Installation of Fiber-Optic Cables Under Flood-Protection Structures Using Horizontal Directional Drilling Techniques

Abstract : Increased use of communications cables has increased the frequency of requests to install cables and other utilities under flood-control levees. The U.S. Army Corps of Engineers, specifically the U.S. Army Engineer District, St. Louis (CEMVS), has allowed the use of horizontal directional drilling (HDD) for cable installation beneath levees along the Mississippi, Meramec, and Wood Rivers. Installations were successful because of careful assessment of subsurface geotechnical conditions prior to initiating field activities, careful specifications, and monitoring of fluid pressures and other critical parameters throughout field operations. This report describes the process of planning, installing, and monitoring HDD under levees at two projects for CEMVS. Utility installations of this type can be completed without damage to the levee in appropriate geologic settings as long as the operation is conducted in a manner that does not fracture the levee blanket or topstratum. Key parameters in the St. Louis experience, in addition to geologic setting and monitoring of fluid pressures, included set-back distance on the landward side of the levee for initiating the drilling, and drilling beneath the levee and river at a depth adequate to contain the drilling operation in bedrock.