Zoar Levee Interim Risk Management

The U.S. Army Corps of Engineers elevated Zoar Levee and Diversion Dam to a Dam Safety Action Class I (urgent and compelling) ranking due to seepage concerns. An accelerated program is in progress to address project deficiencies which include seepage through the levee’s glacial outwash foundation, through a fractured rock knoll beneath the levee, and through the dam’s fractured rock abutments and foundation. These deficiencies have resulted in large uncontrolled seepage quantities and erosion which required significant intervention during past flood events. With an interim risk reduction measure plan in place, and while emerging risk and reliability approaches and guidelines are being utilized to develop a comprehensive project risk reduction measure plan, a number of interim measures have recently been designed and implemented at Zoar Levee. Recent structural measures include toe drain and collector system construction and relief well system rehabilitation and enhancement (i.e. lowering of well riser elevations, replacement of dysfunctional wells, wells redevelopment, and abandonment of relic wells directly beneath the levee footprint). This paper presents a summary of the Zoar Levee project history and focuses on the recent implementation of structural and non-structural interim risk reduction measures. It also discusses the Zoar Levee relationships with other Muskingum River Basin projects (including Bolivar Dam located just upstream of Zoar) which complicate flood risk reduction management, and provides an overview of recently implemented risk reduction measures at Bolivar Dam which additionally benefit Zoar.