Upper Antelope Creek Flood Reduction #135
City of Lincoln and the Lower Platte South Natural Resources District (NRD)
Design / Specifying Engineer
Don Day of Olsson Associates
M.E. Collins (General Contractor); Leick Landscaping (Installer)
THE CHALLENGE: Protecting Homes and Businesses From Flooding.
When the Lower Platte Natural Resources District (NRD) and the City of Lincoln, NE set out to control flooding along the Antelope Creek, they had several objectives in mind. Taking homes and businesses out of the flood plain was a major goal, but preserving and improving a nearby bike path was also a priority.
The Lower Platte South Natural Resources District (NRD) and the City of Lincoln partnered on the $2.5 million project,which included new retaining walls along Antelope Creeks west bank, among other improvements including additional box culverts under a bridge, a “detention cell” to hold water temporarily in a park, two flood-control berms,and a wider recreational trail.
THE SOLUTION: Channelization with Redi-Rock Ledgestone Walls
Finding the right solution for lining the creek channel was a challenge for project designers. Since there was no room to excavate for geogrid, the NRD and City initially considered using a poured-in-place wall and sheet piles.
However, a meeting with local Redi-Rock manufacturer and retailer Workman Precast led the NRD and City to an even better solution. By using massive, one-ton Redi-Rock blocks, engineers were able to design gravity retaining walls up to 16.5 ft. tall to create a channel for the Antelope Creek. Once the owner saw Redi-Rock and the price, the decision was made to specify Redi-Rock with the Ledgestone face (no other options or equivalents allowed).
Several major benefits of the Redi-Rock system in storm channel applications include:
Minimized excavation: The massive size of each Redi-Rock block allows tall walls to be built with minimal excavation. This allows walls to be built closer to property lines—or in the case of this project, the gravity solution preserved space that could be used for widening the bike/pedestrian path.
Fast Installation: Redi-Rock blocks stack like giant Legos, making them quick and easy to install using an excavator and a small crew. Redi-Rock is a product for strong minds and weak backs.
Durable Components: Each block is made of wet cast, 4,000 PSI air-entrained concrete—ensuring that it will stand the test of time.
Superior Aesthetics: Redi-Rocks Ledgestone texture creates walls that look like natural, random stone walls. Ledgestone blocks have the same dimensions and engineered capabilities as other Redi-Rock blocks, but with the look of natural, stacked ledgestone.
THE OUTCOME: 100 Buildings No Longer Threatened By Floods
In total, the project utilized 14,000 sq. ft. of Redi-Rock retaining walls along 2,000 lineal ft. of Antelope Creek. The NRD estimates that when all phases of the project are complete, the flood control measures will take about 100 homes and businesses out of the 100-year flood plain.
The final phase of the project is scheduled for completion in 2012 and includes replacing the South Street Bridge, additional channel stabilization, water main relocation and sanitary sewer construction.
THE REST OF THE STORY:
Even though this was primarily a flood control project, it seems that local bikers and pedestrians are appreciative of the projects other benefit—the improved bike path.
“It’s almost impossible to stop people from using it,” Ed Ubben, project coordinator for the Lower Platte South NRD explained. “We’re almost done. We haven’t had our final walkthrough,” he told the Lincoln Journal Star newspaper in November 2011.
Trail users won’t be the only ones benefiting from the new and improved trail segment. The zoo’s animals will, too. The walls help prevent erosion under the Lincoln Childrens Zoo, plus they help keep vandals from throwing trash and other debris in the animal pens.
“Obviously, we’re always concerned about security and our animals, especially along that perimeter,” said John Chapo, the zoo’s director.