State biologist outlines $680,000 plan to replace twin culverts under Grouse Avenue; seeks county partnership for federal grant

Rob Patterson, a biologist with the Iowa Department of Natural Resources, told the Worth County Board of Supervisors that the agency is pursuing a federal grant to replace two large culverts under Grouse Avenue that serve as the water-control structure for a nearby marsh.

Patterson said engineers estimate the overall project at about $680,000, with roughly $500,000 of that cost covering precast concrete culvert units placed under the roadway.“It’s just a project for us to easier manage it, for us to get in there and do what we have to do easier,” Patterson said, explaining the work would include concrete culverts and new stop-log bays to allow more reliable water-level control.

The project would replace the existing twin steel culverts that Patterson said likely date to the 1960s or 1970s. He told the board the structures are large (roughly 9–10 feet in the existing configuration) and stressed the replacement would be designed so staff can raise and lower stop logs for annual marsh management and for migrating waterfowl habitat.

Patterson said the agency is seeking a local partner statement from Worth County to strengthen the grant application. He asked whether the county could consider a cost share; previous discussions had referenced a possible 50/50 split but Patterson said he deferred to the board on what contribution it would accept.

Board members and county staff asked technical questions about box-span sizes and whether using a single larger span was feasible. Patterson said precast box spans larger than about 14–16 feet are uncommon and that the project likely would match the existing size to preserve stop‑log function and operational access. He noted that if the combined span were to exceed 20 feet, the structure could be classified in the National Bridge Inventory (NBI) and become subject to inspections every two years, which would add a long-term maintenance cost for the county.

Patterson said construction timing is tentative; the agency’s engineers anticipate construction in roughly February of a future year, and the federal grant application is due this summer. He said DNR’s engineering team would be on site the week following the meeting and offered to provide the board a more detailed plan and a draft partner letter for the county to consider and, if appropriate, sign.

Board members asked the agency to check existing mapping for the spacing between the twin culverts to avoid triggering an NBI classification. They also asked the agency to return with a clearer cost-share proposal and life‑expectancy estimates for the replacements before making a funding commitment.

Patterson said the DNR would follow up with engineering plans and a draft partner statement for the board’s review.

The board took no formal funding vote at the meeting; Patterson left the board with a request for feedback and said a formal county commitment would help the grant application.