Originally Posted by tadpole
What an interesting looking boulder!
And herein lies your problem. Because the surface of this boulder is SO irregular, it will be extremely difficult to make any liner attachment to the boulder Leak-Free.
It would be so much easier to lift the boulder, place the liner beneath it and reset the boulder more perpendicular to the ground. Another factor to consider is, if you are going to drill a hole(s) for piping, you will need the proper equipment or sub it out to a concrete contractor.
It would look great as a Water Feature, though.
Originally Posted by mxridernorth
Drill it. Insert epoxied anchors and call in a crane.
If you core drill it keep an eye out for fractures as you stated. Plus, if your able to lift it and put a liner under it pad that liner big time to keep the weight of the rock from puncturing it.
As for the size for the outlet pipe I would at least go to 1.5" to make it look right for that size of boulder.