Here is another thought. In the US, and probably other countries as well, all buried non-metalic pipes must have a trace wire laid along with the pipe. The ends of that wire must be available so a detection system can trace exactly where the pipe is buried. There is nothing to restrict you to a single strand of wire. A multiple conductor could be used to power and control your system. It would have to be removed when the pipe tracing was being done.
In addition, since you will have no access to the equipment, you need to use what you learned in your classes about failure analysis and design in modes that allow your system to still function when pieces fail.
Paul