River Diversion, Contaminated Sediment Removal, and Ecosystem Restoration

Kalamazoo River Superfund Site, Michigan

A mill that de-inked carbon paper contaminated the Kalamazoo River Site with PCBs. Over several decades, process water released into Portage creek, a tributary of the Kalamazoo River, contaminated a large portion of the surrounding floodplain. The U.S. Army Corps of Engineers (USACE) hired Weston Solutions, Inc. (WESTON^®) to conduct an emergency response remediation of Portage Creek and restore the site back to its natural state. The project required rapid deployment to protect the downstream waters of Portage Creek from PCBs since sediments from upstream reaches posed a threat of downstream contamination.

Rapid Response and Restoration

Remedial operations to remove 145,000 cubic yards of PCB-contaminated sediments required stream diversion to protect downstream receptors from PCB migration. To return the river and surrounding area to its original configuration, WESTON worked with USACE to develop a plan to restore pre-existing stream corridor meanders and connections between existing wetlands and floodplains.

Natural materials, including tree trunks and boulders found on-site, supported floodplain and stream restoration, ultimately returning impacted areas to productive, natural habitats. Native wetland species and seed mixes were used to accomplish rapid site revegetation, minimizing invasive plant encroachment.

WESTON provided predesign, design, and construction services; developed the work plan and sampling plan; redesigned an existing water treatment plant; and removed and placed PCB-contaminated river sediments in on-site lagoons. Excavation and contaminant removal was conducted to a depth of 3 to 6 feet from the 23-acre floodplain.

River Diversion, Erosion Control, and Dredged Material Disposal

Portage Creek had to be diverted to excavate both sides of the creek and the creek bottom while protecting downstream water from PCB migration. Once the project was completed, a downstream dam was left in place and incorporated into the remediated landscape. The excavated material was transported to an on-site containment cell that was constructed outside the 100-year floodplain. After placement of the material, the potentially responsible parties (PRPs) installed a final cap.

During construction, WESTON used various forms of temporary erosion-control measures, including riprap and temporary sheetpiling. WESTON used large trees felled during clearing and grubbing as a form of erosion control and a component of restoration in areas of high hydraulic friction.

Site Installation and Project Planning

Throughout the project, WESTON considered existing field conditions related to future project requirements.  For example, the excavation and creek diversions generated water that required treatment for PCBs and total suspended solids at an existing on-site treatment plant. WESTON reengineered the existing treatment facility to increase the treatment capacity to 100 gallons per minute and to accommodate treatment of PCB-contaminated water. WESTON treated nearly 8 million gallons of water with 99% online utilization and collected water samples to test for PCBs and metals prior to discharge of treated water into publicly-owned treatment works.

WESTON worked closely with the USACE to maximize fieldwork efficiencies by gaining on-site approval for design modifications, such as variations to the required depth of excavations, backfill options, and alternative placements of wetlands plantings. With the project focused on safety, over 40,000 hours were logged without a recordable incident.

Ecological Restoration and Geotechnical Sampling

Site restoration was completed with the seeding and planting of more than 5,000 indigenous wetlands-species plants. The plantings will reduce erosion and improve habitat by providing nesting areas and natural cover for animals and birds. A global positioning system (GPS) was used extensively throughout the restoration process. WESTON used GPS to locate and document sampling locations along 50 x 50-foot sampling grids, and to restore the stream to its original location once remediation was complete.