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Public works details bridge foundation revisions, dam options and several road project completions
Summary
County public works staff reported changes to bridge foundation design (drill shafts likely preferred over H-piles), possible use of chromium reinforcement bars, multiple road projects nearing completion and a planned environmental-review role for the county on the dam removal EAW.
Blue Earth County public works staff told the board on Sept. 9 that a complex bridge-and-dam project will require revised foundation designs, that the county has received regulatory feedback favoring natural-channel approaches over heavy rock armoring, and that the county will serve as the Responsible Government Unit (RGU) for an Environmental Assessment Worksheet (EAW) for the dam work.
Why it matters: The bridge and dam work affects project cost, schedule and regulatory approvals and could change the county’s capital and permitting approach for the river crossing and dam removal.
Ryan Till, Blue Earth County engineering and public works director, reported that the current bridge foundation design using H-piles is likely to shift to drilled shafts because of scour concerns and the costs of armoring the river channel. Till said MnDOT and consultants will refer the foundation question to MnDOT central bridge and foundation review units for additional peer review. He also told the board that MnDOT’s bridge office had flagged the potential need for chromium reinforcement bars rather than epoxy-coated bars, which he said could be “at least three times as expensive and maybe up to five times as expensive.”
Till summarized meetings with Barr Engineering, TKDA, the Minnesota Department of Natural Resources (DNR), the Minnesota Pollution Control Agency (MPCA) and the U.S. Army Corps of Engineers. He said those agencies provided letters supporting design work that would allow a natural channel stabilization approach rather than extensive rock armoring; he noted varying levels of support but said he has the letters on file.
The county also received a letter from the Governor's EQB that designated Blue Earth County as the Responsible Government Unit for the EAW process; Till said the county’s planning and environmental review staff will handle that review.
Options discussed with Barr Engineering and consultants include: (1) rock armoring (the initial approach), (2) deep bridge pier foundations with minimal armoring, (3) removing the dam without constructing a replacement bridge, (4) removing the dam with minimal armoring, (5) lowering the dam crest and removing the powerhouse, (6) alternative armoring systems (e.g., flexible concrete block grids), and (7) repairing the dam. Till said the county’s board previously directed removal of the dam but that the project team explored all alternatives to identify cost-effective, deliverable solutions.
Till also provided routine project updates: multiple state-aid road projects are in final grading, paving and bridge-beam set stages; a transportation improvement plan draft is posted for public comment through Sept. 24, 2025; and the department has experimented with using an electric-vehicle pickup for flagging operations, which staff reported reduces idling and greenhouse-gas emissions.
Next steps: consultants will continue geotechnical and foundation reviews, Barr Engineering will proceed with soil and hazardous-material assessments for the dam structure, and county staff will discuss project options in a scheduled work session. Formal design, permitting and cost-estimate updates will follow consultant peer review and agency feedback.
