WATERWAY AND LOCATION: The project would affect waters of the United States associated with wetlands located within the project area of approximately 72 acres situated on 2 parcels. The parcels, located near the Voas Nature Area northwest of Minburn, are owned by Dallas County and managed by Dallas County Conservation Board. Parcel A is within Section 6, Township 80 North, Range 27 West; Latitude 41.766164, Longitude -94.045532; Parcel B is within Section 36, Township 81 North, Range 28 West Latitude 41.778941, Longitude -94.050447; in Dallas County, Iowa.
EXISTING CONDITIONS: The site primarily consists of undeveloped land along Buckeye Creek, surrounded by row-crop agricultural land, a county roadway, and homesteads on neighboring property.
PROJECT PURPOSE/BANK OBJECTIVES: The fundamental objective of compensatory mitigation is to offset environmental losses resulting from unavoidable impacts to waters of the United States (WOTUS) authorized by Department of the Army Permits. The overall goal of the Voas Mitigation Bank Phase II will be to enhance and restore wetlands, wildlife resources, and biological and ecological functions of the watershed by reducing nutrient and sediments loads and creating aquatic and upland habitat. The proposed bank will be self-sufficient by generating income from the sale of mitigation credits to both support initial construction and long-term maintenance of the bank. Other objectives include: provide economically efficient and flexible mitigation opportunities when wetland mitigation is required; support the national goal of no net-loss of waters of the United States; contribute to the long-term health of Iowa’s waterways; enhancement of physical, chemical and/or biological processes that occur in aquatic ecosystems; enhance and restore additional wildlife habitat within the watershed; provide additional flood storage capacity to help prevent flooding downstream of the Bank; fully compensate for wetland losses in a manner which contributes to the long-term ecological functioning of the watershed; create wetland mitigation at a scale that will be most beneficial to the most species and that will be more efficient and affordable to the Sponsor; and provide public hunting, access, and recreational opportunities.
PROJECT DESCRIPTION/BANK ESTABLISHMENT:
a. The bank sponsor proposes to complete activities on a total of 72-acres of property on 2 parcels owned by Dallas County. This project would result in the generation of emergent wetland compensatory mitigation credits. Parcel A (40 acres) and Parcel B (32 acres) will perform wetland restoration on 21.80 acres, wetland enhancement on 6.85 acres of enhancement, and establish a buffer area of 44.48 acres to generate an initial estimate of 35.63 emergent wetland credits. The focus of this mitigation bank will be restoration and enhancement of existing wetland areas. Working with the existing topography, drainage, and ecological features will allow the site to flourish and meet the objectives, including hydrological storage to decrease flooding potential of the surrounding area, water quality improvement of the Des Moines River watershed, and habitat restoration.
b. The design of the mitigation bank will revolve around existing wetland areas in both Parcels A and B. To enhance and restore the areas, excavation will remove some existing surface area to allow for more water storage and potentially tap into groundwater as a source of wetland hydrology. Excavation, soil removal, and shaping will help define the wetland areas and determine water flow based on preferred hydrological course. Some possible design concepts include tile daylighting, replacing perforated tile with non-perforated tile, or installation of a tile riser with a one-way flap gate. After shaping the wetland areas, the landscape will be seeded with native wetland and upland species.
c. The major restoration practice will involve excavation and shaping of designed wetland areas. Wide and shallow berms may be utilized to define the maximum pool elevation and provide a stable overflow, if needed. The shape and structure of the wetland areas will help determine water storage capacity, water flow, and inundation levels of the wetland areas. Unless, otherwise documented in the construction plans, any field tile lines encountered during construction activities plugged or broken to restore subsurface hydrology. Seeding of native vegetation will occur after the earthwork.
d. Additional information on construction/restoration techniques, target plant community types, and detailed planting plans will be completed prior to the submission of the draft Mitigation Banking Instrument.
SERVICE AREA: The proposed mitigation bank will be in the Upper Des Moines Service Area.
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