Ketchum Dam Removal & Rice Creek Improvements
City of Marshall
The public was opposed to abandoning the mill race, so P&N heard their concerns and addressed them with a environment-enhancing solution.
For over 100 years, the Ketchum Dam diverted Rice Creek from its natural channel and directed 90% of its flow into a man-made mill race parallel to the creek. Marshall and the MDNR wanted to abandon the aging dam and restore the creek to its original channel.
The City retained P&N to study the situation and create a plan to re-direct the flow. P&N teamed with stream restoration specialists Milone & MacBroom of Connecticut, the City of Marshall, the local Conservation District, the Calhoun County Road Commission, and the MDNR.
Challenges & Solutions
The public was opposed to abandoning the mill race, as it passed through Ketchum Park and was crossed by an attractive pedestrian bridge. P&N met with and worked extensively with adjacent property owners and local citizens to hear the concerns. To “remove” the Ketchum Dam, the project team designed and a diverting channel upstream of the dam, eliminating all flow over the crumbling dam and drying up the reservoir beyond it. The diversion was located just downstream of the pedestrian bridge, so park users can still stand on the bridge and see a flowing stream below it. The dam remnant still stands at the end of the dried-up reservoir, which is now re-vegetated.
Due to sediment and vegetation, the original creek channel no longer had the capacity to handle flood flows without seriously impacting neighboring properties. P&N designed a rock weir where the original channel and mill race diverged about one mile upstream of the mill race dam. The weir directs half of Rice Creek’s normal flow to the original channel and half to the mill race.
An extensive HEC-RAS hydraulic model helped the design team fine-tune the rock weir’s geometry and evaluate different scenarios. Engineers found that the new flow-split actually improved conditions for adjacent homeowners compared to the previous diversion of the mill race and the original channel.
The former dam created a warm pool of water with low dissolved oxygen content, which is an unfriendly environment for many creatures. It also obstructed upstream movement of fish and other species, fragmenting the ecosystem. Animals can now navigate upstream over a more natural, faster-flowing stream bed.
The water surface level upstream of the rock flow-splitting weir dropped by about two feet, narrowing the impact of the surrounding wetlands. The Calhoun County Road Commission plans to include a new bridge over Rice Creek in the future, and the lower water level will allow for a more affordable, shorter-span bridge.
Funding was provided by the City of Marshall, an Inland Fisheries Grant from the MDNR (Fisheries Division), and a Soil Erosion and Sediment Control Grant from MDEQ’s Office of the Great Lakes.
“Removing the dam is expected to cool temperatures in the waterway and boost fish movement in coming seasons. That stretch should now be able to support higher populations of trout.”
– Scott Hanshue, DNR Fisheries Division Biologist
2010 Project of the Year Award (Environmental) American Public Works Association, Michigan Section
Jim Hegarty, PE, 616-364-8491