MnDOT's I35W Stormwater Storage Facility - Flooding Resolution in Challenging Ground using a Series of Six Diaphragm Wall Cells-PPT Presentation

PPT Presentation

Pdf Summary

The I-35W Stormwater Storage Facility was built to reduce flooding and improve safety along a critical traffic corridor. It comprises six underground storage tanks and required excavation beneath an existing embankment while maintaining a nearby noise wall and working around utilities.<br /><br />A soil nail wall supported the excavation and carried earth, surcharge, and noise-wall loads. Its design accounted for wind loads on the noise wall and avoided conflicts with its posts and existing utilities. Helical anchors braced the noise wall, while vertical soil nails helped stabilize unraveling ground during excavation. The completed wall allowed the noise wall to remain in place and provided a work platform for constructing the storage tanks.<br /><br />Six diaphragm-wall cells were designed to withstand earth and hydrostatic pressures. The design also considered shaft uplift, base-slab resistance, and the connection between the final lining and diaphragm panels. Deep depressurization wells were used to control groundwater and prevent piping failure. The well system was tested and adjusted using instrumentation, with additional pumping capacity provided to mitigate rapid groundwater recharge.<br /><br />Before excavating each cell, the team conducted pump tests to confirm that groundwater objectives had been met. Up to 23 wells operated simultaneously and were moved between cells as work progressed.<br /><br />The presentation credits careful design and early contractor involvement with identifying risks and developing mitigation measures, helping reduce field costs and schedule impacts. The completed facility is intended to lessen flooding and improve safety on I-35W.

Keywords

I-35W

stormwater storage

flooding mitigation

underground tanks

soil nail wall

diaphragm wall

groundwater control

depressurization wells

excavation support

traffic corridor safety