CS39C - Concurrent Session 39C: Risk Informed Assessment to Support a Section 408 Authorization

The Louisville Metro Levee System reduces flood risk to the City of Louisville Kentucky. The levee system was constructed by the U.S. Army Corps of Engineers and is now operated and maintained by the local sponsor, the Louisville and Jefferson County Metropolitan Sewer District (MSD). The levee system has a total length of 25.9 miles consisting of concrete floodwalls and earthen levee with sixteen flood pump stations for flood protection.

MSD determined the need to upgrade the existing Paddy’s Run Flood Pump Station capacity to reduce the risk of interior flooding. Due to the age and complications associated with upgrading the existing pump station, a new flood pump station will be constructed within the existing levee prism and portions of the existing station will be selectively demolished. MSD initiated a Progressive Design-Build project for a new Paddy’s Run Flood Pump Station. This project will require a Section 408 authorization from USACE prior to construction.

To support the Section 408 permit application, the project team conducted a potential failure mode analysis (PFMA) on a proposed levee modification and pump station design. The goal was to evaluate levee risks with the new pump station in place as well as potential risks during construction and verify that that the proposed project “will not be injurious to the public interest and will not impair the usefulness or purpose of the Civil Works” (33 U.S.C. 408). The results were also used to inform designs in accordance with the USACE ECB 2022-7 “Interim Approach for Risk-Informed Designs for Dam and Levee Projects”. USACE has completed baseline risk assessments for most levees within USACE portfolio, including a higher level semi-quantitative risk analysis (SQRA) for the Louisville Metro Levee System. The project team was able to leverage the USACE baseline risk assessment of the existing levee; this was greatly beneficial and streamlined the process. The PFMA was completed on 30% designs and involved the design team, the construction team, the local sponsor and the USACE staff. This paper will summarize the process followed by the team, present findings and identified design refinements, discuss challenges and opportunities associated with using existing risk assessment results, and share lessons learned from incorporating risk-informed processes into levee design and Section 408 Permit application.