The Agnes Flood of 1972 prompted the US Army Corps of Engineers to initiate a levee-raising project in 1992. As design ensued, the effect of the five-foot raising of the levees on stormwater and sanitary pumping stations along the 17-mile levee system was questioned. Borton-Lawson was retained by the Corps of Engineers to analyze, and if necessary, design structural remediation for overstressed elements in the pumping stations. Analysis by Borton-Lawson indicated every station would need remediation to prevent failure during a maximum flood event. New interior wall systems, complicated steel framing systems, and concrete struts were designed to strengthen the pumping stations. Sophisticated computer modeling was necessary, taking advantage of moment redistribution to minimize the extensive structural modifications in cramped station interiors with a maze of utilities. Special construction techniques and safety precautions were detailed on the plans and in the specifications to address the difficult working conditions, including “confined space” in deep sanitary station sumps. Labeled by the Corps of Engineers as a very complex design and an even more complex construction project, the work was completed under the $2.8 million bid amount. |
