Project Summary

The Ottawa Township High School is afforded protection from Illinois and Fox River flooding by levees surrounding the high school campus on three sides. The levee system was designed to provide the 100-year level of protection; however, after updated flow frequency profiles were released, the system no longer provided an adequate level of protection and could not be accredited by FEMA. Klingner provided 408 permitting service and worked with USACE through all of the design project phases.

Klingner initially performed a hydraulic risk and uncertainty analysis to determine the necessary levee height increase to obtain full FEMA accreditation under 44 CFR 65.10 requirements. Ultimately, the analysis was reviewed and approved by USACE Rock Island District.

After approval of the risk and uncertainty analysis, Klingner completed a hydraulic impacts analysis to determine the potential impacts of a levee raise and the addition of a levee / floodwall in previously unprotected areas. This component of the project was critical, as the Ottawa Township High School is located in an urban area and any hydraulic impacts could potentially have adverse effects on neighboring properties. A HEC-GeoRAS unsteady flow analysis was performed by Klingner that incorporated both the Fox and Illinois Rivers and analyzed a full range of loading conditions. The HEC-RAS model and impacts analysis was fully reviewed and approved by USACE Rock Island District, which allowed for the project to proceed into the design phases.

Klingner subsequently designed a vertical extension of the existing floodwall, as well as a new floodwall lining the earthen embankment north of the school. The new floodwall utilizes concrete and sheet pile clad in concrete to blend into the nearby residential historic district. Work included the design of earthen embankment improvements along the Illinois River, a storm drainage capture system, and removable gates to maintain land and water access. Klingner developed a Safety Assurance Review Plan that was approved by USACE and outlined the external peer review process for the project’s design components.

Further assistance with the FEMA accreditation submittal package was provided as well.