County trustees approve IDALS prep wetland to reduce nitrates in subdrainage district 155

Wright County trustees approved a prep wetland project proposed by the Iowa Department of Agriculture and Land Stewardship (IDALS) intended to remove nitrates from agricultural runoff in subdrainage district 155.

IDALS engineer Sarah Smith described the project's purpose and design, saying the wetland is sized to detain runoff and foster microbial nitrate removal. "The purpose is to remove the nitrates from agricultural runoff and from tile water," Smith told trustees, adding that IDALS had obtained DNR and U.S. Army Corps permits and sought district approval to proceed to bidding and construction.

The design includes a shallow treatment pool roughly 1.1'1.2 feet deep, a sheet-pile flow weir, auxiliary spillway, a water-control structure with stop logs and an NRCS-compliant sediment forebay. IDALS said the project will daylight and reroute private tiles into the pool where feasible, will install non-perforated tiles within the conservation easement to limit root intrusion, and will place a conservation easement with the Peterson family enforced by the Soil and Water Conservation District.

Trustees discussed maintenance responsibilities, drainage-assessment implications for district landowners, and contingencies in case construction affects existing tiles. IDALS committed to repair tiles that its work damages and to a post-construction inspection schedule led by a wetland field specialist. The board voted to approve the project and IDALS's design and proceed with bid and construction steps.

What happens next: If the project proceeds, IDALS will go to bid (anticipated in July), convene preconstruction meetings with the county and landowners, and implement construction under NRCS standards; maintenance and monitoring plans will be coordinated through the Soil and Water Conservation District and the landowner conservation easement.