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

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The presentation described a flood-mitigation storage facility built beneath an existing roadway embankment along I-35. The facility captures sewer overflow during storms and pumps it back into the sewer system afterward. Construction required removing the embankment while keeping the neighborhood noise wall in place. A soil nail wall, temporary bracing, and additional vertical nails helped stabilize the ground, including unexpectedly loose organic material behind the noise-wall posts.<br /><br />Six circular diaphragm-wall shafts formed the tanks’ initial ground support. Because excavation faced significant groundwater pressure, the team designed a dewatering system and used full-scale pump tests to determine the necessary capacity. Seventeen pumps were needed for the first shaft, and 23 ultimately supported excavation of up to two shafts at a time.<br /><br />The speakers emphasized that early collaboration through the CMGC delivery method helped identify risks, plan mitigations, and respond quickly in the field. After nearly five years, the project was completed and can store runoff from a 10-year storm event.

Keywords

flood mitigation

storage facility

sewer overflow

diaphragm wall shafts

dewatering system

CMGC delivery method