Engineered Riffles on Portage Creek, MI – Design, Post-Construction Monitoring, and Lessons Learned
Janeen McDermott, PE
AECOM
Southfield, Michigan
The Alcott Street Dam on the Portage Creek, a tributary to the Kalamazoo River, in southwestern Michigan, was built in the late 1800s to divert water flow to provide mechanical power and process water for a now-closed paper mill. Papermill operations resulted in releases of polychlorinated biphenyls (PCBs) to the downstream Portage Creek and Kalamazoo River, and Portage Creek was later designated as an area of environmental contamination. To mitigate risk conditions, the United States Environmental Protection Agency (U.S. EPA) completed a Time-Critical Removal Action in 1999 that removed and backfilled the PCB-impacted sediments. During this process, any remnants of the pre-dam channel were destroyed.
The State of Michigan then later sought removal of the Alcott Street Dam due to it being obsolete and of no functional use. Removal of the dam restored 3,000 feet of stream channel and connected the creek to one mile of restored waterway upstream and three miles of creek downstream providing direct access to the Kalamazoo River. The design of the dam removal and river restoration established the restored river channel on non-native and imported soil since the pre-dam channel and floodplain material had been destroyed by previous dredging and remediation work.
The design established five engineered rock-riffle structures to stabilize the restored river channel and tie in the proposed project to the existing channel elevations bounding the project area. It was also important that the riffles did not impede fish passage as that was a main goal of the project. The riffles were designed to be 100-ft long with a 1.2% slope and consisted of a heterogeneous mix of rock sizes intermixed to optimize targeted flow conditions (e.g. velocity, flow, and depth). Additionally, boulders were incorporated into the riffle design for stability and to provide boundary roughness elements for fish passage.
This presentation reviews the design need for engineered riffles, investigates the design approach, details, and the lessons learned from three years of post-construction monitoring. Lessons learned include how to modify the riffle design to further prevent lateral bank erosion as well as presentation of fish survey data pre- vs post-project.
About Janeen McDermott, PE
Ms. Janeen McDermott is a water resources engineer residing in the beautiful State of Michigan where the Great Lakes and freshwater abound. She grew up fishing and exploring the natural resources Michigan has to offer, inspiring her interest in water resources. Since graduating from Michigan State University in 2010 and completing her master’s degree from Wayne State University in 2014, Janeen has worked on a wide variety of projects for local, state and federal agencies and private clients. When not working, Janeen enjoys spending time outdoors with her husband and three children.