Project Location: The proposed site consists of an approximately 2,982-foot section of Jim Creek, east of Dexfield Way and west of Creamery Road within Section 31, Township 78 North, Range 29 West, Dallas County, Iowa. See attached location maps. Latitude 41.504978, Longitude -94.228486.
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. Other objectives include the enhancement and creation of additional wildlife habitat, the restoration of native vegetation within the riparian buffer, re-meandering and pulling back of streambank slopes to increase stream stability, the construction of floodplain benches to provide a floodplain connection for frequent flows, and to provide stream mitigation credits for project impacts proposed by other entities.
Project Description/Bank Establishment: The bank sponsor proposes to complete activities in one phase on 45.12-acres of property in Dallas County, Iowa. The creek occupies 2,982-linear feet and the proposed conceptual alignment would re-meander the channel to a length of approximately 3,478-linear feet. This project would result in the generation of approximately 48,676 stream compensatory mitigation credits. As it currently exists, the channel is relatively narrow and is deeply incised with nearly vertical slopes. The proposed alignment is designed with the intention of simulating a natural meander within the channel to reduce the risk of erosion, provide an immediate floodplain connection, and increase stability. The alignment was developed to maximize the length of the new channel while maintaining a minimum radius of curvature for stability. An undetermined amount of rock riffles will likely be placed within the upper reach of the stream channel for further grade control, stability, and to provide habitat. The Rosgen Bank Erosion Hazard Index (BEHI) method was used to assess the current stream configuration and will also be used to verify the channel performance post-construction along with HEC-RAS modeling software. Other improvements associated with the project include restoring and creating a diverse riparian buffer habitat of native mesic species. Vegetation will be managed by periodic mowing, prescribed fire, herbicide application, and seeding with native species. Additional information on construction techniques, target plant community types, and planting plans will be completed prior to the submission of the draft Mitigation Banking Instrument.
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