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The high line system has several uses in rope rescues. It can be used for both high- and low-angle applications. It can be used to extricate victims from or move resources into high-rise structures where elevators and stairways are not an option. It can be used to move victims or equipment across natural terrain features such as gorges and ravines, large or fast-moving bodies of water, and contaminated areas. The technique is time consuming to implement and complicated to learn, but is worth having and keeping in the rope-rescue tool kit.
There are several versions of the high line that can be set up. The U.S. Army's Mountaineering Field Manual has a single track line/double tag line system that is easy to set up and operate, but requires additional safety precautions. There are several systems that use specialized equipment such as the Kootenay pulley, but for our training scenario, we decided to go with a simple system that would ensure safety. We wanted to work with a double track line system that could be operated using just the equipment available in our standard heavy technical rescue kit.
To start with the rigging up top, we needed three bags of 150-foot ropes (rope lengths must be determined by the operational location). Most agencies want five-eighths-inch rope due to the strain placed on the ropes. Using this system, we lowered a 200-pound dummy from a 60-foot height with no trouble. We also brought up four six-foot utility straps for anchoring, nine carabiners, four pulleys and a litter basket rigged for vertical lowering. A brake rack descent device also was brought up because we wanted to use it to control the descent and needed something with more control than a figure 8.
We established two anchor points for fixed lines called "track lines." These lines were then routed through a third anchor point that used two carabiners to act as a directional and a high point (photo 1). During our after-action review, we felt this station would have been better served with a double pulley. These lines were then lowered to the ground. The fourth anchor point was used to establish a lowering system using the brake rack (photo 2). This line was attached to the head end of the basket litter. At first glance, the litter seems to be rigged for horizontal lowering with four pulleys rigged to it; two at the head and two at the foot. However the attachment point to the track line is for vertical lowering.
At the bottom we used two fire department vehicles, two six-foot utility straps and six carabiners. It is recommended that anchors be separated by 10% of the distance the load is expected to travel and at a distance from the high point to allow a 45-degree angle on the track lines. We eyeballed the distance for the 45 degrees and parked the vehicles 15 feet apart. We then established an anchor point with a pulley on eyebolts on the front of each vehicle. We captured the lowered track lines and routed them toward each other through the appropriate pulleys.
There is a rather cumbersome formula for calculating the 10% slack needed in the track lines during the operation. You can also use a 2:1 or 3:1 mechanical advantage system to take the slack out of the lines. We decided to use the less cumbersome self-equalizing system where each track line would back up the other. We tightened up the track lines until they met between the two vehicles with enough "tail" on each rope to reach the anchor point of the other rope. One team member stood between the two track lines about 20 feet from the anchor points and held the lines together to place the desired amount of slack in the lines. As he did this we captured the loose ends of the lines and tied a double looped figure 8 at the end of each rope and attached them to each other with reversed carabiners, taking up all the slack behind our holding man as possible. We then attached the tail of each rope to its opposite number's anchor point (photo 3). This would leave us enough tautness in the system so that there would be no great plunge going over the edge and enough slack in the system so that the two ropes will merge together as the load nears the bottom.