The five-year, $99.4-million renovation of Ann Arbor’s wastewater treatment facility alongside the Huron River began with construction of new floodwalls that eliminated requirements for meeting 100- and 500-year floodplain construction criteria.

Walsh incorporated a maintenance of plant operations approach to the preconstruction plan so that the plant could continue functioning throughout the five-year construction period. Preparing for the construction phase also required a sitework sequencing plan to relieve pressure on an underlying aquifer as well as previous measures to ensure uninterrupted treatment.

That included a carefully phased upgrade of the site’s electrical distribution system and rerouting utility lines through areas of congested underground piping so that portions of the facility could be taken out of service for demolition and installation of new high-efficiency process equipment.

As the project progressed, portions of the work were resequenced to benefit the overall schedule, budget and working conditions. Multiple work areas were opened for mass excavations and concrete operations simultaneously, which greatly enhanced productivity.

Along with increasing capacity, operational quality and discharge quality, the project also enhanced the plant’s environmental footprint through improved stormwater features such as installation of porous pavement, rain gardens, swales, detention ponds and hydrodynamic separators.