Preserving A Historic Bridge In Kalona

What’s so special about the Bunker Mill Bridge in Kalona, Iowa?

First and foremost, the Bunker Mill bridge is a historic bridge on Nutmeg Avenue south of Kalona. The Pratt through truss bridge was built in 1887 by the King Bridge Company and modified in 1909 by the Iowa Bridge company. This type of bridge – a truss-style bridge is one of the declining number of bridges across the country which represents a bygone construction method and design. What is remaining of this type of bridge is increasing in importance as picturesque landmarks and must-see travel destinations.

Rapid Rivet - Blind Rivet Nuts - Dec 2013 Bunker-Mill-Bridge-2-1024x768The Historic Bunker Mill Bridge

The historic Bunker Mill bridge has been closed to traffic since 2004 as a result of the Washington County’s bridge inspection which labeled the bridge unsafe for traffic. The bridge was recommended for demolition and replacement. However, the high cost it would take to remove and replace the bridge, which at that time was estimated at $2 million caused any plans to replace the bridge to be shelved and canceled.

Converting The Bridge Into A Trail Bridge

The citizens of the Kalona and Richmond communities proposed that the structure be preserved for its cultural, practical, aesthetic and most importantly, for its historic value to the local communities. The Washington County Board delayed the bridge demolition in order to allow for a full engineering study of the bridge into other solutions. And in 2007, a grant was awarded to the Washington County Trails Committee to develop a trails master plan for Washington County to convert the bridge into a trail bridge.

Preserving Bridge Construction Methods

As part of the preservation effort, restoration work of the bridge included hot riveting. The owner of Bach Steel, Nels Raynor was given the task of fabricating replacement parts for the bridge. He led a demonstration of hot riveting – a lost art which Raynor is trying to preserve along with the Bunker Mill bridge.

Rapid Rivet - Blind Rivet Nuts - Dec 2013 bildeHot Riveting

Hot riveting is not a difficult process but it’s labor-intensive. This is why this fastening procedure is no longer a method preferred by many for fastening steel beams together. The old-fashioned appeal of hot riveting is unique and looks nice. Once driven, the blind rivet nuts expand in the hole and fill the void. They attach to the material, making them stronger than ever.

Collaborative Efforts

The Bunker Mill Bridge restoration is dependent on grants and donations for funding. The Friends of the Bunker Mill Bridge, Workin Bridges Company and Bach Steel have been raising funds for Phase I of the project. Phase I work is expected to be completed in the spring with the addition of new planking. The project’s Phase II will feature the replacement of the sloping northern approach span and the bridge railings resembling ornamental features common to truss bridges in the 1880s and 1890s.

Rapid Rivet - Blind Rivet Nuts - Dec 2013 doc529f3a44b9e2a314176526


Wouldn’t it be exciting to see the old Bunker Mill Bridge again?