The City of Decorah was approached by a local stone Mason, Ted Wilson, with the idea of constructing a dry laid stone arch bridge in Dunnings Spring Park. The park had once had a similar structure over a 140 years ago when it was the site of a grist mill and seemed like a natural fit for the bridge.
Ted and the City had selected a site on the spring fed stream near an ageing wooden foot bridge where the stone bridge would fit well in the park. Ted had spent considerable time studying the geometry and construction of similar type bridges and developed sketches of his proposed bridge. The City donated most of the stone used in the project, which was reclaimed from a school that had been demolished.
WHKS worked with Ted and the City to develop final trail grades, geometry, dimensions, and plans for the structure that fit the proposed location. WHKS performed an arch analysis of the design to ensure that it would safely support modern pedestrian bridge loads from the AASHTO LRFD Guide Specifications for Pedestrian Bridges. Abutments were designed using a reinforced concrete spread footing system keyed into bedrock. The final bridge layout was a 7’x36’ structure with a 16’ span over the stream.
WHKS also provided bid and letting phase services to the City.