The standard questions from this forum is "What are your goals for this pond?" Swimming, fishing, etc?
You will need to re-seal the pond, especially in light of some of the dry summers we have been having if you want your water level to stay consistent. There are things that can be done to excavate your drain pipe and replace it, but I am no expert. Read up on anti-seep collars, and make sure to choose materials that are made to last when you perform the work. Do it right and do it once, do it wrong...
Plenty of experts here to help!
If the pond really is 100 years old, you probably have more than 2-3 feet of muck.
BTW Welcome!
-Mark
