Black Earth Bridge Reconstruction, Dane County, WI
On August 20, 2018 over 13 inches of rain fell over western Dane County, WI. Black Earth Creek hit record high flood stage. Two bridges carrying USH 14 over Black Earth Creek—one on the town’s east side and one on the west side—were significantly damaged in the flood and nearly isolated the tiny community. The western bridge had a washout behind and under the west abutment. The center pier of the eastern bridge dropped into the creek. Spread footings for each bridge were compromised when the flood caused a 15-foot scour in the underlying glacial till type soils.
State government moved quickly to fund two emergency bridge replacement projects. Agreements for both bridges were signed on September 14, 2018 and work began Monday September 17, 2018. The engineers prepared the final structure plans by October 4, with a final plan set completed on October 24. The construction contractor immediately ordered girders and began removing the existing bridges in that first week.
The flooding had damaged underwater sections of the west bridge, and the north bridge pier had collapsed into the water. The contractor successfully minimized impacts to the creek itself during removal of the damaged sections, as Black Earth Creek is a valued resource for trout fishing.
The contractor worked long days, six to seven days a week, on both bridges. A challenge the team encountered almost right away was that gas mains in the water, parallel to each bridge and on both sides of the roadway, had been exposed by scour during the flooding. The contractor took great care to avoid the gas line until the lines could be temporarily taken out of service. Another challenge was an exceptionally cold and wet fall, with decreasing hours of daylight.
OES contacted the Wisconsin Department of Transportation (WisDOT) to offer our expertise and was selected from the WisDOT list of eligible consultants. OES provided project management, construction inspection, and materials certifications. OES completed material testing of ready mix concrete and conducted field density testing of asphaltic pavements using our nuclear density gauge.
In addition to our services during construction, OES used this opportunity to train a newly-hired WisDOT bridge construction inspector.
The town residents and the Wisconsin DOT were very pleased with how quickly the bridges were repaired. Many residents expected a long, drawn-out process that would likely have further negatively affected their community.