Route 66 and Illinois Avenue Flooding

The Problem

The intersection at 7th Street and Illinois Avenue would frequently flood along Illinois Avenue during a 25-year or larger storm. At times, the water level would rise as much as 4.3 feet above the edge of the road. This flooding would cause damage to commercial properties and a general nuisance of road closure for a significant traffic route in the City.

Joplin Creek

Joplin Creek East is the primary drainage channel for the relief of this area. Part of the solution to the 7th and Illinois flooding problem was to both deepen this channel by two feet as well as widen the channel on the east side. We designed a concrete modular block retaining wall for the widened east side. The combination of deepening and widening the channel provided for a larger volume of stormwater runoff into Joplin Creek. Along this wall and into the parking lot we also designed new curb and gutter, drainage flumes, and new pavement.

Two pedestrian bridges crossing the channel were replaced as well as several utility relocations. A triple box culvert was designed and installed on the furthest upstream portion of the project. An existing bridge between two of the commercial buildings was retained as well as an existing pedestrian bridge downstream of that. These structures could be retained due to the increased capacity of the channel. The channel widening continued north of 7th Street into Ewert Park.

The west side of the channel was not improved for this phase of the project. The owner of the commercial development on the west side is considering a Riverwalk feature on the west side.

Illinois Avenue

Because of the increased capacity of Joplin Creek, which can now pass the 100-year design storm, new curb inlets and road cuts across to the west side of Illinois Avenue allowed for a greater volume of stormwater to drain. There is also a significant upsize in the stormwater pipe, 48-inch diameter RCP, that collects the stormwater from Illinois Avenue carrying it under the north parking lot of the Joplin Plaza and into Joplin Creek. Now, both the increased capacity of Joplin Creek and the larger volume of drainage on Illinois Avenue relieve the previous flooding issues.

7th Street Box Culvert and Ewert Park

This project also involved the Missouri Highway and Transportation Department because the box culvert underneath 7th Street crosses a Missouri highway, Route 66. We submitted plans to MODOT for approval which required us to close the highway for a week to install a new precast box culvert additional cell. The new cell was added to the existing double box culvert, making it a triple. By lowering the flow line in this new cell, we were able to lower the water surface elevation upstream on Illinois and in Joplin Creek. This work eliminated the bottleneck that used to occur on the south side of 7th Street.

This project was funded with the City of Joplin’s stormwater sales tax. The design was completed in 2018. Construction began in 2019 and was completed in 2020. This project has performed as expected and been a great success!