The man made block would be lowered about two feet for a distance of about 50 feet. Replacing the existing corrugated metal pipe principal spillway. The auxiliary spillway will be modified to lower its' elevation by about three feet. The actions in the proposed plan for Lawson Creek Watershed will control gully erosion for 50 years at Site 1-1, reduce sheet, rill and ephemeral cropland gully erosion in the watershed above the site, reduce delivery of sediment both to the structure site and the Maple River, provide a source of water for minnow species in the structure pool, and reduce downstream peak flows. There are three cultural resource sites recorded in the area.
None are in the area of potential effect.
Following its procedures, NRCS surveyed the area of potential effect and no sites were identified. Construction discoveries will be handled in accordance with NRCS General Manual, Section 420, Part 401. The Loess Hills are a nationally significant natural area. The installation of the project measures will prevent gully damages to this portion of the Loess Hills. The planting of native vegetation as per Iowa NRCS specifications for restoration of rare and declining habitats on the 49 acre easement area will help restore native prairie vegetation to this portion of the Loess Hills.