallon, and blueprints were actually blue. In 1941, 75 years ago, Union County, Iowa commissioned a dirt road to provide farmers a better route to get their harvest to the grain bins in nearby Creston, Iowa. The three mile grading project included a structural steel plate arch as well as over 1,000 feet of corrugated steel pipe culverts on a farm-to-market road.
The county contracted out the excavation and culvert installation to Roth Construction of Indianola, Iowa.
Roth moved more than 56,000 yards of dirt and installed the culverts for under $7,000, however, the Union County Engineer decided the county would assemble the structural steel plate arch themselves.
This particular structural steel plate arch has a 15 foot span with a 7 foot 8 3/8 inch rise and a length of just over 30 feet.
Assembly of the structure began on October 14, 1941, and installation was completed in just 13 working days. It took 70 hours to assemble and the total labor costs were $66.00, material costs on the project were $566.15 and the equipment costs were just $41.99. The total assembled cost for the structural plate arch was $674.14.
The primary function of the road has remained unchanged over the years, and despite the substantial changes in agricultural equipment and increased loading capacity, the structural plate arch continues to perform well.
Over the past 75 years, the county has added concrete footing and headwalls but little else has been done besides several routine inspections. The latest inspection has the structural plate arch listed in good condition.
There are thousands of structural plate, lock seam, and riveted galvanized corrugated metal pipe in this condition and of this vintage throughout the Midwest.
What is unique to this project is the intact bridge record and blueprints dating back to 1941. This is a prime example of galvanized material performing as expected and living up to its design — making this a hall of fame worthy discovery!
A special thanks to Larry Latham, Assistant to the Engineer, and Union County, Iowa for their assistance in providing detailed cost information and sorting through their archives and to NCSPA member, Metal Culverts Inc., for providing additional information.
Standard structural plates are available in thicknesses ranging from 0.111 inches to 0.380 inches. Plates are furnished curved to various radii and are clearly identified by the fabricator for field assembly.
These plate structures are assembled into various shapes including round, pipe arch, singles-radius arch, horizontal ellipse, low profile arch, high profile arch, pear, underpass and vertical ellipse, with other special shapes also available. Learn more at by clicking here.