If the breakout box cannot be made accessible, a special cable can be built to bring the signals out to a convenient location. All cable runs should be buried, even if only a few inches or with rocks piled on them. Exposed cable is degraded rapidly by UV rays and is chewed by rodents. The rodents seem to like only the insulation, nibbling it off along the cable without breaking many conductors. Unfortunately this leads to shorts, and a steady deterioration of signal quality.
Cables are expensive to replace as a routine.
If the construction includes tubing as a way of protecting the cable, include pull wires when the tubing is installed so that the cables can easily be drawn through the tubing when the equipment is ready to be installed. The target depth is between 80 and 180 cm. Use a rod to pound in and get an idea of the depth before digging. Weathered granite and shales often do not have an abrupt transition from loose to firm but must be chipped at until the layer is deemed firm enough. An iron bar is better than a pick axe for this.