Constructing a Stormwater Storage Facility in a Glacial Valley Using CMGC Project Delivery-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes construction of the I-35W stormwater storage facility in Minneapolis, designed to reduce flooding in a critical traffic corridor by adding 14 acre-feet of surge capacity to existing infrastructure.<br /><br />The project used Construction Manager/General Contractor (CMGC) delivery, bringing the owner, designers, and contractor together to develop the scope, refine the design, manage costs, and address construction risks. The facility is located in a buried glacial valley, where challenging ground conditions—including high blow counts, cobbles, boulders, and very dense layers—complicated investigation and construction.<br /><br />Design options were evaluated to optimize storage-shaft geometry and drainage. The final design consists of six independent, unreinforced shafts and a lift station. Earlier alternatives included different numbers and depths of shafts, gravity drainage, and incorporating the weir structure into the storage shafts.<br /><br />A major construction challenge was building approximately 112,870 square feet of diaphragm wall across 48 panels while encountering potential obstructions. The team used excavation equipment and digital output to identify obstructed layers, track excavation progress, and record boulder-retrieval frequency and associated delays. This transparent documentation helped quantify unforeseen conditions and support change management.<br /><br />CMGC enabled the team to share risk through a risk register and risk pool, select suitable tools and equipment, improve constructability, and respond efficiently to challenges. At the time of the presentation, completion was anticipated by December 2023. The facility was expected to reduce flooding and improve safety along the corridor.

Keywords

I-35W

stormwater storage facility

Minneapolis

flood mitigation

CMGC delivery

diaphragm wall

buried glacial valley

construction risks

lift station

surge capacity