Ann Arbor Wastewater Treatment Plant Upgrade

Ann Arbor, Michigan

Rehabilitation of the Ann Arbor Wastewater Treatment Plant was the largest capital project undertaken in the city’s recent history. The project included rebuilding half of the wastewater treatment plant and renovating the other half while remaining in continuous service. The City hired Walsh Construction Company to lead the work, and Walsh in turn tapped G2 Consulting Group to oversee the challenging underground work portion of the project.

Fast Facts

Project Owner

City of Ann Arbor


Because most of the work occurred underground, several geotechnical engineering firms were retained by subcontractors to perform work. G2 coordinated these technical efforts for consistency among the various disciplines on site and managed Walsh’s geotechnical risk.

G2 Services Provided

Geotechnical engineering
Geotechnical instrumentation monitoring
Retention wall design


      • One of the great challenges at this project site was the hydrogeological characteristics. The complicated artesian conditions coupled with the depths of required excavations and the presence of the Huron River along the perimeter of the project site required careful consideration and coordination among all the trades involved.  G2 provided an independent evaluation of site dewatering to help expedite the subcontractor submittal approval process and to evaluate the proposed phased dewatering across the site.
      • G2 constructed a mathematical model of the hydrogeological conditions and calibrated the model based on actual pumping and drawdown response on the project site. G2 used existing geotechnical data along with the geotechnical instrumentation data being collected during the course of the project to evaluate how much dewatering to perform during specific underground tasks across the site. This reduced the amount of energy consumed during construction by only pumping the amount required at specific locations.
      • Several small braced excavations were required during construction.  G2 designed earth support systems using the materials and equipment available on site allowing Walsh to self-perform work and expedite the schedule.

Smart. Results. Fast. G2 provided geotechnical solutions to address challenging conditions for this highly visible project, expediting the schedule, reducing costs and managing risk.


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