An improved method of operating a drilling system for purposes of installing an underground line and associated apparatus are disclosed. The drilling system includes a drill rig which is positionable at a drilling site and a drill string which is configured for extension by the drill rig such that the drill string is extendable to a predetermined location in a way which forms a pilot bore and which is further configured for retraction, such that one end of a line may be attached to the drill string at the predetermined location and pulled through the pilot bore from the predetermined location to the drill rig as the drill string is retracted. The improvement comprises monitoring tension levels in the line during retraction which tension levels are caused by the force of retraction on the line and transmitting the tension levels to an above ground location for use in establishing the condition of the line as it is installed underground. The associated apparatus includes means for monitoring tension levels in the line caused by the force of retraction on the line and means for transmitting the tension levels to the above ground location.