Just a FYI, I have two PVC seep collars on my 12" pipe. They were installed on the pipe correctly, but not packed in clay, and compacted correctly. There is a leak running along side the pipe when the water level exceeds the spot where the pipe comes out of the dam. The pipe is angled upwards fairly substantially. I think the water runs down the original trench dug to place the pipe.
I'm going to try the polymer approach to stop the seep. I'm hoping to avoid the draining and rebuilding..
I'd go with option #3 if I had a chance to do it all over again.
Or go with a siphon system.
Jeff

12 yr old pond, 1 ac, 15' deep.
RES, YP, GS, FHM (no longer), HBG (decreasing), SMB, and HSB (only two have been seen in 5 yrs)
I think that's about all I should put in my little pond.
Otter attack in 2023.