Over the past several decades, I-35W at 42nd Street, a major interstate artery in Minneapolis, has experienced flooding during intense storm events. Additional stormwater storage requirements prompted the Minnesota Department of Transportation (MnDOT) to hire Barr to develop flood-risk-reduction concepts. Complex hydraulic modeling, the need to understand ground conditions, and a restricted surface workspace posed challenges. The limited footprint and high groundwater conditions meant that the solution might require deep structures, such as tunnels and/or shaft-type construction. Barr provided geotechnical data of the underlying soil and bedrock conditions; accurate hydraulic modeling; and constructible concepts that not only met the hydraulic objective but also considered the challenging geologic conditions.
Barr led a multi-partnered team in final design of a 14-acre-foot stormwater storage facility to reduce highway flooding with the goals of maintaining a 100-year design life, minimizing life-cycle costs, reducing groundwater infiltration into the facility, and optimizing long-term maintenance. We completed hydraulic and structural design, including design of a weir structure to convey flow into the stormwater storage facility, connections between cells, and evaluation of impacts on water levels. We also developed a geotechnical monitoring program to provide baseline and construction monitoring for the duration of the project. Construction was substantially completed in November 2023.
