In the heart of Milwaukee’s Historic Third Ward, where the city’s rivers wind through a bustling urban landscape, an environmental challenge lurked beneath the surface of the Milwaukee River.
Two sites within the Milwaukee Estuary Area of Concern (AOC) held deposits of non-aqueous phase liquids (NAPL). NAPLs are organic chemicals like oil, grease, and industrial solvents that do not mix in water or break down easily and can linger in soil and sediments for years. The NAPL-laden sediments at these two river sites were the result of more than 150 years of industrial development, including a former manufactured gas plant.
The presence of these impacted sediments posed a threat to public health and prevented people and wildlife from fully using the waters within the Milwaukee Estuary AOC.
In total, the two sites contained 45,000 cubic yards of NAPL-impacted sediment. While this represents only a small portion of the AOC’s total impacted sediments (including approximately 1.4 million cubic yards of polychlorinated biphenyls (PCBs) and metal-impacted sediments throughout the estuary), these NAPL deposits required remediation.
The remediation challenge was complex. The client turned to GEI for comprehensive support to complete the pre-design investigation, remedial design, and implementation of the remedy addressing the two NAPL-impacted sediment deposits.
Tackling Urban Waterway Remediation
This would be the first contaminated sediment dredging effort in downtown Milwaukee. As a result, our team’s work would define permitting requirements that would assist future remediation efforts in the AOC.
To prepare for the cleanup effort and minimize the project’s impact on the community, GEI designed and installed a comprehensive monitoring system to ensure public safety by tracking air and water quality, noise and vibration, and structural stability and movement.
The underwater environment revealed its own set of obstacles. The team encountered unexpected utility lines, subsurface debris such as wire, cable, piping, and bricks, and abandoned historical infrastructure including cast-iron sewer pipe and telephone cables. These discoveries required the team to respond with creative engineering solutions without slowing project momentum or sacrificing environmental and safety standards.
GEI and our project partners designed and installed an underwater support wall to protect existing infrastructure from damage to facilitate the dredging.
Environmental Restoration and Material Management
With scarce available property to manage the sediments and water and wanting to avoid adding to downtown Milwaukee’s traffic congestion, the team pumped the dredge stream more than 2 miles away, to the Milwaukee Dredged Material Disposal Facility (DMDF) for dewatering, water treatment, and long-term containment.
The remediation process successfully removed the NAPL-impacted sediment from both sites on the river.
Following sediment removal, dredged areas were capped with clean sand to restore the riverbed. In locations where contaminated sediments could not be removed, an engineered final cover was installed to sequester the sediments in perpetuity.
A Model for Future Remediation Efforts
The project’s successful completion represented more than just an environmental win—it established a precedent for future remediation work in the AOC. As one of the first downtown dredging projects undertaken as part of the Milwaukee Estuary AOC cleanup, the work sets the standard for sediment remediation while demonstrating how complex urban environmental projects can be executed with minimal disruption to community life.
This award-winning initiative also opened doors to significant federal funding for continued environmental restoration in the Milwaukee Estuary AOC. The collaborative approach and technical excellence displayed throughout the project showcase how urban environmental challenges can be transformed into opportunities for community enhancement and ecological restoration.
For the City of Milwaukee, and the wider community, this project demonstrates that even the most complex environmental remediation can be accomplished successfully in the heart of an urban environment, benefiting both present and future generations who call Milwaukee home.
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