Jefferson Barracks Bridge; Movable-Bed Model Study

In July 1977, the Illinois Department of Transportation awarded a contract to construct piers for Interstate Highway 255 Bridge across the Mississippi River at mile 168.7. As of March 1979, the contractor had constructed a work trestle across Jefferson Barracks Slough and a work trestle from the island to a point past pier 10. The contractor also had constructed cofferdams for the construction of piers 5-10, 12, and 13. In the spring of 1979, the discharge in the river increased, and debris accumulated upstream of the work trestle. On 21 March 1979, the portion of the work trestle between cofferdams at piers 9 and 10 failed. It is not known exactly when the cofferdam at pier 10 failed, but it is assumed that it failed about the same time as the trestle between cofferdams at piers 9 and 10 failed. By 19 April 1979, the cofferdam at pier 9 and the portion of the work trestle between cofferdams at piers 8 and 9 had failed. This study was conducted to investigate the relationship of the existence of the work trestle, the cofferdams, and the accumulation of debris that occurred upstream of the work trestle to the riverbed movement that occurred before, during, and after the failure of the work trestle and cofferdams.