IDNR presents Fox River dam‑removal study; trustees direct staff to focus on culvert option and keep 'keep the dam' as a public alternative
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Summary
IDNR presented a multi‑year Fox River dam study showing safety and ecological benefits from removal, multiple alternatives to maintain the mill race (culvert options were recommended), sediment testing and IEPA permitting as key constraints, and wide cost‑share differences depending on whether the dam is fully removed. Trustees favored Option 6 (straight culvert) but asked staff to include a 'keep dam' option when presenting to the public and to return with a focused comparison.
The Illinois Department of Natural Resources on Dec. 1 briefed the Committee of the Whole on a multi‑year study of Fox River dam alternatives, emphasizing safety and ecological benefits from full removal but highlighting sediment‑transport, IEPA permitting and local impacts as major constraints.
Tara McParland, acting section chief in the IDNR Office of Water Resources, said the primary objective of the study is public safety: the existing dam produces a submerged hydraulic jump and downstream scour hole that can trap swimmers and boaters. The IDNR ran hydraulic models for low, average and peak flows and presented 10 alternatives ranging from full dam removal to several ways of providing water to the mill race (open channel, modified culvert designs) and a rock‑ramp safety modification if removal proved infeasible.
Sediment was a central concern. The team initially used a 1‑D model and estimated more than $4 million to remove potentially contaminated sediment; a refined 2‑D model and additional sampling narrowed the quantity and produced a range of lower estimates in the study (IDNR cited scenarios in the low hundreds of thousands up to about $1 million for sediment work depending on required dredging and IEPA thresholds). IDNR engineer Aaron Rotherham told the board that several parameters from early sampling “did not fall within IEPA standards,” and the project team is conducting additional grain‑analysis to determine whether dredging or other mitigation will be required.
On alternatives, IDNR said full removal was generally the most effective for safety and ecological benefit and would likely be funded largely by the state (IDNR indicated the state would pay capital and design at or near 100% for full removal). Of the options studied, IDNR recommended two culvert options that would remove the dam while routing water to the mill race; staff identified Option 6 (a straight culvert under the parking area) as the preferred starting point because it is less costly, meets safety goals and preserves mill‑race flow for nearby residents.
Trustees raised questions about aesthetics, changes to the waterfront view, potential impacts on upstream bank owners and liability if the village assumed ownership of a modified dam. Several trustees expressed preference for Option 6 while asking that 'keeping the dam' remain on the public presentation as an alternative the public can review. The board directed staff to work with IDNR and the Fox Valley Park District to refine Option 6 and prepare a focused comparison (Option 6 vs. keeping the dam) for a public meeting, likely in the spring, and to return to Committee of the Whole with more detailed information.
No final decision was made tonight; the meeting was an informational review and staff will coordinate follow‑up meetings, additional technical work with IEPA, and public outreach.
