The Central Platte NRD asked JEO to analyze and design flood protection for residential, commercial, and agriculture properties in western and northern Grand Island. Flood protection provided through this project will result in the removal of northwestern Grand Island from the FEMA floodplain.
Another important benefit of this project includes reducing flood damages to crops, properties, and other infrastructures. Once completed, this project will eliminate approximately $59 million in damages during a 100-year (1% annual chance) event.
Using updated LiDAR and topographic surveys, complex hydrology and hydraulic models were revised and further developed to ensure that all elements of the project will work in
harmony to provide adequate flood protection.This project contains complex hydrology and hydraulic situations, including timing of hydrographs, analysis of flows crossing drainage basin divides, and examining potential detention effects caused by existing infrastructure in flat terrain. In addition to challenging technical aspects of the project, a variety of non-technical challenges have also been encountered.
The proposed low land detention cells include 3.6 million cubic yards of earth excavated to date, with 2 million cubic yards remaining in future phases. Two dry dams are nearing completion of construction, both of which included about 50,000 cubic yards of excavation/embankment. The remaining two dry dams, both estimated to include over 200,000 cubic yards of excavation/embankment, are in the final design stages. Construction is planned for the spring and summer of 2014. Construction of the levee is anticipated to commence following completion of the dry dams and construction of the remaining detention cells should follow completion of the levee.
With an estimated $30 million total project cost, this large project contains several moving components and elements, requiring extensive coordination between JEO, co-sponsors (Central Platte Natural Resources District, Nebraska Department of Natural Resources, Natural Resources Development Fund, City of Grand Island, Hall County, and Merrick County), and various permitting and regulatory agencies. JEO’s work on the project began in 2005 and is expected to continue through at least 2016.