LOCATION OF PROPOSED ACTIVITY: The project would affect waters of the United States associated with 2 unnamed tributaries to the Platte River and associated emergent and forested wetlands. The project/review area is located on an approximately 156-acre parcel located approximately 4,500 feet north of 100th Road, west of Winchester Avenue and one mile northeast of Athelstan in Section 22, Township 67 North, Range 32 West; Latitude 40.5846081 and Longitude -94.5146447; in Taylor County, Iowa.
PROPOSED ACTIVITY: The applicant is requesting a DA permit to develop a stream and wetland mitigation bank to aid in offsetting environmental losses resulting from unavoidable impacts to waters of the United States authorized by DA permits.
EXISTING CONDITIONS: The site primarily consists of agricultural land along the Platte River with 2 streams within the property, surrounded by row-crop agricultural land, and a county roadway.
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. Other objectives include: to provide economically efficient and flexible mitigation opportunities, support the national goal of no net-loss of Waters of the United States, restore and enhance terrestrial and aquatic habitat, reduce flooding by re-meandering the stream and reconnecting the stream to its natural floodplain, provide additional flood retention and reduce impacts of downstream flooding by capturing and storing water from high flow events, and improve water quality by reducing sediment and nutrient loads.
PROJECT DESCRIPTION/BANK ESTABLISHMENT: The bank sponsor proposes to complete activities on approximately 156-acres of property owned by SCP Platte River, LLC. This project would result in the generation of emergent wetland, forested wetland, and stream compensatory mitigation credits. The goal of this project is to restore 103.68-acres of emergent wetland, enhance 2.09-acres of forested wetland, establish 34.64-acres of buffer to generate an initial estimate of 113.39 wetland credits. The project will also restore 2,410 linear feet of stream with buffers to generate an initial estimate of 39,335.82 stream credits.
A. Emergent wetland restoration for this project will include shallow excavations that would allow water to pool in the wetlands, creating scalloped edges and an undulating bottom to ensure a diverse wetland habitat. The shallow excavations will receive hydrology from daylighted and disabled tile lines, installation of ditch plugs to keep water from draining off the Bank Site, overland flow, direct precipitation, and overbank flooding from the UNT and the Platte River.
B. Forested wetland enhancement for this project will include increasing hydrology through daylighting and disabling of agricultural tile lines. Enhancement will also include controlling undesirable vegetation and planting of native hydrophytic species to increase species diversity.
C. Stream restoration for this project will include realignment and re-meandering in areas needed to restore sinuosity which will increase the flood storage capacity and reduce the velocity of the stream, minimizing streambank and streambed erosion. The streambanks will be sloped and shaped, placing toe wood for protection. Raising the streambed to a higher elevation will reconnect the stream to its floodplain and a step-pool structure will be installed at the Platte River confluence to provide vertical stability and prevent future streambed erosion. In-stream habitat features such as pool/riffle/run complex structures will be installed utilizing native rock and trees removed during construction.
D. Wetland and stream buffer areas for this project will be established by controlling invasive and undesirable plant species through herbicide treatments. Reestablishment will include planting the areas to restore streambank stability, improve water quality, and to improve habitat.
E. Additional information on construction 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 Lower Missouri Service Area.
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