A city-ordered flood mitigation study identified measures that could protect the stores in the East End Plaza from future floods.
Stores in the plaza flooded in both the 2015 and 2017 floods, forcing businesses to close temporarily. Some chose to relocate rather than return to the flood- prone area of the city.
Following the 2017 flood, Cherie Francois, a plaza property owner, asked the city to study the feasibility of installing backflow prevention at one of the culverts beneath the railroad tracks.
When the city contracted with HR Green to study flood mitigation throughout the city, engineers were asked to include the East End Plaza in the study.
Engineer Chad Mason, with HR Green, presented highlights last week to the board of aldermen of the technical memorandum on a flood mitigation study the firm prepared for the city.
Mason and Engineer Josiah Holst offered three alternatives that could prevent future floods in the plaza stores.
One alternative would integrate a closure device, or floodgate, at or near the railroad culvert with a basin to allow temporary pumping. This would include a backflow prevention gate at the culvert and adjacent detention basin and pumping station on the north side of the railroad tracks.
Total cost of the option is estimated at $2,258,000.
A second alternative includes the closure device or floodgate, plus an upstream detention basis to reduce pumping needs at the plaza at a cost of $3,866,000.
If nothing is done, the study noted the plaza will continue to flood.
A third “no build” alternative took into consideration the relatively small footprint of the plaza, saying it might be a good candidate for protection with temporary flood barriers.
The study noted that the owners of the plaza are not seeking the ability to maintain business operations during a flood. Business operations can be closed for a few days until floodwaters recede.
Temporary flood barriers could be installed very close to the building edges, minimizing the total length of barrier needed. Approximately 1,500 linear feet of flood barrier would be needed to completely encapsulate the plaza building complex.
The FEMA HMA grant program provides funding to states, Indian tribal governments and communities to implement cost-effective measures that reduce or eliminate the long-term risk of flood damage.
The HMA program has five categories of grants. Two of these are potentially applicable to the project alternatives described above: Flood Mitigation Assistance (FMA), and Pre-Disaster Mitigation (PDM).
The FMA program provides 75 percent of project costs to successful applicants, with the applicant providing the remaining 25 percent.