— Post-tensioned rock and concrete anchors consist of high tensile strength bars or strands installed in drilled holes which are subsequently tensioned.The anchors provide lateral and vertical load capacity for the installed structures to resist movement. The anchor bottom is bonded to rock or concrete by a cement grout, resin, or can be fixed by a mechanical anchor. The upper portion, or free length, is initially left ungrouted for prestressing; then subsequently grouted to lock in the tension and provide additional corrosion resistance. Rock anchors are used as a cost effective solution to tie down and tie back dams, towers, bridges and other critical structures, for seismic retrofitting, to anchor raft foundations below the groundwater table, and to secure caisson bottoms. Anchors have the design advantage of being able to provide support at hundreds of feet in depth with relatively limited access and disturbance. Corrosion resistant anchors are also available should the project be located in a harshly corrosive environment.