A draft supplemental environmental assessment for repairs to the Ponca State Park backwater site in Dixon County, Neb. is currently available for public review.
The EA evaluates the environmental impacts of repairing damages that occurred to the chute during the 2011 Missouri River flood. These repairs are needed to restore the intended habitat function of the Ponca site and prevent it from degrading further.
The original project, consisting of 29 acres of backwater habitat, was constructed in 2004 on Nebraska Game and Parks land within Ponca State Park boundaries, along the right descending bank of the Missouri River near river mile 754, to function as shallow water habitat with the intent to benefit the federally endangered pallid sturgeon and other native fish and wildlife species.
The 2011 Missouri River flood washed out land that separated the upstream and downstream backwaters, causing a portion of the upstream backwater and entire downstream backwater to function as a flow through chute. This caused sedimentation in the portions of the backwaters that were flowing, making them shallower than desired and filling in the deep-water overwintering fish holes.
The flood also caused approximately two feet of bed degradation in the main channel of the river, which lowered the water surface elevation for a given flow by approximately two feet, causing the water in the constructed backwaters to be two feet shallower than designed.
Proposed repairs are needed to return the site to its original design and functionality and will include excavation and discharge of accreted Missouri River sediments, placement of earthen fill between the two backwater areas, and construction of rock revetment with a covering of fieldstone, topsoil and native grass seed.
Repairs are being made through the Corps’ Operation and Maintenance Program, which, among other things, operates and maintains projects previously constructed through the Missouri River Recovery Program.
Maintenance of these projects helps to ensure they continue to fulfill the requirements of the U.S. Fish and Wildlife Service’s 2003 Amended Biological Opinion for the Operation of the Missouri River Main Stem Reservoir System, Operation and Maintenance of the Missouri River Bank Stabilization and Navigation Project, and Operation of the Kansas River Reservoir System.
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