Quarter pound block of C-4, several feet of detonating cord (Primacord), one blasting cap, more than a few meters of wire, a detonating machine or batteries, and a bunch of filled sandbags (the more the merrier).

Wrap det cord around base of pipe, leaving a foot or so trailing out. Mold C-4 plastic explosive over det cord, splaying it out onto the concrete base. Tape or otherwise affix cap to det cord. Cover base det cord and C-4 with sandbags.

Move a ways away. Use the detonating machine (so-called "plunger") or connect the batteries. Wait for debris to stop falling, neighbors to stop complaining, golfers to clean their pants up, and cops to leave. Put debris out for trash pickup or turn into a yard ornament.

ALTERNATE:

Snakehole under the pipe and concrete, insert explosives in snakehole, touch it off, and launch the pipe assemblage into orbit -- or someone else's yard. In either case, no longer my problem. Fill in resulting hole in back yard, repair lawn sprinklers, etc.