Design and Permitting of Federal Levees R-613 and R-616-613

Background

Federal Levee Systems R-613 and R-616-613 are in Sarpy County, Nebraska, near the confluence of the Platte and Missouri rivers. The 18.2 miles of earthen levee systems protect billions in local infrastructure and commerce, including major transportation corridors, areas of Offutt Air Force Base, and Omaha’s Papillion Creek Water Pollution Control Plant.

Project

FYRA Engineering, now a part of Houston Engineering, Inc. (HEI), completed the final design, permitting, and construction observation services of levee improvements. This project is currently being reviewed by the Federal Emergency Management Administration (FEMA) for system accreditation.

The designed levee modifications included floodwall construction, closure section modifications, levee height increases, concrete pedestrian trail design, culvert/penetration rehabilitation and replacement, and significant under-seepage mitigation in the form of seepage berms, toe drains, and relief wells. Environmental permitting included aquatic resource delineations, preparation of a biological assessment, a full environmental assessment (EA) to meet NEPA requirements, and 404 permitting.

The amount of wetland impacts required an individual 404 permit, so a 404(b)1 alternatives analysis was completed and a 12-step mitigation plan was developed as well. An off-site wetland mitigation area was also designed for this project. All work was conducted in accordance with 44 CFR 65.10 and was reviewed in parallel by the US Army Corps of Engineers (USACE) Omaha District for 408 permission and 404 approvals.

The proximity of three different riverine systems provided a unique challenge to the levee system analysis and design phase. Hydrologic and hydraulic modeling for the interior drainage analysis was used to determine flood impacts on the landside of the levees system at each drainage penetration. HEC-HMS and HEC-RAS models of the Missouri and Platte rivers and Papillion Creek were used to finalize the study.