April 17, 2017
In a draft report, the Little Rock Engineer District is recommending construction of a $137.8 million containment structure to prevent a breach that would halt navigation on the lower McClellan-Kerr Arkansas River Navigation System (MKARNS).
The draft feasibility report and integrated environmental assessment for the Three Rivers South Arkansas Feasibility Study was released March 31. The comment period on the draft report continues through April 30, and the Corps will hold a public workshop about it today (April 17).
The proposed structure would be located between the Arkansas and White rivers in southeastern Arkansas, at the point where the two rivers are the closest to each other. During high water events, water backing up from the Mississippi River can create significant head differentials between the Arkansas and White rivers.
In the lowest 30 miles of the MKARNS, navigation uses a combination of the Arkansas Post Canal, the White River and the White River Entrance channel instead of the Arkansas River, which is too shallow at that point.
“The existing containment structures are subject to damaging overtopping, flanking and seepage that could result in a catastrophic breach,” the study states. Such a breach would cut off navigation for the entire MKARNS from the rest of the inland waterways system.
The problem is not a new one. Engineers have worried about a possible cutoff since the 1970s. In 1992, a multi-component containment system was completed to reduce the chances of erosion that could lead to a cutoff. However, during high water, erosion continues to threaten the system. A study, called the Ark-White Cutoff General Re-evaluation Study, was begun in 2009, but the study was terminated due to potential impacts on the Dale Bumpers White River National Wildlife Refuge, about 64 square miles of which is in the study area.
The recommended plan in the current study is to construct a new 2.5-mile containment structure at an elevation of 157 feet above mean sea level. The planned structure would take advantage of existing high ground, and in most locations would only rise 5 to 7 feet above the ground surface. The structure would cost $137.6 million for construction, real estate, mitigation and interest, but would have a benefit-to-cost ratio of 3.8, the Corps study finds.
The draft report is available for review at: https://go.usa.gov/xX5uu.
The drop-in style public workshop today will be held from 4 p.m. until 7 p.m. at the Delta Rivers Nature Center, 1400 Black Dog Road in Pine Bluff, Ark. During the workshop, Corps representatives will be available to answer one-on-one questions from the public about the study.
Comments can also be mailed to Little Rock Engineer District, Regional Planning and Environmental Center, P.O Box 867, Little Rock, AR 72203-0867; or emailed to 3Rivers@usace.army.mil by April 30.